Red cabbage extract-mediated colorimetric sensor for swift, sensitive and economic detection of urease-positive bacteria by naked eye and Smartphone platform

Abstract

The bacterial pathogens have caused various serious infectious diseases in the human body, and even some threats to human life by leading to deaths. Enterobacteriaceae species especially urease positive ones, Proteus mirabilis (P. mirabilis) and Klebsiella pneumoniae (K. pneumoniae), show resistance to antibiotics and cause respiratory and urinary tract infections. We have developed natural indicator-incorporated colorimetric urease tests with a naked eye and smartphone readout to rapidly, sensitively and economically detect P. mirabilis and K. pneumoniae. We utilized anthocyanin found as a predominant component in red cabbage (Brassica oleracea) extract as a natural pH indicator instead of toxic and synthetic indicators. As a mechanistic explanation for the detection of P. mirabilis and K. pneumoniae, urease enzymes secreted from the P. mirabilis and K. pneumoniae hydrolyze urea to produce ammonia (NH3), which increases the pH value of the reaction environment and leads to deprotonation from anthocyanins. The changes in the molecular structure and electronic structure of anthocyanins are responsible for revealing many different colors. We demonstrated how some reaction parameters including the concentration of the bacteria (colony-forming unit, CFU), the concentration of anthocyanin in the tests, initial color and pH values (pHs) of the tests influence their detection performance. We further developed a 3D-printed smartphone platform with smartphone based digital image processing software to improve the detection limit and shorten the detection time. We claim that natural indicator-incorporated rapid urease tests providing colorimetric readout evaluated by the human eye and smartphone imaging processing has great potential in practical use and they can be implemented in clinics.

Recent Developments in the Design and Fabrication of Electrochemical Biosensors Using Functional Materials and Molecules

“…There are various sophisticated technologies and methodologies, such as high-pressure liquid chromatography, mass spectrometry, chemiluminescence, capillary zone electrophoresis, fluorimetry, calorimetry, electrochemical sensors, biosensors, DNA microarrays, PCR, ELISA, and other immunosorbent assays, being used for the detection and quantification of target analytes. However, most of these techniques are expensive and time-consuming, and require skilled manpower, tedious sample pretreatment, and huge instrumentation setup [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Among them, the electrochemical biosensor is the most preferred technology due to its robustness, simplicity, rapidity, portability, cost-effectiveness, ease of handling, high sensitivity, and selectivity toward target analytes, in addition to reliable and reproducible responses [ 24 , 25 , 26 , 27 , 28 ].…”

Recent Advances in Colorimetric Tests for the Detection of Infectious Diseases and Antimicrobial Resistance

“…Due to the use of a biocompatible pH indicator, anthocyanin, incorporated in these colorimetric phenotypic tests, and a quite economical structure, these colorimetric phenotypic tests have a great potential to be practically used in clinics. Furthermore, anthocyaninincorporated tests have also been utilized for the detection of urinary tract infection (UTI) pathogens [50,56]. Celik et al also developed a test for the use in clinical laboratories to detect UTI.…”

“…In addition to that, a smartphone platform is printed on a 3D printer to minimize the factors affecting the analysis of the mobile application. With the smartphone platform and mobile application, the color change in the diagnostic test can be analyzed very precisely and quickly [56].…”