Selenium-Containing Amphiphiles Reduced and Stabilized Gold

Subscriber access provided by Northern Illinois University

Article

Selenium-containing Amphiphiles Reduced and Stabilized Gold Nanoparticles: Kill Cancer Cells via Reactive Oxygen Species Tianyu Li, Feng Li, Wentian Xiang, Yu Yi, Yuyan Chen, Liang Cheng, Zhuang Liu, and Huaping Xu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 12 Aug 2016 Downloaded from http://pubs.acs.org on August 13, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Selenium-containing Amphiphiles Reduced and Stabilized Gold Nanoparticles: Kill Cancer Cells via Reactive Oxygen Species

Tianyu Li, † Feng Li, † Wentian Xiang, † Yu Yi, † Yuyan Chen, ‡ Liang Cheng, ‡ Zhuang Liu,*, ‡ and Huaping Xu*, †

†

Key Lab of Organic Optoelectronics & Molecular Engineering, Department of

Chemistry, Tsinghua University, Beijing, 100084, People’s Republic of China ‡

Institute of Functional Nano & Soft Materials Laboratory (FUNSOM), Collaborative

Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215123, People’s Republic of China.

Abstract

Selenium has attracted increasing interest in the past decades because of

the function of regulating the redox balance in human body. However, biomedical studies of selenium are still limited. Gold nanoparticles (AuNPs), typically prepared by a first reduction step followed by a second stabilization step, are widely applied in biomedical studies. But their own anti-cancer activity is less studied. Here, we report 2-nm AuNPs with significant anti-cancer activity (IC50 = 20 μM) that stabilized by a selenium-containing amphiphile EGSe-tMe. The AuNPs were prepared by simply mixing chloroauric acid (HAuCl4) with EGSe-tMe, which acts as both a reducing agent and stabilizer. In contrast to AuNPs prepared by EGSe-tMe, EGSe-tMe alone and typically prepared AuNPs show little anti-cancer activity even at concentrations

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

up to 250 μM. Mechanistic studies suggest that selenium in cooperation with AuNPs can induce high concentrations of reactive oxygen species (ROS) in cancer cells, leading to cellular apoptosis.

Keywords

selenium;

gold nanoparticle; anti-cancer; reactive oxygen species;

self-assembly

INTRODUCTION Selenium is an essential trace element in the human body and has gradually become a hotspot for research in the past years.1-2 It was recently demonstrated that three global mass extinction events were strongly linked to selenium depletion,3 which was soon highlighted by both Science and Nature. However, little attention had been paid to selenium until the 1970s, when selenium was found in glutathione peroxidase with the function of preventing cellular damage from reactive oxygen species (ROS, e.g., hydroxyl radicals and oxygen superoxides). In humans, selenium has the unique ability of controlling the concentration of ROS, thus regulating the redox balance in the body.4 At low concentrations, selenium can eliminate ROS to promote cell growth, while at high concentrations, it can induce production of ROS, which would induce mitochondrial dysfunction and lead to cellular apoptosis. This unique feature endows selenium potential anti-cancer activity by inducing apoptosis of cancer cells.5-7 But until now, biomedical studies on selenium-containing systems are still limited because of worries about their toxicity and the difficulties associated with their use in organic


Page 2 of 28

Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


synthesis. A few selenium-containing systems like selenium-containing polymers have recently been developed as promising biomaterials for controlled drug delivery or for antioxidant purposes based on their excellent redox-responsive behavior.8-14 However, these systems focused mainly on the responsive properties based on the low bond energy of C-Se and Se-Se. Studies about the anti-cancer properties of selenium itself have seldom been reported.15-17 Over the past decades, gold nanoparticles (AuNPs) have fascinated scientists in the fields of chemistry, biology, medicine, and engineering.18-22 The broad applications of AuNPs benefited from their unique properties, such as size- and shape-dependent optical properties, excellent stability, good biocompatibility, and ease of surface modification with various functional groups.23-26 In the field of biomedicine, AuNPs are generally considered less toxic and are mostly used for photothermal therapy, photodynamic therapy, and bio-imaging, while the anti-cancer activity of AuNPs has barely been reported.27-28 On the other hand, most AuNPs are synthesized via a two-step method.29-31 HAuCl4 is first reduced by NaBH4 and is then stabilized by ligands such as citrate or thiols to form AuNPs.32-33 Herein, we report a one-step AuNP preparation method in which chloroauric acid (HAuCl4) was reduced and stabilized simultaneously by a selenium-containing amphiphile

EGSe-tMe

(Scheme

1).

The

resulting

2-nm

AuNPs

with

selenium-containing ligands (AuNP/Se) exhibited the ability to induce production of ROS in cancer cells, leading to cellular apoptosis.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 28

Scheme 1. Schematic diagram showing the preparation and the anti-cancer mechanism of AuNP/Se.

RESULTS AND DISCUSSION Preparation and characterization of AuNP/Se. EGSe-tMe was synthesized as described in our previous work.34 The molecule was amphiphilic because it consisted of

a

hydrophobic

head

(trimethylbenzene

portion)

and

hydrophilic

tails

(trioxadodecane portion) (Figure 1a). 35 EGSe-tMe could self-assemble into spherical aggregates with diameters of approximately 190 nm in water. To prepare AuNP/Se, HAuCl4 was added into the EGSe-tMe solution. The solution was kept overnight in a shaking bed at 35 oC, yielding a yellow solution of AuNP/Se (Figure S1a). The UV-Vis absorbance spectrum of AuNP/Se was collected as shown in Figure S1b. The characteristic peak of typical AuNPs with surface plasmon resonance (SPR) was not found, which suggested the formation of AuNPs smaller than 3 nm.36-38


Page 5 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1 a) Molecular structure of selenium-containing amphiphile EGSe-tMe. b) TEM figures of AuNP/Se without staining. The scale bars represent 500 nm. The inset is a zoomed-in TEM figure of AuNP/Se. The scale bar represents 20 nm. c) EDS spectrum of AuNP/Se. d) Size distribution (diameter) of small AuNPs in AuNP/Se.

Spherical aggregates formed by self-assembly of EGSe-tMe-stabilized AuNPs were imaged by Transmission electron microscope (TEM) without staining. The images indicated that the diameter of the spherical aggregates was approximately 150 nm (Figure 1b). In the zoomed image, small AuNPs with diameters of approximately 2 nm could be observed. The small area of the dark dots was detected with energy dispersive spectrometry (EDS) (Figure 1c). The EDS spectrum demonstrated that the assembly was mainly composed of Au and Se elements. Size uniformity is an important criterion for AuNP preparation methods. The diameters of AuNP/Se were measured as 2.2 ± 0.4 nm based on the TEM figure (Figure 1d). AuNPs larger than 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

nm have already been widely utilized in anti-cancer systems as drug carriers and imaging agents.39-41 However, AuNPs smaller than 3 nm are less studied because of the difficulty of their synthesis42 and the loss of SPR features. Despite losing SPR, these smaller AuNPs have special advantages in tumor penetration and endosomal escape, which are important for cancer treatment.43-44

Figure 2 XPS spectra of Se in EGSe-tMe (a), AuNP/Se (b), and Au of AuNP/Se (c). Cyclic voltammograms of HAuCl4 (d) and EGSe-tMe (e) in phosphate buffer with a conventional three-electrode glass electrochemical cell at room temperature. f) The 77

Se NMR spectra (600 MHz, DMSO-d6, 298 K) of EGSe-tMe and AuNP/Se.


Page 6 of 28

Page 7 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Reaction between EGSe-tMe and HAuCl4. The reaction between EGSe-tMe and HAuCl4 was first studied by X-ray photoelectron spectroscopy (XPS) and cyclic voltammograms (CVs). In the XPS spectra of AuNP/Se, the bonding energies of the Au 4f peaks were 84.42 eV and 88.12 eV (Figure 2a-c), indicating the formation of Au (0).45 The binding energy of the Se 3d peak increased from 55.37 eV to 55.77 eV, revealing the oxidation of selenium in EGSe-tMe during the reaction with HAuCl4. These results demonstrated that selenium acted as the reducing agent in the reduction of HAuCl4 to Au (0). To further confirm the hypothesis above, the oxidation potentials of EGSe-tMe and HAuCl4 were detected with CVs (Figure 2d, e). The oxidation potentials of EGSe-tMe and HAuCl4 were 0.955 V and 0.978 V, respectively. The higher potential of HAuCl4 indicated a stronger oxidizing ability compared with EGSe-tMe, confirming that the redox reaction between EGSe-tMe and HAuCl4 was feasible. Nuclear magnetic resonance (NMR) spectra of EGSe-tMe and AuNPs/Se were collected for further investigation of the redox reaction.46 (Figure 2f). In

77

Se-NMR

spectrum, the signal corresponding to selenium in EGSe-tMe shifted from 155 ppm to 278 ppm, suggesting the formation of Se-Au bonds. In the 1H-NMR spectrum of EGSe-tMe, signals corresponding to protons near the selenium atoms (Hb and Hc) shifted downfield after the redox reaction, indicating that the interactions formed between selenium and gold (Figure S3, S4). These results further demonstrated that AuNPs were stabilized by the selenium in AuNP/Se. The function of selenium reducing and stabilizing gold resulted from their own properties. AuNPs are usually



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

stabilized with thiols via interactions between gold and sulfur47. Selenium and sulfur belong to the same group in the periodic table. They share some features, such as good biocompatibility and ease of modification at the surface of AuNPs.48 However, selenium has some different properties. The electronegativity of selenium is lower than that of sulfur, making it a stronger reducing agent and thus increasing the possibility of reducing HAuCl4 to Au (0). The electronegativity and atomic radius of selenium are closer to gold than sulfur, which would lead to the formation of more covalent bonds and enhanced stability for selenium-stabilized AuNPs.49-50

Figure 3 a) Anti-cancer activities of AuNP/Se, EGSe-tMe and AuNP/Citrate. b) Fluorescence intensity of DCFH determining the concentration of ROS. c) Confocal fluorescence images of cells treated with AuNP/Se showing the concentration of ROS in cells. Scale bar represents 30 μm. d) Absorbance of WST-1 showing the presence of oxygen superoxides in cells. e) Fluorescence intensity of DAF-FM DA determining the concentration of nitric oxide in cells. f) Fluorescence intensity of JC-1 determining the changes in mitochondrial membrane potential.


Page 8 of 28

Page 9 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Anti-cancer activity of AuNP/Se in vitro. AuNPs are commonly considered to possess low anti-cancer activity,51 and are used widely for drug delivery, bio-imaging, and other areas. Our previous study demonstrated that EGSe-tMe was also a molecule with low anti-cancer activity34. However, the combination of these two species resulted in a system with good anti-cancer activity. The anti-cancer activity of AuNP/Se was first studied in vitro with HepG2 human liver cancer cells (Figure 3a). Cell counting kit-8 (CCK-8) was employed to test the viability of HepG2 cells treated with different forms of drugs. AuNP/Se showed significant anti-cancer activity even at low concentrations, with an IC50 value of 20 μM. However, EGSe-tMe and AuNP/Citrate (AuNPs reduced by NaBH4 and stabilized by citrate) did not exhibit clear anti-cancer activity even at concentrations up to 250 μM, with cell viability remaining higher than 80%. The differences in anti-cancer activity between AuNP/Se and AuNP/Citrate were further confirmed in MDA-MB-231 human breast cancer cell line, A549 human lung adenocarcinoma cell line and 4T1 murine breast cancer cell line (Figure S5). This interesting phenomenon showed that two low-activity species could be combined to create a novel system with apparent anti-cancer activity. Mechanism of the anti-cancer activity. The mechanism of the anti-cancer activity of AuNP/Se was studied via fluorescence analysis. Selenium is considered to regulate the concentration of ROS in cells. AuNPs have also been reported to induce the production of ROS under some special conditions.52-53 The concentration of ROS in HepG2 cells was tested with DCFH-DA, a fluorescent probe that specifically identifies ROS. Based on the results of the cell viability experiments, HepG2 cells



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

were treated with 100 μM AuNP/Se for 1 h, 3 h, 6 h and 24 h before assaying the ROS concentration (Figure S6). The fluorescence intensity resulted from DCFH-DA increased rapidly in 3 h, showing the production of ROS. HepG2 cells incubated with EGSe-tMe or AuNP/Citrate for 3 h only exhibited a slight increase in fluorescence intensity (Figure 3b), which suggested little production of ROS. These results demonstrated a synergy effect between AuNPs and Se ligands in inducing a high concentration of ROS in cancer cells. To confirm this synergy effect, confocal microscopy was utilized to observe the fluorescence intensity change directly (Figure 3c, S7). HepG2 cells were treated with AuNP/Se, AuNP/Citrate, EGSe-tMe and PBS for 3 h, respectively. Cells treated with AuNP/Se exhibited strong fluorescence, which confirmed the great ability of AuNP/Se in inducing ROS production. In contrast, little fluorescence could be observed in the cells treated with AuNP/Citrate or EGSe-tMe. ROS is a generic term for chemically reactive oxygen-containing molecules, including peroxides, superoxides, and nitric oxide. Different types of ROS have various toxicities to cancer cells. Superoxides and nitric oxide are considered to play important roles in the process of cellular apoptosis. The probes WST-1 and DAF-FM DA were used to specifically detect superoxides and nitric oxide, respectively (Figure 3d, e). HepG2 cells were treated with AuNP/Se, AuNP/Citrate, EGSe-tMe and PBS for 3 h, respectively. The cells treated with AuNP/Se exhibited strong fluorescence in the assays for both superoxides and nitric oxide compared with the cells in the other three groups. The strong fluorescence indicated the production of both superoxides and nitric oxide induced by AuNP/Se. We speculated that AuNP/Se induced a


Page 10 of 28

Page 11 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


comprehensive increase in ROS production instead of stimulating a specific signaling pathway in cancer cells. To confirm that ROS induced by AuNP/Se contributed to the cellular apoptosis process, the mitochondrial membrane potential of HepG2 cells was detected with the probe JC-1 (Figure 3f). The mitochondrial membrane potential is a parameter that can reflect the mitochondrial function. And mitochondrial dysfunction has been reported to be a prelude to ROS-induced cellular apoptosis. HepG2 cells were treated with AuNP/Se, AuNP/Citrate, EGSe-tMe and PBS for 3 h, respectively. The cells treated with AuNP/Se showed strong green fluorescence compared with the PBS-treated cells, which indicated a high level of mitochondrial dysfunction. AuNP/Citrate and EGSe-tMe could only trigger a low level of mitochondria dysfunction. These data further confirmed that AuNP/Se induced cellular apoptosis via the ROS-mediated mechanism. Additionally, the nanoparticles were stabilized in spherical aggregates with diameters of approximately 150 nm. Therefore, they would possess the ability to target tumor tissues via the EPR (enhanced permeation and retention) effect. Cellular uptake experiments suggested that AuNP/Se had good transmembrane ability (Figure S8). These features endowed the AuNP/Se system a good potential in applications of cancer treatment. Anti-cancer activity of AuNP/Se in vivo. Encouraged by the promising in vitro results of AuNP/Se, in vivo experiments were performed by assessing the tumor growth inhibition exerted by AuNP/Se in Balb/c mice bearing s.c. tumors derived from 4T1 cells (Figure 4). 1.5 mg/kg AuNP/Se, AuNP/Citrate, or EGSe-tMe were administrated by injection twice after the tumors formed (at day 0 and day 8). The



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

same volume of PBS was used as control. Little inhibition on tumor growth was observed in mice treated with AuNP/Citrate, EGSe-tMe, or PBS. However, treatment with AuNP/Se significantly inhibited the tumor growth. Chemotherapy drugs, such as cisplatin, always cause severe side effects, which can result in extreme emaciation. Fortunately, mice treated with AuNP/Se showed no significant alteration of body weight, which suggested the low systemic toxicity of AuNP/Se.

Figure 4 a) Relative tumor volume in mice after various treatments. Four groups of mice on day 0 and day 8 were administrated by injection of the following reagents: (i) PBS (control); (ii) AuNP/Citrate; (iii) EGSe-tMe, or (iv) AuNP/Se, with concentrations of 5 mM in 30 μL. Error bars show the standard error of the mean (SEM, n=5). b) Weight loss in mice after treated with different drugs. c) Photos of mice after treatment with different drugs, taken on day 10.


Page 12 of 28

Page 13 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CONCLUSIONS In this study, we have developed a single-step method to prepare uniform 2-nm AuNPs with significant anti-cancer activity. The selenium-containing amphiphile EGSe-tMe was introduced to reduce HAuCl4 and stabilize AuNPs simultaneously. In vitro experiments revealed that EGSe-tMe could cooperate with AuNPs to induce the production of ROS in cancer cells, which further caused the mitochondrial dysfunction and led to cellular apoptosis. In vivo experiments suggested that AuNP/Se possessed great anti-cancer activity with low systemic toxicity. We envisage that this method will breathe new life into the development of AuNPs smaller than 3 nm as well as the study of selenium-containing molecules in the fields of cancer treatment.

ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge via the Internet at http://pubs.acs.org. Additional characterizations of AuNP/Se and the reaction between EGSe-tMe and HAuCl4, results of cytotoxicity assay and fluorescent assay in vitro.

AUTHOR INFORMATION Corresponding Author *[email protected] *[email protected] Notes The authors declare no competing financial interest.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 28

ACKNOWLEDGMENT This work was supported by National Science Foundation for Distinguished Young Scholars (21425416), the National Natural Science Foundation of China (91427301, 51302180,

51572180),

the

National

Basic

Research

Program

of

China

(2013CB834502, 2012CB932601), and the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (21421064).

EXPERIMENTAL SECTION Chemicals. Triethylene glycol monomethyl ether and chloroauric acid were purchased from Sigma-Aldrich Corporation. 1,3,5-Tri(bromomethyl)-2,4,6-trimethyl -benzene was purchased from Tokyo Chemical Industry Co., Ltd. Selenium powder and Sodium borohydride were purchased from Aladdin Chemical Reagent Co., Ltd. 4-Toluene sulfonyl chloride was purchased from J&K Scientific. Pure water was acquired from a Milli-Q water filtration system. Other chemicals and organic solvents were analytical grade products from Beijing Chemical Reagent Company. All chemicals were used as received. Synthesis of EGSe-tMe. EGSe-tMe (12,12',12''-(2,4,6-trimethylbenzene-1,3,5-triyl) tris(2,5,8- trioxa-11-selenadodecane)) was synthesized according to our previous work.1,2 First, 0.227 g NaBH4 (6.0 mmol) was dissolved in 10 mL H2O. To the NaBH4 solution, 0.474 g Se powder (6.0 mmol) was added slowly. After the reaction became mild, the solution was protected with a nitrogen atmosphere and stirred at 50 °C for 30 min until the solution turned dark red. 2-(2-(2-methoxyethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (TEG-Ts) was synthesized according to previous research.


Page 15 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Then, 1.910 g TEG-Ts (6.0 mmol) was dissolved in 50 mL acetonitrile and added slowly to the dark red solution. After being stirred at 50 °C in a nitrogen atmosphere for 5 h, the mixture was cooled to room temperature and concentrated using a rotary evaporator. The concentrated mixture was extracted with dichloromethane three times. The organic layer was washed with H2O twice and then dried with sodium sulfate to obtain

2,5,8,15,18,21-hexaoxa-11,12-diselenadocosane

(TEG-SeSe-TEG).

TEG-SeSe-TEG was dissolved in 30 mL tetrahydrofuran. To the solution, 0.758 g 1,3,5-tri(bromomethyl)-2,4,6-trimethylbenzene was added, and the resulting mixture was then protected with a nitrogen atmosphere. Ten milliliters of H2O was used to dissolve 0.454 g sodium borohydride (12.0 mmol) and 0.024 g sodium hydroxide (0.6 mmol), which was then added into the mixture. After being stirred in a nitrogen atmosphere at room temperature for 5 h, the mixture was concentrated using a rotary evaporator. The concentrated mixture was extracted with dichloromethane three times. The organic layer was washed with H2O twice and dried with sodium sulfate. The sample was purified by column chromatography (dichloromethane:methanol = 50:1) to obtain EGSe-tMe with a yield of 61%. 1H NMR (400 MHz, CDCl3, ppm): δ 3.92 (s, 6H, CH2CH2OCH2CH2SeCH2-), 3.74 (m, 6H, CH2CH2OCH2CH2SeCH2-), 3.68-3.63 (m, 18H, CH3OCH2CH2OCH2CH2O-), 3.55 (m, 6H, CH3OCH2CH2OCH2CH2O-), 3.38 (s, 9H, CH3OCH2CH2OCH2CH2O-), 2.77 (t, 6H, CH2CH2OCH2CH2SeCH2-), 2.43 (s, 9 H, CH3Ph-).

13

C NMR (400 MHz, CDCl3, ppm): δ 134.50, 133.41, 72.01,

71.95, 70.73, 70.64, 70.24, 59.11, 24.52, 23.89, 16.10. ESI-MS: m/z (%) 859.9 (71), 863.5 (93), 861.6 [M+Na]+ (100).



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Preparation of AuNPs.

Page 16 of 28

HAuCl4 was dissolved in H2O at a concentration of 10 mM

as the working solution. Four hundred microliters of the HAuCl4 working solution (4×10-3 mmol) was added to a solution of 6.70 mg (8×10-3 mmol) EGSe-tMe in 3.6 mL water. The solution was stirred for 24 h at room temperature. Four milliliters of a yellow transparent solution was obtained, with 1 mM AuNP/Se (EGSe-tMe: HAuCl4 = 2: 1). AuNP/Se with different ratios of EGSe-tMe to HAuCl4 were synthesized by a similar method. AuNP/Citrate was synthesized according to previous work. Nuclear magnetic resonance (NMR) characterization.

1

H NMR and

13

C NMR

spectra were recorded at 298 K on a JEOL JNM-ECA 400 (400 MHz) NMR spectrometer.

77

Se NMR spectra were recorded at 298 K on a JEOL JNM-ECA 600

(600 MHz) NMR spectrometer. The chemical shifts were referenced to the solvent resonance signals. X-ray photoelectron spectroscopy (XPS) characterization.

XPS spectra were

obtained with a Thermo Fisher ESCALAB 250Xi XPS spectrometer. The samples were dropped on silica wafers in aqueous solution and then dried in vacuum to form liquid films for XPS characterization. Transmission electron microscopy (TEM) characterization. TEM figures were obtained with an H-7650B Microscope with an accelerating voltage of 80 kV. Aqueous solutions of the samples were dropped on carbon-coated copper grids and left for 10 min, then observed without staining. The size of AuNP/Se was measured with the software Nano Measurer 1.2. Energy dispersive spectroscopy (EDS) spectra were obtained using a JEM-2010 Microscope.


Page 17 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Dynamic light scattering (DLS) characterization. DLS spectra were obtained at 25 °C on a Malvern Zetasizer Nano ZS90 to measure size, molecular weight and zeta potential. A monochromatic coherent He-Ne laser (633 nm) was used as the light source. Cyclic voltammetry (CV) characterization.

CV spectra were obtained with a

conventional three-electrode glass electrochemical cell at room temperature. Phosphate buffer was used to ensure sufficient conductivity. A glassy carbon electrode was used as the working electrode, a carbon electrode was used as the auxiliary electrode, and a Ag/AgCl electrode was used as the reference electrode. The negative indicator was a solution of 2 mM K3[Fe(CN)6] and 0.1 M KCl. Prior to measurements, the electrolyte solutions were purged with nitrogen for 30 min. During the measurements, a constant flow of nitrogen was applied above the electrolyte solutions. The potential sweep rate was 100 mV s-1. Cell culture. The HepG2 human hepatoma cell line, MDA-MB-231 human breast cancer cell line, A549 human lung adenocarcinoma cell line and 4T1 murine breast cancer cell line were provided by the Cell Resource Center, Shanghai Institutes for Biological Sciences (SIBS, China). All cell lines were grown at 37 ºC in 5% CO2-humidified environment in Dulbecco's Modified Eagle Medium (DMEM, Gibco, USA) supplemented with 10% fetal bovine serum (Gibco, USA) and 1% penicillin/streptomycin. Cytotoxicity study.

AuNP/Se, AuNP/Citrate, and EGSe-tMe were diluted in

DMEM before testing. Their cytotoxicity to HepG2, MDA-MB-231, A549 and 4T1



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

cells was tested by seeding them in 96-well plates at a density of 1×104 cells per well. The cells were kept in culture for 24 h before replacing the medium with media containing the drugs at different concentrations. After 24 h, cytotoxicity was quantified by adding 10 μL cell counting kit-8 (Dojindo) reagent to each well. The cells were incubated at 37 °C for 1 h. Then, the absorbance at 450 nm was read on a microplate reader (Themo Multiscan MK3, USA). The results were presented as the average values ± standard deviation (n=5). Cell uptake study.

In a 24-well plate, 2×105 HepG2 cells were seeded per well. The

cells were kept in culture for 24 h before replacing the medium with media containing 20 μM drugs. After 3 h of incubation, the cells were washed three times with PBS and counted. Then, cells in each well were lysed with 1 mL lysis buffer for 15 min and digested with 1 mL 5% aqua regia for 10 min. Samples in each well were diluted to 5 mL. The amount of Au and Se taken up by the cells was measured by ICP-MS. Each result was repeated three times. ROS assay.

The intracellular concentration of ROS was determined using a

microplate reader and confocal microscope. AuNP/Se, AuNP/Citrate and EGSe-tMe were diluted to 100 μM in DMEM before testing. HepG2 cells were seeded in 96-well plates at a density of 1×104 cells per well. The cells were kept in culture for 24 h before replacing the medium with media containing drugs. After 3 h, the media with drugs were replaced with DCFH-DA (dichloroﬂuorescein diacetate, 5 μg/mL) in DMEM. The cells were incubated at 37 °C for 30 min, then washed three times with PBS. The fluorescence was tested on a microplate reader using excitation/emission


Page 18 of 28

Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


wavelengths (Ex/Em) of 488/525 nm. The results are presented as the average values ± standard deviation (n=5). To prepare samples for confocal microscopy, HepG2 cells were seeded in confocal dishes at a density of 5×104 cells per dish. The cells were kept in culture for 24 h before replacing the medium with media containing 100 μM drugs. After 3 h, the media with drugs were replaced with DCFH-DA (5 μg/mL) in DMEM. The cells were incubated at 37 °C for 30 min, then washed with PBS for three times. One milliliter of 4% paraformaldehyde was added to each dish for 5 min to fix the cells. The cells were washed with PBS three times and then observed on a confocal microscope using an Ex/Em of 488/525 nm and a light field. Intracellular concentrations of nitric oxide and oxygen superoxide were determined via similar procedures, except that nitric oxide was detected by DAF-FM DA (3-amino,4-aminomethyl-2',7'-difluorescein diacetate) using an Ex/Em of 495/515 nm, and oxygen superoxide was detected by WST-1 (water-soluble tetrazolium-1) with catalase using the absorbance at 450 nm. Mitochondrial membrane assay. Changes in mitochondrial membrane potential were determined by the JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide) mitochondrial membrane potential assay kit according to the manufacturer’s instructions. The conditions were similar to those used for the ROS assay, and the fluorescence was tested using an Ex/Em of 488/525 nm on a microplate reader. In vivo study.

Balb/c mice were obtained from Nanjing Peng Sheng Biological

Technology Co. Ltd. and used under protocols approved by the Soochow University



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Laboratory Animal Center. 4T1 tumors were generated by the subcutaneous injection of 1×106 cells in approximately 30 　L serum-free RPMI-1640 medium into the back of each female Balb/c mouse. After the tumor volume reached approximately 70 mm3, mice were randomly divided into the following four groups (n = 5 per group) for various treatments: PBS control (i), AuNP/Citrate (ii), EGSe-tMe (iii), or AuNP/Se (iv) was intratumorally injected into mice bearing 4T1 tumors with concentrations of 5 mM in 30 　L. On day 8, each group was intratumorally injected with the above solution again. The tumor sizes were measured with a caliper every other day, and the volume (V) of each was calculated as V = (tumor length) × (tumor width)2/2. The relative tumor volumes were calculated as V/V0 (V0 was the initial tumor volume).

REFERENCES (1) Huang, X.; Liu, X.; Luo, Q.; Liu, J.; Shen, J., Artificial selenoenzymes: designed and redesigned. Chem. Soc. Rev. 2011, 40, 1171‐1184. (2) Mugesh, G.; Singh, H. B., Synthetic organoselenium compounds as antioxidants: glutathione peroxidase activity. Chem. Soc. Rev. 2000, 29, 347‐357. (3) Long, J. A.; Large, R. R.; Lee, M. S. Y.; Benton, M. J.; Danyushevsky, L. V.; Chiappe, L. M.; Halpin, J. A.; Cantrill, D.; Lottermoser, B., Severe selenium depletion in the Phanerozoic oceans as a factor in three global mass extinction events. Gondwana Research 2015, DOI: 10.1016/j.gr.2015.10.001.


Page 20 of 28

Page 21 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(4) Wang, M.; Sun, S.; Neufeld, C. I.; Perez‐Ramirez, B.; Xu, Q., Reactive oxygen species‐responsive protein modification and its intracellular delivery for targeted cancer therapy. Angew. Chem. Int. Ed. 2014, 53, 13444‐13448. (5) Valko, M.; Rhodes, C. J.; Moncol, J.; Izakovic, M.; Mazur, M., Free radicals, metals and antioxidants in oxidative stress‐induced cancer. Chem. Biol. Interact. 2006, 160, 1‐40. (6) Schrauzer, G. N., Anticarcinogenic effects of selenium. Cell Mol. Life Sci. 2000, 57, 1864‐1873. (7) Ip, C.; Hayes, C.; Budnick, R. M.; Ganther, H. E., Chemical form of selenium, critical metabolites, and cancer prevention. Cancer Res. 1991, 51, 595‐600. (8) Zeng, H.; Combs, G. F., Jr., Selenium as an anticancer nutrient: roles in cell proliferation and tumor cell invasion. J. Nutr. Biochem. 2008, 19, 1‐7. (9) Deng, Z.; Yu, L.; Cao, W.; Zheng, W.; Chen, T., A selenium‐containing ruthenium complex as a cancer radiosensitizer, rational design and the important role of ROS‐mediated signalling. Chem. Commun. 2015, 51, 2637‐2640. (10) Xu, H. P.; Cao, W.; Zhang, X., Selenium‐Containing Polymers: Promising Biomaterials for Controlled Release and Enzyme Mimics. Acc. Chem. Res. 2013, 46, 1647‐1658. (11) Jiang, W.; Fu, Y.; Yang, F.; Yang, Y.; Liu, T.; Zheng, W.; Zeng, L.; Chen, T., Gracilaria lemaneiformis polysaccharide as integrin‐targeting surface decorator of selenium nanoparticles to achieve enhanced anticancer efficacy. ACS Appl. Mater. Interfaces 2014, 6, 13738‐13748.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(12) Ma, N.; Li, Y.; Xu, H.; Wang, Z.; Zhang, X., Dual redox responsive assemblies formed from diselenide block copolymers. J. Am. Chem. Soc. 2010, 132, 442‐443. (13) Cao, W.; Zhang, X.; Miao, X.; Yang, Z.; Xu, H., gamma‐Ray‐responsive supramolecular hydrogel based on a diselenide‐containing polymer and a peptide. Angew. Chem. Int. Ed. 2013, 52, 6233‐6237. (14) Kim, Y.; Mulay, S. V.; Choi, M.; Yu, S. B.; Jon, S.; Churchill, D. G., Exceptional time response, stability and selectivity in doubly‐activated phenyl selenium‐based glutathione‐selective platform. Chem. Sci. 2015, 6, 5435‐5439. (15) Cao, W.; Li, Y.; Yi, Y.; Ji, S. B.; Zeng, L. W.; Sun, Z. W.; Xu, H. P., Coordination‐responsive selenium‐containing polymer micelles for controlled drug release. Chem. Sci. 2012, 3, 3403‐3408. (16) Zeng, L.; Li, Y.; Li, T.; Cao, W.; Yi, Y.; Geng, W.; Sun, Z.; Xu, H., Selenium‐Platinum Coordination Compounds as Novel Anticancer Drugs: Selectively Killing Cancer Cells via a Reactive Oxygen Species (ROS)‐Mediated Apoptosis Route. Chem. Asian J. 2014, 9, 2295‐2302. (17) Li, T.; Smet, M.; Dehaen, W.; Xu, H., Selenium‐Platinum Coordination Dendrimers with Controlled Anti‐Cancer Activity. ACS Appl. Mater. Interfaces 2016, 8, 3609‐3614. (18) Wu, X.; Gao, Y.; Dong, C.‐M., Polymer/gold hybrid nanoparticles: from synthesis to cancer theranostic applications. RSC Adv. 2015, 5, 13787‐13796.


Page 22 of 28

Page 23 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(19) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J., A DNA‐based method for rationally assembling nanoparticles into macroscopic materials. Nature 1996, 382, 607‐609. (20) Ghosh, P.; Han, G.; De, M.; Kim, C. K.; Rotello, V. M., Gold nanoparticles in delivery applications. Adv. Drug. Deliv. Rev. 2008, 60, 1307‐1315. (21) Oh, H.; Green, P. F., Polymer chain dynamics and glass transition in athermal polymer/nanoparticle mixtures. Nature Mater. 2009, 8, 139‐143. (22) He, X.; Liu, H.; Li, Y.; Wang, S.; Li, Y.; Wang, N.; Xiao, J.; Xu, X.; Zhu, D., Gold Nanoparticle‐Based Fluorometric and Colorimetric Sensing of Copper(II) Ions. Adv. Mater. 2005, 17, 2811‐2815. (23) Daniel, M.‐C.; Astruc, D., Gold Nanoparticles: Assembly, Supramolecular Chemistry, Quantum‐Size‐Related Properties, and Applications toward Biology, Catalysis, and Nanotechnology. Chem. Rev. 2004, 104, 293‐346. (24) Giljohann, D. A.; Seferos, D. S.; Daniel, W. L.; Massich, M. D.; Patel, P. C.; Mirkin, C. A., Gold nanoparticles for biology and medicine. Angew. Chem. Int. Ed. 2010, 49, 3280‐3294. (25) MacLeod, M. J.; Johnson, J. A., PEGylated N‐Heterocyclic Carbene Anchors Designed To Stabilize Gold Nanoparticles in Biologically Relevant Media. J. Am. Chem. Soc. 2015, 137, 7974‐7977. (26) Pacardo, D. B.; Neupane, B.; Rikard, S. M.; Lu, Y.; Mo, R.; Mishra, S. R.; Tracy, J. B.; Wang, G.; Ligler, F. S.; Gu, Z., A dual wavelength‐activatable gold nanorod complex for synergistic cancer treatment. Nanoscale 2015, 7, 12096‐12103.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(27) Alkilany, A. M.; Murphy, C. J., Toxicity and cellular uptake of gold nanoparticles: what we have learned so far? J. Nanopart. Res. 2010, 12, 2313‐2333. (28) Pornpattananangkul, D.; Zhang, L.; Olson, S.; Aryal, S.; Obonyo, M.; Vecchio, K.; Huang, C. M.; Zhang, L., Bacterial toxin‐triggered drug release from gold nanoparticle‐stabilized liposomes for the treatment of bacterial infection. J. Am. Chem. Soc. 2011, 133, 4132‐4139. (29) Brust, M.; Walker, M.; Bethell, D.; Schiffrin, D. J.; Whyman, R., Synthesis of thiol‐derivatised gold nanoparticles in a two‐phase Liquid–Liquid system. J. Chem. Soc., Chem. Commun. 1994, 0, 801‐802. (30) Jana, N. R.; Gearheart, L.; Murphy, C. J., Seeding Growth for Size Control of 5−40 nm Diameter Gold Nanoparticles. Langmuir 2001, 17, 6782‐6786. (31) Jiang, L.; Tang, Y.; Liow, C.; Wu, J.; Sun, Y.; Jiang, Y.; Dong, Z.; Li, S.; Dravid, V. P.; Chen, X., Synthesis of fivefold stellate polyhedral gold nanoparticles with {110}‐facets via a seed‐mediated growth method. Small 2013, 9, 705‐710. (32) Uehara, A.; Booth, S. G.; Chang, S. Y.; Schroeder, S. L.; Imai, T.; Hashimoto, T.; Mosselmans, J. F.; Dryfe, R. A., Electrochemical Insight into the Brust‐Schiffrin Synthesis of Au Nanoparticles. J. Am. Chem. Soc. 2015, 137, 15135‐15144. (33) Kurashige, W.; Yamaguchi, M.; Nobusada, K.; Negishi, Y., Ligand‐Induced Stability of Gold Nanoclusters: Thiolate versus Selenolate. J. Phys. Chem. Lett. 2012, 3, 2649‐2652.


Page 24 of 28

Page 25 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(34) Li, T.; Yi, Y.; Xu, H., Selenium‐containing Coordinating Assemblies with Selective Anti‐cancer Activity: the Control of Reactive Oxygen Species. Acta Chim. Sin. 2014, 72, 1079‐1084. (35) Cai, K.; He, X.; Song, Z.; Yin, Q.; Zhang, Y.; Uckun, F. M.; Jiang, C.; Cheng, J., Dimeric drug polymeric nanoparticles with exceptionally high drug loading and quantitative loading efficiency. J. Am. Chem. Soc. 2015, 137, 3458‐3461. (36) Bastus, N. G.; Comenge, J.; Puntes, V., Kinetically controlled seeded growth synthesis of citrate‐stabilized gold nanoparticles of up to 200 nm: size focusing versus Ostwald ripening. Langmuir 2011, 27, 11098‐11105. (37) Hu, M. S.; Chen, H. L.; Shen, C. H.; Hong, L. S.; Huang, B. R.; Chen, K. H.; Chen, L. C., Photosensitive gold‐nanoparticle‐embedded dielectric nanowires. Nature Mater. 2006, 5, 102‐106. (38) Ni, Y.; Tong, G.; Wang, J.; Li, H.; Chen, F.; Yu, C.; Zhou, Y., One‐pot preparation of pomegranate‐like polydopamine stabilized small gold nanoparticles with superior stability for recyclable nanocatalysts. RSC Advances 2016, 6, 40698‐40705. (39) Patra, C. R.; Bhattacharya, R.; Mukhopadhyay, D.; Mukherjee, P., Fabrication of gold nanoparticles for targeted therapy in pancreatic cancer. Adv. Drug. Deliv. Rev. 2010, 62, 346‐361. (40) Mkandawire, M. M.; Lakatos, M.; Springer, A.; Clemens, A.; Appelhans, D.; Krause‐Buchholz, U.; Pompe, W.; Rodel, G.; Mkandawire, M., Induction of apoptosis in human cancer cells by targeting mitochondria with gold nanoparticles. Nanoscale 2015, 7, 10634‐10640.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(41) Zhou, X.; Cao, P.; Zhu, Y.; Lu, W.; Gu, N.; Mao, C., Phage‐mediated counting by the naked eye of miRNA molecules at attomolar concentrations in a Petri dish. Nature Mater. 2015, 14, 1058‐1064. (42) Walter, M.; Akola, J.; Lopez‐Acevedo, O.; Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Whetten, R. L.; Gronbeck, H.; Hakkinen, H., A unified view of ligand‐protected gold clusters as superatom complexes. Proc. Natl. Acad. Sci. USA 2008, 105, 9157‐9162. (43) Sousa, A. A.; Morgan, J. T.; Brown, P. H.; Adams, A.; Jayasekara, M. P.; Zhang, G.; Ackerson, C. J.; Kruhlak, M. J.; Leapman, R. D., Synthesis, characterization, and direct intracellular imaging of ultrasmall and uniform glutathione‐coated gold nanoparticles. Small 2012, 8, 2277‐2286. (44) Huang, K.; Ma, H.; Liu, J.; Huo, S.; Kumar, A.; Wei, T.; Zhang, X.; Jin, S.; Gan, Y.; Wang, P. C.; He, S.; Zhang, X.; Liang, X.‐J., Size‐Dependent Localization and Penetration of Ultrasmall Gold Nanoparticles in Cancer Cells, Multicellular Spheroids, and Tumors in Vivo. ACS Nano 2012, 6, 4483‐4493. (45) Yee, C. K.; Ulman, A.; Ruiz, J. D.; Parikh, A.; White, H.; Rafailovich, M., Alkyl Selenide‐ and Alkyl Thiolate‐Functionalized Gold Nanoparticles: Chain Packing and Bond Nature. Langmuir 2003, 19, 9450‐9458. (46) Zelakiewicz, B. S.; Yonezawa, T.; Tong, Y., Observation of selenium‐77 nuclear magnetic resonance in octaneselenol‐protected gold nanoparticles. J. Am. Chem. Soc. 2004, 126, 8112‐8113. (47) Li, Y.; Tian, H.; Xiao, C.; Ding, J.; Chen, X., Efficient recovery of precious metal based on Au–S bond and electrostatic interaction. Green Chem. 2014, 16, 4875‐4878.


Page 26 of 28

Page 27 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(48) Zaluzhna, O.; Li, Y.; Allison, T. C.; Tong, Y. J., Inverse‐micelle‐encapsulated water‐enabled bond breaking of dialkyl diselenide/disulfide: a critical step for synthesizing high‐quality gold nanoparticles. J. Am. Chem. Soc. 2012, 134, 17991‐17996. (49) Xu, Q.; Wang, S.; Liu, Z.; Xu, G.; Meng, X.; Zhu, M., Synthesis of selenolate‐protected Au18(SeC6H5)14 nanoclusters. Nanoscale 2013, 5, 1176‐1182. (50) Song, Y.; Wang, S.; Zhang, J.; Kang, X.; Chen, S.; Li, P.; Sheng, H.; Zhu, M., Crystal structure of selenolate‐protected Au24(SeR)20 nanocluster. J. Am. Chem. Soc. 2014, 136, 2963‐2965. (51) Connor, E. E.; Mwamuka, J.; Gole, A.; Murphy, C. J.; Wyatt, M. D., Gold nanoparticles are taken up by human cells but do not cause acute cytotoxicity. Small 2005, 1, 325‐327. (52) Pan, Y.; Neuss, S.; Leifert, A.; Fischler, M.; Wen, F.; Simon, U.; Schmid, G.; Brandau, W.; Jahnen‐Dechent, W., Size‐dependent cytotoxicity of gold nanoparticles. Small 2007, 3, 1941‐1949. (53) Pan, Y.; Leifert, A.; Ruau, D.; Neuss, S.; Bornemann, J.; Schmid, G.; Brandau, W.; Simon, U.; Jahnen‐Dechent, W., Gold nanoparticles of diameter 1.4 nm trigger necrosis by oxidative stress and mitochondrial damage. Small 2009, 5, 2067‐2076.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC:


Page 28 of 28

Selenium-Containing Amphiphiles Reduced and Stabilized Gold

Recommend Documents