Nanostructure-Based Fluorescent Biosensors

Nanostructure-Based Fluorescent Biosensors Shivaram K. a, Gunnella R. a, Giuliodori A. M.b, Spurio R.b, Fabbretti A. b, Perrozzi F.c Ottaviano L.c aSchool of Science and Technology, Physics Division, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino; e-mail: roberto.gunnella@unicam.it bSchool of Biosciences and Veterinary Medicine, Biology Division, University of Camerino, Via Gentile III da Varano, 62032 Camerino cDipartimento di Scienze Fisiche e Chimiche, Universita' dell'Aquila Via Vetoio, 67100 L'Aquila We have investigated a fluorescent biosensor based on graphene oxide (GO) for the measurement of interaction between a fluorophore FAM (Carboxyfluorescein)-labeled single-stranded DNA with its complementary single-stranded DNA oligonucleotide (target). The graphene oxide adsorbs the FAM-labeled single stranded DNA (probe) and quenches its fluorescence. Upon addition of the complementary single stranded DNA oligonucleotide, the probe hybridizes to its target [1] thus producing a double- stranded DNA, which detaches from the GO. The release of the double helix leads to the recovery of dye fluorescence that can be monitored by fluorimetric techniques. Pristine GO [2,3] flakes were prepared using a modified Hummers method and dispersed in water with a concentration of 0.5 mg/mL. The samples were prepared by drop casting, the GO and DNA with buffered solution [1] on 300 nm SiO2 /Si(100) at room temperature. AFM image of the GO flakes,) shows the typical AFM image of the DNA-GO complex, where the bright areas on the GO surface might be due to the adsorption of DNA. In this complex the thickness is about 3 nm.This observation indicates that GO can strongly adsorb ssDNA and can efficiently quench its fluorescence. The fluorescently labeled ssDNA-GO complex displayed significant fluorescence enhancement upon addition of complementary target DNA oligonucleotide (Figure 1b). This recovery of fluorescence increases with increasing concentration of the target DNA added to the mixture. References 1. Lu, C.-H., Angew. Chem. Int. Ed. 48: 4785–4787 (2009). doi: 10.1002/anie.200901479. 2. Nan-Fu Chiu et al. M. Aliofkhazraei (Ed.), ISBN: 978-953-51-1182-5, InTech (2013). DOI: 10.5772/56221. 3. F. Perrozzi et al., J. Phys.: Condens. Matter 27, 013002 (2015) doi:10.1088/0953-8984/27/1/013002 Graphene oxide: from fundamentals to applications.