Synthesis Of Ph-responsive Polymers And Their Applications In The Prevention Of Spinal Surgical Site Infections

Background:Surgical site infections(SSIs)mainly caused by pathogenic bacteria,is one of the most common complications in spinal surgery.It is reported that the local application of vancomycin is an important means to reduce SSIs,however,there are some disadvantages,such as burst drug release,unstable drug release behaviors,and ineffective drug controlled release performance.Staphylococcus aureus in the host decomposes sugars and produces acids which lead to the acidification of the surrounding environment.According to the characteristics of microenvironment change of Staphylococcus aureus infection,a series of pH-responsive drug-loaded polymers were prepared to meet the requirement of stable drug release in the early stage,and bacterial reproduction led to environmental acidification which induce rapid drug release,such systems could prevent spinal surgical sites infection.Objective:We have prepared the pH-responsive vancomycin nanoparticles,and investigated their structures,stabilities,controlled release behavior of drug-loaded nanoparticles,which have wide applications in the prevention of surgical site infection in animal models.Methods:Based on the chemical synthesis and 1?7 branching point strategy,we have prepared POSS hyperbranched polymer by the host-guest interactions;Through the Schiff base reaction,we have obtained amphiphilic PEG-Van polymers;By combination of the embedding physics and chemical methods,we have yielded the drug-loading PEG-Van@Van nanoparticles.Their structures were characterized by NMR,Ms and TEM;the drug release behaviors were investigated by UV spectrometer and HPLC;the bacteriostatic efficacy and biosafety were analyzed by in vitro experiments,animal experiments and pathological sections.Statistical analysis:the measurement data were statistically analyzed by the repeated measurement analysis of variance,and the rank sum test of kruskal-wallis was used to analyze the grade data.P<0.05 was considered statistically significant.Results:1.By combination of 1?7 branching strategy and supramolecular polymerization,here we demonstrate a simple approach to prepare the well-defined POSS-embedded stimuli-responsive supramolecular hyperbranched polymers(POSS-SSHPs)with monomer concentration-dependences,pH-and light-triggered disassembly behaviors and solvent polartiy-relied morphological transitions.Further addition of an appropriate amount of competitive guests in selective solvents can achieve another well-organized morphology transitions by the multiple supramolecular driving forces of host-guest inclusion complexations,hydrophilic-hydrophobic interactions and unique POSS aggregation behaviors.2.A pH-responsive amphiphilic prodrug was synthesized by conjugating vancomycin to poly(ethylene glycol)via an acid-labile Schiff base linker,which can self-assemble into the spherical micelles and maintain the stability of nanoparticles in a neutral environment but quickly destroy the polymeric structures due to the breakage of schiff base bonds in an acidic environment.In this case,this PEG-Van polymeric assembles possessed the smart pH-triggered drug release of vancomycin.3.Combined with the advantages of physical embedding and chemical bonding,pH-responsive amphiphilic prodrug(PEG-Van@Van)was prepared to achieve the high dose loading and rapid and effective release of vancomycin molecules.4.The trisaccharide iron experiment and the pH monitoring experiment of the spinal surgery site in rats confirmed the characteristics of glycolyces acid secretion in the process of proliferation of Staphylococcus aureus.5.Supramolecular POSS-SSHPs polymer had dual-stimuli(pH and UV)responsiveness;in vitro bacteriostatic experiments showed that in the same 2 ?g vancomycin dose,POSS-SSHPs@Van inhibition ring size is significantly different(POSS-SSHPs@Van group:vancomycin group = 9.0±0.3:7.0±0.3,p<0.001.,unit:mm).6.The amphiphilic PEG-Van prodrug molecule is stable under neutral conditions and releases vancomycin under acidic conditions;in the cytotoxicity test,when the polymer concentrations reached 200?g/mL,the cell survival rates were above 90%,indicating the good biosafety;in vitro bacteriostatic test showed that the size of inhibition zone was significantly different in the same 5 ?g vancomycin dose(PEG-Van group:vancomycin group = 7.1±0.2:5.0±0.2,p<0.001,unit:mm).Statistical analysis of pathological sections at the surgical site(PEG-Van group:blank control group t=4.314,p<0.001)showed significant differences in cellulosic changes in the surgical site.Laboratory blood tests showed the statistical analysis of-two weeks after surgery white blood cell COcount was significant cdif'ference(PEG-Van group:blank control group = 14.0± 3.3:19.0±2.2,F = 14.53,P<0.001 unit:109/L).7.The polymer-loaded PEG-Van@Van nanoparticles had sensitive acid responsiveness.The release rate is 28.2%at pH=7.4,and the release rate is 94.6%at pH=5.In vitro bacteriostatic test showed that the size of the inhibition zone was significantly different in the same 2?g vancomycin dose(PEG-Van@Van group:vancomycin group ? 11.0±0.3:7.0±0.3,p<0.001).Statistical analysis of pathological sections at the surgical site showed significant differences in the changes of tissue abscess in the surgical site(PEG-Van group:blank control group t=4.602,p<0.001).Laboratory blood tests showed the statistical analysis of two weeks after surgery significant differences in white blood cells(PEG-Van@Van group:blank control group = 15.0±2.3:23.0±4.9,F = 18.17,P<0.0001).Conclusion:Three vancomycin nanoparticles,POSS hyperbranched polymer,PEG-Van and PEG-Van@Van?have the advantages of safety and non-toxicity,simple and efficient preparation process,flexible structure control and diverse performance construction.Compared with the pure vancomycin at the same concentration,three kinds of polymer nanoparticles can achieve the high effective loading,controllable release of vancomycin and significant antibacterial effects.Combined with the advantages of physical embedding and chemical bonding,pH-responsive amphiphilic prodrug(PEG-Van@Van)was prepared to achieve the high dose loading and rapid and effective release of vancomycin molecules.Therefore,it has been found that PEG-Van@Van has the ability to release drugs in a highly efficient and responsive manner via the verification of bacterial and animal experiments.The drug-loaded polymeric materials have good storage stability.Which had a good prospect in the prevention of infection in the spinal surgery site.