A novel fluorescent aptasensor for sensitive detection of PDGF-BB protein based on a split complementary strand of aptamer and magnetic beads

In this work, a simple and sensitive aptamer-based fluorescent biosensor was fabricated for ultrasensitive detection of platelet-derived growth factor-BB (PDGF-BB) protein, which is known as a potential biomarker for diagnosis of different cancers. The developed aptasensor was based on PDGF-BB aptamer (Apt), a split complementary strand of aptamer (CS), magnetic beads and picogreen (PG) as a sensitive double-stranded DNA (dsDNA) fluorescent dye. Presence of magnetic beads with the capability of sample condensation and split CS in the fabricated biosensor improved the analytical performance of the aptasensor. In the absence of PDGF-BB protein, dsDNA (CS1-CS2/Apt) is formed on the surfaces of magnetic beads. Therefore, after addition of PG to the sample, a strong fluorescence signal is recorded. On the contrary, in the presence of PDGF-BB protein only CS2 as a very short single-stranded DNA (ssDNA) remains on the surfaces of magnetic beads, leading to a weak fluorescence response following the addition of PG. Under optimized condition, the designed biosensor showed a linear response to concentrations of protein from 0.2 to 100 nM with detection limit as low as 0.13 nM. The biosensor was further employed to detect PDGF-BB protein in serum samples and demonstrated satisfied recovery, ranging from 103.6 to 105.2%.