An official website of the United States government
Abstract 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.
more »
« less
Behavior of Neural Cells Post Manufacturing and After Prolonged Encapsulation within Conductive Graphene‐Laden Alginate Microfibers
Abstract 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.
more »
« less
- Award ID(s):
- 2014346
- PAR ID:
- 10360099
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Biology
- Volume:
- 5
- Issue:
- 11
- ISSN:
- 2701-0198
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract This work reports the dynamic behaviors of graphene aerogel (GA) microfibers during and after continuous wave (CW) laser photoreduction. The reduction results in one‐order of magnitude increase in the electrical conductivity. The experimental results reveal the exact mechanisms of photoreduction as it occurs: immediate photochemical removal of oxygen functional groups causing a sharp decrease in electrical resistance and subsequent laser heating that facilitates thermal rearrangement of GO sheets towards more graphene‐like domains. X‐ray and Raman spectroscopy analysis confirm that photoreduction removes virtually all oxygen and nitrogen containing functional groups. Interestingly, a dynamic period immediately following the end of laser exposure shows a slow, gradual increase in electrical resistance, suggesting that a proportion of the electrical conductivity enhancement from photoreduction is not permanent. A two‐part experiment monitoring the resistance changes in real‐time before and after photoreduction is conducted to investigate this critical period. The thermal diffusivity evolution of the microfiber is tracked and shows an improvement of 277 % after all photoreduction experiments. A strong linear coherency between thermal diffusivity and electrical conductivity is also uncovered. This is the first known work to explore both the dynamic electrical and thermal evolution of a GO‐based aerogel during and after photoreduction.more » « less
-
Chalmers, Jeffrey (Ed.)Droplet-based microfluidic devices have been used to achieve homogeneous cell encapsulation, but cells sediment in a solution, leading to heterogeneous products. In this technical note, we describe automated and programmable agitation device to maintain colloidal suspensions of cells. We demonstrate that the agitation device can be interfaced with a syringe pump for microfluidic applications. Agitation profiles of the device were predictable and corresponded to device settings. The device maintains the concentration of cells in an alginate solution over time without implicating cell viability. This device replaces manual agitation, and hence is suitable for applications that require slow perfusion for a longer period of time in a scalable manner.more » « less
-
Abstract Susceptibility of mammalian cells against harsh processing conditions limit their use in cell transplantation and tissue engineering applications. Besides modulation of the cell microenvironment, encapsulation of mammalian cells within hydrogel microbeads attract attention for cytoprotection through physical isolation of the encapsulated cells. The hydrogel formulations used for cell microencapsulation are largely dominated by ionically crosslinked alginate (Alg), which suffer from low structural stability under physiological culture conditions and poor cell–matrix interactions. Here the fabrication of Alg templated silk and silk/gelatin composite hydrogel microspheres with permanent or on‐demand cleavable enzymatic crosslinks using simple and cost‐effective centrifugation‐based droplet processing are demonstrated. The composite microbeads display structural stability under ion exchange conditions with improved mechanical properties compared to ionically crosslinked Alg microspheres. Human mesenchymal stem and neural progenitor cells are successfully encapsulated in the composite beads and protected against environmental factors, including exposure to polycations, extracellular acidosis, apoptotic cytokines, ultraviolet (UV) irradiation, anoikis, immune recognition, and particularly mechanical stress. The microbeads preserve viability, growth, and differentiation of encapsulated stem and progenitor cells after extrusion in viscous polyethylene oxide solution through a 27‐gauge fine needle, suggesting potential applications in injection‐based delivery and three‐dimensional bioprinting of mammalian cells with higher success rates.more » « less
-
Articular cartilage is comprised of two main components, the extracellular matrix (ECM) and the pericellular matrix (PCM). The PCM helps to protect chondrocytes in the cartilage from mechanical loads, but in patients with osteoarthritis, the PCM is weakened, resulting in increased chondrocyte stress. As chondrocytes are responsible for matrix synthesis and maintenance, it is important to understand how mechanical loads affect the cellular responses of chondrocytes. Many studies have examined chondrocyte responses to in vitro mechanical loading by embedding chondrocytes in 3-D hydrogels. However, these experiments are mostly performed in the absence of PCM, which may obscure important responses to mechanotransduction. Here, drop-based microfluidics is used to culture single chondrocytes in alginate microgels for cell-directed PCM synthesis that closely mimics the in vivo microenvironment. Chondrocytes formed PCM over 10 days in these single-cell 3-D microenvironments. Mechanotransduction studies were performed, in which single-cell microgels mimicking the cartilage PCM were embedded in high-stiffness agarose. After physiological dynamic compression in a custom-built bioreactor, microgels exhibited distinct metabolomic profiles from both uncompressed and monolayer controls. These results demonstrate the potential of single cell encapsulation in alginate microgels to advance cartilage tissue engineering and basic chondrocyte mechanobiology.more » « less
