Characterization of Silver Nanoparticle Systems from Microalgae Acclimated to Different CO₂ Atmospheres

Abstract

Green synthesis of metallic nanoparticles using microalgae exposed to high CO 2 atmospheres has not been studied in detail; this is of relevance in biological CO 2 mitigation systems where considerable biomass is produced. In this study, we further characterized the potential of an environmental isolate Desmodesmus abundans acclimated to low and high CO 2 atmospheres [low carbon acclimation (LCA) and high carbon acclimation (HCA) strains, respectively] as a platform for silver nanoparticle (AgNP) synthesis. As previously characterized, cell pellets at pH 11 were selected from the biological components tested of the different microalgae, which included the culture collection strain Spirulina platensis. AgNP characterization showed superior performance of strain HCA components as preserving the supernatant resulted in synthesis in all pH conditions. Size distribution analysis evidenced strain HCA cell pellet platform (pH 11) as the most homogeneous AgNP population (14.9 ± 6.4 nm diameter, −32.7 ± 5.3 mV) followed by S. platensis (18.3 ± 7.5 nm, −33.9 ± 2.4 mV). In contrast, strain LCA presented a broader population where the size was above 100 nm (127.8 ± 14.8 nm, −26.7 ± 2.4 mV). Fourier-transform infrared and Raman spectroscopies showed that the reducing power of microalgae might be attributed to functional groups in the cell pellet from proteins, carbohydrates, and fatty acids and, in the supernatant, from amino acids, monosaccharides, disaccharides, and polysaccharides. Microalgae AgNPs exhibited similar antimicrobial properties in the agar diffusion test against Escherichia coli. However, they were not effective against Gram (+) Lactobacillus plantarum. It is suggested that a high CO 2 atmosphere potentiates components in the D. abundans strain HCA for nanotechnology applications.

Comparative Study of Physicochemical Properties and Antibacterial Potential of Cyanobacteria Spirulina platensis-Derived and Chemically Synthesized Silver Nanoparticles

“…The strongest reflection from the (111) diffraction peak indicates a face-centered cubic structure of NPs with a lattice constant of a = 4.0861 Å. The XRD pattern suggests that the biosynthesized NPs are well crystallized. , …”

“…Microalgae are widely used in biotechnology owing to their ability to produce a large number of bioactive compounds. − Several studies reported the biosynthesis of NPs by distinct microalgae and their inhibitory effect on pathogens. ,,− In this way, AgNPs produced by using the extracts of cyanobacteria Oscillatoria sp. not only exhibited antibacterial and antibiofilm activity against various pathogens but also demonstrated cytotoxicity against some human breast and colon cancer cell lines. , Singh and co-workers reported Dunaliella-mediated synthesis of AgNPs with anticancer activity comparable to that of the Cisplatin drug …”

“…To overcome these threats, eco-friendly and sustainable pathways to synthesize NPs have been implemented. Green technological approaches are favorable since green-synthesized NPs are more robust and nonhazardous than chemically synthesized ones. − The utilization of naturally derived biodegradable substances lowers ecological consequences and the cost of technology. − Although the biological production of metal NPs is a relatively new research field and till now not been investigated in detail, the “green synthesis” has already enabled the production of stable NPs of various shapes and sizes. − Moreover, green synthesized NPs are endowed with various biological activities and have a high potential for application in various fields of biomedicine and biotechnology. − Recently, biosynthesis of NPs and their antimicrobial potential have been reported using extracts of Royal Jelly, various plants such as Stevia rebaudiana, Crataegus microphylla, Artemisia herba-alba, Mentha, Rosmarinus, lichen Protoparmeliopsis muralis, and green algae Desmodesmus abundans and Dunaliella salina. − ,− …”

“… 22 − 25 Several studies reported the biosynthesis of NPs by distinct microalgae and their inhibitory effect on pathogens. 20 , 21 , 26 − 30 In this way, AgNPs produced by using the extracts of cyanobacteria Oscillatoria sp. not only exhibited antibacterial and antibiofilm activity against various pathogens but also demonstrated cytotoxicity against some human breast and colon cancer cell lines.…”