Multiplexed SERS Detection of Microcystins with Aptamer-Driven Core-Satellite Assemblies

Area of Science:

• Environmental Science
• Analytical Chemistry
• Nanotechnology

Background:

• Microcystins (MCs) are potent toxins produced by cyanobacteria, posing risks to aquatic ecosystems and human health.
• Accurate and sensitive detection methods for MCs are crucial for environmental monitoring and risk assessment.
• Existing detection methods may lack the sensitivity, selectivity, or multiplexing capabilities required for real-world applications.

Purpose of the Study:

• To develop and characterize novel surface-enhanced Raman spectroscopy (SERS) aptasensors for the indirect detection of microcystin-LR (MC-LR) and microcystin-RR (MC-RR).
• To achieve individual or simultaneous detection of MC-LR and MC-RR in natural water and algal culture samples.
• To enhance sensor sensitivity and reduce the limit of detection (LOD) compared to existing SERS-based methods.

Main Methods:

• Fabrication of core-satellite nanostructures using Au@label@Ag@Au nanoparticles immobilized on asymmetric Au nanoflowers (AuNFs).
• Functionalization of nanoparticles with MC-LR and/or MC-RR aptamers for specific analyte binding.
• Utilizing the dissociation of aptamer-functionalized nanoparticles upon MC binding to induce a decrease in SERS signal for indirect detection.
• Employing finite-difference time-domain (FDTD) simulations to analyze electromagnetic field enhancement.

Main Results:

• Achieved significantly low LODs: 0.8 pM for individual MC-LR detection and 1.5 pM for MC-LR / 1.3 pM for MC-RR in multiplex detection.
• Demonstrated excellent selectivity and high recovery rates (96-105%) for MC-LR and MC-RR.
• Successfully monitored MC-LR production in *M. aeruginosa* cultures over one week, validating real-world applicability.

Conclusions:

• The developed SERS aptasensors offer a highly sensitive and selective platform for detecting MC-LR and MC-RR in environmental samples.
• The core-satellite nanostructure design enhances SERS signal, leading to improved detection limits.
• These aptasensors show great promise for routine monitoring of microcystin contamination in aquatic environments.