Fast synthesis of biocompatible iron oxide nanoparticles via a microwave-assisted Schikorr reaction: Phase-director influence of iron glycinate complexes

In this study, we present a rapid method for synthesizing iron oxide nanoparticles using a microwave-assisted Schikorr reaction. We propose the use of glycine to inhibit the formation of parasitic phases even from the initial mixture of reagents. In addition to forming the nanoparticles, the method allows for the preparation of their surface for subsequent bioconjugation using a combined glucose-fructose and glycine coating at moderately low temperatures. We demonstrate that the fast formation of iron glycinates prevents the appearance of unintended compounds, which is particularly useful for controlling the Schikorr reaction and avoiding premature reactions during precursor mixing. Glycine also acts as a surfactant, limiting the growth of unwanted clusters and expanding the bioconjugation capabilities of the nanoparticles, favoring their application in theranostics. Finally, cell viability tests at different nanoparticle concentrations do not reveal significant cytotoxicity, strengthening the evidence for biocompatibility. • Rapid microwave-assisted Schikorr reaction enables Fe₃O₄ nanoparticle synthesis in just 10 minutes • Iron glycinate complexes direct phase-pure magnetite formation, suppressing unwanted iron hydroxides • Dual glycine–glucose-fructose coating enhances biocompatibility and biofunctionalization potential • Mild, scalable process supports translational applications and compatibility with industrial production standards