Integration of a Chemical‐Responsive Hydrogel into a Porous Silicon Photonic Sensor for Visual Colorimetric Readout

Abstract

The incorporation of a chemo-responsive hydrogel into a 1D photonic porous silicon (PSi) transducer is demonstrated. A versatile hydrogel backbone is designed via the synthesis of an amine-functionalized polyacrylamide copolymer where further amine-specific biochemical reactions can enable control of cross-links between copolymer chains based on complementary target–probe systems. As an initial demonstration, the incorporation of disulfide chemistry to control cross-linking of this hydrogel system within a PSi Bragg mirror sensor is reported. Direct optical monitoring of a characteristic peak in the white light reflectivity spectrum of the incorporated PSi Bragg mirror facilitates real-time detection of the hydrogel dissolution in response to the target analyte (reducing agent) over a timescale of minutes. The hybrid sensor response characteristics are shown to systematically depend on hydrogel cross-linking density and applied target analyte concentration. Additionally, effects due to responsive hydrogel confinement in a porous template are shown to depend on pore size and architecture of the PSi transducer substrate. Sufficient copolymer and water is removed from the PSi transducer upon dissolution and drying of the hydrogel to induce color changes that can be detected by the unaided eye. This highlights the potential for future development for point-of-care diagnostic biosensing.

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.…”

Photonic Crystal Sensors Based on Porous Silicon

“…Gao et al , transferred this concept to hydrophilic proteins [56]. Further development of porous silicon 1D photonic crystal sensors for visual colorimetric readout was reported by Bonanno and De Louise in 2010 [57]. Here, the integration of a stimuli-responsive hydrogel into the porous structure whose cross-linking densities is controlled by interactions with the analyte is the key to achieve direct optical detection.…”

Covalent tethering of photo-responsive superficial layers on hydrogel surfaces for photo-controlled release

“…12 Light and temperature are contact free and environmentally friendly stimuli, which make them the most commonly used to trigger substance release from hydrogels. Conventionally, the most straightforward method to obtain a stimuli-responsive hydrogel is the chemical modification of a hydrogel with stimuli-responsive moieties in its building blocks or use of a stimuli-responsive polymer to construct its network.…”