Studies on Development of Polymeric Materials Using Gamma Irradiation for Contact and Intraocular Lenses

Abstract

For the development of materials for contact lenses and intraocular lenses, the selection criteria is based on the (i) capacity to absorb and retain water, (ii) hydrophilicity and hydrophobicity, (iii) refractive index and (iv) hardness besides the other essential properties. Various monomers are being studied to develop suitable materials for such applications. Selection of suitable monomers that can be converted into optical materials of desired characteristics is the most essential step. In the present paper, an attempt has been made to develop suitable optical polymers based on 2-hydroxy ethyl methacrylate (HEMA), N-vinyl pyrrolidone (NVP), methyl methacrylate (MMA), methacrylic acid (MAA), and styrene. Compositions were prepared in such a way that polymers of varying hydrophilicity or hydrophobicity could be obtained keeping HEMA as the base (main) monomer. For polymerization, gamma irradiation (Co-60 as a source) was used. The results of the study showed that: (i) an increase in NVP and MAA content brought in an increase in hydrophilicity of polymerized HEMA (pHEMA), while the addition of styrene and MMA decreased hydrophilicity of polymerized HEMA (pHEMA), (ii) polymers for contact lenses with water retention capacity as high as >50 wt.% and as low as <10 wt% with varying content of suitable comonomers can be designed, (iii) polymeric materials for contact lenses can be made by using radiation processing such as Co-60 and (iv) a dose of 40 kGy was found to be ideal for purpose.

Advances in chemistry and composition of soft materials for drug releasing contact lenses

“…With increasing concentration of NVP the refractive index of the contact lens increases due to the high molar refraction of the pyrrolidone ring of NVP. 41 The copolymer of HEMA and NVP also showed no variation in the mechanical properties and the visibility of the lens.…”

“…Due to low molar refractions of MAA and MMA the refractive index of the contact lens decreases with their increasing concentrations in their respective copolymers. 41 NVP has the highest hydrophilicity among the four comonomers used. The presence of the bipolar lactam group makes it highly polar thereby inducing hydrophilicity.…”

“…Incorporation of NVP (N-vinyl pyrrolidone), MMA (methyl methacrylate), MAA (methacrylic acid), styrene into the polymeric network of pHEMA with varying ratios inuences the physicochemical properties of the contact lens. [41][42][43][44][45] Among the four co-monomers used, styrene is most hydrophobic in nature. The presence of aromatic rings makes styrene hydrophobic as compared to the other monomers used in the study.…”

“…The presence of aromatic rings makes styrene hydrophobic as compared to the other monomers used in the study. 41 Thus, when incorporated into pHEMA, it leads to loss of water retention capacity. With increasing concentration of styrene, the refractive index of the lens increases due to the high molar refraction of the phenyl ring present in styrene.…”

Antimicrobial Hydrogel Contact Lens Containing Alginate

“…Co-polymerization of 2-hydroxyethyl methacylate (HEMA) with monomers capable of establishing specific ionic or hydrophilic interactions with the drug molecules has been widely used to improve the release or loading behavior. [11][12][13] For instance, the hydrogels containing the comonomers methacrylic acid (MAA) or NVP (N-vinyl pyrrolidone) has been shown to be capable for a large amount of water. [14][15][16][17] The HEMA that has been copolymerized with anionic monomers such as MAA to introduce charged moieties in the polymeric network was found to improve the biological performance of the material.…”