Use of Laser-Induced Graphene and Functionalized Magnetite Particles as Anchors in Electrochemical CA 15-3 Detection Devices

Iron oxide particles have been used in in vitro diagnostics and theragnosis for nearly 40 years. Magnetite nanoparticles (MNPs) have become popular as supports for immobilizing biomacromolecules due to their magnetic properties, low toxicity, chemically modifiable surface, and high biomolecule loading capacity which promote constant ionic interaction. Coating magnetic nanoparticles with functional materials, such as silicon oxide (SiO₂), has been shown to improve their stability and enable the addition of various functional groups to their surface without altering their properties. The SiO₂ layer provides a chemically inert surface for the core nanomaterials in biological systems.<br/>An ISFET, or Ion-Sensitive Field-Effect Transistor, is a type of field-effect transistor that measures ion concentration in a solution. It can be used as an immunobiosensor when combined with techniques like antibody or antigen immobilization to detect specific biomolecules such as proteins or antigens.<br/>The concentration of target biomolecules in a sample is recorded by measuring the variation of the electrical potential at the gate of the ISFET. The changes in potential are analyzed to establish a correlation between the potential change and the presence and concentration of specific biomolecules. The CA 15-3 cancer-associated antigen has been found in the serum of over 70% of patients with advanced breast carcinoma and in a small percentage of patients with non-breast malignancies. Detecting circulating levels of the CA 15-3 antigen may aid in distinguishing breast carcinoma from other dysplasias.<br/>The upper limit of normal (ULN) for circulating CA 15-3 was set at 40 U/mL, as this threshold most adequately distinguished healthy subjects and patients with metastatic breast cancer. The levels of the antigen CA 15-3 in the serum of 500 patients with non-breast cancer, whose age ranged from 2 to 84 years were studied.<br/>Among metallic particles, functional sable core-shell nanoparticles are promising candidates for electrochemical sensors as they can immobilize various materials of biological significance with proper chemical groups. Even if they show magnetic properties, they enable effective separation through external magnetic field induction. Magnetite, Fe₃O₄, is a prevalent iron oxide that can be converted into particles. They can be dispersed in proper solvents and have the potential to create atomic layers for example oxide surfaces (e.g., silicon or aluminum) with a suitable contact area, which can subsequently be functionalized by joining various bioactive molecules that hold high potential for use in various in vitro and in vivo applications. It is crucial to keep control over the synthesis conditions and surface functionalization of particles to achieve particles with specific dimensions, colloidal stability, and biological properties. Typically, the immobilization of peptides or proteins onto particle surfaces are conducted through the activation of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide-N-hydroxysuccinimide hydrochloride (EDC-NHS).<br/>This work proposes immobilizing the CA 15-3 ELISA kit antibody using functionalized nanoparticles with a magnetite core and silicon oxide shell (F-NPs) with amine groups that diffuse through an immobilization platform (PI) of LIG. Stable groups are created on the functionalized particles to immobilize proteins. A reactive surface is generated by inserting various concentrations of glucose, which gives rise to an immune neutralization reaction (antigen-antibody) producing ionized species. These species are detected through an ISFET that was built on a flexible substrate and subjected to electrical potentials whose are measured between the drain, source, and gate contacts characterizing them by IV saturation curves. This process obtains a proportional relationship between the decay of the current on the device and the added glucose concentration.