Abstract
Semiconductor Quantum dots (QDs) have generated extensive interest for biological and clinical applications. These applications arise from their unique properties, such as high brightness, long-term stability, simultaneous detection of multiple signals, tunable emission spectra. However, high-quality QDs, whether single or core-shell QDs, are most commonly synthesized in organic solution and surface-stabilized with hydrophobic organic ligands and thus lack intrinsic aqueous solubility. For biological applications, very often it is necessary to make the QDs dispersible in water and therefore to modify the QD surfaces with various bifunctional surface ligands or caps to promote solubility in aqueous media. Well-defined methods have been developed for QD surface modification to impart biocompatibility to these systems. In this review, we summarize the recent progress and strategies of QDs surface modification for potential cancer diagnostic and therapeutic applications. In addition, the question that arose from QD surface modification, such as impact of size increase of QD bioconjugates after surface-functionalization or surface modification on photophysical properties of QDs, are also discussed.
Highlights
Cancer is one of the most serious health threats worldwide, with an estimated 12.7 million new cases and 7.6 million cancer deaths in 2008 [1]
We summarize the recent progress and strategies in Quantum dots (QDs) surface modification for cancer diagnostics and therapeutics related applications: (1) the growth of additional layer, for instance a silica shell, around the nanoparticles, through surface silanization; (2) the exchange of hydrophobic surfactant molecules with bifunctional molecules; (3) coating of QD surfaces with amphiphilic polymers, phospholipid micelles, or microspheres
The sizes of QDs are comparable to those of large proteins, it is important to note that the surfacefunctionalization and further conjugation of biomolecules can increase the sizes of QD bioconjugates
Summary
Cancer is one of the most serious health threats worldwide, with an estimated 12.7 million new cases and 7.6 million cancer deaths in 2008 [1]. The unique optical properties of QDs make them appealing as in vivo and in vitro fluorophores in various biological and medical applications, such as diagnosis and therapy of cancer [7,8,9,10,11]. QDs are typically synthesized from various semiconductor materials which can provide access to a full range of potential emission wavelengths. High-quality QDs, whether single or core-shell structures, are most commonly synthesized in organic solution and surface-stabilized with hydrophobic organic ligands and lack intrinsic aqueous solubility. We summarize the recent progress and strategies in QDs surface modification for cancer diagnostics and therapeutics related applications: (1) the growth of additional layer, for instance a silica shell, around the nanoparticles, through surface silanization; (2) the exchange of hydrophobic surfactant molecules with bifunctional molecules; (3) coating of QD surfaces with amphiphilic polymers, phospholipid micelles, or microspheres. The questions that arose from QD surface modification, such as the impact size increase of QD bioconjugates after surface functionalization or surface modification on photophysical properties of QDs, are discussed
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