Colloidal characterisations for environmental exposure assessment in support of the risk assessment of nano-biomaterials for biomedical applications

Abstract

The rapid growth of nanotechnology applications in medical products has been driven by their novel physicochemical properties that promise improved functionality. However, many unknowns remain regarding their potential impact upon environment and human health. Furthermore, the regulatory guidelines to enable effective assessment and management of possible risks are poorly harmonised. In this context, recent research projects propose to develop integrated exposure assessment frameworks for nano-biomaterials (NBMs) and general nano-releases. In this thesis, an investigation into the landscape of nano-biomaterials (NBMs) is outlined. This incorporates an overview of life-cycle thinking applied to NBM risk assessment, and a regulatory review of NBMs across various life cycle stages, where different targets of intentional exposure (patients) or unintentional exposure (workers, environment) can be identified. The effect of physicochemical properties of NBMs upon exposure and (eco)toxicity were considered, with attention given to environmental fate processes, of which agglomeration was identified as a key driver of environmental fate and behaviour. A critical review of physicochemical characterisation methods led to the identification of certain techniques apt to NBM colloidal characterisation. The agglomeration processes themselves arise under the combined influence of pH, salinity, ionic strength and natural organic matter concentration, and thus the colloidal stability of pristine TiO2 and coated nanoparticles were investigated across a range of environmentally relevant values. By utilising Principal Component Analysis (PCA), the relationships between extrinsic and intrinsic properties of the target nanomaterial were clearly expressed, contributing to the growing understanding of nanomaterial dynamics in environmental media. This result can support the characterization of ecological risks of NBMs in the case of releases to environmental compartments.