The Effect Of Surface Modification Of Silicone Rubber On Adhesion And Antibacterial Performance Of Ag Coatings

Coating the antibacterial agents on polymer materials is an effective and simple way to prepare the antibacterial polymer.The Ag coatings deposited on polymer surface could serve as an antibacterial layer and have excellent antibacterial performance.However,the adhesion strength between the metal-based antibacterial coatings and polymer substrates is inherently poor,leding to limited applications in the field of medical and health care.In this experiment,the antibacterial coatings with different adhesion force were achieved by the surface modification.And the effect of adhesion force on the Ag+ release rate was explored in details.In this study,firstly,the surface of silicon rubber was modified by the plasma irradiation to generate active groups(such as hydroxyl and peroxide)on the inert silicon rubber surface,followed by the graft of polyvinylpyrrolidone(PVP)or chitosan(CS)on the modified surface to improve the adhesion strength between the antibacterial coatings and substrates.The surface roughness was observed by the atomic force microscopy(AFM)before and after the plasma irradiation.The surface wettability was tested by the static contact angle measurement instrument.Adhesion force was measured according to ASTM D3359-02.The scanning electron microscope(SEM)was used to observe the surface morphology.In oeder to investigate the effectiveness and durability of the antibacterial properties,the samples with different adhesion force were immersed into the PBS solution and the amounts of Ag+ released from the samples were monitored by the inductively-coupled plasma atomic emission spectrometry(ICP-AES).The fluorescent staining method and plate colony-counting methods were employed to explore the durability of antibacterial properties.The microplate reader was also applied to detect the optical density(OD)of the bacterial solution.The results showed that the adhesion force had evidential effect on the release rate of the silver ions on coatings,and the optimum adhesion strength could both protect the coatings from sliping down from the substrate and provided sustained Ag+ release.The results are as follows:(1)The surface roughness of the silicone rubber was improved after the plasma irradiation,and the larger contact area between the substrates and coatings was helpful to the enhancement of adhesion.(2)The active functional groups on irradiated surface intereated with PVP or CS,covalently bonded them onto the substrates surface.(3)The pyrrole ring of PVP captured silver ions and improved the adhesion force between the substrate and coatings(3B).Simultaneously,the chitosan carries polar and H-bonding functional groups,viz.hydroxyls and amines.Lone pair electrons on O and N anchored silver ions by donating electrons and provided strengthened adhesion(4B).(4)Comparing the release rate of Ag+ from Ag/PVP?Ag/CS and Ag/KH590,the rate from Ag/PVP was the fastest,making it achieve obvious antibacterial effect in the shortest time.But the coatings shed form the substrate easily.On the contrary,the Ag+ release rate from Ag/KH590 was the slowest,and it exhibited weakest antibacterial effect during longer time.It was noticed that the relatively modest release rate from Ag/CS displayed durably effective antibacterial performance as well as satisfied adhesion.(5)Coatings exhibited different microtopography was supposed to be responsible to the different Ag+ release rate.