Stability of Lysozyme Crystals in Organic Solvents and Monomers

Protein encapsulation and crystallization are under much investigation due to their application in biosensors, drug delivery methods, and filter membrane creation. Encapsulation in hydrogels could provide protein crystals a suitable environment, to maintain their biological stability. However, this process involves the placement of crystals in organic/monomeric media. Therefore, the effects of the organic and monomeric components for polymerization on lysozyme crystals are being studied. Ideal crystallization (through hanging-drop method) conditions were found by varying lysozyme concentration, precipitating agent concentration (sodium chloride; NaCl), and pH of the buffer (acetic acid). The best crystals were observed using a pH of 4.6, NaCl concentration of 3.5M, and lysozyme concentration of 40mg/ml. Afterwards crystal stability was assessed as a function of time and composition of the media. Crystals showed a higher stability in solutions of 30% ethanol and 70% water. This factor was used in the following stability tests in the pre-polymeric solutions using anionic monomer, methacrylic acid (MAA). The tests showed that the crystals had a longer stability in solutions with a crosslinker ratio of 12% and diluted by a factor of 40%. Also being studied is the actual polymerization of the crystals using MAA, and stability of crystals in neutral monomer HEMA.