Using Marine Algae for Nanoparticle Synthesis

Written By Sofia Perez

Fig. 1 Seaweed is a kind of macroalgae frequently found on coasts. Lyn Ong; photographic print; Source: Pexels

“We sometimes underestimate the influence of little things,” said Charles W. Chestnutt, the African-American author, essayist, political activist, and lawyer. Clearly, he was one of those rather prescient clairvoyants who believed in the magic of marine algae even before the field of nanotechnology first blossomed into the orchard of scientific discovery. 

Chestnutt knew that one day the underappreciated forests of seaweed and invisibly small phytoplankton with only a meager cell to call their own would finally find their place in our hearts, laboratories, medicine, and cosmetics. 

From the perspective of a creature living on an ever-so-slightly larger scale than phytoplankton, it is difficult to truly comprehend how much life you can find in just a cup of seawater. Nevertheless, if you need to see it to believe it, you might even take the example of a piece of slimy olive-green seaweed. It too is an alga, albeit ‘macro’ rather than ‘micro’. 

Yet while the word ‘algae’ might evoke disgust or be commonly thought of as something to be washed away, marine algae can range anywhere from the silica-shelled diatoms, which generate approximately 20-50% of the oxygen produced on the planet each year, to the red algae Pyropia which is used to wrap rolls of sushi and is commonly known as Nori.

Fig. 2 The red algae Pyropia, commonly known as Nori, is a prevalent part of Japanese cuisine. Emy; photographic print; Source: Unsplash

While nanotechnology is not the beginning of marine algae’s success story, it is definitely a noteworthy achievement in its vast hall of fame. Of course, nanotechnology is another one of those ‘little things’ with a big influence that makes those with an appreciation for irony chuckle. In fact, a nanoparticle can be sized anywhere between 1-100nm in diameter, which is approximately a thousand times smaller than a speck of dust. Due to their high surface area to volume ratio and their submicroscopic size, nanoparticles have been applied everywhere, from UV filters in cosmetics to targeted drug delivery.   

Traditionally (if you can call a technology introduced in the 80s ‘traditional’), nanoparticles have been synthesized by either a top-down approach, taking a big piece of material and breaking it down, or a bottom-up approach, taking a molecule or simple salt and performing chemical reactions to build them up atom-by-atom. Most of these methods lead to a high cost of production, high energy input, and the production of toxic byproducts. However, for an industry with such promise, it is critical that a better method of synthesis be established. Nonetheless, as everyone learns sooner or later, the orchard of scientific discovery has a way of giving answers in the form of an ever-longer list of questions. Now, instead of ‘what’ and ‘why’, the question is ‘how’ and ‘when’. The ‘how’: marine algae. The ‘when’: now.

Fig. 3 Algae offer a solution to creating a more environmentally-friendly and cheaper alternative to nanoparticle synthesis. 2019 Source: Royal Society of Chemistry!divAbstract

Now, considering the vast influence algae already has on our modern way of life, and in fact, on the existence of life at all, is it at all surprising that it has also managed to take hold of the world of nanotechnology? Once again, as the wise Charles Chestnutt has already established, “We sometimes underestimate the influence of little things.”

Sargassum muticum, a species of brown seaweed commonly known as Japanese wireweed, has been used in the synthesis of gold and silver nanoparticles, and diatoms such as Navicula atomus and Diadesmis gallica have been used in the synthesis of gold nanoparticles and silica-gold nanocomposites. To synthesise silver nanoparticles, which are the most widely used antimicrobial agent against bacteria, fungi, & viruses, Lynbyga majuscule, Spirulina platensis, and Chlorella vulgaris have been used. 

The reason for this success is the impressive ability of algae to accumulate and add electrons to metal ions on the cell surface using biomolecules. These molecules speed up the reduction of metal salts into metal or metal oxide nanoparticles, which can then be used in industry. This mechanism has yet to be fully understood by researchers but has offered a cost-effective, nontoxic, eco-friendly alternative to the typical methods. 

In fact, beyond the use of marine algae, nanoparticles can even be made from food waste such as mango peels (gold nanoparticles), grapes (silver nanoparticles), orange peels (silver nanoparticles), and chicken eggshells (fluorescent gold nanoparticles). It is also believed that coffee waste water, domestic waste (e.g. Cardboard, yard clippings, wood, etc.), agricultural waste, and biodegradable waste could be employed.

In truth, there is still much to be discovered in the vast unknown of the nanoparticle-verse, much as there is to be discovered about the wonders of algae itself. However, on the path to more environmentally and economically sustainable alternatives to traditional methods of nanoparticle synthesis, it will certainly be the case that such ‘little things’ will only continue to astound us.  


Featured Photo: Bakir, E. M., N. S. Younis, M. E. Mohamed, N. A. El Semary. 2018. “Cyanobacteria as Nanogold Factories: Chemical and Anti-Myocardial Infarction Properties of Gold Nanoparticles Synthesized by Lyngbya majuscula”. Marine Drugs 16(6):217.

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