Low-Frequency Optical Signal Enhancement Device Combines CRISPR-Based Assay for Portable <i>S. Pneumoniae</i> Detection

Early detection and treatment of <i>Streptococcus pneumoniae</i> (SPN) is crucial for patients. However, since nucleic acid testing relies on large-scale equipment and specialized operators, challenges remain for accurate, fast, and low-cost SPN detection. Here, we present a point-of-care testing (POCT) device for rapid and accurate detection of SPN based on low-frequency optical signal enhancement and cluster of regularly interspaced short palindromic repeats (CRISPR). The spotlight tube enables the enhancement of the fluorescence signal, while the combination of an artificial intelligence-assisted autoexposure algorithm and a homomorphic filtering image processing method improves the signal-to-noise ratio of the fluorescence image, thus realizing highly sensitive detection. Nucleic acid identification is performed using CRISPR-based crRNAs, and fluorescent probes were constructed against the IytA gene of SPN. And they showed high specificity and sensitivity for the IytA gene. This device demonstrated excellent sensitivity in detecting the SPN using the developed CRISPR-based nucleic acid detection strategy. The detection threshold of SPN reached 0.1 fM, and the single detection time of the device was only 40 min. Specificity was validated using clinical samples, and the test showed 100% agreement with quantitative polymerase chain reaction results from clinical samples. This method provides a highly sensitive optical and signal processing device, which, in combination with a novel DNA probe for SPN, provides a novel indicator option for POCT of SPN.