Study On The Preparation And Environmental Impact Of New Wound Dressing-gelatin-based Antibacterial Nanofiber Hydrogels

Wound dressing is a kind of disposable medical articles which becomes hazardous medical waste after usage.The wound dressing waste must be concentrated and treated.The wound dressing wastes which have not been treated effectively can cause intersectional infection and environmental pollution.The huge amount of hazardous wound dressing waste leads to a burden to the treatment departments and environmental protection in China.Now the treatment ratio of wound dressing waste is low and the incinerating disposal method always leads to the secondary pollution.Many countries have focused on the quantity-reducing method of hazardous medical waste.So it is urgent to develop new high-efficient wound dressing products to decrease the using quantity and discharged waste quantity by improving healing effect.In this article,we attempted to prepare new antibacterial wound dressing product by electrospinning,which can provide reference for the application of nanofibers and developing new type of wound dressing.By focusing on eco-environmental material,the degradable natural polymer gelatin and chitosan were chosen as the main raw material to prepare nanofiber hydrogel containing silver nanoparticles by electrospiinning.The as-spun nanofibers can be used to prepare antimicrobial wound dressing product to improve healing effects and reduce dressing-change times.So the new type of wound dressing can reduce the amount of hazardous waste.The influence of electrospinning process conditions to the morphology of the nanofibers and silver nanoparticles was investigated and the proper electrospining conditions were obtained.The crosslinking and swelling of nanofiber hydrogel were studied.The nanofibers can release silver ions and show strong antibacterial activity to Staphylococcus aureas and Pseudomonas aeruginosa.The main results obtained are as following.A new kind of gelatin nanofibers containing silver was prepared by electrospinning technique. The average diameter of gelatin/Ag nanofibers is 91～145 nm,and the average size of silver nanoparticles is 9～20 nm.The influence of gelatin concentration and the amount of AgNO₃ added to the spinnability of solution and the influence of electrospinning conditions such as electrospinning voltage and collection distance to the morphology of nanofibers was investigated. It was found that there is a critical amount value of added AgNO₃ during electrospinning.The behaviors were investigated in details with electrospinning theory.When the content of AgNO₃ attained 8%,the conductivity increasing ratio decreased which caused the change of electrical potential energy of spinning jet.So the jet instability occurs earlier.The morphology of nanofibers and silver nanoparticles was studied also.It was found that silver nanoparticles present quasi-sphere shaped and distributed homogenously on the surface of nanofibers after ultra-violet irradiation.The average diameter of silver nanoparticles did not change after irradiated for three hours.The average diameter values of silver nanoparticles estimated by Scherrer equation are similar to the results measured with transmission electron microscopy.The formation mechanism of silver nanoparticles was discussed and the photo-reduction reaction equation of silver ions was proposed.The new type of gelatin/chtosan nanofibers containing silver nanolparticels was prepared by adding chitosan into gelatin-AgNO₃ spinning solution.The average diameter of gelatin/chitosan/Ag nanofibers is 101～167 nm and the average size of silver nanoparticles is 8～17 nm.The average diameter of nanofibers and the critical amount value of AgNO₃ increased with adding chitosan into gelatin/AgNO₃ solution.The phenomenon was related with the increasing ratio of conductivity of spinning solution caused by adding chitosan.It is found that the average diameter of silver nanoparticles did not change after irradiated for four hours.By fixing the amount of AgNO₃ added,the average diameter of silver nanoparticles decrease and the quantity increase,compared with gelatin/Ag nanofibers.The nanofibers were cosslinked with saturated glutaraldehyde vapor to prepare nanofiber hydrogels.The crosslinked nanofibrous film's tensile strength and Young's modulus can attain 12.06 MPa and 437.8 MPa,respectively.The nanofiber can swell in phosphate buffer solution to form hydrogel and the swelling equillium can be attained during 10～15 min.The swelling degree can attain 5 g/g.The dissolution ratio and welling kinetics of nanofibrous films was studied.The influence of crosslinking time to the mechanical strength and swelling properties of nanofibber was distinct.The scanning electron microscopy photographs of nanofibers showed that the nanofibers can keep fibrous shape after immerged in phosphate buffer solution for 24 h.The release of silver ions of gelatin/Ag nanofiber and gelatin/chitosan/Ag was investigated.It was shown that controlled release of silver ions can be attained.The antibacterial tests against Staphylococcus aureas and Pseudomonas aeruginosa showed the inhibition ratios were more than 99%when 1.0 wt%AgNO₃ was added into spinning solution during electrospinning process.The nanofiber wound dressing can not only absorb a large amount of wound liquid to create a moist environment but also release silver ions to provide sustained antibacterial activity to avoid infection.The new wound dressing can improve wound healing effect remarkably.So the two kinds of nanofibrous films can be used as ideal wound dressing materials.The environmental impact of the new type of wound dressing made from gelatin-based nanofiber hydrogel was analyzed.Through environmental impact and economical analysis, compared with the traditional gauze wound dressing,the new wound dressing can reduce the usage amount of wound dressing and decrease consuming of resource and energy,and alleviate the treatment burden of hazardous medical waste and pollution to the environment.So this type of product is economical and highly valuable in both wound care and environmental protection.