Improved Magneto-Microfluidic Separation of Nanoparticles through Formation of the β-Cyclodextrin-Curcumin Inclusion Complex

Molecular adsorption to the nanoparticle surface may switch the colloidal interactions from repulsive to attractive and promote nanoparticle agglomeration. If the nanoparticles are magnetic, then their agglomerates exhibit a much stronger response to external magnetic fields than individual nanoparticles. Coupling between adsorption, agglomeration, and magnetism allows a synergy between the high specific area of nanoparticles (similar to 100 m(2)/g) and their easy guidance or separation by magnetic fields. This yet poorly explored concept is believed to overcome severe restrictions for several biomedical applications of magnetic nanoparticles related to their poor magnetic remote control. In this paper, we test this concept using curcumin (CUR) binding (adsorption) to beta-cyclodextrin (beta CD)-coated iron oxide nanoparticles (IONP). CUR adsorption is governed by host-guest hydrophobic interactions with beta CD through the formation of 1:1 and, possibly, 2:1 beta CD:CUR inclusion complexes on the IONP surface. A 2:1 stoichiometry is supposed to promote IONP primary agglomeration, facilitating the formation of the secondary needle-like agglomerates under external magnetic fields and their magneto-microfluidic separation. The efficiency of these field-induced processes increases with CUR concentration and beta CD surface density, while their relatively short timescale (<5 min) is compatible with magnetic drug delivery application.

Automated summary

Molecular adsorption on the surface of nanoparticles can promote nanoparticle agglomeration and enhance their response to external magnetic fields, especially in the case of magnetic nanoparticles. The synergy between adsorption, agglomeration, and magnetism allows for high specific area nanoparticles to be easily guided or separated by magnetic fields, overcoming limitations in biomedical applications. By utilizing curcumin binding to beta-cyclodextrin-coated iron oxide nanoparticles, this concept has been tested and shown promising results for magnetic drug delivery applications within a short timescale.