Controlled drug delivery for glaucoma therapy using montmorillonite/Eudragit microspheres as an ion-exchange carrier

Shuangyan Tian,1 Juan Li,1 Qi Tao,2,3 Yawen Zhao,1 Zhufen Lv,4 Fan Yang,1 Haoyun Duan,5 Yanzhong Chen,4 Qingjun Zhou,5 Dongzhi Hou1 1Guangdong Engineering and Technology Research Center of Topical Precise Drug Delivery System, College of Pharmacy, Department of Pharmaceutics, Guangdong Pharmaceutical University, 2CAS Key Laboratory of Mineralogy and Metallogeny, 3Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 4Guangdong Provincial Key Laboratory of Advanced Drug Delivery Systems, Guangdong Pharmaceutical University, Guangzhou, 5State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong Academy of Medical Sciences, Qingdao, China Background: Glaucoma is a serious eye disease that can lead to loss of vision. Unfortunately, effective treatments are limited by poor bioavailability of antiglaucoma medicine due to short residence time on the preocular surface. Materials and methods: To solve this, we successfully prepared novel controlled-release ion-exchange microparticles to deliver betaxolol hydrochloride (BH). Montmorillonite/BH complex (Mt-BH) was prepared by acidification-intercalation, and this complex was encapsulated in microspheres (Mt-BH encapsulated microspheres [BMEMs]) by oil-in-oil emulsion–solvent evaporation method. The BH loaded into ion-exchange Mt was 47.45%±0.54%. After the encapsulation of Mt-BH into Eudragit microspheres, the encapsulation efficiency of BH into Eudragit microspheres was 94.35%±1.01% and BH loaded into Eudragit microspheres was 14.31%±0.47%. Results: Both Fourier transform infrared spectra and X-ray diffraction patterns indicated that BH was successfully intercalated into acid-Mt to form Mt-BH and then Mt-BH was encapsulated into Eudragit microspheres to obtain BMEMs. Interestingly, in vitro release duration of the prepared BMEMs was extended to 12 hours, which is longer than both of the BH solution (2.5 hours) and the conventional BH microspheres (5 hours). Moreover, BMEM exhibited lower toxicity than that of BH solution as shown by the results of cytotoxicity tests, chorioallantoic membrane-trypan blue staining, and Draize rabbit eye test. In addition, both in vivo and in vitro preocular retention capacity study of BMEMs showed a prolonged retention time. The pharmacodynamics showed that BMEMs could extend the drug duration of action. Conclusion: The developed BMEMs have the potential to be further applied as ocular drug delivery systems for the treatment of glaucoma. Keywords: glaucoma, montmorillonite, controlled release, betaxolol hydrochloride, preocular retention, microsphere