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 
©2020 Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute 
Study on the preparation of selenium nanoparticles by gamma 
Co-60 method and investigate the stability 
Ngoc Duy Nguyen
1
, Van Phu Dang
1
, Anh Quoc Le
1
, T. Kim Lan Nguyen
1
, 
Quoc Hien Nguyen
1
, T. Thu Ngan Tran
2
1
Research and Development Center for Radiation Technology, 
202A, Street 11, Thu Duc District, Ho Chi Minh City, Vietnam 
2
University 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. 
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 
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 
LD50 for SeNPs for Kunming mice was 258.2 
mg/kg while the LD50 for H2SeO3 was 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 
 NGUYEN NGOC DUY et al. 
27 
fight lung cancer [7]. Faghfuri et al. [8] 
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 LD50 of SeNPs for 
Kunming mice was 258.2 mg/kg while the 
LD50 for H2SeO3 was 22 mg/kg. 
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. 
II. CONTENT 
A. Subjects and methods 
1. Chemicals 
Selenium dioxide (SeO2) was of pure 
product of Merck, Germany. OC solution is a 
product of the Research and Development 
Center for Radiation Technology 
(VINAGAMMA) with the concentration of 
3%, deacetyl ~ 85% and Mw~ 5000 g/mol. 
Other chemicals were of pure grade. Distilled 
water was used throughout the experiments. 
2. Preparation of SeNPs/OC by γ-irradiation 
A required amount of SeO2 was 
dissolved in 1% (w/v) OC solution to prepare 
selenous acid (H2SeO3) solution (eq. (1)) with 
concentration of 2.5 mM. 
SeO2(s) + H2O(l) → H2SeO3(aq) (1) 
Irradiation of SeO3
2-
/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. 
B. Results 
1. Characteristics of SeNPs /OC solution 
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 
STUDY ON THE PREPARATION OF SELENIUM NANOPARTICLES BY GAMMA CO-60  
28 
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 
2. Stability of SeNPs/OC solution with 
storage time 
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. 
TEM images and the size distribution of 
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. 
Fig. 2. Color change of SeNPs / OC solution stored at 4ºC (A) and 27ºC (B) for 0 to 60 days 
 NGUYEN NGOC DUY et al. 
29 
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 Se
4+
 to 
Se
0
. However, the UV-Vis spectrum of SeNPs 
did not have typical adsorption peaks like other 
metallic nano such as silver (λmax ~ 400-500 
STUDY ON THE PREPARATION OF SELENIUM NANOPARTICLES BY GAMMA CO-60  
30 
nm) nad gold (λmax ~ 520-570 nm). According 
to Lin and Wang [11], the SeNPs with 
diameter less than 100 nm do not have 
characteristic absorption peak (λmax) 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. 
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 
The increasing size of SeNPs during 
storage time can be explained by increasing the 
Brownian motion when the SeNPs solution 
was stored at different temperatures. This 
results were also reported by Lin and Wang et 
al. [11]. From the above results, it can be seen 
that the appropriate temperature to store 
SeNPs/OC solution was 4
o
C. However, 
SeNPs/OC solution is not always convenient 
to transport and apply. To overcome the 
limitation above as well as expand the scope 
of application, SeNPs in powder have been 
formed. Results from Fig 5 showed that 
SeNPs/OC powder prepared by spray drying 
technique from SeNPs/OC solution 
synthesized by gamma Co-60 ray irradiation 
was of high purity with composition only of 
SeNPs and OC. 
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
o
C. 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. 
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