Effect of Chitosan Coating on the Properties of Poly(glycolic acid-lactic acid)Thread-Embedding Material

Poly( glycolic acid-lactic acid)( PGLA) threadembedding material was modified by chitosan coating which could improve the rigidity,hydrophilicity and moisture absorption of the material,and produced better stimulation effect. Thus,this kind of thread-embedding materials which can be buried into acupuncture points to produce a long-time stimulation is popular in the acupuncture and moxibustion therapies. The variation tendencies of diameter,weight, hydrophilicity, and flexibility of the samples under the change of chitosan coating concentration,coating time and coating times were studied respectively. The results showed that the hydrophilicity,weight,and rigidity after coating rose in a certain range with the increase of coating time,coating times and coating concentration. The coating time had little influence on the diameter of fiber.

Effect of Chitosan Coating on Properties of Polyactic Acid Thread-Embedding Material

Thread-embedding materials buried into acupuncture points to produce a long-time stimulation is a method which has been widely applied in the acupuncture and moxibustion therapies for diseases treating and they should have excellent properties of good biocompatibility,biodegradability and moderate rigidity.Polyactic acid(PLA) as the thread-embedding material had some shortcomings such as poor hydrophilicity and slowly biodegradable speed.In this paper,PLA thread-embedding material was modified by chitosan coating which could improve rigidity,hydrophilicity and moisture absorption and thus produce better stimulation effect.The variation tendency of diameter,mass,hydrophilicity,and initial modulus of the sample under the change of chitosan coating concentration,coating time and coating times were studied respectively.The results showed that the hydrophilicity,mass,and initial modulus after coating rose in a certain range when the coating time,coating times and coating concentration increased,while the changing of coating had little impact on fiber diameter.

Development and assessment of a multifunctional chitosan-based coating applied on AZ31 magnesium alloy: Corrosion resistance and antibacterial performance against Klebsiella Pneumoniae

This work presents a simple method to functionalise the surface of AZ31 magnesium alloy by applying a duplex MgF_(2)/chitosan coating,which improves its corrosion resistance and provides it with some antibacterial performance.First,the effect of three chitosan solutions with different concentrations on the growth of the bacteria Klebsiella pneumoniae in nutritive medium(TSB)was evaluated by absorbance kinetics experiments,where the chitosan solution at 2%(m/V)was selected for the coating preparation.Before coating application,the AZ31 substrate was pretreated with hydrofluoric acid for 48 hours in order to form a MgF_(2)conversion layer.Subsequently,the coating was applied to the pretreated substrate through the dry-casting method.Samples of the alloy in each surface condition(bare,pretreated,and pretreated+coated with chitosan)were exposed to simulated body fluid(SBF)for 21 days at 37°C,with the solution renewed every 24 hours and the wastes stored.The surfaces were characterised by SEM-EDS,and XPS after the immersion tests,whereas the stored solutions were employed to measure the change in the Mg-ions concentration.Electrochemical impedance spectroscopy and potentiodynamic polarisation were performed in each surface condition to compare their corrosion resistance in SBF.The antibacterial activity of the functionalised surfaces was evaluated by the plate counting method and compared with bare samples.All results were correlated and demonstrate that the modified surface of AZ31 achieved a higher corrosion resistance when it was exposed to SBF,as well as a reduction of the bacterial growth during in vitro tests.

Antibacterial Sutures Coated with Smooth Chitosan Layer by Gradient Deposition

Owing to the significant importance in clinics,antibacterial activity is thought as one indispensable feature of the next generation of absorbable sutures.It is challenging but imperative to arm the existing absorbable sutures with antibacterial functions.The present study describes a“gradient deposition”technique to coat a continuous and smooth layer of chitosan on the surface of absorbable sutures.Specifically,chitosan solution is arranged to undergo gradient pH decline step by step while during each pH interval,the solution is allowed to stand for a predetermined period of time in order to control gradual chitosan deposition.Chitosan nanoparticles are found to be first generated on suture surface and finally developed into a smooth chitosan layer as the antibacterial surface.In vitro and in vivo results demonstrated that coating chitosan on sutures by our technique could relieve wound inflammation,stimulate collagen deposition,regenerate blood vessels,and assist tissue repairing,consequently leading to a significant enhancement of wound healing effect.This technique is highlighted with low cost,extreme convenience and excellent safety without organic solvents.Furthermore,the“gradient deposition”technique would not affect the fundamental properties of matrix and thus hold promises as a universal way for superficial antibacterial modification towards almost all the surgical implanted materials,including but not limited to absorbable sutures.

Recyclable magnetite-silver heterodimer nanocomposites with durable antibacterial performance

There is a significant need for magnetite-silver nanocomposites that exhibit durable and recyclable antimicrobial activity.In this study,magnetic iron oxide nanoparticles(Fe3O4 NPs)coated with ethylenediamine-modified chitosan/polyacrylic acid copolymeric layer(Fe3O4@ECS/PAA)were fabricated.Subsequently,directly deposited silver(Ag)NPs procedure was carried out to form the antibacterial heterodimers of Fe3O4@ECS/PAA-Ag NPs.The composition and morphology of the resultant nanostructures were confirmed by FT-IR,XRD,TEM and TGA.The overall length of the heterodimers was approximately 45 nm,in which the mean diameter of Fe3O4@ECS/PAA NPs reached up to 35 nm,and that of Ag NPs was around 15 nm.The mass fraction of silver NPs in the nanocomposites was about 63.1%.The obtained Fe3O4@ECS/PAA NPs exhibited good colloidal stability,and excellent response to additional magnetic field,making the NPs easy to recover after antibacterial tests.In particular,the Fe3O4@ECS/PAAAg NPs retained nearly 100%biocidal efficiency(106e107 CFU/mg nanoparticles)for both Gram-negative bacteria E.coli and Gram-positive bacteria S.aureus throughout ten cycles without washing with any solvents or water,exhibiting potent and durable antibacterial activity.