6.6　Challenges and Perspectives

The clinical translation of nano-drug is the final goal of the research on nano-drug，which is also a major difficulty in the research on nano-drug.Currently，most of the FDAapproved nano-drug carriers for clinical application are liposome formulation.Currently，there are 19 liposome formulations that have been approved for the treatment of various diseases，including eight drugs for cancer treatment.Many polymer-based drug delivery systems are promising for clinical transformation.For example，PTX-loaded PEG-b-PLA micelles（Genexol-PM）have been approved for the treatment of breast cancer，and nanospheres of albumin-PTX-conjugates（abraxane）have been approved for the treatment of pancreatic and ovarian cancer.Currently，no polymer-based nano-drug carriers have been approved for the treatment of melanoma or psoriasis，but some polymer-based nano-drug delivery systems for melanoma have entered the clinical trial stage，such as the albumin-PTX-conjugated nano-drug delivery system.

The clinical translation of polymer nano-drug carriers is a complex question，which involves the change of pharmacokinetic of drug loaded in nano-drug carriers，the enhanced tumor accumulation of drug and therapeutic effect，the degradation and metabolism，potential toxic and side effects of the carrier materials，and its standardized production capacity.To improve the clinical translation potential of polymer nano-drug carriers，degradable and metabolic materials should be used as much as possible in the design of the carriers.In addition，besides introducing imaging and therapeutic functions to the nanomaterials，we should focus on investing the principles of interaction between nanomaterials and biological systems.At the same time，the currently used animal models cannot completely simulate the characteristics of human melanoma or psoriasis，and how to build a more realistic animal model to verify the therapeutic effect of nano-drug is also a problem that needs to be solved.The development of nano-drug is an interdisciplinary research direction，which requires the joint efforts of experts from all disciplines and fields to promote its clinical translation process.(https://www.daowen.com)

Compared with the skin disease treatment，polymer nano-drug carriers for cosmetic dermatology were developed much faster（see chapter 9）.More and more cosmetic dermatology products containing polymer nano-drug carriers have been developed and entered the market.