Study on the preparation of selenium nanoparticles by gamma Co-60 method and investigate the stability

Nuclear Science and Technology, Vol.10, No. 2 (2020), pp. 26-31

Study on the preparation of selenium nanoparticles by gamma

Co-60 method and investigate the stability

Ngoc Duy Nguyen¹, Van Phu Dang¹, Anh Quoc Le¹, T. Kim Lan Nguyen¹,

Quoc Hien Nguyen¹, T. Thu Ngan Tran²

¹Research and Development Center for Radiation Technology,

202A, Street 11, Thu Duc District, Ho Chi Minh City, Vietnam

²University of Science, VNU-HCM, 227 Nguyen Van Cu, District 5, Ho Chi Minh City, Vietnam

Email: ngocduy158@gmail.com

(Received 26 November 2019, accepted 31 March 2020)

Abstract: Among nanoparticle materials, selenium nanoparticles (SeNPs) have attracted wide spread

attention due to their excellent bioavailability, high bioactivity and low toxicity compared to other

ionic selenium compounds. SeNPs with size ~ 41.75 nm were synthesized by γ-irradiation method

using oligochitosan (OC) as stabilizer. The prepared SeNPs/OC were characterized by UV-Vis

spectroscopy and transmission electron microscope (TEM) images. The SeNPs/OC powder was also

prepared by spray drying technique and the purity was verified by energy dispersive X-ray (EDX)

analysis. The results of EDX showed that SeNPs/OC solution was of high purity. The stability of

SeNPs/OC solution was investigated. The results indicated that SeNPs/OC solution had good stability

after 60 days of storage at 4ºC. At ambient temperature, the SeNPs/OC solution was unstable and

agglomerated after about 15 days. The SeNPs/OC synthesized by γ-irradiation with the advantages of

environmental friendly and mass production process may be potentially promising for applications in

medicines, functional food and in other fields as well.

Keywords: Selenium nanoparticles, γ-irradiation, oligochitosan.

content in the diet of adults is 50 - 200 μg/day

[2]. Compared to selenium in ionic form,

SeNPs have higher bioavailability and lower

toxicity [3]. Result of the previous studies

showed that SeNPs have a much lower acute

toxicity in mice with LD₅₀~ 91.2 mg Se/kg

body weight compared to methylselenocysteine

with LD₅₀~ 14.6 mg Se/kg body weight [4].

Recently, Zhai et al. [5] also reported that the

LD₅₀for SeNPs for Kunming mice was 258.2

mg/kg while the LD₅₀for H₂SeO₃was 22

mg/kg. In addition, studies have shown that

SeNPs were effective in treating cancer.

Sonkusre et al. [6] have demonstrated that

SeNPs were highly effective and specific

against prostate cancer. Ali et al. found that

mice supplemented SeNPs (50 - 80 nm) at a

dose of 0.2 mg/kg body weight were able to

I. INTRODUCTION

Cancer is now the leading cause of death

worldwide. According to estimation by the

World Cancer Research Agency (IARC), there

were 14.1 million new cancer cases and 8.2

million deaths in 2012. Radiotherapy and

chemotherapy are still considered to be the

most optimal measures, but they also cause

many unwanted side effects such as the

severely reduced number of blood cells, which

can cause anemia and infection with

opportunistic microorganisms caused by the

weakened immune system [1]. Selenium is an

important trace element, which has broad

effects on biological systems, including

antioxidant effect, cancer prevention and

antiviral activitiy [8]. The necessary selenium

NGUYEN NGOC DUY et al.

fight lung cancer [7]. Faghfuri et al. [8]

3%, deacetyl ~ 85% and Mw~ 5000 g/mol.

Other chemicals were of pure grade. Distilled

water was used throughout the experiments.

reported that breast tumor in mice

supplemented with 200 μg SeNPs/day for 60

days was smaller than the control group that

did not use SeNPs. Recently, Zhai et al. [6]

also reported that the LD₅₀of SeNPs for

Kunming mice was 258.2 mg/kg while the

LD₅₀for H₂SeO₃was 22 mg/kg.

2. Preparation of SeNPs/OC by γ-irradiation

A required amount of SeO₂was

dissolved in 1% (w/v) OC solution to prepare

selenous acid (H₂SeO₃) solution (eq. (1)) with

concentration of 2.5 mM.

Several methods have been applied to

synthesize SeNPs from Se ions such as

chemical reduction methods using ascorbic

acid, glutathione, hydrazine hydrate, etc. as

reducing agents [3, 4], biological methods.

using bacterial biomass as a reducing agent

[7, 8], the gamma Co-60 irradiation method

used sodium dodecyl sulfate as a stabilizer

and ethanol as a free radical capture agent [9,

10]. In particular, irradiation method is

considered as an effective method to

synthesize SeNPs with advantages such as:

(1) the reaction is performed at room

temperature, (2) the efficiency of creating

high SeNPs, (3) SeNPs are of high purity due

to the absence of reductant residues, (4)

easily adjust SeNPs particle size by changing

the dose and dose rate, (5) capable of

producing in large quantities [9, 10]. In this

study, SeNPs were synthesized by gamma

Co-60 irradiation method using OC as a

stabilizer. The stability of SeNPs/OC

solution during storage was investigated.

SeO₂(s) + H₂O(l) → H₂SeO₃(aq)

(1)

2-

Irradiation of SeO₃/OC solutions to

synthesize SeNPs was carried out on a Gamma

Co-60 SVST at VINAGAMMA at dose of 20

kGy, with the dose rate of 1.3 kGy/h measured

by a dichromate dosimetry system [10].

3. Characterization and stability of SeNPs/OC

The absorption spectra of OC and the

resulted SeNPs/OC solutions were taken on an

UV-Vis spectrophotometer model UV-2401PC

(Shimadzu, Japan). The size and size

distribution of the SeNPs were characterized

by TEM images on transmission electron

microscope (TEM), model JEM1010 (JEOL,

Japan) and statistically calculated from about

300 particles [10]. The SeNPs/OC powder was

prepared by spray drying of 2.5 mM SeNPs/1%

OC solution with spray dryer model ADL311

(Yamato, Japan). The content of selenium in

SeNPs/OC powder was assessed by energy

dispersive X-ray (EDX) spectroscopy on a

JEOL 6610 LA. The stability of SeNPs/OC

solution determined by changes in particle size

with storage time.

II. CONTENT

A. Subjects and methods

B. Results

1. Chemicals

1. Characteristics of SeNPs /OC solution

Selenium dioxide (SeO₂) was of pure

product of Merck, Germany. OC solution is a

product of the Research and Development

Nano selenium was prepared by the

gamma-Co-60 irradiation method with a dose

of 20 kGy, using 2% OC as a stabilizer

according to Hien et al. [10]. The UV-Vis

Center

for

Radiation

Technology

(VINAGAMMA) with the concentration of

27

STUDY ON THE PREPARATION OF SELENIUM NANOPARTICLES BY GAMMA CO-60 …

spectra of OC, ion selenium and SeNPs/OC

solutions, the color of the solution and the

TEM image are shown in Figure 1. After

irradiating, the color of H₂SeO₃/OC solution

turned from yellow orange to orange-red color

that indicated the formation of SeNPs [10].

Fig. 1. UV-Vis spectra of OC, ion selenium and SeNPs/OC solutions

and TEM image, size distribution of SeNPs/OC solution

TEM images and the size distribution of

2. Stability of SeNPs/OC solution with

storage time

SeNPs/OC solution in Fig. 3 showed that SeNPs

are spherical morphology with average diameter

calculated to be of 41.75, 50.91, and 51.92 nm

for different storage time (0, 30, and 45 days) at

4°C, respectively. At 27 °C, SeNPs particle size

increased faster than that stored at 4°C. SeNPs

particle size increased from 41.75 nm (0 days)

to 115.09 and 125.75 nm, respectively, storage

time of 30 days and 45 day (Fig 4). On the 45th

day, the sample was coagulated and could not

determine the particle size.

The change of color of SeNPs/OC

solution during storage presented in Fig. 2.

Results showed that at low temperatures (4°C)

the color of SeNPs/OC solution remained

almost unchanged over a 60-day period.

Meanwhile, at 27°C, the color of the solution

changes markedly from light yellow to dark

orange and coagulation happen after 25 days

of storage.

Fig. 2. Color change of SeNPs / OC solution stored at 4ºC (A) and 27ºC (B) for 0 to 60 days

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NGUYEN NGOC DUY et al.

Fig. 3. TEM image and size distribution of SeNPs / OC stored at 4ºC at different time: 0 days (A, a); 30 days

(B, b) and 45 days (C, c)

Fig. 4. TEM image and size distribution of SeNPs / OC stored at 27ºC at different time: 0 days (A, a); 15

days (B, b); 30 days (C, c) and 45 days (D)

3. SeNPs/OC in powder was formed by spray drying method

Fig. 5. (A) SeNPs/OC solution, (B) SeNPs/OC powder and EDX spectrum of SeNPs/OC

The photograph and the EDX spectrum

of SeNPs/OC powder prepared by spray drying

technique were presented in Fig. 5. The results

from spectrum indicated that the SeNPs/OC

powder contained only three elements namely

selenium (2.51%), carbon (78.67%) and

oxygen (18.82%).

C. Discussion

The formation of SeNPs is due to water

radiolysis products (e^-, H^●) to reduce Se⁴⁺to

Se⁰. However, the UV-Vis spectrum of SeNPs

did not have typical adsorption peaks like other

metallic nano such as silver (λ_max~ 400-500

29

STUDY ON THE PREPARATION OF SELENIUM NANOPARTICLES BY GAMMA CO-60 …

nm) nad gold (λ_max~ 520-570 nm). According

to Lin and Wang [11], the SeNPs with

diameter less than 100 nm do not have

characteristic absorption peak (λ_max) in the

UV-Vis region (200-800 nm). TEM images

and the size distribution of SeNPs in Fig. 1

(A, a) showed that SeNPs are spherical

morphology with average diameter calculated

to be of 41.75 nm.

III. CONCLUSIONS

SeNPs with concentration of 2.5 mM and

diameter of ~42 nm stabilized in 2% OC

solution were successfully synthesized by

gamma Co-60 ray irradiation method. The

appropriate temperature to store SeNPs/OC

solution was 4^oC. SeNPs/OC powder with high

purity was also prepared from SeNPs/dextran

solution by spray drying technique. SeNPs/OC

powder is potentially promising for use in

injection or in oral administration for cancer

therapy and for other purposes of application

as well.

The SeNPs after being formed will be

stabilized by OC. Like other polysaccharides

as alginate, dextran, gelatin, etc. OC has

electron-rich functional groups such as –NH₂, -

OH groups that will stabilize SeNPs through

coordinate bond and electrostatic repulsion.

There are several factors that affect the

stability of SeNPs solution such as H₂SeO₃

concentration, pH, stabilizer concentration, etc.

[10, 11]. In particular, the temperature greatly

affects the stability as well as the properties of

SeNPs/OC solution

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