Label-free sensing technology of two Staphylococcus species based on a terahertz metasurface.

Staphylococcus epidermidis (SE) and Staphylococcus aureus (SAU), comprising 50% of pathogenic bacteria in clinical blood isolates, demand precise detection for infection control. We present a label-free terahertz (THz) metasurface biosensor enabling simultaneous quantification and speciation of these Gram-positive pathogens. A tailored metasurface enhances THz wave-bacteria interaction through sharp resonance, creating quantitative correlations between resonance shifts and bacterial fluid dosage. Distinct linear regression slopes (SAU: 105.90 GHz/μL, SE: 45.14 GHz/μL) permit species differentiation, achieving specificity without biochemical labeling. This platform eliminates complex surface functionalization, reducing preparation time compared to ELISA-based methods while maintaining high sensitivity (theoretically 135.1 GHz/RIU, at a thickness of 3 μm, and experimentally 556 GHz/cell μm^-2 (SAU) and 237 GHz/cell μm^-2 (SE)). The technology's dual detection-differentiation capability, combined with its operational simplicity and cost-effectiveness, demonstrates transformative potential for clinical diagnostics and food safety monitoring, particularly in resource-limited settings requiring rapid pathogen screening.