title: Electrospinning deposition of hydrogel fibers used as scaffold for biomembranes. Thermal stability of DPPC corroborated by ellipsometry.
abstract: DPPC bilayers were deposited over thin hydrogel scaffolds using the Langmuir-Blodgett technique (with DPPC thickness ∼ 6.2 nm). Wrinkled hydrogels films were used to maintain a moist environment in order to enhance DPPC bilayer stability. Polymer mixtures were prepared using HEMA (as a base monomer) and DEGDMA, PEGDA575, PEGDA700 or AAm (as crosslinking agents); a thermal initiator was added to obtain a final pre-hydrogel (oligomer) with an adequate viscosity for thin film formation. This mixture was deposited as wrinkled film/fibers over hydrophilic silicon wafers using an electrospinning technique. Later, these samples were exposed to UV light to trigger photopolymerization, generating crosslinking bonds between hydrogel chains; this process also generated remnant surface stresses in the films that favored wrinkle formation. In the cases where DEGDMA and AAm were used as crosslinking agents, HEMA was added in higher amounts. The resultant polymer film surface showed homogenous layering with some small isolated clusters. If PEGDA575/700 was used as the crosslinking agent, we observed the formation of polymer wrinkled thin films, composed by main and secondary chains (with different dimensions). Moreover, water absorption and release was found to be mediated through surface morphology, ordering and film thickness. The thermal behavior of biomembranes was examined using ellipsometry techniques under controlled heating cycles, allowing phases and phase transitions to be detected through slight thickness variations with respect to temperature. Atomic force microscopy was used to determinate surface roughness changes according to temperature variation, temperature was varied sufficiently for the detection and recording of DPPC phase limits. Contact angle measurements corroborated and quantified system wettability, supporting the theory that wrinkled hydrogel films act to enhance DPPC bilayer stability during thermal cycles.
authors.affiliation: Departamento de Química, Universidad Tecnológica Metropolitana, Las Palmeras #3360, Santiago, Chile. Electronic address: carmenmabel@gmail.com.
authors.forename: C M
authors.initials: CM
authors.lastname: González-Henríquez
authors.affiliation: Instituto de Física, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna #4860, Santiago, Chile.
authors.forename: M A
authors.initials: MA
authors.lastname: Sarabia-Vallejos
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis* / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D013057:Spectrum Analysis; D013696:Temperature; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D020100:Hydrogels; D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine
keywords: DPPC bilayer; Electrospinning and phase transitions; Ellipsometric measurements; Hydrogel films