SCIENCE CHINA Materials, Volume 61, Issue 11: 1462-1474(2018) https://doi.org/10.1007/s40843-018-9277-8

Enzyme/pH-sensitive dendritic polymer-DOX conjugate for cancer treatment

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  • ReceivedFeb 20, 2018
  • AcceptedApr 10, 2018
  • PublishedMay 22, 2018


It is in a great demand to design a biodegradable, tumor microenvironment-sensitive drug delivery system to achieve safe and highly efficacious treatment of cancer. Herein, a novel pH/enzyme sensitive dendritic pdiHPMA-DOX conjugate was designed. diHPMA dendritic copolymer with GFLG segments in the branches which are sensitive to the intracellular enzyme of the tumor was prepared through RAFT polymerization. DOX was attached to dendritic diHPMA polymer through a pH-sensitive hydrazone bond. The dendritic pdiHPMA-DOX conjugate self-assembled into nanoparticles with an ideal spherical shape at a mean size of 103 nm. The DOX attached to the polymeric carrier was released in an acidic environment, and the GFLG linker for synthesizing the dendritic vehicle with a high molecular weight (MW, 220 kDa) was cleaved to release low MW segments (<40 kDa) in the presence of cathepsin B. The dendritic polymeric conjugate was internalized via an endocytic pathway, and then released the anticancer drug, which led to significant cytotoxicity for tumors. The blood circulation time was profoundly prolonged, resulting in high accumulation of DOX into tumors. In vivo anti-tumor experiments with 4T1 tumor bearing mice demonstrated that the conjugate had a better antitumor efficacy in comparison with free DOX. Additionally, body weight measurements and histological examinations indicated that the conjugate showed low toxicities to normal tissues. This dendritic polymeric drug carrier in a response to intracellular enzyme and acidic pH of tumor tissue or cells holds great promise in tumor-targeted therapy.

Funded by

the National Natural Science Foundation of China(51673127,8162103)

International Science and Technology Cooperation Program of China(2015DFE52780,81220108013)

International Science and Technology Cooperation Program of Chengdu(2016-GH03-00005-HZ)


This work was supported by the National Natural Science Foundation of China (51673127 and 8162103), International Science and Technology Cooperation Program of China (2015DFE52780 and 81220108013) and International Science and Technology Cooperation Program of Chengdu (2016-GH03-00005-HZ).

Interest statement

The authors declare that they have no conflict of interest.

Contributions statement

Chen K designed the study, performed the experiments, analyzed the data, and wrote the manuscript. Liao S and Guo S performed experiments. Zhang H and Cai H analyzed the data, wrote the manuscript. Gong Q, Gu Z and Luo K designed the study, wrote the manuscript and they are responsible for funding support, resources and project administration.

Author information

Kai Chen received his BSc degree from Army Medical University (Third Military Medical University), Chongqing, in 2015. Now he is a PhD candidate at the National Engineering Research Center for Biomaterials, Sichuan University. His current research focuses on the treatment of breast cancer with enzyme/pH sensitive polymer-drug conjugates-based nanoscale delivery system.

Kui Luo is a Professor in West China Hospital and National Engineering Research Center for Biomaterials, Sichuan University, China. He obtained his PhD degree from the National Engineering Research Center for Biomaterials, Sichuan University in 2009, and then became an assistant professor in this center. From 2009 to 2011, he carried out his postdoctoral work on polymeric nanomedicines at the Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, USA. Dr. Luo was promoted to an associate professor in 2012 and Full Professor in 2013 in Sichuan University. From 2016, he was also a Full professor in Huaxi MR Research Center (HMRRC), Department of Radiology, West China Hospital, Sichuan University. His research focuses on stimuli-responsive and biodegradable polymeric gene/drug delivery vehicles and imaging probes for cancer diagnosis and therapy, especially the study of synthetic macromolecules as potential cancer therapeutic and diagnostic agents, and the relationships between their actions and structural features.


Supplementary information

Supporting data are available in the online version of the paper.


[1] Li H, Ding Y, Ha H, et al. An all-stretchable-component sodium-ion full battery. Adv Mater, 2017, 29: 1700898 CrossRef PubMed Google Scholar

[2] Treml BE, McKenzie RN, Buskohl P, et al. Soft robotics: autonomous motility of polymer films. Adv Mater, 2018, 30: 1870046 CrossRef Google Scholar

[3] Wang F, Xiao J, Chen S, et al. Polymer vesicles: modular platforms for cancer theranostics. Adv Mater, 2018, 28: 1705674 CrossRef PubMed Google Scholar

[4] Liu Y, Li M, Yang F, et al. Magnetic drug delivery systems. Sci China Mater, 2017, 60: 471-486 CrossRef Google Scholar

[5] Jia Q, Chen M, Liu Q, et al. Ethylene glycol-mediated synthetic route for production of luminescent silicon nanorod as photodynamic therapy agent. Sci China Mater, 2017, 60: 881-891 CrossRef Google Scholar

[6] Webber MJ, Langer R. Drug delivery by supramolecular design. Chem Soc Rev, 2017, 46: 6600-6620 CrossRef PubMed Google Scholar

[7] Cai H, Wang X, Zhang H, et al. Enzyme-sensitive biodegradable and multifunctional polymeric conjugate as theranostic nanomedicine. Appl Mater Today, 2018, 11: 207–218. Google Scholar

[8] Li Y. Realize molecular surgical knife in tumor therapy by nanotechnology. Sci China Mater, 2015, 58: 851-851 CrossRef Google Scholar

[9] Blanco E, Shen H, Ferrari M. Principles of nanoparticle design for overcoming biological barriers to drug delivery. Nat Biotechnol, 2015, 33: 941-951 CrossRef PubMed Google Scholar

[10] Torchilin VP. Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery. Nat Rev Drug Discov, 2014, 13: 813-827 CrossRef PubMed Google Scholar

[11] Zhang X, Xia LY, Chen X, et al. Hydrogel-based phototherapy for fighting cancer and bacterial infection. Sci China Mater, 2017, 60: 487-503 CrossRef Google Scholar

[12] Anselmo AC, Mitragotri S. An overview of clinical and commercial impact of drug delivery systems. J Control Release, 2014, 190: 15-28 CrossRef PubMed Google Scholar

[13] Dai Y, Cai H, Duan Z, et al. Effect of polymer side chains on drug delivery properties for cancer therapy. J Biomed Nanotechnol, 2017, 13: 1369-1385. Google Scholar

[14] Pan D, She W, Guo C, et al. PEGylated dendritic diaminocyclohexyl-platinum (II) conjugates as pH-responsive drug delivery vehicles with enhanced tumor accumulation and antitumor efficacy. Biomaterials, 2014, 35: 10080-10092 CrossRef PubMed Google Scholar

[15] She W, Luo K, Zhang C, et al. The potential of self-assembled, pH-responsive nanoparticles of mPEGylated peptide dendron–doxorubicin conjugates for cancer therapy. Biomaterials, 2013, 34: 1613-1623 CrossRef PubMed Google Scholar

[16] Duncan R. Development of HPMA copolymer–anticancer conjugates: Clinical experience and lessons learnt. Adv Drug Deliver Rev, 2009, 61: 1131-1148 CrossRef PubMed Google Scholar

[17] Zhang R, Luo K, Yang J, et al. Synthesis and evaluation of a backbone biodegradable multiblock HPMA copolymer nanocarrier for the systemic delivery of paclitaxel. J Control Release, 2013, 166: 66-74 CrossRef PubMed Google Scholar

[18] Zhang R, Yang J, Sima M, et al. Sequential combination therapy of ovarian cancer with degradable N-(2-hydroxypropyl)methacrylamide copolymer paclitaxel and gemcitabine conjugates. Proc Natl Acad Sci USA, 2014, 111: 12181-12186 CrossRef PubMed ADS Google Scholar

[19] Luo Q, Xiao X, Dai X, et al. Cross-linked and biodegradable polymeric system as a safe magnetic resonance imaging contrast agent. ACS Appl Mater Interfaces, 2018, 10: 1575-1588 CrossRef Google Scholar

[20] Yang J, Kopeček J. Design of smart HPMA copolymer-based nanomedicines. J Control Release, 2016, 240: 9-23 CrossRef PubMed Google Scholar

[21] Noguchi Y, Wu J, Duncan R, et al. Early phase tumor accumulation of macromolecules: a great difference in clearance rate between tumor and normal tissues. Jpnese J Cancer Res, 1998, 89: 307-314 CrossRef Google Scholar

[22] Duan Z, Zhang Y, Zhu H, et al. Stimuli-sensitive biodegradable and amphiphilic block copolymer-gemcitabine conjugates self-assemble into a nanoscale vehicle for cancer therapy. ACS Appl Mater Interfaces, 2017, 9: 3474-3486 CrossRef Google Scholar

[23] Li X, Sun L, Wei X, et al. Stimuli-responsive biodegradable and gadolinium-based poly[N-(2-hydroxypropyl) methacrylamide] copolymers: their potential as targeting and safe magnetic resonance imaging probes. J Mater Chem B, 2017, 5: 2763-2774 CrossRef Google Scholar

[24] Xu W, Ledin PA, Shevchenko VV, et al. Architecture, assembly, and emerging applications of branched functional polyelectrolytes and poly(ionic liquid)s. ACS Appl Mater Interfaces, 2015, 7: 12570-12596 CrossRef Google Scholar

[25] Venkataraman S, Hedrick JL, Ong ZY, et al. The effects of polymeric nanostructure shape on drug delivery. Adv Drug Deliver Rev, 2011, 63: 1228-1246 CrossRef PubMed Google Scholar

[26] Kalyanaraman B, Joseph J, Kalivendi S, et al. Doxorubicin-induced apoptosis: Implications in cardiotoxicity. Mol Cellular Biochem, 2002, 234/235: 119-124 CrossRef Google Scholar

[27] Chai Z, Hu X, Lu W. Cell membrane-coated nanoparticles for tumor-targeted drug delivery. Sci China Mater, 2017, 60: 504-510 CrossRef Google Scholar

[28] She W, Pan D, Luo K, et al. PEGylated dendrimer-doxorubicin cojugates as pH-sensitive drug delivery systems: synthesis and in vitro characterization. J Biomed nanotechnol, 2015, 11: 964-978 CrossRef Google Scholar

[29] Wei X, Luo Q, Sun L, et al. Enzyme- and pH-sensitive branched polymer–doxorubicin conjugate-based nanoscale drug delivery system for cancer therapy. ACS Appl Mater Interfaces, 2016, 8: 11765-11778 CrossRef Google Scholar

[30] Zhang C, Pan D, Luo K, et al. Dendrimer–doxorubicin conjugate as enzyme-sensitive and polymeric nanoscale drug delivery vehicle for ovarian cancer therapy. Polym Chem, 2014, 5: 5227-5235 CrossRef Google Scholar

[31] Huang X, Du F, Ju R, et al. Novel acid-labile, thermoresponsive poly(methacrylamide)s with pendentortho ester moieties. Macromol Rapid Commun, 2007, 28: 597-603 CrossRef Google Scholar

[32] Song XR, Wang X, Yu SX, et al. Co9Se8 nanoplates as a new theranostic platform for photoacoustic/magnetic resonance dual-modal-imaging-guided chemo-photothermal combination therapy. Adv Mater, 2015, 27: 3285-3291 CrossRef PubMed Google Scholar

[33] Shi K, Li J, Cao Z, et al. A pH-responsive cell-penetrating peptide-modified liposomes with active recognizing of integrin αvβ3 for the treatment of melanoma. J Control Release, 2015, 217: 138-150 CrossRef PubMed Google Scholar

[34] Tang M, Zhou M, Huang Y, et al. Dual-sensitive and biodegradable core-crosslinked HPMA copolymer–doxorubicin conjugate-based nanoparticles for cancer therapy. Polym Chem, 2017, 8: 2370-2380 CrossRef Google Scholar

[35] Hickey JW, Santos JL, Williford JM, et al. Control of polymeric nanoparticle size to improve therapeutic delivery. J Control Release, 2011, 219: 536-547 CrossRef PubMed Google Scholar

[36] He C, Hu Y, Yin L, et al. Effects of particle size and surface charge on cellular uptake and biodistribution of polymeric nanoparticles. Biomaterials, 2010, 31: 3657-3666 CrossRef PubMed Google Scholar

[37] Felber AE, Dufresne MH, Leroux JC. pH-sensitive vesicles, polymeric micelles, and nanospheres prepared with polycarboxylates. Adv Drug Deliver Rev, 2012, 64: 979-992 CrossRef PubMed Google Scholar

[38] Yuan YY, Mao CQ, Du XJ, et al. Surface charge switchable nanoparticles based on zwitterionic polymer for enhanced drug delivery to tumor. Adv Mater, 2012, 24: 5476-5480 CrossRef PubMed Google Scholar

[39] Karimi M, Ghasemi A, Sahandi Zangabad P, et al. Smart micro/nanoparticles in stimulus-responsive drug/gene delivery systems. Chem Soc Rev, 2016, 45: 1457-1501 CrossRef PubMed Google Scholar

[40] Ben-Nun Y, Fichman G, Adler-Abramovich L, et al. Cathepsin nanofiber substrates as potential agents for targeted drug delivery. J Control Release, 2016, 257: 60-67 CrossRef PubMed Google Scholar

[41] Sahay G, Alakhova DY, Kabanov AV. Endocytosis of nanomedicines. J Control Release, 2010, 145: 182-195 CrossRef PubMed Google Scholar

[42] Chen K, Li X, Zhu H, et al. Endocytosis of nanoscale systems for cancer treatments. Curr Med Chem, 2017, 24: 1-1 CrossRef PubMed Google Scholar

[43] Liu J, Bauer H, Callahan J, et al. Endocytic uptake of a large array of HPMA copolymers: Elucidation into the dependence on the physicochemical characteristics. J Control Release, 2010, 143: 71-79 CrossRef PubMed Google Scholar

[44] Li N, Cai H, Jiang L, et al. Enzyme-sensitive and amphiphilic PEGylated dendrimer-paclitaxel prodrug-based nanoparticles for enhanced stability and anticancer efficacy. ACS Appl Mater Interfaces, 2017, 9: 6865-6877 CrossRef Google Scholar

[45] Jin W, Wang Q, Wu M, et al. Lanthanide-integrated supramolecular polymeric nanoassembly with multiple regulation characteristics for multidrug-resistant cancer therapy. Biomaterials, 2017, 129: 83-97 CrossRef PubMed Google Scholar

[46] Zhang Z, Wang J, Nie X, et al. Near infrared laser-induced targeted cancer therapy using thermoresponsive polymer encapsulated gold nanorods. J Am Chem Soc, 2014, 136: 7317-7326 CrossRef PubMed Google Scholar

[47] Malugin A, Kopecková P, Kopecek J. Liberation of doxorubicin from HPMA copolymer conjugate is essential for the induction of cell cycle arrest and nuclear fragmentation in ovarian carcinoma cells. J Control Release, 2007, 124: 6-10 CrossRef PubMed Google Scholar

[48] Etrych T, Kovář L, Strohalm J, et al. Biodegradable star HPMA polymer–drug conjugates: Biodegradability, distribution and anti-tumor efficacy. J Control Release, 2011, 154: 241-248 CrossRef PubMed Google Scholar

[49] Kostková H, Etrych T, Ríhová B, et al. HPMA copolymer conjugates of DOX and mitomycin C for combination therapy: physicochemical characterization, cytotoxic effects, combination index analysis, and anti-tumor efficacy. Macromol Biosci, 2013, 13: 1648-1660 CrossRef PubMed Google Scholar

[50] Chytil P, Koziolová E, Janoušková O, et al. Synthesis and properties of star HPMA copolymer nanocarriers synthesised by RAFT polymerisation designed for selective anticancer drug delivery and imaging. Macromol Biosci, 2015, 15: 839-850 CrossRef PubMed Google Scholar

[51] Su J, Sun H, Meng Q, et al. Long circulation red-blood-cell-mimetic nanoparticles with peptide-enhanced tumor penetration for simultaneously inhibiting growth and lung metastasis of breast cancer. Adv Funct Mater, 2016, 26: 1243-1252 CrossRef Google Scholar

  • Figure 1

    The 1H NMR spectra of the dendritic pdiHPMA-DOX conjugate recorded in D2O.

  • Scheme 1

    Preparation of the dendritic pdiHPMA-DOX conjugate.

  • Figure 2

    Particle size of dendritic conjugate. (a) SEM images. (b) Size distribution by dynamic light scattering (DLS).

  • Figure 3

    (a) SEC profiles of dendritic conjugate and degraded product. (b) Cumulative DOX release profile from the dendritic conjugate at pH 5.0 and pH 7.4 at 37°C. The buffer was mixed with or without cathepsin B. The data shown are mean ± SD (n=3).

  • Figure 4

    Cytotoxicity of the dendritic conjugate (a) and the drug-free dendritic conjugate against 4T1 cells (b) incubation for 48 h at different concentrations. The data shown are mean ± SD (n=5).

  • Figure 5

    In vitro cellular uptake of free DOX (a) and the dendritic conjugate (b) in 4T1 cells after incubation for 0.5, 2, and 4 h under a CLSM. Cell nuclei were stained with Hoechst 33342. Bar = 25 μm.

  • Figure 6

    (a) Confocal images of cellular uptake of the dendritic conjugate by 4T1 cells after 4 h of incubation with the conjugate at 37°C. The acidic organelles were stained with Lysotracker Green, and cell nuclei with Hoechst 33342. Scale bars: 25 μm. (b) Analysis of 4T1 cell apoptosis induced by free DOX and the dendritic conjugate after 48 h incubation by flow cytometry.

  • Figure 7

    Pharmacokinetic profiles of free DOX and the dendritic conjugate after injection in healthy mice at a DOX dose of 5 mg kg−1 body weight. The data represent the mean ± SD (n=5).

  • Figure 8

    Anti-tumor study in the 4T1 breast tumor model (n=7). (a) The dendritic conjugate presented significant tumor suppression (**p<0.01, compared to saline; #p<0.05, compared to free DOX). The black arrows indicate the date of administration via tail vein. (b) On day 27, weights of tumor tissues. (**p<0.01, compared to saline; #p<0.05, compared to free DOX). (c) Tumor growth inhibition on the basis of the tumor weight. (d) Monitoring of body weight of the mice administrated with the dendritic conjugate, free DOX, and saline. (**p<0.01, free DOX in comparison with saline).

  • Figure 9

    H&E staining of major organs harvested from tumor-bearing mice administrated with saline, free DOX and the conjugate (×200).

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