Fluorescent Aptasensor for Determination of 8-Oxo-2′-deoxyguanosine in Urine Using Carbon Dots and Amine-Functionalized Gold Nanoparticles

Abstract

8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) is a crucial biomarker of oxidative DNA damage. Herein, a highly sensitive fluorescent aptasensor for detecting 8-oxo-dG in urine was developed based on aptamer-mediated quenching of amino-terminated oligo(ethylene glycol)-capped gold nanoparticles (NH2-TEG-AuNPs) toward green emissive carbon dots (G-CDs). G-CDs were employed as fluorometric reporters. Upon addition of 8-oxo-dG, it formed a complex with an anti-8-oxo-dG aptamer, resulting in the quenching of fluorescence as NH2-TEG-AuNPs absorbed the emission from G-CDs. Initially, NH2-TEG-AuNPs suppressed the fluorescence intensity of G-CDs via the inner-filter effect (IFE). With the addition of the aptamers to a mixture of G-CDs and NH2-TEG-AuNPs, the electrostatic interactions between the aptamer and NH2-TEG-AuNPs resulted in the aggregation of NH2-TEG-AuNPs and the recovery of the fluorescence intensity of the quenched G-CDs. NH2-TEG-AuNPs dispersed due to the high affinity between the aptamer and 8-oxo-dG molecules, and the system demonstrated a fluorescence ″turn-off″ response of G-CDs. Thus, it was possible to determine the 8-oxo-dG concentration. A fluorescence calibration curve was constructed with two linear ranges: 100–2000 and 2000–10,000 nM. The limit of detection (LOD) for 8-oxo-dG was 15.89 nM. This approach was successfully applied to assess 8-oxo-dG in synthetic urine samples with mean recoveries ranging from 99 to 120% and relative standard deviations (RSDs) between 1.1 and 4.1%. The analytical performance was comparable to a commercially available enzyme-linked immunosorbent assay (ELISA) kit. This proposed fluorescent aptasensor for 8-oxo-dG detection in urine exhibited high selectivity and sensitivity over a broad concentration range against the target molecule and has the potential to be developed as a new platform for rapid screening of 8-oxo-dG.

Carbon-dot-triggered aggregation/dispersion of gold nanoparticles for colorimetric detection of nucleic acids and its application in visualization of loop-mediated isothermal amplification

“…1,2 It has been shown that depending on the surface functionalities, CDs are capable of complexing with biomolecules and ions through electrostatic interactions, π–π stacking, hydrogen bonding, and hydrophobic interactions. 3–6 Previous studies have explored this particular avenue to construct CDs-based fluorescent probes for sensitive detection of double-stranded deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and nucleolus imaging. 7–9 For instance, Han et al reported the use of a cationic carbon quantum dot (CQD) probe that emits a distinguishable fluorescence upon binding with DNA and single-stranded RNA in live cells.…”