Laminar and turbulent flow effects in high-pressure homogenization of liposomes and perfluorocarbon nanoemulsions

Since flow characteristics are still largely unexplored for high-pressure homogenization, we
investigated particle break-up at different Reynolds numbers and transition ranges in two channels
(Y- and Z-channel). While the channel geometries are often treated as “black boxes”, opening the
channels and measuring their geometries allowed a detailed analysis of flow conditions. Transitions
from laminar to turbulent flow for pressures of 250–2,000 bar have measurable effects on the sizes of
perfluorocarbon (PFC)-nanoemulsion droplets emulsified by phospholipids processed simultaneously
in liposomal conformation. Laminar flow has a higher size-reducing rate with growing pressure
compared to turbulent flow and leads to a minimum in polydispersity. A density-driven sucrose
gradient allows differential analysis of size-reducing effects on liposomes and PFC-nanoemulsion droplets separately. Liposomes can be broken up in both laminar and turbulent flow at the same size reduction rate. In contrast, emulsion droplets have much smaller size reduction rates in turbulent flow and need sufficient emulsifiers, made available by liposomal break-up, to enable size decreases. ... mehrRepetitive homogenization is only effective for a limited number of cycles. Beyond this threshold,
size distributions remain similar or can be deteriorated because of increased particle collisions and
aggregation or coalescence effects.