Application of MTT assay for probing metabolic activity in bacterial biofilm-forming cells on nanofibrous materials.

The quantification of cellular metabolic activity via MTT assay has become a widespread practice in eukaryotic cell studies and is progressively extending to bacterial cell investigations. This study pioneers the application of MTT assay to evaluate the metabolic activity of biofilm-forming cells within bacterial biofilms on nanofibrous materials. The biofilm formation of Staphylococcus aureus and Escherichia coli on nanomaterials electrospun from polycaprolactone (PCL), polylactic acid (PLA), and polyamide (PA) was examined. Various parameters of the MTT assay were systematically investigated, including (i) the dissolution time of the formed formazan, (ii) the addition of glucose, and (iii) the optimal wavelength for spectrophotometric determination. Based on interim findings, a refined protocol suitable for application to nanofibrous materials was devised. We recommend 2 h of the dissolution, the application of glucose, and spectrophotometric measurement at 595 nm to obtain reliable data. Comparative analysis with the reference CFU counting protocol revealed similar trends for both tested bacteria and all tested nanomaterials. The proposed MTT protocol emerges as a suitable method for assessing the metabolic activity of bacterial biofilms on PCL, PLA, and PA nanofibrous materials.

Accelerated Method for Determining Ischemic Brain Damage in Rats and Assessment the Neuroprotective Effect of a Complex Herbal Remedy.

The severity of ischemic injury was evaluated by densitometry of brain samples stained with 2,3,5-triphenyltetrazolium chloride (TTC) on a rat model of cerebral ischemia/reperfusion (common carotid artery occlusion) and the neuroprotective activity of an extract of Astragalus membranaceus, Scutellaria baicalensis, and Phlojodicarpus sibiricus was assessed. Occlusion of the common carotid arteries led to a weakening of TTC staining of the brain tissue: densitometric indicators of the staining intensity for the cortex and striatum were lower than the corresponding indicators of sham-operated rats by 18.3 and 10.4%. The mean intensity of staining of brain samples did not differ in rats treated with the extract and sham-operated animals, which attested to its neuroprotective effect. The applied method is convenient for evaluation of the severity of ischemic brain damage at the early stages and screening potential neuroprotective agents.

A Color Indicator Based on 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide (MTT) and a Biodegradable Poly(ester amide) for Detecting Bacterial Contamination.

Bacterial contamination is a hazard in many industries, including food, pharmaceuticals, and healthcare. The availability of a rapid and simple method for detecting this type of contamination in sterile areas enables immediate intervention to avoid or reduce detrimental effects. Among these methods, colorimetric indicators are becoming increasingly popular due to their affordability, ease of use, and quick visual interpretation of the signal. In this article, a bacterial contamination indicator system was designed by incorporating MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) into an electrospun PADAS matrix, which is a biodegradable poly(ester amide) synthesized from L-alanine, 1,12-dodecanediol, and sebacic acid. Uniaxial stress testing, thermogravimetric analysis and scanning electron microscopy were used to examine the mechanical properties, thermal stability, and morphology of the mats, respectively. The capacity for bacterial detection was not only analyzed with agar and broth assays but also by replicating important environmental conditions. Among the MTT concentrations tested in this study (0.2%, 2%, and 5%), it was found that only with a 2% MTT content the designed system produced a color response visible to the naked eye with optimal intensity, a sensitivity limit of 104 CFU/mL, and 86% cell viability, which showed the great potential for its use to detect bacterial contamination. In summary, by means of the process described in this work, it was possible to obtain a simple, low-cost and fast-response bacterial contamination indicator that can be used in mask filters, air filters, or protective clothing.

Single-Cell MTT: A Simple and Sensitive Assay for Determining the Viability and Metabolic Activity of Polyploid Giant Cancer Cells (PGCCs).

Solid tumors and tumor-derived cell lines commonly contain highly enlarged (giant) cancer cells that enter a state of transient dormancy (active sleep) after they are formed, but retain viability, secrete growth promoting factors, and exhibit the ability to generate rapidly proliferating progeny with stem cell-like properties. Giant cells with a highly enlarged nucleus or multiple nuclei are often called polyploid giant cancer cells (PGCCs). Although PGCCs constitute only a subset of cells within a solid tumor/tumor-derived cell line, their frequency can increase markedly following exposure to ionizing radiation or chemotherapeutic drugs. In this chapter we outline a simple and yet highly sensitive cell-based assay, called single-cell MTT, that we have optimized for determining the viability and metabolic activity of PGCCs before and after exposure to anticancer agents. The assay measures the ability of individual PGCCs to convert the MTT tetrazolium salt to its water insoluble formazan metabolite. In addition to evaluating PGCCs, this assay is also a powerful tool for determining the viability and metabolic activity of cancer cells undergoing premature senescence following treatment with anticancer agents, as well as for distinguishing dead cancer cells and dying cells (e.g., exhibiting features of apoptosis, ferroptosis, etc.) that have the potential to resume proliferation through a process called anastasis.

Development of a Convenient and Quantitative Method for Evaluating Photosensitizing Activity Using Thiazolyl Blue Formazan Dye.

Photosensitizers cause oxidative damages in various biological systems under light. In this study, the method for analyzing photosensitizing activity of various dietary and medicinal sources was developed using 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (thiazolyl blue formazan; MTT-F) as a probe. Significant and quantitative decolorization of MTT-F was observed in the presence of photosensitizers used in this study under light but not under dark conditions. The decolorization of MTT-F occurred irradiation time-, light intensity-, and photosensitizer concentration-dependently. The decolorized MTT-F was reversibly reduced by living cells; the LC-MS/MS results indicated the formation of oxidized products with -1 m/z of base peak from MTT-F, suggesting that MTT-F decolorized by photosensitizers was its corresponding tetrazolium. The present results indicate that MTT-F is a reliable probe for the quantitative analysis of photosensitizing activities, and the MTT-F-based method can be an useful tool for screening and evaluating photosensitizing properties of various compounds used in many industrial purposes.

XTT assay for detection of bacterial metabolic activity in water-based polyester polyurethane.

Cellular metabolic activity can be detected by tetrazolium-based colorimetric assays, which rely on dehydrogenase enzymes from living cells to reduce tetrazolium compounds into colored formazan products. Although these methods have been used in different fields of microbiology, their application to the detection of bacteria with plastic-degrading activity has not been well documented. Here, we report a microplate-adapted method for the detection of bacteria metabolically active on the commercial polyester polyurethane (PU) Impranil®DLN using the tetrazolium salt 2,3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT). Bacterial cells that are active on PU reduce XTT to a water-soluble orange dye, which can be quantitatively measured using a microplate reader. We used the Pseudomonas putida KT2440 strain as a study model. Its metabolic activity on Impranil detected by our novel method was further verified by Fourier-transform infrared spectroscopy (FTIR) analyses. Measurements of the absorbance of reduced XTT at 470 nm in microplate wells were not affected by the colloidal properties of Impranil or cell density. In summary, we provide here an easy and high-throughput method for screening bacteria active on PU that can be adapted to other plastic substrates.

Re-evaluation and modification of dehydrogenase activity tests in assessing microbial activity for wastewater treatment plant operation.

Reliable and cost-effective methods for monitoring microbial activity are critical for process control in wastewater treatment plants. The dehydrogenase activity (DHA) test has been recognized as an efficient measure of biological activity due to its simplicity and broad applicability. Nevertheless, the existing DHA test methods suffer from imperfections and are difficult to implement as routine monitoring techniques. In this work, an accurate and cost-effective modified DHA approach was developed and the procedure for the DHA test was critically evaluated with respect to the standard construction, sample pretreatment, incubation and extraction conditions. The feasibility of the modified DHA test was demonstrated by comparison with the oxygen uptake rate and adenosine triphosphate in a sequencing batch reactor. The sensitivities of the two typical tetrazolium salts to toxicant inhibition by heavy metals and antibiotics were compared, revealing that 2,3,5-triphenyltetrazolium chloride (TTC) exhibited a higher sensitivity. Furthermore, the sensitivity mechanism of the two DHA tests was elucidated through electrochemical experiments, theoretical analysis and molecular simulations. Both tetrazolium salts were found to be effective artificial electron acceptors due to their low redox potentials. Molecular docking simulations revealed that TTC could outperform other tetrazolium salts in accepting electrons and hydrogens from dehydrogenase. Overall, the modified DHA approach presents an accurate and cost-effective way to measure microbial activity, making it a practical tool for wastewater treatment plants.

Size-Dependent Electroporation of Dye-Loaded Polymer Nanoparticles for Efficient and Safe Intracellular Delivery.

Efficient and safe delivery of nanoparticles (NPs) into the cytosol of living cells constitutes a major methodological challenge in bio-nanotechnology. Electroporation allows direct transfer of NPs into the cytosol by forming transient pores in the cell membrane, but it is criticized for invasiveness, and the applicable particle sizes are not well defined. Here, in order to establish principles for efficient delivery of NPs into the cytosol with minimal cytotoxicity, the influence of the size of NPs on their electroporation and intracellular behavior is investigated. For this study, fluorescent dye-loaded polymer NPs with core sizes between 10 and 40 nm are prepared. Optimizing the electroporation protocol allows minimizing contributions of endocytosis and to study directly the effect of NP size on electroporation. NPs of <20 nm hydrodynamic size are efficiently delivered into the cytosol, whereas this is not the case for NPs of >30 nm. Moreover, only particles of core size <15 nm diffuse freely throughout the cytosol. While electroporation at excessive electric fields induces cytotoxicity, the use of small NPs <20 nm allows efficient delivery at mild electroporation conditions. These results give clear methodological and design guidelines for the safe delivery of NPs for intracellular applications.

Improved Formazan Dissolution for Bacterial MTT Assay.

The MTT assay, based on the enzymatic reduction of the water-soluble, yellowish tetrazolium salt 3-(4,5-dimethylthiazol)-2,5-diphenyl-tetrazolium bromide (MTT) to purple formazan, is commonly used for assessment of cell viability and proliferation. Accurate performance by the MTT assay depends on complete solubilization of cells and formazan and stability of the colored solution. Comparison of different solubilization solutions revealed that dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), buffered with ammonia buffer, pH 10, and containing 5% SDS, produced the best results. These two solvents provided rapid and complete solubilization of formazan and cells, with minimal background absorbance at 700 nm, good reproducibility (low interassay coefficient of variation), high sensitivity, and color stability for at least 24 h. A linear relationship between viable-cell number and formazan absorbance was preserved for cell densities up to ∼1 × 109 cells/mL for Gram-negative and Gram-positive microorganisms. Since MTT can be reduced by medium components in the absence of cells, blanks containing all medium components but no cells should be run simultaneously. Measurements at two wavelengths, one corresponding to absorption peak of formazan (570 nm) and a background absorbance far from the peak (700 nm), are necessary to avoid artifacts due to incomplete solubilization and turbidity. IMPORTANCE Reduction of the water-soluble tetrazolium salt 3-(4,5-dimethylthiazol)-2,5 diphenyl-tetrazolium bromide (MTT) to purple, water-insoluble formazan is commonly used for assessment of cell viability and proliferation. Spectrophotometric detection of formazan requires its solubilization. The solubilization solvent has a strong influence on data acquisition and often introduces artifacts, leading to misreading of results. This study offers a choice of solvents that minimize solubilization artifacts when the MTT test is applied to microbiological cultures.

Pyrazoline derivatives as promising novel antischistosomal agents.

Praziquantel is the only available drug to treat schistosomiasis, a parasitic disease that currently infects more than 240 million people globally. Due to increasing concerns about resistance and inadequate efficacy there is a need for new therapeutics. In this study, a series of 17 pyrazolines (15-31) and three pyrazoles (32-34) were synthesized and evaluated for their antiparasitic properties against ex vivo adult Schistosoma mansoni worms. Of the 20 compounds tested, six had a 50% effective concentration (EC50) below 30 µM. Our best hit, pyrazoline 22, showed promising activity against adult schistosomes, with an EC50 < 10 µM. Additionally, compound 22 had low cytotoxicity, with selectivity index of 21.6 and 32.2 for monkey and human cell lines, respectively. All active pyrazolines demonstrated a negative effect on schistosome fecundity, with a marked reduction in the number of eggs. Structure-activity relationship analysis showed that the presence of the non-aromatic heterocycle and N-substitution are fundamental to the antischistosomal properties. Pharmacokinetics, drug-likeness and medicinal chemistry friendliness studies were performed, and predicted values demonstrated an excellent drug-likeness profile for pyrazolines as well as an adherence to major pharmaceutical companies' filters. Collectively, this study demonstrates that pyrazoline derivatives are promising scaffolds in the discovery of novel antischistosomal agents.

Comparative assessment of antimicrobial, antiradical and cytotoxic activities of cannabidiol and its propyl analogue cannabidivarin.

Cannabidiol and cannabidivarin are phytocannabinoids produced by Cannabis indica and Cannabis sativa. Cannabidiol has been studied more extensively than its propyl analogue cannabidivarin. Therefore, we performed a battery of in vitro biological assays to compare the cytotoxic, antiradical and antibacterial activities of both cannabinoids. Potential mitochondrial metabolism alterations, DNA synthesis inhibition, and plasma membrane damage were studied by MTT assay, BrdU-ELISA and LDH assay of cancer and normal human cells exposed to cannabinoids. ABTS and DPPH assays were performed to observe the effects of the cannabinoids on free radicals. Microbial susceptibility tests were performed to study the activity of the cannabinoids in two bacterial species implicated in human infections, Escherichia coli and Staphylococcus aureus. The results showed that the cannabinoids induced medium levels of cytotoxicity in cancer and normal cells at concentrations ranging from 15.80 to 48.63 and from 31.89 to 151.70 µM, respectively, after 72 h of exposure. Cannabinoids did not exhibit a strong antioxidant capacity in scavenging ABTS or DPPH radicals. No evident differences were observed between the two cannabinoids in antimicrobial activity, except with respect to S. aureus, which showed greater susceptibility to cannabidiol than to cannabidivarin after 72 h of exposure.

Biocompatible graphene-zirconia nanocomposite as a cyto-safe immunosensor for the rapid detection of carcinoembryonic antigen.

Graphene-based materials have gained remarkable attention in numerous disciplines owing to their unique electrochemical properties. Out of various hybridized nanocomposites, graphene-zirconia nanocomposite (GZ) was distinctive due to its biocompatibility. Zirconia nanoparticles serve as spacers that reduce the stacking of graphene and improve the electrochemical performance of the material. Considering that lungs and skin suffer the greatest exposure to nanoparticles, this study aimed to evaluate the cytotoxicity of the as-synthesized GZ nanocomposites on MRC5 (lung cells) and HaCaT (skin cells) via morphological observation and cell viability assay using 3-(4,5 dimethylthiazol-2-yl)-(2,5-diphenyltetrazolium bromide) tetrazolium (MTT). GZ-treated cells showed a comparable proliferation rate and morphology with untreated cells under microscopic evaluation. Based on MTT results, the IC50 values of GZ were > 500 µg/ml for MRC5 and HaCaT cells. The excellent biocompatibility was the supremacy of GZ over other nanocomposites applied as electrode materials in biosensors. GZ was functionalized with biolinker for the detection of carcinoembryonic antigen (CEA). The proposed immunosensor exhibited good responses towards CEA detection, with a 4.25 pg/ml LOD and correlation coefficient of R2 = 0.99 within a linear working range from 0.01 to 10 ng/ml. The performance of the immunosensor to detect CEA present in human serum was also evaluated. Good recovery of CEA was found, suggesting that the proposed immunosensor possess a high affinity to CEA even in a complex biological matrix, rendering it a promising sensing platform for real sample analysis and open a new way for the detection of cancer-associated proteins.

Novel magnetic organic-inorganic hybrids based on aromatic polyamides and ZnFe2O4 nanoparticles with biological activity.

Magnetic nanoparticles were creatively selected as stable, inexpensive, biodegradable, facile recoverable, and functionalizable supports for a variety of synthetic and natural polymers. Herein, for the first time, aromatic polyamide was synthesized on the magnetic core of zinc iron oxide (ZnFe2O4). Terephthaloyl chloride and derivations of phenylenediamine were employed as monomers in this polymerization process. The toxicity of the synthesized hybrid at the highest concentration (1000 µg/ml) is 13.65% and on the other hand, the cell viability percentage is 86.35%. So, the prepared hybrid is biocompatible and non-toxic to Hu02 cells. Also, it has antibacterial ability against gram-positive and gram-negative bacteria. Because the results show that the minimum inhibitory concentration (MIC) of the synthesized polymer for bacteria such as Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853 is in the range of 500-1000 µg/ml. Moreover, the hemolytic effect of ZnFe2O4 based hybrid was below 9% at the concentration of 1000 µg/ml. Therefore, it is compatible with red blood cells.

MP-SeNPs; A Promising Cytokines Suppressor in Benzo[a]pyrene-Induced Mammal Tissue Injury in Rats.

<b>Background and Objective:</b> <i>Moringa peregrina</i> (family Moringaceae) is a common flowering plant found in the Arabian Peninsula, Horn of Africa and Southern Sinai, Egypt. The purpose of this study was to investigate the protective activity of MP-SeNPs against BaP-induced mammal tissue injury in rats. <b>Materials and Methods:</b> MP-SeNPs were prepared and characterized in terms of particle size and zeta potential. Furthermore, the IC₅₀ of MP-SeNPs against the Mcf7 breast carcinoma cell line and LD₅₀ was evaluated. Adult albino rats weighing approximately 187±10 g was used to assess the lung protective activity of MP-SeNPs (28.7 and 71.75 mg kg¹ b.wt.) against BaP-induced mammal tissue injury in rats. <b>Results:</b> The mean particle size of MP-SeNPs was 134.69±8.24 nm with negative zeta potential of +26.04 with the observed shapes of nano particle was spherical. Also, IC₅₀ of MP-SeNPs against Mcf7 breast carcinoma cell line = 89.57 µg mL¹ and LD₅₀ equals and 1435 mg kg¹ b.wt., respectively. The daily oral administration of MP-SeNPs at concentrations of 28.7 and 71.75 mg kg¹ b.wt. for 30 days to rats treated with BaP (20 mg kg¹ b.wt.) resulted in a significant improvement of IL-2, IL-6 and IL-10. Oral administration of MP-SeNPs, on the other hand, increased the levels of SOD, GPx, TNF-α, iNOs and GSH as well as decreased the level of MDA in mammal tissue of BaP-treated rats. Furthermore, MP-SeNPs almost normalized these effects in mammal tissue histoarchitecture and MRI examination. <b>Conclusion:</b> The biochemical, histological and MRI findings incurrent study demonstrated that MP-SeNPs have protective activity against BaP-induced mammal tissue injury in rats.

Antimutagenic, Cytoprotective and Antioxidant Properties of Ficus deltoidea Aqueous Extract In Vitro.

Ficus deltoidea var. deltoidea is used as traditional medicine for diabetes, inflammation, and nociception. However, the antimutagenic potential and cytoprotective effects of this plant remain unknown. In this study, the mutagenic and antimutagenic activities of F. deltoidea aqueous extract (FDD) on both Salmonella typhimurium TA 98 and TA 100 strains were assessed using Salmonella mutagenicity assay (Ames test). Then, the cytoprotective potential of FDD on menadione-induced oxidative stress was determined in a V79 mouse lung fibroblast cell line. The ferric-reducing antioxidant power (FRAP) assay was conducted to evaluate FDD antioxidant capacity. Results showed that FDD (up to 50 mg/mL) did not exhibit a mutagenic effect on either TA 98 or TA 100 strains. Notably, FDD decreased the revertant colony count induced by 2-aminoanthracene in both strains in the presence of metabolic activation (p < 0.05). Additionally, pretreatment of FDD (50 and 100 µg/mL) demonstrated remarkable protection against menadione-induced oxidative stress in V79 cells significantly by decreasing superoxide anion level (p < 0.05). FDD at all concentrations tested (12.5-100 µg/mL) exhibited antioxidant power, suggesting the cytoprotective effect of FDD could be partly attributed to its antioxidant properties. This report highlights that F. deltoidea may provide a chemopreventive effect on mutagenic and oxidative stress inducers.

Visible colorimetric growth indicators of Neisseria gonorrhoeae for low-cost diagnostic applications.

N. gonorrhoeae is one of the most pressing antibiotic resistant threats of our time and low-cost diagnostics that can easily identify antibiotic resistance are desperately needed. However, N. gonorrhoeae responds so uniquely to growth conditions that it cannot be assumed gonorrhea will respond to common microbiological methods used for other pathogenic organisms. In this paper, we explore visual colorimetric indicators of N. gonorrhoeae growth that can be seen without a microscope or spectrophotometer. We evaluate growth media, pH indicators, resazurin-based dyes, and tetrazolium-based dyes for their use in simple colorimetric system. Overall, we identified Graver Wade media as the best at supporting robust gonococcal growth while also providing the least background when analyzing results of colorimetric tests. XTT, a tetrazolium-based dye, proved to show to brightest color change over time and not negatively impact the natural growth of N. gonorrhoeae. However, other dyes including PrestoBlue, MTT, and NBT are less expensive than XTT and work well when added after bacterial growth has already occurred. By identifying the specific use cases of these dyes, this research lays the groundwork for future development of a color-based antibiotic susceptibility low-cost test for N. gonorrhoeae.

Piperlongumine Analogs Promote A549 Cell Apoptosis through Enhancing ROS Generation.

Chemotherapeutic agents, which contain the Michael acceptor, are potent anticancer molecules by promoting intracellular reactive oxygen species (ROS) generation. In this study, we synthesized a panel of PL (piperlongumine) analogs with chlorine attaching at C2 and an electron-withdrawing/electron-donating group attaching to the aromatic ring. The results displayed that the strong electrophilicity group at the C2-C3 double bond of PL analogs plays an important role in the cytotoxicity whereas the electric effect of substituents, which attached to the aromatic ring, partly contributed to the anticancer activity. Moreover, the protein containing sulfydryl or seleno, such as TrxR, could be irreversibly inhibited by the C2-C3 double bond of PL analogs, and boost intracellular ROS generation. Then, the ROS accumulation could disrupt the redox balance, induce lipid peroxidation, lead to the loss of MMP (Mitochondrial Membrane Potential), and ultimately result in cell cycle arrest and A549 cell line death. In conclusion, PL analogs could induce in vitro cancer apoptosis through the inhibition of TrxR and ROS accumulation.

SN38 loaded nanostructured lipid carriers (NLCs); preparation and in vitro evaluations against glioblastoma.

SN38 is the active metabolite of irinotecan with 1000-fold greater cytotoxicity compared to the parent drug. Despite the potential, its application as a drug is still seriously limited due to its stability concerns and low solubility in acceptable pharmaceutical solvents. To address these drawbacks here nanostructured lipid carrier (NLC) containing SN38 was prepared and its cytotoxicity against U87MG glioblastoma cell line was investigated. The formulations were prepared using hot ultrasonication and solvent evaporation/emulsification methods. NLCs with a mean size of 140 nm and particle size distribution (PDI) of 0.25 were obtained. The average loading efficiency was 9.5% and its entrapment efficiency was 81%. In order to obtain an accurate determination of released amount of SN38 a novel medium and extraction method was designed, which lead to an appropriate in vitro release profile of the drug from the prepared NLCs. The MTT test results revealed the significant higher cytotoxicity of NLCs on U87MG human glioblastoma cell line compared with the free drug. The confocal microscopy images confirmed the proper penetration of the nanostructures into the cells within the first 4 h. Consequently, the results indicated promising potentials of the prepared NLCs as a novel treatment for glioblastoma.

Bio-corrosion impacts on mechanical integrity of ZM21 Mg for orthopaedic implant application processed by equal channel angular pressing.

The mechanical integrity of rolled ZM21 Mg was improved by equal channel angular pressing (ECAP) to function as a potential biodegradable bone screw implant. Electron backscattered diffraction (EBSD) revealed deformed grains of 45 µm observed in rolled ZM21 Mg. They were transformed to equiaxed fine grains of 5.4 µm after 4th pass ECAP. The yield strength of rolled and ECAPed ZM21 Mg alloys were comparable. In contrast, 4th pass ZM21 Mg exhibited relatively higher elongation when compared to rolled sample. The mechanical properties of rolled and ECAPed ZM21 Mg were dependant on both grain refinement and crystallographic texture. The rolled and 4th pass ECAPed tensile samples exhibited nonlinear deterioration of mechanical properties when tested after 7, 14, 21 and 28 days immersion in Hank's solution. The evaluation signifies that regardless their processing condition, ZM21 Mg alloys are suitable for surgical areas that requires high mechanical strength. In addition, the 4th pass ECAP samples were viable to MG-63 cells proving themselves to be promising candidates for future in vivo studies.

Automated antimicrobial susceptibility testing of slow-growing Pseudomonas aeruginosa strains in the presence of tetrazolium salt WST-1.

Slow growing, mucoid isolates of Pseudomonas aeruginosa require adaptation of the protocol used for automated antimicrobial susceptibility testing (AST). In the present study we used a water soluble tetrazolium salt WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate) in combination with menadione for possibly improving AST of slow growing and biofilm-forming P. aeruginosa isolates from cystic fibrosis (CF) patients. WST-1 and menadione addition ensures sensitive detection of microbial growth increase in the presence of antibiotics that may remain undetected with the automated VITEK® 2 method. We observed that 32.8% of P. aeruginosa isolates from CF and bronchiectasis patients produced an elevated absorbance signal intensity thereby increasing the sensitivity while maintaining the accuracy of VITEK 2. Our study merits future investigation with other slow growing pathogenic bacterial species.