Clearance Properties of Nano-sized Particles and Molecules as Imaging Agents: Considerations and Caveats

Michelle Longmire; Peter L. Choyke; Hisataka Kobayashi

Disclosures

Nanomedicine. 2008;3(5):703-717. 

In This Article

Abstract and Introduction

Abstract

Nanoparticles possess enormous potential as diagnostic imaging agents and hold promise for the development of multimodality agents with both imaging and therapeutic capabilities. Yet, some of the most promising nanoparticles demonstrate prolonged tissue retention and contain heavy metals. This presents serious concerns for toxicity. The creation of nanoparticles with optimal clearance characteristics will minimize toxicity risks by reducing the duration of exposure to these agents. Given that many nanoparticles possess easily modifiable surface and interior chemistry, if nanoparticle characteristics associated with optimal clearance from the body were well established, it would be feasible to design and create agents with more favorable clearance properties. This article presents a thorough discussion of the physiologic aspects of nanoparticle clearance, focusing on renal mechanisms, and provides an overview of current research investigating clearance of specific types of nanoparticles and nano-sized macromolecules, including dendrimers, quantum dots, liposomes and carbon, gold and silica-based nanoparticles.

Introduction

Nanoparticles (NPs) and nano-sized molecules (NMs) possess enormous potential as diagnostic imaging agents and hold promise for the development of multimodality agents with both imaging and therapeutic capabilities. Generally defined as molecules with lengths that range from 1 to 100 nm in at least two dimensions, NPs and NMs show remarkable structural diversity and include nano-tubes, dots, wires, fibers and capsules.[1] Although nanotechnology has exciting implications for medicine, this technology presents challenges regarding particle biocompatibility and much is to be learned about the behavior of NPs and NMs in vivo. Unlike conventional imaging agents and therapeutics, many NPs are highly stable in vivo - exemplified by a recent study suggesting that quantum dots (QDs) may be retained in the body (and remain fluorescent) for more than 100 days.[2] Additionally, some of the most promising NPs currently under investigation contain heavy metals, which not only pose a risk for toxicity, but prolonged particle retention may interfere with diagnostic testing and imaging.[3]

Creating particles with optimal clearance characteristics will minimize toxicity risks and disease concerns posed by NPs and NMs by reducing the duration of exposure to these agents. Given that many types of NPs possess easily modifiable surface chemistry, if characteristics of NPs and NMs associated with optimal clearance were well established, it would be feasible to create agents with more favorable clearance properties. Properties currently known to affect clearance include particle material, size, shape, surface chemistry and charge - all of which vary depending on the individual particle type and modifications made for specific applications. This article presents a thorough discussion of the physiologic aspects of NP clearance, focusing on renal mechanisms, and provides an overview of current research investigating clearance of specific types of NPs and NMs, including dendrimers, QDs, liposomes and carbon, gold and silica-based NPs.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....