Water-Soluble Silicon Quantum Dots toward Fluorescence-Guided Photothermal Nanotherapy

Abstract

We report carboxy-terminated silicon quantum dots (SiQDs) that exhibit high solubility in water due to the high molecular coverage of surface monolayers, bright light emission with high photoluminescence quantum yields (PLQYs), long-term stability in the PL property for monitoring cells, less toxicity to the cells, and a high photothermal response. We prepared water-soluble SiQDs by the thermal hydrosilylation of 10-undecenoic acid on their hydrogenterminated surfaces, provided by the thermal disproportionation of triethoxysilane hydrolyzed at pH 3 and subsequent hydrofluoric etching. The 10-undecanoic acid-functionalized SiQDs (UA:SiQDs) showed long-term stability in hydrophilic solvents including ethanol and water (pH 7). We assess their interaction with live cells by means of cellular uptake, short-term toxicity, and, for the first time, long-term cytotoxicity. Results show that UA:SiQDs are potential candidates for theranostics, with their good optical properties enabling imaging for more than 18 days and a photothermal response having a 25.1% photothermal conversion efficiency together with the direct evidence of cell death by laser irradiation. UA:SiQDs have low cytotoxicity with full viability of up to 400 μg/mL for the short term and a 50% cell viability value after 14 days of incubation at a 50 μg/mL concentration.

Effect of the surface coverage of an alkyl carboxylic acid monolayer on waterborne and cellular uptake behaviors for silicon quantum dots

“…4.0 mg of the sample in powder form was heated up to 650 °C with 10 °C/min heating rate under Ar atmosphere in alumina crucibles and mass loss was recorded. By using this data, surface coverage was calculated by the previously reported method 56 .…”

Silicon quantum dots: surface matter, what next?

“…There was a report of carboxy-terminated silicon quantum dots (SiQDs) synthesized by O ¨zbilgin et al (2022) 140 that exhibited high water solubility, luminescent light emission with high PLQYs, long-term stability of PL properties for cell monitoring, lower toxicity to cells and high photothermal response due to the high molecular coverage of the surface monolayer. Watersoluble SiQDs were prepared by thermal hydroxylation of 10-undecenoic acid as ligand, which was ensured by thermal disproportionation of TES hydrolyzed at pH 3 and subsequent etching with hydrogen fluoride.…”

“…UA-SiQDs have low cytotoxicity with full viability up to 400 mg mL À1 in the short term and 50% cell viability after 14 days of incubation at 50 mg mL À1 . 140 The illustrative photodynamic nanotherapy of 10-undecanoic acid functionalized SiQDs depicts in Fig. 17.…”

Imitation-mussel fluorescent silicon quantum dots for selective labeling and imaging of bacteria and biofilms

“…Recently, semiconductor quantum dots, carbon nanodots, and fluorescent silicon quantum dots (SiQDs) have emerged as a new generation of fluorescence materials for their excellent stability and biocompatibility (Gao et al, 2018;Kasouni et al, 2019;Sivasankarapillai et al, 2019;Huang et al, 2020;Gao et al, 2021;Li et al, 2022;Martynenko et al, 2022;O€zbilgin et al, 2022;Zhao et al, 2022). Among these, zero-dimensional SiQDs with high fluorescence quantum yield and narrow emission bands have received increasing attention for the sensing of biological and bacteriologic species.…”