Accessible, fast and easy fabrication of hydrophilic-in-hydrophobic microdroplet arrays

PLoS One. 2022 Feb 25;17(2):e0263282. doi: 10.1371/journal.pone.0263282. eCollection 2022.

Abstract

Microdroplet arrays (MDAs) are powerful tools for digital immunoassays, high-throughput screening and single cell analysis. However, MDAs are usually produced with cleanroom processes, which are associated with high costs and low availability. Furthermore, in order to obtain robust and stable MDAs based on hydrophilic spots surrounded by a hydrophobic background, the chemistry must be strictly controlled, which is challenging using shared equipment. Here, we developed a new method to fabricate MDA substrates independently from the cleanroom. A small and low-cost in-house built system to collimate the light source was assembled for photopatterning a negative resist, and spots with diameters down to 4 μm were obtained, with only 3% to 5% spot-to-spot variation across the same sample and high batch-to-batch reproducibility. The use of a negative photoresist enabled the formation of a hydrophobic coating in solution which yielded high-quality MDAs. The feasibility for carrying out digital assays was demonstrated by measuring anti-Tau antibody in sample buffers containing bovine serum albumin, with no noticeable surface fouling. The reported, robust, cost-effective, and fast process could hence lower the threshold to fabricate and use MDAs for digital immunoassays and other microcompartmentalization-based applications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Glass / chemistry
  • High-Throughput Screening Assays / methods*
  • Hydrophobic and Hydrophilic Interactions
  • Immunoassay / methods*
  • Light
  • Microarray Analysis / methods*
  • Optical Imaging
  • Serum Albumin, Bovine / chemistry
  • Single-Cell Analysis / methods*
  • Substrate Specificity / genetics

Substances

  • Serum Albumin, Bovine

Grants and funding

We like to thank the following funding sources: BBDiag, H2020-MSCA-ITN-2016, project no 721281 (MD is grant holder) https://ec.europa.eu/info/funding-tenders/opportunities/portal/screen/home, Danish Research Council grant number 8022-00160B (MD is grant holder) https://ufm.dk The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.