PH responsive polypeptide based polymeric micelles for anticancer drug delivery Dongping Zhao,1 Bingqiang Li,1 Jiaming Han,1 Yue Yang,1 Xinchen Zhang,1 Guolin Wu,1* 1
Key Laboratory of Functional Polymer Materials of MOE, Institute of Polymers,
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China *To whom correspondence should be addressed at: Key Laboratory of Functional Polymer Materials, Institute of Polymer Chemistry, Nankai University, Tianjin 300071, PR China E-mail address: [email protected] Fax: +86 22 23502749 Phone: +86 22 23507746
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/jbm.a.35434 This article is protected by copyright. All rights reserved.
Journal of Biomedical Materials Research: Part A
Abstract: A pH-responsive polymeric micelle based on poly(aspartamide) derivative was explored as an efficient acid-triggered anticancer drug delivery system. poly(α,β-L-asparthydrazide) (PAHy) was prepared by aminolysis reaction of polysuccinimide with hydrazine hydrate. Poly(ethylene glycol) and aliphatic chain (C18) were conjugated onto PAHy to afford an amphiphilic copolymer with acid-liable hydrazone bonds. The structure of the resulting copolymer and its self-assembled micelles were confirmed by 1H NMR, FTIR, DLS and TEM. Furthermore, doxorubicin (DOX) was loaded into the polymeric micelles via the hydrophobic interaction between the C18 group and DOX molecules, and also the π-π staking between the hydrazone conjugated DOX and free DOX molecules. Results showed that the DOX loaded nanoparticle was relatively stable under physiological conditions, while the DOX was quickly released in response to acidity due to the shedding of mPEG shells and dissociating of C18 segments because of the pH-cleavage of intermediate hydrazone bonds. In addition, the doxorubicin loaded micelles presented a high cytotoxic activity against tumor cells in vitro. This pH responsive nanoparticle has appeared highly promising for the targeted intracellular delivery of hydrophobic chemotherapeutics in cancer therapy. Keywords
poly(aspartamide), pH-sensitive, drug delivery, hydrazone, micelle
John Wiley & Sons, Inc. This article is protected by copyright. All rights reserved.
Page 2 of 38
Page 3 of 38
Journal of Biomedical Materials Research: Part A
INTRODUCTION Polymeric micelles with core-shell architecture formed by amphiphilic block copolymers have been extensively studied for anticancer drug carrier.1-5 Such polymeric micelles can improve the bioavailability of loaded drugs, prolong the circulation time in blood stream and passively targeting the drug based on the enhanced permeability and retention (EPR) effect.6,7,8 For drug delivery nanocarriers, surface modication of nanoparticles (NPs) with polyethylene glycol (PEG), the so-called PEGylation, is the most commonly used approach for reducing the premature clearance of NPs from circulation. However, after arriving at the pathological site, nanocarriers should be able to deliver their payloads in an efficient manner. It was reported that the PEGylated surfaces limit the interactions between the carriers and target tissues and sequentially diminish cellular uptake of the loaded cargo.9,10 Therefore, great efforts have been made to circumvent these problems. PEG-sheddable nanoparticles, which are capable of shedding their outer layers when needed, may facilitate the drug release as well as the interaction with the target cell. Nanoparticles with pH-sheddable PEG layers conjugated via an acid-cleavable linkage have been reported to enhance intracellular drug delivery due to the different local pHs in blood plasma (pH 7.4) and extracellular tumor matrices (pH 5.8-7.2), as well as the more acidic endosome (pH 5.0-6.0) and lysosome (pH 4.0-5.0) in endocytic compartments. Yang and his co-worker reported an amphiphilic copolymer synthesized by conjugating PEG and a hydrophobic block via benzoic-imine bonds.11,12 Compared
John Wiley & Sons, Inc. This article is protected by copyright. All rights reserved.
Journal of Biomedical Materials Research: Part A
with the imine bond, the benzoic-imine linker is more stable at neutral and basic pH due to the extended π-π conjugation, and is cleavable following a decrease in pH. Recently, a magnetic and pH dually responsive nanocarrier with a multilayer core-shell architecture was prepared in our group, which was based on the magnetic nanoparticles successively coated with poly(benzyl L-aspartate) and PEG for the purpose of tumor specific drug delivery application. In this system, PEG chains are connected to the surface via pH-sensitive benzoic-imine bonds and serve as a pH-sheddable hydrophilic corona. 13,14 In addition to benzoic-imine bond, there are some other acid-cleavable linkages such as hydrazone,15-17 thiopropionate,18,19 acetal,20-22 and orthoester,23,24 which can be used to design the pH-responsive polymers. Hydrazone linkage is fairly stable at neutral pH but rapidly hydrolyzes in the acidic environment at pH
Key Laboratory of Functional Polymer Materials of MOE, Institute of Polymers,
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China *To whom correspondence should be addressed at: Key Laboratory of Functional Polymer Materials, Institute of Polymer Chemistry, Nankai University, Tianjin 300071, PR China E-mail address: [email protected] Fax: +86 22 23502749 Phone: +86 22 23507746
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/jbm.a.35434 This article is protected by copyright. All rights reserved.
Journal of Biomedical Materials Research: Part A
Abstract: A pH-responsive polymeric micelle based on poly(aspartamide) derivative was explored as an efficient acid-triggered anticancer drug delivery system. poly(α,β-L-asparthydrazide) (PAHy) was prepared by aminolysis reaction of polysuccinimide with hydrazine hydrate. Poly(ethylene glycol) and aliphatic chain (C18) were conjugated onto PAHy to afford an amphiphilic copolymer with acid-liable hydrazone bonds. The structure of the resulting copolymer and its self-assembled micelles were confirmed by 1H NMR, FTIR, DLS and TEM. Furthermore, doxorubicin (DOX) was loaded into the polymeric micelles via the hydrophobic interaction between the C18 group and DOX molecules, and also the π-π staking between the hydrazone conjugated DOX and free DOX molecules. Results showed that the DOX loaded nanoparticle was relatively stable under physiological conditions, while the DOX was quickly released in response to acidity due to the shedding of mPEG shells and dissociating of C18 segments because of the pH-cleavage of intermediate hydrazone bonds. In addition, the doxorubicin loaded micelles presented a high cytotoxic activity against tumor cells in vitro. This pH responsive nanoparticle has appeared highly promising for the targeted intracellular delivery of hydrophobic chemotherapeutics in cancer therapy. Keywords
poly(aspartamide), pH-sensitive, drug delivery, hydrazone, micelle
John Wiley & Sons, Inc. This article is protected by copyright. All rights reserved.
Page 2 of 38
Page 3 of 38
Journal of Biomedical Materials Research: Part A
INTRODUCTION Polymeric micelles with core-shell architecture formed by amphiphilic block copolymers have been extensively studied for anticancer drug carrier.1-5 Such polymeric micelles can improve the bioavailability of loaded drugs, prolong the circulation time in blood stream and passively targeting the drug based on the enhanced permeability and retention (EPR) effect.6,7,8 For drug delivery nanocarriers, surface modication of nanoparticles (NPs) with polyethylene glycol (PEG), the so-called PEGylation, is the most commonly used approach for reducing the premature clearance of NPs from circulation. However, after arriving at the pathological site, nanocarriers should be able to deliver their payloads in an efficient manner. It was reported that the PEGylated surfaces limit the interactions between the carriers and target tissues and sequentially diminish cellular uptake of the loaded cargo.9,10 Therefore, great efforts have been made to circumvent these problems. PEG-sheddable nanoparticles, which are capable of shedding their outer layers when needed, may facilitate the drug release as well as the interaction with the target cell. Nanoparticles with pH-sheddable PEG layers conjugated via an acid-cleavable linkage have been reported to enhance intracellular drug delivery due to the different local pHs in blood plasma (pH 7.4) and extracellular tumor matrices (pH 5.8-7.2), as well as the more acidic endosome (pH 5.0-6.0) and lysosome (pH 4.0-5.0) in endocytic compartments. Yang and his co-worker reported an amphiphilic copolymer synthesized by conjugating PEG and a hydrophobic block via benzoic-imine bonds.11,12 Compared
John Wiley & Sons, Inc. This article is protected by copyright. All rights reserved.
Journal of Biomedical Materials Research: Part A
with the imine bond, the benzoic-imine linker is more stable at neutral and basic pH due to the extended π-π conjugation, and is cleavable following a decrease in pH. Recently, a magnetic and pH dually responsive nanocarrier with a multilayer core-shell architecture was prepared in our group, which was based on the magnetic nanoparticles successively coated with poly(benzyl L-aspartate) and PEG for the purpose of tumor specific drug delivery application. In this system, PEG chains are connected to the surface via pH-sensitive benzoic-imine bonds and serve as a pH-sheddable hydrophilic corona. 13,14 In addition to benzoic-imine bond, there are some other acid-cleavable linkages such as hydrazone,15-17 thiopropionate,18,19 acetal,20-22 and orthoester,23,24 which can be used to design the pH-responsive polymers. Hydrazone linkage is fairly stable at neutral pH but rapidly hydrolyzes in the acidic environment at pH
