The talk describes the design of amphiphilic silica nanoparticles for the stabilization of aqueous drops in fluorinated oils for droplet-based biochemical assays. Droplet microfluidics, in which nanoliter- to picoliter-sized drops are used to encapsulate molecules or cells, has enabled a wide range of high-throughput applications. The success of the technology has thus far relied on one type of surfactant (PFPE-PEG). These surfactants are known to have multiple limitations, however. First, they cause inter-drop transport of small, hydrophobic molecules. Such transport leads to the cross-contamination of droplet contents, and prevents the accurate interrogation of biochemical assays. A second limitation is their incompatibility with anchorage-dependent cell cultures, as the droplet surface laden with surfactants is too soft to support the growth of these cells. A third limitation is the difficulty in the chemical modification of the surfactant head groups.<br/>We found that these challenges can be resolved by replacing surfactants with fluorinated silica NPs (F-SiO2 NPs) as stabilizers. Since NPs do not form reverse micelles, which has been shown to play a predominant role on inter-drop molecular transport, cross-contamination in drops stabilized by NPs is mitigated. Our NP system is compatible with droplet generation and typical manipulations in droplet microfluidics. Furthermore, NPs-laden interfaces provide sufficient rigidity to support cell adhesion, spread and growth. We showed that our NP system supported the growth of epithelial and breast cancer cells. Finally, we have designed surface-functionalizable F-SiO2 NPs which allowed covalent conjugation of various designer molecules on the particle surface without compromising droplet stability.<br/>Our F-SiO2 NPs cost at least 20 times less than commercial PFPE-PEG surfactants. Our NP system thus has the potential to become a competitive alternative to current surfactant system critical for the success of droplet technology.<br/>

Amphiphilic nanoparticles as droplet stabilizers for high-fidelity droplet-based biochemical assays

253rd National Meeting (2017)

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