The Effect of Size and Charge of Lipid Nanoparticles Prepared by Microfluidic Mixing on Their Lymph Node Transitivity and Distribution

TLDR

Lymph nodes are essential for initiating immune responses, and delivery of antigens or adjuvants to them is a promising strategy, but the size and charge of delivery vehicles, such as pH‑sensitive lipid nanoparticles produced by microfluidic mixing, are thought to influence their lymph node translocation and distribution, yet these effects remain unclear. This study aimed to determine how the size and surface charge of microfluidically prepared lipid nanoparticles affect their translocation to and distribution within lymph nodes. The authors fabricated lipid nanoparticles of 30, 100, and 200 nm diameter and of neutral, positive, and negative surface charge using microfluidic mixing, then assessed their lymph node accumulation and cellular uptake. They found that 30‑nm negatively charged nanoparticles translocated most efficiently to lymph nodes, were preferentially taken up by CD8⁺ dendritic cells, and reached the deep T‑cell zone, whereas larger or differently charged particles showed markedly reduced lymph node translocation, providing guidance for designing LN‑targeting nanoparticles.

Abstract

Because the lymph node (LN) is a critical organ for inducing immune responses against pathogens and cancers, the transport of immune functional molecules such as antigens and adjuvants to LNs by delivery systems is a useful strategy for the effective outcome of an immune response. The size and charge of a delivery system largely affect the transitivity to and distribution within LN. Although pH-sensitive lipid nanoparticles (LNPs) prepared by microfluidic mixing are the latest delivery system to be applied clinically, the effects of their size and charge on the transitivity to and distribution within LN are currently unknown. We investigated the size and charge effect of LNPs prepared by microfluidic mixing on transitivity to and distribution within LNs. A 30 nm-sized LNP (30-LNP) was efficiently translocated to LNs and was taken up by CD8+ dendritic cells, while the efficiency was drastically decreased in the cases of 100 and 200 nm-sized LNPs. Furthermore, a comparative study between neutral, positively, and negatively charged 30-LNP revealed that the negative 30-LNP moved to the LN more efficiently than the other LNPs. Interestingly, the negative 30-LNP reached the deep cortex, namely, the T cell zone. Our findings provide informative insights for designing LN-targeting LNPs prepared by microfluidic mixing and for the translocation of nanoparticles in LNs.