Study On The Design And Properties Of Textile-based Anti-biofilm Ureteral Prototype Stent

Bacterial biofilms on the surface of implants are commonly found in various fields,including oral prostheses,orthopedic implants,and urological implants,and compose a main threat to implant failure.Among them,urological implants,represented by ureteral stents,are more commonly colonized by bacteria due to their proximity to the in vitro environment.In this paper,based on the systematic analysis and generalization of the mechanism of biofilm formation on the implant surface and the related studies on anti-biofilm strategies,we improved and innovated the traditional anti-biofilm strategies from the perspectives of pathogens,biomaterials and the interaction between materials and biofilms.The feasibility and mechanism of in vivo locoalized controlled-release,anti-adhesion and anti-biofilm strategies in the urological system were explored.Considering the positive role of dynamic biodegradable surfaces in anti-biofilm and the medical trauma of secondary extraction surgery of ureteral stents,we developed a textile-based antibacterial biodegradable ureteral stent and explored their anti-biofilm mechanism.The specific results are as follows.(1)From a pathogen perspective,in order to address the abrupt releaseproblem faced by conventional drug-eluting stents,multiple nano-retarded release barriers were construct.We proposed an intraoperative drug delivery strategy for customized medicine and a matching nanofiber biotape(NFBT)to prepare a modular nano-barriar release system that can be temporarily loaded on the surface of ureteral stents.The NFBT with micrometer thickness was produced using electrospinning technology.NFBT showed good tensile strength and was firm Ly bonded to the polymer stent due to the electret treatment during electrospinning and the suitable elastic modulus of the NFBT.NFBT can resist the slippage caused by ureteral peristalsis.NFBT exhibited a zero-level release for up to 28 days with the hydrophobic model drug Nitrofurantoin(NFT)and a fitted Higuchi model with the hydrophilic model drug Rhodamine B(RB).In vivo experiments showed that NFBT-NFT maintained a sustained release in the urinary system of porcines,during which>99.9%antimicrobial rate was consistently maintained,and the NFT drug dosage was only 2.68 wt%of the recommended dosage in systematic administeration.Due to the consistent release of antibiotics in the NFBT-NFT group,bacterial concentrations in the urine were much lower than in the control group,and biofilms and encrustration on the surface caused by bacterial adhesion were reduced accordingly.Histological analysis showed that the inflammatory response in both distal and proximal tissues was significantly lower in the NFBT-NFT group than in the control group,demonstrating the therapeutic efficiency of NFBT as a local delivery system.The analysis of routine blood and blood biochemical parameters supported that the sustained release of 150 mg of NFT in the urinary system by NFBT-NFT did not cause damage to the liver and kidney functions of the animals.(2)From the perspective of biomaterials.Conventional polymer ureteralstents cannot cope with protein deposition and bacterial adhesion.We constructed a synergistic"anti-adhesion and contact-killing"anti-biofilm degradable ureteral stent.We developed a"fiber-film"biodegradable ureteral stent(FMBUS)by braiding and thermal treatment,which has similar morphology,size,and radial support to commercial polyurethane stent(PUUS).The interwoven fiber structure of the stent divided the membrane structure into micron-sized degradation units,and the size of the degradation fragments was controlled to prevent obstruction to the ureter.As the surface amino density of the stent increases.On the one hand,the water contact angle of the stent decreased from 102.7±1.51°to 0°,and the contact between the stent and the aqueous solution could form a hydrated layer with underwater superoleophobicity.On the other hand,the surface zeta potential of the scaffold tube shifted from-35.58±0.6 m V to+21.36±1.36 m V.The barrier effect of the hydrated layer and the electrostatic adsorption of surface charges simultaneously affected the protein adsorption behavior.After reaching the hydrophilic domain,the barrier effect of the hydrated layer overcomed the electrostatic adsorption,and the stents repelled both the positively charged lysozyme and the negatively charged human serum albumin.After the introduction of hyperbranched poly(amide-amine)(HBPAA),the scaffold tubes could inhibit>99.9%of the adhesion of Staphylococcus aureus and Escherichia coli.The results of anti-bacterial adhesion also showed that the final adhesion on the surface of the stent was less than 100 CFU/cm at a concentration of 10~8 CFU/m L,which also confirmed the synergistic anti-biofilm mechanism of contact-killing and anti-protein adhesion.In vivo experiments using white porcine model showed that the degradation time of the fibrous membrane structured stent was 7-14 days,and significant deformation and collapse of bacteria were observed on the surface of HBPAA-PDA-FMBUS-4.The bacterial count on the stent surface showed that the stent exhibited>99%inhibition at day 4 and maintained>90%at day 7 after implantation,showing a stable anti-biofilm effect.(3)From the perspective of the interaction between biofilm and implant material,a synergistic"contact-killing and degradation"anti-biofilm ureteral stent was constructed for the maturation and dispersion stages of biofilm to further enhance the match between the contact-killing effect and the degradation behavior of the stent.Herein,a hyperbranched poly(amide-amine)-capped Ag shell and Au core nanoparticle(Ag@Au NP)-embedded fiber membrane-structured poly(glycolic acid)/poly(actic-co-glycolic acid)(PGA/PGLA)ureteral stent was constructed.The nanoparticles are thermally stable and reducible due to the stability and reducibility of HBPAA at high temperature and the thermal stability of Ag@Au nanoparticles.The Ag@Au NPs was adsorbed into the braid and fixed into the stent by thermal treatment.HBPAA acted as a reducing agent to protect the NPs from oxidation and a bridge to covalent the NPs to PGA/PGLA.Ag@Au NPs-FMBUS showed rapid and effective bactericidal effects against E.coli and S.aureus.Under the hydrolysis of PGA and PGLA,the stent showed a changing surface in a simulated degradation environment.Due to the uniform distribution of NPs across the cross-section of the scaffold,the inhibition rate of the scaffold was maintained above 90%at each time point of degradation.Furthermore,due to the covalent connection between NPs and PGA/PGLA via amide bonds,only 6.7 wt%of Ag and Au elements(～8μg)were released from the scaffold after 16 days of degradation,avoided potential cytotoxicity.In the UTI infection model,after days 4 and 7 of implantation,the surface of the degradable stent was not conducive to bacterial adhesion due to instability.Significantly less bacterial adhesion was be observed on the surface of the biodegradable sten than PUUS.It indicated that in response to the high concentration of bacteria in urine,FMBUS can interfere with the biofilm formation by forming an unstable dynamic surface through degradation behavior.After being loaded with nanoparticles,bacteria showed significant structural rupture and the adhesion amount was significantly reduced,which exhibited an inhibitory effect on biofilm.The number of bacteria on the surface of the scaffold showed a trend of increasing and then decreasing,which proved that Ag@Au NP-FMBUS had a bactericidal effect on the basis of degradation and achieved a synergistic"contact-killing and biodegradation"anti-biofilm mechanism.In summary,this thesis addressesed the problem of urinary infection caused by biofilm and encrustation of ureteral stent,and constructed"controlled release","anti-adhesion and contact-killing"and"contact-killing and biodegradation"anti-biofilm strategy from three key factors(pathogens,biomaterials and the interaction between materials and biofilms)of biofilm formation.Provided a reference for the anti-biofilm strategies of other implantable biomaterials,drug delivery carriers and biosensors and other medical devices.