. 2017 Apr 25;7(5):93.

doi: 10.3390/nano7050093.

Probing Temperature- and pH-Dependent Binding between Quantum Dots and Bovine Serum Albumin by Fluorescence Correlation Spectroscopy

Zonghua Wang¹, Qiyan Zhao^{2

3

4}, Menghua Cui^{5

6}, Shichao Pang⁷, Jingfang Wang⁸, Ying Liu⁹, Liming Xie^{10

11}

Affiliations

¹ Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Qingdao University, Qingdao 266071, China. wangzonghua@qdu.edu.cn.
² Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Qingdao University, Qingdao 266071, China. zhaoqy@nanoctr.cn.
³ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. zhaoqy@nanoctr.cn.
⁴ Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing 100190, China. zhaoqy@nanoctr.cn.
⁵ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. cuimh@nanoctr.cn.
⁶ University of Chinese Academy of Sciences, Beijing 100049, China. cuimh@nanoctr.cn.
⁷ School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China. scpang@sjtu.edu.cn.
⁸ Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai 200240, China. jfwang8113@sjtu.edu.cn.
⁹ Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing 100190, China. liuy1@nanoctr.cn.
¹⁰ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. xielm@nanoctr.cn.
¹¹ University of Chinese Academy of Sciences, Beijing 100049, China. xielm@nanoctr.cn.

PMID: 28441351
PMCID: PMC5449974
DOI: 10.3390/nano7050093

Probing Temperature- and pH-Dependent Binding between Quantum Dots and Bovine Serum Albumin by Fluorescence Correlation Spectroscopy

Zonghua Wang et al. Nanomaterials (Basel). 2017.

. 2017 Apr 25;7(5):93.

doi: 10.3390/nano7050093.

Authors

Zonghua Wang¹, Qiyan Zhao^{2

3

4}, Menghua Cui^{5

6}, Shichao Pang⁷, Jingfang Wang⁸, Ying Liu⁹, Liming Xie^{10

11}

Affiliations

¹ Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Qingdao University, Qingdao 266071, China. wangzonghua@qdu.edu.cn.
² Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, College of Chemistry and Chemical Engineering, Shandong Sino-Japanese Center for Collaborative Research of Carbon Nanomaterials, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Qingdao University, Qingdao 266071, China. zhaoqy@nanoctr.cn.
³ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. zhaoqy@nanoctr.cn.
⁴ Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing 100190, China. zhaoqy@nanoctr.cn.
⁵ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. cuimh@nanoctr.cn.
⁶ University of Chinese Academy of Sciences, Beijing 100049, China. cuimh@nanoctr.cn.
⁷ School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China. scpang@sjtu.edu.cn.
⁸ Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai 200240, China. jfwang8113@sjtu.edu.cn.
⁹ Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing 100190, China. liuy1@nanoctr.cn.
¹⁰ CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China. xielm@nanoctr.cn.
¹¹ University of Chinese Academy of Sciences, Beijing 100049, China. xielm@nanoctr.cn.

PMID: 28441351
PMCID: PMC5449974
DOI: 10.3390/nano7050093

Abstract

Luminescent quantum dots (QDs) with unique optical properties have potential applications in bio-imaging. The interaction between QDs and bio-molecules is important to the biological effect of QDs in vivo. In this paper, we have employed fluorescence correlation spectroscopy (FCS) to probe the temperature- and pH-dependent interactions between CdSe QDs with carboxyl (QDs-COOH) and bovine serum albumin (BSA) in buffer solutions. The results have shown that microscopic dissociation constant K'_D is in the range of (1.5 ± 0.2) × 10^-5 to (8.6 ± 0.1) × 10^-7 M, the Hill coefficient n is from 0.4 to 2.3, and the protein corona thickness is from 3.0 to 9.4 nm. Variable-temperature measurements have shown both negative values of ∆H and ∆S for BSA adsorption on QDs-COOH, while pH has a profound effect on the adsorption. Additional, FCS measurement QDs-COOH and proteins in whole mice serum and plasma samples has also been conducted. Finally, simulation results have shown four favored QD binding sites in BSA.

Keywords: fluorescence correlation spectroscopy; luminescent quantum dots; simulation; temperature-and pH-dependent interactions.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

**Figure 1**
(a) Typical transmission electron microscopy (TEM) image and (b) the corresponding particle size distributions of carboxyl ZnS/CdSe quantum dots (QDs-COOH); (c) Dynamic light scattering (DLS) correlation curves of QDs-COOH; and (d) fluorescence emission spectra and ultraviolet-visible spectroscopy (UV-VIS) spectra of QDs-COOH.

**Figure 2**
(a) Scheme of FCS system; (b) FCS correlation curves; (c–f) hydrodynamic radii of QDs-COOH at different BSA concentrations (pH = 7.4) at different temperatures (298 K, 300 K, 303 K, and 308 K); (g) Plot of *K′_D* (red line), ∆R (black line) versus temperature; and (h) the plot of lnK against 1/T.

**Figure 3**
(a) Selected pH points for QDs-COOH and BSA binding in FCS measurements; (b) FCS correlation curves; (c–e) hydrodynamic radii of QDs-COOH at different pH (300 K); (f) *K’_D* at different temperatures and pH; and (g) the protein corona thickness at different temperatures and pH.

**Figure 4**
(a) Circula dichroism (CD) spectroscopy of bovine serum albumin (BSA) at different pH (6.0, 7.4, and 9.0); (b–d) CD of QDs-COOH, BSA, and a mixture of QDs-COOH (4 nM) and BSA (0.2 mM) at different pH (6.0, 7.4, and 9.0). In CD experiments, concentrations of QDs-COOH and BSA were 20 nM and 5 nM, respectively.

**Figure 5**
Protein corona thickness of quantum dots in plasma, serum, and BSA solution at different temperatures (298 and 310 K).

**Scheme 1**
The structure of BSA and the simulation result showing the location of the four binding sites (1–4) for QDs-COOH.

See this image and copyright information in PMC

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Probing Temperature- and pH-Dependent Binding between Quantum Dots and Bovine Serum Albumin by Fluorescence Correlation Spectroscopy

Affiliations

Probing Temperature- and pH-Dependent Binding between Quantum Dots and Bovine Serum Albumin by Fluorescence Correlation Spectroscopy

Authors

Affiliations

Abstract

Conflict of interest statement

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