Fluorescent Probes for Intraoperative Navigation

Yunxue Xu; Renfu Liu; Kun xu; Zhifei Dai

doi:10.7536/PC201014

Progress in Chemistry ›› 2021, Vol. 33 ›› Issue (1) : 52-65 DOI: 10.7536/PC201014

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Fluorescent Probes for Intraoperative Navigation

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Abstract

Fluorescence imaging has a promising application prospect in clinical tumor tracing and intraoperative navigation, by virtue of its simple operation, high resolution, safety and real-time imaging. Though there are no targeted fluorescent probes clinically approved yet, a great number of targeted fluorescent probes are indeed under clinical trials. The very first ones are fluorescent dyes conjugated with tumor-targeting ligands, such as tumor-specific antibodies labeled with near-infrared(NIR) cyanine dye(IRDye800CW) and fluorescein isothiocyanate labeled with folic acid(EC17). In recent years, more complicated fluorescent probes, such as activatable probes and PET/fluorescent dual-modal imaging probes, have gradually entered clinical trials. Based on the latest research progress of fluorescent probes for intraoperative navigation, this review discusses receptor-mediated targeted fluorescent probes, activatable targeted fluorescent probes, NIR-Ⅱ fluorescent probes, multimodal fluorescent probes and theranostic fluorescent probes, with an emphasis on analyzing and summarizing the molecular design principles of fluorescent probes which are undergoing clinical evaluation or with the potential of clinical translation. At last, the future perspectives of fluorescent probes for intraoperative navigation are prospected.

Contents

1 Introduction

2 Receptor-mediated targeted fluorescent probe

3 Activatable targeted fluorescent probe

4 NIR-Ⅱfluorescent probe

5 Multimodal fluorescent probe

6 Theranostic fluorescent probe

7 Conclusion and outlook

Graphical abstract

Keywords

fluorescent intraoperative navigation / receptor-mediated targeted fluorescent probes / activatable targeted fluorescent probes / NIR-Ⅱ imaging / multimodal fluorescent probes / theranostic fluorescent probes / clinical translation

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Yunxue Xu, Renfu Liu, Kun xu, Zhifei Dai. Fluorescent Probes for Intraoperative Navigation. Progress in Chemistry, 2021, 33(1): 52-65 DOI:10.7536/PC201014

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1 Introduction

Cancer is one of the major causes of human death. Currently, the treatment of solid tumors is mainly based on surgery combined with radiotherapy and chemotherapy^[1]. The main purpose of tumor surgery is to completely remove the primary and metastatic tumors, while minimizing the damage to normal tissues. However, in the course of surgery, it is difficult to accurately identify the boundary of tumor tissue only by naked eye, palpation and experience, and the residual small lesions may lead to tumor recurrence and metastasis. Therefore, surgical treatment often needs to be combined with imaging AIDS. Among various imaging techniques, such as ultrasound imaging, computed tomography (CT), magnetic resonance imaging (MRI) and fluorescence imaging, fluorescence imaging has attracted much attention because of its convenient operation, high resolution, short imaging time and no radiation injury. It can display the tumor boundary in real time and mark the metastatic lesions and lymph nodes during the operation^[2,3].

Efficient fluorescent probes are necessary for the success of intraoperative fluorescence imaging. Currently, fluorescent probes approved for clinical use include 5-aminolevulinic acid (5-ALA), methylene blue, and indocyanine green (ICG)^{[4 ⇓~6]}. Among them, ICG is the most commonly used fluorescent probe in clinic. As a dye with emission wavelength in the near-infrared I region (700-900 nm), ICG has low non-specific background fluorescence signal and good tissue penetration, which can provide higher signal-to-noise ratio. At present, ICG has achieved good results in clinical sentinel lymph node identification and intraoperative navigation of some liver tumors^[7,8]. However, the stability of ICG is poor, its structure needs to be further optimized, and it is not targeted, so it can not be effectively enriched in most tumor tissues. Therefore, scientists have been working on the development of various new targeted fluorescent probes, and some of them have entered the clinical trial stage^{[9 ⇓ ⇓ ⇓ ⇓ ⇓ ⇓~16]}. The most common targeted fluorescent probes typically consist of a tumor target molecule and a fluorophore. However, such "normally bright" targeting probes continue to emit fluorescent signals whether or not they bind to the target tissue, and therefore have a greater probability of causing a higher background signal. In order to improve the signal to noise ratio, fluorescent probes that can be specifically activated at the lesion site have attracted increasing attention. On the other hand, NIR-Ⅱ (1000-1700 nm) imaging has the advantages of less tissue autofluorescence, higher imaging resolution and deeper penetration depth, which makes NIR-Ⅱ fluorescent probes show great potential for clinical transformation and broad application prospects^[17,18]. In addition, dual-mode/multi-mode fluorescent probes combined with other imaging modes and multi-functional fluorescent probes integrated with diagnosis and treatment have gradually become research hotspots in this field.

According to the progress and problems of fluorescent probes for surgical navigation in recent years, this paper discusses the receptor-mediated targeted fluorescent probes, activatable targeted fluorescent probes, near-infrared two-region fluorescent probes, multimodal fluorescent probes and diagnostic and therapeutic integrated fluorescent probes.The molecular design principles of fluorescent probes which are under clinical research and have the prospect of clinical transformation are analyzed and summarized in order to provide some new ideas for the research in related fields at home and abroad.

2 Receptor-mediated targeted fluorescent probe

Each tumor cell has a series of surface receptors that play an important role in tumor growth. Therefore, these overexpressed receptors could serve as targets for tumor-specific imaging^[19]. Receptor-mediated targeting fluorescent probes are usually composed of fluorophores and targeting ligands with high affinity for tumor receptors, including antibodies, polypeptides and small molecular compounds^{[20 ⇓ ⇓~23]}.

Since rituximab, a monoclonal antibody against CD20, was approved for clinical treatment of B-cell lymphoma, many other tumor-related antibodies have been approved for cancer treatment in recent years^[24]. These antibodies generally have abundant free amino or sulfhydryl groups on the surface, and the fluorescent dye is covalently coupled with the active free group of the antibody to obtain a tumor-targeted fluorescent probe for intraoperative fluorescent navigation of tumor resection^[25]. At present, several clinical trials have demonstrated the feasibility and safety of antibody coupled near-infrared cyanine dye IRDye800CW for tumor surgical navigation^[11,12,26]. IRDye800CW is a near-infrared fluorophore derived from ICG by structural optimization.Compared with ICG, IRDye800CW has better photostability and less intermolecular aggregation due to the introduction of a rigid cyclohexene ring connected by a phenoxy ether bridge into the polymethine chain of the cyanine dye^[27]. The carboxyl group on IRDye800CW was further modified with an N-hydroxysuccinimide (NHS) group to be able to covalently bind to the antibody reactive group (fig. 1A)^[28]. These structural features make IRDye800CW a versatile near-infrared fluorophore with good photostability, safety, and the ability to couple to a variety of target molecules.

Studies have shown that 95% of head and neck squamous cell carcinomas overexpress the tumor epidermal growth factor receptor (EGFR)^[29]. IRDye800CW-labeled panitumumab and cetuximab, which specifically bind to EGFR, are currently undergoing clinical evaluation for intraoperative navigation in head and neck cancer (NCT 01987375, NCT 02415881)^[26]. Bevacizumab is a humanized monoclonal antibody targeting the angiogenesis factor (VEGF-A), and IRDye800CW-labeled bevacizumab is currently in clinical trials for intraoperative fluoronavigation in breast and colorectal cancer (NCT01508572, NCT02583568, NCT01691391)^[30]^[11,12]. Since these antibodies have been approved for clinical use in tumor suppression, and their safety and effectiveness in targeting tumors have been confirmed, the targeted fluorescent probes developed based on these antibodies are more likely to be successful, which may be a relatively shorter, safer and more economical way to develop targeted fluorescent probes^[9]. But at the same time, antibody-based targeted fluorescent probes also have some shortcomings, for example, the molecular weight of antibodies is generally large (more than 100 kDa), which makes it difficult for fluorescent probes to penetrate into tumors uniformly, and may also lead to non-specific retention and uptake in sites with high vascular permeability such as inflammation (high permeability and retention effect, EPR effect).

Most malignant tumor cells have a strong ability to spread and metastasize. As a class of cell adhesion receptors, integrins are widely involved in tumor proliferation and metastasis. Among them, integrin αvβ3 is widely and highly expressed in tumor neovascularization, which is an important target for tumor diagnosis and treatment. Arginine-glycine-aspartic acid (RGD) polypeptide with αvβ3 as a target point is coupled with a fluorescent dye to construct a fluorescent navigation molecular probe in tumor surgery. For example, covalently binding a cyclic arginine-glycine-aspartic acid (cRGD) polypeptide to the near-infrared dye ZW800-1 (cRDG-ZW800-1) can be used for highly targeted imaging of tumors during surgery (fig. 1b). ZW800-1, a zwitterionic near-infrared fluorophore designed by Frangioni et al., has two distinct advantages: less nonspecific binding in vivo and rapid renal clearance^{[31 ⇓~33]}. The chemical structure and geometry of dyes play an important role in the nonspecific binding, cellular uptake, and metabolic clearance of near-infrared fluorophores in organisms. Similar to IRDye800CW, the backbone structure of ZW800-1 also includes a rigid cyclohexene moiety connected by a phenoxy ether bridge in the middle of the methine chain. However, the net charge on the surface of ZW800-1 is zero, which shields the hydrophobic heptamethine chain. This unique structure not only gives ZW800-1 comparable fluorescence properties to IRDye800CW, but also reduces its retention and non-specific binding in the liver. In a preclinical mouse melanoma model, the signal-to-noise ratio after intravenous administration of cRDG-ZW800-1 was as high as 17.2, compared with 5.1 and 2.7 for cRGD-IRDye800CW and cRGD-Cy5.5, respectively^[34]. The cRDG-ZW800-1 is currently in a Phase 2 clinical trial investigating the feasibility of fluorescent-guided surgery in patients with oral and head and neck cancer (NCT04191460).

Folate receptor α (FRα) is highly expressed in a variety of epithelial tumors, and FRα is highly expressed in 90% -95% of epithelial ovarian cancer cells, while its expression in normal cells is at a low level^[35]. In 2011, folate-conjugated fluorescein isothiocyanate-derived EC-17 probe (Fig. 1C) was first used for intraoperative tumor-specific fluorescence imaging in patients with ovarian cancer (NCT 02000778)^[36]. Intraoperative fluorescence detected 57 lesions in 12 patients injected with EC-17 at a dose of 0.1 mg/kg, 44 of which were confirmed pathologically to be FRα positive, and 7 of which had not previously been detected by gross inspection or palpation^[37,38]. These results indicate that EC-17, a fluorescent imaging probe targeting the FRα receptor, can be successfully used for intraoperative navigation of FRα-positive tumors. Because the emission wavelength of EC-17 is located at 500 nm, its limited imaging depth and high background autofluorescence make it impossible for EC-17 to successfully detect deep lesions, resulting in many tumor nodules being missed. Low et al. Optimized the fluorophore of EC-17 and obtained a near-infrared fluorescent probe OTL38 targeting FRα. Although the phenoxy ether bridge structure in cyanine dyes can increase their fluorescence intensity, the phenoxy ether bridge is easily attacked by amino groups when the target ligands are coupled with these cyanine dyes, resulting in by-products and increasing the difficulty of separation and purification. To solve this problem, Low et al. Replaced the glutamic acid moiety of folic acid with tyrosine, and coupled the phenolic hydroxyl group in the tyrosine side chain with the meta-chloride of fluorophore S0456 to obtain OTL38 (Fig. 1D). The yield and purity of OTL38 were more than 98%^[13,39]. At present, OTL38 has successfully completed Phase 1 and Phase 2 clinical trials in ovarian cancer and lung cancer (NCT02317705, NCT02872701). In patients with ovarian cancer, OTL38 was able to track malignant lesions with high sensitivity (mean signal-to-noise ratio 4.4). In a clinical trial, 62 of 83 metastatic ovarian cancer nodules detected by OTL38 were confirmed pathologically, and 18 (29%) of the confirmed nodules were not detectable by other traditional methods^[38].

With the development of nanotechnology, nanoscale targeted fluorescent probes, which have significant advantages in light stability, brightness and multi-functional usability, have begun to enter the stage of clinical trials. For example, ultra-small targeted fluorescent core-shell silica nanoparticles (C dots) with a particle size of 6 to 7 nm were developed by Weisner et al^[45]. The size of less than 10 nm not only allows it to be quickly metabolized and eliminated by the kidney in vivo, reducing potential toxic side effects, but also allows it to penetrate more evenly through tumor tissue^[46]. The C dots are composed of a silica core cross-linked with Cy5 and a shell surface-modified with short polyethylene glycol (PEG) chains (M_w~500)^[47]. Compared with free Cy5, Cy5 in C dots became a relatively rigid structure after crosslinking, which reduced non-radiative losses such as vibrational relaxation, and showed better photostability and fluorescence intensity (increased by more than 2 times)^[48]. In addition, a fluorescent/PET bimodal probe (¹²⁴I-cRGDY-PEG-C dots) targeting integrin was obtained by conjugating a cyclic arginine-glycine-aspartate-tyrosine (cRGDY) targeting peptide labeled with iodine -124(¹²⁴I) to a PEG chain (Fig. 1e, 1f)^[49]. The PET imaging of the first clinical trial confirmed that the ¹²⁴I-cRGDY-PEG-C dots was well tolerated and was mainly metabolized by the kidney in vivo, which proved to have good safety and biodistribution characteristics^[49]. In addition, C dots have been shown to accurately identify metastatic lymph nodes in preclinical melanoma models^[50]. Therefore, clinical trials are being conducted to evaluate the efficacy of C dots in intraoperative fluorescence imaging of metastatic lymph nodes.

Receptor-mediated tumor targeting probes are mostly composed of fluorophores covalently coupled to ligands with high affinity for tumors, and some of them need to introduce linker arms to increase the water solubility of the probes or reduce the steric resistance of the coupling reaction^[51,52]. By optimizing the structure of the connecting arm and the fluorophore, the pharmacokinetic characteristics of the probe in vivo can be further improved, and the specificity and sensitivity of tumor imaging can be improved^{[31 ⇓~33]}. Currently, affinity targeting probes in preclinical/clinical trials have some drawbacks, for example, their imaging specificity is limited by the expression level of tumor-specific receptors. Tumors are heterogeneous, and different patients with the same tumor (or even different regions of tumor tissue in the same patient) have different levels of specific receptor expression^{[53 ⇓~55]}. Therefore, preoperative biopsy of tumor tissue is needed to determine the expression level of specific receptors, which can guide whether to use affinity fluorescent probes to visualize tumors during operation. In addition, specific imaging of the probe at the tumor site can only be observed after the untargeted bound probe is cleared in vivo, which is limited by the diffusion rate of the probe and its clearance in vivo. Therefore, such fluorescent targeting probes are generally not suitable for rapid visualization of tumors.

3 Activatable target fluorescent probe

The targeting fluorescent probes based on affinity have a problem that can not be ignored, that is, regardless of the interaction with the target tissue, the fluorescent probes always emit fluorescent signals, so there is considerable interference of background fluorescent signals^[56]. Unlike these "normally bright" fluorescent probes, activatable fluorescent probes are generally quenched by themselves, they emit strong fluorescence only when stimulated by specific enzymes, pH values or redox potentials, or the state of resonance fluorescence energy transfer of the original probe itself changes under these stimuli, resulting in a change in the wavelength of fluorescence emission^{[57 ⇓~59]}. This kind of activatable probe is easier to obtain a higher signal-to-noise ratio of tumor/normal tissue, and further improves the specificity and sensitivity of tumor targeting imaging.

At present, most of the activatable fluorescent probes entering the clinical trial stage are enzyme activatable fluorescent probes. Enzyme-activatable probes fall into two main categories: enzyme-reactive probes and enzyme-substrate probes. The enzyme-reactive probe is covalently bound to the site of the reaction when the target region is activated, whereas the enzyme-substrate probe is activated by the enzyme and its fluorophore is released and not covalently coupled to the enzyme. cathepsins and matrix metalloproteinases (MMPs) are highly expressed in most tumor tissues, which are closely related to tumor invasion and metastasis. Many activatable probes in preclinical studies/ongoing clinical trials are designed based on these two enzymes. For example, Bender et al. designed a cathepsin reactive probe, BMV109 (fig. 2a)^[60,61]. BMV109 is composed of Cy5 fluorophore, Cbz-Phe-Lys polypeptide linker (cathepsin recognition site), 2,3,5,6-tetrafluorohydroquinone electrophilic group and quenching group. The fluorescence of Cy5 is quenched due to the presence of the quenching group. After cysteine cathepsin recognized the Cbz-Phe-Lys polypeptide, the 2,3,5,6-tetrafluorohydroquinone electrophilic group reacted with the cathepsin, the quenching group was released from BMV109, Cy5-Cbz-Phe-Lys was covalently linked to the enzyme, and the Cy5 fluorophore emitted fluorescence. In a preclinical mouse model of multiple intestinal tumors, signal-to-noise ratios of 9 and 2.6 were achieved for intravenous injection and topical spray of BMV109, respectively^[62]. However, because the enzyme-reactive probe will be covalently bound to the target enzyme after activation, the development of the target label will limit the continuous amplification of the fluorescence signal at the target site, which is not conducive to further improving the specificity and sensitivity of imaging.

Unlike enzyme reaction probes, the fluorophore is released after the enzyme substrate probe is activated and is not covalently coupled with the enzyme, so the fluorescence signal of the target position can be continuously amplified with the increase of time and probe concentration, and the imaging specificity is further improved. Urano et al. developed a series of activatable enzyme substrate fluorescent probes based on hydroxymethyl rhodamine green (HMRG) for intraoperative topical spray fluorescence navigation, such as gamma-glutamyl HRMG (gGlu-HMRG, trade name GCP-001) (fig. 2b)^{[63 ⇓~65]}. The fluorescence of GCP-001 is quenched due to intramolecular spiralization, but it can be rapidly activated by gamma-glutamyl transpeptidase (GGT) to restore fluorescence. GGT is overexpressed on the cell surface of a variety of tumors, including cervical and ovarian cancers^[66]. Once GCP-001 encounters GGT on the surface of cancer cells, it is hydrolyzed into HMRG with strong fluorescence, which guides the resection of tumor lesions^[63]. The feasibility of GCP-001 for intraoperative fluorescence imaging was evaluated using freshly resected human breast cancer samples, and the results showed that 5 minutes after topical application of GCP-001, breast cancer lesions and normal tissue could be distinguished by fluorescence signals^[67]. Currently, GCP-001 is undergoing clinical trials in Japan to evaluate its efficacy in the detection of breast cancer lesions by fluorescence.

In general, the free small molecule fluorophore released after the enzyme substrate probe is activated is easy to diffuse, which leads to the loss of fluorescence signal at the target site and shortens the time window of fluorescence imaging. In order to solve the problem of small molecule diffusion of fluorophores, Whitley et al. Introduced a long polyethylene glycol (PEG) fragment into the protease-activated fluorescent probe LUM015 to increase the overall molecular weight of the released fluorophores and prolong the imaging time. LUM015 is mainly composed of GGRK peptide, QSY21 quencher, Cy5 fluorophore and mPEG polymeric chain (Fig. 2 C)^[68]. The GGRK peptide is a specific substrate for cathepsin and maintains the proper spacing between the fluorophore and the quencher. The QSY21 quencher and the Cy5 fluorophore are covalently bound to the N-terminus of the polypeptide and the amino group of the lysine, respectively. In addition, the introduction of the PEG-fragment can significantly improve the solubility and pharmacokinetics of the probe. The intact LUM015 is in a state of fluorescence quenching, but once it is cleaved by cathepsin, the quencher is released and the Cy5 fluorescence is restored, and the PEG-fragment coupled to the Cy5 fluorophore can inhibit its rapid diffusion in tissues. A phase 1 clinical trial in 15 patients found that LUM015 was well tolerated and could be used to differentiate soft tissue sarcoma and breast cancer tissue from normal tissue in in vitro surgical specimens (NCT01626066)^[68]. In another clinical trial, LUM015 (injected at a dose of 0.5 mg/kg) was shown to identify intraoperative residual breast cancer lesions in real time with a mean signal-to-noise ratio of 4.70 (NCT03321929)^[69].

In addition to increasing the molecular mass of the fluorophore fragments (e.g., PEG-polychains) to inhibit the rapid diffusion of small molecule fluorescence, another strategy is to modify the fluorophore fragments of enzyme substrate probes so that the cleaved fluorescent fragments can be efficiently taken up by cells or localized to specific organelles. For example, Turk et al. modified a cathepsin substrate probe by covalently attaching a palmitoyl lipid chain to the fluorophore fragment, allowing the released fluorophore to fuse with the cell membrane, inhibiting the diffusion of the fluorescent signal (fig. 2D)^[70]. In the mouse 4 T1 breast cancer model, the fluorescence signal intensity of the probe modified by the palmitoyl lipid chain was twice as strong as that of the probe not modified by the lipid chain 24 H after injection, and the fluorescence signal of the lipidated probe could still be detected at the tumor site 8 days after injection. In addition, Ofori et al. designed a cathepsin substrate probe 6QCNIR to localize the fluorescence signal in the lysosome by taking advantage of the acidic environment of the lysosome (fig. 2e). Cathepsin recognizes and cleaves the target on 6 QCNIR, and the cleavage of the amide bond produces a fluorophore fragment containing a free amino group, which is protonated in an acidic environment to carry a positive charge and eventually localizes in the lysosome^[71]. The results showed that 6QCNIR could rapidly generate fluorescence signals in preclinical lung cancer, breast cancer and colon cancer models, and the signal intensity at the target site did not decay significantly after 24 H. Cell-penetrating peptide (CPP) is a kind of short peptide that can carry many active substances into cells. Tsien et al. designed the matrix metalloproteinase-activated Cy5/Cy7 ratio fluorescent probe AVB-620 based on the activatable cell penetrating peptide (ACPP)^[72]. When the linker arm of AVB-620 is cleaved by MMP2 or MMP9, which is highly expressed in human breast cancer cells, the hairpin structure is destroyed, and the cell-penetrating peptide carries Cy5 into the cell, while the Cy7 linked to the polyanion masking peptide cannot enter the cell, resulting in a significant increase in the Cy5/Cy7 fluorescence ratio^[73,74]. Compared with the traditional imaging based on absolute fluorescence intensity, this ratio imaging is less affected by imaging conditions (such as the distance between the camera and the tissue, the change of drug concentration). AVB-620 is currently in a Phase 2 clinical trial to evaluate the accuracy of tumor detection during breast cancer surgery (NCT03113825).

At present, the activatable fluorescent probes that have entered the stage of clinical trials are mainly enzyme-responsive probes.Some activatable probes responding to specific tumor microenvironments (such as hypoxia, low pH, high levels of reactive oxygen species and high concentrations of glutathione) have also achieved good results in clinical/preclinical studies, and have great prospects for clinical application. For example, Gao et al. designed a polymeric micelle fluorescent nanoprobe PINS that can respond to the acidic pH of tumors (transition pH = 6.9)^[16]. By adjusting the length of the polymer and the number of coupled ICG, the most sensitive structural PEG-b-P(EPA₁₀₀-r-ICG₁) to pH response was screened. At pH > 6. 9, the polymer self-assembled to form a stable micelle structure in the buffer solution, and ICG was located in the core of the micelle, resulting in fluorescence quenching. At pH < 6.9, the micelles dissociate into monomers and the ICG fluorescence is restored (fig. 3A). Therefore, the fluorescence signal is quenched when it is in blood (pH ˜ 7.4); However, in the acidic microenvironment of the tumor, the near-infrared fluorescence was restored. PINS has been shown to have broad tumor detection specificity in models of preclinical head and neck cancer, breast cancer, pancreatic cancer, and peritoneal metastases (Figure 3 B). ONM-100 (trade name of PINS) has been found to have a signal-to-noise ratio of up to 27 for tumor detection in a mouse orthotopic head and neck cancer tumor model, with an imaging time window of 12-24 H. In the first clinical trial, ONM-100 was well tolerated by all patients, with an average signal-to-noise ratio of 3.7 for tumor detection. The above results demonstrate the effectiveness and feasibility of ONM-100 for fluorescence navigation in clinical tumor surgery^[75]. Mo et al. designed glutathione (GSH) -responsive dicyanine dye conjugate probes (ss-diCy5 and ss-diNH800CW). ss-diCy5 is linked by two water-soluble Cy5 molecules through disulfide bonds, and ss-diNH800CW is coupled by two NH800CWs through disulfide bonds^[57]. The fluorescence of the dicyanine dye conjugate is quenched, and once the dicyanine dye conjugate is taken up by the tumor tissue, high concentration of GSH in the tumor cell reduces the disulfide bond of the probe, the conjugate is broken, and the fluorescence is restored. In the mouse breast cancer 4T1 tumor model, the two cyanine dye conjugates can restore the fluorescence signal at the tumor site and realize the specific imaging of the tumor.

4 Near-infrared two-region fluorescent probe

Compared with NIR-Ⅰ (700 ~ 900 nm) fluorescence imaging, NIR-Ⅱ (1000 ~ 1700 nm) light has weaker absorption, less scattering and deeper penetration depth in biological tissues. Moreover, the autofluorescence of the tissue is very weak in the NIR-Ⅱ band, and the background signal is very low, therefore, tumor fluorescence imaging navigation in the NIR-Ⅱ can significantly increase the imaging depth and improve the imaging signal-to-noise ratio, and has a very broad clinical application prospect^[17,18].

At present, the development of NIR-Ⅱ fluorescent probes mainly includes some inorganic nanomaterials and organic small molecule dyes. Among them, inorganic nanomaterials mainly include carbon nanotubes, rare earth doped nanomaterials and semiconductor quantum dots (QDs). Carbon nanotubes (CNTs) are the first NIR-Ⅱ fluorescent probes to be imaged in vivo in animals (mice).Compared with other types of probes, CNTs are very stable in fluorescence and have a high bleaching limit (10 H of excitation light exposure)^[76]. In order to further improve the imaging effect of carbon nanotubes and significantly increase their fluorescence emission wavelength, Shuo et al designed and synthesized a semiconducting single-walled carbon nanotube with greatly enhanced brightness and fluorescence emission wavelength of 1500 ~ 1700 nm. The system can realize capillary imaging below 3 mm depth and deeper tumor tracing development^[77]. The fluorescence emission wavelength of QDs in the second near-infrared region is closely related to its particle size, and within a certain wavelength range, the emission wavelength is positively correlated with its particle size. Ag₂S quantum dots (QDs) have been widely used in NIR-Ⅱ biomedical imaging research due to their high fluorescence stability and no toxic heavy metal ions. Li et al. Modified Ag₂S QDs with long-chain PEGs to improve its water solubility and increase its circulation time in vivo. The fluorescence imaging resolution of PEGylated Ag₂S QDs in mice was up to 40 μm, which could continuously observe the angiogenesis within the tumor and trace the small tumor lesions (diameter 2. 7 mm)^[78]. However, due to the small particle size of Ag₂S QDs, the coordination number of surface atoms is low, so the fluorescence quantum yield is low, which becomes a limitation of its application in NIR-Ⅱ imaging.

Compared with inorganic nanomaterials, organic small molecule NIR-Ⅱ fluorescent probes have clear chemical structure, good biocompatibility and rapid metabolism in vivo. Therefore, the development of NIR-Ⅱ probes based on small organic molecules is an ideal candidate for clinical application of NIR-Ⅱ fluorescence imaging. At present, there are mainly two types of such probes. The first type is small molecules based on the donor-acceptor-donor (D-A-D) structure, and benzobisthiadiazole (BBTD), as a strong electron-withdrawing group, is widely used to construct such probes. The other is cyanine dyes which have been structurally modified and optimized. The first small molecule NIR-II fluorescence probe of D-A-D type is CH1055 with BBTD as electron acceptor group and triphenylamine as electron donor group (Fig. 4A). Antaris et al. Modified CH1055 with a sulfonic acid group to obtain a water-soluble probe CH-4T. Based on the affinity between sulfonate and plasma protein, CH-4T was mixed with plasma protein to obtain a supramolecular complex with greatly enhanced fluorescence intensity, and its fluorescence quantum yield could reach 5%, which realized the rapid imaging of deep tumors in vivo^[79]. In addition, Zhou et al. Coupled the targeting polypeptide F3 targeting nucleolin on the surface of breast cancer cells (or breast cancer endothelial cells) with CH1055 to prepare the NIR-II fluorescent probe CH1055-F3 that can actively target breast cancer. The probe can specifically image transplanted and spontaneous breast cancer, and successfully guide the surgical resection of spontaneous breast cancer in mice^[80]. In order to improve the fluorescence quantum yield of D-A-D type small molecular probes in aqueous solution, Zhang et al. Used 3,4-ethylenedioxythiophene (EDOT) instead of triphenylamine as the donor group to prepare IR-E1. This EDOT structure effectively reduces the interaction between water molecules and the conjugated backbone, and its fluorescence quantum yield in aqueous solution can reach 0.7%^[81]. Later, Zhang et al. Further optimized the IR-E1 probe by introducing an electron shielding group (S) -alkyl chain substituted fluorene, which can further weaken the intermolecular interaction, thereby reducing the fluorescence quenching effect caused by intermolecular aggregation. The S-D-A-D-S probe was PEG-modified to obtain the water-soluble probe IR-FEP, which had a fluorescence quantum yield of 2% in aqueous solution and was successfully used for high signal-to-noise ratio imaging of mouse breast cancer (Fig. 4B, 4C)^[82].

ICG is the most commonly used cyanine dye for surgical navigation. In recent years, more and more attention has been paid to the preclinical/clinical studies of ICG in NIR-Ⅱ imaging. Starosolski et al. performed NIR-I and NIR-II fluorescence imaging of mouse hindlimb blood vessels using ICG, and the comparison results showed that ICG had higher signal-to-noise ratio and resolution in NIR-II^[83]. Hu et al. Constructed a visible/near-infrared one-zone/near-infrared two-zone multispectral imager, and used ICG as a fluorescence probe to achieve NIR-II fluorescence imaging guided liver cancer resection for the first time in clinic^[84]. In addition to ICG, a series of new NIR-II cyanine dyes have achieved good imaging results in preclinical studies. For example, the new NIR-II cyanine dye FD-1080 designed and synthesized by Li et al. Has a fluorescence emission peak at 1080 nm (Fig. 4D). FD-1080 was conjugated with fetal bovine serum (FBS) to form a complex with a fluorescence quantum yield of 5. 94%, which could be used to clearly monitor the different respiratory dynamics of mice under awake and anesthetized conditions^[85]. Ding et al. designed a fluorescent dye 5H5 with a very broad absorption peak in the near-infrared region, which can be excited by 808 nm and 1064 nm at the same time, and receive the fluorescence of NIR-Ⅱ (1000-1700 nm) and NIR-Ⅱa (1300-1400 nm) respectively. The results of tumor and blood vessel imaging in mice with the 5H5-based targeted nanoprobe showed that a higher signal-to-noise ratio (3 times the signal-to-noise ratio of the NIR-II band) could be obtained by using the NIR-IIa band for imaging (Fig. 4E)^[86].

5 Multimodal fluorescence imaging probe

Fluorescence imaging technology has the advantages of convenient operation, high resolution, fast imaging and no radiation damage, but the scattering of light in vivo and the shallow penetration depth of light tissue limit the application of fluorescence imaging technology in deep tumor tissue imaging. Although a series of near-infrared two-band fluorescence probes have been developed and the tissue penetration depth of fluorescence imaging has been improved, it is still unable to effectively develop tumor lesions with a depth of more than 5-8 mm^[87]. In addition to fluorescence imaging, the commonly used imaging techniques in clinical practice include ultrasound imaging, computed tomography (CT), positron emission tomography (PET) and single photon emission computed tomography (SPECT).Each imaging technique has its unique advantages and limitations, therefore, combining the advantages of a variety of imaging techniques to construct a dual-mode/multi-mode probe based on fluorescence probe has become one of the current trends of surgical navigation probe research.

Although no bimodal/multimodal fluorescence imaging probes have been clinically approved, some bimodal fluorescence probes are in clinical trials. The first bimodal fluorescent probe to enter clinical trials for tumor surgical navigation is the radionuclide ¹¹¹In and the near-infrared fluorescent dye IRDye800CW co-labeled with the ¹¹¹Indium-DOTA-girentuximab-IRDye800CW(NCT024975599) of gemtuzumab. Girentuximab is a monoclonal antibody that targets carbonic anhydrase IX, which is widely overexpressed in renal clear cell carcinoma^[88]. This fluorescence/PET dual-modality probe can determine the location of deep tumors through preoperative PET imaging, and display the boundaries of tumors through real-time fluorescence imaging during operation to guide tumor resection. Clinical trials have shown that preoperative PET imaging is essential for deep tumor localization, because the fat covering the tumor greatly weakens the fluorescence signal, and if the tumor is resected solely by intraoperative fluorescence signal navigation, it is easy to miss the covered deep lesions. In addition, bimodal imaging can also help exclude false-positive lesions with autofluorescence, such as cyst contents^[88]. Using a similar strategy, Li et al. Constructed a fluorescence/PET bimodal probe ⁶⁸Ga-BBN-IRDye800CW of ⁶⁸Ga and IRDye800CW co-labeled Bombesin peptide (targeting the gastrin-releasing peptide receptor) for preoperative/intraoperative navigation in glioblastoma (NCT02910804)^[106].

In addition to fluorescence/PET bimodal probes, multimodality probes based on fluorescence combined with other imaging techniques have also achieved good results in preclinical studies. For example, Liu et al. constructed BRET-FRET nanobubbles using Bioluminescence resonance energy transfer (BRET) and Fluorescence resonance energy transfer (FRET) technologies for Fluorescence/ultrasound dual-modality imaging of inflammatory tissues such as tumors (Fig. 5A). Myeloperoxidase in inflammatory areas reacts with substrate luminol to emit blue light, which is converted into near-infrared light by BRET-FRET nanobubbles, thus realizing highly sensitive fluorescence imaging of deep inflammatory tissues. This BRET-FRET nanobubble system was successfully used for fluorescence/ultrasound dual-modality imaging of breast cancer metastases (Fig. 5B)^[89]. Chen et al. Used superparamagnetic iron oxide nanoparticles (SPIO) loaded with near-infrared dye ICG, and modified the surface with PEG and RGD to obtain fluorescence/magnetic resonance bimodal probes^[90]. In a mouse model with both primary liver cancer and metastatic liver cancer, the probe detected (0.9 ± 0.5) mm foci by magnetic resonance imaging and (0.6 ± 0.3) mm micrometastases by fluorescence imaging. Using aggregation-induced luminescence (AIE) materials, Qi et al. constructed an AIE small molecule OPTA-TQ3 with near-infrared two-region fluorescence, photoacoustic and Raman signals (Fig. 5C). The fluorescence/photoacoustic/Raman trimodal nanoprobe based on OPTA-TQ3 can provide comprehensive tumor localization information through preoperative fluorescence and photoacoustic imaging, and delineate the tumor edge through intraoperative high-sensitivity fluorescence and Raman imaging, which has good application prospects in surgical navigation (Fig. 5d)^[91].

6 Diagnosis and treatment integrated fluorescent probe

When the fluorescent probe absorbs photons, it can emit fluorescence and release heat or singlet oxygen at the same time, so that it can carry out photothermal (PTT) or photodynamic (PDT) therapy (phototherapy) on tumors^[92,93]. At present, 5-ALA, an integrated fluorescent probe for diagnosis and treatment, has been approved for photodynamic therapy of tumors as a second-generation photosensitizer, in addition to being used for surgical navigation of malignant gliomas. In addition, the use of near-infrared dye ICG for photothermal therapy of tumors has also achieved good preclinical results^{[94 ⇓ ⇓~97]}. With the development of nanotechnology, fluorescent nanoprobes can be loaded with therapeutic drugs or other contrast agents at the same time, which is expected to achieve the integration of multi-modal diagnosis and treatment of tumors. In a word, the development of integrated diagnostic and therapeutic fluorescent probes for image-guided treatment of malignant tumors has gradually become a research hotspot in the field of molecular imaging.

Small molecule fluorescent probe is an integrated reagent for cancer diagnosis and treatment with great potential for clinical transformation, which can integrate targeted delivery, in vivo tracking, cancer treatment and other functions through covalent coupling strategy. For example, Meng et al. constructed RhoSSCy, an integrated probe for diagnosis and treatment, which responds to acidic pH and high concentration of GSH in tumor microenvironment, by connecting a specific structure of heptamethine cyanine dye (Cy7) and rhodamine fluorophore through disulfide bonds^[98]. The probe is a ratiometric fluorescent probe, has a photoacoustic signal, and can generate singlet oxygen to kill tumor cells by virtue of the photosensitive characteristics of rhodamine and Cy7 cyanine dye. The experimental results demonstrate that RhoSSCy can achieve fluorescence/photoacoustic dual-modality imaging-guided photodynamic therapy in a mouse breast cancer model. Zeng et al. Developed a water-soluble sulfonated near-infrared two-domain small molecule probe H2a-4T, which can be mixed with tumor antibody drug Cetuximab (targeting EGFR) to obtain a stable H2a-4T @ Cetuximab complex.The compound has good tumor targeting imaging effect on colon cancer tumor-bearing mice, has high photothermal conversion efficiency, and realizes the photothermal therapy of tumors guided by near-infrared two-region fluorescence imaging^[99].

It is difficult to achieve a very ideal tumor treatment effect by a single phototherapy method, and the development of a new nano-system for fluorescence imaging-guided tumor combination therapy can achieve better therapeutic effect^[100]. PDT can trigger the body's anti-tumor immune response, but the body's adaptive immune resistance will weaken this immune response, resulting in immune tolerance. Inhibition of indoleamine 2,3-dioxygenase 1 (IDO-1) activity has been shown to overcome adaptive immune resistance and enhance anti-tumor immune response^[101,102]. Based on this, Gao et al combined the prodrug of IDO-1 inhibitor with PEGylated photosensitizer PPa, and designed a vesicle system that released the prodrug in response to the tumor microenvironment (high concentration of GSH and MMP-2) (Fig. 6)^[103]. MMP-2 cleaves PEGylated photosensitizer PPa, which is specifically enriched in tumor tissues to achieve fluorescence imaging-guided photodynamic therapy. GSH reduces the disulfide bond on the connecting arm of the prodrug of the IDO-1 inhibitor, so that the IDO-1 inhibitor is released at a tumor site, and the anti-tumor immune response of PDT is enhanced. This fluorescence imaging-guided tumor photodynamic/immunotherapy combination therapy significantly inhibited tumor recurrence in a mouse colorectal cancer tumor model.

7 Conclusions and outlook

In recent years, with the rapid development of intraoperative fluorescence imaging navigation technology, with the development of new fluorescence probes, doctors can more accurately distinguish the tumor boundary, identify residual tumor lesions, and completely resect the lesion location. These techniques revolutionize cancer surgery by maximizing the efficiency of tumor resection and improving patient survival. At present, the clinical transformation of IRDye800CW, OTL38 and other probes has achieved initial results^[9,13,104]. Other fluorescent probes, including specific enzyme-activated fluorescent probes and PET/fluorescent bimodal probes, have also entered the stage of clinical trials^{[16,49,68,73]}. In addition, due to the lower photon scattering, absorption and tissue autofluorescence, the tissue penetration depth, imaging resolution and signal-to-noise ratio of near-infrared region II fluorescence imaging are significantly improved compared with near-infrared region I imaging^[105]. The first clinical trial of NIR-II tumor fluorescence imaging showed that the signal to noise ratio (SNR) of ICG in NIR-II was significantly higher than that in NIR-I (5.33: 1.45)^[84]. Therefore, although most of the fluorescent probes currently in clinical trials are used for near-infrared region I imaging, it can be expected that more and more near-infrared region II imaging probes will enter clinical trials in the near future. In addition, with the continuous development of molecular design theory and nanotechnology, more novel multi-modal and multi-functional fluorescent probes with integrated diagnosis and treatment will be designed and developed, showing great potential for clinical transformation. Because the clinical translation of a new fluorescent probe faces many challenges, it is of great significance to learn from the design concept and translation experience of existing probes.

References

Publishing order | Descend order by publishing year | Descend order by cited within

[1]	Arruebo M, Vilaboa N, Saez-Gutierrez B, Lambea J, Tres A, Valladares M, Gonzalez-Fernandez A. Cancers(Basel), 2011, 3: 3279.

[2]	Bu L, Shen B, Cheng Z. Advanced Drug Delivery Reviews , 2014, 76: 21.

[3]	Hameed S, Chen H, Irfan M, Bajwa S Z, Khan W S, Baig S M, Dai Z. Bioconjug Chem., 2019, 30: 13.

[4]	Namikawa T, Yatabe T, Inoue K, Shuin T, Hanazaki K. World J. Gastroenterol. , 2015, 21: 8769.

[5]	Van Manen L, Handgraaf H J M, Diana M, Dijkstra J, Ishizawa T, Vahrmeijer A L, Mieog J S D. J. Surg. Oncol., 2018, 118: 283.

[6]	Matsui A, Tanaka E, Choi H S, Kianzad V, Gioux S, Lomnes S J, Frangioni J V. Surgery , 2010, 148: 78.

[7]	Alander J T, Kaartinen I, Laakso A, Patila T, Spillmann T, Tuchin V V, Venermo M, Valisuo P. Int. J. Biomed. Imaging , 2012, 2012: 940585.

[8]	Yamamichi T, Oue T, Yonekura T, Owari M, Nakahata K, Umeda S, Nara K, Ueno T, Uehara S, Usui N. J. Pediatr. Surg. , 2015, 50: 833.

[9]	Gao R W, Teraphongphom N, De Boer E, Van Den Berg N S, Divi V, Kaplan M J, Oberhelman N J, Hong S S, Capes E, Colevas A D, Warram J M, Rosenthal E L. Theranostics , 2018, 8: 2488.

[10]	Miller S E, Tummers W S, Teraphongphom N, Van Den Berg N S, Hasan A, Ertsey R D, Nagpal S, Recht L D, Plowey E D, Vogel H, Harsh G R, Grant G A, Li G H, Rosenthal E L. J. Neurooncol. , 2018, 139: 135.

[11]

Lamberts L E, Koch M, De Jong J S, Adams A L L, Glatz J, Kranendonk M E G, Terwisscha Van Scheltinga A G T, Jansen L, De Vries J, Lub-De Hooge M N, Schroder C P, Jorritsma-Smit A, Linssen M D, De Boer E, Van Der Vegt B, Nagengast W B, Elias S G, Oliveira S, Witkamp A J, Mali W, Van Der Wall E, Van Diest P J, De Vries E G E, Ntziachristos V, Van Dam G M. Clin. Cancer Res., 2017, 23: 2730.

[12]	Ter Weele E J, Terwisscha Van Scheltinga A G, Linssen M D, Nagengast W B, Lindner I, Jorritsma-Smit A, De Vries E G, Kosterink J G, Lub-De Hooge M N. Eur. J. Pharm. Biopharm., 2016, 104: 226.

[13]	Mahalingam S M, Kularatne S A, Myers C H, Gagare P, Norshi M, Liu X, Singhal S, Low P S. J. Med. Chem., 2018, 61: 9637.

[14]

Burggraaf J, Kamerling I M, Gordon P B, Schrier L, De Kam M L, Kales A J, Bendiksen R, Indrevoll B, Bjerke R M, Moestue S A, Yazdanfar S, Langers A M, Swaerd-Nordmo M, Torheim G, Warren M V, Morreau H, Voorneveld P W, Buckle T, Van Leeuwen F W, Odegardstuen L I, Dalsgaard G T, Healey A, Hardwick J C. Nat. Med., 2015, 21: 955.

[15]	Zhou J, Joshi B P, Duan X, Pant A, Qiu Z, Kuick R, Owens S R, Wang T D. Clin. Transl. Gastroenterol. , 2015, 6: e101.

[16]	Zhao T, Huang G, Li Y, Yang S, Ramezani S, Lin Z, Wang Y, Ma X, Zeng Z, Luo M, De Boer E, Xie X J, Thibodeaux J, Brekken R A, Sun X, Sumer B D, Gao J. Nat. Biomed. Eng. , 2016, 1: 0006.

[17]	He S, Song J, Qu J, Cheng Z. Chemical Society Reviews , 2018, 47: 4258.

[18]	Ding F, Zhan Y, Lu X, Sun Y. Chemical Science , 2018, 9: 4370.

[19]	Mankoff D A, Link J M, Linden H M, Sundararajan L, Krohn K A. J. Nucl. Med. , 2008, 49 Suppl 2: 149S

[20]

Boogerd L S F, Hoogstins C E S, Schaap D P, Kusters M, Handgraaf H J M, Van Der Valk M J M, Hilling D E, Holman F A, Peeters K, Mieog J S D, Van De Velde C J H, Farina-Sarasqueta A, Van Lijnschoten I, Framery B, Pelegrin A, Gutowski M, Nienhuijs S W, De Hingh I, Nieuwenhuijzen G a P, Rutten H J T, Cailler F, Burggraaf J, Vahrmeijer A L. Lancet Gastroenterol. Hepatol. , 2018, 3: 181.

[21]	Sturm M B, Joshi B P, Lu S, Piraka C, Khondee S, Elmunzer B J, Kwon R S, Beer D G, Appelman H D, Turgeon D K, Wang T D. Sci. Transl. Med. , 2013, 5: 184ra61.

[22]	Kleinjan G H, Buckle T, Van Willigen D M, Van Oosterom M N, Spa S J, Kloosterboer H E, Van Leeuwen F W. Molecules , 2014, 19: 9876.

[23]	Crouch B T, Gallagher J, Wang R, Duer J, Hall A, Soo M S, Hughes P, Haystead T, Ramanujam N. Sci. Rep. , 2019, 9: 3461.

[24]	Vacchelli E, Aranda F, Eggermont A, Galon J, Sautès-Fridman C, Zitvogel L, Kroemer G, Galluzzi L. Oncoimmunology , 2014, 3: e27048.

[25]	Korb M L, Hartman Y E, Kovar J, Zinn K R, Bland K I, Rosenthal E L. J. Surg. Res. , 2014, 188: 119.

[26]	Linssen M D, Ter Weele E J, Allersma D P, Lub-De Hooge M N, Van Dam G M, Jorritsma-Smit A, Nagengast W B. J. Nucl. Med. , 2019, 60: 418.

[27]	Kurutos A, Ryzhova O, Trusova V, Gorbenko G, Gadjev N, Deligeorgiev T. J. Fluoresc. , 2016, 26: 177.

[28]	Cheung L. Fluorescent Imaging with Substituted Cyanine Dyes . US 9248203 B 2. 2016.

[29]	Grandis J R, Tweardy D J. Cancer Research , 1993, 53: 3579.

[30]	Kazazi-Hyseni F, Beijnen J H, Schellens J H. Oncologist , 2010, 15: 819.

[31]	Choi H S, Nasr K, Alyabyev S, Feith D, Lee J H, Kim S H, Ashitate Y, Hyun H, Patonay G, Strekowski L, Henary M, Frangioni J V. Angew. Chem. Int. Ed. Engl. , 2011, 50: 6258.

[32]	Hyun H, Bordo M W, Nasr K, Feith D, Lee J H, Kim S H, Ashitate Y, Moffitt L A, Rosenberg M, Henary M, Choi H S, Frangioni J V. Contrast Media Mol I , 2012, 7: 516.

[33]	De Valk K S, Handgraaf H J, Deken M M, Mulder B G S, Valentijn A R, Van Scheltinga A G T, Kuil J, Van Esdonk M J, Vuijk J, Bevers R F, Peeters K C, Holman F A, Frangioni J V, Burggraaf J, Vahrmeijer A L. Nature Communications , 2019, 10: 3118.

[34]	Choi H S, Gibbs S L, Lee J H, Kim S H, Ashitate Y, Liu F, Hyun H, Park G, Xie Y, Bae S, Henary M, Frangioni J V. Nat. Biotechnol. , 2013, 31: 148.

[35]	Pieroth R, Paver S, Day S, Lammersfeld C. Curr. Nutr. Rep. , 2018, 7: 70.

[36]	Van Dam G M, Themelis G, Crane L M A, Harlaar N J, Pleijhuis R G, Kelder W, Sarantopoulos A, De Jong J S, Arts H J G, Van Der Zee A G J, Bart J, Low P S, Ntziachristos V. Nat. Med., 2011, 17: 1315.

[37]	Tummers Q R J G, Hoogstins C E S, Gaarenstroom K N, De Kroon C D, Van Poelgeest M I E, Vuyk J, Bosse T, Smit V T H B M, Van De Velde C J H, Cohen A F, Low P S, Burggraaf J, Vahrmeijer A L. Oncotarget , 2016, 7: 32144.

[38]	Hoogstins C E, Tummers Q R, Gaarenstroom K N, De Kroon C D, Trimbos J B, Bosse T, Smit V T, Vuyk J, Van De Velde C J, Cohen A F, Low P S, Burggraaf J, Vahrmeijer A L. Clin. Cancer Res. , 2016, 22: 2929.

[39]	Hoogstins C E S, Tummers Q R J G, Gaarenstroom K N, De Kroon C D, Trimbos J B M Z, Bosse T, Smit V T H B M, Vuyk J, Van De Velde C J H, Cohen A F, Low P S, Burggraaf J, Vahrmeijer A L. Clinical Cancer Research , 2016, 22: 2929.

[40]	Liu Y, Bauer A Q, Akers W J, Sudlow G, Liang K, Shen D, Berezin M Y, Culver J P, Achilefu S. Surgery , 2011, 149: 689.

[41]	Franklin H L, Miller D M, Hedges T, Perry J, Parrish-Novak J. Proc. Spie , 2016, 9696.

[42]	Baik F M, Hansen S, Knoblaugh S E, Sahetya D, Mitchell R M, Xu C, Olson J M, Parrish-Novak J, Mendez E. Jama Otolaryngol. , 2016, 142: 330.

[43]	Parrish-Novak J, Byrnes-Blake K, Lalayeva N, Burleson S, Fidel J, Gilmore R, Gayheart-Walsten P, Bricker G A, Crumb W J, Tarlo K S, Hansen S, Wiss V, Malta E, Dernell W S, Olson J M, Miller D M. Int. J. Toxicol., 2017, 36: 104.

[44]	Mohammadi A M, Ormond D R, Bodman A B, Olson J J. Neurosurgery , 2019, 85: E648.

[45]	Bradbury M S, Phillips E, Montero P H, Cheal S M, Stambuk H, Durack J C, Sofocleous C T, Meester R J, Wiesner U, Patel S. Integr. Biol.(Camb), 2013, 5: 74.

[46]	Longmire M, Choyke P L, Kobayashi H. Nanomedicine(Lond), 2008, 3: 703.

[47]	Burns A A, Vider J, Ow H, Herz E, Penate-Medina O, Baumgart M, Larson S M, Wiesner U, Bradbury M. Nano Lett. , 2009, 9: 442.

[48]	Larson D R, Ow H, Vishwasrao H D, Heikal A A, Wiesner U, Webb W W. Chemistry of Materials , 2008, 20: 2677.

[49]	Phillips E, Penate-Medina O, Zanzonico P B, Carvajal R D, Mohan P, Ye Y, Humm J, Gonen M, Kalaigian H, Schoder H, Strauss H W, Larson S M, Wiesner U, Bradbury M S. Sci. Transl. Med. , 2014, 6: 260ra149.

[50]	Benezra M, Penate-Medina O, Zanzonico P B, Schaer D, Ow H, Burns A, Destanchina E, Longo V, Herz E, Iyer S, Wolchok J, Larson S M, Wiesner U, Bradbury M S. J. Clin. Invest., 2011, 121: 2768.

[51]	Huang S S, Wang X, Zhang Y, Doke A, Difilippo F P, Heston W D W. The Prostate , 2014, 74: 702.

[52]	Wang X, Huang S S, Heston W D W, Guo H, Wang B, Basilion J P. Molecular Cancer Therapeutics , 2014, 13: 2595.

[53]	Denison T A, Bae Y H. Journal of Controlled Release , 2012, 164: 187.

[54]	Heppner G H, Miller B E. Cancer Metastasis Rev. , 1983, 2: 5.

[55]

Gerlinger M, Rowan A J, Horswell S, Larkin J, Endesfelder D, Gronroos E, Martinez P, Matthews N, Stewart A, Tarpey P, Varela I, Phillimore B, Begum S, McDonald N Q, Butler A, Jones D, Raine K, Latimer C, Santos C R, Nohadani M, Eklund A C, Spencer-Dene B, Clark G, Pickering L, Stamp G, Gore M, Szallasi Z, Downward J, Futreal P A, Swanton C. New England Journal of Medicine , 2012, 366: 883.

[56]	Chen C, Tian R, Zeng Y, Chu C, Liu G. Bioconjug. Chem. , 2020, 31: 276.

[57]	Mo S, Zhang X, Hameed S, Zhou Y, Dai Z. Theranostics , 2020, 10: 2130.

[58]	Wang C, Wang Z, Zhao T, Li Y, Huang G, Sumer B D, Gao J. Biomaterials , 2018, 157: 62.

[59]	Mochida A, Ogata F, Nagaya T, Choyke P L, Kobayashi H. Bioorg. Med. Chem., 2018, 26: 925.

[60]	Verdoes M, Bender K O, Segal E, Der Linden W a V, Syed S, Withana N P, Sanman L E, Bogyo M. J. Am. Chem. Soc. , 2013, 135: 14726.

[61]	Bender K O, Ofori L O, Der Linden W a V, Mock E D, Datta G K, Chowdhury S, Li H, Segal E, Lopez M S, Ellman J A. J. Am. Chem. Soc. , 2015, 137: 4771.

[62]	Segal E, Prestwood T R, Der Linden W a V, Carmi Y, Bhattacharya N, Withana N P, Verdoes M, Habtezion A, Engleman E G, Bogyo M. Chemistry & Biology , 2015, 22: 148.

[63]	Urano Y, Sakabe M, Kosaka N, Ogawa M, Mitsunaga M, Asanuma D, Kamiya M, Young M R, Nagano T, Choyke P L, Kobayashi H. Sci. Transl. Med. , 2011, 3: 110ra119.

[64]	Slooter M D, Handgraaf H J M, Boonstra M C, Van Der Velden L A, Bhairosingh S S, Que I, De Haan L M, Keereweer S, Van Driel P, Chan A, Kobayashi H, Vahrmeijer A L, Lowik C. Oral Oncol. , 2018, 78: 1.

[65]	Sato C, Abe S, Saito Y, So Tsuruki E, Takamaru H, Makazu M, Sato Y, Sasaki H, Tanaka H, Ikezawa N, Yamada M, Sakamoto T, Nakajima T, Matsuda T, Kushima R, Kamiya M, Maeda S, Urano Y. Digestion , 2015, 91: 70.

[66]	Fentiman I S. Br. J. Cancer , 2012, 106: 1467.

[67]

Ueo H, Shinden Y, Tobo T, Gamachi A, Udo M, Komatsu H, Nambara S, Saito T, Ueda M, Hirata H, Sakimura S, Takano Y, Uchi R, Kurashige J, Akiyoshi S, Iguchi T, Eguchi H, Sugimachi K, Kubota Y, Kai Y, Shibuta K, Kijima Y, Yoshinaka H, Natsugoe S, Mori M, Maehara Y, Sakabe M, Kamiya M, Kakareka J W, Pohida T J, Choyke P L, Kobayashi H, Ueo H, Urano Y, Mimori K. Sci. Rep. , 2015, 5: 12080.

[68]

Whitley M J, Cardona D M, Lazarides A L, Spasojevic I, Ferrer J M, Cahill J, Lee C L, Snuderl M, Blazer D G, 3rd, Hwang E S, Greenup R A, Mosca P J, Mito J K, Cuneo K C, Larrier N A, O’reilly E K, Riedel R F, Eward W C, Strasfeld D B, Fukumura D, Jain R K, Lee W D, Griffith L G, Bawendi M G, Kirsch D G, Brigman B E. Sci. Transl. Med. , 2016, 8: 320ra4.

[69]	Smith B L, Gadd M A, Lanahan C R, Rai U, Tang R, Rice-Stitt T, Merrill A L, Strasfeld D B, Ferrer J M, Brachtel E F, Specht M C. Breast Cancer Res. Treat. , 2018, 171: 413.

[70]	Hu H, Vats D, Vizovisek M, Kramer L, Germanier C, Wendt K U, Rudin M, Turk B, Plettenburg O, Schultz C. Angewandte Chemie , 2014, 53: 7669.

[71]	Ofori L O, Withana N P, Prestwood T R, Verdoes M, Brady J J, Winslow M M, Sorger J M, Bogyo M. ACS Chemical Biology , 2015, 10: 1977.

[72]	Jiang T, Olson E S, Nguyen Q T, Roy M, Jennings P A, Tsien R Y. Proc. Natl. Acad. Sci. U. S. A. , 2004, 101: 17867.

[73]	Miampamba M, Liu J, Harootunian A, Gale A J, Baird S, Chen S L, Nguyen Q T, Tsien R Y, Gonzalez J E. Theranostics , 2017, 7: 3369.

[74]	Unkart J T, Chen S L, Wapnir I L, Gonzalez J E, Harootunian A, Wallace A M. Ann. Surg. Oncol. , 2017, 24: 3167.

[75]	Witjes M, Voskuil F, Steinkamp P, Koller M, Van Der Vegt B, Doff J, Zhao T, Hartung J, Jayalakshmi Y, Sumer B. Journal of Oral and Maxillofacial Surgery , 2019, 77: e38.

[76]	Welsher K, Liu Z, Sherlock S, Robinson J T, Chen Z, Daranciang D, Dai H. Nature Nanotechnology , 2009, 4: 773.

[77]	Diao S, Blackburn J L, Hong G, Antaris A L, Chang J, Wu J Z, Zhang B, Cheng K, Kuo C J, Dai H. Angewandte Chemie , 2015, 54: 14758.

[78]	Li C, Zhang Y, Wang M, Zhang Y, Chen G, Li L, Wu D, Wang Q. Biomaterials , 2014, 35: 393.

[79]	Antaris A L, Chen H, Diao S, Ma Z, Zhang Z, Zhu S, Wang J, Lozano A X, Fan Q, Chew L, Zhu M, Cheng K, Hong X, Dai H, Cheng Z. Nature Communications , 2017, 8: 15269.

[80]	Zhou H, Li S, Zeng X, Zhang M, Hong X. Chinese Chemical Letters , 2020, 31: 1382.

[81]	Zhang X D, Wang H, Antaris A L, Li L, Diao S, Ma R, Nguyen A, Hong G, Ma Z, Wang J, Zhu S, Castellano J M, Wyss-Coray T, Liang Y, Luo J, Dai H. Advanced Materials , 2016, 28: 6872.

[82]	Yang Q, Ma Z, Wang H, Zhou B, Zhu S, Zhong Y, Wang J, Wan H, Antaris A, Ma R, Zhang X, Yang J, Zhang X, Sun H, Liu W, Liang Y, Dai H. Advanced Materials , 2017, 29: 1605497.

[83]	Starosolski Z, Bhavane R, Ghaghada K B, Vasudevan S A, Kaay A, Annapragada A. PLoS ONE , 2017, 12: e0187563.

[84]	Hu Z, Fang C, Li B, Zhang Z, Cao C, Cai M, Su S, Sun X, Shi X, Li C, Zhou T, Zhang Y, Chi C, He P, Xia X, Chen Y, Gambhir S S, Cheng Z, Tian J. Nature Biomedical Engineering , 2020, 4: 259.

[85]	Li B, Lu L, Zhao M, Lei Z, Zhang F. Angewandte Chemie International Edition , 2018, 57: 7483.

[86]	Ding B, Xiao Y, Zhou H, Zhang X, Qu C, Xu F, Deng Z, Cheng Z, Hong X. Journal of Medicinal Chemistry , 2019, 62: 2049.

[87]	Vahrmeijer A L, Hutteman M, Van Der Vorst J R, Van De Velde C J H, Frangioni J V. Nat. Rev. Clin. Oncol. , 2013, 10: 507.

[88]	Hekman M, Rijpkema M, Muselaers C H J, Oosterwijk E, Hulsbergen-Van de Kaa C A, Boerman O C, Oyen W J G, Langenhuijsen J F, Mulders P F A. Theranostics , 2018, 8: 2161.

[89]	Liu R, Tang J, Xu Y, Dai Z. ACS Nano , 2019, 13: 5124.

[90]	Chen Q, Shang W, Zeng C, Wang K, Liang X, Chi C, Liang X, Yang J, Fang C, Tian J. Oncotarget , 2017, 8: 32741.

[91]	Qi J, Li J, Liu R, Li Q, Zhang H, Lam J W Y, Kwok R T K, Liu D, Ding D, Tang B Z. Chem , 2019, 5: 2657.

[92]	Li X, Lovell J F, Yoon J, Chen X. Nat. Rev. Clin. Oncol. , 2020, 17: 657.

[93]	Xu Y, Liang X, Bhattarai P, Sun Y, Zhou Y, Wang S, Chen W, Ge H, Wang J, Cui L, Dai Z. Advanced Functional Materials , 2017, 27: 1704096.

[94]	Hung C C, Huang W C, Lin Y W, Yu T W, Chen H H, Lin S C, Chiang W H, Chiu H C. Theranostics , 2016, 6: 302.

[95]	Liu R, Tang J, Xu Y, Zhou Y, Dai Z. Nanotheranostics , 2017, 1: 430.

[96]	Lin L, Liang X, Xu Y, Yang Y, Li X, Dai Z. Bioconjugate Chemistry , 2017, 28: 2410.

[97]	Yan L, Qiu L. Nanomedicine(Lond), 2015, 10: 361.

[98]	Meng X, Yang Y, Zhou L, Zhang L, Lv Y, Li S, Wu Y, Zheng M, Li W, Gao G. Theranostics , 2017, 7: 1781.

[99]	Zeng X, Xiao Y, Lin J, Li S, Zhou H, Nong J, Xu G, Wang H, Xu F, Wu J. Advanced Healthcare Materials , 2018, 7: 1800589.

[100]

He C, Chan C, Weichselbaum R R, Fleming G F, Yamada S D, Lin W. EBioMedicine , 2015, 2: 366.

[101]

Liu D, Chen B, Mo Y, Wang Z, Qi T, Zhang Q, Wang Y. Nano Letters , 2019, 19: 6964.

[102]

Lu J, Liu X, Liao Y, Wang X, Ahmed A, Jiang W, Ji Y, Meng H, Nel A E. ACS Nano , 2018, 12: 11041.

[103]

Gao A, Chen B, Gao J, Zhou F, Saeed M, Hou B, Li Y, Yu H. Nano Letters , 2020, 20: 353.

[104]

Tummers Q R, Hoogstins C E, Gaarenstroom K N, De Kroon C D, Van Poelgeest M I, Vuyk J, Bosse T, Smit V T, Van De Velde C J, Cohen A F, Low P S, Burggraaf J, Vahrmeijer A L. Oncotarget , 2016, 7: 32144.

[105]

Hong G S, Antaris A L, Dai H J. Nature Biomedical Engineering , 2017, 1: 0010.

[106]

Li D, Zhang J, Chi C, Xiao X, Wang J, Lang L, Ali I, Niu G, Zhang L, Tian J, Ji N, Zhu Z, Chen X. Theranostics , 2018, 8: 2508.

Funding

the Beijing Natural Science Foundation & Haidian Original Innovation Joint Fund(17L20170)

the National Key Research and Development Program of China(No. 2016YFA0201400) , the State Key Program of National Natural Science of China(81930047)

the National Project for Research and Development of Major Scientific Instruments(81727803)

and the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(81421004)

the Projects of International Cooperation and Exchanges NSFC-PSF(31961143003)

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1 Introduction

2 Receptor-mediated targeted fluorescent probe

3 Activatable target fluorescent probe

4 Near-infrared two-region fluorescent probe

5 Multimodal fluorescence imaging probe

6 Diagnosis and treatment integrated fluorescent probe

7 Conclusions and outlook

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