Nanoscale Molecular Quantification of Stem Cell-Hydrogel Interactions

A common approach to tailoring synthetic hydrogels for regenerative medicine applications involves incorporating RGD cell adhesion peptides, yet assessing the cellular response to engineered microenvironments at the nanoscale remains challenging. To date, no study has demonstrated how RGD concentration in hydrogels affects the presentation of individual cell surface receptors. Here we studied the interaction between human mesenchymal stem cells (hMSCs) and RGD-functionalized poly(ethylene glycol) hydrogels, by correlating macro- and nanoscale single-cell interfacial quantification techniques. We quantified RGD unbinding forces on a synthetic hydrogel using single cell atomic force spectroscopy, revealing that short-term binding of hMSCs was sensitive to RGD concentration. We also performed direct stochastic optical reconstruction microscopy (dSTORM) to quantify the molecular interactions between integrin α5β1 and a biomaterial, unexpectedly revealing that increased integrin clustering at the hydrogel-cell interface correlated with fewer available RGD binding sites. Our complementary, quantitative approach uncovered mechanistic insights into specific stem cell-hydrogel interactions, where dSTORM provides nanoscale sensitivity to RGD-dependent differences in cell surface localization of integrin α5β1. Our findings reveal that it is possible to precisely determine how peptide-functionalized hydrogels interact with cells at the molecular scale, thus providing a basis to fine-tune the spatial presentation of bioactive ligands.

Expanding and optimizing 3D bioprinting capabilities using complementary network bioinks

A major challenge in three-dimensional (3D) bioprinting is the limited number of bioinks that fulfill the physicochemical requirements of printing while also providing a desirable environment for encapsulated cells. Here, we address this limitation by temporarily stabilizing bioinks with a complementary thermo-reversible gelatin network. This strategy enables the effective printing of biomaterials that would typically not meet printing requirements, with instrument parameters and structural output largely independent of the base biomaterial. This approach is demonstrated across a library of photocrosslinkable bioinks derived from natural and synthetic polymers, including gelatin, hyaluronic acid, chondroitin sulfate, dextran, alginate, chitosan, heparin, and poly(ethylene glycol). A range of complex and heterogeneous structures are printed, including soft hydrogel constructs supporting the 3D culture of astrocytes. This highly generalizable methodology expands the palette of available bioinks, allowing the biofabrication of constructs optimized to meet the biological requirements of cell culture and tissue engineering.

Adapting tissue-engineered in vitro CNS models for high-throughput study of neurodegeneration

Neurodegenerative conditions remain difficult to treat, with the continuing failure to see therapeutic research successfully advance to clinical trials. One of the obstacles that must be overcome is to develop enhanced models of disease. Tissue engineering techniques enable us to create organised artificial central nervous system tissue that has the potential to improve the drug development process. This study presents a replicable model of neurodegenerative pathology through the use of engineered neural tissue co-cultures that can incorporate cells from various sources and allow degeneration and protection of neurons to be observed easily and measured, following exposure to neurotoxic compounds – okadaic acid and 1-methyl-4-phenylpyridinium. Furthermore, the technology has been miniaturised through development of a mould with 6 mm length that recreates the advantageous features of engineered neural tissue co-cultures at a scale suitable for commercial research and development. Integration of human-derived induced pluripotent stem cells aids more accurate modelling of human diseases, creating new possibilities for engineered neural tissue co-cultures and their use in drug screening.