A novel and sensitive electrochemical DNA biosensor based on Fe@Au nanoparticles decorated graphene oxide

Recent advances in graphene-based biosensor technology with applications in life sciences

Graphene's unique physical structure, as well as its chemical and electrical properties, make it ideal for use in sensor technologies. In the past years, novel sensing platforms have been proposed with pristine and modified graphene with nanoparticles and polymers. Several of these platforms were used to immobilize biomolecules, such as antibodies, DNA, and enzymes to create highly sensitive and selective biosensors. Strategies to attach these biomolecules onto the surface of graphene have been employed based on its chemical composition. These methods include covalent bonding, such as the coupling of the biomolecules via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide reactions, and physisorption. In the literature, several detection methods are employed; however, the most common is electrochemical. The main reason for researchers to use this detection approach is because this method is simple, rapid and presents good sensitivity. These biosensors can be particularly useful in life sciences and medicine since in clinical practice, biosensors with high sensitivity and specificity can significantly enhance patient care, early diagnosis of diseases and pathogen detection. In this review, we will present the research conducted with antibodies, DNA molecules and, enzymes to develop biosensors that use graphene and its derivatives as scaffolds to produce effective biosensors able to detect and identify a variety of diseases, pathogens, and biomolecules linked to diseases.

Top-down fabrication of shape-controlled, monodisperse nanoparticles for biomedical applications

Nanoparticles for biomedical applications are generally formed by bottom-up approaches such as self-assembly, emulsification and precipitation. But these methods usually have critical limitations in fabrication of nanoparticles with controllable morphologies and monodispersed size. Compared with bottom-up methods, top-down nanofabrication techniques offer advantages of high fidelity and high controllability. This review focuses on top-down nanofabrication techniques for engineering particles along with their biomedical applications. We present several commonly used top-down nanofabrication techniques that have the potential to fabricate nanoparticles, including photolithography, interference lithography, electron beam lithography, mold-based lithography (nanoimprint lithography and soft lithography), nanostencil lithography, and nanosphere lithography. Varieties of current and emerging applications are also covered: (i) targeting, (ii) drug and gene delivery, (iii) imaging, and (iv) therapy. Finally, a future perspective of the nanoparticles fabricated by the top-down techniques in biomedicine is also addressed.

Fabrication of novel electrochemical sensors based on modification with different polymorphs of MnO2 nanoparticles. Application to furosemide analysis in pharmaceutical and urine samples

A novel MnO2 nanoparticles/chitosan-modified pencil graphite electrode (MnO2 NPs/CS/PGE) was constructed using two different MnO2 polymorphs (γ-MnO2 and ε-MnO2 nanoparticles). X-ray single phases of these two polymorphs were obtained by the comproportionation reaction between MnCl2 and KMnO4 (molar ratio of 5 : 1). The temperature of this reaction is the key factor governing the formation of the two polymorphs. Their structures were confirmed by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) analysis. Scanning electron microscopy (SEM) was employed to investigate the morphological shape of MnO2 NPs and the surface of the bare and modified electrodes. Moreover, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for surface analysis of the modified electrodes. Compared to bare PGE, MnO2 NPs/CS/PGE shows higher effective surface area and excellent electrocatalytic activity towards the oxidation of the standard K3[Fe(CN)6]. The influence of different suspending solvents on the electrocatalytic activity of MnO2 was studied in detail. It was found that tetrahydrofuran (THF) is the optimum suspending solvent regarding the peak current signal and electrode kinetics. The results reveal that the modified γ-MnO2/CS/PGE is the most sensitive one compared to the other modified electrodes under investigation. The modified γ-MnO2/CS/PGE was applied for selective and sensitive determination of FUR. Under the optimized experimental conditions, γ-MnO2/CS/PGE provides a linear response over the concentration range of 0.05 to 4.20 μmol L-1 FUR with a low limit of detection, which was found to be 4.44 nmol L-1 (1.47 ng mL-1) for the 1st peak and 3.88 nmol L-1 (1.28 ng mL-1) for the 2nd one. The fabricated sensor exhibits a good reproducibility and selectivity and was applied successfully for the determination of FUR in its dosage forms and in spiked urine samples with good accuracy and precision.

Detection of chikungunya virus DNA using two-dimensional MoS2 nanosheets based disposable biosensor

Development of platforms for a reliable, rapid, sensitive and selective detection of chikungunya virus (CHIGV) is the need of the hour in developing countries. To the best of our knowledge, there are no reports available for the electrochemical detection of CHIGVDNA. Therefore, we aim at developing a biosensor based on molybdenum disulphide nanosheets (MoS₂ NSs) for the point-of-care diagnosis of CHIGV. Briefly, MoS₂ NSs were synthesized by chemical route and characterized using scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopy, Raman spectroscopy and X-Ray Diffraction. MoS₂ NSs were then subjected to physical adsorption onto the screen printed gold electrodes (SPGEs) and then employed for the detection of CHIGV DNA using electrochemical voltammetric techniques. Herein, the role of MoS₂ NSs is to provide biocompatibility to the biological recognition element on the surface of the screen printed electrodes. The detection strategy employed herein is the ability of methylene blue to interact differentially with the guanine bases of the single and double-stranded DNA which leads to change in the magnitude of the voltammetric signal. The proposed genosensor exhibited a wide linear range of 0.1 nM to 100 µM towards the chikungunya virus DNA.

Exploration of two-dimensional bio-functionalized phosphorene nanosheets (black phosphorous) for label free haptoglobin electro-immunosensing applications

We report on the development of an antibody-functionalized interface based on electrochemically active liquid-exfoliated two-dimensional phosphorene (Ph) nanosheets-also known as black phosphorous nanosheets-for the label-free electrochemical immunosensing of a haptoglobin (Hp) biomarker, a clinical marker of severe inflammation. The electrodeposition has been achieved over the screen-printed electrode (SPE) using liquid-assisted ultrasonically exfoliated black phosphorus nanosheets. Subsequently, Ph-SPEs bioconjugated with Hp antibodies (Ab), using electrostatic interactions via a poly-L-lysine linker for biointerface development. Electrochemical analysis demonstrates that the Ab-modified Ph-SPEs (Ab@Ph-SPE) exhibit enhanced electroconducting behavior as compared to the pristine electrodes. This Ab-functionalized phosphorene-based electrochemical immunosensor platform has demonstrated remarkable sensitivity and specificity, having a dynamic linear response range from 0.01-10 mg ml-1 for Hp in standard and serum samples with a low detection limit (∼0.011 mg ml-1) using the label-free electrochemical technique. The sensor electrodes were also studied with other closely relative interferents to investigate cross reactivity and specificity. This strategy opens up avenues to POC (point-of-care) and on-farm livestock disease monitoring technologies for multiplexed diagnosis in complex biological samples such as serum. The technique is simple in fabrication and provides an analytical response in less than 60 s.

Electrochemical detection of sequence-specific DNA based on formation of G-quadruplex-hemin through continuous hybridization chain reaction

A high-sensitive detection of sequence-specific DNA was established based on the formation of G-quadruplex-hemin complex through continuous hybridization chain reaction (HCR). Taking HIV DNA sequence as an example, a capture probe complementary to part of HIV DNA was firstly self-assembled onto the surface of Au electrode. Then a specially designed assistant probe with both terminals complementary to the target DNA and a G-quadruplex-forming sequence in the center was introduced into the detection solution. In the presence of both the target DNA and the assistant probe, the target DNA can be captured on the electrode surface and then a continuous HCR can be conducted due to the mutual recognition of the target DNA and the assistant probe, leading to the formation of a large number of G-quadruplex on the electrode surface. With the help of hemin, a pronounced electrochemical signal can be observed in differential pulse voltammetry (DPV), due to the formation of G-quadruplex-hemin complex. The peak current is linearly related with the logarithm of the concentration of the target DNA in the range from 10 fM to 10 pM. The electrochemical sensor has high selectivity to clearly discriminate single-base mismatched and three-base mismatched sequences from the original HIV DNA sequence. Moreover, the established DNA sensor was challenged by detection of HIV DNA in human serum samples, which showed the low detection limit of 6.3 fM. Thus it has great application prospect in the field of clinical diagnosis and environmental monitoring.

Simultaneous extraction and determination of trace amounts of diclofenac from whole blood using supported liquid membrane microextraction and fast Fourier transform voltammetry

A novel, simple, and inexpensive analytical technique based on flat sheet supported liquid membrane microextraction coupled with fast Fourier transform stripping cyclic voltammetry on a reduced graphene oxide carbon paste electrode was used for the extraction and online determination of diclofenac in whole blood. First, diclofenac was extracted from blood samples using a polytetrafluoroethylene membrane impregnated with 1-octanol and then into an acceptor solution, subsequently it was oxidized on a carbon paste electrode modified with reduced graphene oxide nanosheets. The optimal values of the key parameters influencing the method were as follows: scan rate, 6 V/s; stripping potential, 200 mV; stripping time, 5 s; pH of the sample solution, 5; pH of the acceptor solution,7; and extraction time, 240 min. The calibration curves were plotted for the whole blood samples and the method was found to have a good linearity within the range of 1-25 μg/mL with a determination coefficient of 0.99. The limits of detection and quantification were 0.1 and 1.0 μg/mL, respectively. Using this coupled method, the extraction and determination were merged into one step. Accordingly, the speed of detection for sensitive determination of diclofenac in complex samples, such as blood, increased considerably.

An electrodeposited molecularly imprinted quartz crystal microbalance sensor sensitized with AuNPs and rGO material for highly selective and sensitive detection of amantadine

In the present work, a new amantadine (AM) imprinted quartz crystal microbalance (QCM) sensor sensitized by Au nanoparticles (AuNPs) and reduced graphene oxide (rGO) material was fabricated by electrodeposition in the presence of o-aminothiophenol (o-AT) by cyclic voltammetry scanning. AuNPs and graphene, with the advantages of great chemical stability, electrical conductivity, and large surface area, show exceptionally high sensitivity. The results of different modifications of the QCM sensor fabrication process were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. Under the optimal experimental conditions, the frequency shift of the MIP-QCM sensor showed a linear relationship with the concentration of the AM template in the range of 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mmol L⁻¹ with a limit of detection (LOD) of 5.40 × 10⁻⁶ mmol L⁻¹. The imprinting factor for AM reached 7.1, the selectivity coefficient for the analogues rimantadine (RT), adamantine (AMT) and 1-chloroadamantane (CMT) were 7.3, 5.6, and 6.1, respectively. Here, a highly sensitive, selective and stable QCM sensor prepared via the imprinting approach is reported for the first time for detection of AM from animal-derived food samples.

In the present work, a new amantadine imprinted quartz crystal microbalance sensor sensitized by Au nanoparticles and reduced graphene oxide material was fabricated by electrodeposition of o-aminothiophenol by cyclic voltammetry scanning.

An amplified platform nanostructure sensor for the analysis of epirubicin in the presence of topotecan as two important chemotherapy drugs for breast cancer therapy

Epirubicin (EB) and topotecan (TP) are two major anticancer drugs that are used in breast cancer therapy with many side effects.

Colorimetric Biosensor for Detection of Cancer Biomarker by Au Nanoparticle-Decorated Bi2Se3 Nanosheets

The colorimetric biosensors have attracted intensive interest; however, their relatively low sensitivity limits their applications in clinic detection. Herein, we develop an effective colorimetric biosensor based on highly catalytic active Au nanoparticle-decorated Bi₂Se₃ (Au/Bi₂Se₃) nanosheets. Au/Bi₂Se₃ nanosheets are facilely synthesized by simply sonicating Au precursor with the as-synthesized Bi₂Se₃ nanosheets in aqueous solution. Because of the low redox potential and typical topological insulating properties, Bi₂Se₃ nanosheets is capable of providing and accumulating electrons on its surface. Such unique properties of Bi₂Se₃ nanosheets contribute to strong synergistic catalytic effects with Au nanoparticles, particularly when Au/Bi₂Se₃ nanosheets are utilized for catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH₄ (K = 386.67 s^-1g^-1). The excellent catalytic activity of Au/Bi₂Se₃ nanosheets can be "switched off" upon treatment of antibody of cancer biomarker such as anticarcinoembryonic antibody (anti-CEA). Addition of the corresponding antigen such as cancer biomarker carcinoembryonic antibody (CEA) can successively help "switch on" the catalytic activity of Au/Bi₂Se₃ nanosheets, where the resuming degree however depends on the antigen concentration. This cancer biomarker depended catalytic behavior therefore allows Au/Bi₂Se₃ nanosheets to be employed as a colorimetric sensor for detection of a particular cancer biomarker, for the reduction of 4-nitrophenol (4-NP) by NaBH₄ itself involves apparent color change. The sensor shows high sensitivity and selectivity for the cancer biomarker, even for a concentration as low as 160 pg/mL for CEA, which fully satisfies the requirement for real clinical applications. The developed colorimetric sensor shows good generality for detection of different types of cancer biomarkers, such as α-fetoprotein (AFP) and prostate-specific antigen (PSA). Furthermore, real clinic sample analyzing result shows that the prepared biosensor is efficient for detection of CEA, providing an alternative method in cancer diagnosis.

Catalytic performance of graphene-bimetallic composite for heterogeneous oxidation of acid orange 7 from aqueous solution

In this study, reduced graphene oxide (rGO) embedded with bimetallic nanoparticles of cobalt-manganese oxide (CoMn₂O₄) was fabricated by hydrothermal treatment. The obtained product was characterized and applied for the heterogeneous activation of peroxymonosulfate (PMS) to degrade acid orange 7 (AO7). The characterization results revealed that 10-20 nm nanosized CoMn₂O₄ was homogenously decorated on the surface of rGO. The effect of different CoMn₂O₄ loadings showed that catalyst with a CoMn₂O₄ contents higher than 20% performs stronger capability for catalytic degradation of AO7 compared to pure CoMn₂O₄. In a system containing 4 mM PMS and 0.05 g/L 50% CoMn₂O₄/rGO, 100% conversion of AO7 (70 mg/L) and 43% mineralization could be achieved within 12 and 60 min, respectively. Recycling experiment along with XRD data demonstrates good stability of the catalyst for five successive runs. Inhibition confirmation results suggest that surface-bound SO₄^•- and HO^• radicals both played a key role in degradation of AO7. Therefore, this material demonstrates a very efficient catalytic performance for the degradation of organic dyes.

Gold nanocages decorated biocompatible amine functionalized graphene as an efficient dopamine sensor platform

Nanocomposite of gold nanocages and chemically modified graphene oxide (GNCs/CMG) was synthesized in N,N-dimethylformamide (DMF) for sensitive detection of dopamine (DA). DA is widely spread in central nervous system which can regulates essential body functions like movement and emotional behaviour. In this regard sensitive and fast detection of DA level in human body is still challenging considering its interference with other biomolecules in biological samples. CMG was synthesized through amine modification of graphene oxide (GO) with DMF at relatively high temperature followed by attachment of GNCs, fabricated using a galvanic replacement between silver nanocubes and HAuCl₄ solution in the DMF. X-ray diffraction (XRD) pattern of GNCs/CMG nanocomposite revealed high crystallization of GNCs attached to the graphene nanosheets and microscopic images revealed relatively uniform decoration of GNCs on the surface of CMG. Nanocomposite modified glassy carbon electrode (GNCs/CMG/GCE) was used to investigate the electrochemical behaviour of DA with cyclic voltammetry and amperometry techniques. The linear range for dopamine was between 0.1 and 80μM with a low detection limit of 0.02μM. Furthermore, GNCs/CMG/GCE exhibited satisfying reproducibility, long-term stability and high selectivity for DA detection in large amount of ascorbic acid with good results for determination in human serum samples.

Specific and Sensitive Isothermal Electrochemical Biosensor for Plant Pathogen DNA Detection with Colloidal Gold Nanoparticles as Probes

Developing quick and sensitive molecular diagnostics for plant pathogen detection is challenging. Herein, a nanoparticle based electrochemical biosensor was developed for rapid and sensitive detection of plant pathogen DNA on disposable screen-printed carbon electrodes. This 60 min assay relied on the rapid isothermal amplification of target pathogen DNA sequences by recombinase polymerase amplification (RPA) followed by gold nanoparticle-based electrochemical assessment with differential pulse voltammetry (DPV). Our method was 10,000 times more sensitive than conventional polymerase chain reaction (PCR)/gel electrophoresis and could readily identify P. syringae infected plant samples even before the disease symptoms were visible. On the basis of the speed, sensitivity, simplicity and portability of the approach, we believe the method has potential as a rapid disease management solution for applications in agriculture diagnostics.

Graphene-based multiplexed disposable electrochemical biosensor for rapid on-farm monitoring of NEFA and βHBA dairy biomarkers

Label-free assay using electrodeposited antibody-conjugated graphene biointerface for dual detection of NEFA and βHBA from dairy cow blood samples.

Lipase immobilization on facile synthesized polyaniline-coated silver-functionalized graphene oxide nanocomposites as novel biocatalysts: stability and activity insights

Schematic representation of the preparation of PANI/Ag/GO-NCs and immobilization of lipase.

Three-dimensional N-doped carbon nanotube@carbon foam hybrid: an effective carrier of enzymes for glucose biosensors

NCNTs anchored on carbon foam lead to an effective carrier of enzymes for biosensors.