當物質在奈米尺度下，其物理、化學與生物特性將不同於個別的原子、分子或塊材（bulk）所具有之原始特性與價值。其中奈米金粒子在近年來在醫藥科技（drug delivery）、生化感應器（bio-chemical sensors）、DNA標記（DNA labeling）、植物生長礦業（phytomining）、觸酶反應（catalysis）、比色技術（colorimetric technology）、環境修護（environmental remediation）、半導體（semi-conductors）科技、光電伏特（photovoltaic）等的發展皆扮演重要角色。
本研究利用活性植物體（live plants）的生物還原作用（bioreduction），在不添加任何複合劑（complexing agent）或營養劑的情況下，將小麥與苜蓿種子栽種於含有不同濃度的HAuCl4培養液中約14天，再以感應耦合電漿質譜儀分析植株根、莖、葉中的金含量，並配合掃瞄式電子顯微鏡觀察根部奈米金粒子的產狀與顆粒大小。本實驗培育出不具毒性可直接食用的小麥與苜蓿，作為未來開發具療效食材的基礎。
結果顯示苜蓿與小麥的根、莖、葉中，以根部對金具有最佳的吸收能力，且苜蓿吸收金的能力優於小麥。當HAuCl4培養液濃度增加時，苜蓿各部位組織的金含量也隨著增加，但培養液濃度到達100 ppm時，苜蓿即無法繼續生長。本研究發現的奈米金粒子主要分布於50 ppm與20 ppm含金培養液栽種的苜蓿根部中，共有三種產狀：突狀不規則顆粒、根部組織內、根毛表面上。
突狀組織內含金及以銅、矽及鈣為主成分之顆粒，其粒徑約＜500 nm，這些粒子可能以更細微的粒子為核，而逐漸聚集為較大的顆粒。根部組織內所觀察到的奈米金粒子推測可能在植株生長過程中運輸水分時，金粒子沉澱於運輸導管上所形成。而根部組織表面上的奈米金粒子可能因根部長時間與含金培養液接觸，使培養液中的金粒子沉澱於根部表面。

關鍵詞：奈米金、苜蓿、小麥、ICP-MS、SEM

The nano-sized particles have physical, chemical, and biological properties differ significantly from those with visually identifiable sizes. In recent nano-technology developments, nano-gold has been applied on drug delivery, bio-chemical sensors, DNA labeling, phytomining, catalysis, colorimetric technology, environmental remediation, semi-conductors, and photovoltaic. Therefore, the demands on nano-gold increase dramatically.
In this study, experiments were carried out to characterize the distribution and occurrence of nano-gold in live plants. Alfalfa and wheat were cultivated in solutions containing various concentrations of HAuCl4 without the addition of complexing agents and nutrients. After a cultivation period of 14 days, the plants were separated into root, stem, and leave parts for ICP-MS analysis to determine the concentration of gold. Then, the ones with high gold concentration were subjected to SEM observation for size and occurrence of gold particles. Being cultivated in a non-toxicity environment, products from these experiments have a potential to be used as “medical food”.
It is found that nano-gold is more abundant in alfalfa than in wheat. For both alfalfa and wheat, roots contain significantly higher nano-gold contents than stems, and leaves. The gold abundances in alfalfa and wheat increase with increasing HAuCl4 concentration in the cultivation solutions. However, alfalfa sprouting was prohibited in solutions with HAuCl4 concentration higher than 100 ppm.
Three types of nano-gold occurrence were observed in alfalfa roots: they are particles within protuberant and normal tissues and particles on the surface of fibrils. The nano-gold particles within the protuberant tissues are < 500 nm and contain trace amounts of Cu, Si, and Ca, which might be nuclides for the growth of nano-gold particles. The particles in the normal root tissues were possibly precipitated during transportation of gold solution in plants. It is inferred that the nano-gold particles on the fibrils were concentrated by adsorption since the fibrils were in contact with HAuCl4 solution during the whole course of cultivation.

Keywords: nano-gold, alfalfa, wheat, ICP-MS, SEM

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參考網站
United States Departments of Agriculture。http://plants.usda.gov/index.html
奈米科學網。http://nano.nchc.org.tw/main.php