Asymmetric nanomaterials (Janus nanomaterials) comprising at least two components of different chemistry, functionality, and/or polarity have attracted great scientific interest in a wide range of applications. Additional properties are attributed to the asymmetric spatial distribution of functionalities on a single anisotropic nanoparticle, like amphiphilicity or new catalytic characteristic. In addition, Janus nanomaterials' synergistic potential for multilevel targeting, and combination therapies make them particularly attractive for biomedical applications including biosensing, targeting delivery and bio-detection. In this paper, the advances in properties and applications of Janus nanomaterials are summarized. First, some properties and applications of Janus nanomaterials are described in three different aspects: amphipathicity, catalytic characteristic and biocompatibility. Second, the main biomedical applications are highlighted, which include biosensing, targeting delivery, gene vaccine and antimicrobial. Finally, the further development in preparation of Janus nanomaterials and their applications in food safety are expected.

Contents
1 Introduction
2 Properties of Janus particles
2.1 Amphipathy
2.2 Catalytic characteristic
2.3 Biocompatibility
3 Construction and applications of bioprobes based on Janus particles
3.1 Biological sensing
3.2 Targeting delivery
3.3 Gene vaccine
3.4 Antibacterial agents
4 Outlook