Gold nanoparticles, which have specific optical properties, have concrete applications in many fields, such as Organic solar cells, Sensor probe, Remedy, Biomedical drug delivery, Conductive material and so on. Moreover, it is known that regular distribution of particles will interfere with light. Gold nanoparticles spread on a surface of filter absorb UV partially and then passing UV interference each other. In two steps, this filter cuts UV. In this project, we focus on the property that such particles absorb and interfere light at specific wave lengths, in patricular UV. By using this, we design an optical filter that reduces ultraviolet rays. To accurately create an even distribution of particles, we use multiple rectangular DNA origamis from Rothemund et al.(designed DNA origami here). DNA origamis are modified so that some staple strands are extended and can capture fictionalized gold nanoparticles (see EXPERIMENT). Other staple strands are designed to bind to other origamis with the help of a ‘glue’ DNA strand. This optical filter is a material that both cuts UVs while being transparent at other wavelengths and may enable us to create novel transparent UV cut material, which could be used for contact lenses for instance.
It is known that gold nanoparticles absorb and interfere with specific lengths of lights based on their density and size.
We initially started our project focusing on light reflection and decided a goal to create a DNA solution that changes colors in a temperature dependent way. At first we thought of creating DNA sheets that reflect a specific length of light, and came up with the idea to attach gold particles onto their surface of them. Then, these sheets are stacked on top of each other using DNA strands, and by adjusting the Tm value of each strand, we thought it would be possible to create a structure in which the sheets peel off one at a time when the temperature rises. However, we realized there was a problem; the DNA origami, which is the size of 70nm by 100nm, was not large enough to arrange the particles with sufficient distance. This is why we changed our project and focused to UV, and then we aimed to make a UV reflecting DNA sheet.
The reason why we decided to focus on UV is that UV can be harmful depending on how much we get exposed to it. It damages our DNA and can cause mutations, which leads to errors in replication and transcription. In the worst case, this causes skin cancer. UV is also known to be harmful to our eyes. Excess exposure to UV is one of the factors of cataract and keratitis.
In order to protect our skin cells from the damage of UV, melanin is produced in our skin. The color of this substance is what makes our skin darker when we get a suntan. The more sun we get, the more melanin is produced, and therefore, the more suntan we get. Japanese women are very careful about the color of their skin. Many of them do not like to tan their skin in the summer as many people in other countries do. There are many UV protecting goods in Japan, such as arm covers, portable parasols and broad-brimmed hats. We can say that Japanese woman, including us, are concerned about sunlight and UV to a great extent. Since UV protection is such a familiar topic, we decided to choose it as our focus.
This DNA-based UV cutting sheet protects you from the harmful UV, and can be used for various situations. It can be used not only in the same way as other UV cutting materials, for instance, for windows, sun glasses and walls, but also in a new way. We propose an eye drop that prevents diseases caused by excess exposure to sunlight. By forming this sheet on our eye, we can protect the entirety of it, not only our pupil as previously developed UV-cut contact lenses do. This ultra violet cutting system is elegant because it works without a risk of wounding eyeball like contact lens, and innovative because it can cut ultra violet in the transparency state; therefore, it will not change the color of your field of vision. However, because the effect of gold nanoparticles on our human body hasn’t been studied well enough, there may be a long way to realization.
To realize this eye drop, we need to examine RNA that is more stable than DNA, or to research the effect of AuNPs for human body, and so on. However, if there is a substitution that has less effect on us than gold particles, this transparent UV cut sheet can be an innovative material. And, our examination is the important first step.
The goal of this project is to make a material that absorbs UV specifically. In order to consider the project a success, the following criteria need to be met.1. Based on the computer simulation results, the AuNP-attached DNA sheet absorbs ultra violet and that its absorbance is higher than other wavelengths.
Our first idea was to make an eye drop that was made of DNA sheet and can cut ultra violet. However, we thought it would need a lot of steps to put this idea into practice. Thus, for the first step of this project, we focused on two basic goals over the summer. The first aim was to attach AuNPs on DNA origami and form DNA sheet by connecting these DNA origamis each other. The second aim was to check whether this sheet had the effect of intercepting ultra violet. Those themes were not engineering but scientific, so it suited for us because we major in science.
We are new to the field, but Dr. Nathanael Aubert-Kato, the team's supervisor, thoroughly supported us by using his specialized knowledge of DNA computing and the experience of coaching other BIOMOD teams before. Additionally, the graduate school of Ochanomizu University gave us access to consumable and facilities that were necessary for our experiments.
This project was feasible because we chose doable objective in fieldswhere proper expertise was available and we could get enough support.