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.

Thermal Response Analysis of Phospholipid Bilayers Using Ellipsometric Techniques

“…Finally, a thickness stabilization at 53.4 °C is observable, pointing that random liquid phase (L α disordered) was reached. The lateral distance between the tails of the phospholipids that form the bilayer increase progressively when the films are heated under controlled cycles [ 14 , 16 , 17 , 24 ]. Studies performed using SPR are concordant with the results obtained by ellipsometry, showing a proportional and highly similar behavior than those plots but with abrupt and sharp steps that are indicative of phase transitions in the phospholipid bilayer.…”

“…For example, Skjevik et al demonstrated that a self-assembled phospholipid structure forms a spontaneous stable lamellar bilayer in few microseconds in an aqueous environment with a clear preferential orientation with polar head groups pointing outside [ 15 ]. However—experimentally—the bilayer packing is related to full water hydration (Van der Waals interactions) through hydrogen bridges [ 14 , 16 , 17 , 18 , 19 ] and lipid interactions [ 20 ]. Recently, Brea et al showed that a reversible chemoselective reaction can be harnessed to achieve non-enzymatic spontaneous remodeling of the phospholipid membrane [ 21 ].…”

Targeting Polymeric Nanobiomaterials as a Platform for Cartilage Tissue Engineering

“…Similarly, cell-adhesive peptides can be bound to surfaces at the nanoscale to regulate chondrogenesis and selectively control cellmatrix interactions [132]. Top-down manufacturing techniques such as nanolithography, and bottom-up techniques such as electrospinning represent the latest advances in nanoengineering, making development of novel constructs increasingly feasible [133][134][135].…”

A Review of Current Regenerative Medicine Strategies that Utilize Nanotechnology to Treat Cartilage Damage

“…Similarly, cell-adhesive peptides can be bound to surfaces at the nanoscale to regulate chondrogenesis and selectively control cell-matrix interactions [ 58 ]. Top-down manufacturing techniques such as nanolithography, and bottom-up techniques such as Electrospinning represent the latest advances in nanoengineering, making development of novel constructs increasingly feasible [ 59 - 61 ].…”