Mycobacterium tuberculosis (Mtb) is the etiological agent of tuberculosis (TB), a disease that alt-hough preventable and curable, remains a global epidemic due to the emergence of resistance and a latent form responsible for a long period of treatment. Drug discovery in TB is a challenging task due to the heterogeneity of the disease, the emergence of resistance and an uncomplete knowledge of the pathophysiology of the disease. The limited permeability of the cell wall and the presence of multiple efflux pumps remain a major barrier to achieve effective intracellular drug accumulation. While the complete genome sequence of Mtb has been determined and several potential protein targets have been validated, the lack of adequate models for in vitro and in vivo studies is a limit-ing factor in TB drug discovery programs. In current therapeutic regimens, less than 0.5% of bac-terial proteins are targeted being the biosynthesis of the cell wall and the energetic metabolism two of the most important processes exploited for TB chemotherapeutics. This review provides an overview on the current challenges in TB drug discovery and emerging Mtb druggable proteins, and how chemical probes for protein profiling enabled the identification of new targets and bi-omarkers, paving the way to disruptive therapeutic regimens and diagnostic tools.

There are several well-known methods for determining enzyme catalytic activity, including spectral techniques and electrochemical approaches. However, at present, there is no definitive solution to the challenges associated with the fluorescent approach in, for instance, systems of reverse micelles, non-aqueous media, and model biomembranes. We propose the use of the fluorescent resonant energy transfer (FRET) technique, which can enhance the selectivity of fluorescent detection of enzyme activity by shifting the maximum emission wavelength to the longer-wavelength range and reducion the influence of medium components. As fluorescence donors, we have used derivatives of 4-methylumbelliferone (MUmb) and 7-amino-4-methylcoumarin (AMC), which also serve as substrates for hydrolases such as chymotrypsin, phosphatase, and asparaginase. During the catalytic depletion of substrates, an accumulation of a highly fluorescent product is observed. This product can be specifically detected using the fluorescent marker rhodamine 6G (R6G), which emits light in the red region of the spectrum (550–600 nm) with high quantum yield. A significant FRET effect is observed when forming AOT reverse micelles. This is due to the proximity of fluorophores within the hydrophobic core of the micelle, which is shorter than in a buffer solution. This approach have practical implications for visualizing intracellular processes. The FRET technique can be used to determine intracellular enzymatic activity by detection with confocal laser scanning microcopy (CLSM), as demonstrated with L-asparaginase, a clinically important anti-leukemia medication. The approach suggested will allow researchers to study enzyme activity within cells. This has the potential to revolutionize medicine by improving drug development and shedding light on previously unknown aspects of cellular metabolism.

Lysine plays a crucial role in promoting development, enhancing immune function, and improving the function of central nervous system tissues. The two configurational isomers of amino acids have significantly different effects. Currently, methods for chiral recognition of lysine all have drawbacks such as expensive equipment and complicated detection processes, whereas fluorescence analysis boasts high sensitivity, strong selectivity, and simple operation. In this study, we synthesized four novel Binaphthyl-Amine (BINAM)-based fluorescent probes capable of specifically identifying the L-configuration of lysine among the twenty amino acids constituting human proteins. The enantiomeric fluorescence enhancement ratio (ef or ΔIL/ΔID) reached up to 15.29, demonstrating high enantioselectivity. We also evaluated the probe's recognition ability under different pH, reaction times, and metal ion conditions, as well as the Limit of Detection of the probe. Our findings indicate that this probe is a highly stable tool for detecting chiral lysine.

Fluorescent labels, especially FRET probes, are promising tools for studying a number of bio-chemical processes. In this paper, we promoted 2 important applications of FRET probes (MUTMAC-R6G and FITC-R6G): i) the formation of micelles from surfactants of various natures and polymers (chitosan – fatty acid), as well as ii) monitoring of enzymatic activity with improved parameters (increased analytical signal and improved selectivity due to shift to the long-wavelength region). The formation of micelles is accompanied by the convergence of fluorophores in the hydrophobic micelle core by a distance closer than in the buffer solution, thus r/R0 (where R0 – Foerster radius) is chosen as an analytical signal of micelle formation, including critical micelle concentration (CMC) and critical pre-micelle concentration (CPMC). The CMC values calculated using FRET probes are in a good agreement with literature data. At the same time, the r/R0 function provides valuable information about the nature and mechanism of micelle formation. With the second analytical application of FRET probes, we considered the optimization of techniques for studying enzymatic activity. The enzyme catalyses the reaction with the release of a fluorescent product, the signal from which may not be enough for detection, or it may be quenched, for example, in the reverse micelles (AOT-octane). Here we have proposed a solution – a FRET probe containing a rhodamine 6G (R6G) acceptor, which allows us to monitor the enzymatic reaction selectively (in the red region, 550-600 nm), and obtain a significantly higher fluorescence yield (potentially from 10 to 250 times). Thus, we have demonstrated a high potential for the FRET probes application as indicators of micelle formation as well as for the study of the enzyme catalytic activity. In the future, the method developed has prospects for application in the visualization of the enzyme functioning in cells due to the shift of the fluorescence signal to the long-wavelength region with an increase in the signal selectivity to suppress autofluorescence.

Galectin-3 is considered a cancer biomarker and bioindicator of fibrosis and cardiac remodeling, and, therefore, it is desirable to develop convenient methods for its detection. Herein, an approach based on the development of multivalent electrochemical probes with high galectin-3 sensing abilities is reported. The probes consist of multivalent presentations of lactose–ferrocene conjugates scaffolded on poly(amido amine) (PAMAM) dendrimers and gold nanoparticles. Such multivalent lactose–ferrocene conjugates are synthesized by coupling of azidomethylferrocene-lactose building blocks on alkyne-functionalized PAMAM, for the case of the glycodendrimers, and to disulfide‐functionalized linkers that are then used for the surface modification of citrate-stabilized gold nanoparticles. The binding and sensing abilities towards galectin 3 of both ferrocene-containing lactose dendrimers and gold nanoparticles have been evaluated by means of isothermal titration calorimetry, UV-vis spectroscopy, and differential pulse voltammetry. The highest sensitivity by electrochemical methods to galectin-3 was shown by lactosylferrocenylated gold nanoparticles, which are able to detect the lectin in nanomolar concentrations.

Abscisic acid (ABA) is a conserved “stress hormone” in unicellular organisms, plants and animals. In mammals, ABA and its receptors LANCL1 and LANCL2 stimulate insulin-independent cell glucose uptake and oxidative metabolism: overexpression of LANCL1/2 increases, and their si-lencing conversely reduces, mitochondrial number, respiration and proton gradient dissipation in muscle cells and in brown adipocytes. We hypothesized that the ABA/LANCL hor-mone/receptors system could be involved in thermogenesis. Heat production by LANCL1/2-overexpressing vs. double-silenced cells was compared in rat H9c2 cardiomyocytes with two different methods: differential temperature measurements using sensitive thermistor probes, and differential isothermal calorimetry. Results indicate that overexpressing cells generate an approx. double amount of thermal power compared with double-silenced cells, and that addition of ABA further doubles heat production in overexpressing cells. With the temperature probes, we find a time-scale of approx. 4 min for thermogenesis to “turn on” after nutrient addition. These results identify the ABA/LANCL hormone receptors system as a hitherto unknown regu-lator of cell thermogenesis. Pharmacologic means of increasing metabolic energy dissipation are considered a promising strategy to reduce oxidative stress and lipid accumulation at a cellular and organismic level: from this study, LANCL1-2 proteins emerge as targetable controllers of ther-mogenesis through their natural ligand ABA.

Esterases are hydrolases that catalyze the hydrolysis of esters into the corresponding acids and alcohols. The development of fluorescent probes for detecting esterases is of great importance due to their wide spectrum of biological and industrial applications. These probes can provide a rapid and sensitive method for detecting the presence and activity of esterases in various samples, including biological fluids, food products, and environmental samples. Fluorescent probes can also be used for monitoring the effects of drugs and environmental toxins on esterase activity, as well as to study the functions and mechanisms of these enzymes in several biological systems. Additionally, fluorescent probes can be designed to selectively target specific types of esterases, such as those found in pathogenic bacteria or cancer cells. In this review, we summarize the recent fluorescent probes described for the visualization of cell viability and some applications for in vivo imaging. On the other hand, Positron Emission Tomography (PET) is a nuclear-based molecular imaging modality of great value to study the activity of enzymes in vivo. We provide some examples of PET probes for imaging acetylcholinesterases and butyrylcholinesterases in brain, which are valuable tools for diagnosing dementia and monitoring the effects of anticholinergic drugs on the central nervous system.

Verification of inclusivity of molecular detection methods gives indications on the reliability of viral infections diagnosis because of the tendency of viral pathogens to undergo sequence variation. This study was aimed to select inclusive probe based reverse transcription quantitative PCR (RT-qPCR) assays for the diagnosis of the most widespread and detrimental viruses infecting honeybees, namely the acute bee paralysis virus (ABPV), the black queen cell virus (BQCV), the chronic paralysis bee virus (CBPV), the deformed wing virus variants A (DWVA) and B (DWVB), and the sacbrood virus (SBV). Therefore, detection methods previously described were re-evaluated in silico for specificity and inclusivity. Based on this evaluation, selected methods were modified or new ones were designed and tested in duplex RT-qPCR reactions. The limits of detection (LODs), effect of multiplexing on sensitivity and viral RNA quantification potential in bees and hive debris were assessed. This study made available diagnostic assays able to detect an increased number of virus variants compared to previously described tests and two viral pathogens in a single PCR reaction.

Optical coherence tomography (OCT) is one of the most promising, innovative and rapidly emerging intraoperative imaging modalities for neurosurgical guidance in brain tissue imaging, "optical biopsy", brain cerebral vascular detection, nerve fibers and white matter tracts detection. In this article, we provide a short survey of cross-polarization OCT and different types of OCT probes that can be used in routine neurosurgical practice. Through different types of probes there are multiple applications where OCT can play a highly complementary role in offering the real-time microscopic assessment and imaging of normal and pathological brain tissues. The biopsy-needle based probe for CP OCT was shown to be an effective instrument for brain tissue mapping and express estimation of tissue status as well as for detecting large blood vessels to prevent causing bleeding during biopsy sampling. The folded CP OCT probe for intraoperative use for brain tissue examination was shown as a potentially efficient sensor head for CP OCT. The probe demonstrated high lateral resolution in diffractive limited probing beam quality. The length of dismountable probe tip allows using the probe under operating microscope. Due to the designed family of specialized probes CP OCT fills in the niche of devices for express brain tissue examination in situ.

The German health authorities' guidelines for medical devices in 2012 highlighted the importance of cleaning ultrasound probes, emphasizing their validation and reliability. In addition to automated and validated options, alternative manual methods such as wipe disinfection have gained traction due to their independence from additional hardware. The study examines the effectiveness of manual disinfection methods, specifically the cleaning process, addressing concerns raised by the Robert Koch Institute regarding the lack of validation for wipe disinfection of semi-critical devices. The EQUINOS colored wipe disinfection kit identified wetting gaps in all cleanings across four probes tested. The results indicate significant challenges in ensuring complete surface wetting, particularly in complex body parts such as clip-on areas and shapes for additional biopsy attachments, suggesting that manual methods alone may not adequately mitigate the risk of infection transmission (p value .001). The study concludes that while manual disinfection methods are a viable alternative to automated reprocessing, there is a critical need for enhanced training and potentially the development of more effective manual disinfection techniques or colored wipes to ensure patient safety and compliance with healthcare hygiene standards.

Papain-like protease PLpro, a domain within a large polyfunctional protein nsp3, plays key roles in the life cycle of SARS-CoV-2, being responsible for the first events of cleavage of a polyprotein into individual proteins (nsp1-4) as well as for the suppression of cellular immunity. Here, we developed a new genetically encoded fluorescent sensor, named PLpro-ERNuc, for detection of PLpro activity in living cells using translocation-based readout. The sensor was designed as follows. A fragment of nsp3 protein was used to direct the sensor on the cytoplasmic surface of endoplasmic reticulum (ER) membrane, thus closely mimicking the natural target of PLpro. The fluorescent part included two bright fluorescent proteins - red mScarlet I and green mNeonGreen, separated by a linker with the PLpro cleavage site. Nuclear localization signal (NLS) was attached to ensure accumulation of mNeonGreen into the nucleus upon cleavage. We tested PLpro-ERNuc in the model of recombinant PLpro expressed in HeLa cells. The sensor demonstrated expected cytoplasmic reticular network in the red and green channels in the absence of protease, and efficient translocation of the green signal into nuclei in the PLpro-expressing cells (14-fold increase of the nucleus/cytoplasm ratio). Then, we used PLpro-ERNuc in the model of Huh7.5 cells infected with SARS-CoV-2 virus, where it showed robust ER-to-nucleus translocation of the green signal in the infected cells 24 h post infection. We believe that PLpro-ERNuc represents a useful tool for screening PLpro inhibitors as well as for monitoring virus spread in a culture.

Issues presented by the application of monoclonal antibodies in diagnostic assays and as curative agents can make the use of such molecules cost-prohibitive and sometimes even unsafe. This has warranted the development of short single-stranded oligonucleotides known as Aptamers. The structural malleability of these short DNA or RNA nucleotide segments allows them to exist in distinct conformations. SELEX (Systematic Evolution of Ligands by Exponential Enrichment) is a multi-step process for synthesis of aptamers. Each step of this procedure is governed by a diverse set of factors that influence production efficiency, binding affinity, and specificity of the oligonucleotides. Headway in aptamer research has been made in recent years by the introduction of newer iterations of the SELEX process. A greater number of studies are now being carried out to incorporate aptamers into existing disease detection tools and therapies. An overview has been given first on the key aptamer properties and the process of their production (with its newer iterations), contrasting each of them with that of monoclonal antibodies. Possible manifold applications afforded due to unique aptamer characteristics are also discussed. A keen review is further provided on the design, development and use of fluorescent aptamers in bioimaging, sequencing or profiling, and treatment of pathogenic bacteria and tumor cells.

Photoacoustic imaging is attracting a great deal of interest owing to its distinct advantages over other imaging techniques such as fluorescence or magnetic resonance image. Availability of photoacoustic probes for reactive oxygen and nitrogen species (ROS/RNS) could shed light on a plethora of biological processes mediated by these key intermediates. Tetramethylbenzidine (TMB) is a non-toxic and non-mutagenic colorless dye that develops a distinctive blue color upon oxidation. In this work we have investigated the potential of TMB as photoacoustic probe for ROS/RNS. Our results indicate that TMB reacts with hypochlorite, hydrogen peroxide, singlet oxygen and nitrogen dioxide to produce the blue oxidation product, while ROS such as the superoxide radical anion, sodium peroxide, hydroxyl radical or peroxynitrite yield a colorless oxidation product. TMB does not penetrate Escherichia coli cytoplasm but is capable of detecting singlet oxygen generated in its outer membrane.

Two-photon imaging of light stimulus-evoked neuronal activity has been used to study all neuron classes in the vertebrate retina, from the photoreceptors to the retinal ganglion cells. Clearly, the ability to study retinal circuits down to the level of single synapses or zoomed out at the level of complete populations of neurons, has been a major asset in our understanding of this beautiful circuit. In this chapter, we discuss the possibilities and pitfalls of using an all-optical approach in this highly light-sensitive part of the brain.

In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of 1.4 dB and 3.8 dB per 20 mm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.