| dc.description.abstract | Nature through billions of years of trial and error has produced an immeasurable amount of
natural systems like plants, birds and animals. The intelligence of nature is hidden in these
natural systems and researchers are turning towards “Nature’s intelligence” to find inspiration
and advance novelty in the development of nanomaterials. Gold nanoparticles (AuNPs) have
unique optical, electronic and physicochemical features which has gained them popularity and
widespread exploitation in various applications. The conventional methods used for AuNPs
synthesis employs toxic chemicals which makes these NPs unsafe for biomedical applications.
Hence, there is a search for new, ‘green’ and more cost effective methods for AuNPs synthesis.
Plant extracts are regarded as a highly desirable system for nanoparticle synthesis due to their
tremendous capability to produce a wide range of phytochemicals that can act as reducing
agents. The main goal of this study was to synthesize AuNPs in a cost effective manner without
the use of toxic chemicals in the synthesis process. Avocado seeds which are an agricultural
waste by-product were used for the biosynthesis of AuNPs. The study reports on the synthesis
optimization, characterization and activities of the biogenic AuNPs.
The avocado seed extract mediated - AuNPs (AvoSE-AuNPs) were optimized by varying
reaction parameters and characterized by UV-visible, Dynamic Light Scattering (DLS) and
High Resolution Transmission Electron Microscopy (HRTEM), Zetasizer and Fourier
Transform Infrared Spectroscopy (FTIR). The formation of AvoSE-AuNPs had an absorption
maximum at 534 nm. HRTEM and DLS confirmed that the NPs were polydispersed and present
in different shapes. The presence of phytochemical constituents on the AvoSE-AuNPs were
confirmed by FTIR. Their potential antibacterial activity was tested on bacterial strains known
to exhibit resistance to a number of current antibiotics. The catalytic activity of AvoSE-AuNPs
was also assessed as a means to contribute to the development of new methods aimed at
alleviating organic pollutants such as nitrophenols in the environment. The AvoSE-AuNPs
demonstrated excellent catalytic activity in the reduction of 4-NP by NaBH4 as shown by the
rapid decrease in the nitrophenolate absorption band at 400 nm and the appearance of new
absorption band at 298 nm, revealing the formation of the 4-aminophenol. Furthermore, the
rate constants calculated demonstrated that the reaction occurs faster in the presence AvoSEAuNPs. The AvoSE-AuNPs showed low significant cytotoxicity. Cell cycle analysis was
conducted to further investigate the apparent exhibited toxicity of the AvoSE-AuNPs. The
results showed that in both cell lines treated with AvoSE-AuNPs and AvoSE there was a
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disruption in the regulation of cell cycle. Cell cycle analysis helped improve understanding of
the low cytotoxicity observed by the MTT assay results.
The results presented in this study clearly demonstrate the feasibility of using AvoSE for the
synthesis of AuNPs. This study demonstrated that AvoSE mediated AuNPs synthesis is a
greener alternative as it abides by the green chemistry principles. Furthermore, the study
outcomes contributed to minimizing environmental pollution by finding use for agricultural
waste and thus ultimately adding value to the field. | en_US |
