Session 5

The Hydra assay as an early screen for teratogenic potential

Mismanaged plastic litter submitted to environmental conditions may breakdown into smaller fragments, eventually reaching nano-scale particles (nanoplastics, NPLs). In this study, pristine beads of four different types of polymers, three oil-based (polypropylene, PP; polystyrene, PS; and low-density polyethylene, LDPE) and one bio-based (polylactic acid, PLA) were mechanically broken down to obtain more environmentally realistic NPLs and its toxicity to two freshwater secondary consumers was assessed. Thus, effects on the cnidarian Hydra viridissima (mortality, morphology, regeneration ability, and feeding behavior) and the fish Danio rerio (mortality, morphological alterations, and swimming behavior) were tested at NPLs concentrations in the 0.001 to 100 mg/L range. Mortality and several morphological alterations were observed on hydras exposed to 10 and 100 mg/L PP and 100 mg/L LDPE, whilst regeneration capacity was overall accelerated. The locomotory activity of D. rerio larvae was affected by NPLs (decreased swimming time, distance or turning frequency) at environmentally realistic concentrations (as low as 0.001 mg/L). Overall, petroleum- and bio-based NPLs elicited pernicious effects on tested model organisms, especially PP, LDPE and PLA. Data allowed the estimation of NPLs effective concentrations and showed that biopolymers may also induce relevant toxic effects.

Leveraging the biocatalytic machinery of living organisms for fabricating functional bioelectronic interfaces, in vivo, defines a new class of micro-biohybrids enabling the seamless integration of technology with living biological systems. Previously, we have demonstrated the in vivo polymerization of conjugated oligomers forming conductors within the structures of plants.

Here, we expand this concept by reporting that Hydra, an invertebrate animal, polymerizes the conjugated oligomer ETE-S both within cells that expresses peroxidase activity and within the adhesive material that is secreted to promote underwater surface adhesion. The resulting conjugated polymer forms electronically conducting and electrochemically active μm-sized domains, which are inter-connected resulting in percolative conduction pathways extending beyond 100 μm, that are fully integrated within the Hydra tissue and the secreted mucus. Furthermore, the introduction and in vivo polymerization of ETE-S can be used as a biochemical marker to follow the dynamics of Hydra budding (reproduction) and regeneration. This work paves the way for well-defined self-organized electronics in animal tissue to modulate biological functions and in vivo biofabrication of hybrid functional materials and devices.

Animal models play critical roles in fundamental discovery and bioactivity testing to name some activities, and therefore, they represent an invaluable resource for biomedical research and for predicting the efficacy and toxicity of new therapeutic and diagnostic agents. The role of animal models is crucial in many research fields, including the emerging nanomedicine, which demands not only accurate testing of novel medical nanomaterials, but also the study of the interaction between the nanomaterial and the biological target it was designed for. Model organisms provide scientists with a platform to perform biocompatibility, toxicity, and preclinical screening. Invertebrate models also address the 3Rs principle (replacement, reduction, and refinement) by reducing ethical concerns, economic costs, and the number of superior animals to be used in further studies.

In this chapter, we will show the feasibility of using two promising invertebrate model animals, Caenorhabditis elegans and Hydra vulgaris, for both optical and magnetic hyperthermia studies. Following a brief introduction on the biology of both organisms presenting their advantages and limitations, we will overview their versatility to undergo multiple manipulations, hoping to provide the reader accurate criteria to select the most suitable animal model.

Although we will limit our discussion to two models, we predict a significant overlap in mechanisms and concepts with other simple model organisms not discussed in this chapter. Therefore, the final aim of this chapter is to contribute to the safe design and screen of nanomaterials for hyperthermia, boosting its translation to clinical use.

Animal models play critical roles in fundamental discovery and bioactivity testing to name some activities, and therefore, they represent an invaluable resource for biomedical research and for predicting the efficacy and toxicity of new therapeutic and diagnostic agents. The role of animal models is crucial in many research fields, including the emerging nanomedicine, which demands not only accurate testing of novel medical nanomaterials, but also the study of the interaction between the nanomaterial and the biological target it was designed for. Model organisms provide scientists with a platform to perform biocompatibility, toxicity, and preclinical screening. Invertebrate models also address the 3Rs principle (replacement, reduction, and refinement) by reducing ethical concerns, economic costs, and the number of superior animals to be used in further studies.

In this chapter, we will show the feasibility of using two promising invertebrate model animals, Caenorhabditis elegans and Hydra vulgaris, for both optical and magnetic hyperthermia studies. Following a brief introduction on the biology of both organisms presenting their advantages and limitations, we will overview their versatility to undergo multiple manipulations, hoping to provide the reader accurate criteria to select the most suitable animal model.

Although we will limit our discussion to two models, we predict a significant overlap in mechanisms and concepts with other simple model organisms not discussed in this chapter. Therefore, the final aim of this chapter is to contribute to the safe design and screen of nanomaterials for hyperthermia, boosting its translation to clinical use.

Ephyrae of the scyphozoan jellyfish, Aurelia aurita, were evaluated in 96-hr acute toxicity tests for lethal response to Macondo crude oils from the Deepwater Horizon (DWH) incident in the Gulf of Mexico (GOM), Corexit 9500, and oil-dispersant mixtures. Water accommodated fractions (WAFs) of weathered and unweathered Macondo crude oils were not acutely toxic to ephyrae (LC50s > 100% WAF). The total PAHs (TPAHs), measured as the sum of 46 PAHs, averaged 21.1and 152 µg TPAH/L for WAFs of weathered and unweathered oil, respectively. Mortality was significantly (p = <0.0001) higher in the three highest exposure concentrations (184–736 µg TPAH/L) of chemically dispersed WAFs (CEWAF) compared to controls. Dispersant only tests resulted in a mean LC50 of 32.3 µL/L, which is in the range of previously published LC50s for marine zooplankton. Changes in appearance and muscle contractions were observed in organisms exposed to CEWAF dilutions of 12.5 and 25%, as early as 24 h post-exposure. Based on the results of these tests, crude oil alone did not cause significant acute toxicity; however, the presence of chemical dispersant resulted in substantial mortality and physical and behavioral abnormalities either due to an increase in hydrocarbons or droplet exposure.

The aim of this study was a preliminary investigation on the possibility of using the ephyra of Scyphozoan jellyfish Aurelia aurita (Linnaeus, 1758), the common moon jellyfish, as an innovative model organism in marine ecotoxicology.

A series of sequential experiments have been carried out in laboratory in order to investigate the influence of different culturing and methodological parameters (temperature, photoperiod, ephyrae density and age) on behavioural end-points (% of Frequency of Pulsations) and standardize a testing protocol. After that, the organisms have been exposed to two well known reference toxic compounds (Cadmium Nitrate and SDS) in order to analyse the acute and behavioural responses during static exposure. Results of this work indicate that the proposed behavioural end-point, frequency of pulsations (Fp), is an easily measurable one and can be used coupled with an acute one (immobilization) and that ephyrae of jellyfish are very promising model organisms for ecotoxicological investigation.