Green synthesis of silver nanoparticles from marine microalgae Isochrysis sp. and Amphora sp. through Ayurvedic method / Tevan Ramanathan

Faculty of Industrial Sciences and Technology

Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2018

Includes bibliographical references

The majority of metal nanoparticles are chemically synthesised, this is an environmentally risky, costly process and the produced nanoparticles are potentially toxic for biomedical and pharmacological applications. Therefore, green synthesis of metal nanoparticles is an interesting topic to explore. The study aims to identify and characterize marine microalgae species from Pantai Teluk Cempedak, Kuantan coastal region; biosynthesize and characterize silver nanoparticles (AgNPs) using Isochrysis sp. and Amphora sp. and finally determine the anticancer potential of synthesized AgNPs against human non-small cell lung carcinoma (NCL-H1299). Ayurvedic method was employed in this study to synthesize AgNPs. Physio-chemical properties were characterized by various analytical techniques such as UV-Vis spectrophotometer analysis, field emission scanning electron microscope (FESEM), energy-dispersive Xray spectroscopy (EDX), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Further, antibacterial, antioxidant and anticancer potential of synthesised silver nanoparticles were investigated. As a result, nine species of marine microalgae were successfully identified and characterized, namely Coelastrum sp., Chlorococcum sp., Chlamydomonas moewusii, Scenedesmus sp., Nannochloropsis sp., Pavlova sp., Isochrysis sp., Amphiprora paludosa and Amphora sp. Out of nine species Isochrysis sp. and Amphora sp., were selected as potential species to synthesize AgNPs. The synthesized AgNPs were monodispersed and spherical in shape. The size was 98 to 193 nm for Isochrysis sp. and 42.2 to 50.8 nm for Amphora sp. Since microalgae is rich with secondary metabolites, reduction and stabilization of Ag+ ions to Ag° ions took place in room temperature within 3 hours. On the other hand, synthesized AgNPs were successfully inhibited the growth of Gram-negative bacteria Escherichia coli and Proteus vulgaris; Gram-positive bacteria Enterococcus faecalis and Bacillus subtilis. Furthermore, antioxidant activity of AgNPs was found to increase in a dose dependent manner. In addition, AgNPs have shown a reduction in cell viability and an increase in cytotoxicity on human non-small cell lung carcinoma (NCL-H1299). The cytotoxicity effects were observed to be significant from the concentration of 100 μg/ml AgNPs. Finally, the MRNA gene expression revealed that Isochrysis sp. and Amphora sp. Arishtas derived nanoparticles were able to induce the pro-apoptotic genes. Overall, these findings proved that the microalgae arishtas successfully synthesised AgNPs which acts as potent antibacterial, antioxidant and anticancer substances.