Study On The Construction And Surface Properties Of Poly(N-isopropylacrylamide)Microgel Particle Films

Medical implants play an important role in the treatment of various diseases,however,bacterial adhesion to the implant surface can result in serious inflammation and bacterial infections.Although the use of antibiotics has reduced the risk of infection to some extent,their long-term use may lead to the development of drug-resistant bacteria.When bacteria proliferate on the implant surface to form a biofilm,the bactericidal effect of antibiotics will be greatly reduced.Surface modification such as anti-bacterial surfaces,without altering the properties of the body materials,can prevent bacterial infections by inhibiting the initial adhesion of bacteria.However,there are many limitations to the construction of conventional anti-bacterial surfaces.For example,the lack of active sites on the surface of many materials limits the modification density of functional molecules.Special activation treatments(e.g.,plasma treatment,strong acids,alkaline)tend to damage the surface or the body of the material,and these strategies lack universality depending on the polymeric materials.Microgels are composed of soft and deformable colloidal particles,which can form uniform particle films Besides,colloidal particles contain various reactive functional groups,and their chemical composition can also be regulated during the polymerization process,which is of great significance for surface modification strategies on biomedical materials.In addition,colloidal particles can be formed by simple means like drop coating,dip coating or spin coating,showing excellent "substrate universality".This general approach has proven effective for surface modification,but little is known about methods to control the properties of the colloidal particles to regulate film formation and biological function.Here,this paper mainly focuses on the following two aspects:(1)Poly(N-isopropylacrylamide)microgels(ZQP)were successfully prepared by precipitation polymerization,containing both a zwitterionic component(Z)to provide antifouling functionality,and a quaternary ammonium salt(Q)to give bactericidal functionality.Fine-tuning of the Z and Q contents allowed the preparation of microgels over a range of particle size,size distribution,charge,and film-forming capability.The films showed antiadhesion and contact-killing properties versus Escherichia coli(E.coli),depending on the chemical composition.They also showed excellent cytocompatibility relative to L929 cells.A variety of microgel-coated substrates(Silicon wafer,PDMS,PU,PVC)showed long-term anti-bacterial activity and resistance to chemical and mechanical treatments.It is concluded that ZQP microgels will have great advantages in constructing highly-effective anti-bacterial surfaces due to their composition-tunable,substrate universality,and cell-friendly properties.(2)Quaternary ammonium salt PNIPAm microgels(QP Microgel)were successfully prepared by precipitation polymerization.In addition,fluoride-modified silica nanoparticles(SiO2-F NPs)were prepared by sol-gel method.Surface modification of various biomaterials(Silicon,PU,PDMS,PVC)pre-modified with QP Microgel using a simple drop-coating method to further construct QP/SiO2-F NPs hybrid superhydrophobic surfaces.The particle size,size distribution and surface charges of QP Microgel and SiO2-F NPs were then studied separately,demonstrating that electrostatic interactions were the main drivers for the construction of hybrid superhydrophobic surfaces.The water contact angles of these modified biomaterial surfaces all exceeded 150°,showing "superhydrophobic" and"substrate universality".They also showed efficient anti-adhesion abilities against E.coli and L929 cells.In vitro cytotoxicity assays,QP/SiO2-F NPs exhibited excellent cytocompatibility.In addition,QP/SiO2-F NPs significantly inhibited the growth of biofilms against Gram-positive bacteria S.aureus.In summary,the hybrid superhydrophobic surfaces prepared from positively charged QP Microgel and negatively charged SiO2-F NPs have the advantages of substrate universality,inhibition of microbial adhesion and biofilm growth,and non-cytotoxicity,showing great potential for preventing bacterial infections.