Transparent 3D-printable biointeractive surfaces enable real-time oral biofilm investigation under controlled flow

To identify a transparent, directly 3D-printable material (CYTO) capable of recapitulating hydroxyapatite (HA)-associated bacterial attachment while enabling real-time microfluidic investigation of oral biofilms under controlled flow conditions.

Smooth and rough polydimethylsiloxane (sPDMS and rPDMS, respectively), CYTO, and sintered HA were characterized in terms of surface morphology, roughness, wettability, surface energy, and protein adsorption. Enterococcus faecalis attachment was assessed under conventional flow chamber conditions and within a transparent microfluidic chip enabling real-time observation. A 3D-printed root canal platform incorporating accessory canal structures was further developed to evaluate irrigant-mediated bacterial removal under hydrodynamic conditions.

CYTO exhibited substantially greater protein adsorption (44.13 ± 2.57 µg/mL) than sPDMS (6.55 ± 2.80 µg/mL) and rPDMS (11.21 ± 1.56 µg/mL). Bacterial attachment on CYTO was significantly greater than on both PDMS surfaces and approached that observed on HA. The transparent microfluidic platform enabled continuous visualization and temporal mapping of bacterial attachment under flow, with spatially heterogeneous colonization patterns. In the root canal model, sodium hypochlorite irrigation achieved approximately 90% bacterial removal in accessory canals ≥ 300 μm in width, whereas lower removal was observed in 100-200 μm canals.

CYTO more closely replicated the biointeractive behavior of HA than conventional PDMS-based materials while maintaining optical transparency and direct printability. The developed platform enables real-time oral biofilm analysis and hydrodynamically controlled irrigation studies in complex geometries, providing an experimental approach beyond conventional static biofilm models and PDMS-based microfluidic systems.