MAGNETIC PARTICLE SPECTROSCOPY VIA AC BIOSUSCEPTOMETRY (ACB-MPS): NEW APPROACH FOR THE CHARACTERIZATION OF MAGNETIC NANOPARTICLES

Magnetic nanoparticles (MNPs) show promise in healthcare, but their In vivo detection still faces challenges such as high cost and lack of portability. Our group has been exploring AC Biosusceptometry as an alternative. This work aims to develop a ACB-MPS prototype for spectroscopic characterization of MNPs and future biomedical applications. The ACB-MPS prototype, an adaptation of the conventional ACB system, replaces the Lock-in amplifier with the Moku: PRO, utilizing its function generator and frequency analyzer capabilities. The system exploits the nonlinearity and harmonic generation of MNP magnetization to study their properties in the frequency domain. Fourier series analysis of magnetization reveals that, without an external DC field, only odd harmonics are observed, and their real coefficients can be determined. The real part of the nth harmonic of magnetization is expressed by a function of Fourier coefficients and Debye factors, resulting in high-amplitude odd harmonics. The Fourier transform of magnetization over time allows obtaining these harmonics, whose spectral amplitudes relate to intrinsic MNP properties, such as magnetic signal, functionalization, binding of biological targets, and concentration. We used citrate-coated manganese ferrite nanoparticles (Cit-MnFe₂O₄) and commercial Perimag nanoparticles. We obtained magnetic signal values for the odd harmonics of these MNPs, converting them into moment values and plotting them as a function of concentration to determine the system's sensitivity limit. The quantification of nanoparticle mass via ACB-MPS was validated by flame spectrometry. The implementation of the ACB-MPS prototype proved viable and promising for the spectroscopic characterization of MNPs. The technique detects odd harmonics generated by the nonlinear response of MNPs to an oscillating field, providing quantitative information on magnetic mass, surface functionalization, and interaction with the medium. Replacing the Lock-in with the Moku: PRO increased the system's versatility, paving the way for in vivo and preclinical applications. The results, validated by flame spectrometry, confirm the potential of ACB-MPS as a sensitivity alternative for MNP detection and characterization in various biomedical contexts.