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Electrochemical Aptamer-Based Biosensors for Cocaine Detection in Human Saliva: Exploring Matrix Interference
Yasmin Liu1, Rishi Pandey1, Mary Jane McCarthy1
1Forensic Research & Development Department, Institute of Environmental Science and Research, PO Box 50348, Porirua 5240, New Zealand.
Analytical Chemistry
|January 8, 2025
Summary
This study developed a disposable electrochemical aptasensor for detecting cocaine in saliva. A high salt concentration strategy significantly improved sensitivity, enabling rapid cocaine detection in complex biofluids.
Area of Science:
- Electrochemistry
- Biosensor Technology
- Analytical Chemistry
Background:
- Electrochemical aptamer-based biosensors (E-aptasensors) offer point-of-care detection in biofluids like saliva.
- Saliva is a convenient matrix for detecting illicit drugs such as cocaine.
- Current cocaine E-aptasensors face sensitivity challenges in complex saliva matrices.
Purpose of the Study:
- Investigate salivary component effects on cocaine E-aptasensor performance.
- Develop and optimize a disposable E-aptasensor for cocaine detection in saliva.
- Enhance cocaine detection sensitivity and reliability in human saliva.
Main Methods:
- Utilized square-wave voltammetry (SWV) to assess aptasensor performance.
- Fabricated disposable electrodes using laser ablation.
- Employed cyclic voltammetry (CV), scanning electron microscopy (SEM), and atomic force microscopy (AFM) for surface characterization.
- Optimized aptamer immobilization with 6-mercapto-1-hexanol (MCH) co-immobilization.
- Investigated the impact of ionic strength, pH, and salivary components.
Main Results:
- Optimal aptasensor performance in buffer achieved at low ionic strength, neutral pH, and absence of multivalent ions.
- Salivary viscosity and mucin showed minimal impact, but proteins significantly affected sensing.
- High NaCl concentration effectively mitigated the negative impact of salivary proteins.
- Developed a "mix-and-detect" method for cocaine detection in 90% saliva.
- Achieved a limit of detection (LOD) of 3.7 μM for cocaine in saliva.
Conclusions:
- Salivary proteins are a key challenge for cocaine E-aptasensor sensitivity.
- High NaCl concentration is a viable strategy to enhance aptasensor performance in saliva.
- The developed disposable aptasensor shows promise for rapid, sensitive cocaine detection in saliva.
- This method simplifies cocaine detection in complex biofluids, particularly for smoked administration.
