Photonic Crystal Carbohydrate Sensors:  Low Ionic Strength Sugar Sensing

Abstract

We developed a carbohydrate sensing material, which consists of a crystalline colloidal array (CCA) incorporated into a polyacrylamide hydrogel (PCCA) with pendent boronic acid groups. The embedded CCA diffracts visible light, and the PCCA diffraction wavelength reports on the hydrogel volume. This boronic acid PCCA responds to species containing vicinal cis diols such as carbohydrates. This PCCA photonic crystal sensing material responds to glucose in low ionic strength aqueous solutions by swelling and red shifting its diffraction as the glucose concentration increases. The hydrogel swelling results from a Donnan potential due to formation of boronate anion; the boronic acid pK(a) decreases upon glucose binding. This sensing material responds to glucose and other sugars at <50 microM concentrations in low ionic strength solutions.

Swelling Properties of Hydrogels Containing Phenylboronic Acids

“…The estimated K s value based on Equation (1) and the swelling curves in Figure 4a is 0.094 mM. This value is different from the literature value [34] for binding of fructose to free ionized PBA, 0.27 mM, but it is consistent with observations made previously with colloidal crystal-embedded hydrogels containing MPBA [8,9]. The slight increase in the plateau swelling at high pH values in the presence of fructose suggests that fructose-bound PBA is slightly more hydrophilic than bare ionized PBA.…”

“…Below pH 8.8, glucose effects an acid shift in swelling as with fructose, but the degree of swelling of hydrogels in glucose solutions is much less than that in fructose solutions at the same pH and the same sugar concentration. This observation is explained by less avid binding of glucose to PBA, compared to fructose [9,20]. Moreover, while increasing fructose concentration always leads to an increase in swelling, increased glucose concentration leads to shrinkage of the hydrogel above pH 8.5.…”

“…Binding can be observed by fluorescence change or by changes in swelling state of a hydrogel in which PBA moieties is incorporated. Several devices have been proposed based on the swelling/shrinking effect, including hydrogels containing colloidal crystal arrays that change color upon swelling and shrinking due to changes in Bragg spacing [7][8][9][10][11], holograms incorporated into hydrogels that also change color [12,13], hydrogel-coated tips of optical fibers that operate as Fabry-Perot interferometers [14,15], and confined, nearly isochoric hydrogels that exert swelling pressure on microfabricated confining structures, with pressure detected either piezoresistively [16][17][18] or electromagnetically [19,20]. Figure 1 shows the simplest mechanism by which PBA responds to sugar molecules [21][22][23][24].…”

Fabrication of Hierarchically Ordered Hybrid Structures over Multiple Length Scales via Direct Etching of Self-Organized Polyhedral Oligomeric Silsesquioxane (POSS) Functionalized Block Copolymer Films

“…Fabrication of nanometer and micrometer scale ordered structures at low cost is an essential objective of a wide range of current science and technology for the miniaturization of electronic, optic 1,2 and magnetic devices, [3][4][5] and sensors [6][7][8][9] etc. Numerous methods such as photolithography 10 or chemical vapor deposition 11 have successfully fabricated a variety of ordered structures over a wide range of length scales, but still require tedious multiple-step processes with high costs.…”

Functionalised ZnO-nanorod-based selective electrochemical sensor for intracellular glucose

“…When glucose levels in the bloodstream are not properly regulated, diseases such as diabetes can develop. Because of the high demand for blood-glucose monitoring, significant research has been devoted to producing reliable methods for in vitro or in vivo glucose measurement, such as fluorescence spectroscopy (Ballerstadt and Schultz, 2000), diffraction spectroscopy (Asher et al, 2003), surface-enhanced Raman scattering (Shafer et al, 2003), a wireless magnetoelastic sensor (Cai et al, 2004), an electrochemical transistor sensor (Forzani et al, 2004;Raffa et al, 2003), an enzyme-based amperometric sensor (Zen et al, 2003;Hrapovic et al, 2004;Lin et al, 2004;Yang et al, 2004;Zhou et al, 2005), a nanoenzymetric amperometric sensor (Park et al, 2003), nuclear magnetic resonance spectroscopy (Cline et al, 1998) and a potentiometric sensor (Shoji et al, 2001). Since the development of the first glucose biosensor, improvement of the response performance of enzyme electrodes has been the main focus of biosensor research (Raitman et al, 2002).…”