Graphene Gold Nanoparticles Research Articles

SARS-CoV-2 detection by targeting four loci of viral genome using graphene oxide and gold nanoparticle DNA biosensor

The current COVID-19 pandemic outbreak poses a serious threat to public health, demonstrating the critical need for the development of effective and reproducible detection tests. Since the RT-qPCR primers are highly specific and can only be designed based on the known sequence, mutation sensitivity is its limitation. Moreover, the mutations in the severe acute respiratory syndrome β-coronavirus (SARS-CoV-2) genome led to new highly transmissible variants such as Delta and Omicron variants. In the case of mutation, RT-qPCR primers cannot recognize and attach to the target sequence. This research presents an accurate dual-platform DNA biosensor based on the colorimetric assay of gold nanoparticles and the surface-enhanced Raman scattering (SERS) technique. It simultaneously targets four different regions of the viral genome for detection of SARS-CoV-2 and its new variants prior to any sequencing. Hence, in the case of mutation in one of the target sequences, the other three probes could detect the SARS-CoV-2 genome. The method is based on visible biosensor color shift and a locally enhanced electromagnetic field and significantly amplified SERS signal due to the proximity of Sulfo-Cyanine 3 (Cy3) and AuNPs intensity peak at 1468 cm-1. The dual-platform DNA/GO/AuNP biosensor exhibits high sensitivity toward the viral genome with a LOD of 0.16 ng/µL. This is a safe point-of-care, naked-eye, equipment-free, and rapid (10 min) detection biosensor for diagnosing COVID-19 cases at home using a nasopharyngeal sample.

Electrochemical Quantification of H2O2 Released by Airway Cells Growing in Different Culture Media.

Quantification of oxidative stress is a challenging task that can help in monitoring chronic inflammatory respiratory airway diseases. Different studies can be found in the literature regarding the development of electrochemical sensors for H2O2 in cell culture medium to quantify oxidative stress. However, there are very limited data regarding the impact of the cell culture medium on the electrochemical quantification of H2O2. In this work, we studied the effect of different media (RPMI, MEM, DMEM, Ham’s F12 and BEGM/DMEM) on the electrochemical quantification of H2O2. The used electrode is based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) and was obtained by co-electrodeposition. To reduce the electrode fouling by the medium, the effect of dilution was investigated using diluted (50% v/v in PBS) and undiluted media. With the same aim, two electrochemical techniques were employed, chronoamperometry (CH) and linear scan voltammetry (LSV). The influence of different interfering species and the effect of the operating temperature of 37 °C were also studied in order to simulate the operation of the sensor in the culture plate. The LSV technique made the sensor adaptable to undiluted media because the test time is short, compared with the CH technique, reducing the electrode fouling. The long-term stability of the sensors was also evaluated by testing different storage conditions. By storing the electrode at 4 °C, the sensor performance was not reduced for up to 21 days. The sensors were validated measuring H2O2 released by two different human bronchial epithelial cell lines (A549, 16HBE) and human primary bronchial epithelial cells (PBEC) grown in RPMI, MEM and BEGM/DMEM media. To confirm the results obtained with the sensor, the release of reactive oxygen species was also evaluated with a standard flow cytometry technique. The results obtained with the two techniques were very similar. Thus, the LSV technique permits using the proposed sensor for an effective oxidative stress quantification in different culture media and without dilution.

Co phthalocyanine mediated electrochemical detection of the HER2 in the presence of Au and CeO2 nanoparticles and graphene quantum dots

In this work, cobalt tetra phenoxy acetic acid phthalocyanine (CoTAPc) is investigated as an electron mediator, immobilization platform for an HB5 aptamer and to enhance the electrochemical signal for the detection of human epidermal growth factor receptor 2 (HER2). Furthermore, the CoTAPc was combined individually with sulphur/nitrogen doped graphene quantum dots (SNGQDs), gold nanoparticles (AuNPs) and cerium oxide nanoparticles (CeO2NPs), on a glassy carbon electrode (GCE) via sequential adsorption. The CoTAPc and SNGQDs were also π-π stacked, used for electrode modification similarly to the rest of the other surfaces and applied towards the electrochemical detection of HER2. The designed sensors were characterized using electrochemical impedance spectroscopy (EIS). The designed aptasensors showed detection limits as low as 6.0 pg/mL. The real life applicability of the designed aptasensors was tested in human serum samples. The aptasensors showed great storage stability, sensitivity and specificity towards HER2, implying great potential for applications in early diagnosis of breast cancer.

Electrochemical sensor for imidacloprid detection based on graphene oxide/gold nano/β-cyclodextrin multiple amplification strategy

The key to improving the sensitivity of electrochemical sensors for direct detection is the introduction of catalytically amplified nanomaterials. Accordingly, in this study, a new strategy for the preparation of electrochemical sensors with multiple amplification effects is proposed. Graphene oxide (GO), gold nanoparticles (Au NPs), and β-cyclodextrin (β-CD) were introduced to the surface of a glassy carbon electrode via cyclic voltammetry to prepare a modified electrode sensor with a GO/Au NPs/β-CD thin film. The prepared sensor effectively catalyzed and amplified the reduction current of imidacloprid in a B-R buffer with pH = 5.0 owning to the multiple amplification effects of GO/Au NPs/β-CD. A good linear relationship was observed the level of the reduction current response and the imidacloprid at concentrations ranging from approximately 5 × 10−10 to 3000 × 10−10 mol/L; thus, a new imidacloprid detection method using an electrochemical sensor was established. The new method, whose detection limit reached 1.33 × 10−10 mol/L, was tested on actual samples, achieving recoveries of 92.0 % to 110.0 %.

Superior enhancement of SPR fiber optic sensor using laser sensitized dip-coated graphene gold nanocomposite probes

Surface plasmon resonance SPR fiber optic sensors are valuable optical tools in sensor technology in different disciplines. The sensor performance can be enhanced with tailoring the sensing probe especially using graphene. Here, sensing probes of graphene-gold nanoparticles composite were fabricated by dip coating method on the unclad fiber followed by laser irradiation at different times (0, 2, 5, 10 min). Optical characterization and SPR spectra were studied. Raman spectra confirm the deposition of graphene gold nanocomposite on the bare core, the resonant wavelengths are red-shifted 52, 55, 60 and 63 nm for 0, 2, 5, and 10 min of the irradiated Gn-AuNPs composite/core probe for the analyte range (0–200 ppm), respectively. Laser sensitization has enhanced the sensor performance with superior sensitivity 0.725 nm/ppm and lowest limit of detection for 10 min irradiation, the sensitivity was enhanced 129% with respect to that before laser treatment. The laser sensitization of dip-coated graphene gold nanocomposite is a promising method for enhancing performance parameters of optical fiber sensors.

Plasma-bioresource-derived multifunctional porous NGQD/AuNP nanocomposites for water monitoring and purification

Multifunctional metal–organic composites with controlled structures and properties are attractive for smart optoelectronic, drug delivery, cancer therapy, clean energy, and environmental applications. Here we develop lightweight, porous metal-graphene composites with uniformly dispersed nitrogen-doped graphene quantum dots (NGQDs) and gold nanoparticles (AuNPs) using reactive non-thermal microplasmas under ambient conditions. Synergy of NGQDs and AuNPs accelerates the polymer cross-linking during synthesis and ensures the requisite properties for simultaneous water monitoring and purification including reliable photoluminescence for heavy metal detection, as well as high adsorption capacity and fast catalytic degradation of organic pollutants. Large-area hierarchical composites with tunable porosity and self-healing ability can be fabricated by the fast and scalable plasma process avoiding toxic chemicals and high temperatures. The composite achieves 120 g g−1 water purification within 60 min at 0.13 mM 4-nitrophenol concentration and is able to monitor the water quality against Hg2+ with the detection limit of 2.2 μM, producing 2880 L kg−1 freshwater per day. Besides, almost 100 % of recalcitrant dye, remazol brilliant blue R, with the concentration of 20 ppm can be adsorbed by the composite in 120 min. Our work provides new insights into design and production of high-performance graphene-metal composites for emerging applications.

A rapid fluorescent aptasensor for point-of-care detection of C-reactive protein

In this paper, we report on a novel fluorescent aptasensor based on aptamers modified by both nitrogen-doped graphene quantum dots (N-GQDs) and gold nanoparticles (AuNPs) for the detection of C-reactive protein (CRP). FRET effect is utilized in our aptasensor by the change of aptamers conformation when binding with the target. An obvious fluorescence quench of the N-GQDs can be observed when CRP appears in the assay due to electron transfer between the donor and accepter. A detection limit of 0.2 ng/mL can be achieved by our sensor in PBS buffer which is much lower than the physiological CRP level in human serum. Also, CRP levels in different patients’ serum are tested with our assay. Since our aptasensor is rapid (detection time less than 40 min), one-step and very simple to operate, we believe it has great potential to apply for point-of-care testing (POCT).

Self-assembled tetrahedral DNA nanostructures-based ultrasensitive label-free detection of ampicillin.

Antibiotics are widely used for improving the living conditions of livestock. However, residual antibiotics present in animal products induce several human diseases. Therefore, a simple, rapid, and cost-effective system for detecting and monitoring the presence of antibiotics in foods is in great demand to alleviate safety concerns. In this study, a highly sensitive and selective aptameric electrochemical sensing platform was designed based on nanomaterial modification and DNA nanotechnology. Electrochemically reduced graphene oxide and gold nanoparticles were used to modify the working surface of a screen-printed electrode to enhance electrical conductivity and biocompatibility. The electrode surface was further modified with self-assembled tetrahedral DNA nanostructures (TDN) to improve the detection sensitivity. The TDN allowed controlling the nano-spacing of aptamers immobilized on the electrode surface and placing aptamers in a solution-phase-like detecting environment to improve the target-binding efficiency without signal amplification modules. Differential pulse voltammetry was employed to measure electrical signals in proportion to the amount of ampicillin, the target antibiotic, present in buffer and spiked milk samples. The designed aptasensor was able to detect and measure the target ampicillin in less than 30min over a wide concentration range of 10 pM to 1mM, with a limit of detection of 1 pM, which is 100 times better than when using the same sensing probe without TDN modification. The aptasensor was reusable by simply rinsing with deionized water, remained stable during 15-day storage, and yielded reproducible results.

An electrochemical chiral sensor based on glutamic acid functionalized graphene-gold nanocomposites for chiral recognition of tryptophan enantiomers

• Glu functionalized RGO-Au nanocomposites were synthesized as an electrochemical chiral sensor. • The electrochemical chiral sensor has high chiral recognition capability for Trp enantiomers. • Mechanism and binding thermodynamics were explained by UV–vis and DFT in detail. A novel chiral sensing platform via the glutamic acid (Glu) functionalized graphene-gold nanoparticles (RGO-Au/ l -Glu and RGO-Au/ d -Glu) synthesized via the one-step hydrothermal method is described for the enantioselective recognition of L- and d -tryptophan (Trp). The SEM, TEM, EDS, AFM, FTIR, and XRD characterization techniques showed that RGO-Au/ l -Glu and RGO-Au/ d -Glu chiral composite were successfully synthesized. By combining the chiral features of Glu and the excellent electrochemical behaviors of RGO-Au, two electrochemical chiral sensing interfaces constructed by RGO-Au/ l -Glu and RGO-Au/ d -Glu modified glassy carbon electrode (GCE) were constructed for electrochemical chiral recognition of Trp enantiomers. The results demonstrated that the RGO-Au/ l -Glu/GCE showed the highest chiral recognition efficiency, the enantioselectivity coefficient (I L /I D ) was 2.56. UV–vis absorption spectroscopy and density functional theory (DFT) calculations proved that RGO-Au/ l -Glu had a strong binding ability with l -Trp. In addition, the chiral sensing interface had a linear response in the 1 mM to 5 mM Trp concentration range and a 0.28 mM detection limit (at S/N = 3) for l -Trp, and 0.86 mM to d -Trp, also had good stability and reproducibility, which can be used as an efficient chiral sensing interface for the recognition of Trp enantiomers.

An Electrochemical Immunosensor Based on Gold-Graphene Oxide Nanocomposites with Ionic Liquid for Detecting the Breast Cancer CD44 Biomarker.

We develop a highly sensitive electrochemical immunosensor for the detection of a cluster of differentiation-44 (CD44) antigen, a breast cancer biomarker. The hybrid nanocomposite consists of graphene oxide, ionic liquid, and gold nanoparticles (GO-IL-AuNPs) immobilized on a glassy carbon electrode. GO favors the immobilization of antibodies because of the availability of oxygen functionalities. However, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM.BF4) and AuNPs facilitate electron transfer and increase the effective surface area, which enhances the performance of the immunosensor. Furthermore, UV-visible, fourier transform infrared and Raman spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, voltammetry, and electrochemical impedance spectroscopy characterization techniques have been employed to investigate the structural and chemical properties of the nanomaterials. The quantitative detection of CD44 antigen has been accomplished via differential pulse voltammetry and EIS detection techniques. It has been quantified that the proposed immunosensor offers excellent detection ability in both phosphate-buffered saline (PBS) and serum samples. Under optimum conditions, the linear detection range of the immunosensor for CD44 antigen is 5.0 fg mL-1 to 50.0 μg mL-1 and the limit of detection is 2.0 and 1.90 fg mL-1 as observed via DPV and EIS, respectively, in PBS. Additionally, the immunosensor has high sensitivity and specificity and can be successfully applied for the detection of CD44 antigen in clinical samples.

Selective and Sensitive Fluorometric Determination of Piroxicam Based on Nitrogen-doped Graphene Quantum Dots and Gold Nanoparticles Coated with Phenylalanine.

In this study, a sensitive fluorimetric method is proposed for the determination of piroxicam using nitrogen graphene quantum dots (N-GQDs) and gold nanoparticles coated with phenylalanine. The fluorescence emission of N-GQDs at 440nm decreases with the increase of gold nanoparticles coated with phenylalanine. However, the addition of piroxicam causes the release of gold nanoparticles from the surface of quantum dots followed by the retrieval of the fluorescence emission of N-GQDs. Under the optimum conditions, the calibration graph was linear in the concentration range of 2.0-35.0nmol L-1 for piroxicam with a limit of detection of 0.11nmol L-1. The developed method was successfully applied for the determination of piroxicam in urine and serum samples.

Microfluidic electrochemical magnetoimmunosensor for ultrasensitive detection of interleukin-6 based on hybrid of AuNPs and graphene.

Cytokines are important factors in the early diagnosis of autoimmune diseases and require high sensitivity, high selectivity and quantitative detection. We proposed a miniaturized electrochemical magneto-immunosensor (EC-MIS) on portable interleukin-6 (IL-6) detection based on this requirement. Firstly, a micro-fabricated working electrode is electrochemically modified with a hybrid of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs). Increased surface area and enhanced charge transfer rate improve the performance of this immunosensor on sensitivity. Secondly, magnetic beads attached with the capture antibody (cAb) are employed in sandwich immunoassay. This kind of immunoassay is immobilized on the working electrode surface by an external magnet to enrich the analyte IL-6. Thirdly, the last two features are combined and integrated on a microfluidic device in order to restrict the sample at certain areas and ease the operation of detection. With our prototypic EC-MIS operated in amperometric mode, we have achieved the detection of IL-6 with a linear range from 0.97 to 250pg/mL and a limit of detection (LOD) of 0.42pg/mL. Real serum samples were demonstrated and compared with benchtop equipment's results.

A Rapid Graphene Sensor Platform for the Detection of Viral Proteins in Low Volume Samples

Infectious disease outbreaks remain an ever‐prevalent global issue. The associated demand for rapid diagnostics and onsite testing will play an increasing and critical role in disease surveillance, prevention of the spread of infection, as well as timely commencement of treatment. Reported here is a graphene–gold nanoparticle hybrid sensor platform technology that is demonstrated for the real‐time detection of viral proteins utilizing low volume samples (5 μL). Hepatitis C virus (HCV) is still an endemic problem worldwide and is used as an exemplar system here to demonstrate the capability of the platform viral detection sensor technology. Hepatitis C virus core antigen (HCVcAg) is a promising marker for point‐of‐care (POC) diagnostic testing for active HCV infection, with the potential to provide a one‐stop diagnosis and trigger for the commencement of treatment. Real‐time electrical resistance measurements are performed using various concentrations of HCVcAg with linear concentration dependence of resistance on HCVcAg concentration over the range of 100–750 pg mL−1.

Porous polydimethylsiloxane composite filled with graphene oxide and gold nanoparticles produced by laser ablation in liquids

The design of new materials with improved mechanical and biological properties is a major interest in biomedical applications. This paper presents the synthesis of macro-porous polydimethylsiloxane (PDMS) sponge composites as potential materials for tissue engineering. PDMS sponge with pores size ranging between 50 and 900 μm was produced using the sugar templating process. The sponges were decorated with graphene oxide and gold nanoparticles created by the laser ablation in liquid and then they were morphologically, mechanically and biologically characterized. The optical properties of all the solutions containing nanoparticles were studied with the UV-ViS spectroscopy. The biological behaviour and performance of native PDMS, PDMS decorated with graphene oxide, and with graphene oxide and gold nanoparticles were compared. Results show that the composites and equally as important the adopted processing are both biocompatible. The quality of filler dispersion in the porous composites was observed by scanning electron (SEM) and atomic force (AFM) microscopies. The biocompatibility of the composites and of the preparation procedure was confirmed by monitoring the cytotoxicity of the composites for different types of cell cultures.

Enhancing Peptide Nucleic Acid–Nanomaterial Interaction and Performance Improvement of Peptide Nucleic Acid-Based Nucleic Acid Detection by Using Electrostatic Effects

Single-stranded peptide nucleic acid (PNA) probes interact strongly with several nanomaterials, and the interaction was diminished in the presence of complementary nucleic acid targets which forms the basis of many nucleic acid sensing platforms. As opposed to the negatively charged DNA probes, the charges on the PNA probes may be fine-tuned by incorporating amino acids with charged side chains. The contribution of electrostatic effects to the interaction between PNA probes and nanomaterials has been largely overlooked. This work reveals that electrostatic effects substantially enhanced the quenching of dye-labeled conformationally constrained pyrrolidinyl PNA probes by several nanomaterials including graphene oxide (GO), reduced graphene oxide, gold nanoparticles (AuNPs), and silver nanoparticles. The fluorescence quenching and the color change from red to purple in the case of AuNPs because of aggregation were inhibited in the presence of complementary nucleic acid targets. Thus, fluorescence and colorimetric assays for DNA and RNA that can distinguish even single-base-mismatched nucleic acids with improved sensitivity over conventional DNA probes were established. Both the GO- and AuNP-based sensing platforms have been successfully applied for the detection of real DNA and RNA samples in vitro and in living cells. This study emphasizes the active roles of electrostatic effects in the PNA-nanomaterial interactions, which paves the way toward improving the performance of PNA-nanomaterial based assays of nucleic acids.

Nanozymatic detection of thiocyanate through accelerating the growth of ultra-small gold nanoparticles/graphene quantum dots hybrids

Thiocyanate (SCN−) concentration monitoring in food is important to ensure the health and safety of the consumers.A colorimetric detection of thiocyanate (SCN−) based on the nanozymatic activity of gold nanoparticle-graphene quantum dots (GQDs-Au NPs) hybrids in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 has been proposed. Here, a new synthesis method of GQDs directly from graphite was introduced. Transmission electron microscopy (TEM) images revealed that the size of the GQDs was 3–5 nm, and the emission peak appeared at 450 nm. As-synthesized GQDs was utilized to produce GQDs-Au NPs hybrids without additional chemicals. However, the presence of SCN− inhibits the growth of Au NPs, the resulting Au NPs are smaller in size. Moreover, SCN− group is well-known for hydroxyl radical (OH) scavenging activity that could oxidize TMB. Both effects boosted the nanozymatic activity of GQDs-Au NPs to detect SCN− under optimized conditions with a limit of detection (LOD) of 3 nM. Present study also validates the methodology to detect SCN− in raw milk.

Nanoparticles embedded in a sponge of polydimethylsiloxane by laser ablation in liquid

This work describes the preparation of polydimethylsiloxane (PDMS) sponge with pore sizes of about 50 and 900 µm. The sponges synthetized by the sugar template process were embedded with graphene oxide (GO) and gold nanoparticles (AuNPs) previously produced by laser ablation in liquid. The suspension containing graphene oxide and gold nanoparticles were optically characterized by UV-ViS spectroscopy. The dispersion of the nanoparticles in the PDMS sponges was observed by the Scanning Electron Microscopy (SEM). The biocompatibility of virgin PDMS, PDMS filled with graphene oxide, and with graphene oxide and gold nanoparticles was studied for different types of cell cultures. This study has allowed us to confirm that the PDMS sponge is a good matrix for embedding AuNPs and has highlighted as the presence of GO hinders the aggregation of AuNPs avoiding the use of surfactant and allowing their use in biological applications.

Detection of chymotrypsin using a peptide sensor based on graphene oxide modified with sulfhydryl groups and gold nanoparticles

Schematic of chymotrypsin detection based on thiol-modified graphene oxide and gold nanoparticles.

Flexible Electrochemical Sensor With Graphene and Gold Nanoparticles to Detect Dopamine and Uric Acid

Electrochemical sensor is a promising platform in diagnosing the disorders of nervous and metabolic systems for its feasibility of detecting dopamine (DA) and uric acid (UA). Nevertheless, the reported electrochemical sensors still suffer from unfavorable selectivity and the high limit of detection (LOD). To address these problems, this paper introduced a heterogeneous electrode interface to improve the sensor’s selectivity with differently charged regions. The electrode was prepared on a flexible polyolefin substrate and modified with negatively charged graphene (GP) and electroneutral gold nanoparticles (Au NPs). Experimental results show that the optimal electrode with five layers GP and Au NPs (GP5AuNPs5) was capable of detecting DA and UA in the ascorbic acid (AA)-coexisted solution with minimum interference. The GP5AuNPs5 sensor manifests low LODs ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3 {\sigma } /\text{S}$ </tex-math></inline-formula> ) of 10 nM and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.47 {\mu } \text{M}$ </tex-math></inline-formula> for DA and UA, respectively, confirming its feasibility to detect the lowest concentration of the human body. Moreover, the introduction of the Au NPs makes a better separation for current peaks, which might be from the existence of a concentration gradient by electrostatic force difference and an enhanced diffusion from Au NPs. The high-performance sensor with well-separated current peaks is meaningful for detecting DA and UA electrochemically.

Improving graphene/4H-SiC/graphene MSM UV photodetector sensitivity using interdigitated electrodes formalism and embedded gold plasmonic nanoparticles

In this paper, a novel 4H-SiC metal–semiconductor-metal photodetector design based on Graphene electrode engineering and gold nanoparticles is proposed. The benefits of using an intense light trapping formalism to improve the optical performance of the 4H-SiC PD are investigated by means of an accurate optoelectronic model. The developed model is based on the EMT and avoids the difficulty of considering all nanoparticles. The precision assessment of the built model is carried out by comparison with the experimental data. The findings shed light on the ability of the proposed design to realize the dual task of reducing the unwanted shadowing effect and improving the absorption through Graphene electrode formalism and the Surface Plasmon Resonance effect in the 4H-SiC layer. Furthermore, to optimize the design sensing capability, the proposed model is adopted to formulate fitness functions for the multi-objective genetic algorithm. It is found that for a filling fraction of 0.02 and 7.5 nm radius, the optimized design yields 50 % increase in absorption compared to the standard designs where responsivity of 458 mA/W, PDCR of 3.05 × 106 and response time of 4.7 µs are achieved. These findings confirm the outstanding ability of the proposed design approach to boost up the PD active area for low-cost and high sensing capability, making it valuable for optoelectronic application.