Formulation and Structural Study of a Biocompatible Water-in-Oil Microemulsion as an Appropriate Enzyme Carrier: The Model Case of Horseradish Peroxidase

A novel biocompatible water-in-oil microemulsion was developed using non-ionic surfactants and was investigated as a potential enzyme delivery system for pharmaceutical applications. The system composed of isopropyl myristate/polysorbate 80 (Tween 80™)/distilled monoglycerides/water/propylene glycol (PG), had a low total surfactant concentration (8.3% w/w) and was able to incorporate approximately 3% w/w aqueous phase containing Horseradish peroxidase (HRP). Structural and activity aspects of the system were studied using a variety of techniques such as Dynamic Light Scattering (DLS), Electron Paramagnetic Resonance (EPR) and Dynamic Interfacial Tension. Apparent hydrodynamic diameter of the empty droplets was calculated at about 37 nm. Different enzyme concentrations, ranging from 0.01-1.39 µM, were used for both DLS and EPR studies in order to effectively determine the localization of the macromolecule in the microemulsion. According to the results, for high enzyme concentrations a participation of HRP ...