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. 2022 Jul 16;12(7):532. doi: 10.3390/bios12070532

Figure 1.

Figure 1

Colorimetric sensing strategy based on external pH change-induced pH indicator reactions. (A) Detection of Listeria monocytogenes using an antibody (Ab), urease-modified magnetic nanobeads, and gold nanoparticles (AuNPs). Reprinted with permission from [19]. Copyright 2017, Elsevier. (B) Detection of Salmonella typhimurium using silver ions and urease. This strategy is based on the Ag-induced inhibition of urease activity and Ag ion utilization. Reprinted with permission from [21]. Copyright 2020, Springer Nature. (C) Detection of Escherichia coli and S. typhimurium using two different pH-responsive NPs, which were made using PP or TP. Reprinted with permission from [22]. Copyright 2022, Elsevier. (D) Detection of bacterial spoilage using a paper-based pH indicator consisting of BTB and BCG. Quantification can be performed using RGB analysis software on a smartphone. Reprinted with permission from [23]. Copyright 2021, Royal Society of Chemistry. PEI, polyethyleneimine; BSA, bovine serum albumin; RGB, red-green-blue.