HYDROGEL NANOCOMPOSITE SENSORS WITH COLORIMETRIC RESPONSE UPON PROTEIN EXPOSURE
Leopoldo Torres Jr., Omar Ayyub, Peter Kofinas.
University of Maryland, College Park, College Park, MD.
The detection of pathogens is of utmost importance for the prevention of infection in health care facilities. Current technologies designed to achieve this purpose require expensive machinery, technical training, and sample preparation which can be costly. Developing materials that can produce a visible colorimetric response would prove to be cost effective by eliminating the need for machinery and technical personnel. Photonic crystals (PCs) have the potential for biosensing due to their color-producing nanostructures. PCs have been investigated for such applications, with sensors responding to low concentrations of chemicals, proteins, and other stimuli such as pH change and strain. In 3D photonic crystal hydrogel nanocomposites, the stimulus induces a swelling or deswelling event that alters the distance between nanoparticles, thus changing the wavelength of reflectance. However, very few photonic crystal sensors can produce a visible color shift. Our group recently developed a photonic crystal with highly charged silica nanoparticles that produced a color shift (~240 nm) from red to blue upon exposure to chymotrypsin. The hydrogel nanocomposite was designed so that the enzyme would encounter a dicystine peptide in the polymer network and disrupt the crosslinks. This frees charged particles and allows them to become closer in proximity. Additionally, the storage modulus increased by 1500% through the remodification of the network crosslinks. Here, we exploit the limits of this mechanism by comparing photonic crystal sensors with varying particle sizes to observe the effects on reflectance wavelength, storage modulus, and time for transition.