Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing

A Sensitive Enzymatic Electrochemical Biosensor for Cholesterol Based on Cobalt Ferrite@Molybdenum Disulfide/Gold Nanoparticles

Cholesterol is essential in biological systems, and the level of cholesterol in the body of a person acts as a diagnostic marker for a variety of diseases. So, in this work, we fabricated an enzymatic electrochemical biosensor for cholesterol using cobalt ferrite@molybdenum disulfide/gold nanoparticles (CoFe2O4@MoS2/Au). The synthesized composite was used for the determination of cholesterol by voltametric methods. The electroactive material CoFe2O4@MoS2/Au was successfully verified from the physiochemical studies such as XRD, Raman, FT-IR, and XPS spectroscopy along with morphological FESEM and HRTEM characterization. CoFe2O4@MoS2/Au showed outstanding dispersion in the aqueous phase, a large effective area, good biological compatibility, and superior electronic conductivity. The microflower-like CoFe2O4@MoS2/Au was confirmed by scanning electron microscopy. The image of transmission electron microscopy showed decoration of gold nanoparticles on CoFe2O4@MoS2 surfaces. Furthermore, a one-step dip-coating technique was used to build the biosensor used for cholesterol detection. In addition to acting as an enabling matrix to immobilize cholesterol oxidase (ChOx), CoFe2O4@MoS2/Au contributes to an increase in electrical conductivity. The differential pulse voltammetry method was used for the quantitative measurement of cholesterol. The calibration curve for cholesterol was linear in the concentration range of 5 to 100 μM, with a low limit of detection of 0.09 μM and sensitivity of 0.194 μA μM-1 cm-2. Furthermore, the biosensor demonstrates good practicability, as it was also employed for identifying cholesterol in real samples with acceptable selectivity and stability.

Biominerals and Bioinspired Materials in Biosensing: Recent Advancements and Applications

Inspired by nature's remarkable ability to form intricate minerals, researchers have unlocked transformative strategies for creating next-generation biosensors with exceptional sensitivity, selectivity, and biocompatibility. By mimicking how organisms orchestrate mineral growth, biomimetic and bioinspired materials are significantly impacting biosensor design. Engineered bioinspired materials offer distinct advantages over their natural counterparts, boasting superior tunability, precise controllability, and the ability to integrate specific functionalities for enhanced sensing capabilities. This remarkable versatility enables the construction of various biosensing platforms, including optical sensors, electrochemical sensors, magnetic biosensors, and nucleic acid detection platforms, for diverse applications. Additionally, bioinspired materials facilitate the development of smartphone-assisted biosensing platforms, offering user-friendly and portable diagnostic tools for point-of-care applications. This review comprehensively explores the utilization of naturally occurring and engineered biominerals and materials for diverse biosensing applications. We highlight the fabrication and design strategies that tailor their functionalities to address specific biosensing needs. This in-depth exploration underscores the transformative potential of biominerals and materials in revolutionizing biosensing, paving the way for advancements in healthcare, environmental monitoring, and other critical fields.

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

Biomimetic mineralization based on self-assembling peptides

Biomimetic science has attracted great interest in the fields of chemistry, biology, materials science, and energy. Biomimetic mineralization is the process of synthesizing inorganic minerals under the control of organic molecules or biomolecules under mild conditions. Peptides are the motifs that constitute proteins, and can self-assemble into various hierarchical structures and show a high affinity for inorganic substances. Therefore, peptides can be used as building blocks for the synthesis of functional biomimetic materials. With the participation of peptides, the morphology, size, and composition of mineralized materials can be controlled precisely. Peptides not only provide well-defined templates for the nucleation and growth of inorganic nanomaterials but also have the potential to confer inorganic nanomaterials with high catalytic efficiency, selectivity, and biotherapeutic functions. In this review, we systematically summarize research progress in the formation mechanism, nanostructural manipulation, and applications of peptide-templated mineralized materials. These can further inspire researchers to design structurally complex and functionalized biomimetic materials with great promising applications.

Emerging Trends in Non-Enzymatic Cholesterol Biosensors: Challenges and Advancements

The development of a highly sensitive and selective non-enzymatic electrochemical biosensor for precise and accurate determination of multiple disease biomarkers has always been challenging and demanding. The synthesis of novel materials has provided opportunities to fabricate dependable biosensors. In this perspective, we have presented and discussed recent challenges and technological advancements in the development of non-enzymatic cholesterol electrochemical biosensors and recent research trends in the utilization of functional nanomaterials. This review gives an insight into the electrochemically active nanomaterials having potential applications in cholesterol biosensing, including metal/metal oxide, mesoporous metal sulfide, conductive polymers, and carbon materials. Moreover, we have discussed the current strategies for the design of electrode material and key challenges for the construction of an efficient cholesterol biosensor. In addition, we have also described the current issues related to sensitivity and selectivity in cholesterol biosensing.

Graphene-enabled wearable sensors for healthcare monitoring

Wearable sensors in healthcare monitoring have recently found widespread applications in biomedical fields for their non- or minimal-invasive, user-friendly and easy-accessible features. Sensing materials is one of the major challenges to achieve these superiorities of wearable sensors for healthcare monitoring, while graphene-based materials with many favorable properties have shown great efficiency in sensing various biochemical and biophysical signals. In this paper, we review state-of-the-art advances in the development and modification of graphene-based materials (i.e., graphene, graphene oxide and reduced graphene oxide) for fabricating advanced wearable sensors with 1D (fibers), 2D (films) and 3D (foams/aerogels/hydrogels) macroscopic structures. We summarize the structural design guidelines, sensing mechanisms, applications and evolution of the graphene-based materials as wearable sensors for healthcare monitoring of biophysical signals (e.g., mechanical, thermal and electrophysiological signals) and biochemical signals from various body fluids and exhaled gases. Finally, existing challenges and future prospects are presented in this area.

MXene-based enzymatic sensor for highly sensitive and selective detection of cholesterol

In this work, the synthesized MXene (Ti₃C₂T_x) exhibited large specific area, biocompatibility, excellent electronic conductivity, and good dispersion in aqueous phase. The Chit/ChOx/Ti₃C₂T_x nanocomposite was prepared through the continuous self-assembled process. Its structure is characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Moreover, the biosensor for cholesterol detection was fabricated via a one-step dip-coating method. Chit andTi₃C₂T_x act as a support matrix to immobilize ChOx enzyme, and also play a role in increasing the electrical conductivity. Meanwhile, the addition of redox mediator (Fe(CN)₆^3-/4-) facilitates the electron transport from the analyte to the modified electrode in the oxidation of cholesterol. The DPV response exhibited an increase in current with increasing cholesterol concentration. Under the optimum conditions, the DPV response of the biosensor indicated a good linear relationship with the concentration of cholesterol ranging from 0.3 to 4.5 nM with a low detection limit of 0.11 nM, and a high sensitivity of 132.66 μA nM^-1 cm^-2. In addition, with favorable selectivity and stability, the biosensor has been used to detect cholesterol in real samples and the results demonstrate that the biosensor has excellent practicability.

Fabrication of Hybrid Materials Based on Waste Polyethylene/Porous Activated Metakaolinite Nanocomposite as an Efficient Membrane for Heavy Metal Desalination Processes

Hybrid nanostructure materials derived from activated metakaolinite are of growing importance due to their intriguing structural/functional properties and promising biomedical/environmental applications, especially designing desalination membranes. Herein, we report procedures to design and fabricate membranes based on waste polyethylene/porous activated-metakaolinite thin film nanocomposites (WPE/PAMK-TFN). It has been devoted to improving water desalination processes, where efficient removal of trace level (~250 ppm) of toxic heavy metals such as Cd(II), Pb(II), and Cu(II) ions from synthetic wastewater solutions was highly accomplished. Physicochemical techniques such as X-ray diffraction (XRD), surface analysis (BET), and Fourier transform infrared spectroscopy (FTIR) have been extensively employed to elucidate the structure/composition of the prepared nanomaterials. The effect of concentration (0–0.5 wt%) of porous activated-metakaolinite (PAMK) on water permeation was investigated. The results obtained revealed that 0.5 wt% of PAMK clay particles produced the highest dispersion, as evident by SEM images of the nanocomposite membranes. Significantly, the constructed membrane showed marked improvements in porosity, hydrophilicity, and hydraulic resistance. Moreover, elemental mapping studies have confirmed the intercalation of activated bentonite clay within the polymer matrix. The obtained results demonstrated that increased flux and rejection capability of membranes occurred at high clay dosage. In contrast, the low rejection capability was observed at either lower pH and higher initial feed concentrations. Ultimately, for 250 ppm of Cd(II), Pb(II), and Cu(II) ions, the constructed membranes showed maximum removal capability of 69.3%, 76.2%, and 82.5% of toxic cations, respectively.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

A Surfactant Directed Microcrystalline Cellulose/Polyaniline Composite with Enhanced Electrochemical Properties

In this study a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used as a soft template for in situ chemical polymerization of aniline on the surface of microcrystalline cellulose (MCC). The morphology of the wire-like and porous nanostructure of the resulting composite was highly dependent on the MCC and CTAB concentrations. The effect of the MCC and CTAB concentrations on the electrochemical and morphological properties of the polyaniline (PAni) nanocomposite was studied. Cyclic voltammograms of modified PAni/MCC/CTAB electrode displayed a high current response and the effect of scan rate on the current response confirmed a diffusion controlled process on the surface of the electrode that makes it suitable for sensor applications. The overlapping characteristic peaks of pure PAni and MCC caused peak broadening at 3263 cm^-1 in the IR spectra of PAni/MCC/CTAB nanocomposite that revealed the interaction between NH of PAni and OH group of MCC via electrostatic interactions. The addition of MCC to PAni through chemical polymerization decreased the thermal stability of composite compared to pure PAni. Lower crystallinity was observed in the XRD diffractogram, with 2 theta values of 22.8, 16.5, and 34.6 for PAni/MCC, confirming the formation of PAni on the MCC surface.

Recent advances in designing nanomaterial based biointerfaces for electrochemical biosensing cardiovascular biomarkers

Early diagnosis of cardiovascular disease (CVD) is critically important for successful treatment and recovery of patients. At present, detection of CVD at early stages of its progression becomes a major issue for world health. The nanoscale electrochemical biosensors exhibit diverse outstanding properties, rendering them extremely suitable for the determination of CVD biomarkers at very low concentrations in biological fluids. The unique advantages offered by electrochemical biosensors in terms of sensitivity and stability imparted by nanostructuring the electrode surface together with high affinity and selectivity of bioreceptors have led to the development of new electrochemical biosensing strategies that have introduced as interesting alternatives to conventional methodologies for clinical diagnostics of CVD. This review provides an updated overview of selected examples during the period 2005-2018 involving electrochemical biosensing approaches and signal amplification strategies based on nanomaterials, which have been applied for determination of CVD biomarkers. The studied CVD biomarkers include AXL receptor tyrosine kinase, apolipoproteins, cholesterol, C-reactive protein (CRP), D-dimer, fibrinogen (Fib), glucose, insulin, interleukins, lipoproteins, myoglobin, N-terminal pro-B-type natriuretic peptide (BNP), tumor necrosis factor alpha (TNF-α) and troponins (Tns) on electrochemical transduction format. Identification of new specific CVD biomarkers, multiplex bioassay for the simultaneous determination of biomarkers, emergence of microfluidic biosensors, real-time analysis of biomarkers and point of care validation with high sensitivity and selectivity are the major challenges for future research.

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.

State of the art and recent advances in the ultrasound-assisted synthesis, exfoliation and functionalization of graphene derivatives

Sonochemistry, an almost a century old technique was predominantly employed in the cleaning and extraction processes but this tool has now slowly gained tremendous attention in the synthesis of nanoparticles (NPs) where particles of sub-micron have been produced with great stability. Following this, ultrasonication techniques have been largely employed in graphene synthesis and its dispersion in various solvents which would conventionally take days and offers poor yield. Ultrasonic irradiation allows the production of thin-layered graphene oxide (GO) and reduced graphene oxide (RGO) of up to 1nm thickness and can be produced in single layers. With ultrasonic treatment, reactions were made easy whereby graphite can be directly exfoliated to graphene layers. Oxidation to GO can also be carried out within minutes and reduction to RGO is possible without the use of any reducing agents. In addition, various geometry of graphene can be produced such as scrolled graphene, sponge or foam graphene, smooth as well as those with rough edges, each serving its own unique purpose in various applications such as supercapacitor, catalysis, biomedical, etc. In ultrasonic-assisted reaction, deposition of metal NPs on graphene was more homogeneous with custom-made patterns such as core-shell formation, discs, clusters and specific deposition at the edges of graphene sheets. Graphene derivatives with the aid of ultrasonication are the perfect catalyst for various organic reactions as well as an excellent adsorbent. Reactions which used to take hours and days were significantly reduced to minutes with exceedingly high yields. In a more recent approach, sonophotocatalysis was employed for the combined effect of sonication and photocatalysis of metal deposited graphene. The system was highly efficient in organic dye adsorption. This review provides detailed fundamental concepts of ultrasonochemistry for the synthesis of graphene, its dispersion, exfoliation as well as its functionalization, with great emphasis only based on recent publications. Necessary parameters of sonication such as frequency, power input, sonication time, type of sonication as well as temperature and dual-frequency sonication are discussed in great length to provide an overview of the resultant graphene products.

Polyaniline-modified nanocellulose prepared from Semantan bamboo by chemical polymerization: preparation and characterization

Polyaniline/crystalline nanocellulose (PANi/CNC) was prepared via in situ oxidative polymerization of aniline in the presence of crystalline nanocellulose from Semantan bamboo (Gigantochloa scortechinii).

Amplified detection of leukemia cancer cells using an aptamer-conjugated gold-coated magnetic nanoparticles on a nitrogen-doped graphene modified electrode

The increasing demands for early, accurate and ultrasensitive diagnosis of cancers demonstrate the importance of the development of new amplification strategies or diagnostic technologies. In the present study, an aptamer-based electrochemical biosensor for ultrasensitive and selective detection of leukemia cancer cells has been introduced. The thiolated sgc8c aptamer was immobilized on gold nanoparticles-coated magnetic Fe₃O₄ nanoparticles (Apt-GMNPs). Ethidium bromide (EB), intercalated into the stem of the aptamer hairpin, provides the read-out signal for the quantification of the leukemia cancer cells. After introduction of the leukemia cancer cells onto the Apt-GMNPs, the hairpin structure of the aptamer is disrupted and the intercalator molecules are released, resulting in a decrease of the electrochemical signal. The immobilization of nitrogen-doped graphene nanosheets on the electrode surface provides an excellent platform for amplifying the read-out signal. Under optimal conditions, the aptasensor exhibits a linear response over a wide dynamic range of leukemia cancer cells from 10 to 1×10⁶cellmL^-1. The present protocol provides a highly sensitive, selective, simple, and robust method for early stage detection of leukemia cancer. Furthermore, the fabricated aptasensor was successfully used for the detection of leukemia cancer cells in complex media such as human blood plasma, without any serious interference.

A novel bioassay based gold nanoribbon biosensor to aid the preclinical evaluation of anticancer properties

In this manuscript we have attempted to develop a novel biosensor based on Au nanoribbons (AuNRs). Initially, Quercetin stabilized AuNPs were prepared and dityrosine peptides was used as a structure directing agent for the synthesis of AuNRs.