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Efforts to engineer artificial allosteric systems are ongoing. Here the authors analyse factors influencing development of artificial small molecule:protein complexes that act as chemically induced dimerization (CID) systems; they use one of the CIDs to construct an electrochemical biosensor of methotrexate.

In addressing the demand for biocompatible wearable, implantable and injectable biomedical devices, alginate hydrogels stand out as promising candidates. Alginate hydrogels have been used as matrix for immobilization of proteins, responsive polymers and nanomaterials that lead to a wide range of stimuli-responsive “smart” (bio)(nano)composite hydrogels. In this perspective, we analyzed the most recent applications of “smart” alginate composite hydrogels in biomedical applications, such as biosensing, drug delivery, wound healing and biocomputing. The design and key-responsive element of the composites were discussed as well as their practical application in biologically relevant conditions and in vivo. Finally, we provide our insights into the limitations, challenges and future directions of this exciting research field.

Here, we describe a multianalyte biosensor platform for the fluorescent analysis of different human state biomarkers (α-amylase, phenylalanine, glucose, lactate/pyruvate, alcohol) and some immunosuppressive drugs (cyclosporine A, tacrolimus, methotrexate, rapamycin) using chimeric PQQ- and natural NAD+-dependent enzymes. The principle of the approach is based on the analysis of the brightness of photography of a sensor plate taken with a smartphone camera and processed using ImageJ software. The brightness of the image correlates with the fluorescence intensity of the sensor’s spots which is produced by the enzymatic reduction of phenazine methosulfate or its derivative used as a fluorescence probe at UV 356 nm irradiation, where the amount of the reduced dye depends on the concentration of the target analyte (the enzymatic substrate) in the tested sample. The sensor plate is composed of simple and cheap components, and the procedure of its preparation and usage is easy and does not require any specific skills or expensive instrumentation. The proposed sensor platform is characterized by a high selectivity and storage stability depending on the selectivity and stability characteristics of the used enzyme in an immobilized state. The proposed sensor platform could be used for precision quantitative analysis of a single (or several) analytes or used for a simultaneous qualitative multianalyte assay of them using Boolean logic gates.

This review provides a general overview of different biosensors, mostly concentrating on electrochemical analytical devices, while briefly explaining general approaches to various kinds of biosensors, their construction and performance. A discussion on how all required components of biosensors are brought together to perform analytical work is offered. Different signal-transducing mechanisms are discussed, particularly addressing the immobilization of biomolecular components in the vicinity of a transducer interface and their functional integration with electronic devices. The review is mostly addressing general concepts of the biosensing processes rather than specific modern achievements in the area.

The DNA-release activated by light in the self-powered bioelectronic system has been studied. The system was composed of two connected electrodes: one photo-active electrode was modified with photosynthetic thylakoid membranes and another electrode was modified with O2-reducing bilirubin oxidase and nanoparticles functionalized with molecules changing their charge upon pH variation. When the photo-electrode was illuminated, it produced current resulting in O2 reduction and local pH change at the releasing electrode. The interfacial charge was changed from positive, when negatively charged DNA was loaded, to negative, when the DNA was repulsed and released.

Precision analysis of the key biological metabolites such as L-lactate has great practical importance for many technological processes in food technology, including beverage production. Here we describe a new, highly selective, and sensitive biosensor for accurate L-lactate assay based on a combination of peroxidase-mimetic nanozymes with microbial lactate oxidase (LOx) immobilized onto the surface of a graphite-rod electrode (GE). The peroxidase-like nanozymes were synthesized using the debris of carbon microfibers (CFs) functionalized with hemin (H) and modified with gold nanoparticles (AuNPs) or platinum microparticles (PtMPs). The nanozyme formed with PtMPs as well as corresponding bioelectrodes based on it (LOx-CF-H-PtMPs/GE) is characterized by preferable catalytic and operational characteristics, so it was selected for the analysis of L-lactate content in real samples of grape must and red wine. The results of the L-lactate analysis obtained by the developed biosensors are highly correlated with a very selective spectrophotometric approach used as a reference. The developed biosensor, due to its high selectivity and sensitivity, is very prospective not only for the beverage industry and food technology, but also for clinical diagnostics and medicine, as well as in other applications where the accurate analysis of L-lactate is highly important.

Biosensors are analytical devices that are able to convert a biological response into an electrical signal [...]

This review summarizes the fundamentals of the phenomenon of electron transfer (ET) reactions occurring in redox enzymes that were widely employed for the development of electroanalytical devices, like biosensors, and enzymatic fuel cells (EFCs). A brief introduction on the ET observed in proteins/enzymes and its paradigms (e.g., classification of ET mechanisms, maximal distance at which is observed direct electron transfer, etc.) are given. Moreover, the theoretical aspects related to direct electron transfer (DET) are resumed as a guideline for newcomers to the field. Snapshots on the ET theory formulated by Rudolph A. Marcus and on the mathematical model used to calculate the ET rate constant formulated by Laviron are provided. Particular attention is devoted to the case of glucose oxidase (GOx) that has been erroneously classified as an enzyme able to transfer electrons directly. Thereafter, all tools available to investigate ET issues are reported addressing the discussions toward the development of new methodology to tackle ET issues. In conclusion, the trends toward upcoming practical applications are suggested as well as some directions in fundamental studies of bioelectrochemistry.

Magnetic nanoparticles are a class of nanoparticle that can be manipulated using magnetic fields [...]

Magnetic nanoparticles and magnetic nano-species of complex topology (e.g., nanorods, nanowires, nanotubes, etc.) are overviewed briefly in the paper, mostly giving attention to the synthetic details and particle composition (e.g., core-shell structures made of different materials). Some aspects related to applications of magnetic nano-species are briefly discussed. While not being a comprehensive review, the paper offers a large collection of references, particularly useful for newcomers in the research area.

Theranostics of cancer using smart biocompatible materials can enable early cancer diagnostics and treatment. Here, we report on a DNA-nanoparticle functional material, which can simultaneously report the presence of an mRNA cancer biomarker and trigger its degradation in cultured cells. The nanodevice consists of two species of magnetic beads, each of which is conjugated with different components of a multicomponent deoxyribozyme (DZ) sensor. The system is activated only under two conditions: (i) in the presence of a specific target mRNA and (ii) when a magnetic field is applied. We demonstrate that delivery of such a system is markedly enhanced by the application of a magnetic field. The system not only fluorescently detects target mRNA in cultured MCF-7 cancer cells, but also induces its downregulation. Thus, the two-component magnetic nanoparticle system has characteristics of a material that can be used for cancer theranostics.

Measuring telomerase activity has proven successful for the determination of cancer in malignant somatic cells. Early conventional methods for the detection of telomerase activity include in vitro analysis via a primer extension assay, and the telomeric repeat amplification protocol (TRAP) assay. TRAP incorporates the polymerase chain reaction (PCR) step to increase the sensitivity of a given sample. However, research suggests that the TRAP technique suffers from false negative results, caused by failure of its PCR step. Other limitations of TRAP include the post-PCR steps involving polyacrylamide gel electrophoresis which are time inefficient. Thus, various efforts have been made to eliminate the PCR step of TRAP by using a variety of biosensor detection devices. This review mainly focuses on these alternatives including: optical, electrochemical, magnetic, and nanowire conductive signaling techniques to measure the telomerase activity produced via label free biosensor assay—via biocatalytic labels involving beacons, DNAzyme, ferrocenyl-naphthalene diimides, avidin-alkaline phosphatase and semiconductor quantum dots (QDs). These biosensor techniques are sensitive and provide precise and rapid results in the detection of telomerase activity.

A new approach to bioelectronic Sense-and-Act systems was developed with the use of modified electrodes performing sensing and substance-releasing functions. [...]

We consider flow systems that have been utilized for small-scale biomolecular computing and digital signal processing in binary-operating biosensors. Signal measurement is optimized by designing a flow-reversal cuvette and analyzing the experimental data to theoretically extract the pulse shape, as well as reveal the level of noise it possesses. Noise reduction is then carried out numerically. We conclude that this can be accomplished physically via the addition of properly designed well-mixing flow-reversal cell(s) as an integral part of the flow system. This approach should enable improved networking capabilities and potentially not only digital but analog signal-processing in such systems. Possible applications in complex biocomputing networks and various sense-and-act systems are discussed.