The human oral mucosa hosts a diverse microbiome and is exposed to potentially toxic biomaterials from dental restoratives. Mucosal health is partly determined by cell and tissue responses to challenges such as dental materials and pathogenic bacteria. An in vitro model to rapidly determine potential layer-specific responses would lead to a better understanding of mucosal homeostasis and pathology. Therefore, this study aimed to develop a co-cultured microfluidic mucosal model on-a-chip to rapidly assess mucosal remodeling and the responses of epithelial and subepithelial layers to challenges typically found in the oral environment. A gingival fibroblast-laden collagen hydrogel was assembled in the central channel of a three-channel microfluidic chamber with interconnecting pores, followed by a keratinocyte layer attached to the collagen exposed in the pores. This configuration produced apical and subepithelial side channels capable of sustaining flow. Keratinocyte, fibroblast, and collagen densities were optimized to create a co-culture tissue-like construct stable over one week. Cells were stained and imaged with epifluorescence microscopy to confirm layer characteristics. As proof-of-concept, the mucosal construct was exposed separately to a dental monomer, 2-hydroxylethyl methacrylate (HEMA), and the oral bacteria Streptococcus mutans. Exposure to HEMA lowered mucosal cell viability, while exposure to the bacteria lowered transepithelial electrical resistance. These findings suggest that the oral mucosa-on-achip is useful for studying oral mucosal interactions with bacteria and biomaterials with a histology-like view of the tissue layers.

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the relationships within microbiomes and the interactions between microbiome and host in a well-controlled and spatially analogous manner is of great interest in microbiome engineering and developing new biological technologies. [4] Microfluidic platforms have been of great interest for cellular studies in the last two decades. Recent transition from two dimensional (2D) to three dimensional (3D) cell culture in microfluidics provides the ability to control and monitor in vitro interactions between cells and extracellular matrix, establish stable chemical gradients and stimuli, deliver oxygen and nutrients, and to remove metabolites and reduce shear stress by laminar flows. [5] For example, natural and synthetic calcium alginate hydrogels were assembled into 3D geometries with high aspect ratio and curvature by combination of laser ablation and sacrificial molding technique. [4b,c] Calcium alginate with target cells was electrodeposited on electrodes or flow-assembled in microfluidics to model biofilms or construct synthetic ecosystems with spatiotemporal programmability. [6] Great advances have been made in organ-on-a-chip systems and synthetic systems that enable spatially controlled cocultures of cells and model various biological events including cancer metastasis and vascular functions. [7] The vast majority of microbial models or the microbehost systems, however, are limited to mixed or binary cultures that either are challenging if not impossible to track changes occurring in individual populations, or lack the compatibility to deliver different nutrients for different species. Challenges remain in culturing cells with a spatial resolution that can be used to study complex interactions between multiple species within microbial communities.This study presents, for the first time, the concept of fluitrodes to conveniently embed multiple cell populations in 3D hydrogels in microfluidics with a spatial resolution of biological relevance. The fluitrodes are freestanding biopolymer membranes that, like electrodes in transmitting electrons, transmit ions and small molecules with spatiotemporal programmability. Since biology information is mainly transmitted via ions and small molecules rather than electrons, the fluitrodes provide a novel platform to communicate with cell populations through ions and molecules in aqueous condition complementary to the communication in solids through an electrode. The spatially patterned cell populations were assembled either side by side or layer by layer in Modeling the complex interactions among organisms found within microbiomes is of great interest for the development of new biological technologies. Challenges remain in culturing cells of multiple species with spatial resolutions similar to microbial communities. Here, a fluitrode concept in microfluidics using biofabrication of functional biopolymers is demonstrated to efficiently assemble multiple cell populations in 3D hydrogels of spatial and biological relevance. The fluitrodes are freestanding biopolymer membranes...