Amorphous FeBP Magnetic Beads with l-Ascorbic Acid Modification for Efficient Sperm Separation in Forensic Analysis

Magnetic-activated cell sorting (MACS), utilizing the magnetism and specificity of antibody-conjugated magnetic beads, holds significant promise for forensic identification. However, current commercial magnetic beads face limitations in efficient separation due to their slow magnetic responsiveness and the influence of residual carbodiimide reagents used for surface activation. Herein, we report a core-shell magnetic bead with high-magnetic responsiveness and good suspension based on amorphous magnetic particles and l-ascorbic acid (ASA) surface modification. The particle size, coating thickness, and structure of the magnetic particles and coated magnetic beads were characterized by SEM, TEM, and XRD, respectively. The ζ-potential, FTIR spectroscopy, and XPS were selected as surface analysis methods. The magnetic properties of the magnetic beads were characterized by VSM, and the sperm separation performance was evaluated by obtaining Ct values through qPCR. These amorphous FeBP cores exhibit high saturation magnetization (surpassing conventional iron oxide particles by >40%), high susceptibility, and low coercivity, enabling both precise particle size control and enhanced magnetic responsiveness. Modification with ASA provides excellent biocompatibility and a mild chemical environment for the effective immobilization of the SPACA1 antibody based on the Schiff base structure, facilitating the specific separation of sperm using FeBP magnetic beads. ASA-modified FeBP beads achieved an 84% sperm cell capture rate, representing a 25.4% enhancement over commercial beads, and demonstrated a magnetic response speed approximately 3 times faster. Furthermore, ASA-modified beads exhibited excellent long-term stability, retaining 97% of the capture rate even after 60 days of storage. This work provides insights into the structural design and surface modification of high-magnetic-response and biocompatible magnetic beads and has positive significance for achieving efficient separation of different cells.