Silicones have a long history of use in biomedical devices, with unique properties stemming from the siloxane (Si–O–Si) backbone that feature a high degree of flexibility and chemical stability. ...However, surface, rheological, mechanical, and electrical properties of silicones can limit their utility. Successful modification of silicones to address these limitations could lead to superior and new biomedical devices. Toward improving such properties, recent additive strategies have been leveraged to modify biomedical silicones and are highlighted herein.
Flexible, dry skin electrodes represent a potentially superior alternative to standard Ag/AgCl metal electrodes for wearable devices used in long-term monitoring. Herein, such electrodes were formed ...using a facile method for dispersing carbon nanotubes (CNTs) in a silicone matrix using custom amphiphilic dispersive additives (DSPAs). Using only brief mixing and without the use of solvents or surface modification of CNTs, 12 poly(ethylene oxide)-silanes (PEO-SAs) of varying cross-linkability, architecture, siloxane tether length, and molar ratio of siloxane:PEO were combined with an addition cure silicone and CNTs. Nearly all PEO-SA-modified silicone–CNT composites demonstrated improved conductivity compared to the unmodified composite. The best conductivities correlated to composites prepared with PEO-SAs that formed micelles of particular sizes (d of ∼ 200–300 nm) and coincided to PEO-SAs with a siloxane:PEO molar ratio of ∼0.75–3.00. Superior dispersion of CNTs by such PEO-SAs was exemplified by scanning electron microscopy. Advantageously, modified composites retained their moduli, rather than becoming more rigid. Resultant electrodes fabricated with modified composites showed skin-electrode impedance comparable to that of Ag/AgCl electrodes. Combined, these results demonstrate the potential of silicone–CNT composites prepared with PEO-SA DSPAs as flexible, dry electrodes as a superior alternative to traditional electrodes.
Silicone intraocular lenses (IOLs) that resist lens epithelial cell (LEC) growth would greatly improve patient outcomes. Herein, amphiphilic surface modifying additives (SMAs) were incorporated into ...an IOL-type diphenyl silicone to reduce LEC growth without compromising opto-mechanical properties. The SMAs were poly(ethylene oxide)-silane amphiphiles (PEO-SAs) H-Si-ODMS
-
-PEO
-OCH
, comprised of a PEO segment and siloxane tether of varying lengths (
= 0, 13, and 30). These three SMAs were each blended into the addition cure diphenyl silicone at varying concentrations (5, 10, 15, 20, and 25 μmol g
) wherein the wt% of PEO was maintained for all SMAs at a given molar concentration. The chemical crosslinking and subsequent retention of SMAs in modified silicones was confirmed. Key material properties were assessed following equilibration in both air and aqueous environments. Silicones modified with SMAs having longer tethers (
= 13 and 30) underwent rapid and substantial water-driven restructuring of PEO to the surface to form highly hydrophilic surfaces, especially as SMA concentration increased. The % transmittance was also maintained for silicones modified with these particular SMAs. The moduli of the modified silicones were largely unchanged by the SMA and remained in the typical range for silicone IOLs. When the three SMAs were introduced at the highest concentration, modified silicones remained non-cytotoxic and LEC count and associated alpha-smooth muscle actin (α-SMA) expression decreased with increasing tether length. These results demonstrate the potential of silicones modified with PEO-SA SMAs to produce LEC-resistant IOLs.
Amphiphilic gels consisting of acrylamide (AAM)/2-hydroxyethyl methacrylate (HEMA), hexafluorobutyl methacrylate (HFBMA) and non-isocyanate urethane dimethacrylate (NIUDMA) of varying molecular ...weights were compared. A three-level Taguchi analysis was performed using the amount of AAM/HEMA, HFBMA, NIUDMA and reaction time as dependent variables to determine the optimal formulation of the gels with maximized toughness and elastic modulus. The results were compared with commercial AF/FR Intersleek® coatings (IS 700, IS 900 and IS 1100SR) for their antifouling performance against a marine microalga (Navicula incerta), a marine bacterium (Cellulophaga lytica) and adult barnacles (Amphibalanus amphitrite). The toughness, elastic modulus and strain at break of the optimized AAM gels ranged from 3 to7 MPa, 25 to 72 MPa and 80% to 170%, respectively, whereas those of the optimized HEMA gels ranged from 1 to 3 MPa, 13 to 23 MPa and 76% to 160%, respectively. The gels, particularly AHN(E9) and HHN(E12), showed reductions of attachment compared with IS700 of up to 93% and 58%, respectively.
