Green synthesis of selenium nanoparticles for use as micronutrient supplements in food and cosmetics

Selenium (Se) is an essential trace element that the human body cannot synthesise on its own and therefore must be supplied through diet or nutritional supplements. Se forms part of the structural active centres of many antioxidant enzymes and functional proteins, playing an important role in maintaining immune system function, regulating thyroid hormone metabolism, inhibiting cancer progression, and supporting reproductive function through antioxidant mechanisms, hormone regulation and protection of reproductive cells. However, excessive Se supplementation can lead to many undesirable effects, even toxicity and death. Therefore, selecting an appropriate form of Se to optimise biological benefits while limiting adverse effects caused by overdose is an issue that requires attention. Compared with ionic Se, selenium nanoparticles (SeNP) show higher bioavailability, superior biological activity and lower toxicity.

The synthesis of metal nanoparticles in general, and SeNP in particular, can be carried out by various methods, including chemical, physical and biological approaches. While physical methods often require considerable time and energy, chemical methods involve many potentially hazardous chemicals and may produce undesirable by-products. Biological synthesis methods, particularly green synthesis using plant extracts as reducing agents, have attracted increasing attention thanks to their ability to produce nanoparticles with sizes ranging from 1–100 nm, high safety and potential for large-scale application. Plant extracts rich in polyphenols serve as effective sources of reducing agents, not only helping to reduce production costs and environmental impacts but also improving the quality, compatibility and stability of the resulting nanoparticles. Therefore, selecting suitable plant extracts is a key factor in green nanoparticle synthesis technology.

The technology development task coded UDPTCN03/23-25, led by Associate Professor, Dr Nguyen Thi Mai Phuong from the Institute of Biology, aims to synthesise SeNP through green methods for use as micronutrient supplements in food and cosmetics. The research used plant extracts rich in polyphenols with high antioxidant activity from Cleistocalyx operculatus L. leaves and Smilax glabra Roxb as reducing agents, either individually or in combination with electrochemical plasma. Two core technological processes for green synthesis of SeNP were developed, enabling the production of SeNP with selenium concentrations of 300–400 ppm, particle sizes ranging from 50–200 nm and synthesis efficiency of approximately 99%. The obtained SeNP showed good antioxidant and antibacterial activity and lower toxicity compared with SeNP synthesised using chemical methods, demonstrating potential as raw materials for food and cosmetic applications. After 36 months of implementation, the project achieved the following specific results:

- Development of a green synthesis process for SeNP (TPL+PLS) using extract from Smilax glabra roots (TPL) combined with electrochemical plasma (PLS), producing SeNP with a selenium concentration of approximately 400 ppm, particle size < 100 nm and synthesis efficiency of about 99%.

- Development of a green synthesis process for SeNP using Voi leaf extract, producing SeNP with a selenium concentration of approximately 300 ppm, particle sizes ranging from 50–200 nm and synthesis efficiency of about 99%.

- Evaluation of cytotoxicity and biological activities of the synthesised SeNP. Results showed that SeNP (TPL + PLS) exhibited no cytotoxicity at concentrations ≤ 200 mg/mL. The SeNP demonstrated inhibition of DPPH free radical formation (94% at a concentration of 125 µg/mL), inhibition of superoxide formation (88% at 125 µg/mL), and antibacterial activity against S. aureus, E. coli and the fungus C. albicans with inhibition zone diameters of 25, 25 and 27 mm respectively at a concentration of 0.2 mg/mL.

- Evaluation of acute toxicity (LD50) of the SeNP (TPL+PLS) preparation. The LD50 value was 7.5 mg/kg of mouse body weight, approximately three times lower than that of SeNP synthesised by chemical methods.

- Development of in-house standards for SeNP and preparation of documentation for raw material declaration to facilitate technology transfer.

- Publication of one scientific paper in the journal Nano-Structures & Nano-Objects, 38 (2024): 101185 (Scimago Q2, CiteScore 5.4).

- Grant of one invention patent No. 45654 by the Intellectual Property Office on February 27, 2025 for the “Process for synthesising selenium nanoparticles (SeNP) using Smilax glabra Roxb extract combined with electrochemical plasma”.

- Grant of one Utility Solution patent No. 4323 by the Intellectual Property Office on August 12, 2025 for the “Green synthesis process for selenium nanoparticles (SeNP) with antibacterial activity using Voi leaf extract (Cleistocalyx operculatus L.) as a reducing agent”.

Some images illustrating the project’s results:

SeNP solution and TEM image

UV spectrum and FTIR spectrum

Images of two intellectual property publications of the project

The project results contribute to proactive synthesis of SeNP through green synthesis processes using Cleistocalyx operculatus L. leaves extract or Smilax glabra root extract as reducing agents, offering a simple, safe and environmentally friendly approach and providing orientation for applications in food and cosmetics. The developed processes also make it possible to utilise Cleistocalyx operculatus L. leaves as a raw material source, enabling sustainable resource development combined with effective cultivation and harvesting, thereby bringing long-term economic and social benefits.

On December 30, 2025, the acceptance council of the Vietnam Academy of Science and Technology held a meeting to evaluate the task and rated it Excellent. The council also recommended that the research team continue proposing a second phase to further evaluate biological activities, stability and to refine the green synthesis processes for SeNP at a larger scale in order to facilitate technology transfer or commercialisation of the product.

Translated by Phuong Huyen
Link to Vietnamese version