ABSTRACT
By taking advantage of the spectral properties of metal carbonyls, we have designed a surface-enhanced Raman spectroscopy (SERS) ratiometric assay for measuring cell-free circulating DNA (cfDNA) from Epstein-Barr virus in blood for nasopharyngeal carcinoma (NPC). This assay consists of a rhenium carbonyl (Re-CO) to serve as a DNA probe, an osmium carbonyl (Os-CO) embedded within the SERS-active substrate as an internal reference, and a streptavidin layer on the surface of the substrate. Hybridization of cfDNA with biotinylated-capture sequence leads to immobilization of cfDNA on the substrate. The binding of Re-CO via daunorubicin (DNR) to cfDNA is accompanied by an appearance of a strong symmetry stretching vibrations peak at 2113 cm-1, which has spectral overlap with Os-CO (2025 cm-1). This results in an increase in the I2113/ I2025 ratio and quantitatively correlates with cfDNA. This SERS assay can be readily used to detect cfDNA in blood samples from patients due to the intensity ratio of I2113/ I2025 lying in a silent region (1780-2200 cm-1) in the SERS spectrum of the biomolecules.
Subject(s)
Carbon Monoxide/chemistry , Cell-Free Nucleic Acids/blood , DNA, Viral/blood , Herpesvirus 4, Human/genetics , Osmium/chemistry , Rhenium/chemistry , Cell-Free Nucleic Acids/genetics , DNA, Viral/genetics , Herpesvirus 4, Human/isolation & purification , Humans , Real-Time Polymerase Chain Reaction , Spectrum Analysis, Raman , Surface PropertiesABSTRACT
Here, we propose a highly sensitive and rapid bio-sensor for the detection of bio-markers for stroke and cancer-related diseases, based on the utilization of the adsorption properties of ruthenium carbonyl (Ru-CO) clusters on monolayer graphene (MG). A fast rate of decarbonylation of Ru-CO to form ruthenium oxide nanoparticles (RuO2 NPs) on MG was observed. The quantitative detection of matrix metalloproteinase-2 (MMP-2) (bio-marker for stroke and vascular diseases) was demonstrated by tracking the spectral shift of the characteristic G band of graphene caused by the adsorption of RuO2 NPs. A concentration as low as 17 ng mL-1 of MMP-2 was detected in a simulated clinical serum sample. This effective bio-sensor has the potential to revolutionize the biomedical field in the early detection and possible prevention of stroke and cancer diagnosis.
