Oral-mucosa-on-a-chip Sensitivity to a Dental Monomer Exceeds Well-plate Monocultures

Objectives: Knowledge of human gingival cell responses to dental monomers is critical for development of new dental materials. Current testing standards do not recapitulate the multi-layered geometry of the gingiva, which might affect responses. To address this, a two-layer oral mucosa-on-a-chip was exposed to HEMA and compared to well-plate cultures.
Methods: A microfluidic chip was fabricated from polydimethylsiloxane plasma-bonded to a glass slide after molding on a photolithography mask. The device consisted of three channels 400 μm wide, in parallel and interconnected by 7x50 μm² pores. The construct was fabricated by injecting immortalized human gingival fibroblasts (HGFs) into the central channel with 4 mg/ml type I rat tail tendon collagen to form a cell-filled hydrogel, then keratinocytes (Gie-No3B11) into one side channel to form an epithelial layer adherent to collagen in the inter-channel pores. Chip-based co-cultures, Gie-No3B11, and HGF monolayers in well-plates were exposed to 2-hydroxylethyl methacrylate (HEMA) at 1.56-25mM for 24h, then stained using equivalent protocols with calcein AM/ethidium homodimer for cell viability and death analysis.
Results: In the chip, the live (ANOVA, F=6.4, p<0.01) and dead (ANOVA, F=9.4, p<0.01) metrics were altered after 24 h exposure to 6.25 and 25 mM HEMA. Chip parameter sensitivities to HEMA were -1.3%±0.3% live area fraction/mM HEMA (p<0.01), and 1.5±0.3 dead cells/mM HEMA (p<0.001). Metrics (i.e., number of viable cells) were altered (2-ANOVA, p<0.05) in Gie-No3B11 and HGF well-plate monocultures after 24 h exposure to 12.5 and 25 mM HEMA.
Conclusions: This indicates a greater sensitivity to HEMA of gingival cells in the chip than in well-plate monocultures.