Preparation And Properties Of Hydrogel/Nanofibrous Membrane Bilayered Composite Dressing

Skin wound treatment is one of the most prevalent challenges in current clinical medicine.It is still a challenge to develop wound dressings which can promote wound healing and are comfortable.A variety of wound dressings has been developed to provide positive intervention for wound healing.Hydrogel has emerged as one of the most promising dressings for wound healing owing to the creation of moist environment.However,it suffers from poor water retention capability and weak mechanical property in practical applications.Therefore,development of hydrogel dressings with durable water retention and enhanced mechanical property is urgently needed.To solve these problems,we developed a bilayered hydrogel/nanofibrous membrane composite dressing consisting of upper layer of hydrophobic nanofibrous membrane and lower layer of double-crosslinked chitosan-based hydrogel with enhanced water retention and mechanical property.The main research results are summarized as following:1.With the aim to develop nanofibrous membrane with hydrophobicity,the nanofibrous membrane composed of polydimethylsiloxane（PDMS）embedded polyurethane（PU）were prepared by electrospinning.The FTIR spectra indicated the successful doping of PDMS.From the SEM images,it was found that the PU/PDMS33%membrane was more uniform with thinner fiber diameter of about 402 nm.With increasing PDMS content,the fibers became uneven and beads and droplets formed.The contact angle of the nanofibrous membrane increased with the addition of PDMS,indicating the improved hydrophobicity.Moreover,the nanofibrous membrane with 33%PDMS content exhibited good air permeability of 12.7 mm s^-1.2.To improve the water retention capability and mechanical property,the bilayered hydrogel/nanofibrous membrane composite（MOC/NF）was prepared by combining PU/PDMS33%nanofibrous membrane with methacryloyl chitosan（MC）/oxidized chitosan（OC）precursor solution.The radical polymerization of MC under UV irradiation occurred,and Schiff base bonds between MC and OC formed.The effects of hydrophobic nanofibrous membrane and various MC/OC mass ratios on the water retention capability of hydrogel composites were studied.It was found that the water retention of MOC（5-5）/NF composites was 51.3%after 7 days at room temperature,which was about 2.3 times than that of hydrogels.These results indicated the synergistic effect of the hydrophobic protection of PU/PDMS33%nanofibrous membrane and the dense crosslinking structure of hydrogel on water retention capability of the hydrogel composites.In addition,the MOC（5-5）hydrogel exhibited higher tissue adhesion with adhesive strength of 19.8 k Pa and fast self-healing ability.In addition,the MOC（5-5）/NF hydrogel composites presented good tensile property with tensile strength of 136.4 k Pa,compressive capability with compressive strength of 398.1 k Pa and cyclic compression stability.3.To demonstrate the application potential of the composite as a wound dressing,the in vitro cytocompatibility and in vivo rat wound healing activity of hydrogel composites were evaluated.It was found that the cell viability of hydrogel composites reached above 95%,suggesting the good cytocompatibility.In addition,the hydrogel composites could effectively promote the wound closure and skin regeneration in a full-thickness skin defect of rat model.An almost completely closure on the 14^th day post-surgery was achieved for the MOC（5-5）/NF hydrogel composites,indicating their promising potential as an ideal wound dressing.In summary,we developed a hydrogel/nanofibrous membrane composite dressing composed of breathable and hydrophobic nanofibrous membrane and double-crosslinked chitosan-based hydrogel.The hydrogel composites exhibited better water retention,stretchability,tissue adhesion,self-healing,as well as promoted wound healing performance in rat model.