Characterization and quantitation of PVP content in a silicone hydrogel contact lens produced by dual-phase polymerization processing.

Polyvinylpyrrolidone (PVP) has been incorporated over the years into numerous hydrogel contact lenses as both a primary matrix component and an internal wetting agent to increase lens wettability. In this study, complementary analytical techniques were used to characterize the PVP wetting agent component of senofilcon A and samfilcon A contact lenses, both in terms of chemical composition and amount present. Photo-differential scanning calorimetry (photo-DSC), gas chromatography with a flame ionization detector (GC-FID), and high-resolution/accurate mass (HR/AM) liquid chromatography-mass spectrometry (LC-MS) techniques confirmed dual phase reaction and curing of the samfilcon A silicone hydrogel material. Gel permeation chromatography (GPC) demonstrated that high molecular weight (HMW) polymer was present in isopropanol (IPA) extracts of both lenses. High-performance liquid chromatography (HPLC) effectively separated hydrophilic PVP from the hydrophobic silicone polymers present in the extracts. Collectively, atmospheric solids analysis probe mass spectrometry (ASAP MS), Fourier transform infrared (FTIR) spectroscopy, 1 H nuclear magnetic resonance (NMR) spectroscopy, GC-FID, and LC-MS analyses of the lens extracts indicated that the majority of NVP is consumed during the second reaction phase of samfilcon A lens polymerization and exists as HMW PVP, similar to the PVP present in senofilcon A. GC-FID analysis of pyrolyzed samfilcon A and senofilcon A indicates fourfold greater PVP in samfilcon A compared with senofilcon A. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1064-1072, 2018.

Visualization of a hyaluronan network on the surface of silicone-hydrogel materials.

Biotrue multipurpose solution (MPS) is a bioinspired disinfecting and conditioning solution that includes hyaluronic acid (HA) as a natural wetting agent. Previous studies demonstrated that HA sorbed from Biotrue MPS on both conventional and silicone hydrogel (SiHy) contact lens materials; an in vitro simulated-wear test validated the presence of HA on the lens surfaces for as long as 20 hours. In this study, the morphology and distribution of HA sorbed from both Biotrue and pure HA solution on SiHy contact lens surfaces was examined. Atomic force microscopy imaging was used to illustrate the topography of fresh SiHy contact lens materials before and after incubation with 0.1% (w/v) HA solution. The distribution, as well as fine details of the HA network, were resolved by first staining HA with Gram's safranin, then imaging with confocal laser-scanning microscopy and differential interference-contrast microscopy. In this approach, SiHy materials take up the dye (safranin) nonspecifically, such that the resultant safranin-HA complex appears dim against the fluorescent lens background. Balafilcon A was chosen as the representative of glassy SiHy lenses that require postpolymerization plasma treatment to increase wettability. Senofilcon A and samfilcon A were chosen as representatives of SiHy materials fabricated with an internal wetting agent. A confluent and dim HA-safranin network was observed adhered to balafilcon A, senofilcon A, and samfilcon A lens surfaces incubated with either 0.1% (w/v) HA solution or Biotrue MPS. Therefore, the conditioning function provided by Biotrue MPS may be in part explained by the presence of the HA humectant layer that readily sorbs on the various types of SiHy contact lens materials.

Optimizing Pin-Printed and Hydrosilylated Microarray Spot Density on Porous Silicon Platforms.

Microarrays of spatially isolated chemistries on planar surfaces are powerful tools. An important factor in microarray technology is the density of chemically unique spots that can be formed per unit area. In this paper, we use contact pin-printing and evaluate how to decrease contact pin-printed spot diameters on porous silicon (pSi) platforms. Using hydrosilylation chemistry to covalently attach chemistries to the pSi surface, the variables studied included pSi porosity and surface polarity, active agent viscosity, and pin diameter. The spot characteristics were assessed by Fourier transform infrared spectroscopy (FT-IR) microscopy and X-ray photoelectron spectroscopy (XPS). Spot size decreased as pSi porosity increased in accordance with molecular kinetic theory and Darcy's law of imbibition. Increasing active agent viscosity and pin diameter (volume of printed agent) led to larger spot diameters in accordance with molecular kinetic theory and Darcy's law. Oxidizing the pSi with H2O2 increased the surface polarity but had no detectable impact on the spot size. This is consistent with formation of an oxide layer atop an unoxidized pSi sublayer.