Using algae for a more environmentally friendly way to produce functional gold nanoparticles

Osaka, Japan – Researchers from Japan have developed a novel, sustainable method for synthesizing functionalized gold nanoparticles (AuNPs) using microalgae. This “green” approach not only avoids the harsh chemicals used in traditional methods, but also produces AuNPs that are more stable and less toxic to healthy cells. The breakthrough promises a greener and more patient-friendly future for nanomedicine, including applications in photothermal cancer therapy, in line with the United Nations' Sustainable Development Goals (SDGs).

Gold nanoparticles are effective aids in medicine, especially for cancer treatment. In a technique called photothermal therapy, AuNPs are delivered to a tumor and heated with a laser. The localized heat destroys cancer cells without harming surrounding tissue. However, traditional chemical synthesis of these nanoparticles is often costly, energy-intensive and involves toxic substances, posing risks to both the environment and patient health. This has spurred the search for safer and more sustainable production methods.

The research team successfully used microalgae as a biological factory to produce AuNPs. The algae naturally produce compounds that reduce gold ions into stable nanoparticles and cover them with a protective organic layer. This biological process results in “Bio@AuNPs,” which have been compared to chemically synthesized “Chem@AuNPs.” The characterization showed that the algae-mediated gold nanoparticles were highly effective at absorbing laser light and converting it into heat, successfully inducing the death of cancer cells. Crucially, the Bio@AuNPs demonstrated high biocompatibility, maintained low cytotoxicity toward normal cells, and at the same time exhibited selective activity against cancer cells.

This work represents a dual benefit to society. First, it provides a sustainable and environmentally friendly manufacturing process for a high-quality medical material, reducing chemical waste and the ecological footprint of nanomedicine. Second, the improved biocompatibility and stability of these “green” nanoparticles could lead to the development of safer and more effective cancer therapies with fewer side effects for patients. This opens the door for broader clinical use of photothermal therapy as a viable, patient-friendly treatment option.

“Our goal is to find out how living organisms sense and respond to thermal fluctuations generated by the environment and their own biological processes at the cellular level,” says Professor Madoka Suzuki, senior author of the study. “Our recent success in developing an environmentally friendly, microalgae-based method for producing heat-releasing gold nanoparticles provides a new tool for studying cellular thermoregulation and advancing sustainable nanomedical technologies.”

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The article “Microalgae-Mediated Synthesis of Functionalized Gold Nanoparticles with High Photothermal Stability” was published in ACS Sustainable Chemistry and Technology at DOI: https://doi.org/10.1021/acssuschemeng.5c07786

About Osaka University

Osaka University was founded in 1931 as one of Japan's seven imperial universities and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a unique drive for innovation that spans the entire scientific process, from basic research to the creation of applied technology with positive economic impact. His commitment to innovation has been recognized in Japan and around the world. Now, Osaka University leverages its role as a Designated National University Corporation, selected by the Ministry of Education, Culture, Sports, Science and Technology, to contribute to innovation for people's well-being, sustainable development of society and social change.

Website: https://resou.osaka-u.ac.jp/en