Uniform sized cancer spheroids production using hydrogel-based droplet microfluidics: a review

Three-dimensional (3D) cell culture models have been extensively utilized in various mechanistic studies as well as for drug development studies as superior in vitro platforms than conventional two-dimensional (2D) cell culture models. This is especially the case in cancer biology, where 3D cancer models, such as spheroids or organoids, have been utilized extensively to understand the mechanisms of cancer development. Recently, many sophisticated 3D models such as organ-on-a-chip models are emerging as advanced in vitro models that can more accurately mimic the in vivo tissue functions. Despite such advancements, spheroids are still considered as a powerful 3D cancer model due to the relatively simple structure and compatibility with existing laboratory instruments, and also can provide orders of magnitude higher throughput than complex in vitro models, an extremely important aspects for drug development. However, creating well-defined spheroids remain challenging, both in terms of throughputs in generation as well as reproducibility in size and shape that can make it challenging for drug testing applications. In the past decades, droplet microfluidics utilizing hydrogels have been highlighted due to their potentials. Importantly, core-shell structured gel droplets can avoid spheroid-to-spheroid adhesion that can cause large variations in assays while also enabling long-term cultivation of spheroids with higher uniformity by protecting the core organoid area from external environment while the outer porous gel layer still allows nutrient exchange. Hence, core-shell gel droplet-based spheroid formation can improve the predictivity and reproducibility of drug screening assays. This review paper will focus on droplet microfluidics-based technologies for cancer spheroid production using various gel materials and structures. In addition, we will discuss emerging technologies that have the potential to advance the production of spheroids, prospects of such technologies, and remaining challenges.

Development of Crystalline Morphology and Its Relationship with Mechanical Properties of PP/PET Microfibrillar Composites Containing POE and POE-g-MA

The main goal of this research is to study the development of crystalline morphology and compare it to various mechanical properties of microfibrillar composites (MFCs) based on polypropylene (PP) and poly(ethylene terephthalate) (PET), by adding a functional compatibilizer and a non-functional rubber in two different steps in the processing sequence. The MFCs were prepared at a weight ratio of 80/20 PP/PET by twin screw extrusion followed by cold drawing and injection moulding. The non-functionalized polyolefin-based elastomer (POE) and the functional compatibilizer (i.e., POE grafted with maleic anhydride (POE-g-MA)) were added in a fixed weight percentage at two stages: during extrusion or during injection moulding. The morphology observations showed differences in crystalline structure, and the PP spherulite size was reduced in all MFCs due to the presence of PET fibrils. Their relationship with the mechanical performances of the composite was studied by tensile and impact tests. Adding the functional compatibilizer during extrusions showed better mechanical properties compared to MFCs. Overall, a clear relationship was identified between processing, structure and properties.

The performance and morphology of PMMA/SAN/ABS blends

Acrylonitrile-butadiene-styrene (ABS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene (St) and acrylonitrile (AN) on polybutadiene (PB) particles. Poly (methyl methacrylate) (PMMA)/styrene-acrylonitrile (SAN)/ABS blends were prepared by melt blending ABS graft copolymers with PMMA and SAN resins. The properties, morphology and grafted chains behaviors of PMMA/SAN/ABS blends were investigated. The results showed that with the increase of the ratio of PMMA/SAN, the toughness of PMMA/SAN/ABS blends slightly decreased, the transmittance first increased and then decreased, and tensile strength was not dependent on the ratio of PMMA/SAN. The evolution of impact strength of the blends was similar with the tendency of grafted degree (GD) with the increase of cumene hydroperoxide (CHP) and tert-dodecyl mercaptan (TDDM). From transmission electron microscopy (TEM), it was found that ABS graft copolymers were uniformly dispersed in PMMA/SAN matrix.

Toughening of an epoxy thermoset with poly[styrene-alt-(maleic acid)]-block-polystyrene-block-poly(n-butyl acrylate) reactive core–shell particles

Reactive core–shell particles for epoxy toughening were synthesized via reversible addition–fragmentation chain transfer emulsion polymerization mediated by an amphiphilic macro-RAFT agent followed by core-crosslinking to increase stability.

Balanced toughening and strengthening of ethylene–propylene rubber toughened isotactic polypropylene using a poly(styrene-b-ethylene–propylene) diblock copolymer

A new modified polypropylene material with both high toughness and strength was prepared and the synergistic effect was revealed.

Modification of the core–shell ratio to prepare PB-g-(MMA-co-St-co-GMA) particle-toughened poly(butylene terephthalate) and polycarbonate blends with balanced stiffness and toughness

Particles with a modified core–shell ratio provide an effective way to prepare polymer blends with a superior balance of toughness and stiffness.