# Novel Chitosan Derivatives and Their Multifaceted Biological Applications
## 4 Future Perspectives  
The journey of chitosan began from marine shell waste, has meandered from chitin to chitosan and is now diverging into multiple modifications to result in novel ChDs. As observed from the ocean of applications of these chitosan derivatives, much has been accomplished. The wisdom behind modifying chitosan to obtain derivatives that break the limitations of native chitosan is an attractive research direction. As has been described, there have been ample accomplishments in terms of antimicrobial activity, antioxidant activity and biocompatibility. However, this review does envision scope for further expansion.  
With as many as close to a hundred chitosan derivatives synthesized and tested for selective biological properties, it is strange that only a few biomedical applications have been seldom tested. As has been reviewed, very few novel chitosan derivatives have been applied to cancer therapy as compared to the voluminous reports with native chitosan. Chitosan is already well accomplished for cancer treatment [135; 136; 137; 138; 139; 140] and, with the ChDs showing much advanced features compared to native chitosan, more positive outcomes are expected through implementing novel ChDs. This review urges the practical implementation of the novel ChDs for anticancer research, phototherapy, bioimaging and diagnostics. There are definitely huge possibilities and prospects in this direction that need research focus.  
The most worked on biological property, where ChDs have been elaborately worked on, is their antimicrobial properties. Yet here too there exists an evident bias. Antibacterial and antifungal applications have been researched with respect to numerous novel abundant ChDs. However, it was observed that selective novel ChDs were applied to specific strains of bacteria and fungi. As can be observed from Table 1, the strains tested were more or less repetitive. Moreover, almost nothing regarding antiviral applications has been attempted. Being in the COVID era, seeing what these viruses are capable of, it is strange that a system so well understood for its antimicrobial activity, will not be put to test for its antiviral activity. This strong bias (there being more antibacterial reports) towards the implementation of novel ChDs within microbial applications was observed. This review stresses the need for more focus towards implementing the synthesized novel ChDs for diverse antibacterial (especially clinical isolates) and antiviral testing. Additionally, biomedical applications, such as antibacterial coatings, wound dressing, drug delivery and pharmaceutical options, have not been attempted with novel ChDs.  
Chitosan nanoparticles have their own unique properties, combining chitosan derivatives with chitosan nanomaterials will be a whole new avenue of possibilities, which is yet to be explored. As always, nanomaterials have always exceeded the abilities and limits of their bulk counterparts; chemical modification of chitosan nanoparticles and chitosan nanofibers could unleash numerous possibilities and satisfy extended biological functions. This could be the future of novel ChDs.