Stimuli-responsive materials can reversibly switch their properties depending on the external stimuli. Take for example, the colour of the skin of the lizard or cuttlefish. During the course of the THREE-S (Smart multi stimuli-responsive supports for controlled cell growth) project, scientists developed multi-stimuli responsive hydrogels using a technique called initiated chemical vapour deposition (iCVD). Hydrogels were selected because they resemble living tissue and can be used in tissue engineering and regeneration applications. A surface polymerisation method, iCVD can be used to deposit thin films of application-specific polymers in a single step in situ and solvent-free. The major advantage of this method is that it allows the fabrication of engineering polymers with specific microscale properties and well-defined macroscale behaviours. THREE-S researchers wanted to reversibly change the mechanical properties of the poly(hydroxyethylmethacrylate) (PHEMA) hydrogel using light and humidity. Hydrogels, as the name suggests, are polymeric materials with varying stiffness that can hold large amounts of water. The idea was to develop suitable supports that permit controlled cell attachment and growth. X-ray scattering and x-ray reflectivity were used for characterisation of structural changes before, during and after irradiation. Project members successfully functionalised the surface of the PHEMA hydrogel with azobenzene and developed a light-responsive hydrogel. Using light irradiation, they achieved precise control over the stiffness and elasticity of the hydrogel by manipulating water uptake. In other words, they reversibly altered the swelling rate and amount of swelling in different types of PHEMA hydrogels using humidity and light irradiation. After the end of this project, THREE-S researchers plan to immobilise cells on the surface of their smart hydrogels and demonstrate cell adhesion and controlled cell growth. Applications in biomedicine are wide ranging including drug delivery, wound dressings and tissue scaffolding.
Biomedicine, hydrogel, THREE-S, initiated chemical vapour deposition, drug delivery