Auto-degradable and biocompatible superparamagnetic iron oxide nanoparticles/polypeptides colloidal polyion complexes with high density of magnetic material

Hypothesis: Superparamagnetic iron oxide nanoparticles (SPIONs) are extensively used as building block of colloidal nanocomposites for biomedical applications. Strategies employed to embed them in a biodegradable and biocompatible polymer matrix often fail to achieve a high density of loading which would greatly benefit to applications such as imaging and hyperthermia. In this study, poly(acrylic acid) coated SPION (gamma-Fe2O3-PAA) are self-assembled with hydrolysable poly(serine ester) by electrostatic complexation, leading to perfectly defined spherical particles with ultra-high density of magnetic material and an ability to auto-degrade into individual SPION and biocompatible byproducts. Experiments: Self-assembly and auto-degradation of gamma-Fe(2)O(3)PAA/poly(serine ester) and gamma-Fe2O3-PAA/poly (serine ester)-b-PEG colloidal particles are studied by light scattering and microscopy. Colloidal stability in biofluids, hyperthermia under alternating magnetic field, cellular uptake, cytotoxicity and degradation of gamma-Fe2O3-PAA/poly(serine ester)-b-PEG in living cells are investigated. Findings: A remarkably slow electrostatic complexation leads to dense superparamagnetic gamma-Fe2O3-PAA/poly (serine ester)-b-PEG polyion complexes (PICs) with controlled sizes (150-500 nm) and times of degradation in aqueous solvents (700-5000 h). The material shows good sustainability during hyperthermia, is well taken up by MC3T3 cells and non-cytotoxic. TEM images reveal a mechanism of degradation by "peeling" and fragmentation. In cells, PICs are reduced into individual SPIONs within 72 h.