Exploiting Stokes and anti-Stokes type emission profiles of aptamer-functionalized luminescent nanoprobes for multiplex sensing applications

Multiplex biosensing of four types of bacterial food pathogens in one pot is described. Stokes and anti-Stokes type photoluminescence (PL) of two quantum dots (QD) and two upconverting nanoparticles (UCNP) were utilised for realisation of the multiplex detection. The biosensing system was composed of aptamer-functionalized QD and UCNP nanoprobes that were conjugated with partially complementary DNA-modified magnetic beads for separation. PL signals of the conjugates were collected before and after incubation with target pathogens in one pot through the sequential excitations at 335nm for QD probes and 980nm for UCNP probes. The limit of detection values achieved were 28, 15, 12 and 25 cfu center dot mL(-1) for Listeria monocytogenes, Staphylococcus aureus, Salmonella typhimurium and Pseudomonas aeruginosa, respectively. Efforts for extending the multiplex detection up to five pathogens were also presented even though the PL signal cross-talk of a third QD nanoprobe hindered the detection. This work empowers co-deployment of QDs and UCNPs and paves the way for future studies in multiplex sensing, labelling, and bioimaging fields.