Researchers have developed a hydrogel biosensor combining DNAzyme technology, bacteriophages, and machine learning to detect Escherichia coli (E. coli) in environmental and clinical samples with high sensitivity and specificity. Their report, published in Advanced Materials, introduces a colorimetric detection platform capable of identifying E. coli at concentrations as low as 10 colony-forming units per milliliter (CFU/mL) within 18 hours.
The biosensor uses a hydrogel matrix embedded with gold nanoparticles (AuNPs) and crosslinked by E. coli-specific DNAzymes. Upon exposure to E. coli-secreted proteins, the DNAzyme cleaves, dissolving the hydrogel and releasing AuNPs, producing a visible color change. Bacteriophage T7, an E. coli-targeting virus, amplifies the detection signal by lysing bacterial cells to release more DNAzyme-activating proteins. This approach enhanced sensitivity by several orders of magnitude compared with traditional methods.
Credit: Georgia Kirkos, McMaster University
The platform demonstrated consistent results across real-world applications. In lake and cistern water samples, the biosensor reliably detected E. coli at levels of 10–100 CFU/mL. Testing with urine samples from patients with urinary tract infections (UTIs) achieved 100 percent accuracy, with no false positives in control samples. The biosensor maintained stability under various storage conditions, including long-term freezing, making it viable for field deployment and clinical use.
To eliminate subjective interpretation of the colorimetric results, researchers integrated an artificial intelligence (AI) model. The convolutional neural network achieved 96 percent true positive and 100 percent true negative rates in classifying contaminated and uncontaminated samples from optical images. This automation simplifies the biosensor's use in resource-limited settings.
Corresponding author Tohid Didar said, “Now we have a tool that can be used in food samples, environmental samples and clinical samples. Today, people who suspect they may have a UTI must visit a doctor and sometimes wait days for a result. This technology would make it very easy for people to test themselves at home and get a result in a matter of hours.”
The biosensor's ability to detect low bacterial loads rapidly and affordably positions it as a promising tool for water quality monitoring and at-home UTI diagnosis. Researchers plan to extend the platform’s capabilities by targeting additional pathogens, further enhancing its versatility for environmental and clinical diagnostics.
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