Enzyme (Single and Multiple) and Nanozyme Biosensors: Recent Developments and Their Novel Applications in the Water-Food-Health Nexus

When nanozymes meet enzyme: Unlocking the dual-activity potential of integrated biocomposites

Integrating enzymes and nanozymes in various applications is a topic of significant interest. The researchers have explored the encapsulation of enzymes using diverse nanostructures to create nanomaterial-enzyme hybrids. These nanomaterials introduce unique properties that contribute to the additional activity along with the stabilization of enzymes in immobilized form, enabling a cascade of second-order reactions. This review centers on dual-activity nanozymes, providing insights into their applications in biosensors and biocatalysis. These applications leverage the enhanced catalytic activity and stability offered by dual-activity nanozymes. These nanozymes find promising applications in fields like bioremediation, offering eco-friendly solutions for mitigating environmental pollution while showing potential in medical diagnostics. The review delves into various techniques for creating enzyme-nanozyme hybrid catalysts, including adsorption, encapsulation, and incorporation methods. The review also addresses the challenges that must be overcome, such as overlapping catalytic surfaces and disparities in reaction rates in multi-enzyme cascade reactions. It concludes by presenting strategies to tackle these issues and offers insights into the field's promising future, suggesting that machine learning may drive further advancements in enzyme-nanozyme integration. This comprehensive exploration illuminates the present and charts a promising course for future innovations in the seamless integration of enzymes and nanozymes, heralding a new era of catalytic possibilities.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

Design and application of histidine-functionalized ZnCr-LDH nanozyme for promoting bacteria-infected wound healing

Excessive use of antibiotics can lead to an increase in antibiotic-resistant bacteria, which makes it a serious health threat. Therefore, developing new materials with antibacterial activity, such as nanozymes, has gained considerable attention. Reactive oxygen species (ROS) produced by nanozymes have rapid and effective antibacterial efficacy. Here, histidine (His) modified ZnCr layered double hydroxide (LDH) was synthesized inspired by the natural enzyme, and the enzyme-like activity of His/ZnCr-LDH was tested using a colorimetric method. Then, we developed an acid-enhanced antibacterial method based on the high peroxidase-like activity of His/ZnCr-LDH, and its ROS-generating capability in the presence of glucose oxidase (GOx) and glucose (Glu) as a source of hydrogen peroxide (H2O2). Gluconic acid (GA), the main product of the GOx reaction, provides an acidic environment and promotes ROS generation. The mentioned strategy shows high antibacterial activity at a low minimum inhibitory concentration (MIC) which represents the potential of His/ZnCr-LDH for effective bacterial elimination (3.5 μg mL-1 for S. aureus and 6 μg mL-1 for E. coli). In addition, animal experiments illustrated that the His/ZnCr-LDH can successfully boost the curing of infected wounds. The outcomes indicate that amino acid modified LDHs offer a new strategy for effective bacterial removal in different medical applications.

Metal-organic frameworks for enzyme immobilization and nanozymes: A laccase-focused review

Laccases are natural catalysts with remarkable catalytic activity. However, their application is limited by their lack of stability. Metal-organic frameworks (MOFs) have emerged as a promising alternative for enzyme immobilization. Enzymes can be immobilized in MOFs via two approaches: postsynthetic immobilization and in situ immobilization. In postsynthetic immobilization, an enzyme is embedded after MOF formation by covalent interactions or adsorption. In contrast, in in situ immobilization, a MOF is formed in the presence of an enzyme. Additionally, MOFs have exhibited intrinsic enzyme-like activity. These materials, known as nanozymes when they have the ability to replace enzymes in certain catalytic processes, have multiple key advantages, such as low cost, easy preparation, and large surface areas. This review presents a general overview of the most recent advances in both enzyme@MOF biocatalysts and MOF-based nanozymes in different applications, with a focus on laccase, which is one of the most widely investigated enzymes with excellent industrial potential.

Principles, Methods, and Real-Time Applications of Bacteriophage-Based Pathogen Detection

Bacterial pathogens in water, food, and the environment are spreading diseases around the world. According to a World Health Organization (WHO) report, waterborne pathogens pose the most significant global health risks to living organisms, including humans and animals. Conventional bacterial detection approaches such as colony counting, microscopic analysis, biochemical analysis, and molecular analysis are expensive, time-consuming, less sensitive, and require a pre-enrichment step. However, the bacteriophage-based detection of pathogenic bacteria is a robust approach that utilizes bacteriophages, which are viruses that specifically target and infect bacteria, for rapid and accurate detection of targets. This review shed light on cutting-edge technologies about the novel structure of phages and the immobilization process on the surface of electrodes to detect targeted bacterial cells. Similarly, the purpose of this study was to provide a comprehensive assessment of bacteriophage-based biosensors utilized for pathogen detection, as well as their trends, outcomes, and problems. This review article summaries current phage-based pathogen detection strategies for the development of low-cost lab-on-chip (LOC) and point-of-care (POC) devices using electrochemical and optical methods such as surface-enhanced Raman spectroscopy (SERS).

Immobilization of Enzyme Electrochemical Biosensors and Their Application to Food Bioprocess Monitoring

Electrochemical biosensors based on immobilized enzymes are among the most popular and commercially successful biosensors. The literature in this field suggests that modification of electrodes with nanomaterials is an excellent method for enzyme immobilization, which can greatly improve the stability and sensitivity of the sensor. However, the poor stability, weak reproducibility, and limited lifetime of the enzyme itself still limit the requirements for the development of enzyme electrochemical biosensors for food production process monitoring. Therefore, constructing sensing technologies based on enzyme electrochemical biosensors remains a great challenge. This article outlines the construction principles of four generations of enzyme electrochemical biosensors and discusses the applications of single-enzyme systems, multi-enzyme systems, and nano-enzyme systems developed based on these principles. The article further describes methods to improve enzyme immobilization by combining different types of nanomaterials such as metals and their oxides, graphene-related materials, metal-organic frameworks, carbon nanotubes, and conducting polymers. In addition, the article highlights the challenges and future trends of enzyme electrochemical biosensors, providing theoretical support and future perspectives for further research and development of high-performance enzyme chemical biosensors.

Plant Protein-Peptide Supramolecular Polymers with Reliable Tissue Adhesion for Surgical Sealing

The fusion of protein science and peptide science opens up new frontiers in creating innovative biomaterials. Herein, a new kind of adhesive soft materials based on a natural occurring plant protein and short peptides via a simple co-assembly route are explored. The hydrophobic zein is supercharged by sodium dodecyl sulfate to form a stable protein colloid, which is intended to interact with charge-complementary short peptides via multivalent ionic and hydrogen bonds, forming adhesive materials at macroscopic level. The adhesion performance of the resulting soft materials can be fine-manipulated by customizing the peptide sequences. The adhesive materials can resist over 78 cmH2 O of bursting pressure, which is high enough to meet the sealing requirements of dural defect. Dural sealing and repairing capability of the protein-peptide biomaterials are further identified in rat and rabbit models. In vitro and in vivo assays demonstrate that the protein-peptide adhesive shows excellent anti-swelling property, low cell cytotoxicity, hemocompatibility, and inflammation response. In particular, the protein-peptide supramolecular biomaterials can in vivo dissociate and degrade within two weeks, which can well match with the time-window of the dural repairing. This work underscores the versatility and availability of the supramolecular toolbox in the easy-to-implement fabrication of protein-peptide biomaterials.

Multivariate Optimization of Electrochemical Biosensors for the Determination of Compounds Related to Food Safety-A Review

We summarize the application of multivariate optimization for the construction of electrochemical biosensors. The introduction provides an overview of electrochemical biosensing, which is classified into catalytic-based and affinity-based biosensors, and discusses the most recent published works in each category. We then explore the relevance of electrochemical biosensors for food safety analysis, taking into account analytes of different natures. Then, we describe the chemometrics tools used in the construction of electrochemical sensors/biosensors and provide examples from the literature. Finally, we carefully discuss the construction of electrochemical biosensors based on design of experiments, including the advantages, disadvantages, and future perspectives of using multivariate optimization in this field. The discussion section offers a comprehensive analysis of these topics.

Two-Dimensional Transition Metal Dichalcogenide Tunnel Field-Effect Transistors for Biosensing Applications

Field-effect transistor (FET) biosensors based on two-dimensional (2D) materials have drawn significant attention due to their outstanding sensitivity. However, the Boltzmann distribution of electrons imposes a physical limit on the subthreshold swing (SS), and a 2D-material biosensor with sub-60 mV/dec SS has not been realized, which hinders further increase of the sensitivity of 2D-material FET biosensors. Here, we report tunnel FETs (TFETs) based on a SnSe₂/WSe₂ heterostructure and observe the tunneling effect of a 2D material in aqueous solution for the first time with an ultralow SS of 29 mV/dec. A bilayer dielectric (Al₂O₃/HfO₂) and graphene contacts, which significantly reduce the leakage current in solution and contact resistance, respectively, are crucial to the realization of the tunneling effect in solution. Then, we propose a novel biosensing method by using tunneling current as the sensing signal. The TFETs show an extremely high pH sensitivity of 895/pH due to ultralow SS, surpassing the sensitivity of FET biosensors based on a single 2D material (WSe₂) by 8-fold. Specific detection of glucose is realized, and the biosensors show a superb sensitivity (3158 A/A for 5 mM), wide sensing range (from 10^-9 to 10^-3 M), low detection limit (10^-9 M), and rapid response rate (11 s). The sensors also exhibit the ability of monitoring glucose in complex biofluid (sweat). This work provides a platform for ultrasensitive biosensing. The discovery of the tunneling effect of 2D materials in aqueous solution may stimulate further fundamental research and potential applications.

Enzymatic Electrochemical/Fluorescent Nanobiosensor for Detection of Small Chemicals

The detection of small molecules has attracted enormous interest in various fields, including the chemical, biological, and healthcare fields. In order to achieve such detection with high accuracy, up to now, various types of biosensors have been developed. Among those biosensors, enzymatic biosensors have shown excellent sensing performances via their highly specific enzymatic reactions with small chemical molecules. As techniques used to implement the sensing function of such enzymatic biosensors, electrochemical and fluorescence techniques have been mostly used for the detection of small molecules because of their advantages. In addition, through the incorporation of nanotechnologies, the detection property of each technique-based enzymatic nanobiosensors can be improved to measure harmful or important small molecules accurately. This review provides interdisciplinary information related to developing enzymatic nanobiosensors for small molecule detection, such as widely used enzymes, target small molecules, and electrochemical/fluorescence techniques. We expect that this review will provide a broad perspective and well-organized roadmap to develop novel electrochemical and fluorescent enzymatic nanobiosensors.

Advanced Nanomaterials-Based Electrochemical Biosensors for Catecholamines Detection: Challenges and Trends

Catecholamines, including dopamine, epinephrine, and norepinephrine, are considered one of the most crucial subgroups of neurotransmitters in the central nervous system (CNS), in which they act at the brain's highest levels of mental function and play key roles in neurological disorders. Accordingly, the analysis of such catecholamines in biological samples has shown a great interest in clinical and pharmaceutical importance toward the early diagnosis of neurological diseases such as Epilepsy, Parkinson, and Alzheimer diseases. As promising routes for the real-time monitoring of catecholamine neurotransmitters, optical and electrochemical biosensors have been widely adopted and perceived as a dramatically accelerating development in the last decade. Therefore, this review aims to provide a comprehensive overview on the recent advances and main challenges in catecholamines biosensors. Particular emphasis is given to electrochemical biosensors, reviewing their sensing mechanism and the unique characteristics brought by the emergence of nanotechnology. Based on specific biosensors' performance metrics, multiple perspectives on the therapeutic use of nanomaterial for catecholamines analysis and future development trends are also summarized.

Biogenic Selenium Nanoparticles in Biomedical Sciences: Properties, Current Trends, Novel Opportunities and Emerging Challenges in Theranostic Nanomedicine

Selenium is an important dietary supplement and an essential trace element incorporated into selenoproteins with growth-modulating properties and cytotoxic mechanisms of action. However, different compounds of selenium usually possess a narrow nutritional or therapeutic window with a low degree of absorption and delicate safety margins, depending on the dose and the chemical form in which they are provided to the organism. Hence, selenium nanoparticles (SeNPs) are emerging as a novel therapeutic and diagnostic platform with decreased toxicity and the capacity to enhance the biological properties of Se-based compounds. Consistent with the exciting possibilities offered by nanotechnology in the diagnosis, treatment, and prevention of diseases, SeNPs are useful tools in current biomedical research with exceptional benefits as potential therapeutics, with enhanced bioavailability, improved targeting, and effectiveness against oxidative stress and inflammation-mediated disorders. In view of the need for developing eco-friendly, inexpensive, simple, and high-throughput biomedical agents that can also ally with theranostic purposes and exhibit negligible side effects, biogenic SeNPs are receiving special attention. The present manuscript aims to be a reference in its kind by providing the readership with a thorough and comprehensive review that emphasizes the current, yet expanding, possibilities offered by biogenic SeNPs in the biomedical field and the promise they hold among selenium-derived products to, eventually, elicit future developments. First, the present review recalls the physiological importance of selenium as an oligo-element and introduces the unique biological, physicochemical, optoelectronic, and catalytic properties of Se nanomaterials. Then, it addresses the significance of nanosizing on pharmacological activity (pharmacokinetics and pharmacodynamics) and cellular interactions of SeNPs. Importantly, it discusses in detail the role of biosynthesized SeNPs as innovative theranostic agents for personalized nanomedicine-based therapies. Finally, this review explores the role of biogenic SeNPs in the ongoing context of the SARS-CoV-2 pandemic and presents key prospects in translational nanomedicine.

Convenient site-selective protein coupling from bacterial raw lysates to coenzyme A-modified tobacco mosaic virus (TMV) by Bacillus subtilis Sfp phosphopantetheinyl transferase

A facile enzyme-mediated strategy enables site-specific covalent one-step coupling of genetically tagged luciferase molecules to coenzyme A-modified tobacco mosaic virus (TMV-CoA) both in solution and on solid supports. Bacillus subtilis surfactin phosphopantetheinyl transferase Sfp produced in E. coli mediated the conjugation of firefly luciferase N-terminally extended by eleven amino acids forming a 'ybbR tag' as Sfp-selective substrate, which even worked in bacterial raw lysates. The enzymes displayed on the protein coat of the TMV nanocarriers exhibited high activity. As TMV has proven a beneficial high surface-area adapter template stabilizing enzymes in different biosensing layouts in recent years, the use of TMV-CoA for fishing ybbR-tagged proteins from complex mixtures might become an advantageous concept for the versatile equipment of miniaturized devices with biologically active proteins. It comes along with new opportunities for immobilizing multiple functionalities on TMV adapter coatings, as desired, e.g., in handheld systems for point-of-care detection.

Progress and current trends in the electrochemical determination of phosphate ions for environmental and biological monitoring applications

The determination of phosphate ions in biological testing is critical for environmental safety. A reliable and accurate method is required to measure the true phosphate ion concentrations; in this regard, the electrochemical method is preferable because of its simple operation, fast response, and high sensitivity. By compiling existing electroanalytical techniques, researchers can compare the advantages and disadvantages of each method. This review examines the progress and recent advances in electrochemical sensing strategies adapted for the determination of phosphate ions in the environmental and during biological monitoring. We first discuss the history of phosphorus and the development of methods to detect phosphates. The recognition elements of phosphate ion sensors for environmental applications include metal-based, nanomaterial-based, carbon-based, and enzymatic electrodes. Phosphate determination in biological samples, such as blood serum, drugs, and other biological fluids, such as urine and saliva, as well as phosphate esters, is also discussed. The final part of our review addresses the current challenges that phosphate sensing technology faces and illustrates future opportunities for more reliable phosphate detection.

Nanomaterials-based portable electrochemical sensing and biosensing systems for clinical and biomedical applications

Miniaturized electrochemical sensing systems are employed in day-to-day uses in the several area from public health to scientific applications. A variety of electrochemical sensor and biosensor systems may not be effectively employed in real-world diagnostic laboratories and biomedical industries due to their limitation of portability, cost, analytical period, and need of skilled trainer for operating devices. The design of smart and portable sensors with high sensitivity, good selectivity, rapid measurement, and reusable platforms is the driving strength for sensing glucose, lactate, hydrogen peroxide, nitric oxide, mRNA, etc. The enhancement of sensing abilities of such sensor devices through the incorporation of both novel sensitive nanomaterials and design of sensor strategies are evidenced. Miniaturization, cost and energy efficient, online and quantitative detection and multiple sensing ability are the beneficial of the nanostructured-material-based electrochemical sensor and biosensor systems. Owing to the discriminating catalytic action, solidity and biocompatibility for designing sensing system, nanoscale materials empowered electrochemical detection systems are accomplished of being entrenched into/combined with portable or miniaturized devices for specific applications. In this review, the advance development of portable and smart sensing/biosensing systems derived from nanoscale materials for clinical and biomedical applications is described.

Graphical Abstract

A performance improvement of enzyme-based electrochemical lactate sensor fabricated by electroplating novel PdCu mediator on a laser induced graphene electrode

A lactate sensor for lactate sensing using porous laser-induced graphene (LIG) electrodes with an electrodeposited PdCu catalyst was developed in this study. CO₂ laser was used to convert the polyimide film surface to multilayered LIG. The morphology and composition of LIG were analyzed through field-emission scanning electron microscopy and Raman spectroscopy, respectively, to confirm that the fabricated LIG electrode was composed of porous and stacked graphene layers. PdCu was electrodeposited on the LIG electrode and lactate oxidase (LOx) was immobilized on the LIG surface to create a LOx/PdCu/LIG structure. According to the Randles-Ševčík equation, the calculated active surface area of the fabricated PdCu/LIG electrode was ∼12.8 mm², which was larger than the apparent area of PdCu/LIG (1.766 mm²) by a factor of 7.25. The measured sensitivities of the fabricated lactate sensors with the LOx/PdCu/LIG electrode were -51.91 μA/mM·cm² (0.1-5 mM) and -17.18 μA/mM·cm² (5-30 mM). The calculated limit of detection was 0.28 μM. The selectivity of the fabricated lactate sensor is excellent toward various potentially interfering materials such as ascorbic acid, uric acid, lactose, sucrose, K⁺ and Na⁺.

Nanomaterials in bioelectrochemical devices: on applications enhancing their positive effect

Electrochemical biosensors and biofuel cells are finding an ever-increasing practical application due to several advantages. Biosensors are miniature measuring devices, which can be used for on-the-spot analyses, with small assay times and sample volumes. Biofuel cells have dual benefits of environmental cleanup and electric energy generation. Application of nanomaterials in biosensor and biofuel-cell devices increases their functioning efficiency and expands spheres of use. This review discusses the potential of nanomaterials in improving the basic parameters of bioelectrochemical systems, including the sensitivity increase, detection lower-limit decrease, detection-range change, lifetime increase, substrate-specificity control. In most cases, the consideration of the role of nanomaterials links a certain type of nanomaterial with its effect on the bioelectrochemical device upon the whole. The review aims at assessing the effects of nanomaterials on particular analytical parameters of a biosensor/biofuel-cell bioelectrochemical device.

MWCNTs-CTAB and HFs-Lac Nanocomposite-Modified Glassy Carbon Electrode for Rutin Determination

Rutin is a flavonoid glycoside compound, which is mainly transported via the blood circulation system in the human body. The monitoring of the blood concentration of rutin is of great significance in many fields such as pharmacology and pharmacokinetics. In this work, a biosensor based on multi-walled carbon nanotubes (MWCNTs), cetyltrimethylammonium bromide (CTAB), hydroxyl fullerenes (HFs), and laccase (Lac) nanocomposite-modified glassy carbon electrodes was constructed. The modified materials were characterized with a transmission electron microscope (TEM), cyclic voltammograms (CV), and electrochemical impedance spectroscopy (EIS). CTAB is used to disperse MWCNTs and improve hydrophilicity and biocompatibility of MWCNTs, while the use of Lac can enhance the oxidation of catechol structure in rutin, thus significantly improving the sensitivity and selectivity of the modified electrode. Linear sweep voltammetry (LSV) studies showed that the determination linear ranges of rutin were 0.1 µmol L⁻¹ to 2 µmol L⁻¹ and 2 µmol L⁻¹ to 11 µmol L⁻¹, with the determination limits of 30 nmol L⁻¹ and 95.5 nmol L⁻¹, respectively. The proposed biosensor can be used to detect rutin tablets and serum samples with high recovery, which indicates a good accuracy of this method, and the results are consistent with those measured by the traditional ultra-high performance liquid chromatography (UHPLC) method. Hence, this biosensor has potential practical application value in rutin drug quality testing and clinical blood drug concentration monitoring.

Cheap and Sustainable Biosensor Fabrication by Enzyme Immobilization in Commercial Polyacrylic Acid/Carbon Nanotube Films

Novel glucose biosensors were constructed by loading glucose oxidase (GOx) into the nanopores of homogenous carbon nanotube (CNT) films on the surface of Pt disk electrodes and trapping the enzyme by subsequent deposition of polyacrylic acid (PAA), forming PAA/GOx-CNT-modified Pt disks. In amperometric biosensing with anodic hydrogen peroxide (H₂O₂) detection at a potential of +600 mV, increasing electrolyte glucose concentrations produced instantaneous steps in the H₂O₂ oxidation current. Glucose biosensor amperometry was feasible down to 10 μM, with a sensitivity of about 34 μA mM^-1 cm^-2 and linear current response up to 5 mM. The biosensors reliably determined glucose concentrations in human serum and a beverage. Successful trials with PAA/GOx-CNT-modified screen-printed Pt electrode disks demonstrated the potential of this means of enzyme fixation in biosensor mass fabrication, which offers a unique combination of cheap availability of the two matrix constituents and sensor layer formation through simple drop-and-dry steps. PAA/GOx-CNT/Pt biosensors are green and user-friendly bioanalytical tools that do not need large budgets, special skills, or laboratory amenities for their production. Any user, from industrial, university, or school laboratories, even if inexperienced in biosensor construction, can prepare functional biosensors with GOx, as in these proof-of-principle studies, or with other redox enzymes, for clinical, environmental, pharmaceutical, or food sample analysis.

Prussian Blue Nanoparticle Supported MoS2 Nanocomposites as a Peroxidase-Like Nanozyme for Colorimetric Sensing of Dopamine

An abnormal level of dopamine (DA) is usually related to neurological disorders, including Parkinson's disease. Herein, cubic-shaped, Prussian blue nanoparticle-supported MoS2 nanocomposites (MoS2-CPBNPs) were prepared as peroxidase-like nanozymes for the label-free, colorimetric detection of DA. As expected, the as-prepared MoS2-CPBNPs nanozymes have outstanding peroxidase-like mimicking activity, which can catalyze 3,3',5,5'-Tetramethylbenzidine (TMB) to generate blue, oxidized TMB in the presence of hydrogen peroxide (H2O2). DA can inhibit the oxidation of TMB, which causes blue solutions to fade and become colorless. According to this phenomenon, the developed colorimetric sensor can qualitatively and quantitatively analyze DA ranging from 0 to 300 μM with a detection limit of 0.09 μM. In addition, the high recovery and low relative standard deviation for practical DA determination suggested that this colorimetric sensor has potential for application in biological biosensing and diagnostic fields.

Determination of Drugs in Clinical Trials: Current Status and Outlook

All pharmaceutical drugs, vaccines, cosmetic products, and many medical breakthroughs must first be approved through clinical research and trials before advancing to standard practice or entering the marketplace. Clinical trials are sets of tests that are required to determine the safety and efficacy of pharmaceutical compounds, drugs, and treatments. There is one pre-phase and four main clinical phase requirements that every drug must pass to obtain final approval. Analytical techniques play a unique role in clinical trials for measuring the concentrations of pharmaceutical compounds in biological matrices and monitoring the conditions of patients (or volunteers) during various clinical phases. This review focuses on recent analytical methods that are employed to determine the concentrations of drugs and medications in biological matrices, including whole blood, plasma, urine, and breast milk. Four primary analytical techniques (extraction, spectroscopy, chromatography, and electrochemical) are discussed, and their advantages and limitations are assessed. Subsequent to a survey of evidence and results, it is clear that microelectromechanical system (MEMS) based electrochemical sensor and biosensor technologies exhibit several notable advantages over other analytical methods, and their future prospects are discussed.

An Enzymatic Biosensor for the Detection of D-2-Hydroxyglutaric Acid in Serum and Urine

D-2-hydroxyglutaric acid (D2HG) is overproduced as a result of the D-2-hydroxyglutaric aciduria and relevant cancers, caused by gene mutation. Accurate analysis of D2HG could help rapid diagnosis of these diseases and allow for timely treatment. In this work, a D-2-hydroxyglutarate dehydrogenase from Ralstonia solanacearum (RsD2HGDH) is cloned and recombinantly expressed. This enzyme features the direct electron transfer to chemical electron mediators (such as methylene blue (MB)) in the absence of additional coenzymes. Therefore, NAD⁺, a natural electron acceptor for the commercial D2HGDH and usually known for being unstable and difficult for immobilization can be avoided in the preparation of biosensors. The RsD2HGDH and MB are co-immobilized on a two-dimensional material, Ti₃C₂ MXene, followed by drop-coating on the gold screen-printed electrode (AuSPE) to construct a compact and portable biosensor. The D2HG in samples can be catalyzed by RsD2HGDH, where the current change is measured by chronoamperometry at -0.23 V. The biosensor shows a D2HG detection range of 0.5 to 120 µM (R² = 0.9974) with a sensitivity of 22.26 μA mM^-1 cm^-2 and a detection limit of 0.1 µM (S/N = 3). The biosensor retains 72.52% performance of its incipient state after 30 days of storage. The samples of D2HG-containing fetal bovine serum and artificial urine were analyzed with the recovery of 99.56% to 106.83% and 97.30% to 102.47% further indicating the great application potential of our portable D2HG biosensor.

Hollow spheres of iron oxide as an “enzyme-mimic”: preparation, characterization and application as biosensors

Nanostructured hollow spheres of iron oxide are demonstrated as “nanozymes” for the dual mode (spectrophotometric and electrochemical) detection of hydrogen peroxide & cholesterol biomarkers and a novel electrochemical sensing mechanism is proposed.

Nanozyme-based sensors for detection of food biomarkers: a review

Nanozymes have piqued the curiosity of scientists in recent years because of their ability to demonstrate enzyme-like activity combined with advantages such as high stability, inexpensive availability, robust activity, and tunable properties. These attributes have allowed the successful application of nanozymes in sensing to detect various chemical and biological target analytes, overcoming the shortcomings of conventional detection techniques. In this review, we discuss recent developments of nanozyme-based sensors to detect biomarkers associated with food quality and safety. First, we present a brief introduction to this topic, followed by discussing the different types of sensors used in food biomarker detection. We then highlight recent studies on nanozyme-based sensors to detect food markers such as toxins, pathogens, antibiotics, growth hormones, metal ions, additives, small molecules, and drug residues. In the subsequent section, we discuss the challenges and possible solutions towards the development of nanozyme-based sensors for application in the food industry. Finally, we conclude the review by discussing future perspectives of this field towards successful detection and monitoring of food analytes.

We present a discussion on different types of sensors used in food biomarker detection and highlight recent studies on nanozyme-based sensors to detect markers like toxins, pathogens, antibiotics, growth hormones, metal ions, additives, small molecules, drug residues.