Colorimetric Systems for the Detection of Bacterial Contamination: Strategy and Applications

Abstract

Bacterial contamination is a public health concern worldwide causing enormous social and economic losses. For early diagnosis and adequate management to prevent or treat pathogen-related illnesses, extensive effort has been put into the development of pathogenic bacterial detection systems. Colorimetric sensing systems have attracted increasing attention due to their simple and single-site operation, rapid signal readout with the naked eye, ability to operate without external instruments, portability, compact design, and low cost. In this article, recent trends and advances in colorimetric systems for the detection and monitoring of bacterial contamination are reviewed. This article focuses on pathogen detection strategies and technologies based on reaction factors that affect the color change for visual readout. Reactions used in each strategy are introduced by dividing them into the following five categories: external pH change-induced pH indicator reactions, intracellular enzyme-catalyzed chromogenic reactions, enzyme-like nanoparticle (NP)-catalyzed substrate reactions, NP aggregation-based reactions, and NP accumulation-based reactions. Some recently developed colorimetric systems are introduced, and their challenges and strategies to improve the sensing performance are discussed.

Optical Methods for Label-Free Detection of Bacteria

“…Compared with the label-free optical methods, the paper based colorimetric methods have attracted increasing attention due to their simplicity and cost-effectiveness, as well as the rapid signal readout with the naked eye, making them a promising candidate for the development of point of care devices [ 132 ]. However, the colorimetric methods are largely compromised by relatively poor sensitivity.…”

Microfluidic-based colorimetric nucleic acid detection of pathogens

“…32 Some significant advantages of colorimetric readouts include ease of interpretation, label-free signal transduction, cost-effectiveness, and simplicity. 33 The color sensing schemes when coupled with nucleic acid detection assays for pathogens, are broadly categorized into (a) pH responsive colorimetric change, 34 (b) color-change via chromogenic indicators, 35 (c) colorimetric or florescence change via intercalating dyes, 36 (d) nanoparticle mediated colorimetric change. 37 One notable obstacle with colorimetric readout is that the human eye is insensitive to low level color contrasts; thus, discriminating outputs between distinct samples is difficult with the naked eye since most conventional colorimetric approaches primarily depend on the colored output's optical density variation.…”

Electrochemiluminescence Systems for the Detection of Biomarkers: Strategical and Technological Advances

“…The catalytic activity of some NPs is similar to that of enzymes, which triggers redox reactions and energy transfer, which in turn induces ECL emissions from the luminophore. Compared with natural enzymes, using nanozymes can reduce the costs associated with the synthesis and mass production and provides several advantages such as the resistance to harsh environments (e.g., pH and temperature) and facile functionalisation [ 80 , 81 , 82 ]. Nanozymes include peroxidase, oxidase, catalase, and hydrolase mimics such as Fe 3 O 4 , metallic oxide NPs (Co 3 O 4 and CeO 2 ), and noble metal NPs (AuNPs, Ag/PtNPs, and Au/PdNPs).…”