A carregar...
Publicação
Study of digestive processes on the bioaccessibility of polystyrene microplastics and potential intestinal toxic effect
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 765.49 KB | Adobe PDF |
Autores
Orientador(es)
Resumo(s)
Plastic production has grown 20-fold in the past 50 years. Plastics are present
across many sectors, from industrial usage to food packaging. Polystyrene is
a common polymer encountered in daily life. In 2019, global plastic production
reached 368 Mt and is predicted to double within 20 years [5]. Microplastics
are found at all levels of food chains and in the tissues of animals and humans.
There is no internationally recognized size definition, and they are classically
defined as being less than 5 mm. There is a lack of information regarding the
bioaccessibility of microplastics after being consumed by humans. This project
aimed to assess the possible effects of digestion processes on the bioaccessibility
of 5 μm polystyrene microplastics. This study began with the exposure of bivalves
to a red fluorescent concentration of polystyrene (in vivo assay), followed
by the digestion of biota samples using two different protocols[1, 6] and subsequent
analysis for retrieval fraction (KOH 10% protocol) and the bioaccessible
fraction (using a human-simulated digestion protocol). Furthermore, six dilutions
of only the juices from the final phase of human static simulated in vitro
digestion (INFOGEST) were exposed to human intestinal cell culture models
(Caco-2 and Caco-2/HT29MTX) for 24 hours, and an MTT assay was performed
to infer cell viability. Concurrently, an in vitro microplastic exposure assay with
human intestinal cells (Caco-2, HT-29, and Caco- 2/HT29MTX) exposed to six
different concentrations of red-fluorescent polystyrene microplastic was performed,
followed by a final assessment with an MTT assay. All experiments
were done in triplicate, with controls, using measures to mitigate external contamination.
The NOVA Medical School Ethics Committee approved this project.
For the scope of this thesis, experiments with other final phase samples were
not performed. Microplastic samples found in M. galloprovincialis, a commonly
consumed bivalve in Portugal and worldwide, have been a known issue. However,
research on the bioaccessible fraction resulting from digestion is limited.
This study found degradation of 5 μm diameter polystyrene microplastics after
two digestion protocols. Most pristine microplastics were reduced in size to
less than 4.77 μm (below the lower limit coming from the factory), with approximately
12,5% remaining bioaccessible after digestion in the INFOGEST protocol.
MTT assay results showed no significant change in cell viability when exposed
to microplastics, but further toxicity assessment methods are needed. For future
studies, considering the evaluation of the remaining water from mussels
might be a suitable approach to increase data robustness. Also, according to
the results of this research, using INFOGEST factor dilutions of 1:40 or greater
may be beneficial to avoid decreased cell viability. It is known that some degradation
can be due to digestive juices used in simulation (by extrapolation in
vivo), but recent research has pointed out that microorganisms may also play a
role. It is important to remember the indication of possible extensive degradation
from digestion because evidence is accumulating for smaller-sized plastics’
toxicological effects. For future studies, more samples must be used to assess
microplastic bioaccessibility and possible toxicological effects on human
intestinal cells.
Descrição
Palavras-chave
Mediterranean mussel Microplastic INFOGEST bioaccessibility