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Three-dimensional tissue engineered constructs provide a platform to examine how the local extracellular matrix (ECM) contributes to the malignancy of cancers such as human glioblastoma multiforme. Improved resolution of how local matrix biophysical features impact glioma proliferation, genomic and signal transduction paths, as well as phenotypic malignancy markers would complement recent improvements in our understanding of molecular mechanisms associated with enhanced malignancy. Here, we report the use of a gelatin methacrylate (GelMA) platform to create libraries of three-dimensional biomaterials to identify combinations of biophysical features that promote malignant phenotypes of human U87MG glioma cells. We noted key biophysical properties, namely matrix density, crosslinking density, and biodegradability, that significantly impact glioma cell morphology, proliferation, and motility. Gene expression profiles and secreted markers of increased malignancy, notably VEGF, MMP-2, MMP-9, HIF-1, and the ECM protein fibronectin, were also significantly impacted by the local biophysical environment as well as matrix-induced deficits in diffusion-mediated oxygen and nutrient biotransport. Overall, this biomaterial system provides a flexible platform to explore the role biophysical factors play in the etiology, growth, and subsequent invasive spreading of gliomas.

There is an acute need for biomaterial tools that recreate the heterogeneous brain-tumor microenvironment. A microfluidic mixing tool is reported to encapsulate glioblastoma multiforme cells within miniaturized gelatin hydrogels containing overlapping patterns of tumor-inspired matrix signals. This approach permits in situ analysis of glioma cells at the molecular and genomic level as well as the potential for clinical insight.

Glioblastoma (GBM) is the most common and lethal form of brain cancer. Its high mortality is associated with its aggressive invasion throughout the brain. The heterogeneity of stiffness and hyaluronic acid (HA) content within the brain makes it difficult to study invasion in vivo. A dextran-bead assay is employed to quantify GBM invasion within HA-functionalized gelatin hydrogels. Using a library of stiffness-matched hydrogels with variable levels of matrix-bound HA, it is reported that U251 GBM invasion is enhanced in softer hydrogels but reduced in the presence of matrix-bound HA. Inhibiting HA–CD44 interactions reduces invasion, even in hydrogels lacking matrix-bound HA. Analysis of HA biosynthesis suggests that GBM cells compensate for a lack of matrix-bound HA by producing soluble HA to stimulate invasion. Together, a robust method is showed to quantify GBM invasion over long culture times to reveal the coordinated effect of matrix stiffness, immobilized HA, and compensatory HA production on GBM invasion.

Cell transplantation has emerged as the most promising therapy for restoring the scarred myocardium in the treatment of heart failure. However, clinical effi cacy of (stem) cell therapies is still limited by poor retention rate and survival of injected cells in the ischemic tissue. Here we present a new strategy to deliver microtissues in the treatment of heart dysfunction in order to improve the retention, survival, and integration of the delivered cells. For this purpose, we developed stimuli responsive biodegradable polymer constructs consisting of a thin fi lm of thermosensitive hydrogel coupled to a thin fi lm of non-responsive polymer. Due to the temperature responsive swelling behavior of the hydrogel layer, the bilayer polymer constructs can roll or unroll at will. Therefore they can potentially be used for effi cient encapsulation and protection of cell clusters during delivery, while under physiological conditions, the constructs, named cell wraps, can unroll and expose the delivered microtissue to the ischemic tissue.

The extracellular matrix (ECM) is critical in tumor growth and invasive potential of cancer cells. In glioblastoma tumors, some components of the native brain ECM such as hyaluronic acid (HA) have been suggested as key regulators of processes associated with poor patient outlook such as invasion and therapeutic resistance. Given the importance of cell-mediated remodeling during invasion, it is likely that the molecular weight of available HA polymer may strongly influence GBM progression. Biomaterial platforms therefore provide a unique opportunity to systematically examine the influence of the molecular weight distribution of HA on GBM cell activity. Here we report the relationship between the molecular weight of matrix-bound HA within a methacrylamidefunctionalized gelatin (GelMA) hydrogel, the invasive phenotype of a patient-derived xenograft GBM population that exhibits significant in vivo invasivity, and the local production of soluble HA during GBM cell invasion. Hyaluronic acid of different molecular weights spanning a range associated with cell-mediated remodeling (10, 60, and 500 kDa) was photopolymerized into GelMA hydrogels, with cell activity compared to GelMA only conditions (-HA). Polymerization conditions were tuned to create a homologous series of GelMA hydrogels with conserved poroelastic properties (i.e., shear modulus, Poisson's ratio, and diffusivity). GBM migration was strongly influenced by HA molecular weight; while markers associated with active remodeling of HA (hyaluronan synthase and hyaluronidase) were found to be uninfluenced. These results provide new information regarding the importance of local hyaluronic acid content on the invasive phenotype of GBM.

The radical polymerization of ethylene oxide (PEGylated) methacrylates in ionic media has been studied. Lithium salts interact with the monomer causing a significant increase in the propagation rate constant, kp, and also providing an ionic and highly viscous medium that sharply decreases the termination rate coefficient, kt. Both features make the polymerization reactions with lithium salts faster compared to the bulk monomer. The systems are studied by means of FT‐IR spectroscopy to identify the interactions between the monomer and the lithium salt. In addition, an extensive kinetic study by PLP‐SEC has been performed to study the influence of the lithium salt on kp and kt in the polymerization of these monomers. These results are compared to those obtained when ionic liquids are used as polymerization medium. magnified image