Thiol−Ene Induced Diphosphonic Acid Functionalization of Superparamagnetic Iron Oxide Nanoparticles

Abstract

Multifunctional organic molecules represent an interesting challenge for nanoparticle functionalization due to the potential for undesirable interactions between the substrate material and the variable functionalities, making it difficult to control the final orientation of the ligand. In the present study, UV-induced thiol-ene click chemistry has been utilized as a means of directed functionalization of bifunctional ligands on an iron oxide nanoparticle surface. Allyl diphosphonic acid ligand was covalently deposited on the surface of thiol-presenting iron oxide nanoparticles via the formation of a UV-induced thioether. This method of thiol-ene click chemistry offers a set of reaction conditions capable of controlling the ligand deposition and circumventing the natural affinity exhibited by the phosphonic acid moiety for the iron oxide surface. These claims are supported via a multimodal characterization platform which includes thermogravimetric analysis, X-ray photoelectron spectroscopy, and metal contact analysis and are consistent with a properly oriented, highly active ligand on the nanoparticle surface. These experiments suggest thiol-ene click chemistry as both a practical and generally applicable strategy for the directed deposition of multifunctional ligands on metal oxide nanoparticle surfaces.

Nitric oxide donor superparamagnetic iron oxide nanoparticles

“…Replacement of oleic acid by MSA led to MNPs containing sulphydryl (SH) groups on the surface, as identified by FTIR spectroscopy. This technique is useful to identify the most important stretching vibrations of the MSA ligand attached on the particle surface [31]. Fig.…”

A simple method for the quantification of molecular decorations on silica particles

“…The capability of thiol moieties to scavange free radicals assists their regeneration after successful attachment of a thiol–ene bond, effectively acting as a chain transfer process [14] which has potential as a relatively benign means to functionalize particles. However, free radical thiol–ene approaches to form polymeric particle structures and control ligand orientation on magnetic nanoparticles have only been reported to achieve attachment densities of about 0.55 alkene attachments per nm 2 using phosphonic acid derivatives [15], which is significantly lower than other high density attachment mechanisms that currently yield 2–5 attachments per nm 2 , which utilize cycloaddition and ring opening chemical processes [16, 17]. …”

Click Chemistry for Drug Delivery Nanosystems

“…The authors reported modification of allyl-functionalized Fe 3 O 4 NP with cysteine via a one-pot approach hydrolysis-condensation of Fe(III) allylacetylacetonate and TEC (AIBN, EtOH-H 2 O, 60°C). A different strategy was employed by Warner and coworkers, who employed Fe 3 O 4 -mercaptopropionic acid NP further decorated with allyl diphosphonic acid or ester ligands by TEC (benzophenone, UV light, H 2 O or MeOH) (122).…”