Quantum Dots for Cancer Diagnosis and Therapy: Biological and Clinical Perspectives

Hua Zhang; Douglas Yee; Chun Wang

Nanomedicine.  2008;3(1):83-91.  ©2008 Future Medicine Ltd.
Posted 06/05/2008

Abstract and Introduction
Abstract
Quantum dots (QDs) are semiconductor nanocrystals that emit fluorescence on excitation with a light source. They have excellent optical properties, including high brightness, resistance to photobleaching and tunable wavelength. Recent developments in surface modification of QDs enable their potential application in cancer imaging. QDs with near-infrared emission could be applied to sentinel lymph-node mapping to aid biopsy and surgery. Conjugation of QDs with biomolecules, including peptides and antibodies, could be used to target tumors in vivo. In this review, we summarize recent progress in developing QDs for cancer diagnosis and treatment from a clinical standpoint and discuss future prospects of further improving QD technology to identify metastatic cancer cells, quantitatively measure the level of specific molecular targets and guide targeted cancer therapy by providing biodynamic markers for target inhibition.

Introduction
Imaging is an important clinical modality used in determining appropriate cancer therapy. Current imaging techniques, including x-ray, computed tomography, ultrasound, radionuclide imaging and MRI, have been used widely for cancer screening and staging, determining the efficacy of cancer therapy and monitoring recurrence (reviewed in).[1-4] However, current imaging techniques have two major limitations. First, they do not have sufficient sensitivity to detect small numbers of malignant cells in the primary or metastatic sites. Second, the imaging techniques have not been developed to detect specific cancer cell-surface markers. In many instances, these cell-surface markers might be targets for cancer therapy and might assist in the diagnosis and staging of cancer. These limitations demand improvement in current imaging techniques and the development of new imaging probes that are highly sensitive and biospecific. Quantum dot (QD) imaging probes, although still in the early development stage, provide the potential to fulfill these requirements for in vivo cancer imaging.

The composition, optical properties and bioconjugation of QDs have been reviewed extensively.[5-7] In this article, we focus on addressing recent progress and future challenges in cancer imaging using QDs from biological and clinical perspectives and discuss the potential of QD imaging to achieve high sensitivity and specificity that might bring significant impact to how cancer is diagnosed and treated in the clinical setting.