We report the first in vitro enzymatic synthesis of paramagnetic and antiferromagnetic nanoparticles toward magnetic ELISA reporting. With our procedure, alkaline phosphatase catalyzes the dephosphorylation of L-ascorbic-2-phosphate, which then serves as a reducing agent for salts of iron, gadolinium, and holmium, forming magnetic precipitates of Fe45Â±14Gd5Â±2O50Â±15 and Fe42Â±4Ho6Â±4O52Â±5. The nanoparticles were found to be paramagnetic at 300 K and antiferromagnetic under 25 K. Although weakly magnetic at 300 K, the room-temperature magnetization of the nanoparticles found here is considerably greater than that of analogous chemically-synthesized LnxFeyOz (Ln = Gd, Ho) samples reported previously. At 5 K, the nanoparticles showed a significantly higher saturation magnetization of 45 and 30 emu/g for Fe45Â±14Gd5Â±2O50Â±15 and Fe42Â±4Ho6Â±4O52Â±5, respectively. Our approach of enzymatically synthesizing magnetic labels reduces the cost and avoids diffusional mass-transfer limitations associated with pre-synthesized magnetic reporter particles, while retaining the advantages of magnetic sensing.
Arati G. Kolhatkar, et. al., (2015) Enzymatic synthesis of magnetic nanoparticles.International Journal of Molecular Sciences16:47535. DOI: http://doi.org/10.3390/ijms16047535
International Journal of Molecular Sciences