Biocompatible polysaccharide-based hydrogels for attracting and trapping invasive glioma cells

Glioblastoma multiforme (GBM) is the most common deadly and aggressive malignant brain tumour of the central nervous system in humans. The relentless progression of this disease is due to the infiltration of the cells from the primary tumour site into distant regions of the brain, which renders complete resection of the tumour impossible leading to tumour recurrence. Current methods of treatment including surgical removal, chemotherapy combined to radiotherapy are mainly unsuccessful because of the highly invading and resistant nature of these glial tumours. Therefore, there is an urgent need to develop new methods and understand the complex behaviour and microenvironment of glioblastoma tumours. The key challenge in successful glioblastoma treatment lies in destroying the cancer cells that invade the brain tissue and exist in the brain parenchyma after the removal of the primary tumour bed.

To date, strategies that have been used, suffer from several disadvantages, including the absence of molecules that naturally exist in the brain extracellular matrix and most importantly they lack from effective chemoattractants. Consequently, residual invasive tumour cells remain in the margins of the resection cavity, leading to inevitable tumour recurrence. Therefore, this thesis aims to shed light on and tackle the majority of different limitations of the conventional methods of GBM treatment. In order to address these challenges, we here investigated the use of 3D scaffolds such as hydrogels for attracting and trapping glioma cells. Particular attention was given to those based on polysaccharides such as hyaluronic acid (HA) and methylcellulose (MC). HA is one of the main components of the brain extracellular matrix and is implicated in tumour cell behavior, creating a microenvironment favourable for migration, proliferation and invasiveness of malignant cells. HA-based hydrogels were prepared by chemical crosslinking of HA with Adipic Acid Dihydrazide (ADH) or Bovine Serum Albumin (BSA) as crosslinkers using EDC/sulfo-NHS chemistry. In this work, the fabricated hydrogels were loaded with a chemokine at a concentration gradient in order to achieve the migration of glioma cells to the hydrogel matrix and with a chemotherapeutic drug in order to induce cell death. The chemokine that was used is the vasoactive peptide urotensin II (UII) which at a gradient concentration has demonstrated chemoattracting migratory effects on glioma cells. Herein, the chemoattraction was tested on hydrogels loaded with this chemokine peptide.

Moreover, the physicochemical and mechanical properties of the fabricated hydrogels were mainly characterised by swelling studies, Scanning Electron Microscopy, enzymatic degradation experiments, Differential Scanning Calorimetry, Infrared Spectroscopy and oscillatory rheology. In overall, hydrogels presented favourable physicochemical features and mechanical properties that can mimic those of the native brain tissue. Preliminary biological results showed that glioma cells could invade and migrate in response to the loaded chemoattractant UII in the matrix.