Reduced graphene oxide-Hemin-Au nanohybrids: Facile one-pot synthesis and enhanced electrocatalytic activity towards the reduction of hydrogen peroxide

Detection of glucose transporter 1 in living cells for assessment of tumor development and therapy using an electrochemical biosensor

The expression level of glucose transporter 1 (GLUT-1) is highly correlated with tumor malignancy, making it a promising therapeutic target for cancer treatment. The detection of GLUT-1 expression level is significant for cancer discovery and valuating the efficacy of drug treatments. However, current methods for GLUT-1 detection primarily rely on traditional techniques. Therefore, the development of anon-destructive in vivo monitoring system would be invaluable for assessing GLUT-1 expression and tumor responses to various drugs. In this study, an electrochemical platform for detection of GLUT-1 on living cells was established using reduced graphene oxide-multi-wall carbon nanotube composite (rGO-MWCNT) as a conductive coating and toluidine blue O (TBO)-graphene-gold nanoparticle-GLUT-1 antibody as the electrochemical probe. The sensor demonstrated excellent performance in detecting GLUT-1 on cells with a linear range of 10 - 105 cells/mL, good stability and selectivity. The sensor successfully detected GLUT-1 expressions in multiple tumor cell types, including those treated with siRNA or drugs, and the results were consistent with those obtained from traditional methods such as flow cytometry, western blotting, and immunofluorescence. The sensor is promising in evaluating the malignant level of tumor cells, distinguishing glucose uptake pathways in tumor cells, reducing medical costs, and facilitating the translation of electrochemical sensing technology to the clinical settings.

Dual Ni/Co-hemin metal-organic framework-PrGO for high-performance asymmetric hybrid supercapacitor

In this study, we conducted direct synthesis of a dual metal-organic framework (Ni/Co-Hemin MOF) on phosphorous-doped reduced graphene oxide (PrGO) to serve as an active material in high-performance asymmetrical supercapacitors. The nanocomposite was utilized as an active material in supercapacitors, exhibiting a noteworthy specific capacitance of 963 C g^-1 at 1.0 A g^-1, along with a high rate capability of 68.3% upon increasing the current density by 20 times, and superior cycling stability. Our comprehensive characterization and control experiments indicated that the improved performance can be attributed to the combined effect of the dual MOF and the presence of phosphorous, influencing the battery-type supercapacitor behavior of GO. Additionally, we fabricated an asymmetric hybrid supercapacitor (AHSC) using Ni/Co-Hemin/PrGO/Nickel foam (NF) and activated carbon (AC)/NF. This AHSC demonstrated a specific capacitance of 281 C g^-1 at 1.0 A g^-1, an operating voltage of 1.80 V, an impressive energy density of 70.3 Wh kg^-1 at a high power density of 0.9 kW kg^-1. Notably, three AHSC devices connected in series successfully powered a clock for approximately 42 min. These findings highlight the potential application of Hemin-based MOFs in advanced supercapacitor systems.

Recent Insights into Sample Pretreatment Methods for Mycotoxins in Different Food Matrices: A Critical Review on Novel Materials

Mycotoxins pollution is a global concern, and can pose a serious threat to human health. People and livestock eating contaminated food will encounter acute and chronic poisoning symptoms, such as carcinogenicity, acute hepatitis, and a weakened immune system. In order to prevent or reduce the exposure of human beings and livestock to mycotoxins, it is necessary to screen mycotoxins in different foods efficiently, sensitively, and selectively. Proper sample preparation is very important for the separation, purification, and enrichment of mycotoxins from complex matrices. This review provides a comprehensive summary of mycotoxins pretreatment methods since 2017, including traditionally used methods, solid-phase extraction (SPE)-based methods, liquid-liquid extraction (LLE)-based methods, matrix solid phase dispersion (MSPD), QuEChERS, and so on. The novel materials and cutting-edge technologies are systematically and comprehensively summarized. Moreover, we discuss and compare the pros and cons of different pretreatment methods and suggest a prospect.

Development of conducting cellulose paper for electrochemical sensing of procalcitonin

An electrochemical paper-based sensor was developed for the detection of bacterial infection (BI)-specific biomarker procalcitonin (PCT). Reduced graphene oxide-gold nanoparticles (rGO-AuNP) and poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were synthesized and were fabricated to a disposable, portable, and inexpensive cellulose fiber paper (CFP) substrate. rGO-AuNP-PEDOT:PSS nanocomposite-modified conductive paper-based biosensing platform was efficaciously fabricated by a constant and simple coating procedure. rGO-AuNP-PEDOT:PSS nanocomposite-modified conductive paper electrode was found to provide a sensitive and conductive substrate for PCT detection. The presence of rGO-AuNP-PEDOT:PSS nanocomposite on CFP substate was investigated by Fourier transform infrared spectrometry, field emission scanning electron microscopy, ultraviolet-visible spectroscopy, and X-ray diffraction studies. The electrochemical behavior of rGO-AuNP-PEDOT:PSS @CFP surface was studied with impedance spectroscopy, cyclic voltammetry, and chronoamperometry techniques. This low-cost paper-based biosensor has a linear range for PCT of 1 × 10³ to 6 × 10⁷ fg mL^-1. This developed sensor exhibited good reproducibility with a relative standard deviation (RSD) of about 3.7%. The proposed CFP-based biosensor has been proven as an accelerated simple point-of-care (POC) exploratory approach for early PCT diagnosis in inadequate areas with limited production facilities, computational techniques, and highly skilled experts.

GNP-CeO2- polyaniline hybrid hydrogel for electrochemical detection of peroxynitrite anion and its integration in a microfluidic platform

Peroxynitrite anion (ONOO^-) is an important in vivo oxidative stress biomarker whose aberrant levels have pathophysiological implications. In this study, an electrochemical sensor for ONOO^- detection was developed based on graphene nanoplatelets-cerium oxide nanocomposite (GNP-CeO₂) incorporated polyaniline (PANI) conducting hydrogels. The nanocomposite-hydrogel platform exhibited distinct synergistic advantages in terms of large electroactive surface coverage and providing a conductive pathway for electron transfer. Besides, the 3D porous structure of hydrogel integrated the GNP-CeO₂ nanocomposite to provide hybrid materials for the evolution of catalytic activity towards electrochemical oxidation of ONOO^-. Various microscopic and spectroscopic characterization techniques endorsed the successful formation of GNP-CeO₂-PANI hydrogel. Cyclic voltammetry (CV) measurements of GNP-CeO₂-PANI hydrogel modified screen-printed electrodes (SPE) were carried out to record the current changes influenced by ONOO^-. The prepared sensor demonstrated a significant dose-dependent increase in CV peak current within a linear range of 5-100 µM (at a potential of 1.12 V), and a detection limit of 0.14 with a sensitivity of 29.35 ± 1.4 μA μM^-1. Further, a customized microfluidic flow system was integrated with the GNP-CeO₂-PANI hydrogel modified SPE to enable continuous electrochemical detection of ONOO^- at low sample volumes. The developed microfluidic electrochemical device demonstrated an excellent sensitivity towards ONOO^- under optimal experimental conditions. Overall, the fabricated microfluidic device with hybrid hydrogels as electrochemical interfaces provides a reliable assessment of ONOO^- levels. This work offers considerable potential for understanding the oxidative stress-related disease mechanisms through determination of ONOO^- in biological samples.

Luminescence-Sensing Tb-MOF Nanozyme for the Detection and Degradation of Estrogen Endocrine Disruptors

Using flexible structures and components of metal-organic framework (MOF) materials, we designed and developed an artificial nanozyme with dual functions of a catalyst and luminescent sensor specifically for the determination and degradation of hormone 17β-estradiol (E2) and its derivatives (E1, E3, and EE2), a class of disruptors with strong effect on the human endocrine system. This nanozyme composed of the luminescent Tb³⁺ ion, catalytic coenzyme factor hemin, and light-harvesting ligand can be used to both degrade E2 like natural horseradish peroxidase (HRP) and sense E2 as low as 50 pM by its luminescence. The nanozyme catalyzes the decomposition of E2 and its derivatives through a mechanism of active hydroxyl radicals and oxidative high-valent iron-oxo intermediates. The prepared nanozyme is pluripotent, stable, and cheap and can replace the widely used combination of natural enzyme and chromogenic substrate. The present strategy of constructing artificial enzymes directly from functional units provides a new way for the design and development of smart, multifunctional artificial enzymes.

A sandwich-type electrochemical aptasensor for the carcinoembryonic antigen via biocatalytic precipitation amplification and by using gold nanoparticle composites

A sandwich-type electrochemical aptasensor is described for detecting the carcinoembryonic antigen (CEA) with high sensitivity and accuracy. Two kinds of nanomaterials are used. The first was obtained by modifying gold nanoparticles with reduced graphene oxide and hemin (Hemin-rGO-AuNPs). The second consists of horseradish peroxidase-modified organic-inorganic hybrid nanoflowers linked to gold nanoparticles to obtain an architecture of type HRP-Cu₃(PO₄)₂-HNF-AuNPs). These serve as carriers for two aptamers (apt1 and apt2) against CEA. Simultaneously, they were used to catalyze the precipitation reaction between 4-chloro-1-naphthol(4-CN) and H₂O₂. A sandwich-type assay linked to enzyme inhibition amplification was established for electrochemical determination of CEA. Under optimal experimental conditions and by using differential pulse voltammetry, the response peak currents (best measured at -0.34 V vs. Ag/AgCl) increases linearly with the logarithm of the CEA concentration in the range between 100 fg mL^-1 and 100 ng mL^-1. The detection limit is as low as 29 fg mL^-1. Graphical abstract Schematic representation of the sandwich-type electrochemical aptasensor based on signal inhibition amplification from biocatalytic precipitation reaction. (HRP-Cu₃(PO₄)₂ hybrid nanoflowers: Horseradish Peroxidase-Cu₃(PO₄)₂ hybrid nanoflowers; AuNPs: Gold Nanoparticles; Hemin-rGO-AuNPs: Hemin-Reduced Graphene Oxide-Gold Nanoparticles; BSA: Bovine Serum Albumin; CEA: Carcinoembryonic Antigen; CEA_apt1: 5'-SH-(CH₂)₆-ATA CCA GCT TAT TCA ATT-3'; CEA_apt2: 5'-NH₂-(CH₂)₆-AGG GGG TGA AGG GAT ACC C-3'; GCE: Glassy carbon electrode; 4-CN: 4-Chloro-1-naphthol; DPV: Differential pulse voltammetry).

A New Sensor for Methyl Paraben Using an Electrode Made of a Cellulose Nanocrystal-Reduced Graphene Oxide Nanocomposite

A new cellulose nanocrystal-reduced graphene oxide (CNC-rGO) nanocomposite was successfully used for mediatorless electrochemical sensing of methyl paraben (MP). Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) studies confirmed the formation of the CNC-rGO nanocomposite. Cyclic voltammetry (CV) studies of the nanocomposite showed quasi-reversible redox behavior. Differential pulse voltammetry (DPV) was employed for the sensor optimization. Under optimized conditions, the sensor demonstrated a linear calibration curve in the range of 2 × 10^-4-9 × 10^-4 M with a limit of detection (LOD) of 1 × 10^-4 M. The MP sensor showed good reproducibility with a relative standard deviation (RSD) of about 8.20%. The sensor also exhibited good stability and repeatability toward MP determinations. Analysis of MP in cream samples showed recovery percentages between 83% and 106%. Advantages of this sensor are the possibility for the determination of higher concentrations of MP when compared with most other reported sensors for MP. The CNC-rGO nanocomposite-based sensor also depicted good reproducibility and reusability compared to the rGO-based sensor. Furthermore, the CNC-rGO nanocomposite sensor showed good selectivity toward MP with little interference from easily oxidizable species such as ascorbic acid.

A hybrid nanocomposite of CeO2–ZnO–chitosan as an enhanced sensing platform for highly sensitive voltammetric determination of paracetamol and its degradation product p-aminophenol

A highly selective electrochemical sensor was fabricated based on CeO₂–ZnO–chitosan hybrid nanocomposite modified electrode and was successfully applied for the determination of PAR in pharmaceutical formulations.

Ni-hemin metal-organic framework with highly efficient peroxidase catalytic activity: toward colorimetric cancer cell detection and targeted therapeutics

Background

Given the great benefits of artificial enzymes, a simple approach is proposed via assembling of Ni²⁺ with hemin for synthesis of Ni-hemin metal–organic-frameworks (Ni-hemin MOFs) mimic enzyme. The formation of the Ni-hemin MOFs was verified by scanning electron microscopy, Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Energy-dispersive X-ray spectroscopy and UV–vis absorption spectroscopy. This novel nanocomposite exhibited surprising peroxidase like activity monitored by catalytic oxidation of a typical peroxidase substrate, 3,3,5,5′-tetramethylbenzidine, in the presence of H₂O₂. By using folic acid conjugated MOF nanocomposite as a recognition element, we develop a colorimetric assay for the direct detection of cancer cells.

Results

The proposed sensor presented high sensitivity and selectivity for the detection of human breast cancer cells (MCF-7) and Human Caucasian gastric adenocarcinoma. By measuring UV–vis absorbance response, a wide detection range from 50 to 10⁵ cells/mL with a detection limit as low as 10 cells/mLwas reached for MCF-7 cells. We further discuss therapeutics efficiency of Ni-hemin MOFs in the presence of H₂O₂ and ascorbic acid. Peroxidase-mimic Ni-hemin MOFs as reactive oxygen species which could damage MCF-7 cancer cells, however for normal cells (human embryonic kidney HEK 293 cells) killing effect was negligible.

Conclusions

Based on these behaviors, the developed method offers a fast, easy and cheap assay for the interest in future diagnostic and treatment application.

Enhanced reversible redox activity of hemin on cellulose microfiber integrated reduced graphene oxide for H2O2 biosensor applications

In recent years, the carbohydrate polymers incorporated composite materials have shown significant interest in the bioanalytical chemistry due to their enhanced catalytic performances of various enzymes or mimics. This paper reports the fabrication of novel H₂O₂ biosensor using a hemin immobilized reduced graphene oxide-cellulose microfiber composite (hemin/RGO-CMF). The RGO-CMF composite was prepared by the reduction of GO-CMF composite using vitamin C as a reducing agent. Various physio-chemical methods have applied for the characterization of RGO-CMF composite. Cyclic voltammetry results revealed that the hemin/RGO-CMF composite shows a better redox electrochemical behavior than hemin/RGO and hemin/GO-CMF. Under optimized conditions, the hemin/RGO-CMF composite exhibit a linear response to H₂O₂ in the concentration range from 0.06 to 540.6 μM with the lower detection limit of 16 nM. The sensor also can able to detect the H₂O₂ in commercial contact lens solution and milk samples with functional recovery, which authenticates the potential ability in practical sensors.

A novel absorption spectrometric method, based on graphene nanomaterials, for detection of hepatocellular carcinoma-specific T lymphocyte cells

Introduction

Detection of antigen-specific cytotoxic T lymphocytes (CTLs) is the foundation for understanding hepatocellular carcinoma immune pathology and hepatocellular carcinoma immunotherapy. However, the classical method for labeling CTLs, major histocompatibility complex (MHC)–peptide tetramer, has drawbacks and needs further improvement.

Materials and methods

Here, as a new detection probe, a graphene-based MHC–peptide multimer was developed for sensitively and selectively identifying hepatocellular carcinoma-specific T-cells. To assess its detection efficiency, reduced graphene oxide (RGO) was functionalized with hemin and streptavidin to prepare a functionalized HRGO–streptavidin complex. Biotinylated MHC–peptide monomer was subsequently constructed onto HRGO to generate a detection probe for CTL labeling. The number of T-cells was detected through the reaction between HRGO and tetramethylbenzidine.

Results

Using HRGO/MHC–peptide multimers, the number of T-cells was efficiently detected in both the induction system in vitro and in peripheral blood of patients.

Conclusion

HRGO/MHC-peptide multimers methodology has application prospects in the detection of antigen peptide-specific T cells.

Highly sensitive fluorogenic sensing of L-Cysteine in live cells using gelatin-stabilized gold nanoparticles decorated graphene nanosheets

A highly sensitive and selective fluorogenic sensing of L-Cysteine (L-Cys) was implemented based on gelatin stabilized gold nanoparticles decorated reduced graphene oxide (rGO/Au) nanohybrid. The rGO/Au nanohybrid was prepared by the one-pot hydrothermal method and well characterized by different physiochemical techniques. The nanohybrid exhibits a weak fluorescence of rGO due to the energy transfer from the rGO to Au NPs. The rGO/Au nanohybrid shows enhanced fluorescence activity due to the restoration of quenched fluorescence of rGO/Au nanohybrid in presence of L-Cys. The rGO/Au nanohybrid exhibits much lower detection limit of 0.51 nM for L-Cys with higher selectivity. The fluorescence sensing mechanism arose from the fluorescence recovery due to the stronger interaction between Au NPs and L-Cys, and consequently, the energy transfer was prevented between rGO and Au NPs. The practicability of rGO/Au sensor was implemented by invitro bioimaging measurements in Colo-205 (colorectal adenocarcinoma) and MKN-45 (gastric carcinoma) cancer live cells with excellent biocompatibility.

Progress in utilisation of graphene for electrochemical biosensors

This review discusses recent graphene (GR) electrochemical biosensor for accurate detection of biomolecules, including glucose, hydrogen peroxide, dopamine, ascorbic acid, uric acid, nicotinamide adenine dinucleotide, DNA, metals and immunosensor through effective immobilization of enzymes, including glucose oxidase, horseradish peroxidase, and haemoglobin. GR-based biosensors exhibited remarkable performance with high sensitivities, wide linear detection ranges, low detection limits, and long-term stabilities. Future challenges for the field include miniaturising biosensors and simplifying mass production are discussed.

Reduced Graphene Oxide-Gold Nanoparticle Nanoframework as a Highly Selective Separation Material for Aflatoxins

Graphene-based materials have been studied in many applications, owing to the excellent electrical, mechanical, and thermal properties of graphene. In the current study, an environmentally friendly approach to the preparation of a reduced graphene oxide-gold nanoparticle (rGO-AuNP) nanocomposite was developed by using L-cysteine and vitamin C as reductants under mild reaction conditions. The rGO-AuNP material showed a highly selective separation ability for 6 naturally occurring aflatoxins, which are easily adsorbed onto traditional graphene materials but are difficult to be desorbed. The specificity of the nanocomposite was evaluated in the separation of 6 aflatoxin congeners (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, aflatoxin M1 and aflatoxin M2) from 23 other biotoxins (including, ochratoxin A, citrinin, and deoxynivalenol). The results indicated that this material was specific for separating aflatoxin congeners. The synthesized material was further validated by determining the recovery (77.6–105.0%), sensitivity (limit of detection in the range of 0.05–0.21 μg kg⁻¹), and precision (1.5–11.8%), and was then successfully applied to the separation of aflatoxins from real-world maize, wheat and rice samples.

A highly sensitive electrochemical immunosensor for hepatitis B virus surface antigen detection based on Hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme-signal amplification

Here we prepared an electrochemical immunosensor employing Au sheet as working electrode, Fe₃O₄ magnetic nanoparticles (MNPs) as supporting matrix and hemin/G-quadruplex DNAzyme as signal amplifier for determination of hepatitis B virus surface antigen (HBsAg). First, the primary antibody of HBs (Ab₁) was immobilized on the surface of the carboxyl-modified MNPs. Then, the assembly of antibody and alkylthiol/G-quadruplex DNA/hemin on gold nanoparticles was used as bio-bar-coded nanoparticle probe. Protein target was sandwiched between the primary antibody of HBs (Ab₁) immobilized on the MNPs and hemin bio-bar-coded AuNPs probe labeled antibody (Ab₂). Hemin/G-quadruplex structure as HRP mimicking-DNAzyme significantly improved the catalytic reduction of H₂O₂ by oxidation of methylene blue (MB). Square wave voltammetry signals of MB provided quantitative measurements of HBsAg with a linear concentration range of 0.3-1000 pgmL^-1 and detection limit of 0.19 pgmL^-1. Due to efficient catalytic activity of HRP mimicking-DNAzyme, the proposed immunosensor exhibited high sensitivity and it holds great promise for clinical application and provides a new platform for immunosensor development and fast disease diagnosis.

One-Pot Green Synthesis of Graphene Nanosheets Encapsulated Gold Nanoparticles for Sensitive and Selective Detection of Dopamine

We report a simple new approach for green preparation of gallic acid supported reduced graphene oxide encapsulated gold nanoparticles (GA-RGO/AuNPs) via one-pot hydrothermal method. The as-prepared composites were successfully characterized by using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray powder diffraction techniques (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM) and elemental analysis. The GA-RGO/AuNPs modified electrode behaves as a hybrid electrode material for sensitive and selective detection of dopamine (DA) in presence of ascorbic acid (AA) and uric acid (UA). The GA-RGO/AuNPs modified electrode displays an excellent electrocatalytic activity towards the oxidation of DA and exhibits a wide linear response range over the DA concentrations from 0.01-100.3 μM with a detection limit (LOD) of 2.6 nM based on S/N = 3. In addition, the proposed sensor could be applied for the determination of DA in human serum and urine samples for practical analysis.

Low potential detection of indole-3-acetic acid based on the peroxidase-like activity of hemin/reduced graphene oxide nanocomposite

An amperometric sensor was firstly established for the detection of indole-3-acetic acid (IAA) at low potential based on the hemin/reduced graphene oxide (hemin/rGO) composite. The hemin/rGO nanocomposite was prepared by a simple and facile hydrothermal method without using any reducing agent. It exhibited peroxidase-like activity for the catalytic oxidation of IAA in the presence of oxygen. The consumption of oxygen has a linear relationship with the concentration of IAA in the range from 0.1 to 43μM and from 43 to 183μM. The detection limit was down to 0.074μM. This sensor was unaffected by many interfering substances and stable over time. Such work broadened the application of hemin/rGO and provided a new method for IAA detection.

Highly stable biomolecule supported by gold nanoparticles/graphene nanocomposite as a sensing platform for H2O2 biosensor application

Highly stable biomolecule supported by AuNPs assisted with graphene nanocomposite as a sensing platform for H₂O₂ biosensor application.