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BioMed Research International
Volume 2014 (2014), Article ID 761373, 16 pages
http://dx.doi.org/10.1155/2014/761373
Review Article

Biodegradable Polyphosphazene Biomaterials for Tissue Engineering and Delivery of Therapeutics

1Graduate Program of Biomedical Engineering, Faculty of Engineering, The University of Western Ontario, London, ON, Canada N6A 5B9
2Department of Chemical & Biochemical Engineering, Faculty of Engineering, The University of Western Ontario, London, ON, Canada N6A 5B9

Received 1 February 2014; Accepted 29 March 2014; Published 29 April 2014

Academic Editor: Deon Bezuidenhout

Copyright © 2014 Amanda L. Baillargeon and Kibret Mequanint. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Linked References

  1. J. T. Borenstein, E. J. Weinberg, B. K. Orrick, C. Sundback, M. R. Kaazempur-Mofrad, and J. P. Vacanti, “Microfabrication of three-dimensional engineered scaffolds,” Tissue Engineering, vol. 13, no. 8, pp. 1837–1844, 2007. View at Publisher · View at Google Scholar · View at Scopus
  2. J. P. Vacanti, “Tissue engineering and the road to whole organs,” British Journal of Surgery, vol. 99, no. 4, pp. 451–453, 2012. View at Publisher · View at Google Scholar · View at Scopus
  3. C. T. Laurencin, A. M. A. Ambrosio, M. D. Borden, and J. A. Cooper Jr., “Tissue engineering: orthopedic applications,” Annual Review of Biomedical Engineering, vol. 1, pp. 19–46, 1999. View at Google Scholar · View at Scopus
  4. P. X. Ma, “Biomimetic materials for tissue engineering,” Advanced Drug Delivery Reviews, vol. 60, no. 2, pp. 184–198, 2008. View at Publisher · View at Google Scholar · View at Scopus
  5. M. Deng, S. G. Kumbar, Y. Wan, U. S. Toti, H. R. Allcock, and C. T. Laurencin, “Polyphosphazene polymers for tissue engineering: an analysis of material synthesis, characterization and applications,” Soft Matter, vol. 6, no. 14, pp. 3119–3132, 2010. View at Publisher · View at Google Scholar · View at Scopus
  6. R. Langer, “Editorial: tissue engineering: perspectives, challenges, and future directions,” Tissue Engineering, vol. 13, no. 1, pp. 1–2, 2007. View at Publisher · View at Google Scholar · View at Scopus
  7. J. A. Hubbell, “Biomaterials in tissue engineering,” Biotechnology, vol. 13, no. 6, pp. 565–576, 1995. View at Google Scholar · View at Scopus
  8. R. S. Langer and N. A. Peppas, “Present and future applications of biomaterials in controlled drug delivery systems,” Biomaterials, vol. 2, no. 4, pp. 201–214, 1981. View at Publisher · View at Google Scholar · View at Scopus
  9. E. S. Place, N. D. Evans, and M. M. Stevens, “Complexity in biomaterials for tissue engineering,” Nature Materials, vol. 8, no. 6, pp. 457–470, 2009. View at Publisher · View at Google Scholar · View at Scopus
  10. L. S. Nair and C. T. Laurencin, “Biodegradable polymers as biomaterials,” Progress in Polymer Science, vol. 32, no. 8-9, pp. 762–798, 2007. View at Publisher · View at Google Scholar · View at Scopus
  11. S. G. Kumbar, K. S. Soppimath, and T. M. Aminabhavi, “Synthesis and characterization of polyacrylamide-grafted chitosan hydrogel microspheres for the controlled release of indomethacin,” Journal of Applied Polymer Science, vol. 87, no. 9, pp. 1525–1536, 2003. View at Publisher · View at Google Scholar · View at Scopus
  12. K. A. Athanasiou, G. G. Niederauer, and C. M. Agrawal, “Sterilization, toxicity, biocompatibility and clinical applications of polylactic acid/polyglycolic acid copolymers,” Biomaterials, vol. 17, no. 2, pp. 93–102, 1996. View at Publisher · View at Google Scholar · View at Scopus
  13. S. J. De Jong, E. R. Arias, D. T. S. Rijkers, C. F. Van Nostrum, J. J. Kettenes-Van den Bosch, and W. E. Hennink, “New insights into the hydrolytic degradation of poly(lactic acid): participation of the alcohol terminus,” Polymer, vol. 42, no. 7, pp. 2795–2802, 2001. View at Publisher · View at Google Scholar · View at Scopus
  14. M. S. Taylor, A. U. Daniels, K. P. Andriano, and J. Heller, “Six bioabsorbable polymers: In vitro acute toxicity of accumulated degradation products,” Journal of applied biomaterials, vol. 5, no. 2, pp. 151–157, 1994. View at Google Scholar · View at Scopus
  15. C. J. Bettinger, “Synthetic biodegradable elastomers for drug delivery and tissue engineering,” Pure and Applied Chemistry, vol. 83, no. 1, pp. 9–24, 2011. View at Publisher · View at Google Scholar · View at Scopus
  16. D. Puppi, F. Chiellini, A. M. Piras, and E. Chiellini, “Polymeric materials for bone and cartilage repair,” Progress in Polymer Science, vol. 35, no. 4, pp. 403–440, 2010. View at Publisher · View at Google Scholar · View at Scopus
  17. H. R. Allcock, “Recent advances in phosphazene (phosphonitrilic) chemistry,” Chemical Reviews, vol. 72, no. 4, pp. 315–356, 1972. View at Google Scholar · View at Scopus
  18. H. R. Allcock, Chemistry and Applications of Polyphosphazenes, Wiley Interscience, Hoboken, NJ, USA, 2003.
  19. H. R. Allcock, R. L. Kugel, and E. G. Stroh, “Phosphonitrilic compounds. XIII. The structure and properties of poly(difluorophosphazene),” Inorganic Chemistry, vol. 11, no. 5, pp. 1120–1123, 1972. View at Google Scholar · View at Scopus
  20. H. R. Allcock, T. J. Fuller, D. P. Mack, K. Matsumura, and K. M. Smeltz, “Synthesis of poly[(amino acid alkyl ester)phosphazenes],” Macromolecules, vol. 10, no. 4, pp. 824–830, 1977. View at Google Scholar · View at Scopus
  21. A. K. Andrianov, Polyphosphazenes For Biomedical Applications, John Wiley & Sons, Hoboken, NJ, USA, 2009.
  22. J. H. L. Crommen, E. H. Schacht, and E. H. G. Mense, “Biodegradable polymers II. Degradation characteristics of hydrolysis-sensitive poly[(organo)phosphazenes],” Biomaterials, vol. 13, no. 9, pp. 601–611, 1992. View at Publisher · View at Google Scholar · View at Scopus
  23. A. Singh, N. R. Krogman, S. Sethuraman et al., “Effect of side group chemistry on the properties of biodegradable l-alanine cosubstituted polyphosphazenes,” Biomacromolecules, vol. 7, no. 3, pp. 914–918, 2006. View at Publisher · View at Google Scholar · View at Scopus
  24. K. J. L. Burg, S. Porter, and J. F. Kellam, “Biomaterial developments for bone tissue engineering,” Biomaterials, vol. 21, no. 23, pp. 2347–2359, 2000. View at Google Scholar · View at Scopus
  25. R. M. Nerem and D. Seliktar, “Vascular tissue engineering,” Annual Review of Biomedical Engineering, vol. 3, pp. 225–243, 2001. View at Publisher · View at Google Scholar · View at Scopus
  26. H. R. Allcock, “The synthesis of functional polyphosphazenes and their surfaces,” Applied Organometallic Chemistry, vol. 12, no. 10-11, pp. 659–666, 1998. View at Google Scholar · View at Scopus
  27. H. R. Allcock and R. L. Kugel, “Synthesis of high polymeric alkoxy-and aryloxyphosphonitriles,” Journal of the American Chemical Society, vol. 87, no. 18, pp. 4216–4217, 1965. View at Google Scholar · View at Scopus
  28. A. N. Mujumdar, S. G. Young, R. L. Merker, and J. H. Magill, “A study of solution polymerization of polyphosphazenes,” Macromolecules, vol. 23, no. 1, pp. 14–21, 1990. View at Google Scholar · View at Scopus
  29. H. R. Allcock, C. A. Crane, C. T. Morrissey et al., “‘Living’ cationic polymerization of phosphoranimines as an ambient temperature route to polyphosphazenes with controlled molecular weights,” Macromolecules, vol. 29, no. 24, pp. 7740–7747, 1996. View at Google Scholar · View at Scopus
  30. H. R. Allcock, J. M. Nelson, S. D. Reeves, C. H. Honeyman, and I. Manners, “Ambient-temperature direct synthesis of poly(organophosphazenes) via the “living” cationic polymerization of organo-substituted phosphoranimines,” Macromolecules, vol. 30, no. 1, pp. 50–56, 1997. View at Google Scholar · View at Scopus
  31. H. R. Allcock, S. D. Reeves, C. R. De Denus, and C. A. Crane, “Influence of reaction parameters on the living cationic polymerization of phosphoranimines to polyphosphazenes,” Macromolecules, vol. 34, no. 4, pp. 748–754, 2001. View at Publisher · View at Google Scholar · View at Scopus
  32. C. H. Honeyman, I. Manners, C. T. Morrissey, and H. R. Allcock, “Ambient temperature synthesis of poly(dichlorophosphazene) with molecular weight control,” Journal of the American Chemical Society, vol. 117, no. 26, pp. 7035–7036, 1995. View at Google Scholar · View at Scopus
  33. E. S. Peterson, T. A. Luther, M. K. Harrup et al., “On the contributions to the materials science aspects of phosphazene chemistry by Professor Christopher W. Allen: the one-pot synthesis of linear polyphosphazenes,” Journal of Inorganic and Organometallic Polymers and Materials, vol. 17, no. 2, pp. 361–366, 2007. View at Publisher · View at Google Scholar · View at Scopus
  34. S.-K. Kwon, “Synthesis of water-soluble methoxyethoxy-aminoarlyoxy cosubstituted polyphosphazenes as carrier molecules for bioactive agents,” Bulletin of the Korean Chemical Society, vol. 21, no. 10, pp. 969–972, 2000. View at Google Scholar · View at Scopus
  35. L. E. Freed, G. Vunjak-Novakovic, R. J. Biron et al., “Biodegradable polymer scaffolds for tissue engineering,” Biotechnology, vol. 12, no. 7, pp. 689–693, 1994. View at Publisher · View at Google Scholar · View at Scopus
  36. S. Yang, K.-F. Leong, Z. Du, and C.-K. Chua, “The design of scaffolds for use in tissue engineering. Part I. Traditional factors,” Tissue Engineering, vol. 7, no. 6, pp. 679–689, 2001. View at Publisher · View at Google Scholar · View at Scopus
  37. H. R. Allcock, S. R. Pucher, and A. G. Scopelianos, “Poly[(amino acid ester)phosphazenes]: synthesis, crystallinity, and hydrolytic sensitivity in solution and the solid state,” Macromolecules, vol. 27, no. 5, pp. 1071–1075, 1994. View at Google Scholar · View at Scopus
  38. H. R. Allcock, S. R. Pucher, and A. G. Scopelianos, “Poly[(amino acid ester)phosphazenes] as substrates for the controlled release of small molecules,” Biomaterials, vol. 15, no. 8, pp. 563–569, 1994. View at Publisher · View at Google Scholar · View at Scopus
  39. A. K. Andrianov, A. Marin, and P. Peterson, “Water-soluble biodegradable polyphosphazenes containing N-ethylpyrrolidone groups,” Macromolecules, vol. 38, no. 19, pp. 7972–7976, 2005. View at Publisher · View at Google Scholar · View at Scopus
  40. J. Crommen, J. Vandorpe, and E. Schacht, “Degradable polyphosphazenes for biomedical applications,” Journal of Controlled Release, vol. 24, no. 1–3, pp. 167–180, 1993. View at Publisher · View at Google Scholar · View at Scopus
  41. J. H. L. Crommen and E. H. Schacht, “Synthesis and evaluation of the hydrolytical stability of ethyl 2-(α-amino acid)glycolates and ethyl 2-(α-amino acid)lactates,” Bulletin Des Societes Chimiques Belges, vol. 100, no. 10, pp. 747–758, 1991. View at Google Scholar
  42. S. Lakshmi, D. S. Katti, and C. T. Laurencin, “Biodegradable polyphosphazenes for drug delivery applications,” Advanced Drug Delivery Reviews, vol. 55, no. 4, pp. 467–482, 2003. View at Publisher · View at Google Scholar · View at Scopus
  43. C. T. Laurencin, C. D. Morris, H. Pierres-Jacques, E. R. Schwartz, A. R. Keaton, and L. Zou, “The development of bone bioerodible polymer composites for skeletal tissue regeneration: studies of initial cell attachment and spread,” Polymers For Advanced Technologies, no. 3, pp. 369–364, 1992. View at Google Scholar
  44. L. S. Nair, D. A. Lee, J. D. Bender et al., “Synthesis, characterization, and osteocompatibility evaluation of novel alanine-based polyphosphazenes,” Journal of Biomedical Materials Research A, vol. 76, no. 1, pp. 206–213, 2006. View at Publisher · View at Google Scholar · View at Scopus
  45. L. Y. Qiu and K. J. Zhu, “Novel biodegradable polyphosphazenes containing glycine ethyl ester and benzyl ester of amino acethydroxamic acid as cosubstituents: syntheses, characterization, and degradation properties,” Journal of Applied Polymer Science, vol. 77, no. 13, pp. 2987–2995, 2000. View at Google Scholar
  46. E. Schacht, J. Vandorpe, S. Dejardin, Y. Lemmouchi, and L. Seymour, “Biomedical applications of degradable polyphosphazenes,” Biotechnology and Bioengineering, vol. 52, no. 1, pp. 102–108, 1996. View at Google Scholar
  47. S. Sethuraman, L. S. Nair, S. El-Amin et al., “In vivo biodegradability and biocompatibility evaluation of novel alanine ester based polyphosphazenes in a rat model,” Journal of Biomedical Materials Research A, vol. 77, no. 4, pp. 679–687, 2006. View at Publisher · View at Google Scholar · View at Scopus
  48. J. Chlupác, E. Filová, and L. Bacáková, “Blood vessel replacement: 50 years of development and tissue engineering paradigms in vascular surgery,” Physiological research: Academia Scientiarum Bohemoslovaca, vol. 58, pp. S119–S139, 2009. View at Google Scholar · View at Scopus
  49. H. R. Allcock and N. L. Morozowich, “Bioerodible polyphosphazenes and their medical potential,” Polymer Chemistry, vol. 3, no. 3, pp. 578–590, 2012. View at Publisher · View at Google Scholar · View at Scopus
  50. Y. J. Lin, Q. H. Deng, and R. G. Jin, “Effects of processing variables on the morphology and diameter of electrospun poly(amino acid ester)phosphazene nanofibers,” Journal of Wuhan University of Technology-Materials Science, vol. 27, no. 2, pp. 207–211, 2012. View at Publisher · View at Google Scholar
  51. C. Chun, S. M. Lee, C. W. Kim et al., “Doxorubicin-polyphosphazene conjugate hydrogels for locally controlled delivery of cancer therapeutics,” Biomaterials, vol. 30, no. 27, pp. 4752–4762, 2009. View at Publisher · View at Google Scholar · View at Scopus
  52. Y.-J. Lin, Q. Cai, L. Li, Q.-F. Li, X.-P. Yang, and R.-G. Jin, “Co-electrospun composite nanofibers of blends of poly[(amino acid ester)phosphazene] and gelatin,” Polymer International, vol. 59, no. 5, pp. 610–616, 2010. View at Publisher · View at Google Scholar · View at Scopus
  53. J.-K. Cho, J. W. Park, and S.-C. Song, “Injectable and biodegradable poly(organophosphazene) gel containing silibinin: its physicochemical properties and anticancer activity,” Journal of Pharmaceutical Sciences, vol. 101, no. 7, pp. 2382–2391, 2012. View at Publisher · View at Google Scholar · View at Scopus
  54. S. Wilfert, A. Iturmendi, W. Schoefberger et al., “Water-soluble, biocompatible polyphosphazenes with controllable and pH-promoted degradation behavior,” Journal of Polymer Science A: Polymer Chemistry, vol. 52, no. 2, pp. 287–294, 2014. View at Google Scholar
  55. Y. Bi, X. Gong, F. He et al., “Polyphosphazenes containing lactic acid ester and methoxyethoxyethoxy side groups—thermosensitive properties and, in vitro degradation, and biocompatibility,” Canadian Journal of Chemistry, vol. 89, no. 10, pp. 1249–1256, 2011. View at Publisher · View at Google Scholar · View at Scopus
  56. C. T. Laurencin, M. E. Norman, H. M. Elgendy et al., “Use of polyphosphazenes for skeletal tissue regeneration,” Journal of Biomedical Materials Research, vol. 27, no. 7, pp. 963–973, 1993. View at Google Scholar · View at Scopus
  57. M. Gümüşderelioǧlu and A. Gür, “Synthesis, characterization, In vitro degradation and cytotoxicity of poly[bis(ethyl 4-aminobutyro)phosphazene],” Reactive and Functional Polymers, vol. 52, no. 2, pp. 71–80, 2002. View at Publisher · View at Google Scholar · View at Scopus
  58. C. Armstrong and J. F. Staples, “The role of succinate dehydrogenase and oxaloacetate in metabolic suppression during hibernation and arousal,” Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, vol. 180, no. 5, pp. 775–783, 2010. View at Publisher · View at Google Scholar · View at Scopus
  59. P. Carampin, M. T. Conconi, S. Lora et al., “Electrospun polyphosphazene nanofibers for In vitro rat endothelial cells proliferation,” Journal of Biomedical Materials Research A, vol. 80, no. 3, pp. 661–668, 2007. View at Publisher · View at Google Scholar · View at Scopus
  60. F. Langone, S. Lora, F. M. Veronese et al., “Peripheral nerve repair using a poly(organo)phosphazene tubular prosthesis,” Biomaterials, vol. 16, no. 5, pp. 347–353, 1995. View at Publisher · View at Google Scholar · View at Scopus
  61. Y. Fan, M. Kobayashi, and H. Kise, “Synthesis and biodegradation of Poly (ester amide)s containing amino acid residues: the effect of the stereoisomeric composition of L- and D-Phenylalanines on the enzymatic degradation of the polymers,” Journal of Polymer Science A: Polymer Chemistry, vol. 40, no. 3, pp. 385–392, 2002. View at Publisher · View at Google Scholar · View at Scopus
  62. P. X. Ma, ‘Tissue Engineering,’ Encyclopedia of Polymer Science and Technology, John Wiley & Sons, Hoboken, NJ, USA, 2004.
  63. J.-K. Cho, K.-Y. Hong, J. W. Park, H.-K. Yang, and S.-C. Song, “Injectable delivery system of 2-methoxyestradiol for breast cancer therapy using biodegradable thermosensitive poly(organophosphazene) hydrogel,” Journal of Drug Targeting, vol. 19, no. 4, pp. 270–280, 2011. View at Publisher · View at Google Scholar · View at Scopus
  64. G. D. Kang, S. H. Cheon, G. Khang, and S.-C. Song, “Thermosensitive poly(organophosphazene) hydrogels for a controlled drug delivery,” European Journal of Pharmaceutics and Biopharmaceutics, vol. 63, no. 3, pp. 340–346, 2006. View at Publisher · View at Google Scholar · View at Scopus
  65. B. H. Lee and S.-C. Song, “Synthesis and characterization of biodegradable thermosensitive poly(organophosphazene) gels,” Macromolecules, vol. 37, no. 12, pp. 4533–4537, 2004. View at Publisher · View at Google Scholar · View at Scopus
  66. G. H. Altman, R. L. Horan, H. H. Lu et al., “Silk matrix for tissue engineered anterior cruciate ligaments,” Biomaterials, vol. 23, no. 20, pp. 4131–4141, 2002. View at Publisher · View at Google Scholar · View at Scopus
  67. K. S. Katti, “Biomaterials in total joint replacement,” Colloids and Surfaces B: Biointerfaces, vol. 39, no. 3, pp. 133–142, 2004. View at Publisher · View at Google Scholar · View at Scopus
  68. G. Konig, T. N. McAllister, N. Dusserre et al., “Mechanical properties of completely autologous human tissue engineered blood vessels compared to human saphenous vein and mammary artery,” Biomaterials, vol. 30, no. 8, pp. 1542–1550, 2009. View at Publisher · View at Google Scholar · View at Scopus
  69. S. Sarkar, H. J. Salacinski, G. Hamilton, and A. M. Seifalian, “The mechanical properties of infrainguinal vascular bypass grafts: their role in influencing patency,” European Journal of Vascular and Endovascular Surgery, vol. 31, no. 6, pp. 627–636, 2006. View at Publisher · View at Google Scholar · View at Scopus
  70. S. Sethuraman, L. S. Nair, S. El-Amin et al., “Mechanical properties and osteocompatibility of novel biodegradable alanine based polyphosphazenes: side group effects,” Acta Biomaterialia, vol. 6, no. 6, pp. 1931–1937, 2010. View at Publisher · View at Google Scholar · View at Scopus
  71. A. M. A. Ambrosio, J. S. Sahota, C. Runge et al., “Novel polyphosphazene-hydroxyapatite composites as biomaterials,” IEEE Engineering in Medicine and Biology Magazine, vol. 22, no. 5, pp. 18–26, 2003. View at Publisher · View at Google Scholar · View at Scopus
  72. J. L. Brown, L. S. Nair, and C. T. Laurencin, “Solvent/non-solvent sintering: a novel route to create porous microsphere scaffolds for tissue regeneration,” Journal of Biomedical Materials Research B Applied Biomaterials, vol. 86, no. 2, pp. 396–406, 2008. View at Publisher · View at Google Scholar · View at Scopus
  73. C. T. Laurencin, S. F. ElAmin, S. E. Ibim et al., “A highly porous 3-dimensional polyphosphazene polymer matrix for skeletal tissue regeneration,” Journal of Biomedical Materials Research, vol. 30, no. 2, pp. 133–138, 1996. View at Google Scholar
  74. S. P. Nukavarapu, S. G. Kumbar, J. L. Brown et al., “Polyphosphazene/nano-hydroxyapatite composite microsphere scaffolds for bone tissue engineering,” Biomacromolecules, vol. 9, no. 7, pp. 1818–1825, 2008. View at Publisher · View at Google Scholar · View at Scopus
  75. L. S. Nair, S. Bhattacharyya, J. D. Bender et al., “Fabrication and optimization of methylphenoxy substituted polyphosphazene nanofibers for biomedical applications,” Biomacromolecules, vol. 5, no. 6, pp. 2212–2220, 2004. View at Publisher · View at Google Scholar · View at Scopus
  76. N. L. Morozowich, J. L. Nichol, R. J. Mondschein, and H. R. Allcock, “Design and examination of an antioxidant-containing polyphosphazene scaffold for tissue engineering,” Polymer Chemistry, vol. 3, no. 3, pp. 778–786, 2012. View at Publisher · View at Google Scholar · View at Scopus
  77. Y. Li, Y. Shi, S. Duan et al., “Electrospun biodegradable polyorganophosphazene fibrous matrix with poly(dopamine) coating for bone regeneration,” Journal of Biomedical Materials Research A, Early View-Online Version of Record Published Before Inclusion in An Issue, 2013. View at Publisher · View at Google Scholar
  78. N. N. Aldini, M. Fini, M. Rocca et al., “Peripheral nerve reconstruction with bioabsorbable polyphosphazene conduits,” Journal of Bioactive and Compatible Polymers, vol. 12, no. 1, pp. 3–13, 1997. View at Google Scholar · View at Scopus
  79. Q. Zhang, Y. Yan, S. Li, and T. Feng, “The synthesis and characterization of a novel biodegradable and electroactive polyphosphazene for nerve regeneration,” Materials Science and Engineering C, vol. 30, no. 1, pp. 160–166, 2010. View at Publisher · View at Google Scholar · View at Scopus
  80. M. S. Peach, R. James, U. S. Toti et al., “Polyphosphazene functionalized polyester fiber matrices for tendon tissue engineering: In vitro evaluation with human mesenchymal stem cells,” Biomedical Materials, vol. 7, no. 4, pp. 1–13, 2012. View at Google Scholar
  81. J. L. Nichol, N. L. Morozowich, and H. R. Allcock, “Biodegradable alanine and phenylalanine alkyl ester polyphosphazenes as potential ligament and tendon tissue scaffolds,” Polymer Chemistry, vol. 4, no. 3, pp. 600–606, 2013. View at Publisher · View at Google Scholar
  82. J. K. Cho, C. Chun, H. J. Kuh, and S. C. Song, “Injectable poly(organophosphazene)-camptothecin conjugate hydrogels: synthesis, characterization, and antitumor activities,” European Journal of Pharmaceutics and Biopharmaceutics, vol. 81, no. 3, pp. 582–590, 2012. View at Google Scholar
  83. M. Deng, S. G. Kumbar, L. S. Nair, A. L. Weikel, H. R. Allcock, and C. T. Laurencin, “Biomimetic structures: biological implications of dipeptide-substituted polyphosphazene-polyester blend nanofiber matrices for load-bearing bone regeneration,” Advanced Functional Materials, vol. 21, no. 14, pp. 2641–2651, 2011. View at Publisher · View at Google Scholar · View at Scopus
  84. N. R. Krogman, A. Singh, L. S. Nair, C. T. Laurencin, and H. R. Allcock, “Miscibility of bioerodible polyphosphazene/poly(lactide-co-glycolide) blends,” Biomacromolecules, vol. 8, no. 4, pp. 1306–1312, 2007. View at Publisher · View at Google Scholar · View at Scopus
  85. A. L. Weikel, S. G. Owens, N. L. Morozowich et al., “Miscibility of choline-substituted polyphosphazenes with PLGA and osteoblast activity on resulting blends,” Biomaterials, vol. 31, no. 33, pp. 8507–8515, 2010. View at Publisher · View at Google Scholar · View at Scopus