Reduced graphene-oxide transducers for biosensing applications beyond the Debye-screening limit (original) (raw)
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Talanta, 2019
In this work, we developed an effective voltammetric immunosensing platform for the sensitive detection of prostate specific antigen (PSA) utilizing a graphene oxide (GO) modified screen-printed carbon electrode (SPCE) hybridized with the ex-situ prepared silver nanoparticles (AgNPs) as a probe and signal transducer. The sensing platform comprises a direct-type immunoassay involving the selective interaction of PSA with anti-PSA. The surface morphology and analytical performance of the modified SPCE were characterized through relevant instrumentations. The changes in the voltammetric reduction current of AgNPs at 0.11 V in the sensor electrode was correlated to the PSA concentration. Under optimum conditions, the fabricated immunosensor exhibited a sensitive response to PSA with a limit of detection (LOD) of 0.27 ng mL −1 and a dynamic calibration range of 0.75-100.0 ng mL −1. We demonstrated that the participation of AgNPs along with GO modification contribute to the desired signal amplification and sensitive detection of PSA. It is anticipated that the proposed immunosensor can serve as a biomarker and potentially be utilized for the real sample quantification of PSA.
Scientific Reports
The integration of graphene materials into electrochemical biosensing platforms has gained significant interest in recent years. Bulk quantities of graphene can be synthesized by oxidation of graphite to graphite oxide and subsequent exfoliation to graphene oxide (GO). However, the size of the resultant GO sheets changes from the parent graphite yielding a polydispersed solution of sizes ranging from a few nanometers to tens of micrometers. Here, we investigate the direct effect of GO sheets sizes on biosensor performance. We separated different GO sheets sizes, and we characterized them via atomic force, scanning electron, Raman and X-ray photoelectron spectroscopies and solid state nuclear magnetic resonance (NMR). As proof of concept, the sensing performance of these GO samples was probed using a well-known ssDNA aptasensor against microcystin-LR toxin and an immunosensor against β-lactoglobulin. The resulting aptasensors and immunosensors are fabricated by using covalent attachm...
Scientific reports, 2018
Label-free and sensitive detection of PSA (Prostate Specific Antigen) is still a big challenge in the arena of prostate cancer diagnosis in males. We present a comparative study for label-free PSA aptasensor and PSA immunosensor for the PSA-specific monoclonal antibody, based on graphene quantum dots-gold nanorods (GQDs-AuNRs) modified screen-printed electrodes. GQDs-AuNRs composite has been synthesized and used as an electro-active material, which shows fast electron transfer and catalytic property. Aptamer or anti-PSA has immobilized onto the surface of modified screen printed electrodes. Three techniques are used simultaneously, viz. cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedence spectroscopy (EIS) to investigate the analytical performance of both PSA aptasensor and PSA immunosensor with its corresponding PSA antigen. Under optimum conditions, both sensors show comparable results with an almost same limit of detection (LOD) of 0.14 ng ...
Graphene oxide-based SPR biosensor chip for immunoassay applications
Nanoscale Research Letters, 2014
This work develops a highly sensitive immunoassay sensor for use in graphene oxide sheet (GOS)-based surface plasmon resonance (SPR) chips. This sensing film, which is formed by chemically modifying a GOS surface, has covalent bonds that strongly interact with the bovine serum albumin (BSA), explaining why it has a higher sensitivity. This GOS film-based SPR chip has a BSA concentration detection limit that is 100 times higher than that of the conventional Au-film-based sensor. The affinity constants (K A) on the GOS film-based SPR chip and the conventional SPR chip for 100 μg/ml BSA are 80.82 × 10 6 M −1 and 15.67 × 10 6 M −1 , respectively. Therefore, the affinity constant of the GOS film-based SPR chip is 5.2 times higher than that of the conventional chip. With respect to the protein-protein interaction, the SPR sensor capability to detect angle changes at a low concentration anti-BSA of 75.75 nM on the GOS film-based SPR chip and the conventional SPR chip is 36.1867 and 26.1759 mdeg, respectively. At a high concentration, anti-BSA of 378.78 nM on the GOS film-based SPR chip and the conventional SPR chip reveals two times increases in the SPR angle shift. Above results demonstrate that the GOS film is promising for highly sensitive clinical diagnostic applications.
The application of graphene for in vitro and in vivo electrochemical biosensing
Biosensors & bioelectronics, 2016
Advances in analysis are required for rapid and reliable clinical diagnosis. Graphene is a 2D material that has been extensively used in the development of devices for the medical proposes due to properties such as an elevated surface area and excellent electrical conductivity. On the other hand, architectures have been designed with the incorporation of different biological recognition elements such as antibodies/antigens and DNA probes for the proposition of immunosensors and genosensors. This field presents a great progress in the last few years, which have opened up a wide range of applications. Here, we highlight a rather comprehensive overview of the interesting properties of graphene for in vitro, in vivo, and point-of-care electrochemical biosensing. In the course of the paper, we first introduce graphene, electroanalytical methods (potentiometry, voltammetry, amperometry and electrochemical impedance spectroscopy) followed by an overview of the prospects and possible applic...
Graphene oxide for electrochemical sensing applications
Journal of Materials Chemistry, 2011
By exploiting the presence of abundant carboxylic groups (-COOH) on graphene oxide (GO) and using EDC-NHS (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride-N-hydroxysuccinimide) chemistry to covalently conjugate protein molecules, we demonstrate a novel electrochemical immunosensor for detection of antibody-antigen (Rabbit IgG-AntiRabbit IgG) interactions. The interactions were verified using Electrochemical Impedance Spectroscopy (EIS). Although GO is known to be a poor conductor, the charge transfer resistance (R P ) of a GO modified glassy carbon electrode (GCE) was found to be as low as 1.26 U cm 2 . This value is similar to that obtained for reduced graphene oxide (RGO) or graphene and an order of magnitude less than bare GCE. The EIS monitored antibody-antigen interactions showed a linear increase in R P and the overall impedance of the system with increase of antibody concentration. Rabbit IgG antibodies were detected over a wide range of concentrations from 3.3 nM to 683 nM with the limit of detection (LOD) estimated to be 0.67 nM. The sensor showed high selectivity towards Rabbit IgG antibody as compared to non-complementary myoglobin. RGO modified GCE showed no sensing properties due to the removal of carboxylic groups which prevented subsequent chemical functionalization and immobilization of antigen molecules. The sensitivity and selectivity achievable by this simple label free technique hint at the possibility of GO becoming the electrode material of choice for future electrochemical sensing protocols.
An aptameric graphene nanosensor for label-free detection of small-molecule biomarkers
Biosensors & bioelectronics, 2015
This paper presents an aptameric graphene nanosensor for detection of small-molecule biomarkers. To address difficulties in direct detection of small molecules associated with their low molecular weight and electrical charge, we incorporate an aptamer-based competitive affinity assay in a graphene field effect transistor (FET), and demonstrate the utility of the nanosensor with dehydroepiandrosterone sulfate (DHEA-S), a small-molecule steroid hormone, as the target analyte. In the competitive affinity assay, DHEA-S specifically binds to aptamer molecules pre-hybridized to their complementary DNA anchor molecules immobilized on the graphene surface. This results in the competitive release of the strongly charged aptamer from the DNA anchor and hence a change in electrical properties of the graphene, which can be measured to achieve the detection of DHEA-S. We present experimental data on the label-free, specific and quantitative detection of DHEA-S at clinically appropriate concentra...
Development of a low-cost graphene-based impedance biosensor
2018
for their support and guidance throughout my research work. Overcoming project challenges, I had the chance to develop valuable professional and personal abilities. I am also grateful to the School of Mechanical and Systems Engineering for the awarded PhD scholarship and the given opportunity to work on such an intriguing multidisciplinary project.