Nanoparticles in Biomedical Applications and Their Safety Concerns

Abstract

In this chapter, we will discuss the fate of nanoparticles when they are introduced into a system. Recent advances in synthesis and functionalization of nanoparticles have brought a significant increase in their biomedical applications, including imaging of cell and tissues, drug delivery, sensing of target molecules, etc. For example, iron oxide nanoparticles (Feridex) have been clinically administered as a contrast agent in magnetic resonance imaging (MRI). Their superb magnetic properties provide a significant contrast of tissues and cells where particles were administered. The use of Feridex as a MRI contrast agent enables a facile diagnosis of cancers in diverse organs in their early stages of development. As the range of different nanoparticles and their biomedical applications continue to expand, safety concerns over their use have been growing as well, leading to an increasing number of research on their in vivo toxicity, hazards, and biodistributions. While the number of studies assessing in vivo safety of nanoparticles has been increasing, a lack of understanding persists on the mechanisms of adverse effects and the distribution pathways. It is a challenge to correlate reports on one type of particles to reports on other types due to their intrinsic differences in the physical properties (particle size, shape, etc.) and chemical properties (surface chemistry, hydrophobicity, etc.), methods of preparation, and their biological targets (cells, tissues, organs, animals). Discrepancies in experimental conditions among different studies is currently bewildering the field, and there exists a critical need to arrive at a consensus on a gold standard of toxicity measure for probing in vivo fate of nanoparticles. This chapter summarizes recent studies on in vivo nanoparticle safety and biodistribution of nanoparticles in different organs. An emphasis is placed on a systematic categorization of reported findings from in vivo studies over particle types, sizes, shapes, surface functionalization, animal models, types of organs, toxicity assays, and distribution of particles in different organs. Based on our analysis of data and summary, we outline agreements and disagreements between studies on the fate of nanoparticles in vivo and we arrive at general conclusions on the current state and future direction of in vivo research on nanoparticle safety.