Study On The Key Designing Technology And Properties Of Ocular Punctal Plug For Dry Eye Disease

Part?Feasibility study on the electrospinning process in fabricating core-shell structured microcapsulesObjective:The purpose of this study was to investigate the feasibility of an advanced nano-technology the electrospinning process in fabricating core-shell structured microcapsules, to reveal the basic regularity rule of electrospinning process in fabricating core-shell structured microcapsules via changing different electrospinning condition parameters, which will provide the experimental foundation for further study on drug delivered microcapsules and advance the process of successfully designed biodegradable controlled releasing drug loaded punctal plug. The results of this study will broaden the application scope of the nano-technology electrospinning process in the field of biomedicine. Methods:This was achieved by using excellent biocompatible natural polymers such as chitosan,, hyaluronic acid and alginate sodium as the main materias, and using biocompatible synthetic polymers as adjuvant material, through adjusting different concentration proportion ratio to produce electrospun microparticles. Then take advantage of the difference in charge characteristic among the polymers, using modified solution collecting method to receive the electrospun microparticles to fabricate core-shell structured microcapsules, using vacuum filtration machine to collecting the microcapsules on the surface of the micropore filter membranes, which were then examined by SEM to evaluate the shape, dispersion and uniform of the microcapsule and examined by TEM to reveal the interrelationship of the core and shell structure of the microcapsules. With statistically analyzing the particle diameter of the microcapsules, the distributing range and mean size of the microcapsules were calculated. By change the collecting solution or by changing the concentration of the collecting solution, we elucidate the basic characteristics of electrospinning-modified solution collecting method in producing core-shell structured microcapsules.Results.Through varing the concentration ratio of chitosan and PEO blends, we finally found that at the concentration ratio with 3% Chi:6.5% PEO and electrospinning parameters to be at voltage 15Kv, fluid speed 0.1ml/h and DBPC 15cm micropaticles can be produced by electrospinning. Then via electrospinning-modified solution collecting mothed, using HA or alginate as the colleting solution, take advantage of the difference between the polymers, we could further get well-dispersed, smooth-surfaced core-shell structured Chi/PEO@HAand Chi/PEO@ALG microcapsules. Statistical analysis results showed that microcapsules diameters were ranged from 700-1500nm and the mean diameter was 1123nm. Through changing the collecting solution or concentration of the collecting solution we found that 0.3% HA and 1.2% alginate solution was better in producing well-dispersed microcapsules and the diameter of the microcapsule was increasing as the concentration of the collecting solution increased.Conclusion:This study firstly testified the feasibility of nano-technology electrospinning process in produing Chi/PEO microparticles. Using modified solution collecting method to receive the electrospun Chi/PEO microparticles, utilizing the principle of electrostatic interaction, core-shell structured Chi/PEO@HA and Chi/PEO@ALG microcapsules were successfully fabricated, which further confirmed the feasibility of electrospinning modified solution collecting mothod in fabrication of core-shell structured microcapsules. The results will provide substantial experimental foundation for the further study on the drug-loaded microcapsules and for the finally successful fabrication of biodegradable controlled-releasing punctal plug. Part IIFabrication of drug-loaded microcapsule and the study on its propertiesObjective:The purpose of this study was to investigate the feasibility of electrospun microcapsule to load drug and its ability in adjusting drug loading amount. Further investigation was performed to study the releasing properties and compatibility of the drug loaded microcapsules, which will establish a substantial foundation for the manufacture of biodegradable controlled releasing punctal plug and will provide an new research approach in designing controlled releasing materials, scaffolds for clinical application.Methods:Different model drugs, such as estrodiol, cyclosporine A, rhodamine, levofloxacin, were added into the Chi/PEO blends respectively to a final concentration at 5mg/ml. The collecting solution was 0.3% HA solution. After adjusting all the electrospinning parameters, eletrospun productions were collected and then filterd through the micropore filtration membranes for SEM examination. Different concentrations of model drug were also added to the Chi/PEO blends for evaluating the ability in drug loading amount adjustment. According to the method of "Chinese Pharmacopoeias" in accessing the controlled releasing propertities, samples were fetched at different time point and measured by UV-Spectrophotometer. Drug loaded microcapsules electrospun from different conditions were also observed and accumulated releasing rates were calculated to evaluating the properties of the microcapsules. Leaching liquor of the microcapsules was used to culture the corneal epithelium cells to evaluate the biocompatility of the microcapsule hydrosols. MTT method was used to calculate the relative growth rate (RGR) and the results were evaluated according to the National Standard GB/T 1688615—1997 for the biocompatibility evaluation.Results:Different kinds of model drugs (such as estradiol, cyclosporin A, rhodamine and levofloxacin) mixed in the Chi/PEO blends were all successfully electrospun for drug loaded microcapsules and the drug loading amount could be adjusted according to different purpose. Lavofloxacin was used as a model drug for controlled releasing characteristic study. While comparing the performance of the electrospinnig group and the non-eletrospinning group (mechanically mixed group), different concentration of drug loading groups and different concentration of collecting solution groups repectively, encouraging results were showed that electrospinning group manifest greater controlled releasing ability than the contrast group. The results also showed that higher drug loading concentration displaying a higher releasing speed whereas higher collecting solution concentration displaying a lower releasing speed. Leaching liquor of the microcapsule collecting solution was used to culture corneal epithelium cells and were measured by MTT method which showed the biocompatibility belong to grade 1 according to the national standard, implying a fine biocompatibility.Conclusion:This study first demonstrated the feasibility of electrospinning-modified solution colleting method to fabricate drug loaded microcapsules via mixing different drugs into the Chi/PEO blends. The releasing profile of the microcapsules were also studied and showed a controlled releasing capability. The evaluating test of biomaterials biocompatibility also testified the fine biocompatilbility of the microcapsules hydrosel, which allow a further study on the biodegradable punctal plug for dry eye disease.Part?Crosslink modification of microcapsules hydrosel and the primary study on punctal plug manufactureObjective:The purpose of this study was to modify the dissolubility of the microcapsules by crosslinking in order to increase its anti-degradability, prolong its resident time for long-time controlled release while maintaining its fine biocompatibility. Process a primary study on the punctal plug using the crosslinked hydrosel materials. The physical, chemical, biocompatibility as well as the degradability were studied, which will promote the success in manufacturing biodegradable controlled-releasing punctal plug for dry eye disease and improve the life quality of the patients. Methods:Using two different methods (ADH/EDCI method and BDDE method) to crosslink the microcapsule hydrosel with electrospinning-solution collecting method, 1g microcapsule hydrosel were mixed with a certain proportion of the crosslinking agent and stirred quickly to get the crosslinked HA gelatin which was then dialysed and purified with pure water. The crosslinked gelatin sample was soaked in the PBS with constant temperature and agitating water bath for interval observation of the degrading performance. The punctal plug was manufactured using the crosslinked gelatin materials and its biocompatibility and biodegradability were studied.Results:Both of the two methods (ADH/EDCI method and BDDE method) could successfully crosslinked the microcapsule hydrosel with electrospinning-modified solution collecting method. While using ADH/EDCI method, the gelatin was transparent, with good elasticity and low biodegradability. Using BDDE method, the gelatin was lightyellow with little fluidity and good viscoelasticity, as well as low biogegradability.Conclusion:This study first testified the feasibility in using different crosslinking agent to modify microcapsule hydrosel to increase its anti-degradability and prolong resident time for long-time controlled release. The punctal plug using the crosslinked materials was with certain elasticity, fine biocompatibility and low biodegradability. The results primarily accomplished the design of biodegradable controlled releasing punctal plug. However, the details of the process of crosslink and punctal plug modification still need further study.