Abstract
Iron oxide nanoparticles are the basic components of the most promising magnetoresponsive nanoparticle systems for medical (diagnosis and therapy) and bio-related applications. Multi-core iron oxide nanoparticles with a high magnetic moment and well-defined size, shape, and functional coating are designed to fulfill the specific requirements of various biomedical applications, such as contrast agents, heating mediators, drug targeting, or magnetic bioseparation. This review article summarizes recent results in manufacturing multi-core magnetic nanoparticle (MNP) systems emphasizing the synthesis procedures, starting from ferrofluids (with single-core MNPs) as primary materials in various assembly methods to obtain multi-core magnetic particles. The synthesis and functionalization will be followed by the results of advanced physicochemical, structural, and magnetic characterization of multi-core particles, as well as single- and multi-core particle size distribution, morphology, internal structure, agglomerate formation processes, and constant and variable field magnetic properties. The review provides a comprehensive insight into the controlled synthesis and advanced structural and magnetic characterization of multi-core magnetic composites envisaged for nanomedicine and biotechnology.
Highlights
The review provides a comprehensive insight into the controlled synthesis and advanced structural and magnetic characterization of multi-core magnetic composites envisaged for nanomedicine and biotechnology
It is essential to evidence that in contrast with agglomerates of single-core particles encountered in ferrofluids having weak colloidal stability, multi-core particles are the result of assembling a number of cores within a matrix
The evaporation-guided self-assembly of colloidal ferrofluids has been employed by several research groups for obtaining superparamagnetic anisotropic supraparticles of various shapes and with sizes ranging from several μm up to mm
Summary
Hybrid structures of colloidal nanoparticles designed for nanobiotechnology and nanomedicine [1,2,3,4,5,6,7,8], among them multifunctional magnetic nanoparticle–biomolecule–polymer hybrid systems with complex composition and topology [9,10,11,12], are receiving continuously increasing interest for medical diagnosis and treatment due to the newly acquired performances [13,14,15,16,17,18,19,20,21,22,23,24]. Among the remotely controlled endogenous (pH variation, enzymes etc.) or exogenous (e.g., light, temperature, electric field, magnetic field) stimuli-responsive nanoassemblies, designed to ensure dosage, spatial, and temporal controllability, the magnetic field driven bio-nanocomposites attracted tremendous scientific and technological interest [6,43,104] In this context of magnetism-based nanomedicine and biotechnology, we will focus mainly on the ferrofluid-based generation of multi-core magnetic nanocomposites, which are motivated by the relevance and maturity of magnetic fluids technology in providing large quantities of high-performance ferrofluids for various biomedical and engineering applications [105,106,107,108,109,110,111]. In addition to numerous assembly procedures for different shapes of multi-core magnetic particles with an application-specific design of composition and functionalization, the paper presents the results of advanced characterization methods (transmission electron microscopy, TEM; scanning electron microscopy, SEM; high-resolution electron microscopy, HRTEM; dynamic light scattering, DLS) and zeta potential, X-ray, and neutron scattering techniques (small-angle x-ray scattering, SAXS; small-angle neutron scattering, SANS; polarization analyzed SANS, PASANS; very small-angle neutron scattering, VSANS; neutron reflectometry, NR; and magnetometry) and discusses magnetic properties in a constant and variable magnetic field, as well as particle structure (size, polydispersity, stabilizing shell thickness, composition of particle core and shell), magnetic structure (magnetic size and composition), particle interaction (interparticle potential, magnetic moment correlation, phase separation), cluster and supraparticle formation (developed aggregation and chain/bundle formation)
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