Yumei Wu,1– 3,* Chunhua Zeng,1– 3,* Jiajia Lv,1– 3 Hongyu Li,1– 3 Jie Gao,1– 3 Zhidong Liu,4 Zeli Yuan1– 3 

1Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi, 563000, People’s Republic of China; 2Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi, 563000, People’s Republic of China; 3Guizhou International Scientific and Technological Cooperation Base for Medical Photo-Theranostics Technology and Innovative Drug Development, Zunyi Medical University, Zunyi, 563000, People’s Republic of China; 4Engineering Research Center of Modern Chinese Medicine Discovery and Preparation Technique, Ministry of Education, Tianjin University of Traditional Chinese Medicine, Tianjin, 301617, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Zhidong Liu, Tianjin University of Traditional Chinese Medicine, No. 10 Poyanghu Road, Tianjin, Jinghai District, 301617, People’s Republic of China, Email lonerliuzd@163.com Zeli Yuan, Zunyi Medical University, Zunyi, 563000, People’s Republic of China, Email zlyuan@zmu.edu.cn

Background: Combination therapy offers superior therapeutic results compared to monotherapy. However, the outcomes of combination therapy often fall short of expectations, mainly because of increased toxicity from drug interactions and challenges in achieving the desired spatial and temporal distribution of drug delivery. Optimizing synergistic drug combination ratios to ensure uniform targeting and distribution across space and time, particularly in vivo, is a significant challenge. In this study, cRGD-coated liposomes encapsulating optimized synergistic cepharanthine (CEP; a chemotherapy drug) and IR783 (a phototherapy agent) were developed for combined chemotherapy and photothermal therapy in vitro and in vivo.
Methods: An MTT assay was used to evaluate the combination index of CEP and IR783 in five cell lines. The cRGD-encapsulated liposomes were prepared via thin-film hydration, and unencapsulated liposomes served as controls for the loading of CEP and IR783. Fluorescence and photothermal imaging were used to assess the efficacy of CEP and IR783 encapsulated in liposomes at an optimal synergistic ratio, both in vitro and in vivo.
Results: The combination indices of CEP and IR783 were determined in five cell lines. As a proof-of-concept, the optimal synergistic ratio (1:2) of CEP to IR783 in 4T1 cells was evaluated in vitro and in vivo. The average diameter of the liposomes was approximately 100 nm. The liposomes effectively retained the encapsulated CEP and IR783 in vitro at the optimal synergistic molar ratio for over 7 d. In vivo fluorescence imaging revealed that the fluorescence signal from cRGD-CEP-IR783-Lip was detectable at the tumor site at 4 h post-injection and peaked at 8 h. In vivo photothermal imaging of tumor-bearing mice indicated an increase in tumor temperature by 32°C within 200 s. Concurrently, cRGD-CEP-IR783-Lip demonstrated a significant therapeutic effect and robust biosafety in the in vivo antitumor experiments.
Conclusion: The combination indices of CEP and IR783 were successfully determined in vitro in five cell lines. The cRGD-coated liposomes encapsulated CEP and IR783 at an optimal synergistic ratio, exhibiting enhanced antitumor effects and targeting upon application in vitro and in vivo. This study presents a novel concept and establishes a research framework for synergistic chemotherapy and phototherapy treatment.

Keywords: drug delivery, liposomes, synergistic effects, phototherapy