Article pubs.acs.org/molecularpharmaceutics
PEGylated Nanoparticles Obtained through Emulsion Polymerization as Paclitaxel Carriers Claudio Colombo,† Lavinia Morosi,‡ Ezia Bello,‡ Raffaele Ferrari,‡ Simonetta Andrea Licandro,‡ Monica Lupi,‡ Paolo Ubezio,‡ Massimo Morbidelli,§ Massimo Zucchetti,‡ Maurizio D’Incalci,‡ Davide Moscatelli,*,† and Roberta Frapolli‡ †
Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Via Mancinelli 7, 20131 Milano, Italy Department of Oncology, IRCCS, Istituto di Ricerche Farmacologiche Mario Negri, Via La Masa 19, 20156 Milano, Italy § Institute for Chemical and Bioengineering, ETH Zurich, Vladimir Prelog Weg, CH-8093 Zurich, Switzerland ‡
S Supporting Information *
ABSTRACT: Polymer nanoparticles (NPs) represent a promising way to deliver poorly water-soluble anticancer drugs without the use of unwanted excipients, whose presence can be the cause of severe side effects. In this work, a Cremophor-free formulation for paclitaxel (PTX) has been developed by employing PEGylated polymer nanoparticles (NPs) as drug delivery carriers based on modified poly(ε-caprolactone) macromonomers and synthesized through free radical emulsion polymerization. Paclitaxel was loaded in the NPs in a postsynthesis process which allowed to obtain a drug concentration suitable for in vivo use. In vivo experiments on drug biodistribution and therapeutic efficacy show comparable behavior between the NPs and the Cremophor formulation, also showing good tolerability of the new formulation proposed. KEYWORDS: Paclitaxel, Cremophor, Breast Cancer, Nanoparticles, Drug Delivery, Emulsion Polymerization
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INTRODUCTION The use of nanocarriers to efficiently deliver a therapeutic agent to a specific tissue, enhancing its efficacy and at the same time lowering the side effects related to its use, has the potential to significantly change the biomedical field (nanomedicine). Over the last decades, different classes of carriers belonging to the nanoscale have been developed, among which liposomes, micelles and polymer nanoparticles (NPs). In particular, the latter carriers have been widely studied due to the possibility of conveying a wide range of pharmaceuticals as well as to have controlled release of the active compound, specifically in the target organ or tissue.1 Polymer NPs for biological applications are typically based on biodegradable polyesters such as poly(lactic acid) (PLA), poly(caprolactone) (PCL), and poly(lactic-co-glycolic acid) (PLGA), whose biocompatibility is widely assessed.2−4 A critical step in the NP evolution has been the surface functionalization with hydrophilic moieties that enabled NPs to reduce their nonspecific binding with blood proteins and subsequent uptake by the macrophages (opsonization), thus allowing them to have longer circulation time in the bloodstream. This feature is commonly obtained by conjugating the NPs with poly(ethylene glycol) (PEG) chains, which form an hydrophilic barrier to protein−NP interactions.5−7 A general advantage in the use of NPs is their ability to formulate hydrophobic drugs, whose poor water solubility may hinder direct intravenous injection. This is for example the case of paclitaxel (PTX), a drug extracted from Taxus brevifolia © XXXX American Chemical Society
mainly used for the treatment of breast and ovarian cancer, but whose very low water solubility requires the use of excipients for intravenous injection.8,9 The standard formulation for PTX consists in 30 mg of drug in a mixture composed of dehydrated ethanol and Cremophor (50% v/v), a nonionic surfactant obtained through the reaction of ethylene oxide with castor oil.10 However, Cremophor is not a biologically inert substance, and its use has been related to acute hypersensitivity reaction, cytotoxicity, and neurotoxicity.11 For this reason, and given the biocompatibility of polyester-based NPs, several formulation based on these carriers for the delivery of PTX have been studied.12−14 Despite the fact that a very large number of NPbased formulations have been proposed for the delivery of anticancer drugs, only a very few are in clinical trials and even less have reached the market.15 This can be attributed to several causes, among which the inherent difficulty in clinical translation for nanocarriers.16 Also, there is a certain tendency in the literature to focus the attention only on the tumor and not on the overall distribution of the drug and the side effects related to the use of these new carriers. On the contrary, formulations that have undergone clinical trials show relatively higher concentration of drug in the tumor in respect to the standard formulations of their active principle without the use Received: May 18, 2015 Revised: November 23, 2015 Accepted: December 1, 2015
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DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
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Molecular Pharmaceutics of undesired excipients.17 Finally, it is important to point out that for PTX, the only nanoparticulate formulations present on the market are constituted by the drug stabilized in water with albumin (Abraxane) or with polymeric surfactants made of poly(lactic acid)-co-poly(ethylene glycol) (Genexol). In this work, a new class of surfactant-free PEGylated polymer NPs based on modified biodegradable polyester chains are adopted as PTX carriers. NPs have been synthesized through emulsion free radical polymerization, a process commonly used in the polymer industry. The synthesis was done via a two-step procedure: in the first one functionalized caprolactone macromonomers were obtained through a ring opening polymerization (ROP) of ε-caprolactone (CL) using tin octoate (Sn(Oct)2) as a catalyst and 2-hydroxyethyl methacrylate (HEMA) as a cocatalyst.18 At the end of this step, which was carried out in bulk conditions, short oligomer, composed of 3 CL units and functionalized with the preserved vinyl unit coming from the HEMA molecule are obtained (hereinafter named HEMA-CL3). In the second step, the presence of the vinyl bond allows the use of these macromonomers in a subsequent free radical emulsion polymerization. To obtain PEGylated NPs, the produced macromonomers have been copolymerized together with a commercially available PEGylated methacrylate (HEMA-PEG) in a monomer-starved semibatch emulsion polymerization (MSSEP). The final product of this procedure are NPs composed by a comb-like polymer with a poly(HEMA) backbone with PCL and PEG side chains. Latter chains act as a stabilizing agent and also contribute to avoid opsonization. By using this synthetic route, it is possible to obtain monodispersed NP latexes with a solid concentration that is higher than the ones obtained through nanoprecipitation.19,20 Moreover no solvent or surfactant are required, thus ensuring high biocompatibility and decreasing toxicity issues. Because NPs are produced through a process that requires relatively high temperature and the presence of active radicals the drug loading step must happen after the NP synthesis. Therefore, a methodology to effectively load PTX on the NPs was used, based on the mixing of the NP latex with the drug dissolved in ethanol in a mixing device in which the drug is adsorbed on solvent-swollen NPs. We already applied this process to other pharmaceuticals, such as tetracyclines.21 The advantages in using these polymeric NPs compared to the two formulations for PTX based on NPs already on the market are, on one side, the possibility to produce PTX-loaded carriers using emulsion polymerization, an already well-established and widely adopted process on industrial scale. On the other hand, the use of polymeric NPs will allow a further development of the carrier that, for example, can be easy functionalized with a targeting agent in order to increase the therapeutic index other than by the passive enhanced and permeation retention (EPR) effect. Furthermore, no steps such as chromatographic purification or ultrafiltration, which are difficult to translate beyond the laboratory scale,22 are required. Also, at the end of the loading process, the PTX concentration is high enough to be suitable for intravenous injection without the need of further concentration steps. Finally, the use of an emulsion polymerization process allows the synthesis of well-defined and reproducible NPs in terms of size, size-polydispersity, and surface charge, coupled with low cost for the production of the carrier. Drug-loaded NPs were then tested in vivo on mice bearing MDA xenograft breast cancer model; in particular, the
antitumor activity was assessed following repeated treatment, whereas drug biodistribution and excretion was evaluated after a single treatment; the performance of the NPs was compared with the standard formulation of PTX. The toxicity of the produced formulation was also investigated monitoring the evolution of the body weight of the animal.
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EXPERIMENTAL SECTION Materials. For macromonomer production and NP synthesis, ε-caprolactone (CL, 99%), 2-hydroxyethyl methacrylate (HEMA, ≥ 99%), 2-ethylhexanoic acid tin(II) salt (Sn(Oct)2, ∼ 95%), potassium persulfate (KPS, ≥ 99%), poly(ethylene glycol) methyl ether methacrylate (HEMA-PEG19, molecular weight: ca. 950 Da) and albumin from fetal bovine serum (BSA 96%) were purchased from Sigma-Aldrich and used without further treatment. Paclitaxel was supplied by Indena (Italy). Synthesis of the Macromonomer. HEMA-CL3 macromonomer was prepared through a bulk ROP process as described in literature.18 Briefly, 30 mg of tin octoate (Sn(Oct2)) was mixed with a proper amount of HEMA (3.8 g) and left under magnetic stirring at room temperature until full dissolution. ε-Caprolactone (CL, 10 g) was heated up to 130 °C in a stirred flask with temperature controlled by an external oil bath. The HEMA/Sn(Oct)2 solution was then added to the flask; the reaction was carried out for 2 h. 1H NMR spectroscopy was used to characterize the produced material in terms of average chain length; the analysis was carried out by dissolving the sample in CDCl3 and results are reported in the Supporting Information. Synthesis of NPs. NPs were produced through a MSSEP as described in a previous paper.7 This synthesis was carried out in a 50 mL three necked glass flask. A total of 0.5 g of HEMAPEG19 were added to 45 mL of distilled water and the solution was heated up to 80 °C; inert atmosphere was obtained through repeated nitrogen−vacuum cycles. Then, 0.02 g of KPS, dissolved in 2.5 mL of distilled water, was added to the purged solution. After that, 2 g of HEMA-CL3 were injected with a rate of 2 mL/h using a syringe pump (Model NE-300, New Era Pump System, U.S.A.). The reaction was run for 3 h to yield PEGylated NPs (hereinafter named blank PCL3 NPs). The solid content of all the final latexes is equal to 2.5 g (5 wt %/wt). Data about size and particle size distribution (PSD) of the NP dispersions have been determined through dynamic light scattering measurements (DLS, Malvern, Zetanano ZS). Drug Loading. NP synthesis was carried out at high temperature and in the presence of radicals; therefore, the drug loading procedure had to be done after NP production to avoid thermal degradation of the drug; for this reason, a postsynthesis process had to be used.21 First, the concentration of the produced latex was increased up to 6 wt % under rotatory vacuum; the absence of aggregation during this step was confirmed by DLS analysis. PTX was dissolved in ethanol (30 mg/mL) under vortex stirring. The drug loading was carried out by contacting the two phases (blank PCL3 NPs and drug dissolved in ethanol) in a mixing device composed of a PTFE cylinder of 1 cm of diameter and length with an axial perforation of 1 mm and a radial perforation of 500 μm. The two phases were loaded in syringe pumps (Model NE-300, New Era Pump System, U.S.A.) and were injected axially in the device at a flow rate of 30 mL/min for the NPs and 5 mL/min for the drug. PTX-loaded NPs (hereinafter referred to PCL3 NPs) are collected from the radial perforation; the absence of PTX aggregates related to this process was confirmed by DLS B
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veterinarian who is responsible for health monitoring, animal welfare supervision, experimental protocols, and procedures revision. Antitumor Activity and Pharmacokinetics. Exponentially growing MDA-MB-231 human breast cancer cells were suspended in PBS and mixed in a 1:1 ratio with Matrigel. A 0.2 mL suspension containing 10 × 106 cells was injected subcutaneously on the right flank of 7 weeks old female athymic nude mice (Harlan Lab). Tumor growth was monitored two times a week by vernier caliper and tumor volume calculated as follows: (length × (width)2)/2. When tumor weight achieves about 250 mg (under the assumption that 1 mm3 = 1 g), mice were randomized into the experimental groups. PTX (free drug) was dissolved in Cremophor EL/ ethanol 1:1 and diluted in saline immediately before use to a final concentration of 2.5 mg/mL. Mice were treated iv at 25 mg/kg with the free drug and PCL3 NPs. The treatment was repeated every week for three times (q7dx3) for the antitumor activity evaluation. Tolerability was evaluated on the basis of body weight loss (BWL), clinical observation, and mortality. For the pharmacokinetics study blood was collected 1, 4, 24, and 48 h after treatment from the retroorbital plexus under isoflurane anesthesia. Mice were sacrificed by cervical dislocation and tumor and liver removed and immediately frozen in dry ice. To obtain plasma, blood samples were centrifuged at 4000 rpm for 10 min at 4 °C. All the collected samples were stored at −20 °C until analysis. Urine and feces were collected from three mice for each treatment group, 24 and 48 h after treatment, by using metabolic cages. The total concentration of PTX in the different biological matrixes was determined by HPLC as previously described.24,25 For the determination of PTX in tumor and liver, tissues were previously homogenized in 0.2 M CH3COONH4 pH 4.5. Each study sample (0.3 mL for plasma and 0.5 mL for homogenate tissues) was assayed together with a five-point standard calibration curve prepared in the corresponding control matrix of plasma tumor and liver obtained from untreated mice at concentrations ranging from 0.05 to 5 μg/ sample. The limit of quantification (LOQ) was 0.16 μg/mL 0.6 μg/g, and 0.8 μg/g, respectively. Statistical Analysis. Statistical analysis was performed with GraphPad Prism version 6.01 software (GraphPad software, Inc., La Jolla, CA, U.S.A.). Student t test was performed to evaluate differences in drug release experiments. A two way ANOVA test followed by Bonferroni post hoc test were performed to evaluate if there are any statistically significant differences between treated and control groups in the antitumor activity study.
measures. Before any further use, PCL3 NPs were dialyzed against PBS to remove ethanol with Slide-A-Lyzer Dialysis Cassettes (MW cutoff 7000 Da; Thermo Scientific). Quantification of the Drug Loading and In Vitro Release. Drug loading efficiency (LE) was determined via HPLC through the evaluation of the difference between the amount of drug recovered in the whole NP solution and the one recovered from the supernatant obtained after NPs precipitation. LE can be expressed by the following equation: ⎛ drug recovered in the supernatant [mg] ⎞ LE = ⎜1 − ⎟× 100 drug recovered in the latex [mg] ⎠ ⎝
To obtain the complete precipitation of the NPs, centrifugal filters (Amicon Ultra, 100 kDa cutoff) were used at 4500 rpm for 15 min; the absence of residual NPs from the supernatant was evaluated via DLS.23 For in vitro release studies, PCL3 NPs were diluted with PBS containing 40 mg/mL of BSA down to a concentration of 15 μg/mL; 3 mL was put in dialysis cassettes and sank in 300 mL of a solution of BSA in PBS (40 mg/mL) at 37 C and small samples (≈100 μL) were withdrawn at selected times and the drug content was measured. The amount of drug was determined by HPLC analysis coupled to UV detection. The methods employed were illustrated in our previous publications.24,25 Briefly, 0.1 mL of NPs solution were spiked with 5 μg of an internal standard (IS) and extracted with 0.5 mL of CH3CN. After vortex mixing for 10 s, samples were centrifuged at 13 000 rpm for 10 min. The organic phase was separated and dried under nitrogen, and the residues were dissolved with 250 μL of mobile phase composed by 50% of ammonium acetate buffer (0.01 M pH 5), 40% acetonitrile, and 10% methanol. The apparatus was equipped with a Waters Symmetry C18 column (5 μm, 4.6 × 150 mm), with mobile phase pumped at a flux rate of 1.3 mL/min and 30 min run time. Control NPs without drugs were used to prepare the calibration curve at PTX concentration range 1−100 μg/ mL. The analytical reference standard powder of paclitaxel and the IS used, IDN5390 were generously provided by Indena SPA, Settala (MI), Italy. Animal Care. Procedures involving animals and their care were conducted in conformity with the following laws, regulations, and policies governing the care and use of laboratory animals: Italian Governing Law (D.lgs 26/2014; Authorization no. 19/2008-A issued March 6, 2008 by Ministry of Health); Mario Negri Institutional Regulations and Policies providing internal authorization for persons conducting animal experiments (Quality Management System CertificateUNI EN ISO 9001:2008Reg. No. 8576-A); the NIH Guide for the Care and Use of Laboratory Animals (2011 edition), and EU directives and guidelines (EEC Council Directive 2010/63/ UE) and in line with Guidelines for the welfare and use of animals in cancer research. The Statement of Compliance (Assurance) with the Public Health Service (PHS) Policy on Human Care and Use of Laboratory Animals has been recently reviewed (9/9/2014) and will expire on September 30, 2019 (Animal Welfare Assurance #A5023-01). Animal experiments have been reviewed and approved by the IRFMN Animal Care and Use Committee (IACUC) that includes members “ad hoc” for ethical issues. Animals were housed in the Institute’s Animal Care Facilities, which meet international standards; they are regularly checked by a certified
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RESULTS AND DISCUSSION Production of the NPs. The HEMA-CL3 (MW 473 Da) macromonomer was synthesized using a bulk ROP process as described in the Experimental Section. Characterization of the product was carried out through 1H NMR analysis, as reported in the Supporting Information. The MSSEP of the produced macromonomer together with HEMA-PEG19 yields PEGylated polymer NPs (PCL3 NPs) composed of a poly(HEMA) backbone with PEG and PCL chains covalently bound to the NPs themselves. The diameter of blank PCL3 NPs was 108 nm with a PDI of 0.06 and a Z potential of −2.3 mV as determined by DLS measurements. Before being used for PTX loading, the latex concentration was increased under rotatory vacuum at C
DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
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Molecular Pharmaceutics room temperature from the original value to 6% wt. Afterward the loading step was carried out as explained in the Experimental Section through the use of a mixing device. The lipophilicity of the PCL chains aided the loading of the lipophilic and water-insoluble PTX, whereas PEG chains ensured the colloidal stability of the drug-loaded NPs. It is safe to assume that PTX will preferentially be located on the NP outer region because the drug loading step is carried out after NP synthesis through an adsorption−diffusion mechanism. DLS analysis of different steps is reported in Figure 1
Figure 2. In vitro release of PTX from PCL3 NPs (●) and free drug (■), data expressed as mean ± SD.
average percentage of drug released is 67% for PCL3 NPs, whereas almost complete release was achieved for the free drug, confirming that the presence of NPs slows the release of PTX in an albumin-containing medium. Safety and Antitumor Activity. The mouse body weight during the experiment is reported in Figure 3 together with the evolution of the tumor mass. It is of note that no BWLs were observed and the evolution of the body weight is very similar to control for all the treatment groups with an overall increasing trend. These data suggest that the toxicity of the produced formulation is comparable to the free drug and is not very marked. Blank NPs also did not influence the trend in body weight growth, therefore suggesting that the same NPs and materials can be used for the formulation and deliver of other drugs or for other biological applications. For a more in-depth analysis, the evaluation of hepatic enzymes was carried out; the results indicate that there is not an increased hepatic toxicity administering PTX formulated in NPs as compared with free drug (data not shown). Looking at the antitumor activities of the formulations depicted in panel B of Figure 3, PCL3 NPs were superimposable to that of the free paclitaxel. All treatment were very active (p < 0.0001 starting from day 33 compared with the respective control) with a best T/C of 29% and 22% on day 36 for free paclitaxel and PCL3 NPs, respectively. Pharmacokinetics of PTX. PTX biodistribution was evaluated at different times after single administration in tumor, liver, and spleen in comparison with the plasma compartment. Figure 4 shows the concentration time curve of PTX determined after NP administration as well as for the free drug dissolved in the conventional formulation of Cremophor EL/ ethanol 1:1. We can see that after the administration of both the PTXloaded NPs, the tumor distribution of PTX at each time point was superimposable to those obtained after the administration of the free drug. The tumor Cmax of PTX was achieved in the time interval 1−4 h and were 6.64 ± 0.90 μg/g for the free drug and 4.89 ± 0.38 μg/g for PCL3NPs; these concentrations decreased after 48 h to 2.05 ± 0.15 μg/g and 1.69 ± 0.12 μg/g for the same formulations. The concentrations in plasma were 9.56 μg/mL for the free drug and 7.02 μg/mL for PCL3 NPs. These concentrations decreased rapidly to 1.29 μg/mL and to 0.51 μg/mL at 4 h and were undetectable at the subsequent time points. Furthermore,
Figure 1. Particle size distribution of the different stages. Black line, blank PCL3 NPs; red line, PCL3 NPs.
From inspection of Figure 1, it is possible to see that the selected synthetic procedure allows the obtainment of monodispersed NP latex. The drug loading procedure leads to a slight broadening of the PDI but no aggregates that can be related to PTX clusters are detectable, as opposed to some experimental evidence for NP synthesis based on nanoprecipitation;26 this absence, coupled with the low water solubility of PTX, indicates that the drug is effectively loaded into the NPs. These parameters are reported in Table 1 as determined by dynamic light scattering; values are the average of three measurements. Table 1. Size and PDI of the different NPs produced NP type
size [nm]
PDI [−]
PCL3 blank NPs PCL3 NPs
108 ± 2 110 ± 3
0.06 0.08
PTX Loading and In Vitro Release. The results show that the PTX can be loaded in the NPs after their synthesis with good efficiency (95%) due to its hydrophobicity and the presence of the hydrophobic PCL chains The release profile of PTX from PCL3 NPs against BSA solution is compared with that of the free drug. The results are reported in Figure 2. No measures were performed after 24 h because previous studies for similar unloaded NPs have shown that their half-life in plasma was around 30 min, and after 4 h, the NP concentration in the tumor reached a steady state.27 By looking at the profile reported in Figure 2, it is possible to see that the use of polymer NPs results in a slower release profile for PTX: for PCL3 NPs, the accumulated release after 1 h represents the 12% of the initial drug content, whereas this value increases to about the 37% for the free drug. At 24 h, the D
DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
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Figure 3. Evolution of the animal body weight (panel A) and tumor mass (panel B) for Taxol, PCL3 NPs, and blank NPs.
Figure 4. Comparison of the PTX distribution in tumor (panel A), plasma (B), liver (C), and spleen (D) of mice bearing MDA-MB-231 tumor after administration of 25 mg/kg of PTX with the different formulations.
the amount of drug recovered in the filter organs is comparable for all of the formulations. A further confirmation of the pharmacokinetic behavior outlined was found by examining the amount of PTX recovered in the feces and urine reported in Figure 5. It can be seen that no significant difference in the amount of PTX recovered from urine and feces was found, therefore indicating that the encapsulation of the drug in the NPs does not alter the excretion route of the drug, confirming a significant release of the drug in vivo upon injection. From all these data, it is clear that the difference in the release profile for PCL3 NPs and free drug that was found in in vitro conditions did not translate in vivo. The values seem to
suggest that the vast majority of the loaded drug is released into the bloodstream before the 4 h, indicating that there are no significant differences between the three formulations both in terms of blood availability and distribution in the tumor and in the main filter organs. This behavior could be due to the fact that, because of the postsynthesis drug-loading step, the concentration of the drug into the NPs is not uniform and the vast majority is located onto the surface; upon injection in the bloodstream, plasma proteins can act as stabilizing agents for the drug itself, improving its solubility and enhancing the release. The addition of a polymer shell to try to slow the release in vivo, discussed in the Supporting Information, did not lead to a significant improvement either. The differences E
DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
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Figure 5. PTX content recovered in the feces (panel A) and urine (panel B) 24 and 48 h after the first and third injection.
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between in vitro and in vivo profiles are presumably largely imputable to the influence that protein absorption as well as blood dynamic have on in vivo behavior of drug loaded NPs,28 this indicate that in vitro test cannot be considered sufficient for the selection of the optimal NPs for drug delivery. Both the biodistribution of PTX as well as the therapeutic effect on the MDA-MB-231 model shows that the overall performance of the produced formulation is more similar to that of Taxol than either Abraxane or Genexol.29 However, the absence of toxic excipients coupled with the ready scalability of emulsion polymerization to the industrial scale and the possibility to easily functionalize the polymer carrier still make the produce NPs a valid alternative for the intravenous delivery of PTX.
Corresponding Author
*E-mail:
[email protected]. Author Contributions
C.C. and L.M. contributed equally to this work. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by a grant from AIRC Special Program Molecular Clinical Oncology “5 per mille”.
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REFERENCES
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CONCLUSION In this work, PEGylated caprolactone-based NPs were synthesized via emulsion polymerization of functionalized oligomers. The NPs were loaded with Paclitaxel to produce a Cremophor-free formulation suitable for intravenous delivery of this compound. In vitro release experiments were carried out in a BSA solution and show a remarkably slower release of PTX for the NPs compared to the free drug. The produced formulation was tested in vivo against the MDA-MB-231 model and showed overall similar biodistribution to the standard formulation as well as a comparable antitumor activity, suggesting that the majority of the drug is released rapidly after injection. In addition, the slow PTX release observed in vitro did not lead to significant differences during in vivo experiments, giving a clear proof on the difficulties in translate in vitro to in vivo results. The evolution of the body weight of the animals suggest low toxicity of the produced NPs, thus making them as an alternative to the standard formulation for the delivery of PTX.
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AUTHOR INFORMATION
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.molpharmaceut.5b00383. Characterization of HEMA-CL3 macromonomer, schematization of the drug loading device, core−shell nanoparticles. (PDF) F
DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
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DOI: 10.1021/acs.molpharmaceut.5b00383 Mol. Pharmaceutics XXXX, XXX, XXX−XXX
