Electrochromogenic Detection of Live Bacteria Using Soluble and Insoluble Prussian Blue

Abstract

Microbial detection is crucial for the control and prevention of infectious diseases, being one of the leading causes of mortality worldwide. Among the techniques developed for bacterial detection, those based on metabolic indicators are progressively gaining interest due to their simplicity, adaptability, and, most importantly, their capacity to differentiate between live and dead bacteria. Prussian blue (PB) may act as a metabolic indicator, being reduced by bacterial metabolism, producing a visible color change from blue to colorless. This molecule can be present in two main forms, namely, the soluble and the insoluble, having different properties and structures. In the current work, the bacterial-sensing capacity of soluble and insoluble PB will be tested and compared both in suspensions as PB-NPs and after deposition on transparent indium tin oxide-poly­(ethylene terephthalate) (ITO-PET) electrodes. In the presence of live bacteria, PB-NPs are metabolized and completely reduced to the Prussian white state in less than 10 h for soluble and insoluble forms. However, when electrodeposited on ITO-PET substrates, less than 1 h of incubation with bacteria is required for both forms, although the soluble one presents faster metabolic reduction kinetics. This study paves the way to the use of Prussian blue as a metabolic indicator for the early detection of bacterial infection in fields like microbial diagnostics, surface sterilization, food and beverage contamination, and environmental pollution, among others.

Determination of W(V) in WO3 Photochromism Using Localized Surface Plasmon Resonance of Ag Nanoparticles

“…Furthermore, from the plots of A 775 against the concentration of W­(V) in Table , the molar absorption coefficient for the IVCT transition between W­(V) and W­(VI) is evaluated to be 6.85 × 10 3 dm 3 mol –1 cm –1 according to the Lambert-Beer law (Figure S4). Our data indicate that the IVCT transition between the photogenerated W­(V) and W­(VI) in WO 3 has a molar absorption coefficient close to that of Prussian Blue. , …”

“…Our data indicate that the IVCT transition between the photogenerated W(V) and W(VI) in WO 3 has a molar absorption coefficient close to that of Prussian Blue. 10,11 ■ CONCLUSIONS…”

“…Mixed-valence compounds are promising for the application of smart windows and electrochromic display devices or sensors. − Prussian Blue (Fe 4 [Fe­(CN) 6 ] 3 ) is well known as a mixed-valence hexacyanometalate and exhibits blue color due to intervalence charge transfer (IVCT) from Fe­(II) to Fe­(III). − A molar extinction coefficient of a soluble form as KFe­[Fe­(CN) 6 ] has been reported to be 8.4 × 10 3 dm 3 mol –1 cm –1 at 716 nm or 3.0 × 10 4 dm 3 mol –1 cm –1 at 700 nm . When phosphomolybdic anion (PMo 12 O 40 3– ), which is produced by the reaction of MoO 4 2– with PO 4 3– , is reduced by a reducing agent such as ascorbic acid, the color changes from yellow to blue owing to the IVCT transition from Mo­(V) to Mo­(VI).…”

Portable Prussian Blue-Based Sensor for Bacterial Detection in Urine

“…PrBl has recently been used in the design of a variety of portable or wearable analytical devices, all of which were further modified with enzymes, and enzymatic reduction of PrBl to Prussian white (PrWh) was detected amperometrically [ 22 , 23 , 24 ]. Furthermore, ferricyanide is a common metabolic indicator for both Gram-positive and Gram-negative bacteria, and recent studies have shown that PrBl can be reduced to PrWh through the metabolic activity of a variety of microorganisms, including E. coli , a feature that has been used to design electrochromic sensors for bacteria [ 25 , 26 , 27 , 28 ].…”

Simultaneous Optical Detection of Multiple Bacterial Species Using Nanometer-Scaled Metal–Organic Hybrids

“…Numerous bacterial species are vital for improving safety and quality of life across several fields, including drug discovery, food production, sewage treatment, and energy harvesting; however, some bacteria are harmful. Bacterial tests, such as those performed in various areas, including food, medical, and environmental research, must meet requirements for sensitivity, selectivity, speed, and cost. − In recent years, much research has been actively conducted on the development of bacterial tests, whose principles range from luminescence, , absorption, , or current response-based detections − to the combination of microscopy or spectroscopy and deep learning. While these developments have many benefits in terms of sensitivity, selectivity, speed, and cost, they require sufficient development time to replace traditional methods.…”