Surface Functionalization Of Medical Non-woven Wound Dressings And Their Antibacterial Performances

Wound dressing is applied to wound to promote recovery and prevent further harm.Non-woven dressing which is widely used,exhibits a high levels of porosity,excellent gas permeation and hygroscopicity,good softness and comfort.An ideal wound dressing has many requirements,such as,imparting a moist environment,allowing gas exchange,absorbing effusion,preventing wound from bacteria infection,removing painlessly.The most important performance is antibacterial property.Wounds are easily attacked by bacteria.As for wound dressing,bacterial contamination and associated risk of infection is one of the most serious complications because they will cause the deterioration of wound,surgical failure,in severe cases,death.However,most of the wound dressing can not meet the antibacterial requirement,like polypropylene(PP)non-woven and chitosan(CS)non-woven.In this thesis,two kinds of dressing are designed to satisfy the antibacterial property by constructing bactericidal and antifouling surfaces.The antibacterial dressing can prevent the wound from bacterial infection and promote wound healing.The detailed investigations are listed as follows.Part ?:Integrated antifouling and bactericidal polypropylene wound dressing through bioinspired polydopamine/poly(N-vinyl pyrrolidone)coatingPolypropylene(PP)non-woven has been widely used as wound dressing,however,the hydrophobic nature of PP can initiate bacterial attachment and subsequent biofilm formation.Generally,there are two common approaches to impart antibacterial property to a material.One approach is an "attacking" method which utilizes a wide range of bactericides or drugs including silver ions,cationic polymers,and antibiotics to actively kill bacteria.However,drug resistance or poor biocompatibility is of great concern.The other approach is a"defending" method which uses antifouling coatings,e.g.,poly(ethylene glycol),zwitterionic materials.While the key deficiency of this bacteriostatic method is that this passive coating can't kill bacteria or inhibit them proliferation once they attached on the surface.Many efforts have been made to combine antifouling and bactericidal strategies for mitigating their disadvantages.However,these antibacterial coatings are not universal to different types of substrate materials,and their procedures are usually complicated,thus limit their widespread clinical applications.Polydopamine(PDA)is prone to adhere on almost all types of surfaces easily and the as-prepared surface can further react with thiols or amines.Herein,we combine the two strategies of active bactericidal functions and passive antifouling property into a surface by PDA to modify the PP non-woven facilely,that integrating antifouling poly(ethylene glycol)(PEG)components and active bactericidal poly(N-vinyl pyrrolidone)-iodine(PVP-I)components.PVP and PEG are successively tethered onto PP non-woven surface via versatile bioinspired dopamine(DA)chemistry,followed by complexing iodine with PVP moieties.It is demonstrated that the as-prepared PP non-woven integrates both antifouling property and bactericidal property.It can resist bacteria,platelet,red blood cell adhesion,and kill the few attached bacteria at the same time.The main conclusions are listed as follows:(1)The balance between antifouling and bactericidal performances depend on the mass radio of PDA to PVP.Based on the characteristic peak of attenuated total reflectance FTIR(ATR-FTIR)and color change,we select the ratio of 1:1 for the following experiments.(2)As confirmed by the X-ray photoelectron spectroscopy(XPS),surface hydrophilicity,the color change and the surface morphologies,PEG and I2 have been successfully grafted.(3)Through the field emission scanning electron microscope(SEM)and spread plate method,it is demonstrated that the as-modified PP non-woven integrates both antifouling property of PEG for suppressing bacterial adhesion,and bactericidal property of PVP-I for killing the few adherent bacteria.Meanwhile,it can greatly resist platelet and red blood cell adhesion,and the morphologies of blood cells are not active or damage,illustrating complexing iodine does not influence its hemocompatibility.Part ?:Facile fabrication of bactericidal and antifouling switchable chitosan wound dressing through a 'click'-type interfacial reactionChitosan(CS)has good biocompatibility,biodegradability and non-toxicity together with its antimicrobial activity and low immunogenicity.Although CS has antimicrobial activity,its antimicrobial efficacy is influenced by several factors,e.g.,deacetylation degree,ionic concentration,pH,bacterial species,etc.It has been confirmed that CS exhibits low antibacterial activity at physiological pH.The limited antimicrobial property of CS can not meet the requirements of wound dressing.At present,"attacking" method was mainly adopted to improve the antibacterial property of CS,i.e.,physically loading and releasing bactericide,or chemically immobilizing bactericide for sterilizing on contact.As mentioned above,both good antibacterial efficacy and good biocompatibility can't meet simultaneously.Azlactones are lactone-based functional groups that can react rapidly,quantitatively,in the absence of a leaving group,with a broad range of functional nucleophiles through the fast and efficient'click'-type reactions.And CS has a large number of primary amines.Thus,we propose a facile approach to functionalize CS non-woven surface with the bactericidal and antifouling switchable moieties that make use of the 'click'-type reactions between primary amines in CS backbone and azlactone groups in azlactone-carboxybetaine ester copolymer.Azlactone-cationic carboxybetaine ester copolymer(Q-p(VDMA-co-CEA))was firstly prepared,then chemically attached onto CS non-woven surface through the fast and efficient'click'-type interfacial reaction between CS primary amines and azlactone moieties.The CS non-woven surface functionalized with cationic carboxybetaine esters is able to kill bacteria effectively.Upon the hydrolysis of carboxybetaine esters into zwitterionic groups,the resulting zwitterionic surface can further prevent the attachment of proteins,platelets,erythrocytes and bacteria,exhibiting excellent antifouling performance and hemocompatibility.The main conclusions are listed as follows:(1)The chemical structure of poly[(2-vinyl-4,4-dimethylazlactone)-co-(2-chloroethyl acrylate)](p(VDMA-co-CEA))and Q-p(VDMA-co-CEA)are characterized by 1H NMR and ATR-FTIR.(2)The ATR-FTIR characteristic peaks and the water contact angle change of the Q-p(VDMA-co-CEA)modified CS non-woven(Q-CS)show the successful grafting of Q-p(VDMA-co-CEA).The hydrolysis of carboxybetaine esters into zwitterionic groups is demonstrated by ATR-FTIR results and the change of water contact angle,successfully obtaining the zwitterionic CS non-woven(Z-CS).(3)The CS non-woven functioned with cationic carboxybetaine esters can efficiently kill bacteria,because the morphology of attached E.coli is deformed and collapse as shown in SEM.After hydrolysis,the zwitterionic surface has excellent antifouling property,because the surface density of attached bacteria,proteins,platelets and erythrocytes is very few.