Investigation Of Structure Analysis,Functional Modification And Antibacterial Properties Based On γ-PGA

Bacterial infections kill approximately 17 million patients each year and medical materialrelated infections caused by bacteria are the most common clinical complication,making the prevention of bacterial colonisation of medical material surfaces one of the key challenges in the medical field.The cycle of bacterial biofilm formation is broadly divided into five stages:reversible adhesion,irreversible adhesion,aggregation,maturation and biofilm formation,with bacterial adhesion being the most critical stage.Once bacterial adhesion is irreversible,biofilm formation on the surface of the material can lead to bacterial infection and it is therefore important that bacteria adhering to the surface of the material are killed in a timely and efficient manner.Currently,there are two main construction methods for modifying coatings on the surface of medical materials: surface grafting and layer self-assembly(LBL).However,both methods have certain limitations,such as the complexity and tediousness of the grafting process,and the repeated deposition and cross-contamination problems of LBL.Therefore,it is necessary to find a way to construct antimicrobial coatings on the surface of materials in a simple and efficient way.The polyelectrolyte-surfactant system is an entropy-driven spontaneous process with a rich solution behaviour and solid-phase structure,and by regulating the concentration and molar ratio of both,a polyelectrolyte complex insoluble in water but soluble in organic reagents can be obtained,which is simple and efficient to prepare and not dependent on the coating substrate.As one of the polyelectrolytes,γ-PGA has good potential for biomedical and industrial applications due to its excellent biodegradability and biocompatibility.However,the relationship between the structure and rheological properties of γ-PGA is still unclear due to the small amount of structural and performance-related studies.Based on this,we have investigated the relationship between the structure and rheological properties of γ-PGA.Sinceγ-PGA itself is highly soluble in water and has poor antibacterial properties,we have formed a water-insoluble complex by electrostatic compounding with quaternary ammonium salts,a surfactant with broad-spectrum antibacterial properties,which can be easily and efficiently constructed on the surface of medical materials.coatings with resistance to bacterial infection and long-lasting antimicrobial stability.In summary,the polyelectrolyte-surfactant construction strategy solves the problem of polyelectrolytes being water-insoluble,and is simple,efficient and easy to prepare,overcoming the shortcomings of traditional construction methods;on the other hand,this type of coating provides a new idea for the prevention of bacterial infections associated with interventional medical materials.The specific research work in this paper is as follows.(1)To investigate the basic structural components,morphology and rheological properties of γ-polyglutamic acid(γ-PGA)polyelectrolytes,infrared spectroscopy,nuclear magnetic resonance and cryoelectron microscopy were carried out.The results show that the structural components of γ-PGA contain both glutamic acid and monosodium glutamate,and the proportion of monosodium glutamate accounts for about 60% of the total content.With the addition of salt solution,it will affect the dissociation of γ-PGA polyelectrolyte in the solution,then the solution viscosity will be reduced,and when the polyelectrolyte increases to a certain concentration,then the effect of salt on its dissociation is almost negligible,and the viscosity of γ-PGA polyelectrolyte salt solution is the same as that of water;when the concentration ofγ-PGA is small to a certain degree,then the zero-cut viscosity of the solution is measured as the viscosity of the solvent.(2)Based on the structural composition and viscosity of γ-PGA,a new γ-PGA-quaternary ammonium salt surfactant complex insoluble in water but soluble in organic solvents was synthesized by electrostatic compounding of a suitable molecular weight from γ-PGA with quaternary ammonium salt surfactants of different hydrophobic chain lengths.A γ-PGAquaternary ammonium salt complex with high binding capacity was selected for subsequent experimental characterisation by isothermal titration calorimetry(ITC).The antimicrobial test demonstrated that the composite coating has excellent bactericidal properties and the in vitro test demonstrated that the coating is biocompatible and non-toxic to cells.The composite coating is simple,efficient and non-dependent on the substrate material,and can therefore be used to construct antimicrobial coatings for a variety of medical device surfaces to reduce bacterial-induced infections.This work will provide an effective strategy for the rational design of safe antimicrobial materials to prevent infections associated with biomedical materials.