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Barrier functionality of the blood–brain barrier (BBB) is provided by the tight junctions formed by a monolayer of the human brain endothelial cells (HBECs) internally around the blood capillaries. To mimic such barrier functionality in vitro, replicating the hollow tubular structure of the BBB along with the HBECs monolayer on its inner surface is crucial. Here, we developed a microfluidic manufacturing technique to pattern the HBECs on the surface of alginate‐based microstructures. The HBECs were seeded on the inner surface of these hollow microfibers using a custom‐built microfluidic device. The seeded HBECs were monitored for 9 days after manufacturing and cultured to form a monolayer on the inner surface of the alginate hollow microfibers in the maintenance media. A higher cell seeding density of 217 cells/mm length of the hollow microfiber was obtained using our microfluidic technique. Moreover, high accuracy of around 96% was obtained in seeding cells on the inner surface of alginate hollow microfibers. The microfluidic method illustrated in this study could be extrapolated to obtain a monolayer of different cell types on the inner surface of alginate hollow microfibers with cell‐compatible ECM matrix proteins. Furthermore, it will enable us to manufacture a range of microvascular systems in vitro by closely replicating the structural attributes of the native structure.

 

The manufacturing of 3D cell scaffoldings provides advantages for modeling diseases and injuries as it enables the creation of physiologically relevant platforms. A triple‐flow microfluidic device is developed to rapidly fabricate alginate/graphene hollow microfibers based on the gelation of alginate induced with CaCl₂. This five‐channel microdevice actualizes continuous mild fabrication of hollow fibers under an optimized flow rate ratio of 300:200:100 µL min⁻¹. The polymer solution is 2.5% alginate in 0.1% graphene and a 30% polyethylene glycol solution is used as the sheath and core solutions. The biocompatibility of these conductive microfibers by encapsulating mouse astrocyte cells (C8D1A) within the scaffolds is investigated. The cells can successfully survive both the manufacturing process and prolonged encapsulation for up to 8 days, where there is between 18–53% of live cells on both the alginate microfibers and alginate/graphene microfibers. These unique 3D hollow scaffolds can significantly enhance the available surface area for nutrient transport to the cells. In addition, these conductive hollow scaffolds illustrate unique advantages such as 0.728 cm³ gr⁻¹porosity and two times more electrical conductivity in comparison to alginate scaffolds. The results confirm the potential of these scaffolds as a microenvironment that supports cell growth.

 

Mimicking microvascular tissue microenvironment in vitro calls for a cytocompatible technique of manufacturing biocompatible hollow microfibers suitable for cell‐encapsulation/seeding in and around them. The techniques reported to date either have a limit on the microfiber dimensions or undergo a complex manufacturing process. Here, a microfluidic‐based method for cell seeding inside alginate hollow microfibers is designed whereby mouse astrocytes (C8‐D1A) are passively seeded on the inner surface of these hollow microfibers. Collagen I and poly‐d‐lysine, as cell attachment additives, are tested to assess cell adhesion and viability; the results are compared with nonadditive‐based hollow microfibers (BARE). The BARE furnishes better cell attachment and higher cell viability immediately after manufacturing, and an increasing trend in the cell viability is observed between Day 0 and Day 2. Swelling analysis using percentage initial weight and width is performed on BARE microfibers furnishing a maximum of 124.1% and 106.1%, respectively. Degradation analysis using weight observed a 62% loss after 3 days, with 46% occurring in the first 12 h. In the frequency sweep test performed, the storage modulus (G′) remains comparatively higher than the loss modulus (G″) in the frequency range 0–20 Hz, indicating high elastic behavior of the hollow microfibers.

 

Thermoplastic resins (linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polypropylene (PP)) reinforced by different content ratios of raw agave fibers were prepared and characterized in terms of their mechanical, thermal, and chemical properties as well as their morphology. The morphological properties of agave fibers and films were characterized by scanning electron microscopy and the variations in chemical interactions between the filler and matrix materials were studied using Fourier-transform infrared spectroscopy. No significant chemical interaction between the filler and matrix was observed. Melting point and crystallinity of the composites were evaluated for the effect of agave fiber on thermal properties of the composites, and modulus and yield strength parameters were inspected for mechanical analysis. While addition of natural fillers did not affect the overall thermal properties of the composite materials, elastic modulus and yielding stress exhibited direct correlation to the filler content and increased as the fiber content was increased. The highest elastic moduli were achieved with 20 wt % agave fiber for all the three composites. The values were increased by 319.3%, 69.2%, and 57.2%, for LLDPE, HDPE, and PP, respectively. The optimum yield stresses were achieved with 20 wt % fiber for LLDPE increasing by 84.2% and with 30 wt % for both HDPE and PP, increasing by 52% and 12.3% respectively. 

Engineering conductive 3D cell scaffoldings offer advantages toward the creation of physiologically relevant platforms with integrated real‐time sensing capabilities. Dopaminergic neural cells are encapsulated into graphene‐laden alginate microfibers using a microfluidic approach, which is unmatched for creating highly‐tunable microfibers. Incorporating graphene increases the conductivity of the alginate microfibers by 148%, creating a similar conductivity to native brain tissue. The cell encapsulation procedure has an efficiency of 50%, and of those cells, ≈30% remain for the entire 6‐day observation period. To understand how the microfluidic encapsulation affects cell genetics, tyrosine hydroxylase, tubulin beta 3 class 3, interleukin 1 beta, and tumor necrosis factor alfa are analyzed primarily with real‐time reverse transcription‐quantitative polymerase chain reaction and secondarily with enzyme‐linked immunosorbent assay, immediately after manufacturing, after encapsulation in polymer matrix for 6 days, and after encapsulation in the graphene‐polymer composite for 6 days. Preliminary data shows that the manufacturing process and combination with alginate matrix affect the expression of the studied genes immediately after manufacturing. In addition, the introduction of graphene further changes gene expressions. Long‐term encapsulation of neural cells in alginate and 6‐day exposure to graphene also leads to changes in gene expressions.