Rapid, point-of-care, visual detection of RBD of SARS-CoV-2 spike protein using an acrylamide-free photonic crystal aptasensor

Abstract

As COVID-19 continues to reemerge with new variants, it has become a persistent challenge to public health, causing disruptions in society and the economy. We report a facile photonic crystal-based aptasensor for the rapid visual detection of the receptor-binding domain (RBD) of the severe acute respiratory syndrome (SARS-CoV-2) spike (S) protein. Monodispersed polystyrene@poly(2-hydroxyethyl methacrylate–acrylic acid) [PS@poly(HEMA–AA)] core–shell microspheres were synthesized to fabricate a stimuli-responsive photonic crystal (RPC). The integration of the RBD target-specific aptamer into the poly(HEMA–AA) hydrogel network facilitated the development of a biosensor that enabled RPCs to selectively bind to the SARS-CoV-2 spike protein using coupling chemistry. The interaction between the RBD and a single-stranded DNA aptamer causes the hydrogel to expand, leading to a color change and a shift in the photonic bandgap (PBG). This phenomenon can be used to detect the RBD of the SARS-CoV-2 spike protein. The addition of the RBD of SARS-CoV-2-S-protein to the Apt-RPC aptasensor resulted in a rapid visual color shift from violet to green. The detection range of the developed aptasensor was estimated to be 100–1000 ng with excellent selectivity. Thus, the developed aptasensor offers distinct advantages over conventional detection methods. Our study also facilitates the development of a straightforward point-of-care self-testing kit that does not rely on toxic acrylamide-based chemicals. Furthermore, the sensor eliminates the need for complex sample preparation or signal amplification steps, making it a promising platform for point-of-care diagnosis.