Chemical and Biomolecular Engineering - Theses
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ItemEngineering of DNA Micro- and Nanoparticles: Towards Vaccine Delivery( 2021)Vaccines are an effective tool for preventing and controlling various diseases by inducing adaptive immunity. Nanomaterials play an important role in vaccine development. Micro- and nanocarriers can be engineered to improve the therapeutic efficacy of vaccines by (i) preventing the degradation and systemic clearance of vaccine antigens and (ii) facilitating the uptake of vaccines in antigen-presenting cells (iii) co-delivering adjuvants and antigens at desired intracellular compartments for optimal immunotherapy. However, it is important to engineer a carrier that is both effective and safe. Micro- and nanoparticles based on DNA have shown great potential for biological applications, owing to the programmable sequences, predictable interactions, versatile modification sites, and high biocompatibility of DNA strands. This thesis aims to develop facile strategies to synthesize DNA particles for vaccine delivery by self-assembly approaches. First, a simple strategy to synthesize DNA microcapsules is reported. The cytosine-phosphate-guanosine oligodeoxynucleotides (CpG) motif is an efficient vaccine adjuvant that can effectively stimulate the immune system to secrete cytokines. By loading and crosslinking Y-shaped DNA building blocks (containing CpG motifs) into sacrificial calcium carbonate templates, monodisperse and spherical DNA capsules were obtained. These DNA microcapsules were internalized into cells efficiently, accumulated in endosomes, and induced immune cells to secrete high-level of cytokines. Next, we developed a template-assisted and versatile approach for synthesizing a new set of multifunctional particles through the supramolecular assembly of tannic acid (TA) and DNA molecules. Uniform and stable DNA-TA particles with different morphologies could be easily synthesized by using different types of DNA strands. Intriguingly, different DNA sequences can be encoded into this DNA-TA particle for applications in immunotherapy or gene delivery. The incorporation of CpG motifs and ovalbumin into the particles allows the intracellular antigen/adjuvant co-delivery to amplify cytokines production in macrophages, through synergistic effects. In addition, green fluorescent protein (GFP)-expressing plasmid DNA could be transfected by using the DNA-TA particles in HEK293T cells. Finally, nanometer-sized particles were engineered by exploiting the one-pot supramolecular assembly of TA, DNA, and PEG for intracellular delivery of CpG motifs. TA-DNA-PEG nanoparticles with different sizes could be fabricated by adding different molecular weight PEG chains. TA-DNA nanoparticles with tunable size were also synthesized by varying the molar ratio of TA and DNA. The obtained nanoparticles can enhance the cellular uptake of CpG oligonucleotides and consequently the production of cytokines in macrophages. Overall, the engineered DNA-based particles have potential for co-delivering nucleic acids and protein antigens in immune cells to enhance the immunological response against infectious diseases and cancer.
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ItemNanoengineered switchable, multi-responsive carriers for biomedical applications( 2014)Recent progress in material science and nanotechnology has enabled the design of next-generation drug delivery carriers. The implementation of such delivery systems has the potential to significantly enhance the current treatment outcomes, owing to their ability to achieve targeted bio-distribution and enhanced drug payloads. To develop the next generation of drug carriers, it is critical to incorporate a stimuli-responsive trigger into the material design. This allows for the development of “smart” carriers, which can load and release therapeutics in a specific targeted site on demand. Poly(2-diisopropylaminoethyl methacrylate) (PDPA) is a stimuli-responsive polymer that undergoes reversible hydrophobic-hydrophilic phase transition at biological-relevant pH variations. The incorporation of PDPA in the drug delivery systems opens a new route toward advanced drug delivery applications. This thesis focuses on developing several bottom-up approaches to assemble PDPA-based stimuli-responsive delivery systems from a material science perspective. By utilizing Layer-by-Layer (LbL) and self-assembly techniques, switchable, multifunctional systems that responded to various cellular conditions were synthesized. Charge-shifting PDPA capsules were synthesized via LbL assembly and cross-linked using a redox-responsive cross-linker. Dual stimuli-responsive cargo release profiles by pH and redox change were assessed in simulated intracellular conditions. Intracellular degradation kinetics of these capsules was investigated. The tuning of degradation kinetics was achieved by varying the degree of cross-linking density in the capsules, as confirmed by radio scintillation counting. Novel cross-linker free PDPA capsules were later developed. It was found that these capsules could improve the loading ability of drugs as small as 500 Da, and rapidly deconstruct and release cargo upon cellular uptake. Moreover, utilizing self-assembly techniques, multifunctional nanoparticles were synthesized from blending PDPA with an anti-cancer drug and a cell penetrating peptide. By varying the loading ratio in the nanoparticles, tunable cytotoxicity up to 30-fold was achieved. The reported PDPA-based responsive carriers are expected to provide fundamental insights towards the rational deign and synthesis of advanced delivery systems.