An organic solvent-free technology for the fabrication of albumin-based paclitaxel nanoparticles for effective cancer therapy
Graphical abstract
Introduction
Cancer is reported as one of the major death causes that seriously affect human health and threaten human life all around the world [1]. The three major treatments for cancer, including surgery, radiotherapy and chemotherapy, are commonly utilized to extend the survival time of the patients and improve their life quality. Chemotherapy, a systemic treatment, is typically preferred at advanced stages of cancer for its superior effectiveness [2,3]. Various chemotherapeutic agents have been discovered over the past century for anticancer therapy through specific targeted pathways [4].
Paclitaxel (PTX), a natural diterpenoid ester isolated from Pacific Taxus and other Taxus plants, is one of the most popular chemotherapeutic drugs after doxorubicin. PTX exerts its prompt clinical curative effects via accelerating tubulin aggregation and microtubule stabilization, which finally leads to programmed cell death at the G2-M phase [[5], [6], [7], [8], [9]]. However, on account of the extremely poor solubility of PTX in water (less than 1 μg/mL), the therapeutic potential of PTX in the natural form has been inhibited [[10], [11], [12], [13]]. To overcome the drawbacks, PTX injection (Taxol®), utilized Cremophor EL and absolute ethanol (1:1, v/v) as co-solvent, has been developed for the usage of parenteral administration in 1992 [14]. Although the application of Cremophor EL promotes the dissolution and absorption of PTX, it also brings various adverse effects, including hypersensitivity reactions, nephrotoxicity, and neurotoxicity [12,15]. In order to avoid the adverse eff ; ;ects of Cremophor EL and enhance the therapeutic efficacy of PTX, Abraxane®, the classical Cremophor EL-free human serum albumin-bound PTX (nab-PTX), was approved by the US Food and Drug Administration (FDA) for cancer treatment in 2006 [16] and has gained heightened attention for researches in human serum albumin (HSA)-based nanomedicine from then on owing to the desired properties of HSA, such as chemical stability, biodegradability, and biocompatibility [17,18].
Bovine serum albumin (BSA), a major soluble protein with a structure similar to human serum albumin, has been typically utilized as alternative nanocarrier to HSA in virtue of its low cost [19,20]. Several bovine serum albumin-based PTX nanoparticles [11,[21], [22], [23]] have been reported to accumulate in tumor tissue due to the enhanced permeability and retention (EPR) effect arisen from the peculiar tumor characteristics of leaky vasculature and defective lymphatic drainage systems [24]. However, most of the preparation processes for the above albumin-based nanoparticles, including Abraxane®, involve organic solvents [20,25], which have been reported to exert certain influence on the structure and the drug load efficiency of albumin [26], and eventually bring apparent in vivo toxicity due to residual solvent [27]. Besides, the poor colloidal stability of albumin-based nanoparticles will also lead to their rapid elimination in the blood circulation [10,28].
Long-circulating liposomes with modifying hydrophilic polymers, such as distearoylphosphatidylethanolamine-polyethylene glycol (DSPE-PEG), have been utilized as versatile drug delivery systems for the last few decades contributed to their prolonged blood circulation time [29]. Nevertheless, the challenging problems of fusion, aggregation and leakage for liposomes still remain unsolved in clinic [30]. In the current study, in order to avoid direct contact of albumin with organic solvents and enhance the colloidal stability of the formulation, a novel PTX liposome-albumin composite nanoparticles (Lip-PTX/BSA NPs) (Fig.1) were prepared without further chemical modification for the sake of developing a simple fabrication method. Two critical factors including particle size and drug-loading content loss of the nanoparticles were selected for DOE study through Box-Benhnken design-response surface (BBD) to optimize the preparation process. The binding of liposome to albumin during the self-assembly process were verified through spectroscopic studies. Furthermore, characterization of the nanoparticles, including size, morphology, and cumulative release behavior in vitro, were evaluated as well. Eventually, in vitro cytotoxicity and in vivo antitumor efficacy of the nanoparticles were carried out.
Section snippets
Materials
Paclitaxel (PTX) was obtained from Dalian Meilun Biotechnology Co., Ltd (Dalian, China). Bovine serum albumin (BSA) was provided by J&K China Chemical Ltd (Beijing, China). DSPE-PEG2000, cholesterol and phosphatidylcholine (EPC) were obtained from Lipoid GMBH (Germany). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was obtained from Sigma Aldrich Chemicals (Germany). RPMI-1640 was obtained from Hyclone Thermo Scientific (America). Fetal bovine serum (FBS) was provided by
Experimental design and analysis
Three variables including X1 (ratio of drug-EPC), X2 (ratio of drug-BSA) and X3 (pH of media), together with two dependent variables including Y1 (size), and Y2 (DLC loss rate) were selected upon exhaustively exploring the comprehensive evaluation of the feasibility for the response composition. The Box-Behnken experimental design provided 17 runs of experiments. Table S2 exhibited the manufacturing conditions and the measured responses. To select a suitable model during optimization, several
Conclusion
The present studies successfully fabricated novel organic solvent-free formulation of albumin-based paclitaxel-loaded nanoparticles (Lip-PTX/BSA NPs). The nanoparticles with a mean diameter of approximately 116 nm (in the range of 50–150 nm) were capable of passively targeting to tumor tissue through EPR effect. Besides, Lip-PTX/BSA NPs exhibited in vitro sustained drug release profiles for 96 h and excellent colloidal stability due to the necessary steric repulsion of the hydrophilic PEG tails
Declaration of Competing Interest
The authors declare no competing financial interests.
Acknowledgments
This work was financially supported by the National Natural Science Foundation of China (no. 21473085), the National Science and Technology Major Project (no. 2017ZX09201-003), Key Research and Development Program of Shandong Province of China (no. 2015GSF118160), the Natural Science Foundation of Shandong Province of China (no. ZR2016CL14, no. ZR2017BH065), the Project of Shandong Province Higher Educational Science and Technology Program (no. J17KA234), the Open Project of Shandong
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