Designed biointerface using near-infrared quantum dots for ultrasensitive surface plasmon resonance imaging biosensors.

The surface plasmon resonance imaging chip biointerface is fully designed using near-infrared (NIR) quantum dots (QDs) for the enhancement of surface plasmon resonance imaging (SPRi) signals in order to extend their application for medical diagnostics. The measured SPRi detection signal following the QD binding to the surface was amplified 25-fold for a 1 nM concentration of single-stranded DNA (ssDNA) and 50-fold for a 1 μg/mL concentration of prostate-specific antigen (PSA), a cancer biomarker, thus substantiating their wide potential to study interactions of a diverse set of small biomolecules. This significant enhancement is attributed to the QD's mass-loading effect and spontaneous emission coupling with propagating surface plasmons, which allowed the SPRi limit of detection to be reduced to 100 fM and 100 pg/mL for ssDNA and PSA, respectively. Furthermore, this study illustrates the potential of SPRi to be easily integrated with fluorescent imaging for advanced correlative surface-interaction analysis.