In vitro comparison of liposomal drug delivery systems targeting the oxytocin receptor: a potential novel treatment for obstetric complications

Abstract

Introduction

Targeted intervention to the uterus has great potential for the treatment of obstetric complications (eg, preterm birth, dysfunctional labor, and postpartum hemorrhage) by improving the effectiveness and safety of therapeutic compounds. In particular, targeting the oxytocin receptor (OTR) is a novel approach for drug delivery to the uterus. The aim of this study was to report the complete data set for the pharmaceutical synthesis and in vitro characterization of PEGylated liposomes conjugated with anti-OTR monoclonal antibodies (OTR-Lipo) or atosiban (ATO-Lipo, OTR antagonist).

Methods

OTR-targeted liposomal platforms composed of 1,2-distearoyl-sn-glycero-2-phosphocholine and cholesterol were prepared according to the method of dried lipid film hydration. Ligands were conjugated with the surface of liposomes using optimized methods to maximize conjugation efficiency. The liposomes were characterized for particle size, ligand conjugation, drug encapsulation, liposome stability, specificity of binding, cellular internalization, mechanistic pathway of cellular uptake, and cellular toxicity.

Results

Both OTR-Lipo and ATO-Lipo showed significant and specific binding to OTRs in a concentration-dependent manner compared to all control groups. There was no significant difference in binding values between OTR-Lipo and ATO-Lipo across all concentrations evaluated. In addition, OTR-Lipo (81.61%±7.84%) and ATO-Lipo (85.59%±8.28%) demonstrated significantly increased cellular internalization in comparison with rabbit IgG immunoliposomes (9.14%±1.71%) and conventional liposomes (4.09%±0.78%) at 2.02 mM phospholipid concentration. Cellular association following liposome incubation at 4.05 mM resulted in similar findings. Evaluation of the mechanistic pathway of cellular uptake indicated that they undergo internalization through both clathrin- and caveolin-mediated mechanisms. Furthermore, cellular toxicity studies have shown no significant effect of both liposomal platforms on cell viability.

Conclusion

This study further supports OTRs as a novel pharmaceutical target for drug delivery. OTR-targeted liposomal platforms may provide an effective way to deliver existing therapies directly to myometrial tissue and avoid adverse effects by circumventing non-target tissues.

Keywords:

• liposomes
• nanoparticles
• targeted drug delivery
• oxytocin receptor
• uterus
• obstetric complications

Acknowledgments

This work was supported by the National Health and Medical Research Council, Hunter Medical Research Institute, Global Alliance to Prevent Prematurity and Stillbirth, Gladys M Brawn Fellowship, and University of Newcastle. This work was performed in part at the Materials node of the Australian National Fabrication Facility, which is a company established under the National Collaborative Research Infrastructure Strategy to provide nano and microfabrication facilities for Australian researchers.

Author contributions

SH contributed to study concept and design, liposome manufacturing and characterization, liposome imaging, cellular studies, analysis and interpretation of data, and drafting of manuscript. BV contributed to liposome imaging and analysis and interpretation of data. Both authors were involved in revising the article critically for important intellectual content and gave final approval of the version to be published. The authors agree to be accountable for all aspects of the work.

Disclosure

SH has a patent through the University of Newcastle related to the use of targeted liposomes. BV reports no conflicts of interest in this work.