Development and Functionalization of Magnetic Nanoparticles for Extraction of Circulating DNA (cfDNA): Platform for Liquid Biopsy ^†

Introduction: Liquid biopsy is an emerging and promising technique that enables the detection of molecular biomarkers in various body fluids, such as blood, urine, and saliva. Although conventional tissue biopsy remains the gold standard for tumor diagnosis, liquid biopsy offers several advantages, including its minimally invasive nature and its ability to provide valuable information for diagnosis, prognosis, treatment, and remission monitoring in oncology. The most commonly used marker in liquid biopsy is cell-free DNA (cfDNA), a small DNA fragment carrying information capable of detecting and characterizing cancer fingerprints. However, despite its potential, cfDNA analysis presents challenges. Its low concentration and susceptibility to contamination by genomic DNA (gDNA) require specialized extraction techniques. Nanotechnology emerges as a promising strategy to overcome these limitations. Magnetic iron oxide nanoparticles, such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃), were functionalized with a silica (SiO₂) coating to selectively interact with cfDNA fragments in biological samples. Thus, the main goal of this study was to synthesize magnetic nanoparticles with optimized size, surface area, and coating to extract and purify cfDNA from peripheral blood samples. Methodology: Magnetite and maghemite nanoparticles were synthesized via co-precipitation, functionalized with silica (SiO₂), characterized, and their performance was compared with commercial magnetic beads for cfDNA extraction. Results: cfDNA extraction from peripheral blood was achieved, revealing performance differences between magnetite and maghemite nanoparticles. Conclusions: Silica-coated iron oxide magnetic nanoparticles proved to be a promising tool, achieving comparable performance to commercial kits for cfDNA extraction and purification.