A NOVEL HYBRID MAGNETIC SYSTEM FOR AC SUSCEPTIBILITY USING ALTERNATING CURRENT BIOSUSCEPTOMETRY (ACB)

Magnetic nanoparticles (MNPs) are widely studied for applications in diagnostics, therapy, and biomedical imaging. However, accurate characterization of these particles remains a challenge, especially due to structural differences between single-core and multi-core MNPs. Techniques such as TEM, DLS, and magnetic methods (MRX, VSM, ACS, MPS) are used to estimate properties like magnetic moment and hydrodynamic size. Yet, these approaches often require complex models, account for magnetic interactions, and may be expensive or unsuitable for animal experimentation. Our group has been investigating Alternating Current Biosusceptometry (ACB) as an accessible and portable alternative. We propose a prototype based on ACB to estimate the hydrodynamic size of MNPs through the analysis of AC Susceptibility (ACS). The system measures the real χ'and imaginary χ''components of susceptibility at various frequencies, using low-amplitude fields to avoid magnetization saturation. The χ'' peak is sensitive to hydrodynamic volume, medium viscosity, and temperature, enabling the characterization of MNPs and analysis of their mobility in different environments. The superposition of relaxation models allows the separation of distinct MNP populations, expanding the potential of the technique for biomedical applications. We developed a hybrid system, called ACS-ACB, which combines conventional AC magnetometry with advanced phase analysis. Python algorithms were implemented for automated analysis of spectroscopic data. For validation, we used citrate-coated manganese ferrite MNPs and compared the results with commercial systems such as the DynoMag AC susceptometer and DLS. ACS-ACB revealed an average diameter of 34.9 nm, close to values obtained with DynoMag (44.5 nm) and DLS (29 nm). The differences reflect the specificities of each technique but confirm the reliability of ACS-ACB. With low cost, portability, and high sensitivity, ACS-ACB stands out as a promising tool for magnetic characterization of MNPs in solutions, making it especially useful in biomedical research and the development of therapeutic applications.