Design and functionalization of responsive hydrogels for photonic crystal biosensors

Photonic crystals embedded in analyte responsive hydrogels provide a powerful platform for biosensing and have benefitted from recent advances in polymer synthesis and functionalization, nanofabrication, and optical characterization. In this review, state-of-the-art techniques for the fabrication and functionalization of photonic crystal hydrogels are presented, along with a fundamental description of how such materials transduce detection of a target analyte into a simple optical readout. Specific biosensing applications using photonic crystal hydrogels are highlighted, including for the detection of DNA hybridization and single-site DNA modifications, enzyme activity, and small molecule metabolites. Moreover, perspectives on using molecular-level interactions to design and engineer more sensitive or more selective biosensors, as well as future directions in this expanding field, are discussed.