Genotoxic effects and transcriptional deregulation of genetic biomarkers in Chironomus riparius larvae exposed to hydroxyl- and amine-terminated generation 3 (G3) polyamidoamine (PAMAM) dendrimers

Abstract

The physical-chemical properties of polyamidoamine (PAMAM) dendrimers give them attractive qualities for multiple applications, including biomedical purposes. Their use has significantly increased in recent years, and there is currently a lack of information on their potential adverse effects on biological systems, which raises particular concerns about the risks to human health and the environment from their use and disposal. Studies focusing on ecotoxicological effects are particularly scarce. In the present work, we have used the model insect Chironomus riparius to assess the toxicity of hydroxyl-terminated and amine-terminated generation 3 PAMAM dendrimers: PAMAM G3-OH and PAMAM G3-NH2. Fourth-instar larvae were exposed to 10 or 100 ppm G3-OH or G3-NH2 dendrimers for 24 h (acute toxicity) or 24 + 24 h (delayed toxicity). Using quantitative real-time PCR, we analyzed transcriptional alterations in genes related to relevant physiological pathways: EcR, GAPDH, GPx, GST, hsp10, hsp24, Gp93, and rpL4. We also used the comet assay to assess the possible genotoxic characteristics of the dendrimers and their ability to induce DNA breakage. Regarding the effects on transcriptional activity, our results showed that G3-NH2 dendrimers induced greater (and in many cases opposite) alterations than G3-OH dendrimers, especially in acute 24-hour exposures. Delayed toxicity studies showed that both dendrimers produced transcriptional alterations even 24 h after the withdrawal of the compound and frequently contrary to what was observed acutely. In both cases, the lowest concentration studied (10 ppm) was the most toxic. On the other hand, the comet assay allowed us to detect genotoxic effects for the two dendrimers, thus demonstrating their ability to interact with DNA. This work provides new information about the possible disruptive effects of PAMAM G3 dendrimers on the health of exposed organisms, alerting the need to carry out more studies to deepen their toxic characteristics and mode of action, especially in natural environments.