Aptasensor Made of Carbon-based Nanostructures for Detecting Spermine

Spermine, a type of polyamine, plays an important role in regulating ion channels, inhibits fat formation, and promotes skeletal development and intestinal maturation. Recently, spermine has been considered as a biomarker for diagnosis of pancreatic cancer. In this paper, an aptasensor made of carbon nanostructures has been developed to quickly and quantitatively detect spermine in aqueous media by using the Forster resonance energy transfer (FRET) quenching technique. Carbon quantum dots (CDs), acting as the FRET donor, have an average diameter of 5.0 +/- 2.5 nm and show the maximum emission intensity (I-max) at 510 nm when the excitation (lambda(ex)) is at 400 nm. The spermine DNA aptamer has been bioconjugated onto the surface of CDs. The I-max of CDs conjugated with the aptamer is decreased significantly after interacting with graphene oxide nanosheets (GO), the FRET quencher, because of the short distance between CDs and GO through coupling with the DNA aptamer. Due to the strong affinity between the DNA aptamer and spermine, the fluorescence intensity of the CDs-based DNA sensor is restored in the presence of spermine. The spermine detection range, 0.2-250 nM, of this DNA sensor made of carbon-based nanostructures, has been analyzed. This study can provide a cost-effective and user-friendly sensing system to quickly detect spermine, a biomarker associated with pancreatic cancer.