Enhanced and stabilized mesenchymal stem cell growth inside plasma pre-treated and collagen-coated PDMS-based microfluidic chambers

Poly(dimethylsiloxane) (PDMS) - based microfluidic devices, let them be lab-on-a-chip or organ-on-a-chip platforms, have been extensively utilized in biomedical research, due to the versatility, rapid prototyping, op-tical transparency and ease of fabrication. Despite its numerous advantages, PDMS is inherently hydrophobic, which compromises cell adhesion and proliferation, given the direct correlation between surface properties and cell viability. Various strategies have been followed for the functionalization of PDMS surface, from which extracellular matrix (ECM) protein immobilization appears to be more compatible with cell-related applications. In this context, current studies propose multi-step, tedious and occasionally environmentally hazardous pro-cedures of PDMS chemical functionalization that are additionally not easily employed in microfluidic systems. To overcome these limitations, this work suggests air plasma treatment as the single-step PDMS activation pro-cedure for the immobilization of type I collagen, and is one of the few to actually be applied inside microfluidic devices, at the integral fabrication step of sealing, to study cell sustainability. Stable hydrophilization of the plasma-treated and collagen-coated PDMS surfaces was verified for a time period of 7 days in dry state, achieving the highest reported wettability. Moreover, mesenchymal stem cells (MSCs) were cultured in as-treated 3D microchambers for 5 days, when they reached complete confluency, one of the highest reported in literature. The results revealed the potential of plasma treatment followed shortly after by collagen layering to support stabi-lized and long-term cell culture in PDMS-based microfluidic devices. The herein proposed PDMS surface func-tionalization method can be used to create a stable PDMS-collagen composite layer in organ-on-a-chip platforms.