Kenji Uno

Azulene incorporation and release by hydrogel containing methacrylamide propyltrimenthylammonium chloride, and its application to soft contact lens

We have developed the epoch-making contact lens that is equipped with drug delivery system. The hydrogels contain cationic functional group in its side chain were prepared with 2-hydroxyethyl methacylate (HEMA) and methacrylamide propyltrimethylammonium chloride (MAPTAC). The obtained hydrogel is capable to store the anionic drug such as azulene based on ion-exchange reaction. The incorporated anionic drug would be released in physiological condition. The size change of the hydrogel may occur before and after drug release, but we have discovered that the addition of anionic monomer such as methacrylic acid (MAA) and 2-methacryloxyethyl acid phosphate (MOEP) to the above-mentioned composition is effective to prevent the size change, indicating that this hydrogel has the possibility to be applied as a significant drug delivery system device.

The interaction and compatibility between a soft contact lens and an ophthalmic drug.

Purpose. To investigate the interaction and compatibility between a soft contact lens (SCL) and an ophthalmic drug. Methods. Samples were prepared with the nonionic SCL (groups I and II), the anionic SCL (group IV), and the zwitter ionic SCL (group IV). Chlorpheniramine maleate and sodium cromoglycate were used to measure the drug uptake into the SCL. Results. The results showed the largest drug uptake into the anionic SCL accompanied with dimensional changes and lower drug uptakes into the nonionic and the zwitter ionic SCL with dimensional stability. The cell permeability of the substances when instilled in the eye over the SCL was also measured. The zwitter ionic SCL allowed cell permeability comparable to that by oral administration. Conclusions. These results indicated the possibility for the zwitter ionic SCL as a lens to be worn concomitantly with ophthalmic drug instillation.

The effect of the poly(ethylene glycol) chain on surface exchange of rigid gas-permeable contact lenses.

PURPOSE The SEED Company, Ltd. developed the novel SEED S-1, a rigid gas-permeable contact lens (RGPCL) with a hydrophilic monomer grafted onto its surface by polymerization. This article describes the use of the polymerized graft material poly(ethylene glycol) (PEG) used as a biomaterial, and characterizes the surface of the RGPCL. METHODS The grafting of PEG onto a RGPCL was carried out by plasma treatment and polymerization, and the characteristics of the RGPCL surface were obtained by measuring the water equilibrium contact angle and the surface zeta potential. The zeta potential was measured using an electrophoretic light-scattering photometer. Furthermore, the characteristics of the interaction between the polymer surface and protein was obtained by observing the relationship of adsorption between the protein and lipids and the polymer surfaces. RESULTS The RGPCL became hydrophilic with increasing ethylene glycol units when the graft was polymerized onto the otherwise hydrophobic surface. After the graft polymerization of PEG onto the RGPCL, the surface zeta potentials increased to a negative static surface with the increased addition of ethylene glycol units. Additionally, the amount of adsorption of protein and lipids were decreased, respectively, as the ethylene glycol chain increased in length. CONCLUSIONS The hydrophobic surface of the RGPCL was changed to a hydrophilic surface by graft polymerization of PEG. This suggests that novel RGPCL surfaces can be designed by graft polymerization, using such ethylene glycol groups.