Please refer to our latest publication 2017 on SuperParamagnetic Iron Oxide Nanoparticles (SPIONS). Maybe it is of benefitial to you in answering your question about coating. Gd luck
If your complex in nanoparticles is strong, then why add an extra substance, add an excess of one of the two substances chitosan or quercetin. The additive, in accordance with the law of mass action, will increase the strength of the complex and stabilize the nanoparticles.