Challenges of microplastics as emerging contaminants in forensic DNA profiling and proposed mitigation strategies

With an increase in the global usage of plastics, the whole world is facing a huge threat from the microplastics and its subsequent health hazards. Though persistent microplastics contamination in the biological samples have been established, none of the literature have highlighted the problem faced by the forensic DNA analysis process due to microplastics contamination. The microplastics contamination has the potential to affect the forensic DNA analysis process adversely. Accumulation of microplastics in various tissue types such as thyroid (40.4 MPs/g), kidney (21.5 MPs/g), and brain (24.4 MPs/g) have been reported due to environmental and occupational exposure. During downstream processing steps, the biological samples placed in plasticwares are exposed to thermal shock, and harsh chemicals which results in the leaching of microplastics and co-extracted with DNA. The microplastic mediated DNA fragmentation and adsorption of microplastic on DNA surface can be attributed to be the cause of their adverse effect on every step of forensic DNA analysis. Addition of washings from polystyrene micropipettes to a PCR mixture showed significant PCR inhibition. The RT-PCR based DNA quantification and capillary electrophoresis-based detection of DNA fragments rely on the detection of fluorescence level generated from the amplified products. The autofluorescence nature of microplastics have the potential to interfere the fluorescence-based estimation of DNA quantity as well as generation of a DNA profile. This article summarizes the potential source of microplastic contamination in the biological samples, their interaction mechanism with DNA and its effect on various steps of routine forensic DNA analysis. Physical separation of microplastics from the contaminated biological samples and treatment of biological samples with chelating agents have the potential to mitigate the microplastic contamination in forensic DNA workflow.