Optical Multisensor Array with Functionalized Photonic Droplets by an Interpenetrating Polymer Network for Human Blood Analysis.

Photonic solid-state cholesteric liquid crystal (CLCsolid) droplets intertwined with a poly(acrylic acid) (PAA) network that has an interpenetrating polymer network (IPN) structure (referred to as photonic IPN CLCsolid-PAA droplets) were used as individual sensors in the dots of a PAA-patterned array film after functionalization via immobilization of the receptors and a metal-ion treatment. The photonic IPN CLCsolid-PAA droplets in the PAA-patterned array film were pH-responsive and showed an observable change in the reflected central color. This "smart" property, coupled with the photonic color response, makes these devices ideal photonic sensors. The immobilization of urease and phenylboronic acid on the PAA network allowed for the application of several 10 μm photonic IPN CLCsolid-PAA droplets to the optical photonic biosensors through facilitated volumetric changes in the PAA network in response to urea and glucose analytes, with high selectivity for major components in human serum, acceptable sensitivity for use with human serum, and extreme stability due to a solid-state structure. The blueshift of the reflected color of the KOH-treated photonic IPN CLCsolid-PAA droplets could be used for divalent metal-ion detection. The compartmentalized photonic IPN CLCsolid-PAA droplets in the patterned array film could be used for multiple detection applications, as evidenced by the ability to conduct pH, divalent metal ion, urea, and glucose detections in one patterned array film. This new platform opens the door for many interesting applications with numerous combinations of responsive hydrogel matrices and receptors.