Current Strategies in Assessment of Nanotoxicity: Alternatives to In Vivo Animal Testing

Abstract

Millions of experimental animals are widely used in the assessment of toxicological or biological effects of manufactured nanomaterials in medical technology. However, the animal consciousness has increased and become an issue for debate in recent years. Currently, the principle of the 3Rs (i.e., reduction, refinement, and replacement) is applied to ensure the more ethical application of humane animal research. In order to avoid unethical procedures, the strategy of alternatives to animal testing has been employed to overcome the drawbacks of animal experiments. This article provides current alternative strategies to replace or reduce the use of experimental animals in the assessment of nanotoxicity. The currently available alternative methods include in vitro and in silico approaches, which can be used as cost-effective approaches to meet the principle of the 3Rs. These methods are regarded as non-animal approaches and have been implemented in many countries for scientific purposes. The in vitro experiments related to nanotoxicity assays involve cell culture testing and tissue engineering, while the in silico methods refer to prediction using molecular docking, molecular dynamics simulations, and quantitative structure–activity relationship (QSAR) modeling. The commonly used novel cell-based methods and computational approaches have the potential to help minimize the use of experimental animals for nanomaterial toxicity assessments.

A Review on Conventional and Advanced Methods for Nanotoxicology Evaluation of Engineered Nanomaterials

“…Acute versus chronic effects and hazards due to exposure to nanomaterials are also difficult to monitor. Therefore, various measurement techniques must be revised, wisely evaluated (for validity), and used in complex nanomaterial systems [98,99].…”

“…Additionally, different particle sizes, surface properties, and poor dispersion of NMs, leading to improper biological distribution and unreliable results, have been reported. Moreover, the interference of carbon-based nanomaterials with toxicity assays and their potential influence on nanotoxicity assessment have also been reported as significant limitations [98]. Previous literature has proved that some NMs can distort the toxicity assay result by adsorbing to the dye's reagents due to their high surface energy and large surface area to volume ratio.…”

Use of an in silico knowledge discovery approach to determine mechanistic studies of silver nanoparticles-induced toxicity from in vitro to in vivo

“…The use of animals for experimental purposes has been subjected to criticism based on both ethical and practical considerations, and these concerns provoke the desire to apply the 3Rs principles (i.e., reduction, refinement, and replacement) in research and develop alternative methods to substitute for traditional anima tests [ 14 ]. In light of this, the focus of nanotoxicology research has shifted from phenomenological observations to developing novel in vitro , ex vivo , in silico , and combined strategies for mechanistic explorations; the technological advances also help reduce the use of animals in toxicity testing [ 15 ].…”

Organoid Technology: A Reliable Developmental Biology Tool for Organ-Specific Nanotoxicity Evaluation

“…Two-dimensional (2D) monoculture is arguably the most preferred in vitro nanotoxicity assessment modality. The modality possesses multiple advantages including the popularity of cell culture-based methods, prominence, cost-effectiveness, high throughput, reproducibility, and most importantly, being devoid of the ethical constraints associated with animal and human experiments ( Evans et al, 2016 ; Huang et al, 2021 ). However, the lack of defined three-dimensional (3D) structures and cellular cross-talking networks pose limitations to this modality.…”

“…However, the lack of defined three-dimensional (3D) structures and cellular cross-talking networks pose limitations to this modality. Thus, it often fails to replicate in vivo tissue or organ microenvironment and behavior ( Evans et al, 2016 ; Huang et al, 2021 ). Recent developments to customize micro-tissues such as spheroids or organoids can overcome the limitations to provide a more pragmatic evaluation.…”