Tadpoles and Gold Are a Good Combination

Hi, my name is Kevin Lerner and I am a rising junior Biochemistry and Molecular Biology major working in Dr. Thompson’s lab this summer. My work is a continuation of the Tadpole Project carried out by Laura Lee in the summer of 2014 and other student researchers prior to her. In its essence, my research and previous research has been aimed at quantifying the effects of nanoparticles on a biological system, which is increasingly essential due to the increase of nanoparticles in the consumer marketplace. Yes, this does mean that nanoparticles exist in everyday products that you wouldn’t imagine them to be! They can be in your clothes, make-up, and sunscreen among thousands of other products, usually due to the unique physical properties nanoparticles can have versus the properties of the bulk material from which they come.

An example of the uniqueness of nanoparticles can be seen in the nanoparticles that we use in our lab, gold nanoparticles! What is interesting about gold nanoparticles is their unique optical and physical properties that are much different from the usual “gold” color you see in everyday gold; spherical gold nanoparticles exhibit a wine red color, while other rod-shaped gold nanoparticles can be purple, blue, green, or brown. These characteristics can easily be controlled by varying the synthesis conditions of the nanoparticles, which can be done right here in our lab, making the use of gold nanoparticles easy and efficient for our experiments.

Gold nanoparticles of spheres to rods (left to right) which highlights the unique optical properties associated with changes in the particle shape.

Gold nanoparticles of spheres to rods (left to right) which highlights the unique optical properties associated with changes in the particle shape.

For my research this summer, only spherical nanoparticles were used during the exposure of woodfrog tadpoles to gold nanoparticles by Dr. Fong in the biology department. In this experimental protocol, the tadpoles were kept in tanks with water containing 100 parts per billion gold (0.0001 grams of gold per liter of water) for 20 days followed by varied amounts of time (between zero and 15 days) in tanks containing only water. This method was meant to quantify the average gold level contained in the tadpoles as a function of time kept out of the gold containing water.

My work this summer was the processing of these tadpoles to determine exactly how much gold was contained in the different groups that were exposed to various conditions. In order to do this, each tadpole had to be transferred into a liquid solution by dissolving each in various acids and a filtration step to clean them. With these steps all of the gold contained inside each tadpole was transferred to the acid solution, which can be analyzed by inductively coupled plasma/optical emission spectroscopy (ICP-OES). This interesting analysis utilizes a very hot plasma flame (above 5000°C!) to atomize the molecules, or break the chemical bonds, contained in the solution and raises electrons in these atoms to higher energy states. As these electrons move out of these higher energy states, they release energy in the form of light, and the ICP-OES can analyze this lights intensity and, depending on the amount of light emitted as well as calibration values of known gold concentration, determine the concentration of gold in the sample!

An example of the ICP-OES setup used to analyze the amount of gold contained in our samples.

An example of the ICP-OES setup used to analyze the amount of gold contained in our samples.

So far, a trend has emerged showing that gold is in fact being secreted by the tadpoles as a function of time immersed in water after an initial gold exposure. This exciting data that in just five days of water inhabitance, the amount of the gold in the tadpoles has been cut by over half. Although we hope that tadpoles such as these never are exposed to this concentration of gold in their natural habitat, research such as this to determine its effects at higher doses than the natural background is essential considering the boom of nanoparticle use in technology today.

Our initial data of the average amount of micrograms (10-6 grams) of gold per gram of tadpole mass found in the conditions of varying water exposure.

Our initial data of the average amount of micrograms (10-6 grams) of gold per gram of tadpole mass found in the conditions of varying water exposure.

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