Liquid marbles for high-throughput biological screening of anchorage-dependent cells

Stable liquid marbles (LM) are produced by coating liquid droplets with a hydrophobic powder. The used hydrophobic powder is produced by fl uorosilanization of diatomaceous earth, used before to produce superhydrophobic structures. Here, the use of LM is proposed for high-throughput drug screening on anchorage-dependent cells. To provide the required cell adhesion sites inside the liquid environment of LM, surface-modifi ed poly( L -lactic acid) microparticles are used. A simple method that takes advantage from LM appealing features is presented, such as the ability to inject liquid on LM without disrupting (self-healing ability), and to monitor color changes inside of LM. After promoting cell adhesion, a cytotoxic screening test is performed as a proof of concept. Fe 3+ is used as a model cytotoxic agent and is injected on LM. After incubation, AlamarBlue reagent is injected and used to assess the presence of viable cells, by monitoring color change from blue to red. Color intensity is measured by image processing and the analysis of pictures takes using an ordinary digital camera. The proposed method is fully validated in counterpoint to an MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-te trazolium) colorimetric assay, a well-known method used for the cytotoxicity assessment.This work was carried out under the scope of the EU 7th Framework Programme (FP7/2007-2013) under grant agreement no. FP7-KBBE-2010-4-266033 (SPECIAL). The work was also financially supported by the Portuguese Foundation for Science and Technology (FCT) project PTDC/CTM-BIO/1814/2012. N.M.O. and C.R.C. acknowledge the FCT for the PhD scholarships (SFRH/BD/73172/2010 and SFRH/BD/69529/2010, respectively)