SCIENTISTS from the University of the Philippines Diliman have developed a greener approach to producing silver nanoparticles for antibacterial applications by combining gamma irradiation with a natural seaweed-derived biopolymer, ι-carrageenan.
The study advances existing gamma-radiolytic methods for silver nanoparticle synthesis by examining the specific role of ι-carrageenan in stabilizing and influencing nanoparticle formation during radiolysis—an area that has remained largely underexplored.
Colloidal silver nanoparticles produced using gamma irradiation at varying doses showed a visible color change from colorless to yellow and brown as silver ions were converted into antibacterial silver nanoparticles. Darker colors indicated higher nanoparticle concentrations.
The research was conducted by Mon Bryan Gili, Wendell Manuel, and Dr. Marienette Vega of the UP Diliman College of Science Materials Science and Engineering Program; Dr. Marlon Conato of the Institute of Chemistry; and Rakshith Gowda Shankaregowda and Dr. Manh-Huong Phan of the University of South Florida.
Instead of relying on harsh chemical agents, the team used gamma radiation alongside carrageenan, a naturally occurring substance derived from seaweed, to form the nanoparticles.
“In simple terms, we let radiation do the work of forming the particles, while the seaweed extract keeps them stable and safe,” Gili said. “We then tested how effective these particles are against common bacteria.”
Compared to traditional chemical synthesis, the method offers environmental advantages. Conventional approaches often require strong reducing agents and stabilizers that can be toxic and difficult to dispose of safely. In the radiolytic process, gamma radiation fully replaces these chemicals while also sterilizing the nanoparticles during formation—an important advantage for medical applications.
“Overall, this means fewer processing steps, less chemical waste, and a safer product for both people and the environment,” Gili added.
Gili said his background in nuclear science motivated him to explore applications of radiation technology that directly benefit health and sustainability. Environmental safety concerns and the growing problem of antibiotic resistance also influenced the team’s work, as many existing methods rely on chemicals that can harm both people and ecosystems.
“The next steps include improving long-term stability, testing the nanoparticles in real-world products, and evaluating their safety for human use,” Gili said. “Ultimately, we hope this technology can lead to affordable, locally produced antibacterial materials using Philippine natural resources and nuclear science expertise.”
The study, titled “Antibacterial evaluation of radiolytically synthesized silver nanoparticles with ι-carrageenan stabilizers,” was published in Radiation Physics and Chemistry, a peer-reviewed journal focusing on research involving ionizing radiation in physics, chemistry and radiation processing.