Improved Antitumor Efficacy and Pharmacokinetics of Bufalin via PEGylated Liposomes

Yuan et al. Nanoscale Research Letters Improved Antitumor Efficacy and Pharmacokinetics of Bufalin via PEGylated Liposomes Jiani Yuan 0 1 3 Xuanxuan Zhou 0 1 3 Wei Cao 1 3 Linlin Bi 1 3 Yifang Zhang 2 Qian Yang 1 3 Siwang Wang 1 3 0 Equal contributors 1 Department of Natural Medicine & Institute of Materia Medica, School of Pharmacy, The Fourth Military Medical University , Xi'an , China 2 Shaanxi Pharmaceutical Development Center , Xi'an , China 3 Department of Natural Medicine & Institute of Materia Medica, School of Pharmacy, The Fourth Military Medical University , Xi'an , China Bufalin was reported to show strong pharmacological effects including cardiotonic, antiviral, immune-regulation, and especially antitumor effects. The objective of this study was to determine the characterization, antitumor efficacy, and pharmacokinetics of bufalin-loaded PEGylated liposomes compared with bufalin entity, which were prepared by FDA-approved pharmaceutical excipients. Bufalin-loaded PEGylated liposomes and bufalin-loaded liposomes were prepared reproducibly with homogeneous particle size by the combination of thin film evaporation method and high-pressure homogenization method. Their mean particle sizes were 127.6 and 155.0 nm, mean zeta potentials were 2.24 and − 18.5 mV, and entrapment efficiencies were 76.31 and 78.40%, respectively. In vitro release profile revealed that the release of bufalin in bufalin-loaded PEGylated liposomes was slower than that in bufalin-loaded liposomes. The cytotoxicity of blank liposomes has been found within acceptable range, whereas bufalin-loaded PEGylated liposomes showed enhanced cytotoxicity to U251 cells compared with bufalin entity. In vivo pharmacokinetics indicated that bufalin-loaded PEGylated liposomes could extend or eliminate the half-life time of bufalin in plasma in rats. The results suggested that bufalin-loaded PEGylated liposomes improved the solubility and increased the drug concentration in plasma. Bufalin; PEGylated liposome; High-pressure homogenization; Pharmacokinetics Background Cancer diseases are of enormous global significance as the population of cancer patients which annually increase may grow by half by 2020 [ 1 ]. Due to the existence of the blood brain barrier (BBB) and multidrug resistance, glioma tumor is one of the most lifethreatening diseases without effective therapeutic agents clinically [ 2 ]. Bufalin has been isolated and identified from Venenum Bufonis, which are the secretions of the skin and parotid venom glands of the toad Bufo bufo gargarizans Cantor or Bufo melanostictus Schneider [ 3 ]. It has been reported to have strong pharmacological effects including cardiotonic, antiviral, immune-regulation, and especially antitumor effects [ 4–7 ]. However, the poor solubility makes it difficult to disperse in the aqueous solution and restricts application [8]. Liposomes have been regarded as a new drug delivery system to improve poor drug solubility in hydrous solution, enhance the bioavailability, increase the therapeutic efficiency, and reduce the side effects [ 9 ]. Chiefly, it can be helpful for agents loaded to pass through BBB and delivery to the brain [ 10 ]. However, one of the major shortcomings of liposomal formulation is its rapid clearance from the blood due to the absorption of plasma protein to the phospholipid membrane of liposomes, which afterwards triggers the recognition and uptake on the liposomes by the mononuclear phagocytic system. Fortunately, when polyethylene glycol (PEG) is modified on the surface of liposomes, this kind of phagocytose can be sluggish. Hence, it is necessary to study bufalinloaded PEGylated liposomes as long-circulating liposomes to increase its aqueous solubility and improve its pharmacokinetics [ 11 ]. Up to date, studies on the pharmacokinetics of bufalin have not yet been paid much attention. Some reports only focus on the pharmacokinetics of free bufalin in aqueous solution per os administration. In the present study, we developed PEGylated liposomes as a delivery system of bufalin and compared the pharmacokinetic difference among bufalin-loaded PEGylated liposomes, bufalin-loaded liposomes, and bufalin entity in aqueous solution by intravenous administration in rats. Methods Chemicals and Reagents Bufalin (≥ 98% in purity) was purchased from BaoJi Chenguang Technology Development Co., Ltd. (Baoji, Shaanxi, China). L-α-phosphatidylcholine, cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamineN-[methoxy(polyethylene glycol)-2000] (ammonium salt; DSPE-PEG2000) were purchased from Sigma Chemical Co., Ltd.(St. Louis, MO, USA) (the molecular formulas of these substances were shown in Additional file 1: Figure S1). The acetonitrile used was of spectroscopic grade and purchased from Honeywell (America). Chloroform and alcohol (analytical grade) were purchased from Tianjin Kemiou Chemical Reagent Co., Ltd. (China). All chemicals were analytical or high-performance liqu (...truncated)