A novel photonic crystal hydrogel inverse opal fluorescence enhancement platform for highly sensitive immunoassay of tumor markers

Cancer is a significant global health issue, necessitating early detection for effective diagnosis and treatment. We presented a novel method for detecting tumor markers using fluorescence-enhanced photonic crystal hydrogel inverse opal (PC-GELIO) membranes. We efficiently fabricated large-area, low-crack photonic crystal membranes using a homemade microfluidic chip. Composed of PEG-DA and PEG, the hydrogel replicated the photonic crystal structure, yielding photonic crystal hydrogel inverse opal membranes with a unique photonic band gap and inverse opal porous structure. These properties afford the PC-GELIO platform several advantages: Firstly, the high stability of the internal nanostructure in the large-area, low-crack photonic crystals film, prepared using the homemade microfluidic chip, is crucial for preserving the platform's exceptional fluorescence-enhanced sensing capabilities. Secondly, the peak wavelength emitted by fluorescent molecules aligns with the photonic band gap (PBG), significantly enhancing the fluorescence signal through the low-photon effect. Lastly, the high specific surface area provides numerous binding targets for biomolecule modification, and the hydrogel offers a uniform liquid environment conducive to biomolecule binding. We evaluated the fluorescence-enhanced sensing performance of the platform using alpha-fetoprotein (AFP). The limit of quantification (LOQ) for AFP was determined to be as low as 23 pg/mL, representing an order of magnitude improvement compared to non-enhanced platforms (0.29 ng/mL and 0.25 ng/mL). Consequently, this novel fluorescence-enhanced photonic crystal hydrogel inverse opal platform holds significant potential as a straightforward and efficient method for biomolecular detection.