Thioether–Polyglycidol as Multivalent and Multifunctional Coating System for Gold Nanoparticles

Abstract

Thiofunctional polymers are the established standard for the coating and biofunctionalization of gold nanoparticles (AuNPs). However, the nucleophilic and oxidative character of thiols provokes polymeric crosslinking and significantly limits the chemical possibilities to introduce biological functions. Thioethers represent a chemically more stable potential alternative to thiols that would offer easier functionalization, yet a few studies in the literature report inconclusive data regarding the efficacy of thioethers to stabilize AuNPs in comparison to thiols. A systematic comparison is presented of mono- versus multivalent thiol- and thioether-functional polymers, poly(ethylene glycol) versus side chain functional poly(glycidol) (PG) and it is shown that coating of AuNPs with multivalent thioether-functional PG leads to superior colloidal stability, even under physiological conditions and after freeze-drying and resuspension, as compared to thiol analogs at comparable polymer surface coverages. In addition, it is shown that a wide range of functional groups can be introduced in these polymers. Using diazirine functionalization as example, it is demonstrated that proteins can be covalently immobilized, and that conjugation of antibodies via this strategy enables efficient targeting and laser-irradiation induced killing of cells.

A strategy for stable and easily modifiable metal particle coatings based on thiol-ene reactive hydrophilic polymers using polyglycidol as an example is presented. It is demonstrated that introducing thioethers along with biofunctional groups, lyophilizable particles that are stable over a wide pH range and in serum can be prepared, and show cell specific targeting through laser induced cell elimination experiments.

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