Prasad Subramaniam

Synergistic Induction of Apoptosis in Brain Cancer Cells by Targeted Codelivery of siRNA and Anticancer Drugs

Multiple dysregulated pathways in tumors necessitate targeting multiple oncogenic elements by combining orthogonal therapeutic moieties like short-interfering RNAs (siRNA) and drug molecules in order to achieve a synergistic therapeutic effect. In this manuscript, we describe the synthesis of cyclodextrin-modified dendritic polyamines (DexAMs) and their application as a multicomponent delivery vehicle for translocating siRNA and anticancer drugs. The presence of β-cyclodextrins in our DexAMs facilitated complexation and intracellular uptake of hydrophobic anticancer drugs, suberoylanilide hydroxamic acid (SAHA) and erlotinib, whereas the cationic polyamine backbone allowed for electrostatic interaction with the negatively charged siRNA. The DexAM complexes were found to have minimal cytotoxicity over a wide range of concentrations and were found to efficiently deliver siRNA, thereby silencing the expression of targeted genes. As a proof of concept, we demonstrated that upon appropriate modification with targeting ligands, we were able to simultaneously deliver multiple payloads--siRNA against oncogenic receptor, EGFRvIII and anticancer drugs (SAHA or erlotinib)--efficiently and selectively to glioblastoma cells. Codelivery of siRNA-EGFRvIII and SAHA/erlotinib in glioblastoma cells was found to significantly inhibit cell proliferation and induce apoptosis, as compared to the individual treatments.

Generation of a Library of Non‐Toxic Quantum Dots for Cellular Imaging and siRNA Delivery

The development of non-toxic quantum dots and further investigation of their composition-dependent cytotoxicity in a high-throughput manner have been critical challenges for biomedical imaging and gene delivery. Herein, we report a rapid sonochemical synthetic methodology for generating a library of highly biocompatible ZnS-AgInS(2) (ZAIS) quantum dots for cellular imaging and siRNA delivery.

Graphite-Coated Magnetic Nanoparticles as Multimodal Imaging Probes and Cooperative Therapeutic Agents for Tumor Cells

An effective therapeutic approach against cancer typically requires the combination of several modalities, such as chemotherapy, radiation, and hyperthermia. In this regard, the development of multifunctional nanomaterial-based systems with combined therapeutic and molecular imaging capabilities has shown great potential but has not been fully explored. In particular, magnetic nanomaterials have been at the fore-front of cancer research as noninvasive imaging probes as well as multifunctional therapeutics. [1] For example, magnetic nanoparticles (MNPs) with appropriate surface modifications have been successfully applied to deliver therapeutic biomolecules, such as anticancer drugs, antibodies, and siRNAs, to target tumor cells or tissues. [2] Moreover, the unique physical and chemical properties of these magnetic nanostructures have enabled their wide applications in cancer imaging and therapy, including magnetic resonance imaging (MRI) and hyperthermia. [3] Promising advances have been made in synthesizing multifunctional MNPs from various materials, including metals, [4] metal oxides, [5] metal alloys, [6] and metal–graphitic-shell nanomaterials, [7] with different properties. However, current studies are mostly focused on the synthesis and characterization of materials with limited demonstration of their biomedical applications, like molecular imaging and therapy. As a result, research efforts towards developing MNP-based multimodal therapeutics to control the tumor microenvironment are highly limited and have not been fully explored. Therefore, in order to address the challenges of MNP-based therapeutics, as well as to narrow the gap between current nanoparticle-based multimodal imaging approaches and their clinical applications, there is a clear need to synthesize effective chemotherapeutic MNPs and to develop multimodal therapies for targeting specific oncogenes, thereby activating/deactivating corresponding key signaling pathways.

Variability in bioreactivity linked to changes in size and zeta potential of diesel exhaust particles in human immune cells

Acting as fuel combustion catalysts to increase fuel economy, cerium dioxide (ceria, CeO2) nanoparticles have been used in Europe as diesel fuel additives (Envirox™). We attempted to examine the effects of particles emitted from a diesel engine burning either diesel (diesel exhaust particles, DEP) or diesel doped with various concentrations of CeO2 (DEP-Env) on innate immune responses in THP-1 and primary human peripheral blood mononuclear cells (PBMC). Batches of DEP and DEP-Env were obtained on three separate occasions using identical collection and extraction protocols with the aim of determining the reproducibility of particles generated at different times. However, we observed significant differences in size and surface charge (zeta potential) of the DEP and DEP-Env across the three batches. We also observed that exposure of THP-1 cells and PBMC to identical concentrations of DEP and DEP-Env from the three batches resulted in statistically significant differences in bioreactivity as determined by IL-1β, TNF-α, IL-6, IFN-γ, and IL-12p40 mRNA (by qRT-PCR) and protein expression (by ELISPOT assays). Importantly, bioreactivity was noted in very tight ranges of DEP size (60 to 120 nm) and zeta potential (−37 to −41 mV). Thus, these physical properties of DEP and DEP-Env were found to be the primary determinants of the bioreactivity measured in this study. Our findings also point to the potential risk of over- or under- estimation of expected bioreactivity effects (and by inference of public health risks) from bulk DEP use without taking into account potential batch-to-batch variations in physical (and possibly chemical) properties.

Effects of a nanoceria fuel additive on the physicochemical properties of diesel exhaust particles.

Nanoceria (i.e., CeO2 nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency. Previously we have shown that the use of a commercial fuel additive Envirox™ in a diesel-powered electricity generator reduced emissions of diesel exhaust particle (DEP) mass and other pollutants. However, such additives are currently not permitted for use in on-road vehicles in North America, largely due to limited data on the potential health impact. In this study, we characterized a variety of physicochemical properties of DEPs emitted from the same engine. Our methods include novel techniques such as Raman spectrometry for analyzing particle surface structure and an assay for DEP oxidative potential. Results show that with increasing Envirox™ concentrations in the fuel (0×, 0.1×, 1×, and 10× of manufacturer recommended 0.5 mL Envirox™ per liter fuel), DEP sizes decreased from 194.6 ± 20.1 to 116.3 ± 14.8 nm; the zeta potential changed from -28.4 mV to -22.65 mV; DEP carbon content decreased from 91.8% to 79.4%; cerium and nitrogen contents increased from 0.3% to 6.5% and 0.2% to 0.6%, respectively; the ratio of organic carbon (OC) to elemental carbon (EC) increased from 22.9% to 38.7%; and the ratio of the disordered carbon structure to the ordered carbon structure (graphitized carbon) in DEPs decreased. Compared to DEPs emitted from 0×, 0.1×, and 1× fuels, DEPs from the 10× fuel had a lower oxidative potential likely due to the increased ceria content because pure ceria nanoparticles exhibited the lowest oxidative potential compared to all the DEPs. Since the physicochemical parameters tested here are among the determinants of particle toxicity, our findings imply that adding ceria nanoparticles into diesel may alter the toxicity of DEPs. The findings from the present study, hence, can help future studies that will examine the impact of nanoceria additives on DEP toxicities.