Publication Date

12-2009

Advisor(s) - Committee Chair

Dr. Shivendra V. Sahi (Director), Dr. Linda Gonzales, Dr. Darwin Dahl

Degree Program

Department of Biology

Degree Type

Master of Science

Abstract

Manipulating matter at the nanoscale creates materials endowed with unique optoelectronic and physicochemical attributes. Among the noble metals, the properties of gold in "nano" can be manipulated by varying, their shapes and sizes. Gold nanoparticles find several applications in electronics, medicine and environmental reclamation. Emphasis has been on the “green synthesis” of nanogold to mitigate the hazardous implications stemmed from conventional nanogold synthesis. However, it is not known if the in planta synthesis of nanogold particles could be “green engineered” as well for generating desirable sizes and exotic shapes. In the present study, we used inductively coupled plasma (ICP) analysis to determine the species-specific variability, if any, in uptake of gold across taxonomically diverse plant species (alfalfa, cucumber, red clover, rye grass, sunflower, and oregano). Seedlings of these species were grown in half strength Hoagland’s solution supplemented with 100 ppm potassium tetrachloroaurate (KAuCl4) for 15d under controlled growth room conditions. Significant variations were detected in the ability of different plant species in accumulating gold in the root tissues ranging from 500 ppm (ryegrass) to 2500 ppm (alfalfa). Sunflower and oregano translocated significantly higher levels of gold into their aerial tissues compared to other species. This study thus suggested differential abilities of diverse plant species in uptake of gold by roots and its mobilization to aerial parts. For further elucidation of the effects of different growth variables on in planta synthesis of different shapes and sizes of nanogold particles, alfalfa was selected due to its ability to accumulate large quantities of gold in the root tissues. Further, alfalfa was subjected to KAuCl4 (50 ppm) treatment under variable growth conditions (duration of treatment, pH, temperature and light). Temporal analysis revealed that most of the nanogold particles formed within 6 h of treatment and majority fall within the size range of 10-30 nm. Spherical nanogold particles in the size range of 1-50 nm were detected ubiquitously across different treatments. Interestingly though, a noticeable shift was apparent towards the formation of nanogold particles of exotic shapes in response to specific treatments i.e., pH 3.8 (triangular), pH 7.8 (hexagonal), 15°C (rectangular). This study thus provides empirical evidence towards in planta “green engineering” of nanogold particles of exotic shapes and variable sizes. Efforts are now underway to decipher the mechanistic details governing the acquisition, synthesis and mobilization of nanogold particles in a model plant system. Furthermore, testing the efficacy of alternative non-lignified systems (callus and in vitro germinated pollen tubes) for nanogold particle production is of great interest in that in may be conducive for the extraction of nanogold particles.

Disciplines

Plant Sciences

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