Advisory Committee Chair
Advisory Committee Members
Gary M Gray
Hubert M Tse
Date of Award
Degree Name by School
Doctor of Philosophy (PhD) College of Arts and Sciences
The development of polymeric delivery systems help overcome the intrinsic drawbacks of systemically-delivered therapeutic drugs, such as poor solubility and stability, multidrug resistance, inefficient accumulation in the diseased sites and unexpected toxicity to normal tissues. Polymeric vehicles possessing stimuli-sensitivity can prevent premature drug leakage and enable controlled cargo release. The modification with bioactive ligands aids to the accumulation of carriers in the targeted tissues to locally increase the concentration of therapeutics and decrease off-target toxicity. The manipulation of physical characteristics (e.g. size, shape) is also essential in the design of drug delivery systems since these properties play pivotal roles in regulating bio-system/particle interaction. Though extensive efforts have been devoted to establish the “intelligent” delivery platform, the preparation of stimuli-responsive shaped carriers is still synthetically challenging and the study to optimize their drug delivery capability and biological responses has been insufficiently explored. In this dissertation, a layer-by-layer strategy is applied to fabricate stimuli-responsive poly(methacrylic acid) (PMAA) hydrogels of precisely controlled shape and size for intracellular drug delivery and tumor targeting therapy. The effects of shape, size, ligand modification and cell type on the cellular uptake of shaped PMAA hydro-gels are investigated. The presented research covers the syntheses and modification of shaped hydrogels, the fundamental study of cell/hydrogel association, and the potential applications for anticancer drug delivery, with the ultimate aim of providing insight for the rational design of new smart systems for targeted drug delivery. Chapter 2 reports that a novel type of micrometer-sized PMAA hydrogel with disulfide links was engineered to have either spherical or cubical shape through the layer-by-layer technique. The hydrogels had pH-induced size variation and redox-triggered degradation, which expedited their application for intracellular delivery of an anticancer drug. Drug-loaded spherical hydrogels displayed 12% more cytotoxicity than their cubical counterparts in the first 10 h, suggesting more rapid internalization of spheres. The doxorubicin-loaded cubical hydrogels demonstrated 50% and 90% cytotoxicity to HeLa cells after 24 and 48 h, respectively, indicating successful drug delivery into the cancer cells. Chapter 3 presents a facile method to encapsulate a hydrophobic drug (7-(benzylamino)-3,4-dihydro-pyrrolo[4,3,2-de]quinolin-8(1H)-one, BA-TPQ) into PMAA hydrogel matrices. The resulting delivery platform maintained its cubical shape in solution, in the dry state, and upon lyophilization, demonstrating the robust structural stabil-ity and the potential application for shape-regulated drug delivery. The apparent perme-ability coefficient of BA-TPQ across Caco-2 cell monolayers was increased ~2-fold af-ter encapsulation within the hydrogels, suggesting a hydrogel-mediated increase in transepithelial transport of BA-TPQ. Hydrogel encapsulation amplified BA-TPQ potency via down-regulation of MDM2 oncogenic protein and upregulation of p53 and p21 expression in cancer cells, which improved the therapeutic effect of encapsulated BA-TPQ against liver cancer cells with a ~ 40% decrease in IC50 compared to that of free BA-TPQ and regardless of p53 status. Moreover, BA-TPQ-loaded hydrogels showed low toxicity to non-malignant hepatic cells (LO2 and CL48) with a >2-fold higher IC50 compared to that of hepatocellular carcinoma cells, suggesting good selectivity of the delivery system to cancer cells. In Chapter 4, the protocol to conjugate a bioactive peptide (IPLVVPL) to the PMAA hydrogel cubes to target hepsin-overexpressing tumor cells. The modified hydrogels had structural integrity and pH- and redox-triggered drug release. The submicron- and micron-sized PMAA hydrogel particles before and after peptide modification were utilized to investigate the cellular uptake of hydrogels. Flow cytometry experiments indicated that an increase in size could improve the internalization speed and extent of non-peptide-modified hydrogels in MCF-7 cells (hepsin-positive). 700 nm IPLVVPL-PMAA hydrogel particles showed a 2-fold higher internalization compared to PMAA hydrogels after 3 h incubation while the internalization of 2 µm particles was not improved after peptide modification, indicating a size regulated internalization effect. The cell internalization in different cell lines further confirmed the targeting ability of 700 nm IPLVVPL-PMAA hydrogels to hepsin-overexpressing tumors in which the hydrogel cellular uptake by MCF-7 and SK-OV-3 (hepsin-positive) were 3 to 10-fold higher than that of PC-3 (hepsin-negative) cells.
Xue, Bing, "Shaped Stimuli-Responsive Layer-By-Layer Hydrogels For Targeted Drug Delivery" (2018). All ETDs from UAB. 3393.