DES modified protein-based materials and their use in pharmaceutical applications

This study is the first to investigate the modification of proteins using deep eutectic solvents. The production of plastic materials with suitable properties could then lead to their use in biomedical or pharmaceutical applications. Three polypeptides were used, namely gelatin, zein and soy protein. All of them made plastics when mixed and pressed with the deep eutectic solvent, Glyceline, but all three had very different properties. The material made from gelatin showed variable properties which appeared to depend on how long the two components were mixed for. Conductivity measurements indicate the existence of a continuous phase which may be useful in later applications, particularly for the transdermal drug delivery systems. Composites of gelatin with pharmaceutical DESs (PDES) were then made for oral ingestion. Dissolution rates of three PDESs were measured from a gelatin matrix. When the ingredients were left to mix for an extended time before the pill was pressed, more API could be incorporated compared to tablets pressed straight away showing that the DES was slow to diffuse into the gelatin structure. Lastly, PDES modified gelatin was made into a patch for transdermal drug delivery. It was found that for the small number of compounds tested, drug delivery rates were much higher than those from comparable materials made with the same API in a solid form and not in a PDES. The rate of extraction of the PDES from the patch was dependent on the viscosity of the PDES as might be expected. In conclusion, this study has shown that proteins can be modified with DESs to produce mechanically strong materials with a significant content in an amorphous form. The DESs form pools of liquid within the structure and this can be used to release active pharmaceutical agents either through the stomach or across the skin barrier.