Point-of-care testing (POCT) of pathogenic bacteria at low concentrations is vital to early warning of bacterial contaminations. A disposable centrifuge tube was reconstructed in this study for sensitive Salmonella detection in large-volume samples, where the entire bacterial detection progress from separation to detection, was performed within the tube. The bottom of this centrifuge tube was assembled with a flexible stirrer containing a pair of circular magnets, which was rapidly rotated using a DC motor to produce the vortex for simultaneous mixing and capture of target bacteria. Besides, immune manganese dioxide nanoflowers were synthesized and used to label target bacteria, followed by mimicking catalyze colorless TMB substrate into blue TMBox product. The product image was captured and analyzed by a smartphone App to quantitatively determine the target bacteria. This POCT centrifuge tube effectively achieved a separation efficiency of approximately 80 % for target bacteria from a 10 mL sample, enabling the detection of target bacteria within the range of 1.3 × 10 1 to 1.3 × 10 4 CFU/mL in 1 h, with a low detection limit of 13 CFU/mL. More importantly, this reconstructed centrifuge tube demonstrated its potential as a laboratory consumable for bacterial detection in routine screening owing to the features of low cost, easy operation and high integration.
In this study, a novel colorimetric sensing platform was developed for the detection of S. aureus using dog immunoglobulin G (IgG) as the capture antibody and chicken anti-protein A immunoglobulin Y labeled with horseradish peroxidase (HRP-IgY) as the detection antibody. Dog IgG labeled with magnetic beads was used to capture S. aureus through the interaction between the Fc region of dog IgG and Staphylococcal protein A (SPA). HRP-IgY was introduced to recognize the residual SPA on the surface of S. aureus and to create a sandwich format, after which a soluble 3,3′,5,5′-tetramethylbenzidine (TMB) substrate was added. A stop solution was utilized to cease the enzymatic chromogenic reaction, and then optical density was read at 450 nm. Under optimal conditions, the proposed method displayed a low detection limit of 1.0 × 103 CFU mL−1 and a wide linear range of 3.1 × 103 to 2.0 × 105 CFU mL−1. This detection method exhibited high specificity against other foodborne bacteria. The recovery rates ranged from 95.2% to 129.2%. To our knowledge, this is the first report to employ dog IgG and chicken IgY as an antibody pair to detect S. aureus. This technique exhibits high application potential for S. aureus monitoring in various kinds of samples.
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