Nano-carrier drug transport in blood microcirculation is one of the hotspots of current research
in drug development due to many advantages over traditional therapies, such as reduced sideeffects,
target delivery, controlled release, improved pharmacokinetics and therapeutic index. Despite
the substantial efforts made in the design of nanotherapeutics, the big majority of the used strategies
failed to overcome the biological barriers to drug transport encountered in human microvasculature,
such as transport by blood flow via the microcirculatory network and margination, the mechanism according
to which particles migrate along vessel radius to the wall. In fact, drug transport efficiency in
microvasculature is affected by both the particulate nature of blood and drug carrier properties, such as
size, shape and surface charge.
In this work, the effect of the surface charge of liposomes on their margination in blood flow in microcapillaries
was experimentally evaluated. By high-speed video microscopy and image analysis it was
found that the two custom-made liposomes (one neuter and the other positively charged) tend to drift
laterally, moving towards the wall and accumulating in the cell-free layer. In particular, neuter and cationic
liposomes showed a comparable margination propensity, suggesting that the presence of blood
cells governs the flow behavior independently on liposome surface charge.