Applications of photothermally responsive composite materials
Sershen, Scott Robert
West, Jennifer L.
Doctor of Philosophy
A composite material consisting of a thermally-sensitive hydrogel and optically active nanoparticles would possess the temperature sensitive characteristics of the NA copolymer as well as the absorption spectrum of the nanoshells. The combination of these two properties in a single material opens up several very interesting opportunities in a number of applications. Composite hydrogels consisting of either Au-Au2S or SiO2-Au nanoshells or gold colloid embedded in a N-isopropylacrylamide-co-acrylamide copolymer collapse upon exposure to light that matches the peak extinction wavelength of the nanoparticles. These composite materials have successfully delivered a wide range of molecular weight compounds, from methylene blue (MW 345) to bovine serum albumin (MW 66,000), in a pulsatile fashion in vitro and in vivo. Furthermore, insulin that has been released from the composite hydrogels in this manner retains its activity. Due to the ability of the nanoshell-composite to provide on-demand release of a therapeutic agent, such a system may prove to be beneficial in the treatment of diseases that require a flexible therapeutic regimen, such as insulin dependent diabetes mellitus. The collapse of the composite hydrogels has also been investigated for use as valves or gates in microfluidic devices. Hydrogels containing different nanoparticles exhibit independent optical addressibility, and were polymerized in situ within existing microfluidic chambers. Composite materials of optically active nanoparticles and thermally sensitive hydrogels should prove useful in a wide range of applications where remote optical activation of a mechanical device, such as a gate or switch, is desired, in particular where large relative displacements of such a structure are desirable.