51
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Tessmar JK, Göpferich AM. Matrices and scaffolds for protein delivery in tissue engineering. Adv Drug Deliv Rev 2007; 59:274-91. [PMID: 17544542 DOI: 10.1016/j.addr.2007.03.020] [Citation(s) in RCA: 239] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Accepted: 03/28/2007] [Indexed: 11/19/2022]
Abstract
The tissue engineering of functional tissues depends on the development of suitable scaffolds to support three dimensional cell growth. To improve the properties of the scaffolds, many cell carriers serve dual purposes; in addition to providing cell support, cutting-edge scaffolds biologically interact with adhering and invading cells and effectively guide cellular growth and development by releasing bioactive proteins like growth factors and cytokines. To design controlled release systems for certain applications, it is important to understand the basic principles of protein delivery as well as the stability of each applied biomolecule. To illustrate the enormous progress that has been achieved in the important field of controlled release, some of the recently developed cell carriers with controlled release capacity, including both solid scaffolds and hydrogel-derived scaffolds, are described and possible solutions for unresolved issues are illustrated.
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Affiliation(s)
- Joerg K Tessmar
- Department of Pharmaceutical Technology, University of Regensburg, Regensburg, Germany
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52
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Kretlow JD, Klouda L, Mikos AG. Injectable matrices and scaffolds for drug delivery in tissue engineering. Adv Drug Deliv Rev 2007; 59:263-73. [PMID: 17507111 DOI: 10.1016/j.addr.2007.03.013] [Citation(s) in RCA: 429] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 03/28/2007] [Indexed: 11/22/2022]
Abstract
Injectable matrices and depots have been the subject of much research in the field of drug delivery. The classical tissue engineering paradigm includes a matrix or scaffold to facilitate tissue growth and provide structural support, cells, and the delivery of bioactive molecules. As both tissue engineering and drug delivery techniques benefit from the use of injectable materials due to the minimal invasiveness of an injection, significant crossover should be observed between injectable materials in both fields. This review aims to outline injectable materials and processing techniques used in both tissue engineering and drug delivery and to describe methods by which current injectable materials in the field of drug delivery can be adapted for use as injectable scaffolds for tissue engineering.
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Affiliation(s)
- James D Kretlow
- Department of Bioengineering, Rice University, Houston, TX 77251-1892, USA
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53
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Sokolsky-Papkov M, Agashi K, Olaye A, Shakesheff K, Domb AJ. Polymer carriers for drug delivery in tissue engineering. Adv Drug Deliv Rev 2007; 59:187-206. [PMID: 17540473 DOI: 10.1016/j.addr.2007.04.001] [Citation(s) in RCA: 267] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 04/19/2007] [Indexed: 01/18/2023]
Abstract
Growing demand for tissues and organs for transplantation and the inability to meet this need using by autogeneic (from the host) or allogeneic (from the same species) sources has led to the rapid development of tissue engineering as an alternative. Tissue engineering aims to replace or facilitate the regrowth of damaged or diseased tissue by applying a combination of biomaterials, cells and bioactive molecules. This review focuses on synthetic polymers that have been used for tissue growth scaffold fabrication and their applications in both cell and extracellular matrix support and controlling the release of cell growth and differentiation supporting drugs.
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Affiliation(s)
- Marina Sokolsky-Papkov
- Department of Medicinal Chemistry and Natural Products, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
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54
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Nie H, Soh BW, Fu YC, Wang CH. Three-dimensional fibrous PLGA/HAp composite scaffold for BMP-2 delivery. Biotechnol Bioeng 2007; 99:223-34. [PMID: 17570710 DOI: 10.1002/bit.21517] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A protein loaded three-dimensional scaffold can be used for protein delivery and bone tissue regeneration. The main objective of this project was to develop recombinant human bone morphogenetic protein-2 (rhBMP-2) loaded poly(D,L-lactide-co-glycolide)/hydroxylapatite (PLGA/HAp) composite fibrous scaffolds through a promising fabrication technique, electrospinning. In vitro release of BMP-2 from these scaffolds, and the attachment ability and viability of marrow derived messenchymal stem cells (MSCs) in the presence of the scaffolds were investigated. The PLGA/HAp composite scaffolds developed in this study exhibit good morphology and it was observed that HAp nanoparticles were homogeneously dispersed inside PLGA matrix within the scaffold. The composite scaffolds allowed sustained (2-8 weeks) release of BMP-2 whose release rate was accelerated with increasing HAp content. It was also shown that BMP-2 protein successfully maintained its integrity and natural conformations after undergoing the process of electrospinning. Cell culture experiments showed that the encapsulation of HAp could enhance cell attachment to scaffolds and lower cytotoxicity.
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Affiliation(s)
- Hemin Nie
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore
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55
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Yoo JY, Shin JH, Khang G, Shin HS, Yuk SH, Kim YS, Kim MS, Rhee JM, Lee HB. Effect of glycolide monomer on release behavior of gentamicin sulfate-loaded PLGA microparticles. J Appl Polym Sci 2007. [DOI: 10.1002/app.24804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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56
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Silva GA, Ducheyne P, Reis RL. Materials in particulate form for tissue engineering. 1. Basic concepts. J Tissue Eng Regen Med 2007; 1:4-24. [DOI: 10.1002/term.2] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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57
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Holland TA, Mikos AG. Biodegradable polymeric scaffolds. Improvements in bone tissue engineering through controlled drug delivery. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2006; 102:161-85. [PMID: 17089790 DOI: 10.1007/b137205] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent advances in biology, medicine, and engineering have led to the discovery of new therapeutic agents and novel materials for the repair of large bone defects caused by trauma, congenital defects, or bone tumors. These repair strategies often utilize degradable polymeric scaffolds for the controlled localized delivery of bioactive molecules to stimulate bone ingrowth as the scaffold degrades. Polymer composition, hydrophobicity, crystallinity, and degradability will affect the rate of drug release from these scaffolds, as well as the rate of tissue ingrowth. Accordingly, this chapter examines the wide range of synthetic degradable polymers utilized for osteogenic drug delivery. Additionally, the therapeutic proteins involved in bone formation and in the stimulation of osteoblasts, osteoclasts, and progenitor cells are reviewed to direct attention to the many critical issues influencing effective scaffold design for bone repair.
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Affiliation(s)
- Theresa A Holland
- Department of Bioengineering, Rice University, Houston, TX 77251-1892, USA
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58
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Ho W, Tawil B, Dunn JCY, Wu BM. The behavior of human mesenchymal stem cells in 3D fibrin clots: dependence on fibrinogen concentration and clot structure. ACTA ACUST UNITED AC 2006; 12:1587-95. [PMID: 16846354 DOI: 10.1089/ten.2006.12.1587] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Natural biopolymers such as human fibrin are appealing to tissue engineers, because fibrin is biocompatible, bioresorbable, and essential in normal wound healing. There have been numerous studies to date to develop a fibrin-based injectable cell delivery system, albeit with varying success. We propose that the outcome of fibrin cell delivery can, in part, be attributed to the relative concentrations of fibrinogen and thrombin solutions (i.e., formulations) and the structure of the final 3D fibrin clot. Formulation-dependent proliferation of human mesenchymal stem cells (hMSCs) within 3D fibrin clots was investigated in vitro. Our results indicate that hMSCs are viable in all fibrin sealant formulations investigated, and proliferation rates vary with fibrin formulations. Furthermore, the fibrinogen solution, not thrombin, was found to have a more dominant role on hMSC proliferation, with dilute fibrinogen solutions promoting greater hMSC proliferation. Confocal and electron microscopy reveal formulation dependence on 3D fibrin clot structure, with dilute fibrinogen solutions yielding more open, homogeneous microstructures. This study suggests that the concentrations of fibrinogen and thrombin solutions must be carefully considered for cell delivery because they affect 3D fibrin clot structure and cell proliferation.
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Affiliation(s)
- Wendy Ho
- Department of Bioengineering, UCLA School of Engineering, Los Angeles, CA 90095, USA
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59
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Bae JW, Go DH, Park KD, Lee SJ. Thermosensitive chitosan as an injectable carrier for local drug delivery. Macromol Res 2006. [DOI: 10.1007/bf03219111] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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60
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Ruhé PQ, Hedberg-Dirk EL, Padron NT, Spauwen PHM, Jansen JA, Mikos AG. Porous poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composite for reconstruction of bone defects. ACTA ACUST UNITED AC 2006; 12:789-800. [PMID: 16674292 DOI: 10.1089/ten.2006.12.789] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Calcium phosphate (Ca-P) cements are injectable, self-setting ceramic pastes generally known for their favorable bone response. Ingrowth of bone and subsequent degradation rates can be enhanced by the inclusion of macropores. Initial porosity can be induced by CO(2) foaming during setting of the cement, whereas secondary porosity can develop after hydrolysis of incorporated poly(DL-lactic- co-glycolic acid) (PLGA) microparticles. In this study, we focused on the biological response to porous PLGA/Ca-P cement composites. Pre-set composite discs of four formulations (4 wt% or 15 wt% PLGA microparticles and low or high CO(2) induced porosity) were implanted subcutaneously and in cranial defects in rats for 12 weeks. Histological analysis of the explanted composites revealed that bone and fibrous tissue ingrowth was facilitated by addition of PLGA microparticles (number average diameter of 66 +/- 25 microm). No adverse tissue reaction was observed in any of the composites. Significant increases in composite density due to bone ingrowth in cranial implants were found in all formulations. The results suggest that the PLGA pores are suitable for bone ingrowth and may be sufficient to enable complete tissue ingrowth without initial CO(2) induced porosity. Finally, bone-like mineralization in subcutaneous implants suggests that, under appropriate conditions and architecture, porous PLGA/Ca-P cement composites can exhibit osteoinductive properties. These PLGA/Ca-P composites are a promising scaffolding material for bone regeneration and bone tissue engineering.
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Affiliation(s)
- P Quinten Ruhé
- Department of Peridontology and Biomaterials, Radboud University Nijmegen, Nijmegen, The Netherlands
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61
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Kayaman-Apohan N, Akdemir ZS. Synthesis and characterization of pendant carboxylic acid functional poly(lactic acid) and poly(lactic acid-co-glycolic acid) and their drug release behaviors. POLYM ADVAN TECHNOL 2006. [DOI: 10.1002/pat.656] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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62
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Kempen DHR, Lu L, Kim C, Zhu X, Dhert WJA, Currier BL, Yaszemski MJ. Controlled drug release from a novel injectable biodegradable microsphere/scaffold composite based on poly(propylene fumarate). J Biomed Mater Res A 2006; 77:103-11. [PMID: 16392139 DOI: 10.1002/jbm.a.30336] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The ideal biomaterial for the repair of bone defects is expected to have good mechanical properties, be fabricated easily into a desired shape, support cell attachment, allow controlled release of bioactive factors to induce bone formation, and biodegrade into nontoxic products to permit natural bone formation and remodeling. The synthetic polymer poly(propylene fumarate) (PPF) holds great promise as such a biomaterial. In previous work we developed poly(DL-lactic-co-glycolic acid) (PLGA) and PPF microspheres for the controlled delivery of bioactive molecules. This study presents an approach to incorporate these microspheres into an injectable, porous PPF scaffold. Model drug Texas red dextran (TRD) was encapsulated into biodegradable PLGA and PPF microspheres at 2 microg/mg microsphere. Five porous composite formulations were fabricated via a gas foaming technique by combining the injectable PPF paste with the PLGA or PPF microspheres at 100 or 250 mg microsphere per composite formulation, or a control aqueous TRD solution (200 microg per composite). All scaffolds had an interconnected pore network with an average porosity of 64.8 +/- 3.6%. The presence of microspheres in the composite scaffolds was confirmed by scanning electron microscopy and confocal microscopy. The composite scaffolds exhibited a sustained release of the model drug for at least 28 days and had minimal burst release during the initial phase of release, as compared to drug release from microspheres alone. The compressive moduli of the scaffolds were between 2.4 and 26.2 MPa after fabrication, and between 14.9 and 62.8 MPa after 28 days in PBS. The scaffolds containing PPF microspheres exhibited a significantly higher initial compressive modulus than those containing PLGA microspheres. Increasing the amount of microspheres in the composites was found to significantly decrease the initial compressive modulus. The novel injectable PPF-based microsphere/scaffold composites developed in this study are promising to serve as vehicles for controlled drug delivery for bone tissue engineering.
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Affiliation(s)
- Diederik H R Kempen
- Tissue Engineering and Polymeric Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, Minnesota 55905, USA
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63
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Weyand B, von Schroeder HP. Bone challenges for the hand surgeon: from basic bone biology to future clinical applications. Clin Plast Surg 2005; 32:537-47, vii. [PMID: 16139627 DOI: 10.1016/j.cps.2005.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Bone is a complex tissue composed of a calcified extracellular matrix with specialized cells that produce, maintain, and resorb the bone. Bone also has a rich vascular and neural supply. Bone has a great capability of regeneration, healing, and remodelling that is influenced by external factors, such as stress forces, and internal regulators that include hormones, vitamins, and growth factors. These factors dictate bone biology, and variations result in pathophysiologic conditions that have clinical implications in hand surgery. Solutions to the challenges in hand surgery rely on a thorough understanding of the biology of bone.
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Affiliation(s)
- Birgit Weyand
- University of Toronto Hand Program and Bone Laboratory, Faculty of Dentistry, University Health Network and University of Toronto, Hand Clinic 2-East, Toronto M5T 2S8, Ontario, Canada
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64
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B Malafaya PP, Pedro AJ, Peterbauer A, Gabriel C, Redl H, Reis RL. Chitosan particles agglomerated scaffolds for cartilage and osteochondral tissue engineering approaches with adipose tissue derived stem cells. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2005; 16:1077-85. [PMID: 16362204 DOI: 10.1007/s10856-005-4709-4] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2005] [Accepted: 07/20/2005] [Indexed: 05/05/2023]
Abstract
It is well accepted that natural tissue regeneration is unlikely to occur if the cells are not supplied with an extracellular matrix (ECM) substitute. With this goal, several different methodologies have been used to produce a variety of 3D scaffolds as artificial ECM substitutes suitable for bone and cartilage tissue engineering. Furthermore, osteochondral tissue engineering presents new challenges since the combination of scaffolding and co-culture requirements from both bone and cartilage applications is required in order to achieve a successful osteochondral construct. In this paper, an innovative processing route based on a chitosan particles aggregation methodology for the production of cartilage and osteochondral tissue engineering scaffolds is reported. An extensive characterization is presented including a morphological evaluation using Micro-Computed Tomography (microCT) and 3D virtual models built with an image processing software. Mechanical and water uptake characterizations were also carried out, evidencing the potential of the developed scaffolds for the proposed applications. Cytotoxicity tests show that the developed chitosan particles agglomerated scaffolds do not exert toxic effects on cells. Furthermore, osteochondral bilayered scaffolds could also be developed. Preliminary seeding of mesenchymal stem cells isolated from human adipose tissue was performed aiming at developing solutions for chondrogenic and osteogenic differentiation for osteochondral tissue engineering applications.
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Affiliation(s)
- P P B Malafaya
- 3B's Research Group-Biomaterials, Biomimetics and Biodegradables, Dept. Polymer Eng., Univ. of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.
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65
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Salvay DM, Shea LD. Inductive tissue engineering with protein and DNA-releasing scaffolds. MOLECULAR BIOSYSTEMS 2005; 2:36-48. [PMID: 16880921 PMCID: PMC2657198 DOI: 10.1039/b514174p] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cellular differentiation, organization, proliferation and apoptosis are determined by a combination of an intrinsic genetic program, matrix/substrate interactions, and extracellular cues received from the local microenvironment. These molecular cues come in the form of soluble (e.g. cytokines) and insoluble (e.g. ECM proteins) factors, as well as signals from surrounding cells that can promote specific cellular processes leading to tissue formation or regeneration. Recent developments in the field of tissue engineering have employed biomaterials to present these cues, providing powerful tools to investigate the cellular processes involved in tissue development, or to devise therapeutic strategies based on cell replacement or tissue regeneration. These inductive scaffolds utilize natural and/or synthetic biomaterials fabricated into three-dimensional structures. This review summarizes the use of scaffolds in the dual role of structural support for cell growth and vehicle for controlled release of tissue inductive factors, or DNA encoding for these factors. The confluence of molecular and cell biology, materials science and engineering provides the tools to create controllable microenvironments that mimic natural developmental processes and direct tissue formation for experimental and therapeutic applications.
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Affiliation(s)
- David M. Salvay
- Department of Chemical and Biological Engineering, 2145 Sheridan Rd E156 Evanston, IL 60208-3120. E-mail: ; Fax: 847-491-3728; Tel: 847-491-7043
| | - Lonnie D. Shea
- Department of Chemical and Biological Engineering, 2145 Sheridan Rd E156 Evanston, IL 60208-3120. E-mail: ; Fax: 847-491-3728; Tel: 847-491-7043
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd E156 Evanston, IL 60208-3120
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66
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Hedberg EL, Kroese-Deutman HC, Shih CK, Lemoine JJ, Liebschner MAK, Miller MJ, Yasko AW, Crowther RS, Carney DH, Mikos AG, Jansen JA. Methods: A Comparative Analysis of Radiography, Microcomputed Tomography, and Histology for Bone Tissue Engineering. ACTA ACUST UNITED AC 2005; 11:1356-67. [PMID: 16259591 DOI: 10.1089/ten.2005.11.1356] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study focused on the assessment of radiography, microcomputed tomography, and histology for the evaluation of bone formation in a 15.0-mm defect in the rabbit radius after the implantation of a tissue-engineered construct. Radiography was found to be useful as a noninvasive method for obtaining images of calcified tissue throughout the time course of the experiment. With this method, however, image quality was low, making it difficult to obtain precise information about the location and quantity of the bone formed. Microcomputed tomography was used to create three-dimensional reconstructions of the bone (25-microm resolution). These reconstructions allowed for greater spatial resolution than the radiography, but did not allow for imaging of the implanted scaffold material or the surrounding, nonmineralized tissue. To visualize all materials within the defect area at the cellular level, histology was used. Histological analysis, however, is a destructive technique that did not allow for any further analysis of the samples. Each technique examined here has its own advantages and limitations, but each yields unique information regarding bone regeneration. It is only through the use of all three techniques that complete characterization of the bone growth and tissue/construct responses after implantation in vivo.
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67
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Hedberg EL, Shih CK, Lemoine JJ, Timmer MD, Liebschner MAK, Jansen JA, Mikos AG. In vitro degradation of porous poly(propylene fumarate)/poly(dl-lactic-co-glycolic acid) composite scaffolds. Biomaterials 2005; 26:3215-25. [PMID: 15603816 DOI: 10.1016/j.biomaterials.2004.09.012] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Accepted: 09/09/2004] [Indexed: 10/26/2022]
Abstract
This study investigated the in vitro degradation of porous poly(propylene fumarate) (PPF-based) composites incorporating microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) during a 26-week period in pH 7.4 phosphate-buffered saline at 37 degrees C. Using a fractional factorial design, four formulations of composite scaffolds were fabricated with varying PEG content of the microparticles, microparticle mass fraction of the composite material, and initial leachable porogen content of the scaffold formulations. PPF scaffolds without microparticles were fabricated with varying leachable porogen content for use as controls. The effects of including PLGA/PEG microparticles in PPF scaffolds and the influence of alterations in the composite formulation on scaffold mass, geometry, water absorption, mechanical properties and porosity were examined for cylindrical specimens with lengths of 13 mm and diameters of 6.5 mm. The composite scaffold composition affected the extent of loss of polymer mass, scaffold length, and diameter, with the greatest loss of polymer mass equal to 15+/-5% over 26 weeks. No formulation, however, exhibited any variation in compressive modulus or peak compressive strength over time. Additionally, sample porosity, as determined by both mercury porosimetry and micro-computed tomography did not change during the period of this study. These results demonstrate that microparticle carriers can be incorporated into PPF scaffolds for localized delivery of bioactive molecules without altering scaffold mechanical or structural properties up to 26 weeks in vitro.
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Affiliation(s)
- Elizabeth L Hedberg
- Department of Bioengineering, Rice University, P.O. Box 1892-MS 142, Houston, TX 77251-1892, USA
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68
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Hedberg EL, Kroese-Deutman HC, Shih CK, Crowther RS, Carney DH, Mikos AG, Jansen JA. Effect of varied release kinetics of the osteogenic thrombin peptide TP508 from biodegradable, polymeric scaffolds on bone formationin vivo. J Biomed Mater Res A 2005; 72:343-53. [PMID: 15666357 DOI: 10.1002/jbm.a.30265] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study was designed to assess the influence of varied release kinetics of the osteogenic thrombin peptide TP508 from osteoconductive poly(propylene fumarate)-based (PPF) composite scaffolds on bone formation in vivo. Four classes of scaffolds were constructed with different TP508 dosages (200, 100, or 0 microg) and release kinetics (large burst release, minimal burst release, or no release) and implanted in 15.0 mm segmental defects in rabbit radii. The animals were euthanized at 12 weeks and the implants were analyzed by light microscopy, histological scoring analysis, and histomorphometric analysis. Samples from all classes displayed bone growth within the pores of the scaffold near the edges of the defect. In areas where bone was not observed, the pores were filled with mostly fibrous tissue and exhibited minimal inflammatory response for all classes. In contrast to other scaffold classes, scaffolds containing a total dose of 200 microg TP508 and exhibiting a large burst release profile showed statistically more bone formation guided along the surface of the scaffold, with these scaffolds averaging 80% of the defect length bridged with bone compared to 10% or less bridged for the other scaffold classes. These results demonstrate that the extent of in vivo bone formation in response to controlled release from PPF-composite scaffolds is determined by the release kinetics of the incorporated osteogenic peptide.
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Affiliation(s)
- Elizabeth L Hedberg
- Department of Bioengineering, Rice University, P.O. Box 1892-MS 142, Houston, Texas 77251-1892, USA
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69
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Kempen DHR, Lu L, Zhu X, Kim C, Jabbari E, Dhert WJA, Currier BL, Yaszemski MJ. Development of biodegradable poly(propylene fumarate)/poly(lactic-co-glycolic acid) blend microspheres. I. Preparation and characterization. J Biomed Mater Res A 2005; 70:283-92. [PMID: 15227673 DOI: 10.1002/jbm.a.30079] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We developed poly(propylene fumarate)/poly(lactic-co-glycolic acid) (PPF/PLGA) blend microspheres and investigated the effects of various processing parameters on the characteristics of these microspheres. The advantage of these blend microspheres is that the carbon-carbon double bonds along the PPF backbone could be used for their immobilization in a PPF scaffold. Microspheres containing the model drug Texas red dextran were fabricated using a double emulsion-solvent extraction technique. The effects of the following six processing parameters on the microsphere characteristics were investigated: PPF/PLGA ratio, polymer viscosity, vortex speed during emulsification, amount of internal aqueous phase, use of poly(vinyl alcohol) (PVA) in the internal aqueous phase, and PVA concentration in the external aqueous phase. Our results showed that the microsphere surface morphology was affected most by the viscosity of the polymer solution. Microspheres fabricated with a kinematic viscosity of 39 centistokes had a smooth, nonporous surface. In most microsphere formulations, the model drug was dispersed uniformly in the polymer matrix. For all fabricated formulations, the average microsphere diameter ranged between 19.0 and 76.9 microm. The external PVA concentration and vortex speed had most effect on the size distribution. Entrapment efficiencies varied from 60 to 98% and were most affected by the amount of internal aqueous phase, vortex speed, and polymer viscosity. Overall, we demonstrated the ability to fabricate PPF/PLGA blend microspheres with similar surface morphology, entrapment efficiency, and size distribution as conventional PLGA microspheres.
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Affiliation(s)
- Diederik H R Kempen
- Tissue Engineering & Polymeric Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
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70
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Hedberg EL, Kroese-Deutman HC, Shih CK, Crowther RS, Carney DH, Mikos AG, Jansen JA. In vivo degradation of porous poly(propylene fumarate)/poly(DL-lactic-co-glycolic acid) composite scaffolds. Biomaterials 2005; 26:4616-23. [PMID: 15722131 DOI: 10.1016/j.biomaterials.2004.11.039] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Accepted: 11/30/2004] [Indexed: 11/22/2022]
Abstract
This study investigated the in vivo degradation of poly(propylene fumarate) (PPF)/poly(DL-lactic-co-glycolic acid) (PLGA) composite scaffolds designed for controlled release of osteogenic factors. PPF/PLGA composites were implanted into 15.0mm segmental defects in the rabbit radius, harvested after 12 and 18 weeks, and analyzed using histological techniques to assess the extent of polymer degradation as well as the tissue response within the pores of the scaffolds. Polymer degradation was limited to micro-fragmentation of the scaffold at the ends and edges of the implant at both 12 and 18 weeks. The tissue within the pores of the scaffold consisted of fibrous tissue, blood vessels and some inflammatory cells. In areas where polymer breakdown was evident, an increased inflammatory response was observed. In contrast, areas of bone ingrowth into the polymer scaffold were characterized by minimal inflammatory response and polymer degradation. Our results show that minimal degradation of porous PPF occurs within 18 weeks of implantation in a rabbit model. Further, the in vivo degradation data of porous PPF/PLGA scaffolds are comparable with earlier obtained in vitro data.
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Affiliation(s)
- Elizabeth L Hedberg
- Department of Bioengineering, Rice University, P.O. Box 1892-MS 142, Houston, TX 77251-1892, USA
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Lee JE, Kim SE, Kwon IC, Ahn HJ, Cho H, Lee SH, Kim HJ, Seong SC, Lee MC. Effects of a chitosan scaffold containing TGF-beta1 encapsulated chitosan microspheres on in vitro chondrocyte culture. Artif Organs 2004; 28:829-39. [PMID: 15320946 DOI: 10.1111/j.1525-1594.2004.00020.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The objectives of this study were (1) to develop a three-dimensional chitosan scaffold in combination with transforming growth factor-beta1 (TGF-beta1)-loaded chitosan microspheres and (2) to evaluate the effect of the TGF-beta1 release on the chondrogenic potential of rabbit chondrocytes in the scaffolds. TGF-beta1 was loaded into chitosan microspheres using an emulsion-crosslinking method, resulting in spherical shapes with a size ranging from 0.3 to 1.5 microm. Controlled release of TGF-beta1, as measured by enzyme-linked immunosorbent assay (ELISA), was observed with chitosan microspheres over 7 days. Chitosan solutions (2% and 3%) were fabricated into two types of scaffolds with different pore morphologies and mechanical properties using a freeze-drying technique, with the result that scaffold with higher concentrations showed smaller pores and lower porosity, leading to a much stronger scaffold. The TGF-beta1 microspheres were incorporated into the scaffolds at a concentration of 10 ng TGF-beta1/scaffold and then chondrocytes seeded into each scaffold and incubated in vitro for 2 weeks. The 2% chitosan scaffolds showed higher cell attachment levels than the 3% chitosan scaffolds (P < 0.01), regardless of the TGF-beta1 microspheres. Both the proliferation rate and glycosaminoglycan (GAG) production were significantly higher for scaffolds incorporating TGF-beta1 microspheres than for the control scaffolds without microspheres 10 days after incubation. Extracellular matrix staining by Safranin O and immunohistochemistry for type II collagen both significantly increased in scaffolds containing TGF-beta1 microspheres. These results suggest that the TGF-beta1 microsphere incorporated in scaffolds have the potential to enhance cartilage formation.
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Affiliation(s)
- Jong Eun Lee
- Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea
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72
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Hedberg EL, Shih CK, Solchaga LA, Caplan AI, Mikos AG. Controlled release of hyaluronan oligomers from biodegradable polymeric microparticle carriers. J Control Release 2004; 100:257-66. [PMID: 15544873 DOI: 10.1016/j.jconrel.2004.08.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2004] [Accepted: 08/27/2004] [Indexed: 10/26/2022]
Abstract
In the present study, biodegradable microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) were explored as a potential carrier for the controlled release of polysaccharide oligomers. To this end, hyaluronan (HY) oligomers of varying molecular weights were incorporated into PLGA/PEG microparticles. Using a two-level fractional factorial experimental design, four microparticle formulation parameters, the amount of PEG included in the microparticles, the initial HY loading of the microparticles, the molecular weight of HY, and the molecular weight of PLGA, were studied for their influence on the incorporation and in vitro release of HY over the period of 28 days. The entrapment efficiencies were found to range between 10+/-1% and 24+/-2% depending on the initial loading and the molecular weight of the HY oligomer used in the fabrication of the microparticles. The HY was released in a multiphasic fashion including an initial burst release, followed by two separate periods of linear release. The normalized cumulative mass released during the burst release ranged from 25.1+/-9.2% to 93.0+/-0.7% and was found to be significantly influenced by the initial HY loading, the HY molecular weight, and the PLGA molecular weight. The initial period of linear release lasted from day 1 to day 14 and displayed normalized cumulative rates of release from 0.1+/-0.0%/day to 1.4+/-0.2%/day. During this period, PEG content of the microparticles and HY molecular weight exerted the greatest influence on the rate of release. Finally, the second period of linear release lasted through the final time-point at day 28. Here, the normalized cumulative rate of release values ranged from 0.2+/-0.1%/day to 3.6+/-0.7%/day and were dependent on all formulation parameters studied. These results demonstrate the potential of PLGA/PEG blend microparticles for the controlled release of HY oligomers.
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Affiliation(s)
- Elizabeth L Hedberg
- Department of Bioengineering, Rice University, P.O. Box 1892, MS-142, Houston, TX 77251-1892, USA
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73
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Sheller MR, Crowther RS, Kinney JH, Yang J, Di Jorio S, Breunig T, Carney DH, Ryaby JT. Repair of rabbit segmental defects with the thrombin peptide, TP508. J Orthop Res 2004; 22:1094-9. [PMID: 15304284 DOI: 10.1016/j.orthres.2004.03.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The synthetic peptide, TP508 (Chrysalin), was delivered to rabbit segmental bone defects in biodegradable controlled-release PLGA microspheres to determine its potential efficacy for enhancing healing of non-critically and critically sized segmental defects. Non-critically sized radial defects were created in the forelimbs of New Zealand White rabbits, which were randomized into three treatment groups receiving 10, 50 and 100 microg doses of TP508 in the right radius and control microspheres (without TP508) in the left radius. Torsional testing of the radii at six weeks showed a significant increase in ultimate torque, failure torque, ultimate energy, failure energy, and stiffness when treated with TP508 compared to controls (p<0.01 for all measures). Thus, TP508 appeared to enhance or accelerate bone growth in these defects. In a second set of experiments, critically sized ulnar defects were created in the forelimbs of New Zealand White rabbits, which were randomized into two groups with each rabbit receiving microspheres with 100 or 200 microg of TP508 into the right ulnar defect and control microspheres (without TP508) alone into the left ulnar defect. Bone healing was evaluated with plain radiographs, synchrotron-based microtomography, and mechanical testing. Radiographs of the rabbit limbs scored by three blinded, independent reviewers demonstrated a significantly higher degree of healing when treated with TP508 than their untreated control limbs (p<0.05). Three-dimensional synchrotron tomography of a limited number of samples showed that the new bone in TP508-treated samples had a less porous surface appearance and open marrow spaces, suggesting progression of bone remodeling. Torsional testing of the ulnae at nine weeks showed a significant increase in maximum torque and failure energy when treated with TP508 compared to controls (p<0.01 for both measures). These results suggest that TP508 in a controlled release delivery vehicle has the potential to enhance healing of segmental defects in both critically and non-critically sized defects.
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74
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Packhaeuser CB, Schnieders J, Oster CG, Kissel T. In situ forming parenteral drug delivery systems: an overview. Eur J Pharm Biopharm 2004; 58:445-55. [PMID: 15296966 DOI: 10.1016/j.ejpb.2004.03.003] [Citation(s) in RCA: 279] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 01/26/2004] [Indexed: 11/18/2022]
Abstract
Biodegradable injectable in situ forming drug delivery systems represent an attractive alternative to microspheres and implants as parenteral depot systems. Their importance will grow as numerous proteins will lose their patent protection in the near future. These devices may offer attractive opportunities for protein delivery and could possibly extend the patent life of protein drugs. The controlled release of bioactive macromolecules via (semi-) solid in situ forming systems has a number of advantages, such as ease of administration, less complicated fabrication, and less stressful manufacturing conditions for sensitive drug molecules. For these reasons, a number of polymeric drug delivery systems with the ability to form a drug reservoir at the injection site are under investigation. Here, we review various strategies used for the preparation of in situ forming parenteral drug depots and their potential benefits/draw-backs, especially with regard to the delivery of protein drug candidates.
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Affiliation(s)
- C B Packhaeuser
- Department of Pharmaceutics and Biopharmacy, Philipps-University, Marburg, Germany
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75
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Yoo JY, Kim JM, Khang G, Kim MS, Cho SH, Lee HB, Kim YS. Effect of lactide/glycolide monomers on release behaviors of gentamicin sulfate-loaded PLGA discs. Int J Pharm 2004; 276:1-9. [PMID: 15113609 DOI: 10.1016/j.ijpharm.2004.01.043] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2003] [Revised: 01/13/2004] [Accepted: 01/25/2004] [Indexed: 11/29/2022]
Abstract
In order to develop the desirable drug release patterns such as no lag time and exact zero-order release rate, gentamicin sulfate (GS)-loaded poly(D,L-lactide-co-glycolide) (PLGA) discs containing lactide monomer (LM) or glycolide monomer (GM) were prepared. LM or GM was applied for the controlling drug release pattern due to its non-toxic and biodegradable nature. Water absorption, mass loss, pH change, and morphology of discs were examined to study the effect of LM or GM addition. GS release showed near zero-order profile in the GS-loaded polymeric discs prepared in the presence of LM or GM (10%). The channel of GS-loaded PLGA containing LM or GM was formed by the dissolution of LM or GM. Water uptake of disc increased till 21 days from the beginning of the test. The pH variations of media declined in the same manner with the result of mass loss. The antibiosis of GS was also confirmed by bacterial inhibition zone test using the prepared polymeric discs. From these results, we expected that the polymeric discs containing LM or GM would be a good dosage form as a topically implantable device which can get rid of lag period from PLGA matrix.
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Affiliation(s)
- Je Young Yoo
- Department of Advanced Organic Materials Engineering, Chonbuk National University, 664-14 Dukjin, Jeonju 561-756, Republic of Korea
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76
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Maeda H, Sano A, Fujioka K. Controlled release of rhBMP-2 from collagen minipellet and the relationship between release profile and ectopic bone formation. Int J Pharm 2004; 275:109-22. [PMID: 15081142 DOI: 10.1016/j.ijpharm.2004.01.040] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2003] [Revised: 01/15/2004] [Accepted: 01/20/2004] [Indexed: 11/17/2022]
Abstract
The purpose of this study was to examine the effects of various additives on the profiles of rhBMP-2 release from minipellet, which is a sustained release formulation for protein drugs using collagen as a carrier, and to examine the influence of varying release profiles on ectopic bone formation. When the amount of rhBMP-2 remaining in the preparation after subcutaneous implantation to mice was examined, it was found that the addition of sucrose, glucose, PEG4000, alanine (Ala) or acacia in a concentration of 20% (w/w) to the minipellet with 5% (w/w) of rhBMP-2 did not accelerate the drug release in a noticeable manner, while the addition of sodium chondroitin sulfate, glutamic acid (Glu) or citric acid accelerated the release of rhBMP-2 markedly. When two types of minipellets (a fast release type added with 20% Glu and 20% Ala and a slow release type without additives) containing varying amounts of rhBMP-2 were implanted subcutaneously to mice, the soft X-ray observation, histological examination and measurement of calcium formation 3 weeks after implantation revealed extensive ectopic bone formation in mice implanted with the fast release type preparation. Ectopic bone formation was dose-dependent. The result of this study exhibited that the effects of controlled release formulation of rhBMP-2 on bone formation vary depending on their release profiles, and suggested that combination of initial burst and sustained release was effective for bone formation. It was also shown that minipellet is useful as a controlled release formulation which can release rhBMP-2 to areas around the implanted site with various release profiles.
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Affiliation(s)
- Hiroo Maeda
- Formulation Research Laboratories, Sumitomo Pharmaceuticals Co. Ltd., 3-45 Kurakakiuchi 1-Chome, Ibaraki-shi, Osaka 567-0878, Japan.
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77
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Kempen DHR, Lu L, Zhu X, Kim C, Jabbari E, Dhert WJA, Currier BL, Yaszemski MJ. Development of biodegradable poly(propylene fumarate)/poly(lactic-co-glycolic acid) blend microspheres. II. Controlled drug release and microsphere degradation. ACTA ACUST UNITED AC 2004; 70:293-302. [PMID: 15227674 DOI: 10.1002/jbm.a.30080] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This article describes the effects of six processing parameters on the release kinetics of a model drug Texas red dextran (TRD) from poly(propylene fumarate)/poly(lactic-co-glycolic acid) (PPF/PLGA) blend microspheres as well as the degradation of these microspheres. The microspheres were fabricated using a double emulsion-solvent extraction technique in which the following six parameters were varied: PPF/PLGA ratio, polymer viscosity, vortex speed during emulsification, amount of internal aqueous phase, use of poly(vinyl alcohol) in the internal aqueous phase, and poly(vinyl alcohol) concentration in the external aqueous phase. We have previously characterized these microspheres in terms of microsphere morphology, size distribution, and TRD entrapment efficiency. In this work, the TRD release profiles in phosphate-buffered saline were determined and all formulations showed an initial burst release in the first 2 days followed by a decreased sustained release over a 38-day period. The initial burst release varied from 5.1 (+/-1.1) to 67.7 (+/-3.4)% of the entrapped TRD, and was affected most by the viscosity of the polymer solution used for microsphere fabrication. The sustained release between day 2 and day 38 ranged from 7.9 (+/-0.8) to 27.2 (+/-3.1)% of the entrapped TRD. During 11 weeks of in vitro degradation, the mass of the microspheres remained relatively constant for the first 3 weeks after which it decreased dramatically, whereas the molecular weight of the polymers decreased immediately upon placement in phosphate-buffered saline. Increasing the PPF content in the PPF/PLGA blend resulted in slower microsphere degradation. Overall, this study provides further understanding of the effects of various processing parameters on the release kinetics from PPF/PLGA blend microspheres thus allowing modulation of drug release to achieve a wide spectrum of release profiles.
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Affiliation(s)
- Diederik H R Kempen
- Tissue Engineering & Polymeric Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905
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78
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Ruhe PQ, Hedberg EL, Padron NT, Spauwen PHM, Jansen JA, Mikos AG. rhBMP-2 release from injectable poly(DL-lactic-co-glycolic acid)/calcium-phosphate cement composites. J Bone Joint Surg Am 2003; 85-A Suppl 3:75-81. [PMID: 12925613 DOI: 10.2106/00004623-200300003-00013] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND In bone tissue engineering, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles are frequently used as a delivery vehicle for bioactive molecules. Calcium phosphate cement is an injectable, osteoconductive, and degradable bone cement that sets in situ. The objective of this study was to create an injectable composite based on calcium phosphate cement embedded with PLGA microparticles for sustained delivery of recombinant human bone morphogenetic protein-2 (rhBMP-2). METHODS (125) I-labeled rhBMP-2 was incorporated in PLGA microparticles. PLGA microparticle/calcium-phosphate cement composites were prepared in a ratio of 30:70 by weight. Material properties were evaluated by scanning electron microscopy, microcomputed tomography, and mechanical testing. Release kinetics of rhBMP-2 from PLGA/calcium-phosphate cement disks and PLGA microparticles alone were determined in vitro in two buffer solutions (pH 7.4 and pH 4.0) for up to twenty-eight days. RESULTS The entrapment yield of rhBMP-2 in PLGA microparticles was a mean (and standard deviation) of 79% +/- 8%. Analysis showed spherical PLGA microparticles (average size, 17.2 +/-1.3 micro m) distributed homogeneously throughout the nanoporous disks. The average compressive strength was significantly lower (p < 0.001) for PLGA and calcium-phosphate cement composite scaffolds than for calcium-phosphate cement scaffolds alone (6.4 +/- 0.6 MPa compared with 38.6 +/- 2.6 MPa, respectively). Average rhBMP-2 loading was 5.0 +/- 0.4 micro g per 75-mm (3) disk. Release of rhBMP-2 was limited for all formulations. At pH 7.4, 3.1% +/- 0.1% of the rhBMP-2 was released from the PLGA/calcium-phosphate cement disks and 18.0% +/- 1.9% was released from the PLGA microparticles alone after twenty-eight days. At pH 4.0, PLGA/calcium-phosphate cement disks revealed more release of rhBMP-2 than did PLGA microparticles alone (14.5% +/- 6.3% compared with 5.4% +/- 0.7%) by day 28. CONCLUSIONS These results indicate that preparation of a PLGA/calcium-phosphate cement composite for the delivery of rhBMP-2 is feasible and that the release of rhBMP-2 is dependent on the composite composition and nanostructure as well as the pH of the release medium.
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79
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Timmer MD, Shin H, Horch RA, Ambrose CG, Mikos AG. In vitro cytotoxicity of injectable and biodegradable poly(propylene fumarate)-based networks: unreacted macromers, cross-linked networks, and degradation products. Biomacromolecules 2003; 4:1026-33. [PMID: 12857088 DOI: 10.1021/bm0300150] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study evaluates the in vitro biocompatibility of an injectable and biodegradable polymeric network based on poly(propylene fumarate) (PPF) and the cross-linking agent PPF-diacrylate (PPF-DA). Using a methyl tetrazolium (MTT) assay, the effect of the concentrations of PPF and PPF-DA on the cytotoxicity of its unreacted macromers, cross-linked networks, and degradation products was examined. The influence of network structure properties on cell viability and attachment to the cross-linked material was also investigated. The unreacted macromers exhibited a time- and dose-dependent cytotoxic response that increased with more PPF-DA in the mixture. Conversely, the cross-linked networks formed with more PPF-DA did not demonstrate an adverse response because increases in conversion and cross-linking density prevented the extraction of toxic products. Fibroblast attachment was observed on the PPF/PPF-DA networks with the highest double bond conversions. The degradation products, obtained from the complete breakdown of the networks in basic conditions, displayed a dose-dependent cytotoxic response. These results show that there are concerns regarding the biocompatibility of injectable, biodegradable PPF/PPF-DA networks but also sheds light onto potential mechanisms to reduce the cytotoxic effects.
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Affiliation(s)
- Mark D Timmer
- Department of Bioengineering, Rice University, MS-142, Houston, Texas 77251-1892, USA
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80
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Abstract
The complex structure of articular cartilage, the connective tissue lining diarthrodial joints, enables this tissue to dissipate compressive loads but also appears to hinder its repair ability. At best, both natural and surgical repair attempts replace the highly ordered extracellular matrix of native articular cartilage with fibrous repair tissue of inferior mechanical properties. Numerous bioactive molecules closely regulate the cellular processes in healthy and degenerative articular cartilage. Accordingly, this review outlines the roles of important signaling molecules in cartilage tissue. In addition, drug delivery strategies, aimed at utilizing these bioactive agents to prevent inflammation, to regulate extracellular matrix metabolism, and to control cellular activities, are discussed. As scientists gain further insight into the complex signaling cascades of articular cartilage, continued refinement of drug delivery systems is necessary to develop effective clinical therapies for articular cartilage repair.
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Affiliation(s)
- Theresa A Holland
- Department of Bioengineering, Rice University, P O Box 1892, MS 142, Houston, TX 77251-1892, USA
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81
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Hoerstrup SP, Lu L, Lysaght MJ, Mikos AG, Rein D, Schoen FJ, Temenoff JS, Tessmar JK, Vacanti JP. Tissue Engineering. Biomater Sci 1996. [DOI: 10.1016/b978-012582460-6/50011-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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