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Facile aqueous, room temperature preparation of high transverse relaxivity clustered iron oxide nanoparticles

Hobson, Nicholas J., Weng, Xian, Ashford, Marianne, Thanh, Nguyen T.K., Schätzlein, Andreas G., Uchegbu, Ijeoma F.
Colloids and surfaces 2019 v.570 pp. 165-171
X-ray diffraction, ambient temperature, chitosan, coatings, image analysis, magnetic resonance imaging, magnetism, molecular weight, nanoparticles, pH, particle size, polymers, solvents, sonication, surfactants, zeta potential
Clustering superparamagnetic iron oxide nanoparticles (SPIONs) is one method of providing the biomedical benefits of larger SPIONs [e.g. superior T2 weighted magnetic resonance imaging (MRI) contrast] without increasing particle size. The work presented herein, describes the facile synthesis of clustered SPIONs that are suitable for MRI applications, by using a chitosan based polymer: N-palmitoyl-N-monomethyl-N-N-dimethyl-N-N-N-trimethyl-6-O-glycolchitosan (GCPQ) and aqueous nanoprecipitation followed by probe sonication, in the absence of organic solvents or elevated temperatures. The resulting clustered SPIONs consist of individual 8 nm iron oxide nanoparticles clustered into a 150 nm particle with a positive zeta potential (+23 mV) at neutral pH. X-ray diffraction confirms the presence of crystalline magnetic iron oxide, while magnetometer experiments show the clustered SPIONs are superparamagnetic giving an overall Ms of 63.5 ± 1.3 emu g−1. Relaxometry analyses revealed that the clustered SPIONs (inclusive of coatings) had a high r2 value of 294.8 mM−1 s−1 and an r2/r1 of 21.1 making the clustered SPIONs suitable for T2 weighted (negative) MRI contrast imaging applications. The resulting clustered SPIONs demonstrate that highly sensitive T2 contrast agents may be produced in mild room temperature conditions, without the need for organic solvents or low molecular weight surfactants.