Date of Award
5-9-2025
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Blood-brain barrier (BBB) is a crucial neurovascular unit that maintains the homeostasis of the central nervous system but also poses a significant challenge for brain disease treatment and diagnosis. Focused ultrasound combined with microbubbles (FUSMB) has emerged as a promising technique for noninvasive, localized, transient and safe BBB opening, thereby enhancing both drug delivery for treatment and biomarker detection for diagnosis of brain diseases. Extensive research has demonstrated the potential of FUSMB-enhanced drug delivery to various brain diseases. The conventional treatment for diffuse intrinsic pontine glioma (DIPG) remains challenging due to the often-intact BBB, making FUSMB a strong candidate for DIPG drug delivery. In parallel, FUSMB-enhanced biomarker release for brain disease diagnosis has progressed rapidly, yet few studies have explored its broader applications such as gene therapy monitoring in the brain. Reporter genes used in gene delivery can serve as measurable biomarkers released by FUSMB, offering a safer alternative to radioactive tracers in nuclear imaging. Despite advances in applications, the biophysical mechanism of how FUSMB enhances agent transport remains unclear. Neither drug delivery outcomes in brain nor biomarker levels in plasma reveal the biophysical process during FUSMB treatment. Real-time capture of the FUSMB-enhanced agent transport is needed to better elucidate the mechanisms. My dissertation aims to leverage the FUSMB-enhanced agent transport for brainstem drug delivery and gene therapy monitoring, followed by biophysical mechanism study on the microscopic level. The research is divided into three specific aims. The first aim optimized the FUS sonication patterns, microbubble administration methods and FUS pressures for FUSMB treatment at the mouse brainstem. The optimized strategy achieved efficient, homogenous, and safe large volume drug delivery at the brainstem, providing guidance for future development of FUSMB treatment in DIPG. The second aim evaluated the capability of FUSMB to release biomarkers for monitoring gene delivery in the brain. Released biomarkers showed dependency on FUS pressure, enhancement on multiple molecular levels, and spatial concordance with the true expression in the targeted region, demonstrating FUSMB as a promising tool for gene delivery monitoring. The third aim investigated real-time interaction between FUSMB and agent transport in the mouse brain using in vivo two-photon microscopy. FUSMB induced vessel deformation at the affected vasculature, which was found to be highly correlated with the enhanced agent transport. This indicated that FUSMB-induced vessel deformation plays an important role in regulating the agent transport, providing valuable insights into the underlying mechanism. In conclusion, my thesis optimized FUSMB-enhanced brainstem drug delivery, characterized FUSMB-enhanced gene-therapy reporter release, and investigated real-time microscopic bioeffects, laying foundation to broaden applications and understand the mechanisms underlying FUSMB-enhanced agent transport in the brain.
Language
English (en)