Publications (10) View all
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Article: Spatiotemporal multicolor labeling of individual cells using peptide-functionalized quantum dots and mixed delivery techniques.
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ABSTRACT: Multicolor fluorescent labeling of both intra- and extracellular structures is a powerful technique for simultaneous monitoring of multiple complex biochemical processes. This approach remains extremely challenging, however, as it often necessitates the combinatorial use of numerous targeting probes (e.g., antibodies), multistep bioconjugation chemistries, different delivery strategies (e.g., electroporation or transfection reagents), cellular fixation coupled with membrane permeabilization, and complex spectral deconvolution. Here, we present a nanoparticle-based fluorescence labeling strategy for the multicolor labeling of distinct subcellular compartments within live cells without the need for antibody conjugation or cellular fixation/permeabilization. This multipronged approach incorporates an array of delivery strategies, which localize semiconductor quantum dots (QDs) to various subcellular structures. QD uptake is implemented in a spaciotemporal manner by staggering the delivery of QD-peptide composites and exploiting various innate (peptide-mediated endocytosis, peptide-membrane interaction, polymer-based transfection) along with physical (microinjection) cellular delivery modalities to live cells growing in culture over a 4 day period. Imaging of the different intracellular labels is simplified by the unique photophysical characteristics of the QDs in combination with Förster resonance energy transfer sensitization, which allow for multiple spectral windows to be accessed with one excitation wavelength. Using this overall approach, QDs were targeted to both early and late endosomes, the cellular cytosol, and the plasma membrane in live cells, ultimately allowing for simultaneous five-color fluorescent imaging.Journal of the American Chemical Society 06/2011; 133(27):10482-9. · 9.91 Impact Factor -
Article: Peptides for specific intracellular delivery and targeting of nanoparticles: implications for developing nanoparticle-mediated drug delivery.
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ABSTRACT: The use of peptides to mediate the delivery and uptake of nanoparticle (NP) materials by mammalian cells has grown significantly over the past 10 years. This area of research has important implications for the development of new therapeutic materials and for the emerging field of NP-mediated drug delivery. In this review, we highlight recent advances in the delivery of various NPs by some of the more commonly employed cellular delivery peptides and discuss important related factors such as NP-peptide bioconjugation, uptake efficiency, intracellular fate and toxicity. We also highlight various demonstrations of therapeutic applications of NP-peptide conjugates where appropriate. The paper concludes with a brief forward-looking perspective discussing what can be expected as this field develops in the coming years.Therapeutic delivery 09/2010; 1(3):411-33. -
Article: Delivering quantum dot-peptide bioconjugates to the cellular cytosol: escaping from the endolysosomal system.
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ABSTRACT: For luminescent quantum dots (QDs) to realize their full potential as intracellular labeling, imaging and sensing reagents, robust noninvasive methods for their delivery to the cellular cytosol must be developed. Our aim in this study was to explore a range of methods aimed at delivering QDs to the cytosol. We have previously shown that QDs functionalized with a polyarginine 'Tat' cell-penetrating peptide (CPP) could be specifically delivered to cells via endocytic uptake with no adverse effects on cellular proliferation. We began by assessing the long-term intracellular fate and stability of these QD-peptide conjugates. We found that the QDs remained sequestered within acidic endolysosomal vesicles for at least three days after initial uptake while the CPP appeared to remain stably associated with the QD throughout this time. We next explored techniques designed to either actively deliver QDs directly to the cytosol or to combine endocytosis with subsequent endosomal escape to the cytosol in several eukaryotic cell lines. Active delivery methods such as electroporation and nucleofection delivered only modest amounts of QDs to the cytosol as aggregates. Delivery of QDs using a variety of transfection polymers also resulted in primarily endosomal sequestration of QDs. However, in one case the commercial PULSin reagent did facilitate a modest cytosolic dispersal of QDs, but only after several days in culture and with significant polymer-induced cytotoxicity. Finally, we demonstrated that an amphiphilic peptide designed to mediate cell penetration and vesicle membrane interactions could mediate rapid QD uptake by endocytosis followed by a slower efficient endosomal release which peaked at 48 h after initial delivery. Importantly, this QD-peptide bioconjugate elicited minimal cytotoxicity in the cell lines tested.Integrative Biology 06/2010; 2(5-6):265-77. · 4.51 Impact Factor -
Article: Quantum dots: a powerful tool for understanding the intricacies of nanoparticle-mediated drug delivery.
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ABSTRACT: Nanoparticle-mediated drug delivery (NMDD) is an emerging research area that seeks to address many of the pharmacokinetic issues encountered with traditional systemically administered drug therapies. Although the field is still in its infancy, recent research has already highlighted the potential for improved drug delivery and targeted therapeutics; however, the real promise lies in combining drug therapy with diagnostic imaging, nucleic acid delivery/gene therapy and/or biosensing applications all in one engineered nanoparticle vector. In this review, the authors discuss the unique contributions that luminescent semiconductor nanocrystals or quantum dots (QDs) offer for NMDD, how they can function as a powerful nanoscale platform to understand this process at its most basic level, and even provide drug-related properties in certain circumstances. Selected examples from the current literature are utilized to describe both their potential and the contributions they have already made towards the design and implementation of NMDD vectors. Important related issues such as QD biofunctionalization and toxicity are also discussed. The paper concludes with a perspective of how this field can be expected to develop in the future.Expert Opinion on Drug Delivery 09/2009; 6(10):1091-112. · 4.90 Impact Factor -
Article: Organization of carboxysome genes in the thiobacilli.
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ABSTRACT: The order of genes in the carboxysome gene clusters of four thiobacilli was examined and the possibility of the cluster forming an operon evaluated. Furthermore, carboxysome peptide homologs were compared with respect to similarities in primary sequence, and the unique structural features of the shell protein CsoS2 were described.Current Microbiology 03/2003; 46(2):115-9. · 1.82 Impact Factor
