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

Abstract

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 (γ-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 γ-Fe2O3-PAA/poly(serine ester) and γ-Fe2O3-PAA/poly(serine ester)-b-PEG colloidal particles are studied by light scattering and microscopy. Colloidal stability in bio-fluids, hyperthermia under alternating magnetic field, cellular uptake, cytotoxicity and degradation of γ-Fe2O3-PAA/poly(serine ester)-b-PEG in living cells are investigated. Findings: A remarkably slow electrostatic complexation leads to dense superparamagnetic γ-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.