Controlled release of naringenin from soft hydrogel contact lens: An investigation into lens critical properties and in vitro release

The naringenin (NAR)-impregnated hydrogel lenses (nesofilcon A material) were manufactured in this study with the feasibility to achieve controlled daily drug release. The lenses were fabricated using a comparable commercial-standard process, utilizing injection molding and thermal curing approaches. NAR-loaded lenses were prepared by both direct entrapment and ‘soak and release’ methods. Their critical properties were tested to ISO standards and comparable to the commercial lenses. NAR was fully characterized by studying its physical and chemical stability throughout the manufacturing processes using thermal analysis, high performance liquid chromatography and X-ray diffraction analysis. The NAR-loaded lenses showed > 97% light transmission, >75% water content, 0.50–0.53 ± 0.06 MPa tensile strength, with a lens diameter of 14.1 ± 0.1 mm. Lens polymerization kinetics were studied using differential scanning calorimetry. NAR released from the lens, prepared by a direct entrapment approach, followed a diffusion-controlled mechanism, and provided a controlled drug release of 72–82% for 24 h. A faster release rate was observed for NAR-loaded lenses prepared by a soak and release method, with over 90% of NAR was released in the first five hours.