2.4　Challenges and Perspectives

The incidence of skin wound is high.Improper and delay treatment could cause the wound bleeding，infection，refractory healing and pathological scar formation，affecting the patients'quality of life.At present，the pathogeneses of skin wound and its complications have not been fully elucidated，and need to be further explored.With the development of polymer materials，intelligent-response hydrogel，antibacterial hydrogel and microneedles have achieved satisfactory therapeutic effects in the experimental animal model of skin wound.

Polymer materials can be used alone，or be combined with conventional therapy in treating skin wound.Antimicrobial hydrogel，a new type of skin wound dressings，has antibacterial property and can keep wound moisture，which could shorten inflammation phase of wound healing process.With the further research of antibacterial materials，the kinds of antibacterial hydrogel will enlarge.Moreover，the molecular mechanism of antibacterial hydrogel in promoting skin wound healing and the selection of antibacterial hydrogel in different stages of skin wound healing need to be further improved in the future.Available microneedle technology in clinical practice include roller microneedle and radio-frequency microneedle，which can be used alone or in combination with radiotherapy，laser and external drugs.The advantages of microneedle in treating skin scar are hypodynia，convenient，safe and efficient.Studies on the mechanism of microneedles in treating skin scars need to be strengthened.

In more severe forms of psoriasis，a combination of treatment modalities may be employed.In treating patients with methotrexate（MTX），for example，concomitant topical agents may be used to minimize the dose.Methotrexate has been combined with infliximab to reduce the incidence of neutralizing antibodies，and has been used with acitretin in managing patients with severe and generalized pustular psoriasis.Combination systemic therapy has the potential to reduce overall toxicity if the toxicities of each agent are different.However，new regimens should be used with caution because the potential for cumulative toxicity or drug interaction exists.With the development of scientific progress，the transdermal drug delivery technology is becoming more and more perfect，using a micrometer-sized needle-like structure to penetrate the epidermis painlessly，and form a reversible skin microchannel to convert methotrexate.Drugs such as MTX，acitretin，or biological agents are successfully delivered to the lesions through the stratum corneum，and then delivered on time according to different stimulus response functions，which reduces the gastrointestinal discomfort（nausea，vomiting，diarrhea，abdominal pain，etc.），stomatitis，bone marrow suppression，liver and kidney toxicity and other adverse reactions caused by traditional administration，but also reduces the pain and bleeding caused by the syringe.Therefore，changing the traditional drug delivery route will provide patients with a safer and easier treatment experience in the future.(https://www.daowen.com)

In the past decade，due to the development of immunotherapy and targeted therapy，the clinical efficacy of melanoma has been improved significantly，but not all patients can benefit from the existing treatment methods，and further optimization requires an in-depth understanding of tumor immunobiology mechanisms.Therefore，extensive pre-clinical，translational，and clinical studies are needed to better understand the response to current therapies and drug resistance mechanisms，develop rational next-generation therapies and combination therapies，and establish more complex and effective melanoma models to support further pre-clinical and clinical translation studies.Currently，surgical treatment is the gold standard for non-melanoma skin cancers.However，surgical treatment has great limitations，not all patients can undergo surgery，and surgical treatment has problems such as great trauma，affecting tissue function and aesthetics.The commonly used non-surgical treatment such as topical therapy and photodynamic therapy，although the trauma is small，but there are problems of poor drug penetration and narrow treatment range，which can only effectively treat primary and superficial tumors.The combination of biochemical technology and traditional treatment may bring new directions for the treatment of skin tumors，such as the use of microneedle and transdermal drug delivery technology to promote the penetration of local drugs and photosensitizers and improve the efficacy of topical therapy and photodynamic therapy；design nano-targeted drugs to precisely target cancer tissues，so as to reduce the side effects of systemic treatment.