Integrated PhD : Sequential Growth Factor Delivery from Polymeric Scaffolds for Bone Tissue Engineering METU, Dep. Biotechnology and Univ. Minho, Dep. Polymer Engineering, Portugal (through EU FP6 NoE EXPERTISSUES)

Thesis Abstract: Tissue engineering is a promising alternative strategy to produce artificial bone substitutes; however, the control of the cell organization and cell behavior to create fully functional 3-D constructs has not yet been achieved. To overcome these, activities have been concentrated on the development of multi-functional tissue engineering scaffolds capable of delivering the required bioactive agents to initiate and control cellular activities. The aim of this study was to prepare tissue engineered constructs composed of polymeric scaffolds seeded with mesenchymal stem cells (MSCs) carrying a nanoparticulate growth factor delivery system that would sequentially deliver the growth factors in order to mimic the natural bone healing process. To achieve this, BMP-2 and BMP-7, the osteogenic growth factors, were encapsulated in different polymeric nanocapsules (poly(lactic acid-co-glycolic acid) (PLGA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)) with different properties (degradation rates, crystallinity) and, therefore, different release rates to achieve the early release of BMP-2 followed by the release of BMP-7, as it is in nature. Initially, these nanoparticulate delivery systems were characterized and then the effect of single, simultaneous and sequential delivery of BMP-2 and BMP-7 from these delivery systems was studied in vitro using rat bone marrow MSCs. The effect of using these two growth factors in a sequential manner by mimicking their natural bioavailability timing was shown with maximized osteogenic activity results. BMP-2 loaded PLGA nanocapsules were subcutaneously implanted into Wistar rats and according to initial results, their biocompatibility as well as the positive effect of BMP-2 release on the formation of osteoclast-like cells was shown. To complete the construction of the bioactive scaffold, this nanoparticulate sequential delivery system was incorporated into two different types of polymeric systems; natural (chitosan) and synthetic (poly(-caprolactone) (PCL)). 3-D fibrous scaffolds were produced using these materials by wet spinning and 3-D plotting. Incorporation of nanocapsules into 3-D chitosan scaffolds was studied by two different methods: incorporation within and onto chitosan fibers. Incorporation into 3-D PCL scaffolds was achieved by coating the nanocapsules onto the fibers of the scaffolds in an alginate layer. With both scaffold systems, incorporation of nanocapsule populations capable of delivering BMP-2 and BMP-7 in single, simultaneous and sequential fashion was achieved. As with free nanocapsules, the positive effect of sequential delivery on the osteogenic differentiation of MSCs was shown with both scaffold systems, creating multi-functional scaffolds capable of inducing bone healing.

Selected Publications:
Research Articles

• · P.Yilgor, N.Hasirci, V.Hasirci. Sequential BMP-2/BMP-7 Delivery from Polyester Nanocapsules. Journal of Biomedical Materials Research Part A, doi: 10.1002/jbm.a.32520, 2009.

  · P.Yilgor, K.Tuzlakoglu, R.L.Reis, N.Hasirci, V.Hasirci. Incorporation of a Sequential BMP-2/BMP-7 Delivery System into Chitosan-Based Scaffolds for Bone Tissue Engineering. Biomaterials, 30, 3551-3559, 2009.

  · P.Yilgor, R.A.Sousa, R.L.Reis, N.Hasirci, V.Hasirci. 3D Plotted PCL Scaffolds for Stem Cell Based Bone Tissue Engineering. Macromolecular Symposia, 269, 92-99, 2008.

  · P.Yilgor, K.Tuzlakoglu, R.L.Reis, N.Hasirci, V.Hasirci. Nano/Microparticle Incorporated Chitosan Fibers as Tissue Engineering Scaffolds. Tissue Engineering Part A, 14(5), 759-759, Meeting Abstract, 2008.

  · P.Yilgor, C.Orth, S.Ghanaati, N.Hasirci, J.Kirkpatrick, V.Hasirci. PLGA Based BMP-2 Nanocapsules for Bone Tissue Engineering. Tissue Engineering Part A, 14(5), 896-897, Meeting Abstract, 2008.

  · P.Calik, P.Yilgor, A.S.Demir. Influence of controlled-pH and uncontrolled-pH operations on recombinant benzaldehyde lyase production by Escherichia coli. Enzyme and Microbial Technology, 38(5), 617-627, 2006.

  · P.Calik, P.Yilgor, P.Ayhan, A.S.Demir. Oxygen Transfer Effects On Recombinant Benzaldehyde Lyase Production. Chemical Engineering Science, 59, 5075-5083, 2004.

  Review Articles

  · P.Zorlutuna, P.Yilgor, F.B.Basmanav, V.Hasirci. Biomaterials and Tissue Engineering Research in Turkey: The METU BIOMAT Center Experience. Biotechnology Journal, 4, 965-980, 2009.

  · V.Hasirci, E.Vrana, P.Zorlutuna, A.Ndreu, P.Yilgor, B.Basmanav, E.Aydin. Nano biomaterials; A review of the existing science and technology, and new approaches. Journal of Biomaterials Science Polymer Edition, 17(11), 1241-1268, 2006.

  Book Chapters

  · V.Hasirci, P.Yilgor, T.Endogan, G.Eke, N.Hasirci. Polymer Fundamentals: Polymer Synthesis. In Comprehensive Biomaterials. Ed. P.Ducheyne, K.Healy, D.Hutmacher, J.Kirkpatrick, Elsevier Press, submitted.

  · P.Yilgor, D.Yucel, H.Kenar, V.Hasirci. Polyhydroxyalkanoates: a Versatile Class of Biopolymers, and Their Biomedical Potential. In Brazilian Network On Green Chemistry: Awareness, Responsibility And Action. Ed. J.O.B.Carioca, Chapter 20, 415-431, 2008.

  Published Abstracts:

  Oral Presentations

  · P.Yilgor , H.Kenar, V.Hasirci. Kas Dokusu Onarımında Doku Mühendisliği Yaklaşımları ve Kök Hücre Tedavileri, 21. Ulusal Türk Ortopedi ve Travmatoloji Kongresi, İzmir, Turkey, November 3-8, 2009.

  · H.Kenar, D.Yucel, P.Yilgor, N.Hasirci, V.Hasirci. Polyhydroxyalkanoates in tissue engineering, 5th European Symposium on Biopolymers, ESBP 2009, Funchal, Madeira, Portugal, November 18-20, 2009.

  · G.T.Kose , A.B.Ertan, A.C.Calikoglu, P.Yilgor, F.N.Kok, V.Hasirci. Use of nanospheres in cartilage tissue engineering, 15th Biomedical Science and Technology Symposium, Guzelyurt, TRNC, August 16-19, 2009.

  · P.Yilgor , K.Tuzlakoglu, R.L.Reis, N.Hasirci, V.Hasirci. Bone Regeneration on Growth Factor Releasing Fiber Mesh Scaffolds, 2nd National Congress on Artificial Organs and Support Systems, Antalya, Turkey, April 23-26, 2009.

  · V.Hasirci , H.Kenar, D.Yucel, P.Zorlutuna, P.Yilgor, G.Kose, N.Hasirci. Collagen and polyester-based scaffolds for tissue engineering, 237th ACS National Meeting, "Genetically Designed Molecular Materials and Systems" Symposium, Salt Lake City, USA, March 22-26, 2009.

  · F.B.Basmanav, P.Yilgor, G.Kose, N.Hasirci, V.Hasirci. Sequential growth factor delivery from micro and nanoparticles for bone tissue engineering, 60th Indian Pharmaceutical Congress, New Delhi, India, December 12-14, 2008.

  · P.Yilgor , K.Tuzlakoglu, R.L.Reis, N.Hasirci, V.Hasirci. Nano/Microparticle Incorporated Chitosan Fibers as Tissue Engineering Scaffolds, TERMIS-EU Meeting 2008, Porto, Portugal, June 22-26, 2008.

  · P.Yilgor, B.Basmanav, R.L.Reis, N.Hasirci, V.Hasirci. Design of Controlled Release Systems for the Local Delivery of Growth Factors, 35th Controlled Release Society Annual Meeting, New York, USA, July 12-16, 2008.

  · P.Yilgor, B.Basmanav, R.L.Reis, N.Hasirci, V.Hasirci. Controlled Release Systems in Growth Factor Delivery, Trento Innovation Conferences in Materials Engineering, 1st Meeting, Advances in Polymers, Composites and Biomaterials, Trento, Italy, December 16-19, 2007.

  · V.Hasirci , H.Kenar, D.Yucel, P. Zorlutuna, P. Yilgor, B. Basmanav, B. Bayyurt, A. Ndreu, G. Torun Kose, N. Hasirci. Polymeric Nanobiomaterials in Drug Delivery and Tissue Engineering, International Workshop on Nanobiotechnology and Genome Technologies, Antalya, Turkey, October 31- November 3, 2007.

  · C.Orth, P.Yilgor, S.Ghanaati, N.Hasirci, V.Hasirci, J. Kirkpatrick. Characterization of PLGA Based Drug Delivery Systems In Vivo: Analysis of BMP-2 Loaded Nanocapsules, 4th European Symposium on Biopolymers, Kusadasi, Turkey, October 2-4, 2007.

  · P.Yilgor , K.Tuzlakoglu, R.L.Reis, N.Hasirci, V.Hasirci. Incorporation of a Sequential Delivery System into Chitosan-Based Scaffolds for Bone Tissue Engineering, 21st European Conference on Biomaterials, Brighton, UK, September 9-13, 2007.

  · P.Yilgor , P.Ayhan, P.Calik, A.S.Demir. Benzaldehit Liyaz Enzimi Üretimi İçin Biyoproses İşletim Parametrelerinin Araştırılması, 18. Ulusal Kimya Kongresi, Kars, Turkey, July 5-9, 2004.

  · P.Yilgor , P.Ayhan, P.Calik, A.S.Demir. Benzaldehit Liyaz Enzimi Üretimi İçin Oksijen Aktarım stratejisi Geliştirilmesi, 6. Ulusal Kimya Mühendisliği Kongresi, İzmir, Turkey, September 7-10, 2004.

  Poster Presentations

  · S.Kardesler , G.Eke, A.Kucukturhan, P.Yilgor, N.Hasirci, V.Hasirci. Topical Delivery Systems for the Treatment of Skin Diseases, International Symposium on Biotechnology: Developments and Trends, Ankara, Turkey, September 27-30 2009.

  · P.Yilgor, N.Hasirci, V.Hasirci. Sequential BMP-2/BMP-7 Delivery from Polyester Nanocapsules, 15th Biomedical Science and Technology Symposium, Guzelyurt, TRNC, August 16-19, 2009.

  · A.B.Ertan , C.Calikoglu, P.Yilgor, F.N.Kok, G.T.Kose, V.Hasirci. Controlled Release of IGF-I Loaded in Nanospheres Improves in vitro Cartilage Formation, 14. Biyomedikal Mühendisliği Ulusal Toplantısı, Izmir, Turkey, May 20-24, 2009.

  · P.Yilgor, C.Orth, S.Ghanaati, N.Hasirci, J.Kirkpatrick, V.Hasirci. PLGA Based BMP-2 Nanocapsules for Bone Tissue Engineering, TERMIS-EU Meeting 2008, Porto, Portugal, June 22-26, 2008.

  · P.Yilgor, R.A.Sousa, R.L.Reis, N.Hasirci, V.Hasirci. Construction of 3-D Printed PCL Scaffolds with an Inherent Sequential Delivery System, 8th World Biomaterials Congress, Amsterdam, the Netherlands, May 28-June 1, 2008.

  · P.Yilgor , R.A.Sousa, R.L.Reis, N.Hasirci, V.Hasirci. Stem Cell Based Bone Tissue Engineering On 3-D Printed PCL Scaffolds, 4th European Symposium on Biopolymers, Kusadasi, Turkey, October 2-4, 2007.

  · P.Yilgor , R.A.Sousa, R.L.Reis, N.Hasirci, V.Hasirci. Production and Characterization of Rapid Prototyped Tissue Engineering Scaffolds, 13th Biomedical Science and Technology Symposium, Istanbul, Turkey, August 26-28, 2007.

  · B.Ertan , P.Yilgor, N.Hasirci, G.T.Kose, V.Hasirci. Use of pH and Temperature Responsive Intelligent Nanobiomaterials in Cartilage Tissue Engineering, 13th Biomedical Science and Technology Symposium, Istanbul, Turkey, August 26-28, 2007.

  · G.Gurel , P.Yilgor, P.Zorlutuna, V.Hasirci. Bone Tissue Engineering Potential of Poly(å-caprolactone) Films and Foams, 13th Biomedical Science and Technology Symposium, Istanbul, Turkey, August 26-28, 2007.

  · P.Yilgor, N.Hasirci, V.Hasirci. Nanocapsular Sequential Delivery System for Bone Tissue Engineering, 20th European Conference on Biomaterials, Nantes, France, September 27- October 1, 2006.

  · P.Yilgor , N.Hasirci, V.Hasirci. Polymeric Nanocapsules as Growth Factor Carriers for Tissue Engineering Applications, NanoTR-II, Ankara, Turkey, May 3-5, 2006.

  · P.Calik, P.Yilgor, P.Ayhan, A.S.Demir. Oxygen Transfer Effects On Recombinant Benzaldehyde Lyase Production, The 18th International Symposium on Chemical Reaction Engineering, Chicago, USA, June 6-9, 2004.