Characterization of Nanoscale Loaded Liposomes Produced by 2D Hydrodynamic Flow Focusing

This paper presents the continuous flow formation by two-dimensional (2D) hydrodynamic flow focusing (HFF) of nanosized liposomes in microfluidic systems. The size distribution and concentration of the nanosized liposomes, as well as the polydispersity index (PDI) and zeta potential (ZP) of the liposomal dispersions, were investigated under various flow rate ratios (FRRs) and lipid formulations, by the selective incorporation of either positively charged DDAB (didodecyl-dimethylammonium bromide) or negatively charged DOPG (1,2 dioleoyl-sn-glycero-3- phosphoglycerol) lipids to the main bilayer DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) constituent. The challenges of encapsulating an FITC (fluorescein isothiocyanate)-labeled LC-TAT peptide (long chain of transactivator of transcription peptide), which plays a direct role in the HIV regulation and transcription, overcame and could be achieved via one-step nanoliposomes synthesis, in order to validate the potential of this device as an all-in-one nanoparticle synthesis and loading platform. Liposomes with sizes ranging between 60 to 800 nm were produced with low polydispersity and high particle throughput from alteration of the flow rate ratio and lipid concentration. We introduced the use of nanoparticle tracking analysis (NTA) to estimate for the first time the throughput of microfluidic synthesized liposomal NPs by measuring quantitatively the concentration of the synthesized particles at the outlet. These measurements showed that stable and unilamellar liposomes are generated at a maximum concentration of 1740 × 108 particles/mL in less than 2 min, with higher FRR enabling the most rapid generation of liposomes with similar diameter and significant lower polydispersity index than those obtained by other batch techniques.