Enhancing the Conductivity of Cell-Laden Alginate Microfibers With Aqueous Graphene for Neural Applications

Abstract

Microfluidically manufacturing graphene-alginate microfibers create possibilities for encapsulating rat neural cells within conductive 3D tissue scaffolding to enable the creation of real-time 3D sensing arrays with high physiological relavancy. Cells are encapsulated using the biopolymer alginate, which is combined with graphene to create a cell-containing hydrogel with increased electrical conductivity. Resulting novel alginate-graphene microfibers showed a 2.5-fold increase over pure alginate microfibers, but did not show significant differences in size and porosity. Cells encapsulated within the microfibers survive for up to 8 days, and maintain ∼20% live cells over that duration. The biocompatible aqueous graphene suspension used in this investigation was obtained via liquid phase exfoliation of pristine graphite, to create a graphene-alginate pre-hydrogel solution.

Behavior of Neural Cells Post Manufacturing and After Prolonged Encapsulation within Conductive Graphene-Laden Alginate Microfibers

“…[16] Its structure of M- and G-blocks can be ionically crosslinked in the presence of divalant cations, such as Ca 2+ , Ba 2+ , Sr 2+ , and others; however, calcium crosslinkers are commonly used in biomedical applications because they are readily available and cost effective, and because calcium alginate hydrogels exhibit good swelling properties, which is important to maintain cell viability. [5, 6, 9, 35]…”

“…Briefly, the microfluidic channel features a main chamber which has dimensions of 130 μm x 390 μm, which holds four chevrons to allow for lateral shaping of the core fluid. [6, 9, 29, 30, 32] These chevrons are 200 μm apart and have dimensions of 130 μm x 100 μm.…”

“…There are a number of synthetic or carbon-based materials that can enhance the naturally low conductivity of alginate; these materials include synthetic polymers such as PEDOT:PSS, [13] silver nanowires, [14] graphite, [15, 16] graphene oxide, [17, 18] and pure graphene. [9, 18, 19] While pure graphene is favorable due to its extraordinary electrical, optical, biomedical, and mechanical properties, incorporating it into a stable aqueous pre-polymer solution for use with cell encapsulation is difficult, as the creation of graphene solutions typically requires the use of toxic or unstable chemicals, such as dimethylformamide (DMF) or N-methylpyyrolidone (NMP). [1, 20] Fortunately, bovine serum albumin (BSA), an edible protein, can be used to stabilize aqueous graphene solutions after exposing graphite to mechanical shear stress through liquid phase exfoliation (LPF).…”

“…[1, 20] Fortunately, bovine serum albumin (BSA), an edible protein, can be used to stabilize aqueous graphene solutions after exposing graphite to mechanical shear stress through liquid phase exfoliation (LPF). [1, 9, 21] This mitigated the need for cytotoxic chemicals to stabilize a graphene dispersion. In this study, shear stress was created through the use of a kitchen blender in a cost-effective and scalable method.…”

Protein-assisted scalable mechanochemical exfoliation of few-layer biocompatible graphene nanosheets

“…However, they found that hydrophilic graphene did not exhibit the harmful traits that hydrophobic graphene possessed. They concluded that surface functionalization is one of the salient factors that mitigate the cytotoxic characteristics of pristine graphene [62][63][64]. Since the hydrophobic portion of BSA is adsorbed on graphene, the hydrophilic part interacts with water and the surrounding environment promoting a benign interaction with cells.…”