Synthetic biology is one of the main methods adopted in solving biological issues. Applying the synthetic biology techniques in realistic problems is always the core of iGEM. Conducting the residential college lecture in university is one of the best ways of introducing synthetic biology to the general public. As an iGEM team formed by biomedical majored undergraduate students, we felt obliged in presenting and introducing synthetic biology to reveal its benefits and its affable face to university students. We held a residential college lecture in Ma Man Kei and Lo Pak Sam college at the University of Macau. By this chance, we also introduced nanoparticle pollution and our project as one potential solution. Students were interested in SANCE and actively in asking questions. Not only the students, the vice-rector of the University of Macau also found our project appealing and meaningful.

We chose two incubation time points: 6 minutes and 48 minutes to plot the graph.

In sample A obtained from Inner Harbour, we can see the concentration of nanoparticles captured by OPHT2 bacteria and wild-type bacteria has significant differences between each other. This river water sample contains heavy metals molecules and unknown dirty particles which might occupy the nanoparticles binding sites on the sticky protein of our bacteria SANCE. In terms of different time points incubation, OPHT2 shown able to capture more nanoparticles after 48 minutes incubation compared to 6 minutes. From Figure 2A, in fact we can see the concentration of nanoparticle captured by OPHT2 after 6 minutes and 48 minutes do not change, the significant increases due to the decrease of nanoparticle captured by wild-type bacteria after longer incubation time. Therefore, we can conclude that OPHT2 bacteria is able to capture nanoparticles even under the water sample A’s harsh environment due to the fact that there are significant differences in both time points.

In sample B which is a reservoir used to store water, Figure 2B shows that the nanoparticle concentration differences between OPHT2 and wild-type are both significant at 6 and 48 minutes incubation, indicating that our OPHT2 construct works well in sample B. From another viewpoint, the data is more significant under 6 minutes incubation compared to 48 minutes. Along with the increase of incubation time, the nanoparticle binding sites are gradually occupied. Thus, the concentration of nanoparticle captured decreases after 48 minutes incubation. As there are significant differences in both time points, we can conclude that our bacteria with OPHT2 construct works in water sample B environment.

From Figure 2C, it is shown that our bacteria SANCE performed the best capturing ability in sample C which is from the Outer Harbour. The nanoparticle concentration captured by OPHT2 bacteria is way higher than wild-type bacteria at 6 minutes incubation. At 48 minutes incubation time point, the significance decreases compared to the 6 minutes time point as the protein binding sites for nanoparticles will reach a saturation point along with the increase of incubation time. As this water source is from lake water, it makes sense that our bacteria SANCE can perform its sticky function normally in a cleaner water environment which has related normal pH and stable condition for bacteria in comparison to sample A and B. Therefore, it can be concluded that our bacteria able to capture nanoparticles in water sample C.

Based on the results above, we can safely conclude that our SANCE is able to perform similarly in realistic water conditions.

During our interview to Hong Kong experts, one of the interviewees from The University of Hong Kong, Professor Leung, Kenneth Mei Yee raised a concern that toxicity of nanoparticles might be harmful and powerful to kill our bacteria organisms. Therefore, we designed a survival test to investigate whether toxic nanoparticles can actually kill our bacteria. We have chosen two nanoparticles which is AgNP (20nm in size) and ZnO (30±10nm) respectively. 5 different concentrations of Zinc Oxide and Silver nanoparticles were prepared in LB broth solution with concentrations of 0.5 mg/L, 1 mg/L, 20 mg/L, 40 mg/L and 60 mg/L respectively. We chose this range because according to literature, the average concentration of AgNP in waste water treatment plants is 1 mg/L.