Development of an Injectable Hydrogel Platform to Capture and Eradicate Glioblastoma Cells with Chemical and Physical Stimuli

Glioblastoma multiforme (GBM) is the most aggressive type of primary brain tumor. Even after patients undergo maximum and safe surgical resection followed by adjuvant chemotherapy and radiation therapy, residual GBM cells form secondary tumors which lead to poor survival times and prognoses for patients. This tumor recurrence can be attributed to the inherent GBM heterogeneity that makes it difficult to eradicate the therapy-resistant and tumorigenic subpopulation of GBM cells with stem cell-like properties, referred to as glioma stem cells (GSCs). Additionally, the migratory nature of GBM/GSCs enable them to invade into the healthy brain parenchyma beyond the resection cavity to generate new tumors. In an effort to address these challenges of GBM recurrence, this research aimed to develop a biomaterials-based approach to attract, capture, and eradicate GBM cells and GSCs with chemical and physical stimuli. Specifically, it is proposed that after surgical removal of the primary GBM tumor mass, an injectable hydrogel can be dispensed into the resection cavity for crosslinking in situ. A combination of chemical and physical cues can then induce the migration of the residual GBM/GSCs into the injectable hydrogel to localize and concentrate the malignant cells prior to non-invasively abating them. In order to develop this proposed treatment, this dissertation focused on 1) characterizing and optimizing the thiol-Michael addition injectable hydrogel, 2) attracting and entrapping GBM/GSCs into the hydrogel with CXCL12-mediated chemotaxis, and 3) assessing the feasibility of utilizing histotripsy to mechanically and non-invasively ablate cells entrapped in the hydrogel. The results revealed that hydrogel formulations comprising 0.175 M NaHCO3(aq) and 50 wt% water content were the most optimal for physical, chemical, and biological compatibility with the GBM microenvironment on the basis of their swelling characteristics, sufficiently crosslinked polymer networks, degradation rates, viscoelastic properties, and interactions with normal human astrocytes. Loading the hydrogel with 5 µg/mL of CXCL12 was optimal for the slow, sustained release of the chemokine payload. A dual layer hydrogel platform demonstrated in vitro that the resulting chemotactic gradient induced the invasion of GBM cells and GSCs from the extracellular matrix and into the synthetic hydrogel with ameboid migration and myosin IIA activation. This injectable hydrogel also demonstrated direct therapeutic benefits by passively eradicating entrapped GBM cells through matrix diffusion limitations as well as decreasing the GBM malignancy and GSC stemness upon cancer cell-hydrogel interactions. Research findings revealed the hydrogels can be synthesized under clinically relevant conditions mimicking GBM resection in vitro, and hydrogels were distinguishable with ultrasound imaging. Furthermore, the synthetic hydrogel was acoustically active to generate a stable cavitation bubble cloud with histotripsy treatment for ablation of entrapped red blood cells with well-defined, uniform lesion areas. Overall, the results from this research demonstrate this injectable hydrogel is a promising platform to attract and entrap malignant GBM/GSCs for subsequent eradication with chemical and physical stimuli. Further development of this platform, such as by integrating electric cues for electrotaxis-directed cell migration, may help to improve the cancer cell trapping capabilities and thereby mitigate GBM tumor recurrences in patients.