R-3 Repository :: Browsing by Author "Drezek, Rebekah"

Browsing by Author "Drezek, Rebekah"

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Assessment of In Vivo Microscopy for Malaria Detection
(2014-10-23) Burnett, Jennifer; Richards-Kortum, Rebecca Rae; Drezek, Rebekah; Tkaczyk, Tomasz
Half of the world’s population is at risk for malaria, yet 90% of deaths due to malaria occur in sub-Saharan Africa, with the highest mortality rates occurring in children under 5. Due to this high mortality rate, children with common flu-like symptoms are often treated for malaria presumptively. This overtreatment with anti-malarial drugs can contribute to the emergence of drug resistant species. Commercially available diagnostic tools, such as blood smear microscopy and rapid diagnostic tests, offer greater specificity than presumptive diagnosis, but require the collection of a finger prick blood sample for diagnosis, generating biohazards and requiring consumables. This thesis introduces a new diagnostic concept to detect parasitized blood cells as they circulate in vivo, avoiding the requirement for blood collection. The work presented here investigates two major components of this concept: 1) develop and characterize a needle-free malaria diagnostic system, and 2) evaluate the performance of the system in biological environments of progressively increasing complexity. Results show promising optical signatures from two biomarkers for malaria detection. This work demonstrates the feasibility for imaging circulating blood cells in vivo through a non-invasive technique, warranting future investigations in a small malaria-infected sample population.
Development and Characterization of a Novel Class of Self-Assembling dsRNA Cancer Therapeutics
(2018-08-03) Asthana, Vishwaratn; Drezek, Rebekah
Cancer has proven to be an extremely difficult challenge to treat. Several fundamental issues currently underlie cancer treatment including differentiating self from non-self, functional coupling of the recognition and therapeutic components of various therapies, and the propensity of cancerous cells to develop resistance to common treatment modalities via evolutionary pressure. Given these limitations, there is a profound need to develop an all encompassing therapeutic that can uniquely target malignant cells, decouple recognition from treatment, and overcome cancer resistance. We describe herein, a new class of programmable self-assembling dsRNA-based cancer therapeutics that uniquely targets aberrant genetic sequences, and in a functionally decoupled manner, initiates a therapeutic polymerization cascade that induces apoptosis and immune activation. We further show that a DNA protector can be used to selectively seal the therapeutic RNA and induce specific and potent killing of cells containing the target oncogenic sequence, but not wildtype.
Gold Nanoparticle Dendrimer Conjugates for Gene Therapy
(2015-04-24) Figueroa, Elizabeth Raquel; Drezek, Rebekah; Suh, Junghae; Wong, Michael; Foster, Aaron
Gene therapy is a promising treatment that has enormous potential for the management of numerous diseases of acquired and innate origin. Viral delivery vectors are successful in delivering therapeutic DNA, but their efficacy is circumvented by immunogenicity and cost. Non-viral vectors face other issues of inflammatory response, colloidal stability, and low transfection efficiency. Gold nanoparticles (AuNPs) have emerged as attractive nanocarriers for gene delivery. AuNPs are bioinert, easily synthesized, and possess rich surface chemistry that facilitates versatile functionalization. Therefore, AuNPs provide an excellent platform for gene delivery. Polyamidoamine (PAMAM) dendrimers are commercially available cationic branched polymers in which growth branches from a core molecule. Their physiochemical properties make PAMAM dendrimers well suited for gene delivery applications. In this thesis, PAMAM dendrimers are functionalized on the surface of small AuNPs yielding a unique class of gene delivery vectors termed AuPAMAM vectors. We begin by establishing the synthesis and characterization of AuPAMAM vectors, showing that AuPAMAM colloidal stability and DNA condensation ability are dependent on the PAMAM conjugation reaction rate, and that this reaction rate can be altered to enhance transfection efficiency in vitro. Then, we further investigate the influence of each chemical component of the bottom-up AuPAMAM synthesis process by systematically probing each step of the reaction and analyzing its effect on the overall transfection efficiency and cytotoxicity. Finally, in order to clarify the mechanism underlying the differential transfection efficiency seen across many cell lines and tissues, the AuPAMAM vectors are tracked intracellularly over time in vitro using confocal imaging, cellular TEM and flow cytometry. Together, this thesis demonstrates that AuPAMAM conjugates present attractive candidates for non-viral gene delivery due to their commercial availability, ease of fabrication and scale-up, high yield, high transfection efficiency and low cytotoxicity. Additionally, this thesis demonstrates the need to characterize the tissue-specific transfection hurdles vectors face in order to improve application-specific non-viral vector design.
Gold Nanoparticle Platforms for Antigen and Adjuvant Delivery in Cancer Immunotherapy
(2014-09-03) Mattos Almeida, Joao Paulo; Drezek, Rebekah; Suh, Junghae; Harrington, Daniel
Cancer immunotherapy is a growing treatment modality with the promise to yield systemic and targeted treatments for cancer. Major modalities such as radiation, chemotherapy, and surgery are limited in that they are either too localized--as is the case with radiation and surgery—and cannot be effective in metastatic disease, or they are not targeted-- as with chemotherapy--thus leading to severe toxicities. Immunotherapy aims to stimulate the body’s immune system against disease, allowing one to circumvent such challenges because the immune system can act systemically and can have specific activity against cancer cells expressing antigens of interest. The development of an effective cancer vaccine and subsequent immune response requires the delivery of an antigen for immune recognition and of an adjuvant for an inflammatory response. Gold nanoparticles (AuNPs) are promising vaccine carriers because they are generally non-toxic, can be synthesized in the optimal sizes for lymphatic drainage and cell uptake, and can be readily conjugated with antigens and adjuvants for delivery. This thesis project characterizes AuNP distribution in the immune system and details the development of AuNP mediated delivery of antigens and adjuvants for cancer immunotherapy. In our work, we have detailed AuNP distribution within immune cells of the spleen and the tumor microenvironment, thereby identifying that AuNPs associate with a range of immune populations, including B cells, dendritic cells, and macrophages, all of which can be potentially targeted for immune modulation. Next we developed AuNP complexes capable of delivering the CpG oligonucleotide adjuvant, demonstrating that AuNP delivery promotes the therapeutic effect of CpG in vitro and in vivo. In addition, we studied AuNP mediated delivery of the ovalbumin (OVA) peptide antigen and showed that AuNP delivery enhances vaccination with the antigen in vivo, subsequently causing tumor inhibition and prolonged survival in both prophylactic and established tumor models. The thesis thus elucidates AuNP interactions with the immune system and demonstrates that the technology is an effective platform for delivery of immune modulatory agents.
Gold Nanovaccine Strategies for Cancer Immunotherapy
(2018-04-18) Evans, Emily Reiser; Drezek, Rebekah
Gold nanoparticles have excellent properties for cancer therapeutics because their tunable size and surface chemistry make them customizable for many applications. For immunotherapy applications in particular, we can leverage their natural biodistribution to the spleen and immune cells for delivering peptide antigen vaccines or tune their optical properties for photothermal therapy to ablate tumors, which results in tumor antigen circulation and an in situ vaccination effect. Our group has demonstrated the potential of gold nanoparticles to elicit systemic, anti-tumor immunity through several iterations of particle design, characterization, and in vivo testing. However, most of the animal testing was done using a B16-OVA model, which is less clinically relevant due to the transgene antigen inserted for vaccination and tumor detection. My work builds upon the strong foundation of proof-of-concept vaccination strategies and examines the use of these gold nanoparticle platforms for cancer immunotherapy applications in a more clinically relevant tumor model. Though many hurdles remain for the first gold nanoparticles to reach FDA approval, this work demonstrates the progression of gold nanoparticle-enabled cancer immunotherapy toward that end and illustrates novel immunotherapeutic outcomes and combinations that may inform future progress toward identifying a clinically viable gold nanoparticle cancer immunotherapy strategy.
Interaction of Colloidal Gold Nanoparticles with Model Serum Proteins: The Nanoparticle-Protein ‘Corona’ from a Physico-Chemical Viewpoint
(2015-09-15) Dominguez-Medina, Sergio; Link, Stephan; Marti, Angel; Drezek, Rebekah
When nanoparticles come in contact with biological fluids they become coated with a mixture of proteins present in the media, forming what is known as the nanoparticle-protein ‘corona’. This corona changes the nanoparticles’ original surface properties and plays a central role in how these get screened by cellular receptors. In the context of biomedical research, this presents a bottleneck for the transition of nanoparticles from research laboratories to clinical settings. It is therefore fundamental to probe these nanoparticle-protein interactions in order to understand the different physico-chemical mechanisms involved. This thesis is aimed to investigate the exposure of colloidal gold nanoparticles to model serum proteins, particularly serum albumin, the main transporter of molecular compounds in the bloodstream of mammals. A set of experimental tools based on optical microscopy and spectroscopy were developed in order to probe these interactions in situ. First, the intrinsic photoluminescence and elastic scattering of individual gold nanoparticles were investigated in order to understand its physical origin. These optical signals were then used to measure the size of the nanoparticles while in Brownian diffusion using fluctuation correlation spectroscopy. This spectroscopic tool was then applied to detect the binding of serum albumin onto the nanoparticle surface, increasing its hydrodynamic size. By performing a binding isotherm as a function of protein concentration, it was determined that serum albumin follows an anti-cooperative binding mechanism on negatively charged gold nanoparticles. This protein monolayer substantially enhanced the stability of the colloid, preventing their aggregation in saline solutions with ionic strength higher than biological media. Cationic gold nanoparticles in contrast, aggregated when serum albumin was present at a low protein-to-nanoparticle ratio, but prevented aggregation if exposed in excess. Single-molecule fluorescence microscopy revealed that under low protein-to-nanoparticle binding ratios, serum albumin irreversibly unfolds upon adsorption and spreads across the available nanoparticle surface area. Unfolded proteins then interact with one another, triggering nanoparticle aggregation. Fibrinogen and globulin also triggered aggregation when exposed to cationic nanoparticles. In an effort to relate these physico-chemical observations to relevant biological parameters, the uptake of protein coated gold nanoparticles by a model cancer cell line was investigated under different incubation conditions. Those nanoparticles pre-incubated with bovine serum albumin before fetal bovine serum were found to be uptaken three times more than those only incubated in serum.
Metallic nanoparticles for cancer immunotherapy
(Elsevier, 2018) Evans, Emily Reiser; Bugga, Pallavi; Asthana, Vishwaratn; Drezek, Rebekah; Bioengineering; Electrical and Computer Engineering
Cancer immunotherapy, or the utilization of the body’s immune system to attack tumor cells, has gained prominence over the past few decades as a viable cancer treatment strategy. Recently approved immunotherapeutics have conferred remission upon patients with previously bleak outcomes and have expanded the number of tools available to treat cancer. Nanoparticles – including polymeric, liposomal, and metallic formulations – naturally traffic to the spleen and lymph organs and the relevant immune cells therein, making them good candidates for delivery of immunotherapeutic agents. Metallic nanoparticle formulations, in particular, are advantageous because of their potential for dense surface functionalizationand their capability for optical or heat-based therapeutic methods. Many research groups have investigated the potential of nanoparticle-mediated delivery platforms to improve the efficacy of immunotherapies. Despite the significant preclinical successes demonstrated by many of these platforms over the last twenty years, only a few metallic nanoparticles have successfully entered clinical trials with none achieving FDA approval for cancer therapy. In this review, we will discuss preclinical research and clinical trials involving metallic nanoparticles (MNPs) for cancer immunotherapy applications and discuss the potential for clinical translation of MNPs.
Mid-IR Spectral Investigation of Normal and Malignant Breast and Cervical Tissue Samples Using a Quantum Cascade Laser-Based Microscope
(2017-04-21) Haugen, Paul; Drezek, Rebekah; Tittel, Frank
Mid-infrared (MIR) spectroscopy has been a tool used to identify specific features of normal and malignant tissue samples by utilizing MIR characteristics, specifically in the “fingerprint” region. The fingerprint region is a biologically significant spectral region typically identified between 1500 and 500 cm-1. MIR spectroscopy can be used to study molecular changes and variations occurring in samples, which can then be used to fingerprint specific spectral characteristics and biomarkers in order to categorize the specimens. The most common instruments currently used in this analysis are Fourier transform infrared (FTIR) spectrometers, although properties inherent in these instruments, such as slow data collection time and an inability to specify sample location for the spectral data collection, have placed a ceiling on the clinical practicality of their use for specimen classification and identification. In this thesis, we use a prototype of an infrared hyperspectral imaging microscopy platform based around tunable quantum cascade laser (QCL) technology that has a spectral coverage from 1800-900 cm-1. The quantum cascade lasers are coupled with a series of MIR refractive objectives and an uncooled microbolometer camera. The speed of spectral imaging improves to 30 frames per second, and the high magnification objective has a 1.34 µm pixel resolution with a 0.70 numerical aperture and 4.3 µm spatial resolution. We are able to specify data collection at specific discrete wavelengths as opposed to the full spectrum, which improves the data collection time and de-clutters the data for analysis expediency. Finally, we perform spectral imaging real-time, which aides in selecting precise regions of interest on the target sample. This thesis demonstrates the advantages of exploiting the capabilities of the QCL microscope to advance MIR spectroscopy in the identification of distinguishing traits of normal and malignant breast and cervical tissue samples.
Optically-absorbing nanoparticles for enhanced tissue repair
(2004-02-03) West, Jennifer L.; Drezek, Rebekah; Sershen, Scott R.; Halas, Nancy J.; Rice University; United States Patent and Trademark Office
This invention is generally in the field of improved methods for the localized delivery of heat and the use thereof for the repair of tissue. The method involves localized induction of hyperthermia in tissue or materials by delivering nanoparticles to the tissue or materials and exposing the nanoparticles to an excitation source under conditions wherein they emit heat. The generation of heat effects the joining of the tissue or materials.
Rapid Stereomicroscopic Imaging of HER2 Overexpression in Ex Vivo Breast Tissue Using Topically Applied Silica-Based Gold Nanoshells
(Hindawi, 2012) Bickford, Lissett R.; Langsner, Robert J.; Chang, Joseph; Kennedy, Laura C.; Agollah, Germaine D.; Drezek, Rebekah; Bioengineering; Electrical and Computer Engineering
Tumor margin detection for patients undergoing breast conservation surgery primarily occurs postoperatively. Previously, we demonstrated that gold nanoshells rapidly enhance contrast of HER2 overexpression in ex vivo tissue sections. Our ultimate objective, however, is to discern HER2 overexpressing tissue from normal tissue in whole, nonsectioned, specimens to facilitate rapid diagnoses. Here, we use targeted nanoshells to quickly and effectively visualize HER2 receptor expression in intact ex vivo human breast tissue specimens. Punch biopsies of human breast tissue were analyzed after a brief 5-minute incubation with and without HER2-targeted silica-gold nanoshells using two-photon microscopy and stereomicroscopy. Labeling was subsequently verified using reflectance confocal microscopy, darkfield hyperspectral imaging, and immunohistochemistry to confirm levels of HER2 expression. Our results suggest that anti-HER2 nanoshells used in tandem with a near-infrared reflectance confocal microscope and a standard stereomicroscope may potentially be used to discern HER2-overexpressing cancerous tissue from normal tissue in near real time and offer a rapid supplement to current diagnostic techniques.
Simulation-guided tunable DNA probe design for mismatch tolerant hybridization
(Public Library of Science, 2024) Bugga, Pallavi; Asthana, Vishwaratn; Drezek, Rebekah
The ability to both sensitively and specifically assess the sequence composition of a nucleic acid strand is an ever-growing field. Designing a detection scheme that can perform this function when the sequence of the target being detected deviates significantly from the canonical sequence however is difficult in part because probe/primer design is based on established Watson-Crick base-pairing rules. We present here a robust and tunable toehold-based exchange probe that can detect a sequence with a variable number of SNPs of unknown identity by inserting a series of controlled, sequential mismatches into the protector seal of the toehold probe, in an effort to make the protector seal “sloppy”. We show that the mismatch-tolerant system follows predicted behavior closely even with targets containing up to four mismatches that thermodynamically deviate from the canonical sequence by up to 15 kcal/mole. The system also performs faithfully regardless of the global mismatch position on either the protector seal or target. Lastly, we demonstrate the generalizability of the approach by testing the increasingly mismatch-tolerant protectors on HIV clinical samples to show that the system is capable of resolving multiple, iteratively mutated sequences derived from numerous HIV sub-populations with remarkable precision.

Browsing by Author "Drezek, Rebekah"

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