Written by Grace Hu
Jérémie Caprasse, University of Liège
Microfluidic Shape-Memory Microparticles for Embolization System
Microfluidic techniques are elevating our ability to produce uniform immersion droplets and multifunctional materials. Jérémie Caprasse from the University of Liège has been refining his microfluidic formulation of shape-memory microparticles to serve as an embolization system. Embolization is a voluntary, minimally invasive procedure that involves the selective occlusion of blood vessels to gain medical benefits, such as controlling abnormal bleeding, inhibiting blood supply to a tumor, and treating aneurysms. Caprasse looks at modifying the hard and soft segments of shape-memory polymers, which fix the permanent and temporary shape of the material respectively, in response to thermal stimuli.
Caprasse aims to optimize the process of forming well-defined, monodisperse microparticles composed of 4-arm poly (ε-caprolactone) stars crosslinked by coumarin. He then tested a few conditions on his microparticle formulations and found that increasing the emulsifier concentration and/or decreasing the polymer flow led to smaller microparticle sizes (overall range of 50–150 µm). By performing differential scanning calorimetry, he also showed that the 38% crystallinity imparts shape memory such that the elastic material recovers its initial shape within 30 seconds. Ultimately, having tunable control of microparticle synthesis with shape memory is a promising technique for embolization applications.
Ryan Trueman, University College London
3D Aligned Engineered Living Conductive Neural Tissue
Severed nerve injuries are a major challenge for patients today since a stable connection is needed to bridge the gap. The gold standard treatment is to perform a surgical autograft, where a patient’s own nerve tissue from another site of the body is extracted to fill the gap. However, the surgical method has shown side effects of nerve loss at the donor site and poor recovery satisfaction. As such, a speaker filling in for Ryan Trueman said the research group aims to explore how electrical stimulation (ES) can be leveraged to promote nerve regeneration.
To do so, the research team has designed a composite scaffold of polymerized polypyrrole nanoparticles and fibrillar collagen processed through a technique known as gel aspiration-ejection. This conductive scaffold then served as a carrier for therapeutic Schwann cells to help bridge primary rat neurons that were seeded in as well. They demonstrated how the cell-laden constructs were able to align the Schwann cells and help maintain cell viability, where electrical stimulation also did not incur additional cell death. In fact, electrically stimulating the Schwann cells in the scaffold resulted in increased neurite extension in the monolayer, which shows potential for ES as a promising therapy for nerve regeneration in the future.
Daniel Verrico, Case Western Reserve University
Cell Encapsulation and Functionality in Engineered Living Microfibers by Uniaxial Electrospinning
Like humans settled into their home, a cell flourishes best in the comfortable microenvironment that they grow in. But how can we replicate complex in vivo conditions through in vitro geometric lattices? PhD student Daniel Verrico from Case Western Reserve University, in collaboration with researchers in the Lawrence Livermore National Laboratory, tries to tackle this problem by fabricating a novel poly(ethylene glycol) (PEG) scaffold for single cell encapsulation and bioprocess intensification. Here, Verrico used a novel uniaxial electrospinning approach to generate PEG microfibers, which were then characterized and loaded with viable yeast cells to facilitate mass transfer and increase production capacity.
Diving into the results, Verrico first showed how varying the initial concentration of aqueous poly(ethylene glycol) diacrylate (PEGDA) from 5 wt% to 15 wt% led to pretty consistent fiber diameters (0.7–0.9 µm), but at a cost of higher embrittlement. Rehydrating the scaffold also induced a thicker web-like structure with agglomerated morphology. To strengthen the gel, Verrico created dual network fibers composed of 5 wt% acrylamide and 0.5 wt% N, N′-methylenebisacrylamide, which helped reduce brittle behavior and improve elasticity.
Going forward, Verrico hopes to perform in situ photopolymerization to cure the electrospun material and evaluate impacts on morphological outcome. Overall, designing biomaterials to promote yeast cell functionality can help produce valuable products such as biofuels and pharmaceuticals, offering a strong candidate for biocatalyst production.