Elsevier

Biomaterials

Volume 33, Issue 5, February 2012, Pages 1596-1606
Biomaterials

Cholesterol-based anionic long-circulating cisplatin liposomes with reduced renal toxicity

https://doi.org/10.1016/j.biomaterials.2011.10.081Get rights and content

Abstract

Cholesterol anchored derivatives of 5-Cholestene-3-beta-ol 3-hemisuccinate (CHO-HS) and 1-cholesteryl-4-ω-methoxy-polyethylene glycol succinate (CHO-PEG) have been synthesized via esterification and employed at various ratios with di-stearoylphosphatidylcholine (DSPC) in the preparation of anionic long-circulating nanoliposmes for cisplatin (CDDP) delivery. In the present study, CHO-HS and CHO-PEG were characterized by FTIR and 1H NMR. The particle size and zeta potential of liposomes were determined by Dynamic lights scattering (DLS). The obtained liposomes have concentratedly distributed nanosizes around 100 nm and proper zeta potentials between −39.7 mV and −3.18 mV and good physical stability in test period of 28 days. Fine morphology of the liposomal vesicles can be observed via transmission electron microscopy (TEM). The CDDP encapsulating percentage of liposomes was 43–94% and loading efficiency was 7.5–29.3%, depending on the presence or absence of CHO-HS and CHO-PEG. In addition, the in vitro drug release behaviors, in vitro cytotoxicity against HeLa cells and 293T cells and in vivo CDDP distribution of CDDP loaded CHO-HS/CHO-PEG liposomes were evaluated. The results suggest that CHO-HS/CHO-PEG nanoliposomes represent a promising strategy for the CDDP delivery as an effective long-circulating drug carrier system which may reduce the acute renal toxicity.

Introduction

Platinum compounds play an important role in cancer chemotherapy. Cisplatin, (cis-diammine dichloroplatinum (II); CDDP), the first generation of platinum based chemotherapy drug, is one of the most common anticancer agents and has a broad spectrum of anticancer activity in the treatment of solid tumors including gastrointestinal, head and neck, genitourinary and lung tumors [1], [2], [3], [4], [5]. However, broader therapeutic applications of CDDP are limited by drawbacks such as the low selectivity between malignant and normal cells, the presence of intrinsic or acquired resistance, short time period of retention, rapid inactivation and severe toxic effects (e.g. anemia, deafness, vomiting, nausea and neurotoxicity, particularly nephrotoxicity [6], [7], [8], [9]).

According to the previous research, about 25–35% of patients display a significant decline of renal function following a single dose (50–100 mg/m2) of CDDP [10], [11] due to its preferential accumulation in the kidney, nephrotoxicity consequently becomes the main limit of CDDP in clinical use and to the greater efficacy [12], [13], [14]. Many of the current studies are focus on the underlying cause of cisplatin-induced nephrotoxicity [15], [16], [17], however, the mechanisms are not fully understood. To overcome this shortcoming, enhancement of the hydrophobicity and polymerization of platinum drugs become the mainstream theories of anti-nephrotoxicity strategy. Plenty of related platinum compounds such as carboplatin, oxaliplatin and nedaplatin have been synthesized and tested in the last two decades with the aim of improving the drug efficacy [15]. Also, the anionic carriers such as anionic dendrimers [18], poly (amino acid) [19], anionic polysaccharide [20], anionic polyester [21], alginate and other anionic polymers, were usually designed as the CDDP delivery system in order to load more CDDP in vectors and increase the loading efficiency. Further more, the complex formation of CDDP with the anionic groups could polymerize the platinum drug and the macromolecular drug compounds tend to improve the uptake and effect on retention of CDDP to a higher level in tumors than in the normal tissues indeed in the absence of a targeting group [22]. Such selective targeting which won’t appear in the using of low-molecular weight drugs has been termed “the enhanced permeability and retention effect” (EPR effect) [23].

Specific drug delivery systems (DDS) such as liposomes, micelles, microspheres and other lipid or polymer-based particles have been investigated [24], [25] and designed to polymerize the small molecules so as to endue the polymeric drugs with EPR effect that could reduce drug toxicity and side effects, as well as to prolong the circulation time of encapsulated drugs and improve the in vivo anticancer therapy [26]. It was proved by the advanced clinical studies in patients that liposome is a multifunctional and successful DDS [24] due to the low in vivo toxicity, easily controlled size, high carrying capacity of lipophilic, hydrophilic and amphipathic drugs, membrane-like property, and biocompatibility [27], [28], [29].

In recent years, polyethylene glycol (PEG) modifications were often incorporated into the liposomal system to receive long-circulating stealth liposomes which are able to escape from being phagocytized by the reticuloendothelial system (RES) [30] and can exhibit a prolonged circulation time. Several PEG grafted phospholipids, such as distearoylphosphatidylethanolamine-PEG (DSPE-PEG) [31], phosethanolamine-PEG (PE-PEG) [32] and distearoylglycerol-PEG (DSG-PEG) [33], were designed and successfully maintained the circulation time of drugs. However, the employments of phospholipids-anchored modification induced high cost and inconvenience in the synthesis due to the difficulties in separation of phospholipids and PEG-phospholipids. Another essential constituent of liposomes–cholesterol, which works as the framework in liposomal membrane, could reduce the fluidity of membrane and plays an important role in stabilization and controlling the drug permeability properties of liposomal membrane bilayer [34], [35], [36]. Thus cholesterol was developed as another anchor of modification to obtain materials with the framework-like function as cholesterol and even more specialities. In addition, it was proved that cholesterol anchored PEG-modified liposomes were easily incorporated into the liposomal membranes compared with that of phospholipids-anchored PEG-modified liposomes in the previous report [37].

According to the informations above, the purpose of our work was to design an anionic hydrophobic vector to polymerize the CDDP so as to reduce the nephrotoxicity and increase the loading efficiency. It’s the first time that a simple and efficient long-circulating anionic liposomal nanosystem containing cholesterol-based derivatives was prepared and used in the CDDP delivery. 5-Cholesten-3-beta-ol 3-hemisuccinate (CHO-HS, used as the anionic moiety) and 1-cholesteryl-4-ω-methoxy-polyethylene succinate (CHO-PEG, used as the long-circulating moiety) were selected to be synthesized and incorporated into the liposome system in the interest of EPR effect and reducing the renal toxicity.

Section snippets

Chemicals and materials

Cholesterol (CHO), succinic anhydride (SA), cisplatin (CDDP), 4-dimethylamino pyridine (DMAP), monomethoxy-polyethylene glycol (MPEG) with molecular weight of 550 or 2000, tetrahydrofuran (THF), dimethyl formamide (DMF), ethanol, methanol, acetone and di-stearoylphosphatidylcholine (DSPC) were obtained from Shanghai Chemical Reagent Co., China. All other chemicals were of analytical grade and used as received.

Synthesis of CHO-HS

The CHO-HS was prepared by reaction of the cholesterol with succinic anhydride in

FTIR spectra

Fig. 2 shows the FTIR spectra of cholesterol (spectrum A), CHO-HS (spectrum B) and CHO-PEG (spectrum C). In Fig. 2A, the absorption peaks at 3420 cm−1, 2930 cm−1, 1460 cm−1, 1380 cm−1 are associated with hydroxyl bonds, alkene bonds, methylene and methyl groups of cholesterol, respectively. In Fig. 2B, the broad peak appearing between 3400 and 2500 cm−1 and the peak at 1720 cm−1 are indicative of absorption by O–H bonds and carbonyl bonds in carboxylic acid; absorption peaks appearing at 1660 cm

Conclusion

In this study, mono-cholesteryl succinate (CHO-HS) and 1-cholesteryl-4-ω-methoxy-polyethylene succinate (CHO-PEG) were successfully synthesized and characterized by 1H NMR and FTIR. The synthesized materials have been developed to produce stable and long-circulation liposomes. Physicochemical characteristics of the liposomes were investigated by assessing profiles of the vesicle size, zeta potential, drug encapsulation percentage and loading efficiency, the transmission electron microscopy and

Acknowledgements

The authors are grateful for the financial support of the National Basic Research Program of China (2009CB930300 and 2011CB606202).

References (42)

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