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. 2022 Sep 19;23(18):10977.
doi: 10.3390/ijms231810977.

Highly Bright Silica-Coated InP/ZnS Quantum Dot-Embedded Silica Nanoparticles as Biocompatible Nanoprobes

Kyeong-Min Ham  1 , Minhee Kim  1 , Sungje Bock  1 , Jaehi Kim  1 , Wooyeon Kim  1 , Heung Su Jung  2 , Jaehyun An  1   3 , Hobeom Song  3 , Jung-Won Kim  3 , Hyung-Mo Kim  1   4 , Won-Yeop Rho  5 , Sang Hun Lee  6 , Seung-Min Park  7 , Dong-Eun Kim  1 , Bong-Hyun Jun  1
Affiliations

Highly Bright Silica-Coated InP/ZnS Quantum Dot-Embedded Silica Nanoparticles as Biocompatible Nanoprobes

Kyeong-Min Ham et al. Int J Mol Sci. .

Abstract

Quantum dots (QDs) have outstanding optical properties such as strong fluorescence, excellent photostability, broad absorption spectra, and narrow emission bands, which make them useful for bioimaging. However, cadmium (Cd)-based QDs, which have been widely studied, have potential toxicity problems. Cd-free QDs have also been studied, but their weak photoluminescence (PL) intensity makes their practical use in bioimaging challenging. In this study, Cd-free QD nanoprobes for bioimaging were fabricated by densely embedding multiple indium phosphide/zinc sulfide (InP/ZnS) QDs onto silica templates and coating them with a silica shell. The fabricated silica-coated InP/ZnS QD-embedded silica nanoparticles (SiO2@InP QDs@SiO2 NPs) exhibited hydrophilic properties because of the surface silica shell. The quantum yield (QY), maximum emission peak wavelength, and full-width half-maximum (FWHM) of the final fabricated SiO2@InP QDs@SiO2 NPs were 6.61%, 527.01 nm, and 44.62 nm, respectively. Moreover, the brightness of the particles could be easily controlled by adjusting the amount of InP/ZnS QDs in the SiO2@InP QDs@SiO2 NPs. When SiO2@InP QDs@SiO2 NPs were administered to tumor syngeneic mice, the fluorescence signal was prominently detected in the tumor because of the preferential distribution of the SiO2@InP QDs@SiO2 NPs, demonstrating their applicability in bioimaging with NPs. Thus, SiO2@InP QDs@SiO2 NPs have the potential to successfully replace Cd-based QDs as highly bright and biocompatible fluorescent nanoprobes.

Keywords: biocompatible nanoprobes; bioimaging; in vivo; photoluminescence (PL); quantum dots (QDs); silica-coated InP/ZnS QD-embedded silica nanoparticles; syngeneic mice.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Fabrication of SiO2@InP QDs@SiO2 NPs. (a) Schematic illustration for fabrication of SiO2@InP QDs@SiO2 NPs. (b) Transmission electron microscopy (TEM) images of (i) SiO2 NPs, (ii) InP/ZnS QDs (iii), and (iv) SiO2@InP QDs@SiO2 NPs.
Figure 2
Figure 2
Characterization of SiO2@InP QDs@SiO2 NPs. (a) UV/Vis/NIR absorbance spectra of SiO2 NPs, InP/ZnS QDs, and SiO2@InP QDs@SiO2 NPs. (b) Comparison of quantum yield (QY) between InP/ZnS QDs and SiO2@InP QDs@SiO2 NPs. (c) Comparison of photoluminescence (PL) spectra between InP/ZnS QDs and SiO2@InP QDs@SiO2 NPs. (d) Digital images of SiO2@InP QDs@SiO2 NPs distributed in distilled water (DW).
Figure 3
Figure 3
Brightness control of SiO2@InP QDs@SiO2 NPs. (a) TEM image of SiO2@InP QDs@SiO2 NPs via the amount of added QDs. The amount of added QDs were (i) 0 mg, (ii) 0.0875 mg, (iii) 0.175 mg, (iv) 0.35 mg, and (v) 0.7mg per 1 mg of SiO2 NPs. (b) Normalized PL intensity spectra of SiO2@InP QDs@SiO2 NPs via amount of added QDs. (c) Maximum PL intensity of SiO2@InP QDs@SiO2 NPs via amount of added QDs at 527 nm emission wavelength.
Figure 4
Figure 4
In vivo biodistribution of SiO2@InP QDs@SiO2 NPs. (a) Comparison of biodistribution and fluorescence of particles in major organs and tumors after administration of SiO2@InP QDs@SiO2 NPs and hydrophilic CdSe/ZnS QDs to tumor syngeneic mice. (b) Comparison of average radiant efficiency in major organs and tumors.
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Grants and funding

This research was funded by the Ministry of Science and ICT (NRF-2022R1A2C2012883), and supported by the Konkuk University Researcher Fund in 2020 (2020-A019-0280). Further, this research was supported by the Korea Initiative for fostering University of Research and Innovation Program of the National Research Foundation (NRF), funded by the Korean government (MSIT) (No. NRF2021M3H1A104892211).

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