Title : Biocompatible synthesis of non crystalline iron oxide nanoparticles with stable colloidal properties
Abstract:
Biocompatible iron oxide nanoparticles (IONPs) are widely used in targeted and responsive delivery, yet conventional formulations adopt crystalline spinel phases that generate magnetic interactions and aggregation, constraining spaciousness and colloidal stability. To overcome these limitations, we intentionally disrupted spinel lattice formation under biocompatible, aqueous, single-pot synthesis conditions. This approach yielded a gold-colored, non-aggregated iron oxide: magnesium (9:1) nanoparticle suspension with a hydrodynamic diameter of ~45 nm, a Zeta potential of ~–25 mV, and PDI < 0.3. A 62 mg batch produced ~2×10¹³ functionalized, zwitterionic particles that remained stable through freeze–thaw cycling.
In-process controls revealed that under oxygen-limited conditions, reduced magnesium and low-MW dextran co-incorporate during particle formation rather than acting as dopants or surface coatings. Multidentate iron-coordination ligands governed colloidal integrity, while optical characterization showed time-dependent spectral evolution differ with crystalline spinel signatures, indicating emergence of a locked, non-crystalline colloidal state at 140 minutes.
These findings demonstrate that colloidal nanoparticle is not required for IONP stabilization under automatable synthesis constraints and define boundary conditions in which coordination alone is insufficient; persistence of the particulate state arises only when dynamic exchange, spatial organization, and multifunctional coupling are simultaneously imposed. Limiting Fe³+ availability during synthesis generates a second, distinct, and reproducible nanoparticle population. These two classes (Type I and Type II) exhibit differentiated physicochemical properties consistent with single particles possessing different composite dimensions and component ratios.
The biological evaluation is structured to leverage these mechanistic distinctions: Type I nanoparticles are applied to HEK293 cells prior to cryopreservation, whereas Type II nanoparticles are used to recover cells post-thaw. In parallel, rabbit splenocytes from male and female donors are assessed ex vivo to establish sex-dependent baselines in nanoparticle viability effects. This design reflects growing evidence that biological sex significantly shapes cancer treatment outcomes—modulating therapeutic efficacy, toxicity, and immune function, including non-small cell lung cancer (NSCLC); NK-cell activity such as fetal microchimerism—suggesting persistent, system-level divergence between males and females.
