Design And Evaluation Of Ion-exchange Eye Nanosuspension Based On Pre-corneal Retention Enhancing

In this study,anti-glaucoma drugs（betaxolol hydrochloride,BH）was selected as a model drug.The nano-technology and ion-exchange technology were used to prepare a novel chitosan nanoparticles with positive charge,combining with ion-exchange performance of montmorillonite（Mt）and finally obtained ion exchange nano-drug delivery system（Mt-BH/CS NPs）to improve their therapeutic efficacy.The preparation methods and freeze-drying process of Mt-BH/CS NPs were designed and evaluated.Irritation evaluation,corneal permeability,in vitro pre-corneal retention time,tear elimination in rabbits and the effect of lowing intraocular pressure were investigated.Those results showed that the potential applications of the novel ion-exchange nanoparticles as a pharmaceutical carrier in the treatment of glaucoma were revealed.The preparation process of which chitosan（CS）and sodium polyphosphate（TPP）formed nanoparticles under a mild and non-toxic reaction condition by ion gel method was improved（has applied for a patent）.At the same time,the acid-Mt（montmorillonite treated with acid）developed by our laboratory before（have obtained a patent）was intercalated into the nanoparticle to prepare ion exchange nanocarrier for anti-glaucoma drug.The drug loading,encapsulation efficiency were 9.99%±0.076%and59.06%±0.56%,respectively.The result of in vitro release showed that the BH solution was completely released in 3 h,and the BH/CS NPs（without Mt）were released continuously for 10 h（the cumulative release was 94.20%）.After the intercalation of Mt,the cumulative release of Mt-BH/CS NPs was84.94%during 10 h,which showed a significant slower release performance.Moreover,the particle size and Zeta potential of Mt-BH/CS NPs were+30.70 mV and 503 nm,repectively.This very small size with a very large surface area can increase contact area between cornea and drug.Moreover,the relatively high positive charge can have electrostatic interaction with the negatively charged tear film mucin,so that the precorneal retention time may be prolonged,which was conducive to improving the bioavailability of the eye.In order to investigate the safety of the developed novel nano-suspension containing BH,two irritation evaluation methods were used（CAM-TBS and MTT）.Both results showed that the irritation of the novel nano-suspension containing BH and the nano-carrier suspension without BH were lower than that of BH solution.Moreover,the novel nanocarriers without BH had lower irritation than the BH loaded into novel nanocarriers.This indicated that BH solution（raw drug）had strong irritation and the developed carrier was relatively safe.BH loaded into novel nanocarriers may reduce irritation of BH to a certain degree and the novel nano-carrier can be applied to delivery anti-glaucoma drug with the expectation to reduce discomfort of eye and increase patient compliance.Immortalized human corneal epithelial cell model（iHCEC）were established and the stratified structure of cell were formed to simulate human corneal epithelial barrier.The results of cell permeability test showed that the capacity of cell permeability of the Mt-BH/CS NPs(1.124×10^-55 cm·s^-1)was lower than BH solution(1.6795×10^-55 cm·s^-1),indicating that BH contained into the developed novel carrier had a slow sustained release performance,which was conducive to producing sustained IOP reduction and reducing drug side effects.At the same time,cell uptake experiments showed that the novel nanocarrier can be uptaken by iHCEC and located in the cytoplasm,showed that it was conducive to having better efficacy.In vitro pre-corneal retention time experiments showed that the pre-corneal retention time of Mt-BH/CS NPs was one and a half times than BH solution.Tear elimination experiment showed that the BH concentration of Mt-BH/CS NPs can be detected at 240 min and the BH concentration of BH solution can not be detected only at 90 min.Both in vitro and in vivo study suggested Mt-BH/CS NPs could prolong pre-corneal retention time.In addition,the concentration of drug in the blood was investigated and the results showed that the concentration of BH in the blood of Mt-BH/CS NPs was obviously lower than that of BH solution,and the content of BH was very low,indicating that Mt-BH/CS NPs had lower potential systemic side effects caused by the entry of drug into general circulation.The model of acute intraocular pressure（IOP）was induced by water loading method and the results showed Mt-BH/CS NPs could maintain a more stable IOP for 6 h,and the lowering IOP effect was significantly higher than that of BH solution.Therefore,the developed ion exchange nanocarrier（Mt-BH/CS NPs）has potential application in the treatment of glaucoma.