Rodrigues Patrícia M, Xavier Miguel, Calero Victor, Pastrana Lorenzo, Gonçalves Catarina
International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, 4715-330 Braga, Portugal.
University of Minho, Gualtar Campus, 4710-057 Braga, Portugal.
Micromachines (Basel). 2022 Apr 30;13(5):713. doi: 10.3390/mi13050713.
Polydimethylsiloxane (PDMS) is ubiquitously used in microfluidics. However, PDMS is porous and hydrophobic, potentially leading to small molecule partitioning. Although many studies addressed this issue and suggested surface/bulk modifications to overcome it, most were not quantitative, did not address which variables besides hydrophobicity governed molecule absorption, and no modification has been shown to completely obviate it. We evaluated qualitatively (confocal microscopy) and quantitatively (fluorescence spectroscopy) the effects of solute/solvent pairings, concentration, and residence time on molecule partitioning into PDMS. Additionally, we tested previously reported surface/bulk modifications, aiming to determine whether reduced PDMS hydrophobicity was stable and hindered molecule partitioning. Partitioning was more significant at lower concentrations, with the relative concentration of rhodamine-B at 20 µM remaining around 90% vs. 10% at 1 µM. Solute/solvent pairings were demonstrated to be determinant by the dramatically higher partitioning of Nile-red in a PBS-based solvent as opposed to ethanol. A paraffin coating slightly decreased the partitioning of Nile-red, and a sol-gel modification hindered the rhodamine-B diffusion into the PDMS bulk. However, there was no direct correlation between reduced surface hydrophobicity and molecule partitioning. This work highlighted the need for pre-assessing the absorption of test molecules into the microfluidic substrates and considering alternative materials for fabrication.
聚二甲基硅氧烷（PDMS）在微流控领域有着广泛应用。然而，PDMS具有多孔性和疏水性，这可能导致小分子的分配。尽管许多研究探讨了这个问题，并提出了表面/本体改性方法来克服它，但大多数研究都没有进行定量分析，没有涉及除疏水性之外哪些变量控制分子吸收，而且没有一种改性方法能完全消除这个问题。我们通过共聚焦显微镜进行定性评估，以及通过荧光光谱进行定量评估，研究了溶质/溶剂配对、浓度和停留时间对分子在PDMS中分配的影响。此外，我们测试了先前报道的表面/本体改性方法，旨在确定降低的PDMS疏水性是否稳定以及是否能阻碍分子分配。在较低浓度下分配现象更为显著，例如罗丹明 - B在20 μM时的相对浓度约为90%，而在1 μM时为10%。与乙醇相比，尼罗红在基于磷酸盐缓冲盐水（PBS）的溶剂中的分配显著更高，这表明溶质/溶剂配对起着决定性作用。石蜡涂层略微降低了尼罗红的分配，溶胶 - 凝胶改性则阻碍了罗丹明 - B扩散到PDMS本体中。然而，表面疏水性降低与分子分配之间没有直接关联。这项工作强调了在将测试分子吸收到微流控基板中之前进行预评估的必要性，并考虑使用替代材料进行制造。
