Superparamagnetic iron oxide nanoparticles coating
Naked SPIONs are stable in high- and low-pH suspensions. However, their rapid aggregation tendency and high surface oxidation in the physiological environment (pH=7.4) restore its use. At neutral pH, SPIONs are very reactive (due to the huge surface area to volume ratio, high surface energy, and reactivity, with magnetic and long-range attractive van der Waals forces). Aggregation and oxidation decrease SPIONs magnetic performance, biocompatibility but increase toxicity. To overcome these drawbacks, SPIONs surface needs to be coated, which is usually performed with surfactants/capping agents/polymers. The coupling is performed via end functional groups (either by electrostatic interactions or covalent bonding) increasing the thickness of the new nanostructure. Moreover, it is also important to mention that the surface coating, depending on their nature, amount, composition, and thickness, may affect the inherent magnetic properties of SPIONs. For example, polyoxyethylene (5) nonylphenylether with –OH end group, oleic acid (with either inorganic or organic surfactants), and PEG and dextran polymers (with shorter chains) do not affect the SPIONs magnetization performance, although PEGs and dextrans with longer chains significantly decrease the coated particle magnetization values. Coating is the most commonly used method for SPIONs surface modification, allowing the conjugation of inorganic or organic materials on the surface. Besides preventing SPIONs surface oxidation and/or aggregation, the coating provides the possibility of functionalization, making them promising candidates for biomedicine applications. There are different vias for SPIONs’ coating: in situ coating, postsynthesis adsorption, and postsynthesis grafting. In in situ coating, as in the postsynthesis adsorption methods, occurs uniform encapsulation of SPIONs. In the postsynthesis grafting method, polymer end groups are coupled to SPIONs surface. Coating or grafting are processes used to make SPIONs more stable. However, it is important to highlight that when nonmagnetic materials are used as coating a decrease in saturation magnetization values may occur. If you are looking for high quality, high purity and cost-effective Iron oxide, or if you require the latest price of Iron oxide, please feel free to email contact mis-asia.