Date of Award
Doctor of Philosophy
William R. Hamel, Wei He, Ramón V. León, Siqun Wang
Green nanoscience is a rapidly emerging field that aims to achieve the maximum performance and benefits from nanotechnology, while minimizing the impact on the environment. In this study, several methods for the green nanomanufacturing of biomedically important nanomaterials, specifically through the use of natural plants, have been extensively investigated. It was found that natural nanomaterials are inherent within plants, and can be further manipulated for potential biomedical applications. In addition, the metabolites and reductive capacity of plant extracts can be used to synthesize metallic nanoparticles with advantages over semi-conductor based nanomaterials. Nanoparticles were found to exist in the extracts produced from tea leaves, the adventitious roots of English ivy (Hedera helix), the adhesive of the sundew (Drosera sp.), and the rhizome of the Chinese yam (Dioscoera opposite). These nanoparticles showed highly uniform repeating structures varying in size from 50-200 nm. Plant-derived nanofibers were also observed in the traditional Chinese medicine, Yunnan Baiyao, and from the polysaccharide components of the sundew adhesive and the viscous pulp extract from the Chinese yam. The nanofibers observed from the dried polysaccharides of the sundew and Chinese yam formed network structures with various pore sizes and fiber diameters. Due to their organic backbone, advantageous material properties, and biocompatibility, these natural nanomaterials offer significant advantages for biomedical applications. As such, these natural nanomaterials were further tested from medical prospects. Ivy nanoparticles were found to have unique optical property, blocking the transmission of ultraviolet light, which has potential for sunscreen and cosmetic applications. Nanofiber networks created from the sundew and Chinese yam showed strong cell attachment and proliferation with multiple cell lines, indicating their potential use as coatings for implants in the field of tissue engineering. Finally, gold and silver nanoparticles were synthesized using the extracts from homogenized ivy rootlets, by live sundew plant, or by herbicide additive. Through this study, the potential of plants has been demonstrated to vastly expand the current field of nanomanufacturing, and to reduce the environmental concerns associated with synthetic nanomaterials.
Xia, Lijin, "Characteristics and Functionalities of Natural and Bioinspired Nanomaterials. " PhD diss., University of Tennessee, 2012.