Contents

1. Introduction

1.1 Problems caused by conventional sunscreens and our proposed solution 1.2 Lignin as a natural UV absorber

1.3 Objectives 2. Methodology

2.1 Preparation of lignin-based coconut oil

2.2 Preparation of DNA solution and UV radiation treatment 2.3 Gel electrophoresis, staining and image capture

2.4 Biosafety test 3. Results and Discussions

3.1 DNA damage analysis 3.2 Biosafety test

3.3 Cost comparison between lignin-based and conventional sunscreens 4. Future directions

5. Conclusion 6. References

Introduction

Problems caused by conventional sunscreens and our proposed solution

It is necessary for us to put on sunscreen to protect ourselves from the harmful effects of ultraviolet (UV) rays from the sun.

Conventional sunscreens block or absorb UV rays, which protects us from eye damage, sunburn and even skin cancer.

However, most commercial sunscreens contain oxybenzone and ​octocrylene, which is detrimental to the environment​. ​When released into coral reef areas, ​oxybenzone causes the outer epidermal cells of coral larvae to calcify into skeleton during the wrong stage of development. Oxybenzone is also toxic to the nutrient-providing symbiotic algae living inside corals, and when the algae are killed, the coral will turn white and fail to survive.

We hope the government would address this issue by replacing the sunscreen that contains oxybenzone and octocrylene with

biodegradable sunscreen and by setting regulations to reduce the use of sunscreen in order to minimize the damage to ocean ecosystems. Aiming to tackle this problem, we plan to invent a biodegradable non-toxic sunscreen which does not harm the aquatic environment.

Lignin as a natural UV absorber

Lignin is a complex chemical containing free and etherified hydroxyl groups, which contributes to the characteristic absorption spectrum minimum of 280 nm. Its unsaturated substituents on carbon side chains, e.g. carbonyls, are responsible for the absorption spectrum near UV regions (300-400 nm).

Moreover, the absorption minima of unconjugated guaiacyl and 3,4-dimethoxy-phenyl (aromatic constituents of lignin) fall within the narrow wavelength range of 277-282 nm (UVB & UVC). These chemical constituents allow lignin to absorb radiation within the UV spectrum. Energy absorption from UV rays excites double-bonded electrons in these functional groups onto higher energy levels which is then dissipated as heat (infrared waves with lower

frequency).

Objectives

Due to the aforementioned reasons, we would like to invent a sunscreen using lignin as the active ingredient. We hope our results can raise public awareness on the harmful effects of conventional

sunscreens, and to persuade companies to use lignin to replace chemicals such as oxybenzone in their sunscreen products.

Methodology

Preparation of lignin-based coconut oil and lignin solution

1%, 2% and 10% aqueous lignosulphonate solutions were prepared with ratios of mass (w/w). Upon heating, the lignin compound dissolves into the water. The same method was used to dissolve the lignin compound in liquid coconut oil. The lignin-based coconut oil was only used when the mixture cooled down and solidified. Coconut

oil served as the base of our product as it is cheap, easily obtainable and most importantly, organic and safe, causing no harm to the environment. Moreover, it is a lipid which facilitates the dissolving of lignin compounds into the oil.

Preparation of DNA solution and UV radiation treatment

We obtained DNA from a commercial kit. Firstly, we transferred 20μl DNA solution into each microcentrifuge tube with the help of a micropipette. Without closing the lid of the microcentrifuge tubes, transparent cling wrap was used to seal

the top of the microcentrifuge tubes in a taut manner to create a flat surface for the application of chemicals.

Two sets of microcentrifuge tubes were prepared and each set was put under UV light for 10 and 48 hours respectively. We obtained a UVB lamp [T8, 10W] to imitate the scenario of UV rays damaging the DNA of cells. The UV lamp was hoisted 89mm above the tubes. The following setups were prepared:

a negative control setup which was not put under the UV light, and a control which had no additional liquid put onto the cling wrap, and setups which were covered lightly with conventional sunscreen, lignin-based sunscreen, coconut oil and aqueous lignosulfonate solution.

Gel electrophoresis, staining and image capture

We carried out gel electrophoresis to separate the DNA. The DNA samples were mixed with loading dye and were then loaded into the wells at the negative end of the gel with a pipette.

After that, the gel was placed inside the TAE buffer to maintain a stable pH. An electrical current of 120 volts from the mains power supply passed through the gel for around ​20 ​minutes, the negatively charged DNA molecules were attracted towards the positive electrode. The faster the DNA molecule moves, the more damaged it is. The degree of damage of the UV light on the DNA strands can also be clearly shown as the strands with more damage forming a less dense and less compact band. This provides clear results on the extent of damage on the DNA strand, and also a clear result to do comparisons.​ ​After gel

electrophoresis, the gel was stained and placed onto a rocking platform overnight, so that the DNA bands could be stained clearly onto the gel.

Biosafety test

Boehlkea fredcochui

​

freshwater fish and has a very active metabolism, thereby showing the results of the chemicals on the physiology of the fish quickly. Seventy individuals were randomly separated into seven tanks containing either tap water, 0.01%, 0.1% and 1% (w/w) lignin solution and conventional sunscreen. Conventional sunscreen was obtained from a company

(Coppertone). The survival rate was assessed every day for a week.