LAUSR

It is well known that neutrophil-mediated delivery of therapeutic agents is a promising method for treating tumors. However, owing to the limited number and limited uptake ability of neutrophils, determining a reasonable dose has become an urgent problem to be solved. Furthermore, the number of nanoparticles is far greater than the number of neutrophils at normal doses, which causes excessive nanoparticles to reach nontargeted organs or tissues, leading to serious adverse effects. To address these problems, a neutrophil-targeting delivery system (DiR-DADGC-L) based on DiR-labeled and butanedioic acid (DA)-linked 5-amino-3,5-dideoxy-D-Glycerol-D-galactonanulose-cholesterol conjugate (DADGC) was designed to improve the efficiency of hitchhiking neutrophils through the specific binding of sialic acid (SA) to L-selectin (SA-binding receptor, expressed on neutrophils). DiR-DADGC-L was prepared with favorable particle size and encapsulation efficiency (%EE) to deliver DiR into neutrophils. Subsequently, diverse doses of DiR-DADGC-L were injected intravenously into S180 tumor-bearing and cyclophosphamide-depleted (CTX-D) S180 tumor-bearing mice to evaluate the in vivo behavior of liposomes. The results verified the following: a) The content of DiR-DADGC-L in neutrophils accounts for approximately 14.5% of the content of DiR-DADGC-L in plasma, and the uptake capacity of neutrophils remains unchanged under different doses, and b) both neutrophils and the enhanced permeability and retention (EPR) effect might exert significant roles in tumor treatment. As for the neutrophil-mediated delivery system, higher doses are not necessarily appropriate, and a lower dose may achieve an unexpected effect. It will be wise to determine an optimum dose to improve delivery efficiency.