Lymph-directed nitric oxide increases immune cell access to lymph-borne nanoscale solutes.

Lymph nodes (LNs) are immune organs housing high concentrations of lymphocytes, making them critical targets for therapeutic immunomodulation in a wide variety of diseases. While there is great interest in targeted drug delivery to LNs, many nanoscale drug delivery carriers have limited access to parenchymal resident immune cells compared to small molecules, limiting their efficacy. Nitric oxide (NO) is a potent regulator of vascular and lymphatic transport and a promising candidate for modulating nanocarrier access to LNs, but its lymphatic accumulation is limited by its low molecular weight and high reactivity. In this work, we employ S-nitrosated nanoparticles (SNO-NP), a lymphatic-targeted delivery system for controlled NO release, to investigate the effect of NO application on molecule accumulation and distribution within the LN. We evaluated the LN accumulation, spatial distribution, and cellular distribution of a panel of fluorescent tracers after intradermal administration alongside SNO-NP or a small molecule NO donor. While SNO-NP did not alter total tracer accumulation in draining lymph nodes (dLNs) or affect active cellular transport of large molecules from the injection site, its application enhanced the penetration of nanoscale 30 nm dextrans into the LN and their subsequent uptake by LN-resident lymphocytes, while nontargeted NO delivery did not. These results further extended to a peptide-conjugated NP drug delivery system, which showed enhanced uptake by B cells and dendritic cells when administered alongside SNO-NP. Together, these results highlight the utility of LN-targeted NO application for the enhancement of nanocarrier access to therapeutically relevant LN-resident immune cells, making NO a potentially useful tool for improving LN drug delivery and immune responses.