Preparation, Characterization And Application As Wound Dressing Of Silver Nanoparticles-Pectin Composite Nanofibers

Chronic wounds are easy to recur,difficult to heal,and can lead to amputation or even death.Ideal wound dressing speeds wound healing by preventing infection and restoring skin structure and function.Silver nanoparticles(AgNPs)have broad spectrum antimicrobial properties and do not produce drug resistance.Electrospun polymer nanofibers have large specific surface area and small pore size,high porosity and other characteristics.AgNPs-electrospun polymeric nanofiber composites may be excellent wound dressing.At present,the commonly used methods for preparing AgNPs-electrospun polymeric nanofiber composites include dispersion electrospinning and post-reduction.The further treatment of electrospun fibers prepared by dispersion electrospinning may affect the properties of AgNPs.The steric hindrance of the nanofibers used in the post-reduction method results in that the deposition of AgNPs occurs only on the surface of the fibers.In this thesis,hydrophilic crosslinked pectin nanofibers were immersed in silver nitrate aqueous solution,swelled,allowing Ag~+enter into the fibers.The surrounding crosslinked pectin macromolecules acted as reductants,leading to the nucleation of AgNPs in situ and the formation of composite nanofibers with AgNPs homogeneously dispersed on fibers The properties of the composite nanofibers as wound dressings were then studied.The specific work is as follows:In the first part,AgNPs-pectin composite nanofibers were prepared,and the properties of the composite fibers and the effects of preparation conditions on them were studied.The results showed that the hydroxyl in pectin macromolecules and heat together reduced Ag~+,forming the face-centered cubic crystalline AgNPs on the crosslinked pectin nanofibers.The dispersion of AgNPs had no effect on the morphology and size of crosslinked pectin nanofibers,butmight make their surface rough.AgNPs distributed homogeneously in length and diameter of the fibers.At the silver nitrate concentration of 0.1 mol/L,as the incubation time extended from 3 h to 24 h,the size of AgNPs increased from 3.7 nm to 8.6 nm,and their content increased from 31.8%to 47.0%.The increase of silver nitrate concentration also caused an increase in the size and content of AgNPs.This method of preparation may be suitable for the homogeneous deposition of AgNPs on other hydrophilic polymeric nanofibers.In the second part,the properties of composite nanofiber mats related to wound dressing applications were studied.Their long-term antibacterial activity was emphatically studied.The composite nanofiber mats had a Young’s modulus of 2.3~7.2 MPa.They could permeat air at a rate of 0.32~0.40 g/(cm~2/24 h),which was between the normal human skin and the exposed wound,and thus could eliminate the excess water vapor on the surface of wounds.They could absorb simulated wound exudates equal to 16.3~32.2 times of their own weight,showing good ability to deal with wound exudates.The silver in the composite nanofibers incubated in 0.001 mol/L silver nitrate solution was uniformly released with a similar amount.In comparison,the amount of silver released from the composite nanofibers incubated in 0.1mol/L silver nitrate was relatively larger.For the composite nanofibers incubated for 3 h,the silver was uniformly released.For the composite nanofibers incubated for 8 h and 24 h,the release rate slowed down at later stage due to the larger size of the AgNPs.The total released amount of silver from the 24 h sample was even lower than that of 8 h sample.The inhibition zones of the composite nanofiber mats incubated with low silver nitrate concentration decreased with time,and those of the composite nanofiber mats incubated with high silver nitrate concentration were basically unchanged.The composite nanofiber mats with high AgNPs content show better long-term antibacterial ability,and are better wound dressings.In summary,AgNPs-pectin composite nanofibers with AgNPs uniformly distributed on fibers were successfully prepared.The composite nanofibers have excellent long-term antibacterial activity and are promising for wound dressing application.This work provides new ideas for the preparation of nanofibers with homogeneously dispersed AgNPs,and has implications for the development of high-performance wound dressings.