Preparation Of Antibiotic Delivery System Coated On The Surface Of Titanium Alloy Implant And Evaluation Of The Drug Release In Vitro And In Vivo

Objective:1. To investigate the technique of gentamicin gelatin microspheres （GT-GMS）preparation and to evaluate the physical and releasing characteristics of GT-GMS invitro.2. To explore the method of fabricating antibiotic delivery systems coated on the surfaceof low elastic modulus β titanium alloy, and evaluate the effect of anti-infectivematerial prepared by coating the antibiotics microspheres to the surface of titaniumalloy.3. To search for new prophylaxis and therapeutic modalities for IAOMI through theseries of studies.Methods:1. The preparation of GT-GMS and assessment of some characteristics in vitro:(1)Thiolated modification to gelatin and detection of the degree;(2) Prepared GT-GMS by the improved double emulsion method and achieved the crosslinkingwith the solution of genipin;(3) Observed the morphology and characteristics of thesurface of the GMS by using an optical microscope and scanning electron microscoperespectively, and detected the sizes and ranges of particle sizes of the GMS by usingthe particle size analyzer;(4) Detected the drug loading and encapsulation efficiencyof the GT-GMS, released the drug from GT-GMS with the method of dynamicdialysis and evaluated the characteristics of drug releasing in vitro.2. Coating of the GT-GMS on the surface of titanium alloy:(1) Made the micro-trenchon the surface of titanium alloy by laser etching, and observed the surfacemorphology with the scanning electron microscopy; selected the optimal width ofmicro-trench which fit the growing of cell, obtaining evidence from the experimentsof cellular proliferation and adhesion on the surface of the titanium alloy withmicro-trench;(2) Detected the poly-DOPA coating by XPS after depositing it on thesurface of titanium alloy;(3) Fabricated the composite material via a chemicalreaction by coating the thiolated GMS onto the material coated by poly-DOPA, andthen detected the composite effect of the process;(4) Evaluated the drug-releasingcharacteristics of the composite material in vitro by using the dynamic dialysismethod, verified its characteristics of drug release in vivo by implanting it in themuscle pouch of mouse, and meanwhile evaluated the antibacterial performance invitro by means of the agar plates inoculated with bacteria.Results:1. Results of GT-GMS preparation and its characteristics in vitro.(1) The thiolateddegree of gelatin: each gram of gelatin contained9.71±0.51mmol sulfhydryl;(2)Physical morphology of the GMS: GT-GMS were prepared in an average particle sizeof1.61、13.45and56.14μm, which featured in regular and smooth surface, as well asdistribution range of the particle size from1to100μm;(3) Pharmacologicalcharacteristics of the GT-GMS: a method of spectrophotography was explored todetermine the gentamicin sulfate, and the drug loading and encapsulation efficiencywere (63.71±0.8)%and (81.16±1.2)%respectively; the three kinds of GT-GMS could release the gentamicin in vitro for at least30days.2. Results of coating the GMS on the surface of titanium alloy.(1) Micro-trench on thesurface of titanium alloy: the scanning electron microscopy showed that the width ofthe trenches on the titanium alloy were50、100、200μm and the structure wasregularly arranged; it was showed in the experiments of cellular proliferation andadhesion that the200μm micro-trench excelled in the proliferation with respect toamount and the adhesion concerning morphology;（2) Results of the DOPA coating:the thickness of the coating on the titanium alloy surface was greater than20nm;(3)Through quantitative screening method, when the200μm micro-trench coated withthe comparatively larger GT-GMS of56μm, the most obvious effect of payload ofantibiotics would be achieved, and scanning electron microscopy revealed that theGMS existed densely on the surface of the titanium alloy;(4) Drug release in vitroand in vivo of the composite materials and the results of antibacterial performance invitro: gentamicin could be released continuously from the anti-infective material for atleast30days in vitro and in vivo, which was consistent with the drug-releasing periodin the antibacterial experiment in vitro.Conclusion:1. GT-GMS with a higher drug loading and superior drug-releasing effect could beprepared by the improved double-emulsion crosslinking method.2. The anti-infective material could be fabricated by coating thiolated GT-GMS on thesurface of titanium alloy with micro-trench and DOPA coating, and the material wascontinuously and effectively anti-infective. The regular micro-trench facilitated thecellular growth on the surface of the titanium alloy.