Effects of Co-Solvents on Loading and Release Properties of Self- Assembled Di-Peptide Building Blocks, Towards Drug Delivery Applications

Abstract

Background: Due to their solid-like porous structure, molecular organogel and microcrystal structures have the capabilities of loading drug molecules, encapsulation, and extended release, all considered as essential properties in drug delivery applications. Phases of these structures, however, depend on the solvent used during the gelation process. Objective: Understanding the phase transition between organogel and microcrystal structures through adjusting the mixture ratio of different co-solvents. Method: Short peptide Diphenylalanine as the gelation building block was used due to its amino acid sequences that can be exactly selected at its molecular levels. Ethanol as a polar solvent was used in combination with four other co-solvents with different polarity levels, namely Xylene, Toluene, Acetone, and Dimethyl Sulfoxide. The morphology of molecular structures of each co-solvent combination at each ratio level was examined as well as the loading and release properties for a non-polar Flufenamic Acid drug. Results: The resultant structure wasaffected by the polarity of the co-solvents; in particular, in the sample containing 25 μg/ml of the drug, 94% of the drug amount was loaded inside the organogel. By increasing the drug concentration to 50, 75, and 100 μg/ml, the loading capability decreased to 76%, 47%, and 33%, respectively. Conclusion: Molecular organogels have excellent capabilities of loading drug molecules, while microcrystal structures have higher release capacity. The findings of this study reveal how to best design a gelation method to obtain maximum loading or release properties for a particular peptide- based drug delivery application.