sirolimus and propylene-sulfide

We show the first example of a synergic approach of oxidant (ROS) scavenging carrier and ROS-responsive drug release in the context of a potential therapy against osteoporosis, aiming to inhibit the differentiation of inflammatory cells into osteoclasts. In our "tandem" approach, a branched amphiphilic, PEGylated polysulfide (PPSES-PEG) was preferred over a linear analogue, because of improved homogeneity in the aggregates (spherical micelles vs mixture of wormlike and spherical), increased stability, and higher drug loading (up to ∼22 wt % of antiosteoclastic rapamycin). These effects are ascribed to the branching inhibiting crystallization in the polysulfide blocks. The ROS-scavenging micelles alone were already able to reduce osteoclastogenesis in a RAW 264.7 model, but the "drug" combination (the polymer itself + rapamycin released only under oxidation) completely abrogated the process. An important take-home message is that the synergic performance depended very strongly on the oxidant:oxidizable group molar ratio, a parameter to carefully tune in the perspective of targeting specific diseases.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antioxidants; Drug Carriers; Drug Liberation; Mice; Micelles; Nanomedicine; Osteoclasts; Osteogenesis; Oxidation-Reduction; RAW 264.7 Cells; Reactive Oxygen Species; Sirolimus; Sulfides