Fast Responsive Crystalline Colloidal Array Photonic Crystal Glucose Sensors

Abstract

We developed new photonic crystal polymerized crystalline colloidal array (PCCA) glucose sensing materials, which operate on the basis of formation of cross-links in the hydrogel. These materials are composed of hydrogels that embed an array of approximately 100-nm-diameter monodisperse polystyrene colloids that Bragg diffract light in the visible spectral region. The hydrogels change volume as the glucose concentration varies. This changes the lattice spacing, which changes the wavelength of the diffracted light. In contrast to our previous glucose sensing photonic crystal materials, we no longer require Na+ chelating agents. These photonic crystal materials are being designed for use in glucose sensing contact lens for people with diabetes mellitus. We describe methods to speed up the response kinetics of these PCCA sensing materials. Rapid-response kinetics is achieved by controlling the elasticity and the hydrophilic-hydrophobic balance of the hydrogel system. A more hydrophobic hydrogel composition is obtained by copolymerizing n-hexylacrylate into an acrylamide-bisacrylamide hydrogel. The response rate significantly increases to where it fully responds within 90 s to the average glucose concentrations found in blood (5 mM) and within 300 s to the average glucose concentrations found in tear fluid (0.15 mM). We find unusual temperature-dependent kinetics, which derive from glucose mutarotation in solution. It is shown that alpha-d-glucose is the glucose anomer binding to the boronic acid derivative. Care must be taken in any glucose determination to ensure that the glucose mutarotation equilibrium has been established. We have demonstrated that the sensor is responsive to approximately 0.15 mM glucose concentrations in artificial tear fluid solution.

Osmotic-pressure-controlled concentration of colloidal particles in thin-shelled capsules

“…Fits for the membrane permeability, k, yield consistent values for various values of C out . The response time of the silicone capsules to osmotic pressure differences is on the order of 10 3 s, comparable to that of colorimetric sensors based on polymerized crystalline colloidal arrays 11 . The response can potentially be improved by using elastic membranes with higher permeability.…”

“…Such dynamic control is especially useful for reflective colour displays, which have been fabricated by embedding colloidal particles in a polymer matrix whose swelling is controlled by an external electric field 6,7 . Dynamic control of diffraction has also be exploited to create colorimetric biosensors that change their structural colour upon specific binding of a biomolecule [8][9][10][11][12][13] . In all of these cases, the modulation of the photonic properties is controlled by changing the interparticle spacing, which requires fluid to flow out from the crystal; this transport is limited by diffusion, and thus rapid response requires small dimensions.…”

DNA-Functionalized Monolithic Hydrogels and Gold Nanoparticles for Colorimetric DNA Detection

“…Other signaling mechanisms such as electrochemical detection have also been demonstrated while few examples of optical sensors are known (25,30,(45)(46)(47)(48)(49). In particular, very few colorimetric sensors have been reported (25,45,50,51). We are interested in making hydrogel-based colorimetric sensors since hydrogels are transparent and can therefore be observed with a low optical background, allowing low concentration of labels to be visually detected.…”

Fabrication of Polymerized Crystalline Colloidal Array Thin Film Modified β-Cyclodextrin Polymer for Paraoxon-ethyl and Parathion-ethyl Detection

“…15 Asher et al have reported the use of polymerized crystalline colloidal array (PCCA) of polystyrene as a novel sensing material for the detection of glucose, organophosphate pesticides and cancer marker with enzyme-based sensors. 16,17 As the PCCA hydrogel undergoes a volume change, the spacing between particles will change, resulting in the shift of reflectance wavelength following Bragg's law. [18][19][20] Since most OP compounds are hydrophobic and exhibit low solubility in water media, on-site detection is indeed difficult.…”