MP13 - Impedimetric Detection of COVID Proteins on Functionalized Boron Doped Diamond Electrodes – is the Redox Marker Necessary?

At a Glance

Metadata	Details
Publication Date	2025-01-01
Authors	Anna Olejnik, Robert Bogdanowicz
Analysis	Full AI Review Included

Executive Summary

This technical analysis focuses on the successful development of a high-performance COVID-19 biosensor utilizing Boron Doped Diamond (BDD) electrodes and Electrochemical Impedance Spectroscopy (EIS).

Core Achievement: Quantitative detection of COVID-19 Receptor Binding Domain (RBD) protein was achieved using BDD electrodes functionalized with ACE2 receptors.
Methodological Breakthrough: The study validated a novel, marker-free detection strategy, eliminating the need for external redox couples (e.g., hexaferrocyanide).
Superior Sensitivity: The non-marker approach demonstrated significantly enhanced performance, achieving a Limit of Detection (LOD) of 6 pg/L, which is 8.3 times lower than the standard redox-marker protocol (50 pg/L).
Enhanced Stability: The marker-free method resulted in improved electrode stability and repeatability, mitigating issues associated with redox marker interaction with the receptor or target protein.
Material Validation: The research confirms BDD’s exceptional suitability as a robust, chemically inert, and highly sensitive platform for advanced electrochemical biosensing applications.
Linear Range: Both detection methods maintained a wide linear response range spanning from 0.05 µg/L to 1 mg/L.

Technical Specifications

The following data points summarize the key performance metrics achieved in the detection of COVID-19 RBD protein using BDD electrodes.

Parameter	Value	Unit	Context
Material Platform	Boron Doped Diamond (BDD)	N/A	Prepared via MPCVD
Target Analyte	COVID-19 RBD Protein	N/A	Functionalized with ACE2 Receptors
Detection Method	Electrochemical Impedance Spectroscopy (EIS)	N/A	Measured at 1 Hz (Imaginary Impedance, Z”)
LOD (Non-Marker Protocol)	6	pg/L	Superior performance without external redox couple
LOD (Standard Marker Protocol)	50	pg/L	Using 1 mM hexaferrocyanide (II/III)
Sensitivity Slope (Non-Marker)	1	kΩ/dec	Imaginary impedance vs. concentration
Sensitivity Slope (Standard Marker)	300	Ω/dec	Imaginary impedance vs. concentration
Linear Detection Range	0.05 to 1	µg/L	Applicable for both marker and non-marker methods
Electrolyte Solution	1X Tris buffered saline	N/A	pH = 7.2
Redox Marker Concentration	1	mM	Hexaferrocyanide (II/III)

Key Methodologies

The experimental procedure relied on advanced material preparation and precise electrochemical measurement techniques:

BDD Preparation: Boron Doped Diamond electrodes were synthesized using a Microwave-Assisted Chemical Vapor Deposition (MPCVD) process.
Functionalization: The BDD surfaces were functionalized with Angiotensin Convertase Enzyme (ACE2) receptors, which specifically target the COVID-19 RBD protein.
Confirmation: Successful formation of the nanostructured BDD and subsequent biomolecule functionalization were confirmed via established methods [2].
Electrochemical Measurement: Detection was performed using Electrochemical Impedance Spectroscopy (EIS) in a neutral aqueous solution (1X Tris buffered saline, pH 7.2).
Protocol Comparison: Two measurement protocols were compared:
- Standard Protocol: Included 1 mM external hexaferrocyanide (II/III) redox couple.
- Marker-Free Protocol: Conducted without the external redox couple.
Signal Analysis: The detection signal was simplified to the imaginary part of the impedance (Z”) measured specifically at 1 Hz frequency.
LOD Calculation: Limit of Detection (LOD) was calculated according to the standard approach advised in [3]: LOD = 3.3 SD / a.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality BDD materials and customization services required to replicate, scale, and advance this biosensor research. Our MPCVD capabilities ensure the tight material control necessary for high-performance electrochemical applications, especially those relying on subtle impedance changes in marker-free detection.

Applicable Materials

To achieve the high conductivity and chemical inertness required for stable, marker-free electrochemical detection, the following 6CCVD materials are recommended:

Heavy Boron Doped PCD (Polycrystalline Diamond): Ideal for large-area biosensor arrays (up to 125mm) requiring high conductivity, low background noise, and cost-effective scaling.
Heavy Boron Doped SCD (Single Crystal Diamond): Recommended for high-precision, small-area sensors where ultra-low defect density and maximum charge transfer efficiency are paramount.
Custom Thickness BDD: We offer BDD layers ranging from 0.1µm to 500µm, allowing researchers to optimize film thickness for specific electrochemical properties and device integration.

Customization Potential

The development of advanced biosensors often requires specialized geometries and integration features. 6CCVD provides comprehensive customization services:

Research Requirement	6CCVD Customization Service
Specific Electrode Dimensions	Custom Dimensions & Laser Cutting: We provide plates/wafers up to 125mm (PCD) and offer precision laser cutting to create complex electrode patterns, micro-arrays, or specific geometries for microfluidic integration.
Surface Finish	Ultra-Smooth Polishing: We achieve surface roughness of Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD), ensuring the ideal smooth platform necessary for reliable receptor (ACE2) functionalization and minimizing non-specific binding.
Device Integration	Custom Metalization: We offer in-house deposition of standard contact metals (Au, Pt, Pd, Ti, W, Cu) to facilitate robust electrical connection and integration into sensor platforms.
Substrate Support	Custom Substrates: We supply substrates up to 10mm thick, providing the mechanical stability required for robust device packaging and handling.

Engineering Support

The successful transition to a marker-free protocol relies heavily on the quality and consistency of the BDD material. 6CCVD’s in-house PhD team specializes in optimizing diamond growth parameters (boron concentration, surface termination, film morphology) to maximize electrochemical performance.

We can assist with material selection for similar Electrochemical Biosensing projects, ensuring the BDD film exhibits the optimal conductivity and surface characteristics needed to achieve high sensitivity (Slope: 1 kΩ/dec) and superior stability, replicating the benefits of the non-marker approach.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.5162/eurosensors2025/mp13