One-Pot electrochemical fabrication of high performance amperometric enzymatic biosensors using polypyrrole and polydopamine

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.

Conductive Polymers and Their Nanocomposites: Application Features in Biosensors and Biofuel Cells

Conductive polymers and their composites are excellent materials for coupling biological materials and electrodes in bioelectrochemical systems. It is assumed that their relevance and introduction to the field of bioelectrochemical devices will only grow due to their tunable conductivity, easy modification, and biocompatibility. This review analyzes the main trends and trends in the development of the methodology for the application of conductive polymers and their use in biosensors and biofuel elements, as well as describes their future prospects. Approaches to the synthesis of such materials and the peculiarities of obtaining their nanocomposites are presented. Special emphasis is placed on the features of the interfaces of such materials with biological objects.

An ultrasensitive dual-signal ratio electrochemical aptamer biosensor for the detection of HER2

Electrochemical ratiometric biosensors have received attention from researchers because of their self-calibration capability, which can improve the accuracy of detection. In the present study, a ratiometric dual signal electrochemical aptamer biosensor based on ZIF-67 @polydopamine (PDA) nanocomposite and Cu/UiO-66 @ 3, 3', 5, 5'-tetramethylbenzidine (TMB) nanocomposite was fabricated for the detection of breast cancer biomarker- human epidermal growth factor receptor 2 (HER2). PDA was chosen as the electroactive material with electrochemical redox activity and ZIF-67 with a high specific surface area, forming the ZIF-67 @PDA+Apt as the nanoprobe for capturing HER2 in this paper. Cu/UiO-66 is a bimetallic compound with high stability, specific surface area, and strong adsorption onto aptamer chains, and the Cu/UiO-66 @TMB+Apt nanocomposite was used as a probe for signal labeling. In the presence of HER2, the capture of HER2 by the ZIF-67 @PDA+Apt probe results in a weakening of the conductivity of the electrode, however, by attenuating the electrochemical signal from the PDA, altering the probe-Cu/UiO-66 @TMB+Apt signaling will result in the enhancement of the TMB electrochemical signal. With a sensitive detection of HER2 biomarkers in as little as 30 min with the detection range of 0.75-40 pg/mL and a limit of detection as low as 44.8 fg/mL. Dual signal ratio biosensors have a low limit of detection, short detection time, which can accurately detect targets in complex biological samples, which has important theoretical importance.

What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective.

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⁺.