Preparation Of Alginate Nanofiber Mats And Evaluation Of Their Properties As Wound Dressings

Chronic wounds such as bedsore ulcers,leg ulcers and burns,can't be repaired orderly due to the complicated situation of the disease source.Alginate dressings have been widely used in chronic wound care because they can absorb a lot of exudates.However,the traditional alginate dressings were prepared by wet spinning.The alginate microfiber mats have large pores between the fibers,which restricted their performance.In this paper,in order to improve the properties of alginate dressing,alginate nanofiber mats with ultrafine pores were prepared by electrospinning.The specific research contents and results are as follows:In the first part,alginate nanofiber mats were prepared through electrospinning and crosslinked with two strategies.One is calcium ions crosslinking strategy.The other is the Schiff-base reaction crosslinking strategy recently developed by our group.The wound dressing related properties of the electrospun nanofiber mats were compared with the clinically used alginate dressings?Kaltostat and Algisite M?.The results show that the absorption capacity of the alginate microfibers in Kaltostat and Algisite M is only 2.1 and 2.7 g/g.The absorption capacity of calcium ions crosslinked alginate nanofibers(SA-Ca²⁺)is stronger,which is 5.4 g/g.The ultimate tensile strength of Kaltostat and Algisite M is only 0.28 and 0.40 MPa,respectively.The ultimate tensile strength of SA-Ca²⁺nanofiber mat is 0.94 MPa,which is twice as much as the former.Their permeability is around 0.30 g/?cm²·24h?.By comparison,the absorption capacity of the Schiff-base reaction crosslinked alginate nanofibers?OSA-ADH?can be up to 27.4 g/g.The ultimate tensile strength of OSA-ADH mats can be as high as 1.7 MPa.Their permeability is 0.20 0.25 g/?cm²·24 h?,which is within the recommended range.OSA-ADH nanofibers are degradable and not toxic to L929 fibroblasts.Therefore,OSA-ADH nanofiber mats are more promising wound dressings.In the second part,we studied the effects of pH value of crosslinking solution and the length of alkyl chain of the crosslinkers on the properties of the Schiff-base reaction crosslinked alginate nanofiber mats.The results of the first section show that the absorption capacity of the fibers crosslinked at pH 3 is 3.1 g/g,which is higher than that of the fibers crosslinked at pH 7.The surface contact angle of pH 3 mat is 35.8 °,slightly higher than that of pH 7 crosslinked mat,and both of them were completely infiltrated within 0.5 s.There is no significant difference in the surface wettability.Under acid condition,the reaction efficiency can be increased dramatically,and the complete degradation time of sodium alginate nanofibers is extended from 10 days to more than 21 days.In the second section,alginate nanofibers were crosslinked by using oxalyl dihydrazide?ODH?,malonic acid dihydrazide?MDH?,adipic dihydrazide?ADH?and dodecanedioic dihydrazide?DDH?,which contain 0,1,4 and 10 methylene groups,respectively.The absorption capacity of the crosslinked fibers is 3.0,2.1,3.0 and 5.1 g/g,respectively.The contact angle of the fiber mats crosslinked by the dihydrazides with shorter alkyl chains?ODH,MDH,ADH?are less than 35.8°.The contact angle of the fiber mats crosslinked with dihydrazide with long alkyl chains?DDH?is amazing,which is 137.6 °,which is obvious hydrophobic.The extension of alkyl chains significantly improved the water resistance of crosslinked alginate nanofibers.The residual mass of the fibers cultured for three weeks were 0% to 56%,66% and 99%,respectively.In summary,the electrospun OSA-ADH nanofiber mats were successfully prepared in this paper.Compared with the alginate microfiber mats and SA-Ca²⁺nanofiber mats,the OSA-ADH nanofiber mats exhibit excellent comprehensive performances,and are promising wound dressings.Furthermore,by adjusting the pH of the crosslinking solution and the alkyl chain length of the crosslinking agent,the performance of the mats can be tuned.This work is of high significance for the development of novel high-performance alginate wound dressings.