Self-assembled star-shaped chiroplasmonic gold nanoparticles for an ultrasensitive chiro-immunosensor for viruses

Near field optics and optical tunneling light-matter interactions in the superstructure of chiral nanostructures and semiconductor quantum dots exhibit strong optical rotation activity that may open a new window for chiral-based bioanalyte detection. Herein we report an ultrasensitive, chiro-immunosensor using a superstructure of chiral gold nanohybrids (CAu NPs) and quantum dots (QDs). Self-assembly techniques were employed to create asymmetric plasmonic chiral nanostructures to extend the spectral range of the circular dichroism (CD) response to obtain superior plasmonic resonant coupling with the QD excited state; this may help to achieve lower limit of detection (LOD) values. As a result, the designed probe could detect avian influenza A (H5N1) viral concentrations at the picomolar level, a significant improvement in sensitivity in comparison to a non-assembled CAu NP-based chiro-assay. The practicability of the proposed sensing system was successfully demonstrated on several virus cultures, including avian influenza A (H4N6) virus, fowl adenovirus and coronavirus in blood samples. The results of our study highlight that exciton-plasmon interactions change the chirality, and the use of self-assembled nanostructures is an efficient strategy for enhancing the sensitivity of plasmonic nanosensors.