A simple colorimetric method for viable bacteria detection based on cell counting Kit-8

In this study, Cell Counting Kit-8 (CCK-8) was introduced to detect the concentration of live bacteria for the first time depending on the redox reaction between CCK-8 solution and dehydrogenase. CCK-8 solution can be reduced to form water soluble orange-yellow formazan by the dehydrogenase present in bacterial cells, and the concentration of live bacteria is proportional to the absorbance value of formazan at 450 nm. Based on this principle, Staphylococcus aureus and Escherichia coli were chosen as the model bacteria. The optimal detection conditions were investigated and a good linear relationship was obtained in the concentration range from 2.600 × 102 to 1.160 × 109 CFU mL-1 with a linear equation of Y = 0.06305 log10 X-0.1153 (X in CFU mL-1R2 = 0.9747) for S. aureus and 9.750 × 102 to 6.000 × 108 CFU mL-1 with a linear equation of Y = 0.06122 log10 X-0.1358 (X in CFU mL-1R2 = 0.9958) for E. coli.
The CCK-8 based viable bacteria detection method can be completed within 2 h with a wide bacterial detection concentration range. Satisfactory results were obtained when applied to an actual sample analysis and there is a good consistency between the proposed CCK-8 based method and the traditional plate counting method. More importantly, this method can realize the one-time detection of a large number of samples with high sensitivity, which suggests its great potential in high-throughput bacterial detection.

A Novel Imidazole Bound Schiff Base as Highly Selective “Turn-on” Fluorescence Sensor for Zn 2+ and Colorimetric Kit for Co 2

An imidazole based Schiff base (2-[(1H-imidazole-2-ylmethylene)-amino]-4-methyl-phenol) (IMP), with an imine unit, has been designed and characterized by various standard methods. The evaluation of the probe as a fluorogenic sensor for Zn2+ and a chromogenic sensor for Co2+ has been rationalized in terms of the PET mechanism. In the presence of Zn2+, a light yellow colored solution of IMP with maximum absorption of 364 nm becomes bright yellow with maximum absorption of 410 nm and a measurable fluorescent signal at 612 nm with bathochromic enhancement.
The sensitivity of the fluorescent based assay (6.78 × 10-9 M) for Zn2+ is far below the limit in the World Health Organization (WHO) guidelines for drinking water (7.6 × 10-5 M) and therefore it is capable of being a practical system for the monitoring of Zn2+ concentrations in aqueous samples. Moreover, IMP showed a highly selective colorimetric response to Co2+ by displayed an obvious pink color upon addition of metal solution immediately without any interference from other ions. These results provide a new approach for selectively recognizing the two most important trace elements in the human body simultaneously, for Zn2+ by emission spectra and Co2+ by the naked eye.

Profile and correlates of colorimetric reagent kit use among people who use ecstasy/MDMA and other illegal stimulants in Australia

Background: Colorimetric reagent kits can provide information about the compounds present in drug samples. This study aimed to identify patterns and correlates of colorimetric reagent kit use, as well as behavioural outcomes of testing, amongst people who use illegal stimulants in a context that lacks permanent government-sanctioned drug checking services.
Methods: Australians residing in capital cities who reported regularly using ecstasy/MDMA and/or other illegal stimulants ≥monthly in the past six months were recruited via social media and word-of-mouth from April-July 2019 (N = 792). Participants were asked about testing the contents and/or purity of illegal drugs, and features of last colorimetric reagent kit use. Logistic regression identified correlates of last using a kit (referent: no use of drug checking technology to test drug contents/purity in the past year).
Results: Over one-third (36%) reported testing drug contents and/or purity; of this group, 86% had last used a colorimetric reagent kit. On the last occasion, 52% reported someone else had conducted testing; 58% said testing occurred <24 h before planned drug use; and 24% reported testing for quantity of a substance. Correlates of drug checking comprised: being younger, male, past six-month use of new psychoactive substances, accessing community-based health services for alcohol or other drug reasons, selling drugs for cash profit, obtaining information from peers who had tried the drug, and searching online for reports of the drug by stamp/appearance. The majority (84%) tested a substance they had been sold and/or given as MDMA; of these, 87% detected MDMA. Of those who expected and detected MDMA, 29% and 11% reported results to their peers and dealer, respectively.
Conclusion: People who use ecstasy/MDMA and/or other illegal stimulants seek out objective information about substance contents. In countries that lack permanent government-sanctioned drug checking services, it is important to acknowledge that people already engage in drug checking but with suboptimal technologies and without tailored specialist advice and education.

Correlation between L-Lactate Concentrations in Beef Cattle, Obtained Using a Hand-Held Lactate Analyzer and a Lactate Assay Colorimetric Kit

  • Lactate is a product of anaerobic glycolysis, used in animal research as an indicator of muscle fatigue. Therefore, it has been used as an indicator of cattle response to long distance transportation. The aim of this study was to assess the relationship of L-lactate concentrations measured using a Lactate Scout+ analyzer and a traditional lactate assay colorimetric kit. Blood samples were collected by venipuncture from 96 steers (Black or Red Angus × Hereford/Simmental and Black or Red Angus × Charolais; 247 ± 38.2 kg BW) prior to loading (LO1) and after 36 h of transport, and prior to reloading and after an additional 4 h of road transportation, and on d 1, 2, 3, 5, 14, and 28 after transport.
  • The Lactate Scout+ analyzer strip was dipped in blood at the time of sampling, while blood samples were collected into sodium fluoride tubes for use in the colorimetric analysis. Pearson correlations were calculated to assess the strength of the relationship between the experimental methods for the quantification of L-lactate concentrations. The magnitude and direction of the correlation, and the level of statistical significance varied over the observed time points, ranging from r = -0.03 (p = 0.75; LO1) to r = 0.75 (p < 0.0001; d 3).
  • The correlation for the pooled data was weak but statistically significant (r = 0.33, p < 0.0001). Based on the low magnitude of the correlation due to variability across sampling time points in this study, the Lactate Scout+ analyzer is not a suitable alternative to a lab-based assay (considered the gold standard) for measuring L-lactate in transported cattle.

Colorimetric DTT Assay kit

DTT100C 100 assays 221.78 EUR

AMP Colorimetric Assay Kit

K229-100 each 692.4 EUR

Heme Colorimetric Assay Kit

K672-100 each 588 EUR

Urea Colorimetric Assay Kit

K375-100 each 646.8 EUR

Zinc Colorimetric Assay Kit

K387-100 each 588 EUR

Heme Colorimetric Assay Kit

K2215-100 100 assays 602.4 EUR

Iron Colorimetric Assay Kit

K2069-100 100 assays 652.8 EUR

Iron Colorimetric Assay Kit

K390-100 each 660 EUR

Zinc Assay Kit (Colorimetric)

MET-5138 100 assays 410 EUR

cAMP ELISA Kit (Colorimetric)

STA-500 96 assays 706.8 EUR

cAMP ELISA Kit (Colorimetric)

STA-500-5 5 x 96 assays 2558.4 EUR

cGMP ELISA Kit (Colorimetric)

STA-505 96 assays 706.8 EUR

cGMP ELISA Kit (Colorimetric)

STA-505-5 5 x 96 assays 2558.4 EUR

HDAC colorimetric assay kit

TBS2065 100 tests 289 EUR

PTP1B Colorimetric Assay Kit

30019 96 rxns. 425 EUR

PARP1 Colorimetric Assay Kit

80580 96 rxns. 640 EUR

PARP2 Colorimetric Assay Kit

80581 96 rxns. 875 EUR

Malate Colorimetric Assay Kit

K637-100 each 588 EUR

Cobalt Colorimetric Assay Kit

K505-100 each 548.4 EUR

Nickel Colorimetric Assay Kit

K510-100 each 548.4 EUR

Starch Assay Kit (Colorimetric)

MET-5025 100 assays 574.8 EUR

Malate Colorimetric Assay Kit

K2139-100 100 assays 602.4 EUR

Sodium Assay Kit (Colorimetric)

K391-100 each 927.6 EUR

Malate Assay Kit (Colorimetric)

MET-5119 200 assays 395 EUR

Lysine Assay Kit (Colorimetric)

MET-5130 100 assays 525 EUR

Taurine Assay Kit (Colorimetric)

K988-100 each 777.6 EUR

The Stimulus Response of TPE-TS@Eu/GMP ICPs: Towards Colorimetric Sensing of Anthrax Biomarker with Double Ratiometric Fluorescence and Its Coffee Ring Test Kit for Point-of-Use Application

In this work, by fully exploring the stimulus response of infinite coordination polymer nanoparticles (ICPs) and by taking advantage of the particular optical properties of ICP guest tetra(4-sulfophenyl)ethene (TPE-TS) with adjustable monomer emission (ME) and aggregation-induced emission (AIE), we demonstrated a novel sensing mechanism for Anthrax biomarker dipicolinic acid (DPA) based on the competitive coordination interaction regulating the structure of TPE-TS@Eu/GMP ICPs. The double ratiometric fluorescence stemming from triple response of TPE-TS@Eu/GMP ICPs without spectral cross interference (ME and AIE from TPE-TS and sensitized emission from Eu/DPA) and a corresponding blue-to-red fluorescent color change which not only benefited the direct detection of DPA with high sensitivity and selectivity, but also offered a great opportunity to realize real-time monitoring of DPA released by Bacillus subtilis spores.
Furthermore, the coffee ring deposition patterns on test paper were innovatively tuned by the quantity and morphology changes of TPE-TS@Eu/GMP ICPs during their stimulus response towards DPA, which could be exploited as expanded signal channels. By integrating a multi-channel responsive coffee ring test kit with image recognition and processing application installed on smart-phones, point-of-use analysis of DPA could be realized in a low-cost and high-throughput fashion.

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