Single Protein Encapsulated Doxorubicin as an Efficacious Anticancer Therapeutic.

Small-molecule chemotherapeutics are potent and effective against a variety of malignancies, but common and severe side effects restrict their clinical applications. Nanomedicine approaches represent a major focus for improving chemotherapy, but have met limited success. To overcome the limitations of chemotherapy drugs, we have developed a novel Single Protein Encapsulation (SPE)-based drug formulation and delivery platform and tested its utility in improving doxorubicin (DOX) treatment. Using this methodology, a series of SPEDOX complexes were generated by encapsulating various numbers of DOX molecules into a single human serum albumin (HSA) molecule. UV/fluorescence spectroscopy, membrane dialysis, and dynamic light scattering techniques showed that SPEDOXs are stable and uniform as monomeric HSA and display unique properties distinct from those of DOX and DOX-HSA mixture. Furthermore, detailed procedures to precisely monitor and control both DOX payload and binding strength to HSA were established. Breast cancer xenograft tumor studies revealed that SPEDOX-6 treatment displays improved pharmacokinetic profiles, higher antitumor efficacy, and lower DOX accumulation in the heart tissue compared with unformulated DOX. This SPE technology, which does not involve nanoparticle assembly and modifications to either small-molecule drugs or HSA, may open up a new avenue for developing new drug delivery systems to improve anticancer therapeutics.