DNA-decorated phase-shift microdroplets enable programmable coalescence and gene transfection.

HYPOTHESIS: Phase-shift perfluorocarbon microdroplets (MDs) are a promising and flexible method for challenging applications in colloid science, such as customizing chemical reactions or enhancing tumor gene delivery efficiency. To achieve these goals, we focused on stable MDs made of a decafluoropentane (DFP) core and a dimethyldioctadecylammonium bromide (DDAB) lipid shell that binds DNA through electrostatic interactions to create DNA-MDs assemblies. EXPERIMENTAL: The MDs were obtained via ultrasound homogenization and decorated with complementary DNAs. Fluorescence, confocal microscopy, and dynamic light scattering methodologies were combined to measure the binding features driving DNA-MDs formation and their coalescing interactions. The effect of the DNA-MDs at the cell interface was evaluated by MTT viability assay and DNA transfection in tumor melanoma cells. FINDINGS: We defined the colloidal formulation of DNA-MDs, functional for both chemical and biomedical relevant applications. First, we identified the conditions that enable DNA-MDs to rapidly and selectively coalesce via oligonucleotide hybridization at the MDs interface. Then, we used DNA-MDs to efficiently enter nucleic acids into human melanoma cells, even within a two-step transfection protocol to promote intracellular DNA strand displacement. Our results could shed new light on conducting controlled reactions in small volumes, realizing microreactors, as well as designing consensus gene transfection strategies.