The effects of nanoparticles on health

There are around 100 trillion harmless and beneficial microbes in the gut, representing as many as 5,000 different species! They are called the gut microbiota and are essential for regulating brain function through the microbiota-gut-brain axis, controlling intestinal inflammation and more. Nanoparticles may alter the gut microbiota, posing a risk to health and well-being. Read on to find out more about how.

What are nanoparticles?

Nanoparticles are small particles that are usually less than 100 nm in diameter. One example of a common nanoparticle is silicon dioxide, which can be found as the food additive E551. Silicon dioxide nanoparticles (SiO2NPs) are commonly used as anti-caking agents in free-flowing powdery food products, such as spices and coffee.

These nanoparticles can be toxic, damaging cells, tissues, and organs including the liver, kidneys, and lungs. The damage is primarily due to the way SiO2NPs react in the body as a result of their size: even though SiO2NPs are bigger than 100 nm in the form of E551, when the SiO2NPs are in the gastrointestinal tract, they can clump together and degrade into a smaller size of 10-50 nm.

The experiment

Researchers completed several experiments to examine the effects of exposure to SiO2NPs on health. This article will specifically talk about one experiment where they looked at the impacts of SiO2NPs on the gut microbiota. For this experiment, the researchers hypothesised that oral exposure to SiO2NPs will cause changes in the gut microbiota, affecting diversity and function in mice. 20 healthy male 4-week-old mice were used, weighing 8 to 12 grams.

Researchers administered either SiO2NPs solution or vehicle solution for 28 days. The vehicle solution can be considered the control and was created out of a sterile saline solution.

All bacteria contain the 16S rRNA gene which is highly conserved, meaning that the sequence remains mostly unchanged across different species. After 28 days, the researchers took faecal samples from the mice and conducted 16S rRNA gene sequencing of the bacterial DNA in the faeces to analyse the gut microbiota. Figure 1 shows the process of 16S rRNA gene sequencing, a method used to identify and compare bacterial diversity without needing to grow bacterial cultures. Because it is culture-free, 16S sequencing can survey complex microbiomes or difficult environments to study. This technique is commonly used to identify bacteria down to the genus or species level, depending on the needs of the experiments.

Researchers looked at the alpha diversity of the gut microbiota, with Sob, Ace, Chao, Simpson, and Shannon indices being used. Sob, Ace and Chao give information about the number of species, while Simpson and Shannon give information about the community diversity, including the species evenness.

The results

The results of this experiment, as seen in Figure 2, show that there was a significant increase in Sob, Ace, and Chao indices, but there was no substantial change in Simpson or Shannon indices. This suggests that SiO2NPs can change the diversity of gut microbiota, which could impact their biological functions. For example, if there are changes to the gut microbiota, it could result in increased inflammation in the intestine. This could potentially lead to the immune system’s defences in the gut being weaker, allowing harmful pathogens to pass through the epithelial barrier more easily.

Conclusion

One of the main weaknesses of this experiment is that it was conducted on mice. Because of this, the study's findings cannot be directly translated to humans. In addition, the study was conducted over only 28 days, meaning we don’t know the long-term effects and consequences of the impacts of SiO2NPs on the gut microbiota.

Nevertheless, this is still a critical study as it shows that SiO2NPs do impact the gut microbiota. It also shows that maintaining healthy gut microbiota is important. This can be done by being mindful of what we eat. So next time, instead of having instant noodles full of additives, think about making a home-made soup with your favourite vegetables! Eating unprocessed whole foods is not just good for us, but also for our gut microbiota!

Written by Naoshin Haque

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