Microgut to assess the risk microplastics present to human health
Nanoplastics and microplastics (NMPs) are debris from the degradation of larger plastic-based products. Microplastics are typically under five millimetres across, nanoplastics under one micrometre. NMPs are now found everywhere; in oceans, seas, rivers and lakes, but also in soils, the atmosphere and even the food chain. “There is debate about exact quantities, which vary by location, but as we continue using plastics, the amount obviously increases,” says Bastien Venzac, research fellow from the MIGMIPS project, which was funded by the Marie Skłodowska-Curie Actions programme. Despite growing concern about how NMPs may impact human health, there remain significant gaps in knowledge about their toxicity. “First, we have to know which types of NMPs are able to pass through the human body’s main defensive barriers, namely the lungs, gut and skin,” explains Venzac, from the French National Centre for Scientific Research, the project host. MIGMIPS was set up to develop a method to determine what diameter, composition and shape of NMPs could pass through the gut epithelium, with a publication currently under development outlining how a model that mimics the gut epithelium was fabricated to assess this.
A more accurate engineering solution
The classic technique for checking the permeability of the gut barrier or epithelium is to culture it in vitro on a porous membrane, then test which particles can pass through the structure. “But most membranes available were not designed for NMPs, with pores too small for them to pass through. Added to which, the cultured epitheliums are still very different from real ones,” adds Venzac. MIGMIPS used high-resolution 3D printing to create a highly porous membrane, on which to culture a more accurate gut epithelium, even able to incorporate its folded shape. “Originally we planned to 3D-print a porous hydrogel directly into the relevant shape, at a resolution of around 20-50 micrometres. But we realised that it would not be robust enough to hold the epithelium, with too small pore sizes. So we decided to use a non-porous acrylate resin, while also printing a net-like structure at around 500 nanometres resolution, to control the pore sizes as we print them,” explains Venzac. The team is currently testing how the membrane’s fishing net-like design influences the development and functioning of the epithelium. So far, by varying the net’s pore sizes, along with the fibre diameter (from 500 nanometres to two micrometres), Venzac has found a pore size threshold of around six micrometres. If the pore size is above this, the cells pass through and so are unable to build a tight epithelium.
If you can’t measure it, you can’t manage it
A World Health Organization report into the potential impact of NMP exposure on human health, suggests that microplastic concentration in drinking water is over 100 particles per litre, with humans probably inhaling around 3 000 microplastics daily. Despite a lack of data, it is estimated that adults ingest around 0.6 micrograms of microplastics daily from food. “While the WHO report did not highlight any especially high risks from microplastics, it wasn’t because there are none but because we don’t have the data yet,” Venzac notes. MIGMIPS’ models offer health researchers a tool with which to assess the ability of NMPs to get inside the human body and potentially do damage. In years to come this could also prove invaluable for policymakers when crafting legislation to manage plastic pollution and the threat of microplastics. Towards this end, next year the team will start trialling the potential of NMPs to pass through the gut barrier.
Keywords
MIGMIPS, gut, microplastic, nanoplastic, epithelium, membrane, 3D printing, toxicity, health
