High-precision deposition and controlled release of high molecular weight hyaluronic acid from contact lens surfaces using nanoelectrospray

Abstract

Using additive manufacturing processes to selectively modify soft and wet polymer surfaces, such as soft contact lenses, with micrometer-level precision for applications, including controlled delivery of active ingredients, can be challenging. This study demonstrates the use of a novel nanoelectrospray (nES) process as a technical solution to deposit precise amounts of high molecular weight hyaluronic acid (HA), a highly water-soluble anionic glycosaminoglycan, onto predefined locations on the surface of soft contact lenses, and subsequently release it in a sustained manner. nES allows precise deposition of nano- to micrometer-thick layers outside the central optical zone. To achieve the sustained release of HA from the lens, a chemical modification of the polymer surface was developed to allow the lens surface to be covalently linked with a semi-interpenetrating network (IPN) layer containing entrapped HA after deposition by nES. Additional zein barrier layers applied by nES over the HA layer led to further reduction in the release rate of HA from the lenses. The results confirmed that the selective nES deposition allowed modification of the lens surface without affecting optical properties in the central vision zone of the soft contact lenses. The results suggested that the HA release kinetics can be strongly affected by multiple factors, including the degree of crosslinking, the molecular size of the crosslinker, the addition of a photoinitiator and the polymeric barrier layer. This study demonstrated the potential of nES as an alternative approach for surface modification and drug loading to commercially available contact lenses for treating ocular conditions.