Improved oxygen permeability and mechanical strength of silicone hydrogels with interpenetrating network structure

The Ophthalmic Performance of Hydrogel Contact Lenses Loaded with Silicone Nanoparticles

In this study, silicone nanoparticles (SiNPs) were prepared from polydimethylsiloxane (PDMS) and tetraethyl orthosilicate (TEOS) via the sol-gel process. The resultant SiNPs were characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and scanning electron microscope (SEM). These SiNPs were then blended with 2-hydroxyethylmethacrylate (HEMA) and 1-vinyl-2-pyrrolidinone (NVP) before polymerizing into hydrogel contact lenses. All hydrogels were subject to characterization, including equilibrium water content (EWC), contact angle, and oxygen permeability (Dk). The average diameter of SiNPs was 330 nm. The results indicated that, with the increase of SiNPs content, the oxygen permeability increased, while the EWC was affected insignificantly. The maximum oxygen permeability attained was 71 barrer for HEMA-NVP lens containing 1.2 wt% of SiNPs with an EWC of 73%. These results demonstrate that by loading a small amount of SiNPs, the Dk of conventional hydrogel lenses can be improved greatly. This approach would be a new method to produce oxygen-permeable contact lenses.

Preparation, material properties and antimicrobial efficacy of silicone hydrogel by modulating silicone and hydrophilic monomer

The present work proposes to investigate two series of silicone hydrogel materials for their characterization, water content, surface wettability, transmittance, mechanical property, oxygen permeability (Dk), and bacterial attachment as potential contact lens materials and discuss the relationships between water affinity and optical, mechanical, oxygen permeable and biological properties. One of the series of silicone hydrogels is presented on the basis of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane (TRIS), 3-(3-methacryloxy-2-hydroxypropoxy)propylbis(trimethylsiloxy)methylsilane (BIS) and 2-hydroxyethyl methacrylate (HEMA) with different silicone monomers/HEMA ratios. The other is presented on the basis of TRIS, BIS, HEMA and N,N-dimethylacrylamide (DMA) with different DMA/HEMA ratios. The results showed that the water affinity could be modulated by the hydrophilic methacrylate. The equilibrium water content (EWC) increased and the water static contact angle (WCA) value decreased with the increase of hydrophilic monomers. Overall, the results demonstrated that visible light transmittance tends to increase and tensile mechanical properties presented in declining trend depending on the increasing EWC. The Dk value decreased first and then increased when the EWC was from 20 to 60%. The reversion point of EWC was about 42.5% The amount of Staphylococcus aureus attached on the surface of the silicone hydrogels was dropped from 10⁴ to 10³ while the WCA was at 55^°. This work may provide information on preparing functional silicone hydrogels for contact lenses application.

Effect of crosslinking concentration on properties of 3-(trimethoxysilyl) propyl methacrylate/N-vinyl pyrrolidone gels

BACKGROUND

The incorporation of two different monomers, having different properties, in the same polymer molecule leads to the formation of new materials with great scientific and commercial importance. The basic requirements for polymeric materials in some areas of biomedical applications are that they are hydrophilic, having good mechanical and thermal properties, soft, and oxygen-permeable.

RESULTS

A series of 3-(trimethoxysilyl) propyl methacrylate/N-vinyl pyrrolidone (TMSPM/NVP) xerogels containing different concentration of ethylene glycol dimethacrylate (EGDMA) as crosslinking agent were prepared by bulk polymerization to high conversion using BPO as initiator. The copolymers were characterized by FTIR. The corresponding hydrogels were obtained by swelling the xerogels in deionized water to equilibrium. Addition of EGDMA increases the transparency of xerogels and hydrogels. The minimum amount of EGDMA required to produce a transparent xerogel is 1%. All the Swelling parameters, including water content (EWC), volume fraction of polymer (ϕ₂) and weight loss during swelling decrease with increasing EGDMA. Young's and shear modulus (E and G) increase as EGDMA increases. The hydrogels were characterized in terms of modulus cross-linking density (v _e and v _t ) and polymer-solvent interaction parameters (χ). Thermal properties include TGA and glass transition temperature (T_g) enhance by adding EGDMA whereas the oxygen permeability (P) of hydrogels decreases as water content decrease.

CONCLUSIONS

This study prepared and studied the properties for new copolymer (TMSPM-co-NVP) contains different amounts of (EGDMA). These copolymers possess new properties with potential use in different biomedical applications. The properties of the prepared hydrogels are fit with the standard properties of materials which should be used for contact lenses.

Robust and self-healable nanocomposite physical hydrogel facilitated by the synergy of ternary crosslinking points in a single network

A single network physical gel hierarchically crosslinked by hydrogen bonds, hydrophobic interactions and nanoparticles exhibits great mechanical performance.