Papers by Ajmeeta Sangtani
Reviews in Fluorescence 2016, 2017
Since they were first described over two decades ago, interest in interfacing highly fluorescent ... more Since they were first described over two decades ago, interest in interfacing highly fluorescent semiconductor nanocrystals, or quantum dots, with biological systems has grown at an unabated pace. Examples of their demonstrated or intended use range from the labeling and tracking of cellular structures in vitro to drug/cargo delivery and tissue imaging in vivo. Over the past 10 years, our groups at the Center for Bio/Molecular Science and Engineering and The Optical Sciences Division at the U.S. Naval Research Laboratory, in conjunction with many collaborators, have developed expertise in QD design and synthesis, controlled attachment of biologicals to QDs, and interfacing QD-bioconjugates with living biological systems from the cellular to the organismal level. This chapter provides a chronology of these developments and details the progression of our QD materials from a mere fluorescent cellular label to a multifunctional, active material that can probe cellular behavior to extract information in ways not previously possible.
Systemic drug delivery relies on repeated dosing of large concentrations of poorly targeted drug ... more Systemic drug delivery relies on repeated dosing of large concentrations of poorly targeted drug leading to off-target toxicity. Recently, nanoparticle (NP)-mediated drug delivery (NMDD) has been developed as an approach to overcome the limitations of traditional drug delivery. The unique size-dependent properties of NPs and their ability to augment the activity of attached/loaded cargos makes them attractive drug delivery vectors. NPs are classified into two categories (soft or hard depending on their material composition) and our understanding of how to load and control soft NP materials currently surpasses that of hard NPs. In this dissertation we seek to further our fundamental knowledge of hard NP-based drug delivery systems. In Aim 1 we utilize a quantum dot (QD)-cell uptake peptide complex as a central scaffold to append various responsive peptide-drug constructs in order to modulate the toxicity of one of the most widely used chemotherapeutics, doxorubicin. By doing a comparative study of four chemical linkages, we determine the role played by attachment chemistry in controlling drug release. In Aim 2, we utilize the knowledge gained from Aim 1 to develop a system capable of overcoming multidrug resistance in cancer cells, which is known to severely limit the efficacy of chemotherapeutics. Our hard NP conjugate system is unique as it is one of the few systems reported in the literature to bypass multidrug resistance pumps without the need for exogenous drugs. Finally, in Aim 3 we append a peptide for membrane targeting and a photosensitizing drug capable of generating reactive oxygen species to the QD. This multifunctional system displays augmented therapeutic efficacy of the appended photosensitizer by delivering it to the membrane of cells and controlling its actuation using energy transfer. The work described here details basic concepts for the design of "smart" hard NP materials for internally and externally-triggered, active release of surface-appended drug cargos. Additionally, we hope to elucidate [...]
Colloidal Nanoparticles for Biomedical Applications XIII, 2018
Nanoparticle (NP)-mediated drug delivery offers the potential to overcome limitations of systemic... more Nanoparticle (NP)-mediated drug delivery offers the potential to overcome limitations of systemic delivery, including the ability to specifically target cargo and control release of NP-associated drug cargo. Doxorubicin (DOX) is a widely used FDA-approved cancer therapeutic; however, multiple side effects limit its utility. Thus, there is wide interest in modulating toxicity after cell delivery. Our goal here was to realize a NP-based DOX-delivery system that can modulate drug toxicity by controlling the release kinetics of DOX from the surface of a hard NP carrier. To achieve this, we employed a quantum dot (QD) as a central scaffold which DOX was appended via three different peptidyl linkages (ester, disulfide, hydrazone) that are cleavable in response to various intracellular conditions. Attachment of a cell penetrating peptide (CPP) containing a positively charged polyarginine sequence facilitates endocytosis of the ensemble. Polyhistidine-driven metal affinity coordination was used to self-assemble both peptides to the QD surface, allowing for fine control over both the ratio of peptides attached to the QD as well as DOX dose delivered to cells. Microplate-based Förster resonance energy transfer assays confirmed the successful ratiometric assembly of the conjugates and functionality of the linkages. Cell delivery experiments and cytotoxicity assays were performed to compare the various cleavable linkages to a control peptide where DOX is attached through an amide bond. The role played by various attachment chemistries used in QD-peptide-drug assemblies and their implications for the rationale in design of NPbased constructs for drug delivery is described here.
Journal of Nanoparticle Research, 2021
Photodynamic therapy (PDT) has emerged as an attractive therapeutic modality for the targeted des... more Photodynamic therapy (PDT) has emerged as an attractive therapeutic modality for the targeted destruction of abnormal cells as it involves the specific generation of reactive oxygen species (ROS) in tissue only in the combined presence of a photosensitizer (PS), incident excitation light, and molecular oxygen. A variety of effective PS molecules have been developed but they are often limited by poor water solubility or a lack of cell-type specificity. We have developed a quantum dot-chlorin e6 (QD-Ce6) nanobioconjugate system where the QD (5 nm diameter) serves simultaneously as a hydrophilic scaffold and an efficient Förster resonance energy transfer (FRET) donor to multiple Ce6 PS acceptors arrayed around the central QD. Decoration of the conjugate with a membrane-tethering peptide stably localizes the ensemble conjugate system on the exofacial leaflet of the plasma membrane of mammalian cells. Excitation of Ce6 in a FRET configuration results in membrane-localized ROS generation resulting in lipid peroxidation, increased membrane permeability, and inhibition of cellular proliferation. We present and discuss our results in the context of the further evolution of QD-based PDT systems.
Wiley Interdisciplinary Reviews: Computational Molecular Science, 2019
Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology
Therapeutic Delivery, 2016
A primary envisioned use for nanoparticles (NPs) in a cellular context is for controlled drug del... more A primary envisioned use for nanoparticles (NPs) in a cellular context is for controlled drug delivery where the full benefit of NP attributes (small size, large drug cargo loading capacity) can improve the pharmacokinetics of the drug cargo. This requires the ability to controllably manipulate the release of the drug cargo from the NP vehicle or 'controlled actuation.' In this review, we highlight new developments in this field from 2013 to 2015. The number and breadth of reports are a testament to the significant advancements made in this field over this time period. We conclude with a perspective of how we envision this field to continue to develop in the years to come.
A heterobifunctional reactive oxygen species (ROS)-responsive linker for directed drug assembly o... more A heterobifunctional reactive oxygen species (ROS)-responsive linker for directed drug assembly onto and delivery from a quantum dot (QD) nanoparticle carrier was synthesized and coupled to doxorubicin using EDC/sulfo-NHS coupling. The doxorubicin conjugate was characterized using 1H NMR and LC-MS and subsequently reacted under conditions of ROS formation (Cu2+/H2O2) resulting in successful and rapid thioacetal oxidative cleavage which was monitored using 1H NMR. The deprotected amine linker is amenable to peptide or protein conjugation prior to QD assembly or to direct conjugation to cognate reactive groups on ligands that cap the QD surface.
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Papers by Ajmeeta Sangtani