Polydimethylsiloxane (PDMS) is a polymer widely used for fabrication and prototyping of microfluidic chips. The porous matrix structure of PDMS allows small hydrophobic molecules including some fluorescent dyes to be readily absorbed to PDMS and results in high fluorescent background signals, thereby significantly decreasing the optical detection sensitivity. This makes it challenging to accurately detect the fluorescent signals from samples using PDMS devices. Here, we have utilized polytetrafluoroethylene (PTFE) to inhibit absorption of hydrophobic small molecules on PDMS. Nile red was used to analyze the effectiveness of the inhibition and the absorbed fluorescence intensities for 3% and 6% PTFE coating (7.7 ± 1.0 and 6.6 ± 0.2) was twofold lower compared to 1% and 2% PTFE coating results (17.2 ± 0.5 and 15.4 ± 0.5). When compared to the control (55.3 ± 1.6), it was sevenfold lower in background fluorescent intensity. Furthermore, we validated the optimized PTFE coating condition using a PDMS bioreactor capable of locally stimulating cells during culture to quantitatively analyze the lipid production using Chlamydomonas reinhardtii CC-125. Three percent PTFE coating was selected as the optimal concentration as there was no significant difference between 3% and 6% PTFE coating. Intracellular lipid contents of the cells were successfully stained with Nile Red inside the bioreactor and 3% PTFE coating successfully minimized the background fluorescence noise, allowing strong optical lipid signal to be detected within the PDMS bioreactor comparable to that of off-chip, less than 1% difference.
Bibliographical noteFunding Information:
J.P.Funding:and J.Y.Thiswroteworkthewaspaper.supportedAll authorsby Shenzhenhave readScientificand agreedresearchto thegrantpublished(JCYJ20180504165801830) version of the manuscript. of China. This work was also supported by Regional Specialized Industry Development Program funded by the Ministry of SMEs and Startups (Project Number: S2933804). Funding: This work was supported by Shenzhen Scientific research grant (JCYJ20180504165801830)
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Fluorescence absorption inhibition
- Nile red
- PDMS surface modification
- PTFE coating
ASJC Scopus subject areas
- Analytical Chemistry
- Information Systems
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering