ABSTRACT
Microfluidics is used here for the first time to efficiently tune the growth conditions for understanding the build-up mechanism of exponentially growing polyelectrolyte (PE) films. The velocity of PE supply and time of interaction can be successfully altered during the layer-by-layer assembly. Another advantage of this method is that the deposition of poly-L-lysine/hyaluronic acid (PLL/HA) films in microchannels can be monitored online by fluorescence microscopy. The study demonstrates that PE mass transport to the film surface and diffusion in the film are key parameters affecting PLL/HA film build-up. Increase of PE supply rate results in a change in the "transition" (exponential-to-linear growth) towards higher number of deposition steps, thus indicating a mass transport-mediated growth mechanism.
Subject(s)
Microfluidics , Electrolytes , Hyaluronic Acid/chemistry , Microscopy, Fluorescence , Polylysine/chemistryABSTRACT
We present here the micropatterns of layer-by-layer (LbL) assembled soft films generated using microfluidic platform that can be exploited for selective cell growth. Using this method, the issue of cell adhesion and spreading on soft LbL-derived films, and simultaneous utilisation of such unmodified soft films to exploit their reservoir properties are addressed. This also paves the way for extending the culture of cells to soft films and other demanding applications like triggered release of biomolecules.
Subject(s)
Fibroblasts/cytology , Hyaluronic Acid/chemistry , Microfluidic Analytical Techniques/instrumentation , Polylysine/chemistry , Tissue Scaffolds/chemistry , Animals , Cell Adhesion , Cell Line , Cell Proliferation , Equipment Design , Mice , Microscopy, Atomic ForceABSTRACT
The control of cell adhesion is crucial in many procedures in cellular biotechnology. A thermo-responsive poly(N-isopropylacrylamide)-poly(ethylene glycol)-thiol (PNIPAAm-PEG-thiol) copolymer was synthesized for the formation of self-assembled monolayers (SAM) that allow the control of adhesion of cells on gold substrates. The contact angle of water on these layers varies between 65 degrees at a temperature of 45 degrees C and 54 degrees at 25 degrees C. This behaviour is consistent with a transition of the polymer chains from an extended and highly hydrated to a collapsed coil-like state. At 37 degrees C, cultivated fibroblasts adhere and spread normally on this surface and detach by reducing the temperature below the lower critical solution temperature (LCST). Layers can repeatedly be used without loss of their functionality. In order to quantify the capability of the copolymer layer to induce cell detachment, defined shear forces are applied to the cells. For this purpose, the laminar flow in a microfluidic device is used. Our approach provides a strategy for the optimization of layer properties that is based on establishing a correlation between a functional parameter and molecular details of the layers.
