Bioluminescence assay for cell viability

Magnetically modified bacteriophage-triggered ATP release activated EXPAR-CRISPR/Cas14a system for visual detection of Burkholderia pseudomallei

Burkholderia pseudomallei, widely distributed in tropical and subtropical ecosystems, is capable of causing the fatal zoonotic disease melioidosis and exhibiting a global trend of dissemination. Rapid and sensitive detection of B. pseudomallei is essential for environmental monitoring as well as infection control. Here, we developed an innovative biosensor for quantitatively detecting B. pseudomallei relies on ATP released triggered by bacteriophage-induced bacteria lysis. The lytic bacteriophage vB_BpP_HN01, with high specificity, is employed alongside magnetic nanoparticles assembly to create a biological receptor, facilitating the capture and enrichment of viable target bacteria. Following a brief extraction and incubation process, the captured target undergoes rapid lysis to release contents including ATP. The EXPAR-CRISPR cascade reaction provides an efficient signal transduction and dual amplification module that allowing the generated ATP to guide the signal output as an activator, ultimately converting the target bacterial amount into a detectable fluorescence signal. The proposed bacteriophage affinity strategy exhibited superior performance for B. pseudomallei detection with a dynamic range from 10^2 to 10^7 CFU mL-1, and a LOD of 45 CFU mL-1 within 80 min. Moreover, with the output signal compatible across various monitoring methods, this work offers a robust assurance for rapid diagnosis and on-site environmental monitoring of B. pseudomallei.

Online monitoring system for qualitative and quantitative analysis of bioaerosols by combined ATP bioluminescence assay with loop-mediated isothermal amplification

Rapid detection of airborne pathogens is crucial in preventing respiratory infections and allergies. However, technologies aiming to real-time analysis of microorganisms in air remain limited due to the sparse and complex nature of bioaerosols. Here, we introduced an online bioaerosol monitoring system (OBMS) comprised of integrated units including a rotatable stainless-steel sintered filter-based sampler, a lysis unit for extracting adenosine triphosphate (ATP), and a single photon detector-based fluorescence unit. Through optimization of the ATP bioluminescence method and establishment of standard curves between relative luminescence units (RLUs) and ATP as well as microbial concentration, we achieved simultaneous detection of bioaerosols' concentration and activity. Testing OBMS with four bacterial and two fungal aerosols at a sampling flow rate of 10 to 50 L/min revealed an outstanding collection efficiency of 95 % at 30 L/min. A single OBMS measurement takes only 8 min (sampling: 5 min; lysis and detection: 3 min) with detection limits of 3 Pcs/ms photons (2.9 × 103 and 292 CFU/m3 for Staphylococcus aureus and Candida albicans aerosol). In both laboratory and field tests, OBMS detected higher concentrations of bioaerosol compared to the traditional Andersen impactor and liquid biosampler. When combined OBMS with loop-mediated isothermal amplification (LAMP), the bioaerosol can be qualitative and quantitative analyzed within 40 min without the cumbersome procedures of sample pretreatment and DNA extraction. These results offer a high compressive and humidity resistance membrane filtration sampler and validate the potential of OBMS for online measurement of bioaerosol concentration and composition.

Functionalized sampling swabs array-based portable ATP bioluminescence sensor with on-site enrichment and high specificity for live Salmonella detection

Live food-borne pathogens, featured with rapid proliferative capacity and high pathogenicity, pose an emerging food safety and public health crisis. The high-sensitivity detection of pathogens is particularly imperative yet remains challenging. This work developed a functionalized nylon swab array with enhanced affinity for Salmonella typhimurium (S.T.) for high-specificity ATP bioluminescence-based S.T. detection. In brief, the nylon swabs (NyS) were turned to N-methylation nylon (NyS-OH) by reacting with formaldehyde, and NyS-OH were further converted to NyS-CA by reacting with carboxylic groups of citric acid (CA) and EDC/NHS solution, for altering the NyS surface energy to favor biomodification. The antibody-immobilized nylon swab (MNyS-Ab) was ready for S.T.-specific adsorption. Three prepared MNyS-Ab were installed on a stirrer to form an MNyS-Ab array, allowing for on-site enrichment of S.T. through absorptive extraction. The enriched S.T. was quantified by measuring the bioluminescence of ATP released from cell lysis utilizing a portable ATP bioluminescence sensor. The bioassay demonstrated a detectable range of 102-107 CFU mL-1 with a detection limit (LOD) of 8 CFU/mL within 35 min. The signal of single MNyS-Ab swabs was 500 times stronger than the direct detection of 106 CFU/mL S.T. The MNyS-Ab array exhibited a 100-fold increase in extraction level compared to a single MNyS. This combination of a portable bioluminescent sensor and modified nylon swab array offers a novel strategy for point-of-care testing of live S.T. strains. It holds promise for high-sensitivity measurements of other pathogens and viruses.

Solid-Phase Synthesis as a Tool to Create Exactly Defined, Branched Polymer Vectors for Cell Membrane Targeting

Modern drug formulations often require, besides the active drug molecule, auxiliaries to enhance their pharmacological properties. Tailor-made, biocompatible polymers covalently connected to the drug molecule can fulfill this function by increasing its solubility, reducing its toxicity, and guiding it to a specific target. If targeting membrane-bound proteins, localization of the drug close to the cell membrane and its target is beneficial to increase drug efficiency and residence time. In this study, we present the synthesis of highly defined, branched polymeric structures with membrane-binding properties. One to three hydrophilic poly(ethylene oxide) or poly(2-ethyloxazoline) side chains were connected via a peptoid backbone using a two-step iterative protocol for solid-phase peptoid synthesis. Additional groups, e.g., a hydrophobic anchor for membrane attachment, were introduced. Due to the nature of solid-phase synthesis, the number and order of the side chains and additional units can be precisely defined. The method proved to be versatile for the generation of multifunctional, branched polymeric structures of molecular weights up to approximately 7000 g mol-1. The behavior of all compounds towards biological membranes and cells was investigated using liposomes as cell membrane models, HEK293 and U251-MG cell lines, and red blood cells, thereby demonstrating their potential value as drug auxiliaries with cell membrane affinity.

Biodegradation of low-density polyethylene by plasma-activated Bacillus strain

Plastic biodegradation by microorganisms is an eco-friendly and sustainable method without any ramifications. Herein, we used a cultivation method and 16S rRNA sequencing to screen bacteria that can efficiently colonize and degrade low-density polyethylene (LDPE) from various plastic wastes. We identified Bacillus safensis BS-10L through whole-genome sequencing analysis and verified its LDPE-degradation ability. However, the decomposition mechanism of the isolated bacteria was unclear and the decomposition efficiency was insufficient, so low-temperature plasma was used to increase the decomposition efficiency of the bacteria. The population and viability of bacteria treated with cold plasma increased. Plasma-activated bacteria could induce cracks, holes, and roughness on the surface of LDPE films over 90 days, and over 30 days; the LDPE film lost 13.40 ± 0.013% and 27.78 ± 0.014% of its mass by BS-10L and plasma-treated BS-10L, respectively. Fourier-transform infrared spectroscopic analysis identified new peaks of the C=O and C-O groups in the plasma-treated LDPE film, exhibiting high transmittance in the LDPE film that was inoculated with bacteria. X-ray photoelectron spectroscopic analysis showed that C-O bonds were generated by BS-10L strain, and relatively strong C=O bonds were generated in the film inoculated with plasma-treated BS-10L strain. Plasma treatment increased the colonization of the BS-10L strain and changed the chemical bonding of the LDPE film, suggesting that plasma-activated BS-10L could accelerate decomposition by oxidation by increasing the carbonyl group of the PE film. Therefore, plasma technology may be effective for enhancing the plastic-degrading ability of microorganisms.

The role of protein globule in firefly luciferase catalysis

The important role of the dynamic structure of firefly luciferase in enzyme functioning is a subject of this literature review. Due to the domain alternation, the optimal configuration of the active site is created for each stage of the luciferin oxidation. The diversity of bioluminescence spectra is explained by the combined emission of several coexisting forms of electronically excited oxyluciferin. The superposition of two or three emitter forms recorded in the bioluminescence spectra indicates that different luciferase conformers coexist in the reaction medium in dynamic equilibrium. The relationship between the thermal stability of the protein globule and the bioluminescence spectra is also discussed.

NK92 Expressing Anti-BCMA CAR and Secreted TRAIL for the Treatment of Multiple Myeloma: Preliminary In Vitro Assessment

Multiple myeloma (MM) has witnessed improved patient outcomes through advancements in therapeutic approaches. Notably, allogeneic stem cell transplantation, proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies have contributed to enhanced quality of life. Recently, a promising avenue has emerged with chimeric antigen receptor (CAR) T cells targeting B-cell maturation antigen (BCMA), expressed widely on MM cells. To mitigate risks associated with allogenic T cells, we investigated the potential of BCMA CAR expression in natural killer cells (NKs), known for potent cytotoxicity and minimal side effects. Using the NK-92 cell line, we co-expressed BCMA CAR and soluble tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) employing the piggyBac transposon system. Engineered NK cells (CAR-NK-92-TRAIL) demonstrated robust cytotoxicity against a panel of MM cell lines and primary patient samples, outperforming unmodified NK-92 cells with a mean difference in viability of 45.1% (±26.1%, depending on the target cell line). Combination therapy was explored with the proteasome inhibitor bortezomib (BZ) and γ-secretase inhibitors (GSIs), leading to a significant synergistic effect in combination with CAR-NK-92-TRAIL cells. This synergy was evident in cytotoxicity assays where a notable decrease in MM cell viability was observed in combinatorial therapy compared to single treatment. In summary, our study demonstrates the therapeutic potential of the CAR-NK-92-TRAIL cells for the treatment of MM. The synergistic impact of combining these engineered NK cells with BZ and GSI supports further development of allogeneic CAR-based products for effective MM therapy.

Development of a Novel ATP Bioluminescence Assay Based on Engineered Probiotic Saccharomyces boulardii Expressing Firefly Luciferase

Quantitative analysis of adenosine triphosphate (ATP) has been widely used as a diagnostic tool in the food and medical industries. Particularly, the pathogenesis of a few diseases including inflammatory bowel disease (IBD) is closely related to high ATP concentrations. A bioluminescent D-luciferin/luciferase system, which includes a luciferase (FLuc) from the firefly Photinus pyralis as a key component, is the most commonly used method for the detection and quantification of ATP. Here, instead of isolating FLuc produced in recombinant Escherichia coli, we aimed to develop a whole-cell biocatalyst system that does not require extraction and purification of FLuc. To this end, the gene coding for FLuc was introduced into the genome of probiotic Saccharomyces boulardii using the CRISPR/Cas9-based genome editing system. The linear relationship (r2 = 0.9561) between ATP levels and bioluminescence generated from the engineered S. boulardii expressing FLuc was observed in vitro. To explore the feasibility of using the engineered S. boulardii expressing FLuc as a whole-cell biosensor to detect inflammation biomarker (i.e., ATP) in the gut, a colitis mouse model was established using dextran sodium sulfate as a colitogenic compound. Our findings demonstrated that the whole-cell biosensor can detect elevated ATP levels during gut inflammation in mice. Therefore, the simple and powerful method developed herein could be applied for non-invasive IBD diagnosis.

Luciola mingrelica firefly luciferase as a marker in bioluminescent immunoassays

Chemical modification of the enzymes with biospecific macromolecules is used in various fields of biotechnology to impart new functions or improve their properties and is a fast and convenient way to get the final products. The preparation of highly active, stable, and functionally active conjugates of the thermostable luciferase through the NH2-groups or free SH-groups of the enzyme with target molecules of different molecular weight (albumin, avidin from chicken eggs, antibodies, and progesterone) is described. The obtained conjugates were successfully tested as a reporter in bioluminescent immunoassay for the detection of the molecules and pathogens. Thus, the luc-albumin (Luc-Alb) and luc-insulin (Luc-Ins) conjugates were used in competitive ELISA for the detection of an analyte (albumin or insulin) in the samples. Luc-progesterone (Luc-Pg) was used in the rapid homogeneous immunoassay of progesterone by the BRET technique with the detection limit of 0.5 ng/ml. Luciferase conjugates with avidin (Luc-Avi) and secondary and primary antibodies (Luc-RAM and Luc-Sal) were used for enzyme immunoassay detection of Salmonella paratyphi A cells with the cell detection limit of 5 × 104 CFU/ml. To reduce the detection limit of Salmonella cells, we developed a pseudo-homogeneous bioluminescent enzyme immunoassay of cells using a new matrix for the analyte capture-polystyrene microparticles coated with Pluronic F108, covalently labeled with Sal antibodies. This allowed to achieve efficient trapping of cells from solution, significantly reduced nonspecific sorption and decreased the cell detection limit to 2.7 × 103 CFU/ml without prior concentration of the sample. The methodology that was developed in this study can be applied for the development of novel bioanalytical systems based on firefly luciferases.

Advances in detection methods for viable Salmonella spp.: current applications and challenges

Salmonella is a common intestinal pathogen that can cause food poisoning and intestinal disease. The high prevalence of Salmonella necessitates efficient and sensitive methods for its identification, detection, and monitoring, especially of viable Salmonella. Conventional culture methods need to be more laborious and time-consuming. And they are relatively limited in their ability to detect Salmonella in the viable but non-culturable status if present in the sample to be tested. As a result, there is an increasing need for rapid and accurate techniques to detect viable Salmonella spp. This paper reviewed the status and progress of various methods reported in recent years that can be used to detect viable Salmonella, such as culture-based methods, molecular methods targeting RNAs and DNAs, phage-based methods, biosensors, and some techniques that have the potential for future application. This review can provide researchers with a reference for additional method options and help facilitate the development of rapid and accurate assays. In the future, viable Salmonella detection approaches will become more stable, sensitive, and fast and are expected to play a more significant role in food safety and public health.

Analyzing mechanisms of action of antimicrobial peptides on bacterial membranes requires multiple complimentary assays and different bacterial strains

Antimicrobial peptides (AMPs) commonly target bacterial membranes and show broad-spectrum activity against microorganisms. In this research we used three AMPs (nisin, epilancin 15×, [R4L10]-teixobactin) and tested their membrane effects towards three strains (Staphylococcus simulans, Micrococcus flavus, Bacillus megaterium) in relation with their antibacterial activity. We describe fluorescence and luminescence-based assays to measure effects on membrane potential, intracellular pH, membrane permeabilization and intracellular ATP levels. The results show that our control peptide, nisin, performed mostly as expected in view of its targeted pore-forming activity, with fast killing kinetics that coincided with severe membrane permeabilization in all three strains. However, the mechanisms of action of both Epilancin 15× as well as [R4L10]-teixobactin appeared to depend strongly on the bacterium tested. In certain specific combinations of assay, peptide and bacterium, deviations from the general picture were observed. This was even the case for nisin, indicating the importance of using multiple assays and bacteria for mode of action studies to be able to draw proper conclusions on the mode of action of AMPs.

Adenosine triphosphate (ATP) bioluminescence-based strategies for monitoring atmospheric bioaerosols

Bioaerosols play a momentous role in the transmission of human infectious diseases, so there has been increasing concern over their exposure in recent years. Bioaerosol monitor is crucial in environmental fields. Based on the universal existence of Adenosine triphosphate (ATP) in bioaerosols, ATP bioluminescence can be used as a powerful technique to detect bioaerosols without interference from non-bioaerosols. When ATP is released from bioaerosols, they can quantify microbial biomass by ATP bioluminescence. In this review, we provide the latest methodological improvements that enable more reliable quantification of bioaerosols in complex environmental samples, especially the use of ATP bioluminescence in this era of technological advancement via the following routes: lower sample content for the trace existence of bioaerosols in the atmosphere, higher sensitivity of ATP bioluminescence reaction system and shorter process times. We also highlight the new techniques in improving the efficiencies of these monitoring processes. The purpose of this paper is to make more people realize the great potential of the ATP bioluminescence system for monitoring airborne microorganisms. Additionally, the present work intends to increase people's awareness of developing novel technology combined with ATP bioluminescence reaction system to realize rapid, real-time, and sensitive sensing of bioaerosols.Implications: The ATP bioluminescence methodology can not only eliminate the interference of co-existing nonbiological (fluorescent or PM) but also significantly improve the efficiency of bioaerosol. Recent progresses, such as the application of ATP fluorescence technology in bioaerosol monitoring, indicating that the efficiency and sensitivity are possible to be further improved. Nevertheless, there is no reviews address these advances and deeply analyze the application of ATP fluorescence technology in this field. his contribution will attract wide attention from both academic and industrial communities of this field, as well as researchers engaging in environmental monitoring. Furthermore, the strategies and techniques of studying the ATP bioluminescence reviewed here is instructive for environment monitoring in various fields. Therefore, in view of significance and broad interest, we feel strongly that our critical review is very essential to the field of public health security, pharmaceutics, anti-bioterrorism, etc., and would like it to be published in Journal of the Air & Waste Management Association.

Bioluminescent test systems based on firefly luciferase for studying stress effects on living cells

The bioluminescent luciferin-luciferase reaction is based on the oxidation of D-luciferin by oxygen in the presence of ATP and magnesium ions, catalyzed by firefly luciferase. The possibilities of using this reaction to study the influence of external effectors of a physical and chemical nature (temperature exposure, additions of drugs, membrane-active compounds, etc.) on living cells (prokaryotes and eukaryotes) are considered. Examples of the use of test systems based on living cells producing thermostable firefly luciferase for monitoring cellular homeostasis are given. The study of the kinetics of changes in the concentration of ATP and luciferase inside and outside cells made it possible to determine in dynamics the metabolic activity, cytotoxicity, and survival of cells under conditions of cellular stress, to study the processes of ATP synthesis/hydrolysis, and to evaluate the effectiveness of lytic agents in changing the permeability of the cell membrane.

Biocontamination and diversity of epilithic bacteria and fungi colonising outdoor stone and mortar sculptures

Microbial communities colonising outdoor sculptures form intricate and dynamic ecosystems, which can accelerate the deterioration processes of the artworks and pose challenges to their conservation. In this study, the bacterial and fungal communities colonising the surfaces of five contemporary outdoor sculptures were characterised by high-throughput sequencing. The sculptures, made of marble, granite, Ançã limestone and mortar, are in urban parks and squares in the district of Porto, Portugal. The analysis of the microbial populations revealed great taxonomic diversity and species richness, including in well-preserved sculptures showing few visible traces of contamination. Proteobacteria, namely the genera Pseudomonas and Sphingomonas, were the core taxa common to all the sculptures, while Massilia and Aureobasidium were dominant only in granite. An abundance of pigment-producing microorganisms, such as Deinococcus, Methylobacterium, Rhodotorula and Sporobolomyces, was also found in granite. These are relevant taxonomic groups that can negatively impact stone and mortar artworks. The study was complemented with colourimetric analyses and bioluminescence assays to measure the adenosine triphosphate (ATP) content of samples collected from specific contaminated areas of the sculptures. The characterisation of the microbiomes of sculptures can provide further knowledge on the deterioration risks of this type of artwork in the region and help outline future targeted conservation strategies. KEY POINTS: • Rich and abundant microbiomes expose sculptures' vulnerability to deterioration. • Well-preserved sculptures are at risk of deterioration by pigment-producing taxa. • ATP and colourimetry quickly identified the most relevant contaminated areas.

A Multi-Purpose Approach to the Mechanisms of Action of Two Biocides (Benzalkonium Chloride and Dibromonitrilopropionamide): Discussion of Pseudomonas fluorescens’ Viability and Death

Biocides are widely used in water treatment for microbiological control. The rise of antimicrobial resistance and the need to assure properly managed water systems require a better understanding of the mechanisms of action of biocides and of their impact on cell’s viability as a function of dosage concentrations. The present work addresses these two aspects regarding the biocides benzalkonium chloride (BAC) and dibromonitrilopropionamide (DBNPA)—two biocides commonly found in the water treatment industry. For that, the following parameters were studied: culturability, membrane integrity, metabolic activity, cellular energy, and the structure and morphology of cells. Also, to assess cell’s death, a reliable positive control, consisting of cells killed by autoclave (dead cells), was introduced. The results confirmed that BAC is a lytic biocide and DBNPA a moderate electrophilic one. Furthermore, the comparison between cells exposed to the biocides’ minimum bactericidal concentrations (MBCs) and autoclaved cells revealed that other viability parameters should be taken into consideration as “death indicators.” The present work also shows that only for the concentrations above the MBC the viability indicators reached values statistically similar to the ones observed for the autoclaved cells (considered to be definitively dead). Finally, the importance of considering the biocide mechanism of action in the definition of the viability parameter to use in the viable but non-culturable (VBNC) determination is discussed.

The Combined Treatment With the FLT3-Inhibitor AC220 and the Complex I Inhibitor IACS-010759 Synergistically Depletes Wt- and FLT3-Mutated Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with a high mortality rate and relapse risk. Although progress on the genetic and molecular understanding of this disease has been made, the standard of care has changed minimally for the past 40 years and the five-year survival rate remains poor, warranting new treatment strategies. Here, we applied a two-step screening platform consisting of a primary cell viability screening and a secondary metabolomics-based phenotypic screening to find synergistic drug combinations to treat AML. A novel synergy between the oxidative phosphorylation inhibitor IACS-010759 and the FMS-like tyrosine kinase 3 (FLT3) inhibitor AC220 (quizartinib) was discovered in AML and then validated by ATP bioluminescence and apoptosis assays. In-depth stable isotope tracer metabolic flux analysis revealed that IACS-010759 and AC220 synergistically reduced glucose and glutamine enrichment in glycolysis and the TCA cycle, leading to impaired energy production and de novo nucleotide biosynthesis. In summary, we identified a novel drug combination, AC220 and IACS-010759, which synergistically inhibits cell growth in AML cells due to a major disruption of cell metabolism, regardless of FLT3 mutation status.

In Vitro Liver Toxicity Testing of Chemicals: A Pragmatic Approach

The liver is among the most frequently targeted organs by noxious chemicals of diverse nature. Liver toxicity testing using laboratory animals not only raises serious ethical questions, but is also rather poorly predictive of human safety towards chemicals. Increasing attention is, therefore, being paid to the development of non-animal and human-based testing schemes, which rely to a great extent on in vitro methodology. The present paper proposes a rationalized tiered in vitro testing strategy to detect liver toxicity triggered by chemicals, in which the first tier is focused on assessing general cytotoxicity, while the second tier is aimed at identifying liver-specific toxicity as such. A state-of-the-art overview is provided of the most commonly used in vitro assays that can be used in both tiers. Advantages and disadvantages of each assay as well as overall practical considerations are discussed.

Real-time monitoring of extracellular ATP in bacterial cultures using thermostable luciferase

Adenosine triphosphate (ATP) is one of the most important indicators of cell viability. Extracellular ATP (eATP) is commonly detected in cultures of both eukaryotic and prokaryotic cells but is not the focus of current scientific research. Although ATP release has traditionally been considered to mainly occur as a consequence of cell destruction, current evidence indicates that ATP leakage also occurs during the growth phase of diverse bacterial species and may play an important role in bacterial physiology. ATP can be conveniently measured with high sensitivity in luciferase-based bioluminescence assays. However, wild-type luciferases suffer from low stability, which limit their use. Here we demonstrate that an engineered, thermostable luciferase is suitable for real-time monitoring of ATP release by bacteria, both in broth culture and on agar surfaces. Different bacterial species show distinct patterns of eATP accumulation and decline. Real-time monitoring of eATP allows for the estimation of viable cell number by relating luminescence onset time to initial cell concentration. Furthermore, the method is able to rapidly detect the effect of antibiotics on bacterial cultures as Ampicillin sensitive strains challenged with beta lactam antibiotics showed strongly increased accumulation of eATP even in the absence of growth, as determined by optical density. Patterns of eATP determined by real-time luminescence measurement could be used to infer the minimal inhibitory concentration of Ampicillin. Compared to conventional antibiotic susceptibility testing, the method presented here is faster and more sensitive, which is essential for better treatment outcomes and reducing the risk of inducing antibiotic resistance. Real-time eATP bioluminescence assays are suitable for different cell types, either prokaryotic or eukaryotic, thus, permitting their application in diverse fields of research. It can be used for example in the study of the role of eATP in physiology and pathophysiology, for monitoring microbial contamination or for antimicrobial susceptibility testing in clinical diagnostics.

Different Methods for Cell Viability and Proliferation Assay: Essential Tools in Pharmaceutical Studies

BACKGROUND AND OBJECTIVE

The ratio of live cells to total cells in a sample is a definition for cell viability or cell toxicity. The assessment of the viable cells plays a critical role in all processes of the cell culture workflows. Overall, they are used to evaluate the survival of cells and also to optimize culture or experimental conditions following treatment with different agents or compounds, like during a drug screen. In most cases, the measurement of cell viability is the primary purpose of the experiments, for example, in pharmaceutical studies to evaluate agents' toxicity.

METHODS

A literature research was conducted on cell viability assays in MEDLINE (PubMed), Web of Science and Scopus.

RESULTS

There is a wide range of cell viability assays and different parameters such as cost, speed, and complexity of a test effect to determine the choosing method. However each method has some advantages and disadvantages and none of them is not 100% perfect method.

CONCLUSION

Accordingly, it seems that the simultaneous utility of at least two assays will cover each other disadvantages to demonstrate the effects of different agents on different cell types. For instance, when one assay measures cell metabolic health, the other one checks cells permeability. Therefore by this strategy a researcher can report with more confidence the effective doses of the examined therapeutic agents.

Activated carbon/titanium dioxide composite to adsorb volatile organic compounds associated with human body odor

The human body generates various malodor compounds in different body parts and even in the same parts. A more effective and versatile deodorant material that can suppress various key contributors to the body odor must be developed to improve the quality of life of affected individuals. In this study, activated carbon (AC) was found to have higher adsorption ability toward key body odor-generating compounds than zinc oxide (ZnO), which is a well-known deodorant material. To prevent pigmentation of human skin induced by the direct application of AC, white activated carbon (WAC) was developed by blending AC, titanium dioxide (TiO₂), and ammonium acrylate copolymer. AC to TiO₂ ratio of 1:6 was found to be the optimum blending ratio to form WAC. Compared with ZnO, this optimal WAC exhibited higher adsorption ability toward five key body odor compounds. The in vivo evaluation of the sample containing WAC revealed that it significantly suppressed the generation of axillary odor without a bactericidal effect. The developed WAC can effectively suppress the human body odor in different body parts. These findings are valuable for individuals experiencing psychological stress attributed to their unpleasant body odor.

Point-of-Need Diagnostics for Foodborne Pathogen Screening

Foodborne illness is a major public health issue that results in millions of global infections annually. The burden of such illness sits mostly with developing countries, as access to advanced laboratory equipment and skilled lab technicians, as well as consistent power sources, is limited and expensive. Current gold standards in foodborne pathogen screening involve labor-intensive sample enrichment steps, pathogen isolation and purification, and costly readout machinery. Overall, time to detection can take multiple days, excluding the time it takes to ship samples to off-site laboratories. Efforts have been made to simplify the workflow of such tests by integrating multiple steps of foodborne pathogen screening procedures into a singular device, as well as implementing more point-of-need readout methods. In this review, we explore recent advancements in developing point-of-need devices for foodborne pathogen screening. We discuss the detection of surface markers, nucleic acids, and metabolic products using both paper-based and microfluidic devices, focusing primarily on developments that have been made between 2015 and mid-2020.

Application of Biosensors for Detection of Pathogenic Food Bacteria: A Review

The use of biosensors is considered a novel approach for the rapid detection of foodborne pathogens in food products. Biosensors, which can convert biological, chemical, or biochemical signals into measurable electrical signals, are systems containing a biological detection material combined with a chemical or physical transducer. The objective of this review was to present the effectiveness of various forms of sensing technologies for the detection of foodborne pathogens in food products, as well as the criteria for industrial use of this technology. In this article, the principle components and requirements for an ideal biosensor, types, and their applications in the food industry are summarized. This review also focuses in detail on the application of the most widely used biosensor types in food safety.

Tetrazolium reduction assays under-report cell death provoked by clinically relevant concentrations of proteasome inhibitors

High throughput cell viability screening assays often capitalize on the ability of active enzymes or molecules within viable cells to catalyze a quantifiable chemical reaction. The tetrazolium reduction (MTT) assay relies on oxidoreductases to reduce tetrazolium into purple formazan crystals that are solubilized so absorbance reflects viability, while other assays use cellular ATP to catalyze a luminescence-emitting reaction. It is therefore important to know how accurately these assays report cellular responses, as cytotoxic anti-cancer agents promote cell death via a variety of signaling pathways, some of which may alter how these assays work. In this study, we compared the magnitude of cytotoxicity to different cell types provoked by currently used anti-cancer agents, using three different cell viability assays. We found the three assays were consistent in reporting the viability of cells treated with chemotherapy drugs or the BH3 mimetic navitoclax, but the MTT assay underreported the killing capacity of proteasome inhibitors. Additionally, the MTT assay failed to confirm the induction of caspase-mediated cell death by bortezomib at physiologically relevant concentrations, thereby mischaracterizing the mode of cell death. While the cell viability assays used allow for the rapid identification of novel cytotoxic compounds, our study emphasizes the importance for these screening assays to be complemented with a direct measure of cell death or another independent measure of cell viability. We caution researchers against using MTT assays for monitoring cytotoxicity induced by proteasome inhibitors.

In vivo imaging of transgenic Brugia malayi

Background

Studies of the human filarial parasite have been hampered by the fact that they are obligate parasites with long life cycles. In other pathogenic infections, in vivo imaging systems (IVIS) have proven extremely useful in studying pathogenesis, tissue tropism and in vivo drug efficacy. IVIS requires the use of transgenic parasites expressing a florescent reporter. Developing a method to produce transgenic filarial parasites expressing a florescent reporter would permit IVIS to be applied to the study of tissue tropism and provide a non-invasive way to screen for in vivo drug efficacy against these parasites.

Methodology/Principal findings

We report the development of a dual luciferase reporter construct in a piggyBac backbone that may be used to stably transfect Brugia malayi, a causative agent of human filariasis. Parasites transfected with this construct were visible in IVIS images obtained from infected gerbils. The signal in these infected animals increased dramatically when the transgenic parasites matured to the adult stage and began to produce transgenic progeny microfilaria. We demonstrate that the IVIS system can be used to develop an effective method for cryopreservation of transgenic parasites, to non-invasively monitor the effect of treatment with anti-filarial drugs, and to rapidly identify transgenic F1 microfilariae.

Conclusions

To our knowledge, this represents the first application of IVIS to the study of a human filarial parasite. This method should prove useful in studies of tissue tropism and as an efficient in vivo assay for candidate anti-filarial drugs.

The human filarial parasites are responsible for two major debilitating diseases; lymphatic filariasis (elephantiasis) and onchocerciasis (river blindness). Both have been identified as diseases that can be eliminated as a public health problem. However, the current elimination programs rely upon prolonged distribution of a limited number of drugs, a process which is logistically difficult to accomplish and may encourage the development of resistance. Thus, more effective drugs are needed. In other infectious diseases, in vivo imaging systems (IVIS) have proven to be very effective tools to study the pathogenesis of infection and to develop rapid and non-invasive assays for new drugs. Here we report the adaptation of IVIS to a human filarial parasitic infection and demonstrate in principal that it may be used to non-invasively monitor the efficacy of anti-filarial treatment in vivo. This system should prove useful as an in vivo screen for new anti-filarial compounds, as well as studies of the basic biology of these parasites.

Challenges and Opportunities in Preclinical Research of Synthetic Cannabinoids for Pain Therapy

Cannabis has been used in pain management since 2900 BC. In the 20th century, synthetic cannabinoids began to emerge, thus opening the way for improved efficacy. The search for new forms of synthetic cannabinoids continues and, as such, the aim of this review is to provide a comprehensive tool for the research and development of this promising class of drugs. Methods for the in vitro assessment of cytotoxic, mutagenic or developmental effects are presented, followed by the main in vivo pain models used in cannabis research and the results yielded by different types of administration (systemic versus intrathecal versus inhalation). Animal models designed for assessing side-effects and long-term uses are also discussed. In the second part of this review, pharmacokinetic and pharmacodynamic studies of synthetic cannabinoid biodistribution, together with liquid chromatography–mass spectrometric identification of synthetic cannabinoids in biological fluids from rodents to humans are presented. Last, but not least, different strategies for improving the solubility and physicochemical stability of synthetic cannabinoids and their potential impact on pain management are discussed. In conclusion, synthetic cannabinoids are one of the most promising classes of drugs in pain medicine, and preclinical research should focus on identifying new and improved alternatives for a better clinical and preclinical outcome.

Pulsed high-power microwaves do not impair the functions of skin normal and cancer cells in vitro: A short-term biological evaluation

•

Pulsed high power microwave (MW) at a frequency 3.5 GHz was generated.

•

MW did not induce cell death in skin fibroblast normal cells and melanoma cells.

•

MW did not alter the morphology of melanoma cells.

•

Gene expression related to ATP synthesis and proliferation can get altered by MW.

•

MW selectively stimulated viability and proliferation of only melanoma cells.

Over the past few decades, microwave (MW) radiation has been widely used, and its biological effects have been extensively investigated. However, the effect of MW radiation on human skin biology is not well understood. We study the effects of pulsed high-power microwaves (HPMs) on melanoma (G361 and SK-Mel-31) and normal human dermal fibroblast (NHDF) cells. A pulsed power generator (Chundoong) was used to generate pulsed HPMs (dominant frequency: 3.5 GHz). For treatment 1, 5, 15, and 45 shots are given to cells in which the electromagnetic energy of 0.6 J was delivered to the cells at each trigger shot. Cell viability, proliferation rate, apoptosis, cell death, metabolic activity, and oxygen-free radical regulation were evaluated after the MW exposure at low and high doses. MW exposure increased the viabilities and proliferation rates of both melanoma cell lines in a dose-dependent manner, while no significant effects on the fibroblast cells were observed. We found an elevated level of ATP and mitochondrial activity in melanoma cells. Also, it was observed that MW exposure did not affect cell death in melanoma and fibroblast cells. A polymerase chain reaction analysis indicated that the MWs induced dose-dependent proliferation markers without affecting the cell cycle and apoptotic genes in the melanoma cells. Our findings show the differential effects of the MW radiation on the melanoma cells, compared to those on the fibroblast cells.

Mechanisms of increased mitochondria-dependent necrosis in Wiskott-Aldrich syndrome platelets

Wiskott-Aldrich syndrome (WAS) is associated with thrombocytopenia of unclear origin. We investigated real-time cytosolic calcium dynamics, mitochondrial membrane potential and phoszphatidylserine (PS) exposure in single fibrinogen-bound platelets using confocal microscopy. The WAS platelets had higher resting calcium levels, more frequent spikes, and their mitochondria more frequently lost membrane potential followed by PS exposure (in 22.9% of platelets vs. 3.9% in controls; P<0.001) after the collapse of the last mitochondria. This phenomenon was inhibited by the mitochondrial permeability transition pore inhibitor cyclosporine A, as well by xestospongin C and lack of extracellular calcium. Thapsigargin by itself caused accelerated cell death in the WAS platelets. The number of mitochondria was predictive of PS exposure: 33% of platelets from WAS patients with fewer than five mitochondria exposed PS, while only 12% did among those that had five or more mitochondria. Interestingly, healthy donor platelets with fewer mitochondria also more readily became procoagulant upon PAR1/PAR4 stimulation. Collapse of single mitochondria led to greater cytosolic calcium increase in WAS platelets if they had one to three mitochondria compared with platelets containing higher numbers. A computer systems biology model of platelet calcium homeostasis showed that smaller platelets with fewer mitochondria could have impaired calcium homeostasis because of higher surface-to-volume ratio and greater metabolic load, respectively. There was a correlation (C=0.81, P<0.02) between the mean platelet size and platelet count in the WAS patients. We conclude that WAS platelets readily expose PS via a mitochondria-dependent necrotic mechanism caused by their smaller size, which could contribute to the development of thrombocytopenia.

A New Approach to Assess the Effect of Various Humic Compounds on the Metabolic Activity of Cells Participating in Methanogenesis

The possible use of the concentration of intracellular adenosine triphosphate (ATP) as a parameter enabling quick and adequate evaluation of the metabolic activity of methanogenic cells was demonstrated in the work. This approach was used to analyze the effect of introducing potassium humate and fulvic acids (1–10 g/L) into media with four different methanogenic consortia producing biogas. The ATP concentration was analyzed by the bioluminescent luciferin–luciferase method at the beginning and end of the process. During the entire process, the biogas composition, biogas efficiency, and the kinetics of methanogenesis in the presence of humic compounds were determined. The increase in the concentration of potassium humate led to a decrease in the overall energy status of the cells and reduced methanogenesis efficiency. However, fulvic acids introduced into the media stimulated methanogenesis in half of the tested consortia, which was accompanied by an increase in ATP concentration in cell samples. So, a positive correlation between the metabolic activity of cells in biogas formation and the concentration of ATP was observed. ATP concentration control appears to be an attractive tool for finding compounds that suppress methanogenesis in landfills.

A One-Step Extraction and Luminescence Assay for Quantifying Glucose and ATP Levels in Cultured HepG2 Cells

A fluorescence-based enzymatic microplate intracellular glucose assay was designed and fully validated. The method was tested in a hepatocellular cancer cell line (HepG2). Our novel one-step extraction reagent gave stable cell lysates for glucose, adenosine triphosphate (ATP), and total protein determination from the same sample. Limit of detection for glucose was 0.13 µM (26 pmol/well), which is superior to commercially available glucose assays. Both intra- and interday assay imprecision in HepG2 cultures were less than 12% coefficient of variance (CV). In cell lysates spiked with glucose, recovery at two levels varied between 83.70% and 91.81%, and both linearity and stability were acceptable. HepG2 cells treated with agents affecting glucose uptake/metabolism (phloretin, quercetin, quercetin-3'-sulfate, NaF, 3-bromopyruvate, NaN₃, oligomycin A, ochratoxin A, cytochalasin B, and anti-GLUT1 antibody) showed dose-dependent changes in glucose and ATP levels without total protein (cell) loss. Finally, we performed flow cytometric glucose uptake measurement in the treated cells using 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose fluorescent glucose analog. Glucose uptake did not always mirror the intracellular glucose levels, which most likely reflects the differences between the two methodologies. However, interpreting data obtained by both methods and taking ATP/protein levels at the same time, one can get information on the mode of action of the compounds.

Binding of Mucin by E. coli from Human Gut

Cells of E. coli isolates from the gut of healthy volunteers (N=5) and patients with Crohn's disease (N=5) and laboratory E. coli strain DH5α bound mucin in vitro in similar amounts ranging from 0.02 to 0.12 mg/mg of bacterial dry weight. Binding was evaluated by the decrease in optical absorption of mucin solution at 214 nm after incubation with bacteria. Detailed analysis of mucin binding by one of isolates showed that during incubation of 0.09 mg/ml bacteria in 0.15 M NaCl containing 0.1 mg/ml mucin at 25^oC, maximum binding was reached in 30 min, while in the presence of 14 mM α-methyl mannoside, mucin binding decreased by 46% (p<0.05). Confocal microscopy revealed intensive binding of FITC-labeled mucin to the surface of a small number of bacterial cells. Mucin binding did not significantly affect zeta potential of bacteria and their energetic status assessed by ATP content; at the same time, ATP content in the extracellular environment slightly increased.

Magnetic-dependent ATP pool in Escherichia coli

The ATP pool in Escherichia coli is a magnetic-dependent characteristic of microorganism vital activity. It depends on the values of the external static magnetic field and the existence of magnetic moment of magnesium isotopes nuclei added to the growth nutrient medium. The combined effects of the magnetic field 70-95 mT and magnesium magnetic isotope ²⁵Mg on E. coli bacteria leads to increase intracellular concentration of ATP. Magnetic-field effects in the range of 0.8-16 mT, registered for all bacteria regardless of the magnesium-isotopic enrichment of nutrient medium, evidence about the sensitivity of intracellular processes to weak magnetic fields.

Phase Transition of the Bacterium upon Invasion of a Host Cell as a Mechanism of Adaptation: a Mycoplasma gallisepticum Model

What strategies do bacteria employ for adaptation to their hosts and are these strategies different for varied hosts? To date, many studies on the interaction of the bacterium and its host have been published. However, global changes in the bacterial cell in the process of invasion and persistence, remain poorly understood. In this study, we demonstrated phase transition of the avian pathogen Mycoplasma gallisepticum upon invasion of the various types of eukaryotic cells (human, chicken, and mouse) which was stable during several passages after isolation of intracellular clones and recultivation in a culture medium. It was shown that this phase transition is manifested in changes at the proteomic, genomic and metabolomic levels. Eukaryotic cells induced similar proteome reorganization of M. gallisepticum during infection, despite different origins of the host cell lines. Proteomic changes affected a broad range of processes including metabolism, translation and oxidative stress response. We determined that the activation of glycerol utilization, overproduction of hydrogen peroxide and the upregulation of the SpxA regulatory protein occurred during intracellular infection. We propose SpxA as an important regulator for the adaptation of M. gallisepticum to an intracellular environment.

A simplified ATP method for the rapid control of cell viability in a freeze-dried BCG vaccine

We propose a simple and cost-effective ATP method for controlling the specific activity of a freeze-dried BCG vaccine. A freeze-dried BCG vaccine is reconstituted with 1ml saline and incubated for 15min at room temperature and then for 1h at 37°C. The vaccine is then treated with apyrase to remove extracellular ATP. After that, the cells are lysed with DMSO and the ATP content in the lysate is measured by the bioluminescence method. To implement the method, we developed a kit that requires no time-consuming preparation before the analysis. We demonstrated the linear relationship between the experimental values of the specific activity (10⁶CFU/mg) and intracellular ATP content (ATP, pmol/mg) for different batches of the studied BCG vaccines; the proportionality coefficient was К=0.36±0.02. We proposed a formula for calculating the specific activity from the measured content of intracellular ATP (ATP, pmol/mg). The comparison of the measured and calculated values of the specific activity (10⁶CFU/mg) shows that these values are similar; their differences fall within the allowable range of deviations for the specific activity values of the BCG vaccine.