The use of HRM shifts in qPCR to investigate a much neglected aspect of interference by intracellular nanoparticles

PLoS One. 2021 Dec 7;16(12):e0260207. doi: 10.1371/journal.pone.0260207. eCollection 2021.

Abstract

Genetic molecular studies used to understand potential risks of engineered nanomaterials (ENMs) are incomplete. Intracellular residual ENMs present in biological samples may cause assay interference. This report applies the high-resolution melt (HRM) feature of RT-qPCR to detect shifts caused by the presence of gold nanoparticles (AuNPs). A universal RNA standard (untreated control) sample was spiked with known amounts of AuNPs and reverse transcribed, where 10 reference genes were amplified. The amplification plots, dissociation assay (melt) profiles, electrophoretic profiles and HRM difference curves were analysed and detected interference caused by AuNPs, which differed according to the amount of AuNP present (i.e. semi-quantitative). Whether or not the assay interference was specific to the reverse transcription or the PCR amplification step was tested. The study was extended to a target gene-of-interest (GOI), Caspase 7. Also, the effect on in vitro cellular samples was assessed (for reference genes and Caspase 7). This method can screen for the presence of AuNPs in RNA samples, which were isolated from biological material in contact with the nanomaterials, i.e., during exposure and risk assessment studies. This is an important quality control procedure to be implemented when quantifying the expression of a GOI from samples that have been in contact with various ENMs. It is recommended to further examine 18S, PPIA and TBP since these were the most reliable for detecting shifts in the difference curves, irrespective of the source of the RNA, or, the point at which the different AuNPs interacted with the assay.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Caspase 7 / chemistry
  • Caspase 7 / genetics*
  • Cell Line
  • Citric Acid
  • Drug Stability
  • Gold / chemistry*
  • Humans
  • Metal Nanoparticles
  • Real-Time Polymerase Chain Reaction / standards*
  • Reference Standards

Substances

  • Citric Acid
  • Gold
  • CASP7 protein, human
  • Caspase 7

Grants and funding

MG received funding, i,e, this work was supported by the Department of Science and Technology (DST) of South Africa. NS also received funding, i.e. this work was supported by the NIOH/ NHLS Research Trust development grant (2014-2DEV29-SNT1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.