Manufacturing system for an electrochemical DNA biosensor based on gold-graphene quantum dots

Abstract

A system for the fabrication of an electrochemical DNA biosensor, comprising synthesis, electrode modification and probe immobilization modules to generate an AuNPs@GQDs based sensor surface.

Description

Field of invention

[0001] The invention relates to an electrochemical biosensor system with AuNP@GQD nanocomposites for the highly sensitive and specific DNA-based detection of Neisseria gonorrhoeae. Background of the invention

[0002] Neisseria gonorrhoeae is a significant sexually transmitted pathogen that poses a serious public health problem due to increasing antibiotic resistance and asymptomatic infections. Conventional diagnostic methods such as culture, microscopy, and nucleic acid amplification tests often require laboratory infrastructure, trained personnel, lengthy processing times, and expensive reagents. These limitations necessitate rapid, sensitive, and point-of-care diagnostic methods. Electrochemical biosensors offer advantages such as high sensitivity, fast response time, portability, and low sample size. Nanomaterials such as gold nanoparticles (AuNPs) and graphene quantum dots (GQDs) significantly improve transduction efficiency by increasing the electron transfer rate and providing a large surface area for probe immobilization.However, the fabrication of a stable, reproducible, and highly conductive nanocomposite interface requires precise control of the synthesis, assembly, and probe attachment steps. Therefore, there is a need for a system that integrates the synthesis of the AuNPs@GQDs nanocomposite with electrode modification and DNA probe immobilization to enable reliable electrochemical detection of Neisseria gonorrhoeae. Summary of the invention

[0003] The invention provides a system for the fabrication of an electrochemical DNA biosensor based on a gold nanoparticle-graphene quantum dot nanocomposite (AuNPs@GQDs) for the detection of Neisseria gonorrhoeae. The system comprises modules for the synthesis of the AuNPs@GQDs hybrid nanomaterial, for modifying an electrode surface, and for immobilizing a DNA probe specific to the pathogen's genetic sequence. The nanocomposite enhances electrical conductivity, electron transfer, and surface loading capacity, thus forming a highly reactive sensor platform. The controlled synthesis ensures uniform nanoparticle deposition and the stable integration of gold nanoparticles (AuNPs) into graphene quantum dots (GQDs) to form an efficient conductive matrix.

[0004] The detection module utilizes hybridization between immobilized probe DNA and the genetic target material of Neisseria gonorrhoeae, resulting in measurable electrochemical changes. These reactions can be monitored using techniques such as differential pulse voltammetry or impedance analysis. The system thus enables rapid, sensitive, and selective detection. The modular manufacturing process ensures reproducibility, stability of the biosensor interface, and suitability for mobile diagnostic applications. Detailed description

[0005] The system comprises a nanocomposite synthesis unit in which gold nanoparticles are combined with graphene quantum dots (GQDs) under controlled reaction conditions to form an AuNPs@GQDs hybrid. This process ensures uniform anchoring of the gold nanoparticles to the GQD surface, thereby increasing conductivity and surface area. Synthesis parameters such as precursor concentration, pH, temperature, and reaction time are adjusted to achieve optimal nanocomposite morphology and stability.

[0006] Following synthesis, the system includes an electrode modification unit. A conductive electrode surface, typically carbon-based or metallic, is purified, activated, and coated with the AuNPs@GQDs dispersion. Controlled deposition ensures uniform coating, strong adhesion of the nanocomposite, and improved electron transfer pathways at the electrode surface.

[0007] The modified electrode is then transferred to the DNA probe immobilization module. Specific single-stranded DNA sequences complementary to genetic markers of Neisseria gonorrhoeae are immobilized on the AuNPs@GQDs-coated electrode via thiol-gold bonds or other affinity interactions. The nanocomposite structure, with its numerous functional surface sites, enables high probe loading.

[0008] After immobilization, the system undergoes a stabilization step in which unbound DNA and contaminants are removed to ensure a clean and stable sensor surface. The biosensor surface is then conditioned to minimize non-specific interactions and increase selectivity.

[0009] For detection, target DNA extracted from clinical or environmental samples is introduced into the system. Upon hybridization with the immobilized probe, the electrochemical properties of the biosensor surface change, generating measurable electrical signals. These signals can include changes in impedance, current, or peak potential.

[0010] The system includes an electrochemical measurement module that enables voltammetric, amperometric, or impedance-based analyses. These methods detect hybridization-related changes with high sensitivity, thus allowing for the early and borderline detection of Neisseria gonorrhoeae.

[0011] To ensure reliability, the system includes calibration and control steps that validate the sensor response using known concentrations of complementary and non-complementary DNA sequences. The biosensor can be regenerated or reused by denaturing the hybridized DNA under controlled conditions.

[0012] The integrated manufacturing and measurement process ensures reproducibility, fast response times, portability and user-friendly operation, making the biosensor suitable for patient-centered applications and field diagnostics.

Claims

[1] A system for the fabrication of an electrochemical DNA biosensor, comprising synthesis, electrode modification and probe immobilization modules for the production of an AuNPs@GQDs based sensor surface. [2] System according to claim 1, wherein the AuNPs@GQDs nanocomposite improves electron transfer, increases the surface area and enables the attachment of DNA probes at high density. [3] System according to claim 1, wherein the hybridization between immobilized probe DNA and target DNA of Neisseria gonorrhoeae generates measurable electrochemical signals for detection. [4] A biosensor manufactured using the system according to claim 1, which enables rapid, sensitive and selective electrochemical detection of Neisseria gonorrhoeae.