Dual-mode colorimetric-fluorescence biosensor for endotoxin detection based on CS@Fe,Cu/CDs-MnO₂ nanomaterials

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Nanotechnology

Background:

• Endotoxins from gram-negative bacteria cause severe health issues like endotoxemia and organ failure.
• Traditional endotoxin detection methods, such as Limulus reagent, are costly and limited in speed and accuracy.
• There is a need for advanced, rapid, and sensitive biosensors for endotoxin detection.

Purpose of the Study:

• To develop a dual-mode (fluorometric and colorimetric) biosensor for sensitive and rapid endotoxin detection.
• To utilize chitosan-grafted Fe,Cu-doped carbon dots (CS@Fe,Cu/CDs) as an artificial nanozyme for enhanced sensing.
• To provide a smartphone-compatible platform for accessible endotoxin analysis.

Main Methods:

• Fabrication of CS@Fe,Cu/CDs-MnO2 nanozyme with high catalytic activity and fluorescence.
• Utilized the nanozyme's peroxidase-like activity to oxidize DAB for colorimetric detection.
• Exploited electrostatic interactions between the positively charged nanozyme and negatively charged endotoxin to modulate catalytic activity and fluorescence quenching for dual-mode detection.

Main Results:

• The colorimetric method showed a linear response for endotoxin in the range of 0.125-175 EU/L with a LOD of 0.058 EU/L.
• The fluorometric method detected endotoxin linearly from 0.05-90 EU/L with a LOD of 0.036 EU/L.
• The biosensor achieved high accuracy (89.0–101.3% recovery) and precision (RSD ≤ 4.51%) in real injection samples.

Conclusions:

• The developed CS@Fe,Cu/CDs-MnO2 based dual-mode biosensor offers a sensitive, rapid, and reliable method for endotoxin detection.
• This smartphone-assisted approach provides a cost-effective and accessible alternative to conventional endotoxin assays.
• The biosensor demonstrates significant potential for clinical diagnostics and quality control applications.