Sepsis is a serious bloodstream infection where the immunity of the host body is compromised, leading to organ failure and death of the patient. In early sepsis, the concentration of bacteria is very low and the time of diagnosis is very critical since mortality increases exponentially with every hour after infection. Common culture-based methods fail in fast bacteria determination, while recent rapid diagnostic methods are expensive and prone to false positives. In this work, we present a sepsis kit for fast detection of bacteria in whole blood, here achieved by combining selective cell lysis and a sensitive colorimetric approach detecting as low as 10³ CFU/mL bacteria in less than 5 h. Homemade selective cell lysis buffer (combination of saponin and sodium cholate) allows fast processing of whole blood in 5 min while maintaining bacteria alive (100% viability). After filtration, retained bacteria on filter paper are incubated under constant illumination with the electrochromic precursors, i.e., ferricyanide and ferric ammonium citrate. Viable bacteria metabolically reduce iron(III) complexes, initiating a photocatalytic cascade toward Prussian blue formation. As a proof of concept, we combine this method with antibiotic susceptibility testing to determine the minimum inhibitory concentration (MIC) using two antibiotics (ampicillin and gentamicin). Although this kit is used to demonstrate its applicability to sepsis, this approach is expected to impact other key sectors such as hygiene evaluation, microbial contaminated food/beverage, or UTI, among others.

• Sonochemical production of smart hospital textiles able to detect live bacteria by changing its own colour. • Sonochemical coating of Prussian Blue nanoparticles in a single-step and scalable ultrasonic process. • Use of Prussian Blue as electrochromic metabolic indicator for live bacterial detection. • Textile colour change is produced by bacterial metabolism, either by Gram-negative or Gram-positive bacteria.

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.

The detection of living organisms at very low concentrations is necessary for the early diagnosis of bacterial infections, but it is still challenging as there is a need for signal amplification. Cell culture, nucleic acid amplification, or nanostructure-based signal enhancement are the most common amplification methods, relying on long, tedious, complex, or expensive procedures. Here, we present a cyanotype-based photochemical amplification reaction enabling the detection of low bacterial concentrations up to a single-cell level. Photocatalysis is induced with visible light and requires bacterial metabolism of iron-based compounds to produce Prussian Blue. Bacterial activity is thus detected through the formation of an observable blue precipitate within 3 h of the reaction, which corresponds to the concentration of living organisms. The short time-to-result and simplicity of the reaction are expected to strongly impact the clinical diagnosis of infectious diseases.

The early detection of very low bacterial concentrations is key to minimize the healthcare and safety issues associated with microbial infections, food poisoning or water pollution. In amperometric integrated circuits for electrochemical sensors, flicker noise is still the main bottleneck to achieve ultrasensitive detection with small footprint, cost-effective and ultra-low power instrumentation. Current strategies rely on autozeroing or chopper stabilization causing negative impacts on chip size and power consumption. This work presents a 27-μW potentiostatic-amperometric Delta-Sigma modulator able to cancel its own flicker noise and provide a 4-fold improvement in the limit of detection. The 2.3-mm² all-in-one CMOS integrated circuit is glued to an inkjet-printed electrochemical sensor. Measurements show that the limit of detection is 15 pA_rms, the extended dynamic range reaches 110 dB and linearity is R² = 0.998. The disposable device is able to detect, in less than 1h, live bacterial concentrations as low as 10² CFU/mL from a 50-μL droplet sample, which is equivalent to 5 microorganisms.

Hospital fabrics and wound dressings with antibacterial properties are essential to minimize infection risks associated with bacterial colonization of textiles. A key challenge of these materials lies in the difficulty in assessing their functional lifespan. Integrating bacterial-sensing elements into smart textiles enables real-time and in-situ evaluation of antibacterial activity. However, this approach is often hindered by the reactivity between bactericidal and bacterial-sensing components, the limited stability and selectivity of the sensing probes, and high production costs. Here, we address these challenges by presenting a smart textile that simultaneously provides antibacterial activity and bacterial-sensing capacity using a layer-by-layer sonochemical deposition method. Prussian blue, a chromogenic bacterial-sensing probe, is integrated onto hospital-grade antibacterial fabrics containing copper oxide nanoparticles. When the biocidal fabric begins to lose its antimicrobial activity, live bacteria in the textile metabolically reduce Prussian blue nanoparticles, triggering a visible colour change. This approach offers several key advantages, such as: (i) the resulting textile retains antibacterial activity comparable to conventional copper oxide-based textiles (A value > 4 in both cases); (ii) it provides a direct and visible colour transition from blue to colourless (>20 % colour losses) when the antibacterial coating begins to lose effectiveness, enabling straightforward monitoring of antibacterial lifespan without external instruments or reagents; (iii) the co-immobilization enhances coating stability, nearly doubling the binding strength of copper oxide and Prussian blue compared to single-layer coatings; and (iv), the additional Prussian blue layer significantly reduces the material cytotoxicity, enhancing biocompatibility for safer use in healthcare settings. These innovations offer a scalable, cost-effective, and multifunctional solution for infection control. The smart textile not only prevents bacterial spread but also provides timely, visual indications of coating degradation, making it a promising tool for improving patient safety in hospitals and for minimizing infection risks in schools and other high-risk environments.