Artificial biomembranes stabilized over spin coated hydrogel scaffolds. Crosslinking agent nature induces wrinkled or flat surfaces on the hydrogel

Design and fabrication of biocompatible wrinkled hydrogel films with selective antibiofouling properties

In this article, we explored the selective antibiofouling capacity acquired by functional wrinkled hydrogel films via a fine tuning of their chemical structure through the gradual insertion of hydrophobic radical groups in their network. The hydrogel consists of three main components: hydroxyethyl methacrylate (HEMA, amphiphilic monomer), trifluoroethyl methacrylate (TFMA, hydrophobic monomer), and poly(ethylene glycol) diacrylate (PEGDA, hydrophilic crosslinking agent). Interestingly, the manipulation of the chemical composition affects both, surface morphology and physicochemical characteristics of the patterns, inducing transitions between different surface microstructures, i.e. from wrinkles to creases, to folds, and to crumples. Contact angle measurements show that the insertion of TFMA produces a slight decrease in surface wettability, remaining however highly hydrophilic. By using confocal Raman spectroscopy, important information about wrinkle formation mechanism could be obtained. The procedure presented in this article involves two consecutive thermal and photopolymerization steps, generating a "pseudo" two-layer system, which contracts at different extents when is exposed to external stimuli, leading to the formation of wrinkled surfaces. Finally, bacterial and cellular adhesion/proliferation studies were carried out, evidencing that the amount of TFMA included clearly reduce the bacterial adhesion while mammalian cells are able to still proliferate.

Thermal Response Analysis of Phospholipid Bilayers Using Ellipsometric Techniques

Biomimetic planar artificial membranes have been widely studied due to their multiple applications in several research fields. Their humectation and thermal response are crucial for reaching stability; these characteristics are related to the molecular organization inside the bilayer, which is affected by the aliphatic chain length, saturations, and molecule polarity, among others. Bilayer stability becomes a fundamental factor when technological devices are developed—like biosensors—based on those systems. Thermal studies were performed for different types of phosphatidylcholine (PC) molecules: two pure PC bilayers and four binary PC mixtures. These analyses were carried out through the detection of slight changes in their optical and structural parameters via Ellipsometry and Surface Plasmon Resonance (SPR) techniques. Phospholipid bilayers were prepared by Langmuir-Blodgett technique and deposited over a hydrophilic silicon wafer. Their molecular inclination degree, mobility, and stability of the different phases were detected and analyzed through bilayer thickness changes and their optical phase-amplitude response. Results show that certain binary lipid mixtures—with differences in its aliphatic chain length—present a co-existence of two thermal responses due to non-ideal mixing.