Quantum Dot−Aptamer Conjugates for Synchronous Cancer Imaging, Therapy, and Sensing of Drug Delivery Based on Bi-Fluorescence Resonance Energy Transfer

Abstract

We report a novel quantum dot (QD)-aptamer(Apt)-doxorubicin (Dox) conjugate [QD-Apt(Dox)] as a targeted cancer imaging, therapy, and sensing system. By functionalizing the surface of fluorescent QD with the A10 RNA aptamer, which recognizes the extracellular domain of the prostate specific membrane antigen (PSMA), we developed a targeted QD imaging system (QD-Apt) that is capable of differential uptake and imaging of prostate cancer cells that express the PSMA protein. The intercalation of Dox, a widely used antineoplastic anthracycline drug with fluorescent properties, in the double-stranded stem of the A10 aptamer results in a targeted QD-Apt(Dox) conjugate with reversible self-quenching properties based on a Bi-FRET mechanism. A donor-acceptor model fluorescence resonance energy transfer (FRET) between QD and Dox and a donor-quencher model FRET between Dox and aptamer result when Dox intercalated within the A10 aptamer. This simple multifunctional nanoparticle system can deliver Dox to the targeted prostate cancer cells and sense the delivery of Dox by activating the fluorescence of QD, which concurrently images the cancer cells. We demonstrate the specificity and sensitivity of this nanoparticle conjugate as a cancer imaging, therapy and sensing system in vitro.

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

“…This can be exploited to generate the so-called aptamer sequences to a given target molecule by molecular evolution, technically realized by multiple randomization, selection and amplification of strongly binding sequences, resulting in an optimized strand of DNA, RNA or peptide for the target molecule with affinities comparable to antibodies (Bunka & Stockley 2006;Lu & Liu 2006;Mairal et al 2008). Aptamers have been attached to gold nanoparticles via a thiol function (Liu et al 2007a;Zhao et al 2008), to quantum dots or silica-coated Au particles by covalent conjugation chemistry (Bagalkot et al 2007;Jana & Ying 2008), to avidin-modified magnetic nanoparticles (Herr et al 2006), as well as biotinylated DNA apatamers to quantum dots with streptavidin (Levy et al 2005).…”

“…by growing nanocrystals with domains of different functional materials (Gu et al 2004;Kim et al 2005c;Zanella et al 2008), (ii) post-modification of particles with functional molecules, e.g. fluorescent quantum dots with paramagnetic organic molecules (Mulder et al 2006a;Bakalova et al 2007) or non-fluorescent nanoparticles with fluorescent dyes (Bertorelle et al 2006;Bagalkot et al 2007;Kim et al 2008a;Liong et al 2008), bio-functional molecules (Schellenberger et al 2004;Herr et al 2006;Garanger et al 2008), or (iii) assembly of composite materials e.g. by a combination of different nanoparticles with different functionality , or e.g.…”

Magnetic field remotely controlled selective biocatalysis

“…Note, the non-zero base line is due to a weak fluorescence of quenched DOX in the conjugate. Upon release, the DOX fluorescent intensity increases and recovers 32 (see Supporting Fig. 7).…”

Aqueous phase synthesis of CdTe quantum dots for biophotonics

“…Moreover, the polymer coating will have functional groups such as carboxyl and amine for conjugation purposes. More importantly, the overall hydrodynamic diameter size of the QDs must be minimized (<5-10 nm) to allow renal clearance after performing their task in the body such as drug delivery [79]. To date, some other QDs formulations such as CdSe/ZnS and CdTe/CdSe QDs have been successfully used for small animal studies [80].…”