Biocompatibility Testing of UV-Curable Polydimethylsiloxane for Human Umbilical Vein Endothelial Cell Culture on-a-Chip

Abstract

Polydimethylsiloxane (PDMS) is extensively used to fabricate biocompatible microfluidic systems due to its favorable properties for cell culture. Recently, ultraviolet-curable PDMS (UV-PDMS) has shown potential for enhancing manufacturing processes and final optical quality while retaining the benefits of traditional thermally cured PDMS. This study investigates the biocompatibility of UV-PDMS under static and flow conditions using human umbilical vein endothelial cells (HUVECs). UV-PDMS samples were treated with oxygen plasma and boiling deionized water to assess potential improvements in cell behavior compared with untreated samples. We evaluated HUVECs adhesion, growth, morphology, and viability in static cultures and microchannels fabricated with UV-PDMS to test their resistance to flow conditions. Our results confirmed the biocompatibility of UV-PDMS for HUVECs culture. Moreover, plasma-oxygen-treated UV-PDMS substrates exhibited superior cell growth and adhesion compared to untreated UV-PDMS. This enhancement enabled HUVECs to maintain their morphology and viability under flow conditions in UV-PDMS microchannels. Additionally, UV-PDMS demonstrated improved optical quality and more efficient handling and processing, characterized by shorter curing times and simplified procedures utilizing UV light compared to traditional PDMS.

Figure 1

Setup of a circuit assembly for flow application on a microfluidic device. (A) Close-up view of the device and its connection to the medium reservoir bottle. (B) View of the circulation through the chip of the fluid coming from the pump and exiting through the medium reservoir. (C) Panoramic view showing the integration of the peristaltic pump, the chip, and the reservoir bottle in the circuit as a whole.

Figure 2

Cell adhesion. (A) Assessment of cell status at 3 h post-seeding in the different treatments. Three-grade scale: (+) low level, (++) intermediate level, and (+++) high level, as detailed in the Methods Section. (B) Representative images of the cell state at 3 h post-seeding. T1: normal production without treatment; T2: water boiling; and T3: oxygen plasma treatment. Control: standard polystyrene surface for cell culture.

Figure 3

Cell growth. (A) Representative images of cell state at 24 h post seeding in UV-PDMS (T1, T2, and T3) or in standard polystyrene surface for cell culture (control). (B) Cell area and number of cells in each condition. *p < 0.05 for the comparison with the control. T1: normal UV-PDMS without treatment, T2: UV-PDMS boiled with water, and T3: UV-PDMS treated with oxygen plasma.

Figure 4

Cell growth and maintenance. (A) Assessment of the cell growth trend in T1, T2, and T3. Three-grade scale: (+) low level, (++) intermediate level, and (+++) high level, as detailed in the Methods Section. (B) Representative images of cell growth at 72 h under phase contrast microscopy. T1: standard production without treatment; T2: water boiling; T3: oxygen plasma treatment; and control: polystyrene.

Figure 5

Optimization of oxygen plasma treatment (OPT). Representative images of cell growth in the comparative experiments with 60, 40, 20, and 10 s of the OPT (A–C,E–F) and the control in polystyrene (D,G). Scale bar is the same in all cases: 100 μm. Table with assessment of cell growth for the different OPT times (H). Number of cells on each condition after 24 h of culture (I), with columns representing the mean value of cells/area and s.e.m. by the bars.

Figure 6

Cell morphology adaptation. Representative images of the distribution of F-actin filaments stained with fluorescent-conjugated phalloidin (red) and nuclei, stained with Hoechst 33342 (blue), in the different surfaces. T1: standard production without treatment; T2: water-boiled; T3: oxygen plasma treatment; and control: polystyrene.

Figure 7

Cell culture under flow conditions. HUVECs nuclei stained with Hoechst 33342 in the main branch of the Y-shape channels, observed after exposure to the indicated flow rates for 6–7 h.