Speaker
Description
Introduction
Polymeric membranes, such as polyethylene terephthalate (PET), are widely used in Organ-on-a-Chip (OoC) systems due to their mechanical strength, porosity, and compatibility with microscopic analysis.[1] However, effective integration of these membranes into PDMS-based devices remains a technical challenge, as native PET does not readily bond with PDMS.[2] Surface modification is therefore necessary to ensure mechanical stability and functional integrity of the system during long-term culture and under flow conditions.
Methods
A two-layer poly(dimethylsiloxane) (PDMS) OoC system was developed, consisting of a top channel the culture of ovarian cancer cells and a bottom channel for the culture of non-malignant fibroblasts, separated by a thin porous PET membrane. To enhance bonding, PET membranes were surface-modified using two organosilanes: (3-Aminopropyl)triethoxysilane (APTES) and (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) at concentrations of 1% and 5% v/v. As an alternative approach, due to the potential cytotoxicity of silanes, a polydopamine coating was tested.. Surface modification was confirmed by water contact angle measurements and Fourier Transform Infrared Spectroscopy (FTIR). Bonding strength was evaluated by manual peeling and under continuous flow. Cytotoxicity was assessed using cell viability and morphology on modified membranes.
Results
Bonding efficiency varied with the type and concentration of silane. Microsystems modified with 5% silane exhibited stronger bonding, often tearing the PDMS during peeling, while 1% silane-bonded devices failed more predictably along PDMS–PET interfaces. Under flow, silane-modified devices failed at rates >5 µL/min, whereas polydopamine-modified systems remained sealed at up to 30 µL/min. Contact angle measurements confirmed successful surface modification: unmodified PDMS and PET showed high hydrophobicity (110° and 65°, respectively), while oxygen plasma treatment greatly increased hydrophilicity (30° and 25°). Subsequent silanization partially restored hydrophobicity (APTES ~45°, GPTMS ~35°), whereas polydopamine maintained low contact angles (~27°), indicating sustained hydrophilicity. In cytocompatibility assays, MTT tests performed on extracts from the modified membranes revealed no significant cytotoxicity. However, direct cell culture on silane-modified membranes showed limited cell adhesion and abnormal morphology, suggesting surface-related effects despite the absence of toxic leachables. In contrast, polydopamine-coated membranes supported abundant cells with normal morphology, indicating superior biocompatibility and more favorable conditions for cell growth.
Discussion
Although the literature supports the use of APTES and GPTMS for polymer surface modification and PDMS bonding [3], our results suggest that the outcomes is not always consistent and may lead to cytotoxic effects, possibly due to residual unreacted silane or non-uniform coating. Polydopamine offered a more reproducible and biocompatible alternative, ensuring strong bonding and healthy cell growth under flow conditions.
Acknowledgemets
The research was financially supported by the National Science Center (Poland), OPUS 21 no. 2021/41/B/ST4/01725.
References
[1] Schneider, S., et al., “Membrane integration into PDMS-free microfluidic platforms for organ-on-chip and analytical chemistry applications.” Lab on a Chip, 2021, 21, 1866
[2] Tang L, Lee NY. “A facile route for irreversible bonding of plastic-PDMS hybrid microdevices at room temperature”, Lab Chip. 2010;10(10):1274–80.
[3] Sip CG, Folch A. “Stable chemical bonding of porous membranes and poly(dimethylsiloxane) devices for long-term cell culture”, Biomicrofluidics. 2014;8(3):1–9.
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