Norbornene derived doxorubicin copolymers as drug carriers with pH responsive hydrazone linker

The synthesis and complete characterization of both norbornene-derived doxorubicin (mono 1) and polyethylene glycol (mono 2) monomers are clearly described, and their copolymerization by ring-opening metathesis polymerization (ROMP) to get the block copolymer (COPY-DOX) is vividly elaborated. The careful design of these conjugates exhibits properties like well-shielded drug moieties and well-defined nanostructures; additionally, they show solubility in both water and biological medium and also have the important tendency of rendering acid-triggered drug release. The drug release profile suggests the importance of having the hydrazone linker that helps to release the drug exactly at the mild acidic conditions resembling the pH of the cancerous cells. It is also observed that the drug release from micelles of COPY-DOX is significantly accelerated at a mildly acidic pH of 5.5-6, compared to the physiological pH of 7.4, suggesting the pH-responsive feature of the drug delivery system with hydrazone linkages. Confocal laser scanning microscopy (CLSM) measurements indicate that these COPY-DOX micelles are easily internalized by living cells. MTT assays against HeLa and 4T cancer cells showing COPY-DOX micelles have a high anticancer efficacy. All of these results demonstrate that these polymeric micelles that self-assembled from COPY-DOX block copolymers have great scope in the world of medicine, and they also symbolize promising carriers for the pH-triggered intracellular delivery of hydrophobic anticancer drugs.     

Cytotoxicity of doxrubicin loaded single-walled carbon nanotubes

Carbon nanotube (CNTs) is a new alternative for efficient drug delivery and it has a great potential to change drug delivery system profile in pharmaceutical industry. One of the important advantage of CNTs is their needle-like, cylindrical shape. This shape provides a high surface area for multiple connections and adsorption onto for millions of therapeutic molecules. CNTs can be internalized by cells via endocytosis, passive diffusion and phagocytosis and release the drug with different effects like pH and temperature. The acidic nature of cancer cells and the susceptibility of CNTs to release the drug in the acidic environment have made it a promising area of research in cancer drug delivery. In this research, we investigated cell viability, cytotoxicity and drug delivery in breast cancer cell line by designing non-covalent single walled carbon nanotubes (SWNT)–doxorubicin (DOX) supramolecular complex that can be developed for cancer therapy. Applied high concentrations of DOX loaded SWNTs changed the actin structure of the cells and prevented the proliferation of the cells. It was showed that doxorubicin loaded SWNTs were more effective than free doxorubicin at relatively small concentrations. Once we applied same procedure for short and long (short: 1–1.3 µm; long: 2.5–4 µm) SWNTs and compared the results, more disrupted cell structure and reduction in cell proliferation were observed for long CNTs. DOX is bounded more to nanotubes in basic medium, less bound in acidic environment. Cancer cells were also examined for concentration at which they were effective by applying DOX and it was seen that 3.68 µM doxorubicin kills more than 55% of the cells.     

pH and reduction dual-sensitive copolymeric micelles for intracellular doxorubicin delivery

This study develops novel pH and reduction dual-sensitive micelles for the anticancer drug doxorubicin (DOX) delivery owing to the fact that the tumor tissues show low pH and high reduction environment. These sub-100 nm micelles present a core-shell structure under physiological conditions, but quickly release the loaded drugs responding to acidic and reductive stimuli. With disulfide bonds in each repeat unit of poly(β-amino ester)s, the novel copolymer was synthesized via Michael addition polymerization from 2,2'-dithiodiethanol diacrylate, 4,4'-trimethylene dipiperidine, and methoxy-PEG-NH(2). DOX released faster from micelles in a weakly acidic environment (pH 6.5) than at pH 7.4 or in the presence of a higher concentration (5 mM) of reducing agent (DTT). The release is even more effective in a scenario of both stimuli (pH 6.5 and 5 mM DTT). MTT assay showed that the DOX-loaded micelles had a higher cytotoxicity for HepG2 tumor cells than DOX at higher concentrations, and that blank micelles had a very low cytotoxicity to the tumor cells. Confocal microscopy observation showed that the micelles can be quickly internalized, effectively deliver the drugs into nuclei, and inhibit cell growth. These results present the copolymer as a novel and effective pH and reduction dual-responsive nanocarrier to enhance drug efficacy for cancer cells.     

pH-Responsive copolymer assemblies for controlled release of doxorubicin

pH-Responsive drug carriers have the potential to provide selective drug release at therapeutic targets including tumors and in acidic intracellular vesicles such as endosomes and lysosomes. We have developed a new approach to the design of acid-sensitive micelles by incorporating hydrophobic acetal groups on the core block of a micelle-forming block copolymer. Hydrolysis of the acetals at mildly acidic pH is designed to reveal polar groups on the core-forming block, thus changing its solubility and disrupting the micelle, triggering drug release. The anticancer drug doxorubicin (DOX) was encapsulated in these pH-sensitive micelles, and the acetal hydrolysis rates and DOX release rates were determined in the pH range of 4.0 to 7.4 and were compared to those of control systems. The micelle disruption was investigated by dynamic light scattering. The in vitro toxicities of the empty and DOX-loaded micelles were determined, and the intracellular fate of the encapsulated DOX was compared to free DOX using fluorescence confocal microscopy.     

Immobilization and intracellular delivery of an anticancer drug using mussel-inspired polydopamine capsules

We report a facile approach to immobilize pH-cleavable polymer-drug conjugates in mussel-inspired polydopamine (PDA) capsules for intracellular drug delivery. Our design takes advantage of the facile PDA coating to form capsules, the chemical reactivity of PDA films, and the acid-labile groups in polymer side chains for sustained pH-induced drug release. The anticancer drug doxorubicin (Dox) was conjugated to thiolated poly(methacrylic acid) (PMA(SH)) with a pH-cleavable hydrazone bond, and then immobilized in PDA capsules via robust thiol-catechol reactions between the polymer-drug conjugate and capsule walls. The loaded Dox showed limited release at physiological pH but significant release (over 85%) at endosomal/lysosomal pH. Cell viability assays showed that Dox-loaded PDA capsules enhanced the efficacy of eradicating HeLa cancer cells compared with free drug under the same assay conditions. The reported method provides a new platform for the application of stimuli-responsive PDA capsules as drug delivery systems.     

Fabrication and Intracellular Delivery of Doxorubicin/Carbonate Apatite Nanocomposites: Effect on Growth Retardation of Established Colon Tumor

In continuing search for effective treatments of cancer, the emerging model aims at efficient intracellular delivery of therapeutics into tumor cells in order to increase the drug concentration. However, the implementation of this strategy suffers from inefficient cellular uptake and drug resistance. Therefore, pH-sensitive nanosystems have recently been developed to target slightly acidic extracellular pH environment of solid tumors. The pH targeting approach is regarded as a more general strategy than conventional specific tumor cell surface targeting approaches, because the acidic tumor microclimate is most common in solid tumors. When nanosystems are combined with triggered release mechanisms in endosomal or lysosomal acidic pH along with endosomolytic capability, the nanocarriers demonstrated to overcome multidrug resistance of various tumors. Here, novel pH sensitive carbonate apatite has been fabricated to efficiently deliver anticancer drug Doxorubicin (DOX) to cancer cells, by virtue of its pH sensitivity being quite unstable under an acidic condition in endosomes and the desirable size of the resulting apatite-DOX for efficient cellular uptake as revealed by scanning electron microscopy. Florescence microscopy and flow cytometry analyses demonstrated significant uptake of drug (92%) when complexed with apatite nanoparticles. In vitro chemosensitivity assay revealed that apatite-DOX nanoparticles executed high cytotoxicity in several human cancer cell lines compared to free drugs and consequently apatite-DOX-facilitated enhanced tumor inhibitory effect was observed in colorectal tumor model within BALB/cA nude mice, thereby shedding light on their potential applications in cancer therapy.     

D-甘露糖修饰聚合物胶束的制备及其在靶向药物输送中的应用

聚合物胶束作为药物载体具有良好的稳定性和生物相容性,提高疏水性药物溶解性等优势,是一类很有应用潜力的药物传输系统。本研究以合成的共价键连D-甘露糖的双亲性聚合物分子(PGMA-Mannose)为药物载体,包载抗癌药物阿霉素(DOX)制备具有甘露糖受体靶向性和pH敏感药物释放特性的新型载药聚合物胶束。利用激光共聚焦显微镜和MTT细胞毒性评价方法对载药胶束的细胞内吞摄取和毒性进行评价。实验结果表明,载药胶束能特异性识别人乳腺癌细胞MDA-MB-231表面过度表达的甘露糖受体,被癌细胞大量摄取并在细胞溶酶体酸性环境内释放药物,而载药胶束在表面甘露糖受体低表达的HEK293细胞中只有少量摄取。与原药DOX相比,该载药胶束对癌细胞的毒性显著提高,而对正常细胞的毒性较低。因此,该PGMA-Mannose聚合物胶束有望成为一种新型的靶向药物输送系统应用于癌症的治疗。     

Design of acid-activated cell penetrating peptide for delivery of active molecules into cancer cells

TP10-5 (TK) was screened as the most promising candidate among the designed analogues of transportan 10 (TP10), a cell penetrating peptide (CPP) with remarkable capacity for membrane translocation. However, low levels of specificity and high toxicity limit its successful use for drug delivery applications. Here, we developed a new type of acid-activated CPP (TH) by replacement of all lysines of TK with histidines. As expected, histidine-containing TH can be activated and subsequently enter cells at pH 6.0, whereas it is less active at pH 7.4. In contrast, the uptake of TK has no significant difference for both pH values. Importantly, the toxicity of TH is significantly lower than that of TK under physiological conditions. After attachment of camptothecin (CPT) to TH, this conjugate exhibited remarkable cytotoxicity to cancer cells in a pH-dependent manner compared with free CPT and TK-CPT. This study opens a new avenue to design CPPs that preferentially enter cells in acidic solid tumors, with minimal cellular uptake in normal tissues.     

Polyketal nanoparticles: a new pH-sensitive biodegradable drug delivery vehicle

In this report, we present an acid-sensitive drug delivery vehicle, termed polyketal nanoparticles, which are designed to target therapeutics to the acidic environments of tumors, inflammatory tissues, and phagosomes. The polyketal nanoparticles are formulated from poly(1,4-phenyleneacetone dimethylene ketal) (PPADK), a new hydrophobic polymer which contains ketal linkages in its backbone. The polyketal nanoparticles undergo acid-catalyzed hydrolysis into low molecular weight hydrophilic compounds and should therefore release encapsulated therapeutics at an accelerated rate in acidic environments. Importantly, the polyketal nanoparticles do not generate acidic degradation products after hydrolysis, as with polyester-based biomaterials. Dexamethasone-loaded nanoparticles, 200-600 nm in diameter, were fabricated with PPADK via an emulsion procedure using chloroform and water. The hydrolysis half-life of PPADK was measured to be 102 h at pH 7.4 and 35 h at pH 5.0. PPADK was synthesized by a new polymerization strategy based on the acetal exchange reaction. This new delivery system should find numerous applications in the field of drug delivery because of its ease of synthesis and excellent degradation properties.     

Ketal cross-linked poly(ethylene glycol)-poly(amino acid)s copolymer micelles for efficient intracellular delivery of doxorubicin

A biocompatible, robust polymer micelle bearing pH-hydrolyzable shell cross-links was developed for efficient intracellular delivery of doxorubicin (DOX). The rationally designed triblock copolymer of poly(ethylene glycol)-poly(L-aspartic acid)-poly(L-phenylalanine) (PEG-PAsp-PPhe) self-assembled to form polymer micelles with three distinct domains of the PEG outer corona, the PAsp middle shell, and the PPhe inner core. Shell cross-linking was performed by the reaction of ketal-containing cross-linkers with Asp moieties in the middle shells. The shell cross-linking did not change the micelle size and the spherical morphology. Fluorescence quenching experiments confirmed the formation of shell cross-linked diffusion barrier, as judged by the reduced Stern-Volmer quenching constant (K(SV)). Dynamic light scattering and fluorescence spectroscopy experiments showed that shell cross-linking improved the micellar physical stability even in the presence of micelle disrupting surfactants, sodium dodecyl sulfate (SDS). The hydrolysis kinetics study showed that the hydrolysis half-life (t(1/2)) of ketal cross-links was estimated to be 52 h at pH 7.4, whereas 0.7 h at pH 5.0, indicating the 74-fold faster hydrolysis at endosomal pH. Ketal cross-linked micelles showed the rapid DOX release at endosomal pH, compared to physiological pH. Confocal laser scanning microscopy (CLSM) showed that ketal cross-linked micelles were taken up by the MCF-7 breast cancer cells via endocytosis and transferred into endosomes to hydrolyze the cross-links by lowered pH and finally facilitate the DOX release to inhibit proliferation of cancer cells. This ketal cross-linked polymer micelle is promising for enhanced intracellular delivery efficiency of many hydrophobic anticancer drugs.     

Supramolecular copolymer micelles based on the complementary multiple hydrogen bonds of nucleobases for drug delivery

Novel supramolecular copolymer micelles with stimuli-responsive abilities were successfully prepared through the complementary multiple hydrogen bonds of nucleobases and then applied for rapid intracellular release of drugs. First, both adenine-terminated poly(ε-caprolactone) (PCL-A) and uracil-terminated poly(ethylene glycol) (PEG-U) were synthesized. The supramolecular amphiphilic block copolymers (PCL-A:U-PEG) were formed based on multiple hydrogen bonding interactions between PCL-A and PEG-U. The micelles self-assembled from PCL-A:U-PEG were sufficiently stable in water but prone to fast aggregation in acidic condition due to the dynamic and sensitive nature of noncovalent interactions. The low cytotoxicity of supramolecular copolymer micelles was confirmed by MTT assay against NIH/3T3 normal cells. As a hydrophobic anticancer model drug, doxorubicin (DOX) was encapsulated into these supramolecular copolymer micelles. In vitro release studies demonstrated that the release of DOX from micelles was significantly faster at mildly acid pH of 5.0 compared to physiological pH. MTT assay against HeLa cancer cells showed DOX-loaded micelles had high anticancer efficacy. Hence, these supramolecular copolymer micelles based on the complementary multiple hydrogen bonds of nucleobases are very promising candidates for rapid controlled release of drugs.     

Polyester dendritic systems for drug delivery applications: in vitro and in vivo evaluation

High molecular weight polymers (> 20 000 Da) have been widely used as soluble drug carriers to improve drug targeting and therapeutic efficacy. Dendritic polymers are exceptional candidates for the preparation of near monodisperse drug carriers due to their well-defined structure, multivalency, and flexibility for tailored functionalization. We evaluated various dendritic architectures composed of a polyester dendritic scaffold based on the monomer unit 2,2-bis(hydroxymethyl)propanoic acid for their suitability as drug carriers both in vitro and in vivo. These systems are both water soluble and nontoxic. In addition, the potent anticancer drug, doxorubicin, was covalently bound via a hydrazone linkage to a high molecular weight 3-arm poly(ethylene oxide)-dendrimer hybrid. Drug release was a function of pH, and the release rate was more rapid at pH < 6. The cytotoxicity of the DOX-polymer conjugate measured on multiple cancer lines in vitro was reduced but not eliminated, indicating that some active doxorubicin was released from the drug polymer conjugate under physiological conditions. Furthermore, biodistribution experiments show little accumulation of the DOX-polymer conjugate in vital organs, and the serum half-life of doxorubicin attached to an appropriate high molecular weight polymer has been significantly increased when compared to the free drug. Thus, this new macromolecular system exhibits promising characteristics for the development of new polymeric drug carriers.     

Importance of intracellular pH in determining the uptake and efficacy of the weakly basic chemotherapeutic drug, doxorubicin

Low extracellular pH (pH(e)), that is characteristic of many tumours, tends to reduce the uptake of weakly basic drugs, such as doxorubicin, thereby conferring a degree of physiological resistance to chemotherapy. It has been assumed, from pH-partition theory, that the effect of intracellular pH (pH(i)) is symmetrically opposite, although this has not been tested experimentally. Doxorubicin uptake into colon HCT116 cells was measured using the drug's intrinsic fluorescence under conditions that alter pH(i) and pH(e) or pH(i) alone. Acutely, doxorubicin influx across the cell-membrane correlates with the trans-membrane pH-gradient (facilitated at alkaline pH(e) and acidic pH(i)). However, the protonated molecule is not completely membrane-impermeant and, therefore, overall drug uptake is less pH(e)-sensitive than expected from pH-partitioning. Once inside cells, doxorubicin associates with slowly-releasing nuclear binding sites. The occupancy of these sites increases with pH(i), such that steady-state drug uptake can be greater with alkaline cytoplasm, in contradiction to pH-partition theory. Measurements of cell proliferation demonstrate that doxorubicin efficacy is enhanced at alkaline pH(i) and that pH-partition theory is inadequate to account for this. The limitations in the predictive power of pH-partition theory arise because it only accounts for the pH(i)/pH(e)-sensitivity of drug entry into cells but not the drug's subsequent interactions that, independently, show pH(i)-dependence. In summary, doxorubicin uptake into cells is favoured by high pH(e) and high pH(i). This modified formalism should be taken into account when designing manoeuvres aimed at increasing doxorubicin efficacy.     

SYNTHESIS OF FOLATE RECEPTOR-TARGETED AND DOXORUBICIN-COUPLED CHEMOTHERAPEUTIC NANOCONJUGATE AND RESEARCH INTO ITS MEDICAL APPLICATIONS

Folate-targeted drug delivery has become an alternative therapy for the treatment of various cancers. Folate receptors are known to be responsible for cellular accumulation of folate and folate analogs with high binding affinity. The anthracycline antibiotic doxorubicin has a broad spectrum of antineoplastic action and a correspondingly widespread degree of clinical use. In this work, we aimed to prepare a folate receptor-targeted doxorubicin delivery system to achieve minimal effect of doxorubicin on healthy cells and more cytotoxicity of it on tumor cells. Folate–poly(ethylene glycol)–doxorubicin (FOL-PEG-DOX) nanoconjugate was synthesized through this aim and characterized with nuclear magnetic resonance (NMR), zetasizer, and atomic force microscopy (AFM). Doxorubicin release studies were also performed in vitro. The size of FOL-PEG-DOX was 78.84 nm. The results indicated that doxorubicin release rate from the conjugate was faster at pH 5.0 than pH 7.4 and the amide bond between DOX and PEG was more stable at pH 7.4 than pH 5.0. As a consequence, FOL-PEG-DOX nanoconjugate could be a potentially useful delivery system for folate receptor-positive cancer cells.     

双模态纳米诊疗一体药物在肝癌动物模型中的应用

摘要 目的：构建一种肿瘤诊断和治疗一体化药物，并利用肝癌动物模型开展诊疗效能评价。方法：利用多孔金属有机骨架材料ZIF-8，通过配位作用同时对化疗药物阿霉素（DOX）和近红外荧光染料IR-820进行负载。而后，利用超声的方法在ZIF-8-IR-820-DOX表面修饰了红细胞膜以提高载药体系的生物安全性和稳定性，得到具有生物伪装特性的pH响应型ZIF-8-IR-820-DOX@RM纳米颗粒。最后，通过对该药物体系的粒径、表面电位、形貌等理化性质进行表征，并利用肝癌动物模型验证该药物的诊断和治疗效能。结果：成功构建了一款红细胞伪装的金属框架纳米诊疗一体试剂，该试剂具有较好的pH相应性，在肿瘤pH 5.5 条件下，药物的释放率达到98.4 %，而在机体正常pH 7.4条件下，释放率仅为15.3 %。在小鼠肝癌动物模型的诊疗过程中，能通过近红外荧光较好的识别肿瘤的位置和大小，且对小鼠肿瘤具有较好的治疗效果。结论：本研究所构建的ZIF-8-IR-820-DOX @RM能通过肿瘤处增强的渗透性和保留（EPR）效应，精准的到达肿瘤部位，并利用pH响应性，在肿瘤酸性环境中精准释放携带的抗肿瘤药物和近红外荧光成像试剂，实现对肿瘤的诊断和治疗一体化设计。为肿瘤治疗的相关研究提供了一种思路和借鉴。     

pH-sensitive polymer nanospheres for use as a potential drug delivery vehicle

We report the development and characterization of pH-sensitive poly(2-tetrahydropyranyl methacrylate) [poly(THPMA)] nanospheres and demonstrate their feasibility as an effective drug delivery vehicle. Poly(THPMA) nanospheres were prepared using either the double emulsion or single emulsion method for the encapsulation of, respectively, water soluble (rhodamine B) or organic soluble (paclitaxel) payloads. The resulting nanospheres showed pH-dependent dissolution behavior, resulting in significant morphologic changes and loss of nanoparticle mass under mild acidic conditions (pH 5.1) with a half-life of 3.3 days, as compared to physiologic condition (pH 7.4) with a half-life of 6.2 days. The in vitro drug release profile of the paclitaxel-loaded poly(THPMA) nanospheres revealed that the rate of drug release in pH 5.1 acetate buffer was relatively faster than that in pH 7.4 HEPES buffer. Furthermore, poly(THPMA) nanospheres showed lower cytotoxicity and higher cellular uptake as compared to the FDA-approved PLGA-based nanospheres currently in clinical practice.     

New conjugates of antitumor antibiotic doxorubicin with water-soluble galactomannan: synthesis and biological activity

New water-soluble conjugates in the form of Schiff bases (DGM-1 and DGM-2) were prepared by the interaction of water-soluble periodate-oxidized galactomannan with doxorubicin or N-(L-lysyl)doxorubicin, respectively. The water-soluble galactomannan (DAVANAT a commercial product of Pro-Pharmaceuticals company) was obtained by partial acidic hydrolysis of high-molecular-mass galactomannan from Cyamopsis tetragonoloba (guar gum) seeds. The conjugate stability was studied in aqueous solutions. The DGM-1 antiproliferative activity was comparable with that of doxorubicin on three models: cell lines of murine melanoma B 16-F1, human breast cancer MCF-7 (HTB-22), and human colon cancer HT-29 (HTB-38). DGM-2 was poorly active in all the three tests. DGM- 1 can thus be regarded as a high-molecular-mass depot form of doxorubicin.     

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pH_e) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pH_e-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pH_e-activated NPs, with special emphasis on pH_e-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.     

Structural effects and lipid membrane interactions of the pH-responsive GALA peptide with fatty acid acylation

GALA is a pH-responsive, membrane-perturbing peptide designed to fold from a random coil at physiological pH to an amphipathic α-helix under mildly acidic conditions. Because of its pH-activated function, GALA has been sought-after as a component of intracellular drug delivery systems that could actively propel endosomal escape. In this study, we conjugated GALA with lauryl and palmitoyl fatty acid tails as model hydrophobic moieties and examined the physicochemical characteristics and activities of the resulting peptide amphiphiles (PAs). The fatty acid variants of GALA exhibited distinctly different membrane perturbing mechanisms at pH 7.5 and 5.5. At physiological pH, the PAs ruptured liposomes through a surfactant-like mechanism. At pH 5.5, lauryl-GALA was shown to form transmembrane pores with a higher potency as compared to its unmodified peptide counterpart; however, after prolonged exposure it also caused liposome lysis. The lytic activity of fatty acid-conjugated GALA did not impair cell viability. Lauryl-GALA was tolerated well by SJSA-1 osteocarcinoma cells and enhanced cell internalization of the PA was observed. Our findings are discussed with the overarching goal of developing efficient therapeutic delivery systems.     

Hyperbranched double hydrophilic block copolymer micelles of poly(ethylene oxide) and polyglycerol for pH-responsive drug delivery

We report the synthesis of a well-defined hyperbranched double hydrophilic block copolymer of poly(ethylene oxide)-hyperbranched-polyglycerol (PEO-hb-PG) to develop an efficient drug delivery system. In specific, we demonstrate the hyperbranched PEO-hb-PG can form a self-assembled micellar structure on conjugation with the hydrophobic anticancer agent doxorubicin, which is linked to the polymer by pH-sensitive hydrazone bonds, resulting in a pH-responsive controlled release of doxorubicin. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy demonstrated successful formation of the spherical core-shell type micelles with an average size of about 200 nm. Moreover, the pH-responsive release of doxorubicin and in vitro cytotoxicity studies revealed the controlled stimuli-responsive drug delivery system desirable for enhanced efficiency. Benefiting from many desirable features of hyperbranched double hydrophilic block copolymers such as enhanced biocompatibility, increased water solubility, and drug loading efficiency as well as improved clearance of the polymer after drug release, we believe that double hydrophilic block copolymer will provide a versatile platform to develop excellent drug delivery systems for effective treatment of cancer.