Aptamer-functionalized magnetic nanoparticles for electrochemical microbial sensing

Overview

This technology is a biosensing platform that uses aptamer-functionalized magnetic nanoparticles to capture and detect bacteria through a sandwich assay format. The nanoparticles target bacterial surface proteins, enabling the sensor to find the target rather than waiting for diffusion to a stationary sensor surface. An antibody-functionalized horseradish peroxidase (HRP) enzyme binds to the captured bacteria, and HRP catalyzes the oxidation of tetramethylbenzidine (TMB) to produce a colorimetric or electrochemical signal proportional to bacterial concentration. This approach is intended for affordable, user-friendly point-of-care diagnostic devices for microbial detection.

Technical specifications

Core mechanism:

• Aptamer-functionalized magnetic nanoparticles capture bacteria by binding to surface proteins
• HRP-antibody conjugates form a sandwich complex with captured bacteria
• Magnetic isolation concentrates the target before signal generation
• HRP catalyzes TMB oxidation, producing oxy-TMB detectable electrochemically or optically
• Signal intensity correlates with bacterial count

Key advantages:

• Reduced diffusional length because nanoparticles travel through solution to find targets
• Faster sensing time compared to conventional diffusion-limited biosensors
• Improved sensitivity through magnetic concentration of analytes
• Dual readout capability (electrochemical and optical)
• Facile aptamer functionalization techniques on magnetic nanoparticle surfaces

Development pipeline:

• Aptamer selection and screening for highest binding affinity (Kd value)
• Conjugation protocol optimization to magnetic nanoparticles
• Stability testing of aptamer-nanoparticle conjugates
• Binding condition optimization including buffer, salt concentration, and interaction time
• Electrochemical sensing optimization and real-sample analysis
• Sensitivity benchmarking and product cost assessment
• Affordable point-of-care diagnostic device development

Technology readiness level

The underlying aptamer-magnetic nanoparticle biosensing approach has been validated in the research group for detecting analytes such as prostate-specific antigen (PSA) and other proteins from blood samples. The bacterial detection application is at an earlier stage, with a structured five-month validation plan covering aptamer selection, conjugation optimization, binding condition refinement, electrochemical sensing development, and prototype point-of-care device construction. Current efforts focus on identifying the optimal aptamer, establishing robust conjugation protocols, and progressing toward real-sample analysis and cost evaluation.