Impact of solvent choice during microfluidic manufacture on the in vivo performance of liposomal doxorubicin

Microfluidics offers a reproducible approach to liposome manufacture; however, the impact of solvent choice on formulation performance remains underexplored. Here, we investigated whether solvent selection during microfluidic manufacturing influences liposome performance by assessing its effect on the drug release and biodistribution of liposomal doxorubicin, using rotary evaporation as a conventional method of comparison. PEGylated liposomes (DSPC:Chol:DSPE-PEG2000, 3:1:1 w/w) were prepared using a staggered herringbone microfluidic mixer, with lipids dissolved in either ethanol or Transcutol, and compared with liposomes produced by rotary evaporation and extrusion. All formulations were actively loaded with doxorubicin via an ammonium sulphate gradient, purified by tangential flow filtration, and characterised for size, polydispersity, and drug loading. The three formulations (two microfluidic (ethanol vs Transcutol) and one rotary evaporation control) were intravenously administered to Sprague-Dawley rats (1 mg/kg), and doxorubicin concentrations in plasma and tissues were quantified using LC-MS. Although solvent choice produced liposomes with broadly comparable physicochemical properties (~ 100-120 nm, PDI < 0.25, encapsulation > 90%), Transcutol-based microfluidic liposomes showed prolonged and higher concentrations of doxorubicin within the plasma and tissue samples compared with liposomes produced by ethanol microfluidics and rotary evaporation. By contrast, the manufacturing method alone (microfluidics using ethanol as the solvent versus rotary evaporation) did not significantly influence biodistribution. These findings highlight solvent selection as an important parameter in microfluidic liposome manufacture, demonstrating that matching standard critical quality attributes and in vitro release behaviour alone may be insufficient to ensure comparable in vivo performance.