Surface acoustic wave sensor for endotoxin detection in fluid media

Overview

This solution offers a compact, portable sensing platform for detecting endotoxins in fluid media using surface acoustic wave (SAW) technology. Endotoxins, which are toxic components of bacterial cell walls, pose significant risks in pharmaceutical manufacturing, medical device sterilization, water quality monitoring, and clinical diagnostics. Current detection methods often require laboratory infrastructure, are time-consuming, or lack the sensitivity needed for early warning.

The proposed sensor leverages Love wave SAW devices fabricated on piezoelectric substrates such as ST quartz and lithium tantalate, coated with an oxide guiding layer. By functionalizing the sensor surface with aptamers—synthetic nucleotide sequences that bind specifically to target molecules—the platform achieves selective recognition of endotoxins. The approach targets detection limits in the ng/ml range, with potential to reach pg/ml sensitivity, enabling rapid, on-site testing without the need for centralized laboratory analysis.

Technical specifications

Key features:

• Dual delay-line SAW architecture on ST quartz or LiTaO3 substrates with oxide guiding layers for Love wave propagation
• Aptamer-based recognition layers immobilized on the sensor surface for selective endotoxin binding
• Microfluidic test cell integration for controlled sample delivery and handling
• Custom portable electronics adapted from validated prototype designs for signal processing and readout
• Non-specific binding removal mechanism that improves selectivity by clearing unbound material from the sensor surface
• Sensitivity enhancement through operation at higher frequencies (~300–400 MHz versus current ~100 MHz) and optimized oxide layer design guided by finite element modeling

How it works: Acoustic waves propagate along the piezoelectric substrate surface. When target endotoxins bind to the aptamer layer, they alter the wave's velocity and amplitude, producing a measurable signal correlated with analyte concentration.

Technology readiness level

The underlying SAW sensor technology has been validated through published research demonstrating pg/ml detection limits for cancer biomarkers such as carcinoembryonic antigen in both prepared laboratory samples and human plasma. Prototype electronics have been constructed and characterized. The current effort extends this validated platform to endotoxin detection, requiring aptamer functionalization, microfluidic integration, and frequency optimization. Bench-top validation of endotoxin detection is the next milestone, followed by adaptation of portable electronics into a point-of-need sensor system. The technology readiness level is estimated at TRL 4–5, with laboratory validation of components completed and system-level integration underway.