title: Thin and ordered hydrogel films deposited through electrospinning technique; a simple and efficient support for organic bilayers.
abstract: Thermal behavior of Dipalmitoylphosphatidylcholine (DPPC) bilayers deposited over hydrogel fibers was examined. Thus, membrane stability, water absorption-release, phase transitions and phase transition temperatures were studied through different methods during heating cycles. Hydrogel films were realized using an oligomer mixture (HEMA-PEGDA575/photo-initiator) with adequate viscosity. Then, the fibers were deposited over silicon wafers (hydrophilic substrate) through electrospinning technique using four different voltages: 15, 20, 25 and 30 kV. The films were then exposed to UV light, favoring polymer chain crosslinking and interactions between hydrogel and substrate. For samples deposited at 20 and 25 kV, hierarchical wrinkle folds were observed at surface level, their arrangement distribution depends directly on thickness and associated point defects. DPPC bilayers were then placed over hydrogel scaffold using Langmuir-Blodgett technique. Field emission scanning electron microscopy (FE-SEM) analysis were used to investigate sample surface, micrographies show homogeneous layer formation with chain polymer order/disorder related to applied voltage during hydrogel deposition process, among other parameters. According to the results obtained, it is possible to conclude that the oligomer deposited at 20 kV produce thin homogenous films (~40 nm) with enhanced ability to absorb water and release it in a controlled way during heating cycles. These scaffold properties confer to DPPC membrane thermal stability, which allow an easy detection of phase(s) and phase transitions. Thermal behavior was also studied via Atomic Force Microscopy (roughness analysis). Contact angle measurements corroborate system wettability, supporting the theory that hydrogel thin films act as DPPC membrane enhancers for thermal stability against external stimuli.
authors.affiliation: Departamento de Química, Universidad Tecnológica Metropolitana, Las Palmeras 3360, Santiago, Chile. Electronic address: carmenmabel@gmail.com.
authors.forename: Carmen M
authors.initials: CM
authors.lastname: González-Henríquez
authors.affiliation: Departamento de Química, Universidad Tecnológica Metropolitana, Las Palmeras 3360, Santiago, Chile.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: del C Pizarro
authors.affiliation: Instituto de Física, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago, Chile.
authors.forename: Mauricio A
authors.initials: MA
authors.lastname: Sarabia-Vallejos
authors.affiliation: Facultad de Química, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago, Chile.
authors.forename: Claudio A
authors.initials: CA
authors.lastname: Terraza
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000327:Adsorption; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis; D004595:Electroplating / Q000379:methods*; D020100:Hydrogels / Q000737:chemistry*; D008051:Lipid Bilayers / Q000138:chemical synthesis*; D008422:Materials Testing; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D012399:Rotation; D012825:Silicon / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D020100:Hydrogels; D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D012825:Silicon
keywords: Biomimetic membrane; DPPC bilayer; Electrospinning; Ellipsometry; Hydrogel wrinkled film; Phospholipid bilayer stability