Zein-based photonic sensor platform: Application to microRNA detection

Novel zein biopolymer films were formulated for the first time using a combination of glycerol, polydopamine, and shellac, creating sustainable, flexible substrates designed for photonic biosensing. The incorporation of polydopamine improved optical performance by effectively absorbing randomly scattered light, thereby enhancing the photonic crystal signal. Furthermore, the tailored composition contributed to mechanical robustness and plastic-like flexibility, resulting in homogeneous films suitable for photonic structure assembly and point-of-care sensing applications. As a proof-of-concept, the zein film was successfully tested for the detection of microRNAs (miRs). The photonic biosensor targeted miR-21-5p, a key biomarker associated with cancer, demonstrating a broad linear response through reflectance wavelength shifts and visible colorimetric changes. The biosensor provided a linear detection range for miR-21-5p from 10 −14 to 10 −6 mol L −1 , with a limit of detection of 2.2 fmol L −1 . Selectivity was confirmed by testing against miR-26a-5p and a three-base mismatch variant of miR-21-5p. Thus, the integration of a zein-based biopolymer film, the self-reporting capability of photonic crystals, and the high selectivity of oligonucleotide sequences, offers a novel and highly sensitive sensor platform, with potential for detecting miRs circulating in extracellular vesicles as diagnostic biomarkers. • A novel zein-based biopolymer film was developed as a sustainable substrate for assembling photonic biosensors. • Detection of microRNA-21-5p, a key cancer biomarker, was demonstrated through reflectance wavelength shifts and visible colorimetric changes. • Highly sensitive sensor platform with potential for detecting extracellular vesicle-associated microRNAs as diagnostic biomarkers. • The platform shows promise for integration into point-of-care sensing applications.