Special Issue “World of Biosensing”

1. Introduction

The broad definition of the term biosensing relates to practically all processes of molecular recognition. Owing to the unique selectivity of such recognition, molecular interactions between DNA–DNA, DNA–RNA, DNA/RNA–regulatory proteins, enzymes–substrates (as well as co-enzymes, inhibitors, effectors), hormones–receptors, antigens–antibodies, etc. are fundamental to life [1]. Undoubtedly, unique evolutionary-derived molecular recognition processes have been used for analytical purposes, namely for construction of biosensors.

A commonly cited definition of a “biosensing” only focuses on analytical aspects of the field. (Bio)sensors are devices which are based on selective (bio)recognition-enabling sensitive monitoring and measurement of target analytes or processes by converting biological or chemical responses into corresponding signals [2]. In the last decades, (bio)sensors have caused revolutionary changes in analytical chemistry, replacing the complex and tedious traditional methods of analysis with fast, selective, and accurate measurements of responses to specific analytes and processes. The main applications of (bio)sensors are in medicine (clinical and patient care diagnostics, control for therapy); pharmacy (drug development and monitoring); agriculture; water and environmental monitoring; biodefense and military security; and the food industry (quality and safety of products and beverages) [3,4,5].

The majority of biosensors are based on biochemical recognition elements, including enzymes, antibodies, antigens, nucleic acids and other natural biomolecules or their biomimetics [6]. At the same time, cell-based biosensors are also of essential interest due to their great potential for their application in the areas of environmental pollution detection and in biomedical diagnostics [7]. In contrast to molecular-based devices, biosensors containing native or recombinant living cells, pieces of tissue, organelles, biomembranes, liposomes or receptors, have some important advantages, including easy isolation and a broad specificity to the studied analytes. Both the possibility of improving biosensor signaling using gene engineering and the availability of effective methods for cell immobilization are the valuable properties of cell-based biosensors [6,7].

The global market of (bio)sensors was estimated to be worth USD 25.1 billion in 2021, and is expected to reach USD 38 billion by 2028 [8]. Improvements in the development of biosensors will significantly amplify their commercial production in the forecast period. Devices that detect analytes using optical and electrochemical transducers (including piezoelectrical) have progressed significantly. The most essential advantages of biosensors are excellent chemical selectivity, high sensitivity and a possibility of miniaturization. The drawbacks of biosensors are their limited stability and complicated procedure for the preparation of the biologically active material.

Combining bio- and nanotechnologies will enhance the production of perfect materials for biosensors. Such materials are necessary for the fabrication of traditional devices with improved analytical characteristics, as well as the design and generation of new high-tech biosensors, including piezoelectric, mass-based and nanomechanical sensors amongst other types [9,10].

2. (Bio)Sensing

In light of the facts mentioned above, this Special Issue (SI), entitled “World of Biosensing”, collected reports on the latest scientific achievements in (bio)sensing. We have reported on the development and testing of laboratory prototypes of (bio)sensors, aiming to accelerate the introduction of these sensitive and reliable experimental devices into commercial products. The analysis of recent scientific sources demonstrated that all the devices belong ultimately to two main modes of signal detection: electrochemical and optical, each group consisting of several subfamilies. Electrochemical (bio)sensors include amperometric, potentiometric, impediometric, piezoelectric piezoresistive sensors, amongst other types. Optical biosensors are based on methods of spectrophotometry, luminescence, fluorescence, surface plasmon resonance, surface-enhanced Raman scattering, atomic force spectroscopy and more [11,12].

Looking back to the “World of Biosensing,” we see that various topics were addressed—primarily concerning up-to-date achievements in the development and characterization of different types of (bio)sensors used to determine quantitative changes in a target analyte or process. Eighteen papers were submitted to this Special Issue, and eleven were accepted (a 61% acceptance rate). Further, we analyze shortly the content of the papers of the current Special Issue.

The first paper in the SI, authored by S. Cho and J.S. Lee, presented a review of the latest achievements in the development of biosensors based on morphologically tunable conducting polymers [13]. This overview article is pivotal, since the problem of providing effective electron transfer between a biorecognition element and an electrode surface is a decisive factor in electrochemical biosensors. The authors selected conducting polymers and nanoparticles with excellent electrical, chemical, and physical properties, polymers which would improve the analytical characteristics of biosensors when used as components [13,14,15]. The second paper, authored by O. Demkiv, N. Stasyuk, R. Serkiz et al., was dedicated to hydrogen peroxide-sensitive amperometric electrodes that were developed using metallic nanoparticles as effective mimetics of natural peroxidase [14]. Catalytically active nanomaterials or nanozymes, having higher stability and a lower cost in comparison with natural enzymes, are promising platforms for further biosensor construction. The paper by N. Stasyuk, G. Gayda, O. Demkiv et al. is an example of the successful application of peroxidase-like metallic nanozymes for the fabrication of arginine oxidase-based amperometric biosensors for L-arginine determination [15]. The developed biosensors, with their excellent analytical characteristics, may be used in different branches of science, medicine, and industry.

Problem-solving in the high-tech development process, especially in healthcare, is very relevant today. In the article authored by S. Gao, Y. Wang, C. Fang and L. Xu, the fabrication of a rehabilitation robot to help people suffering from limited mobile ability is described [16]. For lower limb rehabilitation to be provided successfully, level walking is necessary; thus, precise terrain identification (downhill, level, and uphill) is needed. To solve this challenge, an intelligent device was proposed that contained two types of wearable sensors: electromyography-based and ground-reaction force (mechanical-based).

Three papers in the SI dealt with the development of nonenzymatic optical sensors [17,18,19]. A gas sensor for detection of alcoholic vapors was described in the paper of S.-C. Wang, J.-W. Liang, Y.-B. Yao et al. [17]. A reusable poly(lactic acid)-based sandwich-structural membrane, equipped with excellent analytical characteristics, was fabricated for vapor sorbtion, with Fourier transform infrared spectroscopy used for signal detection. The authors proposed to apply the developed chemosensor for the monitoring of the atmosphere and environmental protection. The paper of P. Tomasella, V. Sanfilippo, C. Bonaccorso et al. [18] described the fabrication of nanocomposites as potential medicines. The hybrid materials consisted of graphene oxide derivatives and nanoparticles of gold. The main task of the investigation was to characterize, in detail, the structure, composition, and properties of these nanocomposites owing to their possibility to become cytotoxic drugs. To evaluate the nanotoxicity of the nanocomposites on human neuroblastoma cells in vitro, a colorimetric sensor was developed. The paper submitted by N. Cennamo, F. Arcadio, A. Minardo et al. [19] reported on the dependence of the working characteristics of surface plasmon resonance (SPR) sensors on their configurations. Different SPR sensors, which contain multimode and tapered D-shaped plastic optical fibers, were fabricated and studied using water–glycerin mixtures. The optimized sensors, based on tapered optical fibers covered with gold film, were shown to possess increased sensitivity and may be prospective platforms for biosensor construction.

Two papers are devoted to optic biosensors [20,21]. The article authored by Z. Kotsiri, A. Vantarakis, F. Rizzotto et al. described a simple and quick method for colorimetric detection of E. coli in seawater. Aptamer-coated magnetic beads were used for selective preconcentration of bacterial cells. The advantage of the PCR procedure, coming directly after magnetic pre-concentration, is the detection of target cells without the need for DNA isolation [20]. The paper of D.V. Sotnikov, A.V. Zherdev, E.A. Zvereva et al. discussed theoretical and experimental aspects of different approaches to the immune sensing of sulfonamides and fluoroquinolones [21]. It was shown that the cross-reactivity of enzymatic and fluorescent polarization immunoassays depends on the properties of antibodies and on the concentration ratio of immunoreagents/bioreceptors. The mathematical modeling and experimental comparison of both assays demonstrated the possibility of modulating immuno-detection selectivity without searching for new binding reactants.

The last two papers in the SI presented a nanomechanical biosensor as a promising tool to study the biomolecular interactions, vibrations and aggregation states of macromolecules [22,23]. Such a biosensor belongs to a subfamily of micro-electrochemical systems and converts the energy of biological processes into measurable mechanical motion, which may be detected with optical or piezo-resistive devices. An atomic force microscopy (AFM) sensor was used to measure the changes in the conformational states of the enzyme horseradish peroxidase, which was placed in a cell over the coil. The influence of different liquids’ motions in the flow-based system on the protein conformation was studied in both papers [22,23]. In the paper of V.S. Ziborov, T.O. Pleshakova, I.D. Shumov et al., the flow of a nonaqueous liquid (glycerol) was shown to induce changes in the enzyme aggregation state and its adsorbability onto the mica surface [22]. Similar results were obtained during a study of water flow, as reported in another work by Y. D. Ivanov, T. O. Pleshakova, I. D. Shumov et al. [23]. The changes in protein conformational states may be explained by the influence of an electromagnetic field, which was induced due to triboelectric charge generation during the motion of liquids through the coiled communication pipes. An AFM sensor in the flow-based system, capable of monitoring the changes in the aggregation states of proteins of interest, may be promising for clinical diagnostics and veterinary medicine.

All the papers published in this SI concerned chemical- [14,16,17,18,19] or macromolecular- based [13,15,20,21,22,23] sensors. It is worth mentioning that in the two years of the SI publication, the presented papers [13,14,15,16,17,18,19,20,21,22,23] have attracted a level of attention from the scientific community. Information concerning research interest in these papers was summarized up to January 2023 [24] and is presented in Figure 1.

3. Future (Bio)Sensors

Although the Special Issue has closed, investigations into the problems of biosensing will be continued. Future outlooks and possible areas of investigation may be formulated for the development of nanomaterial-based miniaturized transportable biosensors with improved mechanical, electrochemical, optical, thermometric, piezoelectric, or magnetic properties. The work on these problems can bring together leaders from industry and academia, both to develop new projects and to exploit modern technologies for future biosensing applications in clinical diagnosis, food analysis, process control, and environmental monitoring.