Project Inspiration
Heavy metal pollution is an invisible killer in Hong Kong, affecting both our environment and health. Dangerous metals like lead, mercury, cadmium, and zinc can be found in water sources from various origins such as agricultural land pollution, joints of water pipes, and sewage water pouring into storm drains. There was even a scandal where lead-contaminated water in a public housing estate affected hundreds of people.[1][2] Moreover, intaking Traditional Chinese medicine (TCM) or TCM supplements also put one at risk as herbs and raw materials used in TCM had been reported to contain harmful levels of heavy metals from contamination or naturally occurring sources.[3][4] On top of that, the Centre for Food Safety (CFS) announced that a crab sample and a escolar sample were detected with cadmium and methylmercury respectively.[5]Apart from that, eight households in Oi Tung Estate also tested that water contained metallic impurities, including lead, aluminium, zinc and copper.[6]
Figure 1: News and reports of heavy metal contamination incidents in Hong Kong
While current methods to detect these metals can have their own strengths, most are too complicated and expensive for everyday use. The general public remains worried and concerned.
Figure 2: Advantages and disadvantages of current methods to detect lead, mercury, cadmium and zinc
Our solution: Metalytic
Our iGEM 2024 project aims to create simple and affordable biosensors to help people easily detect heavy metals in daily life. These biosensors will target common heavy metals like lead, mercury, cadmium, and zinc, and are designed to be user-friendly, requiring no special tools or knowledge. Being portable, they cause less environmental damage since they use fewer harmful or toxic chemicals. From our interviews with experts, we learned that traditional chemical testing methods for heavy metals can be affected by other substances in the sample. However, biosensors offer higher specificity due to the precise interaction between proteins and metals. By making it easy for everyone to test for these pollutants and raising awareness about the issue, we hope to protect people's health and make our environment safer. Our product features include:
Design of the Heavy Metal Biosensors
GM E. coli strains were designed to express chromoproteins in the presence of targeted heavy metals, allowing concentration-dependent colour change visible to naked-eye for easy identification. This was made possible by using following heavy metals-sensitive parts in our biosensors:
- pPbr operon (lead-sensing) In the presence of lead, it activates the expression of the downstream chromoprotein dTomato, which serves as the reporter signal.
- pCadA operon (cadmium-sensing) In the presence of cadmium, it activates the expression of the downstream chromoprotein amilCP, which serves as the reporter signal.
- MerR-pMerT operon (mercury-sensing) When mercury is present, the pMerT promoter drives the expression of the chromoprotein tsPurple, serving as the reporter signal.
- pZnt (zinc-sensing) Natively found in E. coli, pZnt promoter drives the expression of the chromoprotein eforRed as the reporter signal in the presence of zinc.
AI-Powered Detection for Automatic Monitoring
Our team is excited to introduce Metalytic, an easy and automatic warning and feedback system that detects heavy metals using our GM E. coli strains. Chromoproteins are expressed in the presence of heavy metals, and higher concentrations lead to stronger color intensity. This allows us to determine the presence of heavy metals and assess if their concentrations exceed safe limits. By integrating the E. coli culture system with AI and machine learning, Metalytic performs automatic color analysis and provides consistent feedback, ensuring efficiency and reliability.
Health Protection
Metalytic safeguards users' health by sending instant alerts when samples are found to have heavy metal exceeding the safe limits via IoT services. To add, our team is also dedicated to raising public awareness towards the seriousness of heavy metal pollution and promoting the use of synthetic biology in solving real-world problems, ensuring informed decision-making when they encounter similar incidents in the future.
References
- Westcott, B. and Chan, S. (2015, July 16). Hong Kong’s lead-in-drinking-water crisis: everything you need to know. South China Morning Post. https://www.scmp.com/news/hong-kong/health-environment/article/1840021/hong-kongs-lead-drinking-water-crisis-everything
- Lo, A. (2015, July 13). Explainer: How the water lead contamination scare became a citywide concern. Hong Kong Free Press. https://hongkongfp.com/2015/07/13/explainer-how-a-public-estates-lead-contamination-became-a-citywide-concern/
- Department of Health. (2013, May 7). Recall of mercury-tainted proprietary Chinese medicine. Press Release. https://www.dh.gov.hk/english/press/2013/130507-2.html
- Consumer Council Hong Kong. (2013, May 7). Recall of mercury-tainted proprietary Chinese medicine. Consumer Protection, Consumer Alert. https://www.consumer.org.hk/en/consumer-alert/2013050702
- The Government of the Hong Kong Special Administrative Region. (2024, May 14). Excessive cadmium and methylmercury found in crab sample and escolar sample respectively. Press Release. https://www.info.gov.hk/gia/general/202405/14/P2024051400734.htm
- Wong, B. S. K. (2017, December 5). Fears of a second Hong Kong water scare as heavy metals found in public estate tap water. South China Morning Post. https://www.scmp.com/news/hong-kong/health-environment/article/2122992/fears-second-hong-kong-water-scare-heavy-metals