Background: Mycobacterium tuberculosis (MTB) is a pathogen causing tuberculosis (TB) in human, and TB can cause enormous social and economic disruptions. Lateral flow test strips (LFTSs) are inexpensive, portable, disposable, rapid, and easy-to-use analytical tools. Objective: LFTSs were prepared for the detection of MTB. LFTSs were fabricated using a new specific probe for MTB H37Rv, based on IS6110 sequence gene, and tailed with poly deoxyadenine (dA). Material and Methods: In this experimental study, to create test and control zones, streptavidin (STP) and a 150-mer dA were dotted on a nitrocellolose membrane. Gold nanoparticles (GNPs) were conjugated with poly deoxythymidine sequence and placed on the conjugate pad. The composition of immersion buffers for sample pad and conjugate pad, running solution, solutions of GNPs-S-dT150 and STP were introduced. DNA genome of MTB and Mycobacterium bovis in clinical samples was amplified with PCR, and then detected by the LFTSs. During the assay, samples were firstly hybridized in two steps and then placed on a conjugate pad in a manner that positive and negative samples provided two and one red lines, respectively, on the detection pad. Results: After PCR reaction with biotinylated primer, hybridization process with specific MTB probe-dA70-100 toke 10 min, and running process on the strip was performed within 5 min. Conclusion: We showed that LFTS can discriminate a particular bacteria strain from others. The LFTSs can be redesigned for detection of other pathogenic genomes.

We present the construction of a biodegradable colorimetric sensor on the microtube lid for formaldehyde determination via Naked-eye detection and /or UV–Vis spectrophotometry. Alizarin Red S (ARS) was subjected as the effective reagent for formaldehyde detection by incorporation in a thin film of starch. The sensor was accredited by the reaction of formaldehyde with ARS based on a color response from purple to yellow at pH 12. The sensor characterization was obtained by Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray (EDX) spectroscopy analytical methods. The effect of the main parameters on the detection of formaldehyde was studied and optimized. Under optimal conditions, the linearity range of colorimetric response was obtained in the concentration range of 0.15-10 mg L−1 with a determination coefficient (R2) of 0.9923. A limit of detection (LOD) of 0.05 mg L−1 and a relative standard deviation (RSD, n=5) of 1.2 % were achieved. This method presented a short response time (within 15 min) for the application as biosensing. Subsequently, the concentrations of formaldehyde in hair care products (hair shampoo and conditioner samples) were successfully obtained with good recoveries.

Herein, a simple, sensitive, and rapid chemosensor is reported for the colorimetric detection and determination of oxalate ions. This system produces a visible color change from purple to yellow based on the indicator displacement assay (IDA) approach. The reaction of Eriochrome Cyanine R (ECR) as an indicator and vanadyl ions (VO2+) at pH 6. 00 acts as a chemosensor for oxalate ions (Ox). Adding oxalate ions to the designed chemosensor causes the replacement of the vanadyl ions with the oxalate ions to binding the indicator. Due to this displacement, the solution color returns to yellow with about 80 nm blue shifts (530 to 450 nm). Also, the formation constants of ECRVO2+ and VO2+-Ox complexes were determined to be 6. 13 and 13. 94, respectively using spectrophotometric titration. Under the optimized experimental conditions, the chemosensor exhibited a dynamic linear range for oxalate ions from 8. 30 × 10-7-1. 13 ×10-4 M, with a detection limit (S/N = 3) of 5. 40 × 10-7 M. The relative standard deviation (RSD) value was evaluated to be 0. 52% for five determinations of oxalate (6. 02 μ M). The designed sensor was applied successfully for the determination of oxalate ions in human urine samples with the recoveries of 96. 36 to 105. 73% showing satisfactory results.