Systematic Investigation of Functional Ligands for Colloidal Stable Upconversion Nanoparticles

Abstract

<div> <p>Despite intense efforts on surface functionalization to generate hydrophilic upconversion nanoparticles (UCNPs), long-term colloidal stability in physiological buffers remains a major concern. Here we quantitatively investigate the competitive adsorption of phosphate, carboxylic acid and sulphonic acid onto the surface of UCNPs and study their binding strength to identify the best conjugation strategy. To achieve this, we designed and synthesized three di-block copolymers composed of poly(ethylene glycol) methyl ether acrylate and a polymer block bearing phosphate, carboxylic or sulphonic acid anchoring groups prepared by an advanced polymerization technique, Reversible Addition Fragmentation Chain Transfer (RAFT). Analytical tools provide the evidence that phosphate ligands completely replaced all the oleic acid capping molecules on the surface of the UCNPs compared with incomplete ligand exchange by carboxylic and sulphonic acid groups. In the meanwhile, simulated quantitative adsorption energy measurements confirmed that among three functional groups, calculated adsorption strength for phosphate anchoring ligands is higher which is in good agreement with experimental results regarding the best colloidal stability especially in phosphate buffer solution. The finding suggests that polymers with multiple anchoring negatively charged phosphate moieties provide excellent colloidal stability for lanthanide ion-doped luminescent nanoparticles for various potential applications.</p> </div> <br>

Targeted and stimuli–responsive mesoporous silica nanoparticles for drug delivery and theranostic use

“…For instance, the extracellular GSH (reduced glutathione) level in plasma is 100-1,000 times lower than in intracellular environment (Meister, 1991), which produces redox potential gradient between the reducing intracellular and oxidizing extracellular environments (Colilla, González, & Vallet-Regí, 2013). In addition, the key characteristics of tumor tissue environment include high hypoxia and reducing potential, in comparison with that of normal tissue, due to a fourfold higher GSH level in the tumor cell than in the healthy cell (Duong et al, 2018;Jang & Cha, 2018;Kuppusamy et al, 2002;Xiao et al, 2016;Zhang et al, 2013). Table 2 describes the doxorubicin-loaded redox-responsive systems for chemotherapeutic delivery.…”