Microalgae-Derived Metal Nanostructures: Biosynthesis, Characterization, and Applications

The exploration of green chemistry approaches for novel nanoparticles derived from microalgae presents a promising frontier in the realm of biomedical applications, harnessing the unique properties of these microorganisms for innovative solutions in healthcare. Microalgae, mainly due to their rapid growth rates and ability to synthesize diverse bioactive compounds, have become an environmentally friendly, green chemistry method to produce nanoparticles, overcoming current toxic chemical approaches. This review study aims to clarify the processes that underlie the biosynthesis of different microalgal species' nanoparticles and the following biomedical uses. The study investigates the manufacturing of copper, gold, iron, and silver nanoparticles and the optimization of other parameters, including pH and metal ion concentration. Characterization techniques such as UV-Vis spectroscopy, FTIR, TEM, and XRD revealed particle sizes ranging from 2 to 149 nm with distinct crystalline structures. Notably, microalgae-derived silver nanoparticles exhibited strong antioxidant activity (e.g., 77.01% DPPH and 88.12% ABTS scavenging at 500 µg mL^-1), potent antibacterial action (minimum inhibitory concentrations as low as 5 μg mL^-1 for Escherichia coli), and selective cytotoxicity against cancer cell lines (IC50 values: 25-30 µg mL^-1 for HeLa and MCF-7; as low as 0.16 μg mL^-1 for MCF7). These nanoparticles also demonstrated high biocompatibility, with minimal toxicity to normal human cells at effective concentrations. Overall, this study emphasizes how crucial it is to conduct further studies in this area to create safe and efficient nanomaterials for use in medical applications.