(E-198) Polymersomes as Chemotherapeutic Agents for Non-Invasive Treatment of Glioblastoma

Introduction:: The World Health Organization has deemed neurologic diseases as one of the largest global burdens. Even with limited treatment methods, the absolute number of deaths has increased by 39% over the last 30 years. The main reason for this treatment gap is the blood-brain barrier (BBB), which protects the central nervous system from circulating pathogens. There is a high need for methods to deliver drugs to the brain, specifically in the case of brain cancer. Glioblastoma multiforme (GBM) is a grade IV, malignant brain tumor that accounts for over 45% of all CNS tumors. With an incidence rate of approximately 5 cases per 100,000 people, the average survival rate in the first year is 40%, with only 17% surviving after year 2. The GBM tumor microenvironment (TME) also has an upregulation of the hyaluronidase enzyme. Under the acidic conditions of the GBM TME, the hyaluronidase enzyme causes hydrolysis of hyaluronic acid, making it an optimum polymer choice for polymersomes to achieve stimuli-responsive degradation and drug delivery. The brain is often thought of as a primary site for cancer metastases because it provides a haven for cancer cells to hide from treatment behind the BBB and continue to grow. Improved drug delivery can be achieved through better delivery vehicles. In our lab, we have previously demonstrated the ability of polymersomes to penetrate the BBB after intravenous injection using receptor-mediated transcytosis. This project extends the use of functionalized polymersomes to actively target GBM for improved delivery efficacy of chemotherapeutic doxorubicin.

Materials and Methods:: In this study, we synthesized hyaluronic acid-block-poly (lactic acid) (HA-PLA) and used it to create functionalized polymersomes via solvent injection. In this study, we are optimizing the synthesis of HA-PLA polymersomes by varying the molecular weight of HA at 5, 7, and 9 kDa. Characterization of the polymersomes is performed using dynamic light scattering, transmission electron microscopy, and UV-Vis spectroscopy with doxorubicin (DOX). The encapsulation efficiency and loading capacity of the polymersomes are determined, and their drug release is evaluated by simulating the tumor environment using the hyaluronidase enzyme.

Results, Conclusions, and Discussions:: By increasing the size of HA, the hydrophilic fraction is increased. Our lab has previously proven the polymersome formulation of HA-PLA in varying molecular weight achieves sizes of less than or equal to 100 nm and negative zeta potential in the mid to high 20s, which is necessary for brain transport. Increasing the size of HA has an impact on both the size and encapsulation efficiency of the polymersomes when evaluating the loading of FITC-BSA as a model protein. While there is an inversely proportional relationship between HA molecular weight and encapsulation, the effect on size is less consistent. It is expected for the hydrodynamic diameter to decrease with increasing molecular weight. However, this is not the case for HA at nine kDa, likely due to more unbound polymer chains. We believe we will also see potential improvements in the encapsulation efficiency of DOX. Furthermore, changing the HA molecular weight changes the responsivity to hyaluronidase in the release of FITC-BSA, with an increase in molecular weight of HA leading to a decrease in a release from the polymersomes. CD44, a glycoprotein overexpressed in human GBM cells, was identified as a potential target for the HA-PLA polymersomes. HA, which plays a significant role in signaling pathways and tumor progression, can also be utilized to trigger enzyme release of DOX within the tumor microenvironment (TME).
The study demonstrated that varying the molecular weight of HA in the HA-PLA polymersome synthesis increased the hydrophilic fraction, improving the encapsulation efficiency of DOX. CD44 was identified as a potential target for the HA-PLA polymersomes, and HA was utilized to trigger the enzyme release of DOX within the TME. The increased expression of CD44 and hyaluronidase in the TME enhances the delivery of HA-PLA polymersomes, making them a promising candidate for drug delivery in GBM treatment. With further refinement and investigation, HA-PLA polymersomes have the potential to become an effective and targeted drug delivery system for brain cancer treatment, ultimately improving patient outcomes and quality of life.

Acknowledgements (Optional): :

References (Optional): : 1. Feigin, V. L. et al. The global burden of neurological disorders: translating evidence into policy. Lancet Neurol. 19, 255–265 (2020).

2. Wu, W. Glioblastoma multiforme (GBM): An overview of current therapies and mechanisms of resistance | Elsevier Enhanced Reader. Pharmacological Research https://reader.elsevier.com/reader/sd/pii/S1043661821003649?token=CD4CAF1AC5A59D9875608F24D4E05F23C296B6E77C4CF8D1E87C9B3806E7EA8DA7B75E6051ABAADBAF2CCEB83FA9CEB6&originRegion=us-east-1&originCreation=20220613161832 (2021).

3. Glioblastoma Multiforme – Symptoms, Diagnosis and Treatment Options. https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Glioblastoma-Multiforme.

4. Ho, V. K. Y. et al. Changing incidence and improved survival of gliomas. Eur. J. Cancer 50, 2309–2318 (2014).

5. Kesharwani, P., Chadar, R., Sheikh, A., Rizg, W. Y. & Safhi, A. Y. CD44-Targeted Nanocarrier for Cancer Therapy. doi:10.3389/fphar.2021.800481.