Investigating the Energetics of Bioadhesion on Microengineered Siloxane Elastomers

Abstract

The energetics of a polydimethylsiloxane (PDMS) elastomer biointerface were micro-engineered through topographical and chemical modification to elicit controlled cellular responses. The PDMS elastomer surfaces were engineered with micrometer scale pillars and ridges on the surface and variable mechanical properties intended to effect directed cell behavior. The topographical features were created by casting the elastomer against epoxy replicas of micropatterned silicon wafers. Using UV photolithography and a reactive ion etching process, highly controlled and repeatable surface microtextures were produced on these wafers. AFM, SEM and white light interference profilometry (WLIP) confirmed the 197 high fidelity of the pattern transfer process from wafer to elastomer. Ridges and pillars 5 μm wide and 1.5 μm or 5 μm tall separated by valleys at 5 μm, 10 μm, or 20 μm widths were examined. Mechanical properties were modulated by addition of linear and branched nonfunctional trimethylsiloxy terminated silicone oils.The modulus of the siloxane elastomer decreased from 1.43 MPa for the unmodified formulation to as low as 0.81 MPa with additives. The oils had no significant effect on the surface energy of the siloxane elastomer as measured by goniometry. Two main biological systems were studied: spores of the green alga Enteromorpha and porcine vascular endothelial cells (PVECs). The density of Enteromorpha spores that settled increased as the valley width decreased. The surface properties of the elastomer were altered by Argon plasma, radio frequency glow discharge (RFGD) treatment, to increase the hydrophilicity for PVEC culture. The endothelial cells formed a confluent layer on the RFGD treated smooth siloxane surface that was interrupted when micro-topography was introduced.

The Antifouling and Fouling-Release Perfomance of Hyperbranched Fluoropolymer (HBFP)−Poly(ethylene glycol) (PEG) Composite Coatings Evaluated by Adsorption of Biomacromolecules and the Green Fouling Alga Ulva

“…Silastic T-2 (Dow-Corning Corporation) was applied to glass slides as described in Hoipkemeier-Wilson et al 42 The modulus of the T2 PDMSE is 1.4 MPa, the water contact angle is typically 109 ( 3.5°, and the calculated surface energy is 23.0 ( 0.4 mN m -2 . 43 Acid-washed glass and cross-linked HBFP-PEG45 coated slides (four replicates of each) were exposed to a suspension of zoospores for 1 h as described above, at a density of 1 × 10 6 mL -1 . After washing, 10 mL of growth medium 44 was added to each dish compartment.…”

“…The fouling-release properties of the most promising test surface (HBFP−PEG45) were compared with a Pt-cured poly(dimethylsiloxane) elastomer (PDMSE) standard using Ulva sporelings (young plants). Silastic T-2 (Dow-Corning Corporation) was applied to glass slides as described in Hoipkemeier-Wilson et al The modulus of the T2 PDMSE is 1.4 MPa, the water contact angle is typically 109 ± 3.5°, and the calculated surface energy is 23.0 ± 0.4 mN m -2 …”

Anti-Biofouling Properties of Comblike Block Copolymers with Amphiphilic Side Chains

“…Acid-washed glass slides and glass slides coated with poly(dimethyl siloxane) were used as standards. The acid-washed glass slides were prepared by washing in Decon detergent before soaking in 1 M hydrochloric acid for 24 h. The PDMS surfaces were prepared using Silastic T-2 (Dow-Corning), as described in Hoipkemeier-Wilson et al , Silastic T-2 was used because of its good dimensional stability, optical transparency, and minimal unknown or nondisclosed additives …”

Engineered Nanoforce Gradients for Inhibition of Settlement (Attachment) of Swimming Algal Spores

“…Micrometer-sized posts of a polydimethylsiloxane elastomer (PDMSe) have previously been modeled as linearly elastic cantilever beams under pure bending . Applying this model, the amount of lateral force required to cause an end deflection of 10% for each topographical feature was estimated (Figure ) using eq 1 where F is the applied force, E is the modulus of elasticity, I is the rectangular moment of area, L is the height of the feature, and y is the end deflection distance . The modulus of elasticity for the particular PDMSe system used in this study is approximately 1.4 MPa .…”