Colorimetric endotoxin detection using gold nanoparticles in glow stick format

Overview

This solution offers a rapid, equipment-free method for detecting endotoxin using a self-contained plastic stick that works like a glow stick. Endotoxin, a toxic component of bacterial cell walls, is a critical contaminant that must be monitored in pharmaceutical manufacturing, medical devices, and clinical diagnostics. Current detection methods often require laboratory instrumentation, trained personnel, and hours of processing time.

The proposed test uses gold nanoparticles (AuNPs) coated with lipopolysaccharide-specific peptides. When a sample containing endotoxin is introduced, the nanoparticles aggregate and shift in colour from red to purple. An internal enhancer solution, released by snapping a glass capillary inside the stick, amplifies the colour signal for clear naked-eye interpretation. This combination of peptide-driven specificity and signal enhancement aims to deliver sensitivity well below conventional AuNP-based colour tests.

Technical specifications

Key features:

• AuNPs conjugated to high-affinity lipopolysaccharide-specific peptides for targeted endotoxin recognition
• Aggregation-based colour shift from red (negative) to purple (positive) within minutes
• Self-contained plastic stick with sealed glass capillary holding an enhancer solution
• Glow stick-style activation: bending the stick releases the enhancer to amplify the colour signal
• Designed for naked-eye read-out, eliminating the need for spectrophotometers or other instruments
• Initial development in 96-well plate format to optimise peptide conjugation, enhancer chemistry, and incubation times before prototyping the stick format

How it works:

The peptides bound to the AuNPs recognise and bind endotoxin molecules, causing the nanoparticles to cluster together. This aggregation changes how the nanoparticles interact with light, producing a visible shift from red to purple. The enhancer solution released from the broken capillary promotes further growth of both aggregated and unaggregated nanoparticles, intensifying the colour difference and making the result obvious without magnification or measurement devices.

Technology readiness level

The technology is at an early-to-mid stage of development. The underlying AuNP colour-shift principle and peptide-based biosensor affinity have been demonstrated separately in prior published work, but they have not yet been combined in this specific glow stick configuration. Planned next steps include functionalising AuNPs with LPS-specific peptides, optimising aggregation conditions and enhancer chemistry, building 96-well plate prototypes, and then fabricating physical glow stick prototypes using plastic tubing and glass capillaries. Sensitivity, specificity, and cross-reactivity with serum proteins, polysaccharides, buffers, and culture media will be characterised during validation.