Development of in situ gel containing CUR:HP-β-CD inclusion complex prepared for ocular diseases: Formulation, characterization, anti-inflammatory, antioxidant evaluation and comprehensive release kinetic studies

In this study, cyclodextrin (HP-β-CD) inclusion complexes were prepared with Curcumin (CUR) by cosolvency/lyophilization method. Characterization studies were performed with phase-solubility diagrams, scanning electron microscopy (SEM), FT-IR, FT-Raman, XRD, Differential scanning calorimetry (DSC). The prepared CUR:HP-βCD complexes were evaluated for their anti-oxidant and anti-inflammatory activities compared to free CUR and significantly higher activity was detected with the complexation. In addition, pre-formulation studies have been completed in order to develop an in situ gel formulation, containing CUR:HP-β-CD, suitable for use in ocular diseases. To prepare the in situ forming gels, different Pluronic F127 (PF127) concentrations were used. Chitosan was added to the formulations to improve the gel's mucoadhesive properties. The formulations were evaluated for their viscosity pH, clarity, and sol-gel transition temperature. It was established that the formulations were all clear, their pH was 6, their gelation temperature decreased with increasing PF127, and was between 26-35 °C. Viscosities of all formulations were found to be suitable for ocular application. For the selected formulation, CUR and CUR:HP-β-CD were loaded to in situ gelling systems. In vitro release experiments revealed that the CUR:HP-CD inclusion complex including NSL formulation released for 6 hours with a higher burst effect than the other formulation. At the end of the study, in situ gel formulations containing CUR:HP-β-CD were successfully prepared and characterized comprehensively. In addition, a detailed release kinetic study was conducted for the formulations and it was determined that the CUR release from the in situ gel formulations was compatible with the Weibull model. In conclusion, a mucoadhesive in situ gel formulation containing anti-oxidant and anti-inflammatory CUR:HP-β-CD complex for ocular diseases is presented as an innovative formulation approach. © 2023 Marmara University Press.