METHODS: Human and mouse RBCs were modified with light-responsive B12-drug conjugates using two methods, cell-surface external loading and internal loading. Phototherapeutic RBCs were subjected to in vitro assays of resilience and stability, including tests of hemolysis, osmotic and turbulence fragility, and morphology as well as examined after intravenous administration in mice.
RESULTS: Photo-cleavable probes and drugs tuned to specific wavelengths of light were readily synthesized and selectively released from RBCs. Both externally and internally loaded RBCs displayed properties analogous to their unloaded counterparts. RBCs that were internally or externally loaded with B12-drug/probe conjugates were assessed via intravital imaging and found to be stable for up to 2 hours in vivo (the maximum allowed time period for these experiments). In vivo light application using a laser applied to the mouse ear releases the photocleavable agent into the interstitium.
CONCLUSIONS: Our preliminary results have demonstrated feasibility and assessed the structure, function, and lifetime of Phototherapeutic RBCs in vitro and in vivo.