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Natural and Synthetic Polymeric Scaffolds. Biomed Mater 2021. [DOI: 10.1007/978-3-030-49206-9_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Gascón E, Maisanaba S, Otal I, Valero E, Repetto G, Jones PG, Jiménez J. (Amino)cyclophosphazenes as Multisite Ligands for the Synthesis of Antitumoral and Antibacterial Silver(I) Complexes. Inorg Chem 2020; 59:2464-2483. [PMID: 31984738 DOI: 10.1021/acs.inorgchem.9b03334] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The reactivity of the multisite (amino)cyclotriphosphazene ligands, [N3P3(NHCy)6] and [N3P3(NHCy)3(NMe2)3], has been explored in order to obtain silver(I) metallophosphazene complexes. Two series of cationic silver(I) metallophosphazenes were obtained and characterized: [N3P3(NHCy)6{AgL}n](TfO)n [n = 2, L = PPh3 (2), PPh2Me (4); n = 3, L = PPh3 (3), PPh2Me (5), TPA (TPA = 1,3,5-triaza-7-phosphaadamantane, 6)] and nongem-trans-[N3P3(NHCy)3(NMe2)3{AgL}n](TfO)n [n = 2, L = PPh3 (7), PPh2Me (9); n = 3, L = PPh3 (8), PPh2Me (10)]. 5, 7, and 9 have also been characterized by single-crystal X-ray diffraction, thereby allowing key bonding information to be obtained. Compounds 2-6, 9, and 10 were screened for in vitro cytotoxic activity against two tumor human cell lines, MCF7 (breast adenocarcinoma) and HepG2 (hepatocellular carcinoma), and for antimicrobial activity against five bacterial species including Gram-positive, Gram-negative, and Mycobacteria strains. Both the IC50 and MIC values revealed excellent biological activity for these metal complexes, compared with their precursors and cisplatin and also AgNO3 and silver sulfadiazine, respectively. Both IC50 and MIC values are among the lowest values found for any silver derivatives against the cell lines and bacterial strains used in this work. The structure-activity relationships were clear. The most cytotoxic and antimicrobial derivatives were those with the triphenylphosphane and [N3P3(NHCy)6] ligands. A significant improvement in the activity was also observed upon a rise in the number of silver atoms linked to the phosphazene ring.
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Affiliation(s)
- Elena Gascón
- Departamento de Química Inorgánica, Facultad de Ciencias, Instituto de Síntesis Química y Catálisis Homogénea , Universidad de Zaragoza-CSIC , Pedro Cerbuna 12 , 50009 Zaragoza , Spain
| | - Sara Maisanaba
- Departamento de Biología Molecular e Ingeniería Bioquímica, Área de Toxicología , Universidad Pablo de Olavide , Ctra. Utrera, Km 1 , 41013 Sevilla , Spain
| | - Isabel Otal
- Grupo de Genética de Micobacterias, Departamento de Microbiología, Medicina Preventiva y Salud Pública , Universidad de Zaragoza , Zaragoza 50009 , Spain.,Instituto de Salud Carlos III , CIBER de Enfermedades Respiratorias , E-28029 Madrid , Spain
| | - Eva Valero
- Departamento de Biología Molecular e Ingeniería Bioquímica, Área Nutrición y Bromatología , Universidad Pablo de Olavide , Ctra. Utrera, Km 1 , 41013 Sevilla , Spain
| | - Guillermo Repetto
- Departamento de Biología Molecular e Ingeniería Bioquímica, Área de Toxicología , Universidad Pablo de Olavide , Ctra. Utrera, Km 1 , 41013 Sevilla , Spain
| | - Peter G Jones
- Institut für Anorganische und Analytische Chemie , Technische Universität Braunschweig , Hagenring 30 , D-38106 Braunschweig , Germany
| | - Josefina Jiménez
- Departamento de Química Inorgánica, Facultad de Ciencias, Instituto de Síntesis Química y Catálisis Homogénea , Universidad de Zaragoza-CSIC , Pedro Cerbuna 12 , 50009 Zaragoza , Spain
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Synthesis, Characterization and Hydrolytic Degradation of p-Cresol-Substituted Polyphosphazenes. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2019. [DOI: 10.1007/s13369-019-03952-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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4
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Petcu EB, Midha R, McColl E, Popa-Wagner A, Chirila TV, Dalton PD. 3D printing strategies for peripheral nerve regeneration. Biofabrication 2018; 10:032001. [DOI: 10.1088/1758-5090/aaaf50] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Khan RU, Wang L, Yu H, Zain-ul-Abdin, Akram M, Wu J, Haroon M, Ullah RS, Deng Z, Xia X. Recent progress in the synthesis of poly(organo)phosphazenes and their applications in tissue engineering and drug delivery. RUSSIAN CHEMICAL REVIEWS 2018. [DOI: 10.1070/rcr4757] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ogueri KS, Escobar Ivirico JL, Nair LS, Allcock HR, Laurencin CT. Biodegradable Polyphosphazene-Based Blends for Regenerative Engineering. REGENERATIVE ENGINEERING AND TRANSLATIONAL MEDICINE 2017; 3:15-31. [PMID: 28596987 DOI: 10.1007/s40883-016-0022-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The occurrence of musculoskeletal tissue injury or disease and the subsequent functional impairment is at an alarming rate. It continues to be one of the most challenging problems in the human health care. Regenerative engineering offers a promising transdisciplinary strategy for tissues regeneration based on the convergence of tissue engineering, advanced materials science, stem cell science, developmental biology and clinical translation. Biomaterials are emerging as extracellular-mimicking matrices designed to provide instructive cues to control cell behavior and ultimately, be applied as therapies to regenerate damaged tissues. Biodegradable polymers constitute an attractive class of biomaterials for the development of scaffolds due to their flexibility in chemistry and the ability to be excreted or resorbed by the body. Herein, the focus will be on biodegradable polyphosphazene-based blend systems. The synthetic flexibility of polyphosphazene, combined with the unique inorganic backbone, has provided a springboard for more research and subsequent development of numerous novel materials that are capable of forming miscible blends with poly (lactide-co-glycolide) (PLAGA). Laurencin and co-workers has demonstrated the exploitation of the synthetic flexibility of Polyphosphazene that will allow the design of novel polymers, which can form miscible blends with PLAGA for biomedical applications. These novel blends, due to their well-tuned biodegradability, and mechanical and biological properties coupled with the buffering capacity of the degradation products, constitute ideal materials for regeneration of various musculoskeletal tissues. LAY SUMMARY Regenerative engineering aims to regenerate complex tissues to address the clinical challenge of organ damage. Tissue engineering has largely focused on the restoration and repair of individual tissues and organs, but over the past 25 years, scientific, engineering, and medical advances have led to the introduction of this new approach which involves the regeneration of complex tissues and biological systems such as a knee or a whole limb. While a number of excellent advanced biomaterials have been developed, the choice of biomaterials, however, has increased over the past years to include polymers that can be designed with a range of mechanical properties, degradation rates, and chemical functionality. The polyphosphazenes are one good example. Their chemical versatility and hydrogen bonding capability encourages blending with other biologically relevant polymers. The further development of Polyphosphazene-based blends will present a wide spectrum of advanced biomaterials that can be used as scaffolds for regenerative engineering and as well as other biomedical applications.
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Affiliation(s)
- Kenneth S Ogueri
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269, USA.,Institute for Regenerative Engineering, University of Connecticut Health Center, Farmington, CT 06030, USA.,Raymond and Beverly Sackler Center for Biomedical, Biological, Physical and Engineering Sciences, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Jorge L Escobar Ivirico
- Institute for Regenerative Engineering, University of Connecticut Health Center, Farmington, CT 06030, USA.,Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT 06030, USA.,Raymond and Beverly Sackler Center for Biomedical, Biological, Physical and Engineering Sciences, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Lakshmi S Nair
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269, USA.,Institute for Regenerative Engineering, University of Connecticut Health Center, Farmington, CT 06030, USA.,Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT 06030, USA.,Raymond and Beverly Sackler Center for Biomedical, Biological, Physical and Engineering Sciences, University of Connecticut Health Center, Farmington, CT 06030, USA.,Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - Harry R Allcock
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Cato T Laurencin
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT 06269, USA.,Institute for Regenerative Engineering, University of Connecticut Health Center, Farmington, CT 06030, USA.,Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT 06030, USA.,Raymond and Beverly Sackler Center for Biomedical, Biological, Physical and Engineering Sciences, University of Connecticut Health Center, Farmington, CT 06030, USA.,Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA.,Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, CT 06269, USA
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Ullah RS, Wang L, Yu H, Abbasi NM, Akram M, -ul-Abdin Z, Saleem M, Haroon M, Khan RU. Synthesis of polyphosphazenes with different side groups and various tactics for drug delivery. RSC Adv 2017. [DOI: 10.1039/c6ra27103k] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Polyphosphazenes (PPZs) are hybrid polymers comprising a main chain containing nitrogen and phosphorous linked through interchanging single and double bonds, and side chains.
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Affiliation(s)
- Raja Summe Ullah
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Li Wang
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Haojie Yu
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Nasir M. Abbasi
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Muhammad Akram
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Zain -ul-Abdin
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Muhammad Saleem
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Muhammad Haroon
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
| | - Rizwan Ullah Khan
- State Key Laboratory of Chemical Engineering
- College of Chemical and Biological Engineering
- Zhejiang University
- Hangzhou 310027
- China
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8
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Olfactory ensheathing glia cell therapy and tubular conduit enhance nerve regeneration after mouse sciatic nerve transection. Brain Res 2016; 1650:243-251. [PMID: 27641994 DOI: 10.1016/j.brainres.2016.09.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/02/2016] [Accepted: 09/15/2016] [Indexed: 02/06/2023]
Abstract
The regenerative potential of the peripheral nervous system (PNS) is widely known, but functional recovery, particularly in humans, is seldom complete. Therefore, it is necessary to resort to strategies that induce or potentiate the PNS regeneration. Our main objective was to test the effectiveness of Olfactory Ensheathing Cells (OEC) transplantation into a biodegradable conduit as a therapeutic strategy to improve the repair outcome after nerve injury. Sciatic nerve transection was performed in C57BL/6 mice; proximal and distal stumps of the nerve were sutured into the collagen conduit. Two groups were analyzed: DMEM (acellular grafts) and OEC (1×105/2μL). Locomotor function was assessed weekly by Sciatic Function Index (SFI) and Global Mobility Test (GMT). After eight weeks the sciatic nerve was dissected for morphological analysis. Our results showed that the OEC group exhibited many clusters of regenerated nerve fibers, a higher number of myelinated fibers and myelin area compared to DMEM group. The G-ratio analysis of the OEC group showed significantly more fibers on the most suitable sciatic nerve G-ratio index. Motor recovery was accelerated in the OEC group. These data provide evidence that the OEC therapy can improve sciatic nerve functional and morphological recovery and can be potentially translated to the clinical setting.
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Aldini NN, Fini M, Rocca M, Martini L, Giardino R, Caliceti P, Veronese FM, Lora S, Maltarello MC. Peripheral Nerve Reconstruction with Bioabsorbable Polyphosphazene Conduits. J BIOACT COMPAT POL 2016. [DOI: 10.1177/088391159701200101] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Tubes of poly[bis(ethylalanato)phosphazene], obtained by evaporating the polymer around a 1.3 mm diameter capillary, were evaluated as guides for nerve regeneration in an experimental animal model. In six Wistar rats, under general anesthesia and with microsurgical technique, the ischiatic nerve was bilaterally isolated. On the right side, a segment was removed to create a defect of 10 mm, that was repaired with the conduit; on the left side the defect was repaired with harvested nerve segment from the right side. Controls at 30, 90, 180 days showed slow and gradual absorption of the conduit without signs of local or general toxicity. Nerve fiber regeneration in the conduits was not significantly different from that obtained with autologous grafts. Polyphosphazene conduits may be considered effective as a guide for nerve regeneration mainly in the perspective of using the polymer matrix as a carrier for neurite-promoting factors.
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Affiliation(s)
- N. Nicoli Aldini
- Experimental Surgery Dept., Istituto di Ricerca Codivilla-Putti I.O.R., Bologna, Italy
| | - M. Fini
- Experimental Surgery Dept., Istituto di Ricerca Codivilla-Putti I.O.R., Bologna, Italy
| | - M. Rocca
- Experimental Surgery Dept., Istituto di Ricerca Codivilla-Putti I.O.R., Bologna, Italy
| | - L. Martini
- Experimental Surgery Dept., Istituto di Ricerca Codivilla-Putti I.O.R., Bologna, Italy
| | - R. Giardino
- Experimental Surgery Dept., Istituto di Ricerca Codivilla-Putti I.O.R., Bologna, Italy
| | - P. Caliceti
- Pharmaceutical Sciences Department, University of Padova, Padova, Italy
| | - F. M. Veronese
- Pharmaceutical Sciences Department, University of Padova, Padova, Italy
| | - S. Lora
- Institute of Photochemistry and High Energy Radiations, C.N.R., Legnaro, Padova, Italy
| | - M. C. Maltarello
- Cellular Biology and Electron Microscopy Lab., Istituto di Ricerca Codivilla-Putti L.O.R., Bologna, Italy
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Li Q, Li T, Cao XC, Luo DQ, Lian KJ. Methylprednisolone microsphere sustained-release membrane inhibits scar formation at the site of peripheral nerve lesion. Neural Regen Res 2016; 11:835-41. [PMID: 27335571 PMCID: PMC4904478 DOI: 10.4103/1673-5374.182713] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Corticosteroids are widely used for the treatment of acute central nervous system injury. However, their bioactivity is limited by their short half-life. Sustained release of glucocorticoids can prolong their efficacy and inhibit scar formation at the site of nerve injury. In the present study, we wrapped the anastomotic ends of the rat sciatic nerve with a methylprednisolone sustained-release membrane. Compared with methylprednisone alone or methylprednisone microspheres, the methylprednisolone microsphere sustained-release membrane reduced tissue adhesion and inhibited scar tissue formation at the site of anastomosis. It also increased sciatic nerve function index and the thickness of the myelin sheath. Our findings show that the methylprednisolone microsphere sustained-release membrane effectively inhibits scar formation at the site of anastomosis of the peripheral nerve, thereby promoting nerve regeneration.
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Affiliation(s)
- Qiang Li
- The Affiliated Dongnan Hospital of Xiamen University, Zhangzhou, Fujian Province, China
| | - Teng Li
- The Affiliated Dongnan Hospital of Xiamen University, Zhangzhou, Fujian Province, China
| | - Xiang-Chang Cao
- The Affiliated Dongnan Hospital of Xiamen University, Zhangzhou, Fujian Province, China
| | - De-Qing Luo
- The Affiliated Dongnan Hospital of Xiamen University, Zhangzhou, Fujian Province, China
| | - Ke-Jian Lian
- The Affiliated Dongnan Hospital of Xiamen University, Zhangzhou, Fujian Province, China
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Sivagangi Reddy N, Krishna Rao KSV, Eswaramma S, Madhusudana Rao K. Synthesis of dual responsive cyclotriphosphazene-based IPN hydrogels for controlled release of chemotherapeutic agent. POLYM ADVAN TECHNOL 2015. [DOI: 10.1002/pat.3650] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- N. Sivagangi Reddy
- Polymer Biomaterial Design and Synthesis Laboratory, Department of Chemistry; Yogi Vemana University; Kadapa Andhra Pradesh 516003 India
| | - K. S. V. Krishna Rao
- Polymer Biomaterial Design and Synthesis Laboratory, Department of Chemistry; Yogi Vemana University; Kadapa Andhra Pradesh 516003 India
- Department of Chemical Engineering and Material Science; Wayne State University; Detroit MI 48202 USA
| | - S. Eswaramma
- Polymer Biomaterial Design and Synthesis Laboratory, Department of Chemistry; Yogi Vemana University; Kadapa Andhra Pradesh 516003 India
| | - K. Madhusudana Rao
- Nano Information Materials Laboratory, Department of Polymer Science and Engineering; Pusan National University; Busan 609735 South Korea
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12
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Demir Y. Epineural Sheath Grafts for Nerve Regeneration. Plast Reconstr Surg 2015. [DOI: 10.1007/978-1-4471-6335-0_56] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Biodegradable polyphosphazene biomaterials for tissue engineering and delivery of therapeutics. BIOMED RESEARCH INTERNATIONAL 2014; 2014:761373. [PMID: 24883323 PMCID: PMC4022062 DOI: 10.1155/2014/761373] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 03/29/2014] [Indexed: 12/22/2022]
Abstract
Degradable biomaterials continue to play a major role in tissue engineering and regenerative medicine as well as for delivering therapeutic agents. Although the chemistry of polyphosphazenes has been studied extensively, a systematic review of their applications for a wide range of biomedical applications is lacking. Polyphosphazenes are synthesized through a relatively well-known two-step reaction scheme which involves the substitution of the initial linear precursor with a wide range of nucleophiles. The ease of substitution has led to the development of a broad class of materials that have been studied for numerous biomedical applications including as scaffold materials for tissue engineering and regenerative medicine. The objective of this review is to discuss the suitability of poly(amino acid ester)phosphazene biomaterials in regard to their unique stimuli responsive properties, tunable degradation rates and mechanical properties, as well as in vitro and in vivo biocompatibility. The application of these materials in areas such as tissue engineering and drug delivery is discussed systematically. Lastly, the utility of polyphosphazenes is further extended as they are being employed in blend materials for new applications and as another method of tailoring material properties.
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Félix SP, Pereira Lopes FR, Marques SA, Martinez AM. Comparison between suture and fibrin glue on repair by direct coaptation or tubulization of injured mouse sciatic nerve. Microsurgery 2013; 33:468-77. [DOI: 10.1002/micr.22109] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 02/20/2013] [Accepted: 02/25/2013] [Indexed: 12/12/2022]
Affiliation(s)
- Severina P. Félix
- Laboratório de Neurodegeneração e Reparo; Programa de Pesquisa em Neurociência Básica e Clínica; Instituto de Ciências Biomédicas; Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ Brazil
- Departamento de Patologia; Faculdade de Medicina; Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ Brazil
| | - Fátima R. Pereira Lopes
- Laboratório de Neurodegeneração e Reparo; Programa de Pesquisa em Neurociência Básica e Clínica; Instituto de Ciências Biomédicas; Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ Brazil
| | - Suelen A. Marques
- Laboratórios de Regeneração Neural e Função; Departamento de Neurobiologia; Universidade Federal Fluminense; Niterói RJ Brazil
| | - Ana M.B. Martinez
- Laboratório de Neurodegeneração e Reparo; Programa de Pesquisa em Neurociência Básica e Clínica; Instituto de Ciências Biomédicas; Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ Brazil
- Departamento de Patologia; Faculdade de Medicina; Universidade Federal do Rio de Janeiro; Rio de Janeiro RJ Brazil
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Fitzpatrick SD, Fitzpatrick LE, Thakur A, Mazumder MAJ, Sheardown H. Temperature-sensitive polymers for drug delivery. Expert Rev Med Devices 2013; 9:339-51. [PMID: 22905838 DOI: 10.1586/erd.12.24] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The ability to undergo rapid changes in response to subtle environmental cues make stimuli- responsive materials attractive candidates for minimally invasive, targeted and personalized drug delivery applications. This special report aims to highlight and provide a brief description of several of the significant natural and synthetic temperature-responsive materials that have clinical relevance for drug delivery applications. This report examines the advantages and disadvantages of natural versus synthetic materials and outlines various scaffold architectures that can be utilized with temperature-sensitive drug delivery materials. The authors provide a commentary on the current state of the field and provide their insight into future expectations for temperature-sensitive drug delivery, emphasizing the importance of the emergence of dual and multiresponsive systems capable of responding precisely to an expanding set of stimuli, thereby allowing the development of disease-specific drug delivery vehicles.
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Affiliation(s)
- Scott D Fitzpatrick
- School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada
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Building biocompatible hydrogels for tissue engineering of the brain and spinal cord. J Funct Biomater 2012; 3:839-63. [PMID: 24955749 PMCID: PMC4030922 DOI: 10.3390/jfb3040839] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 10/24/2012] [Indexed: 01/07/2023] Open
Abstract
Tissue engineering strategies employing biomaterials have made great progress in the last few decades. However, the tissues of the brain and spinal cord pose unique challenges due to a separate immune system and their nature as soft tissue. Because of this, neural tissue engineering for the brain and spinal cord may require re-establishing biocompatibility and functionality of biomaterials that have previously been successful for tissue engineering in the body. The goal of this review is to briefly describe the distinctive properties of the central nervous system, specifically the neuroimmune response, and to describe the factors which contribute to building polymer hydrogels compatible with this tissue. These factors include polymer chemistry, polymerization and degradation, and the physical and mechanical properties of the hydrogel. By understanding the necessities in making hydrogels biocompatible with tissue of the brain and spinal cord, tissue engineers can then functionalize these materials for repairing and replacing tissue in the central nervous system.
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Rai R, Tallawi M, Grigore A, Boccaccini AR. Synthesis, properties and biomedical applications of poly(glycerol sebacate) (PGS): A review. Prog Polym Sci 2012. [DOI: 10.1016/j.progpolymsci.2012.02.001] [Citation(s) in RCA: 334] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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HUANG YICHENG, HUANG YIYOU. TISSUE ENGINEERING FOR NERVE REPAIR. BIOMEDICAL ENGINEERING-APPLICATIONS BASIS COMMUNICATIONS 2012. [DOI: 10.4015/s101623720600018x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Nerve regeneration is a complex biological phenomenon. Once the nervous system is impaired, its recovery is difficult and malfunctions in other parts of the body may occur because mature neurons don't undergo cell division. To increase the prospects of axonal regeneration and functional recovery, researches have focused on designing “nerve guidance channels” or “nerve conduits”. For developing tissue engineered nerve conduits, four components come to mind, including a scaffold for axonal proliferation, supporting cells such as Schwann cells, growth factors, and extracelluar matrix. This article reviews the nervous system physiology, the factors that are critical for nerve repair, and the advanced technologies that are explored to fabricate nerve conduits. Furthermore, we also introduce a new method we developed to create longitudinally oriented channels within biodegradable polymers, Chitosan and PLGA, using a combined lyophilizing and wire-heating process. This innovative method using Ni-Cr wires as mandrels to create nerve guidance channels. The process is easy, straightforward, highly reproducible, and could easily be tailored to other polymer and solvent systems. These scaffolds could be useful for guided regeneration after transection injury in either the peripheral nerve or spinal cord.
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Affiliation(s)
- YI-CHENG HUANG
- Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei, Taiwan
| | - YI-YOU HUANG
- Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei, Taiwan
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Aurand ER, Lampe KJ, Bjugstad KB. Defining and designing polymers and hydrogels for neural tissue engineering. Neurosci Res 2011; 72:199-213. [PMID: 22192467 DOI: 10.1016/j.neures.2011.12.005] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/07/2011] [Accepted: 12/07/2011] [Indexed: 12/16/2022]
Abstract
The use of biomaterials, such as hydrogels, as neural cell delivery devices is becoming more common in areas of research such as stroke, traumatic brain injury, and spinal cord injury. When reviewing the available research there is some ambiguity in the type of materials used and results are often at odds. This review aims to provide the neuroscience community who may not be familiar with fundamental concepts of hydrogel construction, with basic information that would pertain to neural tissue applications, and to describe the use of hydrogels as cell and drug delivery devices. We will illustrate some of the many tunable properties of hydrogels and the importance of these properties in obtaining reliable and consistent results. It is our hope that this review promotes creative ideas for ways that hydrogels could be adapted and employed for the treatment of a broad range of neurological disorders.
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Affiliation(s)
- Emily R Aurand
- Neuroscience Program, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO 80045, USA.
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Siemionow M, Bozkurt M, Zor F. Regeneration and repair of peripheral nerves with different biomaterials: review. Microsurgery 2011; 30:574-88. [PMID: 20878689 DOI: 10.1002/micr.20799] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Peripheral nerve injury may cause gaps between the nerve stumps. Axonal proliferation in nerve conduits is limited to 10-15 mm. Most of the supportive research has been done on rat or mouse models which are different from humans. Herein we review autografts and biomaterials which are commonly used for nerve gap repair and their respective outcomes. Nerve autografting has been the first choice for repairing peripheral nerve gaps. However, it has been demonstrated experimentally that tissue engineered tubes can also permit lead to effective nerve repair over gaps longer than 4 cm repair that was previously thought to be restorable by means of nerve graft only. All of the discoveries in the nerve armamentarium are making their way into the clinic, where they are, showing great potential for improving both the extent and rate of functional recovery compared with alternative nerve guides.
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Affiliation(s)
- Maria Siemionow
- Department of Plastic Surgery, The Cleveland Clinic, Cleveland, OH 44195, USA.
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22
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Pasut G, Veronese FM. Improvement of Drug Therapy by Covalent PEG Conjugation: An Overview From a Research Laboratory. Isr J Chem 2010. [DOI: 10.1002/ijch.201000019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Bjugstad KB, Lampe K, Kern DS, Mahoney M. Biocompatibility of poly(ethylene glycol)-based hydrogels in the brain: An analysis of the glial response across space and time. J Biomed Mater Res A 2010; 95:79-91. [DOI: 10.1002/jbm.a.32809] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Sethuraman S, Nair LS, El-Amin S, Nguyen MT, Singh A, Krogman N, Greish YE, Allcock HR, Brown PW, Laurencin CT. Mechanical properties and osteocompatibility of novel biodegradable alanine based polyphosphazenes: Side group effects. Acta Biomater 2010; 6:1931-7. [PMID: 20004751 PMCID: PMC2862891 DOI: 10.1016/j.actbio.2009.12.012] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 12/04/2009] [Accepted: 12/04/2009] [Indexed: 11/28/2022]
Abstract
The versatility of polymers for tissue regeneration lies in the feasibility to modulate the physical and biological properties by varying the side groups grafted to the polymers. Biodegradable polyphosphazenes are high-molecular-weight polymers with alternating nitrogen and phosphorus atoms in the backbone. This study is the first of its kind to systematically investigate the effect of side group structure on the compressive strength of novel biodegradable polyphosphazene based polymers as potential materials for tissue regeneration. The alanine polyphosphazene based polymers, poly(bis(ethyl alanato) phosphazene) (PNEA), poly((50% ethyl alanato) (50% methyl phenoxy) phosphazene) (PNEA(50)mPh(50)), poly((50% ethyl alanato) (50% phenyl phenoxy) phosphazene) (PNEA(50)PhPh(50)) were investigated to demonstrate their mechanical properties and osteocompatibility. Results of mechanical testing studies demonstrated that the nature and the ratio of the pendent groups attached to the polymer backbone play a significant role in determining the mechanical properties of the resulting polymer. The compressive strength of PNEA(50)PhPh(50) was significantly higher than poly(lactide-co-glycolide) (85:15 PLAGA) (p<0.05). Additional studies evaluated the cellular response and gene expression of primary rat osteoblast cells on PNEA, PNEA(50)mPh(50) and PNEA(50)PhPh(50) films as candidates for bone tissue engineering applications. Results of the in vitro osteocompatibility evaluation demonstrated that cells adhere, proliferate, and maintain their phenotype when seeded directly on the surface of PNEA, PNEA(50)mPh(50), and PNEA(50)PhPh(50). Moreover, cells on the surface of the polymers expressed type I collagen, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein, which are characteristic genes for osteoblast maturation, differentiation, and mineralization.
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Affiliation(s)
| | - Lakshmi S. Nair
- Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, USA
- Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, USA
| | - Saadiq El-Amin
- Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, USA
| | - My-Tien Nguyen
- Department of Biology, University of Virginia, Charlottesville, USA
| | - Anurima Singh
- Department of Chemistry, Pennsylvania State University, University Park, USA
| | - Nick Krogman
- Department of Chemistry, Pennsylvania State University, University Park, USA
| | - Yaser E. Greish
- Materials Research Institute Pennsylvania State University, University Park, USA
| | - Harry R. Allcock
- Department of Chemistry, Pennsylvania State University, University Park, USA
| | - Paul W. Brown
- Materials Research Institute Pennsylvania State University, University Park, USA
| | - Cato T. Laurencin
- Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, USA
- Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, USA
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Pereira Lopes FR, Frattini F, Marques SA, Almeida FMD, de Moura Campos LC, Langone F, Lora S, Borojevic R, Martinez AMB. Transplantation of bone-marrow-derived cells into a nerve guide resulted in transdifferentiation into Schwann cells and effective regeneration of transected mouse sciatic nerve. Micron 2010; 41:783-90. [PMID: 20728816 DOI: 10.1016/j.micron.2010.05.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 05/18/2010] [Accepted: 05/19/2010] [Indexed: 12/28/2022]
Abstract
Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Nevertheless, the functional outcome after peripheral-nerve regeneration is often poor, especially if the nerve injuries occur far from their targets. Aiming to optimize axon regeneration, we grafted bone-marrow-derived cells (BMDCs) into a collagen-tube nerve guide after transection of the mouse sciatic nerve. The control group received only the culture medium. Motor function was tested at 2, 4, and 6 weeks after surgery, using the sciatic functional index (SFI), and showed that functional recovery was significantly improved in animals that received the cell grafts. After 6 weeks, the mice were anesthetized, perfused transcardially, and the sciatic nerves were dissected and processed for transmission electron microscopy and light microscopy. The proximal and distal segments of the nerves were compared, to address the question of improvement in growth rate; the results revealed a maintenance and increase of nerve regeneration for both myelinated and non-myelinated fibers in distal segments of the experimental group. Also, quantitative analysis of the distal region of the regenerating nerves showed that the numbers of myelinated fibers, Schwann cells (SCs) and g-ratio were significantly increased in the experimental group compared to the control group. The transdifferentiation of BMDCs into Schwann cells was confirmed by double labeling with S100/and Hoechst staining. Our data suggest that BMDCs transplanted into a nerve guide can differentiate into SCs, and improve the growth rate of nerve fibers and motor function in a transected sciatic-nerve model.
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Wang JH, Lin UH, Lin CH, Chung YC, Chen CR, Kao YC, Lai JY, Young TH. Change in neuron aggregation and neurite fasciculation on EVAL membranes modified with different diamines. J Biomed Mater Res A 2010; 94:489-98. [PMID: 20186774 DOI: 10.1002/jbm.a.32716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, we modified poly(ethylene-co-vinyl alcohol) (EVAL) membranes by the covalent bonding of diamines via epoxidation of surface hydroxyl groups of EVAL to analyze the effect of immobilized diamines with different carbon chain length on the cultured cerebellar granule neurons. Morphological studies showed that neurons seeded on the diamine-immobilized EVAL membrane were able to survive and regenerate with formation of an extensive neuritic network. Furthermore, cultured neurons showed that the presence of diamine with different carbon chain length was able to effectively regulate the neuron adhesion, migration, aggregation, and neurite growth pattern, but mediated neuronal activity with equal efficacy. The short-chain amine stimulated neuron migration, aggregation, and neurite fasciculation, whereas the long carbon chain diamine maintained single neuron distribution with the defasciculated feature of the neurite. Although it is known that positively charged amine molecules can interact directly with cell surface proteoglycans to mediate cell attachment, this study further demonstrated that the terminal primary amine with different carbon chain length is involved in mediating cell-substrate interaction to further regulate neuron aggregation and neurite fasciculation. This indicates a delicate interaction of neuron with the immobilized diamine molecules on the EVAL membrane surface. This work is encouraging because the diamine- immobilized EVAL membranes can be applied for the establishment of different neural culture systems useful for future investigations of neuron biology under in vitro conditions.
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Affiliation(s)
- Jyh-Horng Wang
- Department of Orthopedic Surgery, National Taiwan University Hospital, Taipei, Taiwan, Republic of China
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Trophic activity derived from bone marrow mononuclear cells increases peripheral nerve regeneration by acting on both neuronal and glial cell populations. Neuroscience 2009; 159:540-9. [PMID: 19174184 DOI: 10.1016/j.neuroscience.2008.12.059] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Revised: 12/11/2008] [Accepted: 12/23/2008] [Indexed: 12/23/2022]
Abstract
A rat model of complete sciatic nerve transection was used to evaluate the effect of bone marrow mononuclear cells (BMMC) transplanted to the injury site immediately after lesion. Rats treated with BMMC had both sensory and motor axons reaching the distal stump earlier compared to untreated animals. In addition, BMMC transplantation reduced cell death in dorsal root ganglia (DRG) compared to control animals. Transplanted BMMC remained in the lesion site for several days but there is no evidence of BMMC differentiation into Schwann cells. However, an increase in the number of Schwann cells, satellite cells and astrocytes was observed in the treated group. Moreover, neutralizing antibodies for nerve growth factor (NGF) (but not for brain-derived neurotrophic factor and ciliary-derived neurotrophic factor) added to the BMMC-conditioned medium reduced neurite growth of sensory and sympathetic neurons in vitro, suggesting that BMMC release NGF, improve regeneration of the sciatic nerve in the adult rat and stimulate Schwann and satellite cell proliferation or a combination of both.
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Prabhakaran MP, Venugopal J, Chan CK, Ramakrishna S. Surface modified electrospun nanofibrous scaffolds for nerve tissue engineering. NANOTECHNOLOGY 2008; 19:455102. [PMID: 21832761 DOI: 10.1088/0957-4484/19/45/455102] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The development of biodegradable polymeric scaffolds with surface properties that dominate interactions between the material and biological environment is of great interest in biomedical applications. In this regard, poly-ε-caprolactone (PCL) nanofibrous scaffolds were fabricated by an electrospinning process and surface modified by a simple plasma treatment process for enhancing the Schwann cell adhesion, proliferation and interactions with nanofibers necessary for nerve tissue formation. The hydrophilicity of surface modified PCL nanofibrous scaffolds (p-PCL) was evaluated by contact angle and x-ray photoelectron spectroscopy studies. Naturally derived polymers such as collagen are frequently used for the fabrication of biocomposite PCL/collagen scaffolds, though the feasibility of procuring large amounts of natural materials for clinical applications remains a concern, along with their cost and mechanical stability. The proliferation of Schwann cells on p-PCL nanofibrous scaffolds showed a 17% increase in cell proliferation compared to those on PCL/collagen nanofibrous scaffolds after 8 days of cell culture. Schwann cells were found to attach and proliferate on surface modified PCL nanofibrous scaffolds expressing bipolar elongations, retaining their normal morphology. The results of our study showed that plasma treated PCL nanofibrous scaffolds are a cost-effective material compared to PCL/collagen scaffolds, and can potentially serve as an ideal tissue engineered scaffold, especially for peripheral nerve regeneration.
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Yildirim ED, Yin X, Nair K, Sun W. Fabrication, characterization, and biocompatibility of single-walled carbon nanotube-reinforced alginate composite scaffolds manufactured using freeform fabrication technique. J Biomed Mater Res B Appl Biomater 2008; 87:406-14. [DOI: 10.1002/jbm.b.31118] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Ichihara S, Inada Y, Nakamura T. Artificial nerve tubes and their application for repair of peripheral nerve injury: an update of current concepts. Injury 2008; 39 Suppl 4:29-39. [PMID: 18804584 DOI: 10.1016/j.injury.2008.08.029] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Over the last 20 years, an increasing number of research articles have reported on the use of artificial nerve tubes to repair nerve defects. The development of an artificial nerve tube as an alternative to autogenous nerve grafting is currently a focus of interest for peripheral nerve repair. The clinical employment of tubes as an alternative to autogenous nerve grafts is mainly justified by the limited availability of donor tissue for nerve autografts and the related morbidity. Numerous studies indicate that short-distance defects in humans can be successfully treated by implantation of artificial nerve guides. This review provides a brief overview of various preclinical and clinical trials conducted to evaluate the utility of artificial nerve tubes for the regeneration of peripheral nerves. This review is also intended to help update hand surgeons on the rapid advances in tubulization techniques, and to provide them with indications of the various directions toward which future research can proceed. Future studies need to provide us with as much comparative information as possible on the effectiveness of different tubulization techniques, in order to guide the surgeon in choosing the best indications for their optimal clinical employment. Future progress in implant development can be expected from interdisciplinary approaches involving both materials and life sciences, leading to advances in neuro-tissue engineering that will be needed to effectively treat larger nerve defects.
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Affiliation(s)
- Satoshi Ichihara
- Department of Bioartificial Organs, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan
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Johnson EO, Soucacos PN. Nerve repair: experimental and clinical evaluation of biodegradable artificial nerve guides. Injury 2008; 39 Suppl 3:S30-6. [PMID: 18722612 DOI: 10.1016/j.injury.2008.05.018] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Several methods have been used for bridging nerve gaps. Much of the focus in nerve repair of peripheral nerves has focussed on creating either natural or synthetic tubular nerve guidance channels, as an alternative to nerve autografts. These conduits act to guide axons sprouting from the regenerating nerve end, provide a conduit for diffusion of neurotrophic and neurotropic factors secreted by the injured nerve stump, as well as help protect against infiltration of fibrous tissue. Among the conduits that have been studied are autogenous veins, arteries, mesothelial chambers, synthetic tubes, collagen tubes, amnion tubes, cardiac and skeletal muscle, and silicon tubes. This paper briefly reviews major studies in which bioabsorbable nerve guides were used for peripheral nerve repair, with a particular emphasis on polymeric guidance channels, in an effort to evaluate their use, their ability to support or enhance nerve regeneration and any potential problems.
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Affiliation(s)
- Elizabeth O Johnson
- Department of Anatomy, Histology & Embryology, University of Ioannina, School of Medicine, 45110 Ioannina, Greece.
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33
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Bjugstad KB, Redmond DE, Lampe KJ, Kern DS, Sladek JR, Mahoney MJ. Biocompatibility of PEG-Based Hydrogels in Primate Brain. Cell Transplant 2008. [DOI: 10.3727/096368908784423292] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Degradable polymers have been used successfully in a wide variety of peripheral applications from tissue regeneration to drug delivery. These polymers induce little inflammatory response and appear to be well accepted by the host environment. Their use in the brain, for neural tissue reconstruction or drug delivery, also could be advantageous in treating neurodegenerative disorders. Because the brain has a unique immune response, a polymer that is compatible in the body may not be so in the brain. In the present study, polyethylene glycol (PEG)-based hydrogels were implanted into the striatum and cerebral cortex of nonhuman primates. Four months after implantation, brains were processed to evaluate the extent of astrogliosis and scaring, the presence of microglia/macrophages, and the extent of T-cell infiltration. Hydrogels with 20% w/v PEG implanted into the brain stimulated a slight increase in astrocytic and microglial/macrophage presence, as indicated by a small increase in glial fibrillary acidic protein (GFAP) and CD68 staining intensity. This increase was not substantially different from that found in the sham-implanted hemispheres of the brain. Staining for CD3+ T cells indicated no presence of peripheral T-cell infiltration. No gliotic scarring was seen in any implanted hemisphere. The combination of low density of GFAP-positive cells and CD68-positive cells, the absence of T cells, and the lack of gliotic scarring suggest that this level of immune response is not indicative of immunorejection and that the PEG-based hydrogel has potential to be used in the primate brain for local drug delivery or neural tissue regeneration.
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Affiliation(s)
- K. B. Bjugstad
- Department Pediatrics, University Colorado Denver and Health Sciences Center, Aurora, CO, USA
| | - D. E. Redmond
- Departments Psychiatry and Neurosurgery, Yale University, New Haven, CT, USA
| | - K. J. Lampe
- Department Chemical and Biological Engineering, University Colorado, Boulder, CO, USA
| | - D. S. Kern
- Department Pediatrics, University Colorado Denver and Health Sciences Center, Aurora, CO, USA
| | - J. R. Sladek
- Department Pediatrics, University Colorado Denver and Health Sciences Center, Aurora, CO, USA
| | - M. J. Mahoney
- Department Chemical and Biological Engineering, University Colorado, Boulder, CO, USA
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Vein Grafts Used as Nerve Conduits for Obstetrical Brachial Plexus Palsy Reconstruction. Plast Reconstr Surg 2007; 120:1930-1941. [DOI: 10.1097/01.prs.0000287391.12943.00] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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35
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Yin L, Huang X, Tang X. Synthesis, characterization and hydrolytic degradation of linear and crosslinked poly[(glycino ethyl ester)(allyl amino)phosphazene]. Polym Degrad Stab 2007. [DOI: 10.1016/j.polymdegradstab.2007.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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36
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Heyde M, Moens M, Van Vaeck L, Shakesheff KM, Davies MC, Schacht EH. Synthesis and Characterization of Novel Poly[(organo)phosphazenes] with Cell-Adhesive Side Groups. Biomacromolecules 2007; 8:1436-45. [PMID: 17391003 DOI: 10.1021/bm060926k] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
There is a need to develop new scaffold materials with controlled surface properties for tissue engineering applications. For that purpose novel biodegradable poly[(organo)phosphazenes] were synthesized. A cell-binding molecule, galactose, was introduced via a spacer, either 6-aminohexanol (AH) or poly(ethylene glycol) (PEG; M(w) = 3400). Some polymers were substituted with an additional PEG chain of different molecular weights (M(w) = 750 or 5000). The polyphosphazene derivatives were characterized by 1H NMR. T(g) and T(m) were determined using differential scanning calorimetry. A detailed surface analysis of the polymers using X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), and dynamic contact angle (DCA) measurements was performed. Typical backbone and side chain fragments were detected by SIMS and confirmed the polymer composition. Compared to that of the reference polymer (having only amino acid ester side groups), an increased value of the specific ether carbon groups from PEG confirmed the enrichment of PEG at the surface of PEG-Gal polymers. However, the values were lower than expected. DCA studies showed that the galactose moieties were present at the surface after exposure to an aqueous environment. XPS results confirmed the similarity between experimental and theoretical values for the AH-Gal polymers. This indicated the presence of galactose moieties at the surface, which was confirmed by the DCA data because the contact angles were low compared to those of the other polymers.
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Affiliation(s)
- Mieke Heyde
- Polymer Chemistry and Biomaterials Research Group, Ghent University, 9000 Ghent, Belgium
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Chang CJ, Hsu SH, Yen HJ, Chang H, Hsu SK. Effects of unidirectional permeability in asymmetric poly(DL-lactic acid-co-glycolic acid) conduits on peripheral nerve regeneration: Anin vitro andin vivo study. J Biomed Mater Res B Appl Biomater 2007; 83:206-15. [PMID: 17405166 DOI: 10.1002/jbm.b.30785] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The high outflow permeability of the nerve conduit used to emit the drained waste generated from the traumatized host nerve stump is critical in peripheral nerve regeneration. Our earlier studies have established that asymmetric conduits fulfill the basic requirements for use as nerve guide conduits. In this study, the inflow characteristics of optimal nerve conduits were further examined using in vivo and in vitro trials. Various asymmetric poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits were controlled by modifying precipitation baths using 0, 20, and 95% isopropyl alcohol, with high-porosity (permeability), medium-porosity (high outflow and low inflow), and low-porosity (permeability), respectively. In the in vitro trial, the Schwann cells and fibroblasts were seeded on either side of the asymmetric PLGA films in a newly designed coculture system that simulated the repaired nerve conduit environment. The results of the directional permeable films indicated the statistically significant proliferation of Schwann cells and the inhibition of the division of fibroblasts in lactate dehydrogenase release and inhibition of 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) reduction, compared with the other films. In the in vivo trial, the PLGA conduits seeded with Schwann cells were implanted into 10 mm right sciatic nerve defects in rats. After 6 weeks, implanted conduits were harvested. Histological examination verified that directional permeable conduits had markedly more A-type and B-type myelin fibers in the midconduit and distal nerve. In this work, the directional transport characteristics were established as an extremely important factor to the design and development of optimal nerve guide conduits in peripheral nerve regeneration.
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Affiliation(s)
- Chen-Jung Chang
- Department of Radiological Technology, Central Taiwan University of Science and Technology, Taichung, Taiwan
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In Vitro and In Vivo Characterization of Biodegradable Poly(organophosphazenes) for Biomedical Applications. J Inorg Organomet Polym Mater 2006. [DOI: 10.1007/s10904-006-9071-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
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40
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Nair LS, Laurencin CT. Polymers as biomaterials for tissue engineering and controlled drug delivery. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2006; 102:47-90. [PMID: 17089786 DOI: 10.1007/b137240] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The advent of biodegradable polymers has significantly influenced the development and rapid growth of various technologies in modern medicine. Biodegradable polymers are mainly used where the transient existence of materials is required and they find applications as sutures, scaffolds for tissue regeneration, tissue adhesives, hemostats, and transient barriers for tissue adhesion, as well as drug delivery systems. Each of these applications demands materials with unique physical, chemical, biological, and biomechanical properties to provide efficient therapy. Consequently, a wide range of degradable polymers, both natural and synthetic, have been investigated for these applications. Furthermore, recent advances in molecular and cellular biology, coupled with the development of novel biotechnological drugs, necessitate the modification of existing polymers or synthesis of novel polymers for specific applications. This review highlights various biodegradable polymeric materials currently investigated for use in two key medical applications: drug delivery and tissue engineering.
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Affiliation(s)
- Lakshmi S Nair
- Department of Orthopaedic Surgery, College of Medicine, University of Virginia, Charlottesville 22903, USA
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41
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Greish YE, Bender JD, Lakshmi S, Brown PW, Allcock HR, Laurencin CT. Formation of hydroxyapatite-polyphosphazene polymer composites at physiologic temperature. J Biomed Mater Res A 2006; 77:416-25. [PMID: 16482546 DOI: 10.1002/jbm.a.30145] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Aspects of the formation of bone analog composites at 37 degrees C are described. The composites are composed of hydroxyapatite (HAp) and the calcium salt of a biocompatible polymer and are capable of forming under in vivo conditions. Composite formation involves the formation of monolithic HAp from particulate calcium phosphate precursors while Ca ions liberated to the aqueous medium in which this reaction is occurring form crosslinks with the acidic polymer. The reactants are poly[bis(carboxylatophenoxy)phosphazene] (acid-PCPP), tetracalcium phosphate [Ca4(PO4)2O, TetCP], and anhydrous dicalcium phosphate (CaHPO4, DCPA). The effects of the proportion of polymer (5, 10, or 15 wt %) on the kinetics of HAp formation were studied. Compositional evolution of the solid calcium phosphates present was followed by X-ray diffraction and infrared spectroscopy analyses. HAp formation through a dissolution-precipitation process provided a mildly alkaline medium suitable for deprotonation of the acid-PCPP and for the formation of the calcium crosslinks, as monitored by infrared spectroscopy. Concurrence of crosslinking of the polymer and HAp formation was established, indicating true composite formation can be realized at physiologic temperature.
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Affiliation(s)
- Y E Greish
- Intercollege Materials Research Laboratory, 136 Materials Research Laboratory Building, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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42
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Singh A, Krogman NR, Sethuraman S, Nair LS, Sturgeon JL, Brown PW, Laurencin CT, Allcock HR. Effect of side group chemistry on the properties of biodegradable L-alanine cosubstituted polyphosphazenes. Biomacromolecules 2006; 7:914-8. [PMID: 16529431 DOI: 10.1021/bm050752r] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biodegradable polyphosphazenes have been investigated for a variety of applications, such as controlled drug delivery matrixes, tissue-engineering scaffolds, membranes, and bone-type composites. In this study we have evaluated the effect of side group chemistry on the properties of biodegradable phosphazene polymers that contain ethyl alanato side groups together with ethyl glycinato, p-methylphenoxy, or p-phenylphenoxy side groups. The polymers were synthesized by a macromolecular substitution route. The molecular weights of aryloxy/amino acid ester cosubstituted polymers were much higher than the amino acid ester substituted polyphosphazenes described earlier. Polymer properties, such as glass transition temperature, hydrolytic degradation, surface wettability, tensile strength, and modulus of elasticity varied over a wide range following changes to the type of co-substituents on the polymer backbone. The glass transition temperatures varied from -10 to 35 degrees C and increased with the bulkiness of the side groups. Polymer films in phosphate buffer saline solution showed molecular weight declines ranging from 58% to >80% and mass loss ranging from 4% to 90% over a period of 7 weeks. Water contact angles for polymer films varied from 63 degrees to 107 degrees , with the highest angles for the alanine ethyl ester and p-phenylphenoxy cosubstituted polyphosphazene. The tensile strengths were in the range of 2.4-7.6 MPa and the modulus of elasticity was in the range of 31.4-455.9 MPa. Thus, in this study we have demonstrated the tunability of biodegradable polyphosphazenes to suit a range of biomedical applications.
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Affiliation(s)
- Anurima Singh
- Department of Chemistry and Intercollege Materials Research Laboratory, The Pennsylvania State University, University Park, 16802-6300, USA
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Conconi MT, Lora S, Menti AM, Carampin P, Parnigotto PP. In vitro evaluation of poly[bis(ethyl alanato)phosphazene] as a scaffold for bone tissue engineering. ACTA ACUST UNITED AC 2006; 12:811-9. [PMID: 16674294 DOI: 10.1089/ten.2006.12.811] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Polyphosphazenes with amino acid ester as side groups are biocompatible polymers that could provide valid scaffolds for cell growth. In the present study we investigate the adhesion and growth of osteoblasts obtained from rat bone marrow on matrices composed of thin fibers of poly[bis(ethyl alanato)phosphazene] (PAlaP), poly(d,l-lactic acid) (PDLLA), or PAlaP/PDLLA blend. Our data show that scaffolds of PAlaP or PAlaP/PDLLA blend enhanced the cell adhesion and growth in comparison with that observed in cultures seeded on polystyrene tissue culture plates. Although collagenase-digestible protein synthesis remained unchanged, all scaffolds induced a decrease in alkaline phosphatase activity, suggesting that osteoblasts are in the proliferation phase. Both PAlaP and PAlaP blended with PDLLA may represent a new and interesting substrate for bone tissue engineering.
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Abstract
Nerve regeneration is a complex biological phenomenon. Once the nervous system is impaired, its recovery is difficult and malfunctions in other parts of the body may occur because mature neurons do not undergo cell division. To increase the prospects of axonal regeneration and functional recovery, researches have focused on designing "nerve guidance channels" or "nerve conduits." When developing ideal tissue-engineered nerve conduits, several components come to mind. They include a biodegradable and porous channel wall, the ability to deliver bioactive growth factors, incorporation of support cells, an internal oriented matrix to support cell migration, intraluminal channels to mimic the structure of nerve fascicles, and electrical activities. This article reviews the factors that are critical for nerve repair, and the advanced technologies that are explored to fabricate nerve conduits. To more accurately mimic natural repair in the body, recent studies have focused on the use of various advanced approaches to create ideal nerve conduits that combine multiple stimuli in an effort to better mimic the complex signals normally found in the body.
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Affiliation(s)
- Yi-Cheng Huang
- Institute of Biomedical Engineering, College of Engineering, College of Medicine, National Taiwan University, Taipei, Taiwan.
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Pereira Lopes FR, Camargo de Moura Campos L, Dias Corrêa J, Balduino A, Lora S, Langone F, Borojevic R, Blanco Martinez AM. Bone marrow stromal cells and resorbable collagen guidance tubes enhance sciatic nerve regeneration in mice. Exp Neurol 2006; 198:457-68. [PMID: 16487971 DOI: 10.1016/j.expneurol.2005.12.019] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Revised: 11/23/2005] [Accepted: 12/14/2005] [Indexed: 12/12/2022]
Abstract
We evaluated peripheral nerve regeneration using a tubular nerve guide of resorbable collagen filled with either bone marrow-derived cells (BMDCs) in Dulbecco's cell culture medium (DMEM) or with DMEM alone (control). The control group received just the culture medium (vehicle). The left sciatic nerves of ten isogenic mice were transected and the tubular nerve guides were sutured to the end of the proximal and distal nerve stumps. Motor function was tested at 2, 4 and 6 weeks after surgery using the walking track test. The pawprints were analyzed and the print lengths (PL) were measured to evaluate functional recovery. After 6 weeks, mice were anesthetized, perfused transcardially with fixative containing aldehydes, and the sciatic nerves and tubes were dissected and processed for scanning and transmission electron microscopy. Scanning electron microscopy of the collagen tube revealed that the tube wall became progressively thinner after surgery, proving that the tube can be resorbed in vivo. Quantitative analysis of the regenerating nerves showed that the number of myelinated fibers and the myelin area were significantly increased in the experimental group. Also, motor function recovery was faster in animals that received the cell grafts. These results indicate that the collagen tube filled with BMDCs provided an adequate and favorable environment for the growth and myelination of regenerating axons compared to the collagen tube alone.
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Affiliation(s)
- Fátima Rosalina Pereira Lopes
- Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Brasil
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Barrett EW, Phelps MVB, Silva RJ, Gaumond RP, Allcock HR. Patterning poly(organophosphazenes) for selective cell adhesion applications. Biomacromolecules 2006; 6:1689-97. [PMID: 15877395 DOI: 10.1021/bm049193z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Five polyphosphazenes with different hydrophilicites were synthesized and screened in vitro. The purpose was to identify unique types of polymeric substrates that distinctly favored or markedly prevented cellular adhesion. The SK-N-BE(2c) human neuroblastoma cell line, utilized for its electrogenic responses, was used to test this differential adhesion. In particular, the objective was to specifically culture this cell line in a highly selective pattern. Each candidate polymer was cast into films and plated with neuroblastoma cells for 3 days. The polyphosphazene materials which showed negative cellular adhesive properties (-CAPs) were poly[bis(trifluoroethoxy)phosphazene] (TFE) and poly[bis(methoxyethoxyethoxy)phosphazene] (MEEP). The polyphosphazenes which showed positive cellular adhesive properties (+CAPs) were poly[(methoxyethoxyethoxy)(1.0)(carboxylatophenoxy)(1.0)phosphazene] (PMCPP), poly[(methoxyethoxyethoxy)(1.0)(cinnamyloxy)(1.0)phosphazene] (PMCP), and poly[(methoxyethoxyethoxy)(1.0)(p-methylphenoxy)(1.0)phosphazene] (PMMP). To test cellular selectivity, films of -CAP and +CAP were copatterned onto glass substrates. The micropatterned films were plated with SK-N-BE(2c) neuroblastoma cells for one week. The results showed that neuroblastoma cells adhere selectively (over 60%) to the +CAP microfeatures. We also showed that multiple properties can be achieved with a single material and that we can use TFE as both a -CAP and an insulation layer and PMCP as a conductive +CAP layer.
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Affiliation(s)
- Eric W Barrett
- Department of Chemistry, 104 Chemistry Building, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Desouches C, Alluin O, Mutaftschiev N, Dousset E, Magalon G, Boucraut J, Feron F, Decherchi P. La réparation nerveuse périphérique : 30 siècles de recherche. Rev Neurol (Paris) 2005; 161:1045-59. [PMID: 16288170 DOI: 10.1016/s0035-3787(05)85172-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Nerve injury compromises sensory and motor functions. Techniques of peripheral nerve repair are based on our knowledge regarding regeneration. Microsurgical techniques introduced in the late 1950s and widely developed for the past 20 years have improved repairs. However, functional recovery following a peripheral mixed nerve injury is still incomplete. STATE OF ART Good motor and sensory function after nerve injury depends on the reinnervation of the motor end plates and sensory receptors. Nerve regeneration does not begin if the cell body has not survived the initial injury or if it is unable to initiate regeneration. The regenerated axons must reach and reinnervate the appropriate target end-organs in a timely fashion. Recovery of motor function requires a critical number of motor axons reinnervating the muscle fibers. Sensory recovery is possible if the delay in reinnervation is short. Many additional factors influence the success of nerve repair or reconstruction. The timing of the repair, the level of injury, the extent of the zone of injury, the technical skill of the surgeon, and the method of repair and reconstruction contribute to the functional outcome after nerve injury. CONCLUSION This review presents the recent advances in understanding of neural regeneration and their application to the management of primary repairs and nerve gaps.
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Affiliation(s)
- C Desouches
- Service de Chirurgie de la Main, Chirurgie Plastique et Réparatrice des Membres, Assistance Publique, Hôpitaux de Marseille, Hôpital de la Conception, Marseille
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Greish YE, Bender JD, Lakshmi S, Brown PW, Allcock HR, Laurencin CT. Composite formation from hydroxyapatite with sodium and potassium salts of polyphosphazene. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2005; 16:613-20. [PMID: 15965592 DOI: 10.1007/s10856-005-2531-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2003] [Accepted: 05/20/2004] [Indexed: 05/03/2023]
Abstract
The low temperature synthesis of composites potentially suitable as bone substitutes which form in vivo, was investigated. The composites were comprised of stoichiometric hydroxyapatite (SHAp) and water-soluble poly phosphazenes. These constituents were selected because of their biocompatibility, and were mixed as powders with a phosphate buffer solution (PBS) to form the composites. The effects of poly[bis(sodium carboxylatophenoxy)phosphazene] (Na-PCPP) or poly[bis(potassium carboxylatophenoxy) phosphazene] (K-PCPP) on stoichiometric hydroxyapatite (SHAp) formation from tetracalcium phosphate and anhydrous dicalcium phosphate were assessed. The kinetics and reaction chemistries of composite formation were followed by isothermal calorimetry, X-ray diffraction, infrared spectroscopy and scanning electron microscopy. In the presence of 1% by weight of polyphosphazenes, composites comprised of SHAp and calcium cross-linked polymer salts were formed. Thus a mechanism for binding between polymer chains was established. Elevated proportions (5 and 10% by weight) of polyphosphazene, however, resulted in the inhibition of SHAp formation. This is attributed to the formation of viscous polymer solution coatings on the calcium phosphate precursors, retarding their reaction, and consequently inhibiting SHAp formation.
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Affiliation(s)
- Y E Greish
- Intercollege Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
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Conconi MT, Lora S, Baiguera S, Boscolo E, Folin M, Scienza R, Rebuffat P, Parnigotto PP, Nussdorfer GG. In vitro culture of rat neuromicrovascular endothelial cells on polymeric scaffolds. J Biomed Mater Res A 2005; 71:669-74. [PMID: 15499589 DOI: 10.1002/jbm.a.30198] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Polyphosphazenes are polymers possessing a skeleton composed of alternating phosphorous and nitrogen atoms, and two side-moieties linked to each phosphorous atom. Polyphosphazenes with amino acid esters as side-moieties are biocompatible and biodegradable polymers. Two polyphosphazenes, poly[bis(ethyl alanate) phosphazene] and poly[(ethyl phenylalanate)0.8(ethyl alanate)0.8(ethyl glycinate)0.4 phosphazene] (PPAGP) were synthesized, and processed to form small fibers. Their ability to support rat neuromicrovascular endothelial cell (EC) adhesion and growth has been studied, using poly(D,L-lactic acid) as reference compound. Scanning electron microscopy revealed that both poly[bis(ethyl alanate) phosphazene] and PPAGP fibers were thinner than poly(D,L-lactic acid) fibers, and possessed a more irregular and porous surface. All polymers increased EC adhesion, compared with polystyrene, but only polyphosphazenes were able to improve EC growth. The highest increase in EC proliferation was induced by PPAGP, which, as revealed by environmental scanning electron microscopy, was also able to induce ECs to arrange into tubular structures. The conclusion is drawn that PPAGP may provide the best scaffold for engineered blood vessels, because it promotes adhesion, growth, and organization of ECs into capillary-like structures.
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Prinz RAD, Nakamura-Pereira M, De-Ary-Pires B, Fernandes D, Fabião-Gomes BDSV, Martinez AMB, de Ary-Pires R, Pires-Neto MA. Axonal and extracellular matrix responses to experimental chronic nerve entrapment. Brain Res 2005; 1044:164-75. [PMID: 15885215 DOI: 10.1016/j.brainres.2005.02.085] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 02/21/2005] [Accepted: 02/23/2005] [Indexed: 11/15/2022]
Abstract
We have analyzed the ultrastructural and histopathological changes that occur during experimental chronic nerve entrapment, as well as the immunohistochemical expression of chondroitin sulfate proteoglycan (CSPG). Adult hamsters (n = 30) were anesthetized and received a cuff around the right sciatic nerve. Animals survived for varying times (5 to 15 weeks) being thereafter perfused transcardially with fixative solutions either for immunohistochemical or electron microscopic procedures. Experimental nerves were dissected based upon the site of compression (proximal, entrapment and distal). CSPG overexpression was detected in the compressed nerve segment and associated with an increase in perineurial and endoneurial cells. Ultrastructural changes and data from semithin sections were analyzed both in control and compressed nerves. We have observed endoneurial edema, perineurial and endoneurial thickening, and whorled cell-sparse pathological structures (Renaut bodies) in the compressed nerves. Morphometrical analyses of myelinated axons at the compression sites revealed: (a) a reduction both in axon sectional area (up to 30%) and in myelin sectional area (up to 80%); (b) an increase in number of small axons (up to 60%) comparatively to the control group. Distal segment of compressed nerves presented: (a) a reduction in axon sectional area (up to 60%) and in myelin sectional area (up to 90%); (b) a decrease in axon number (up to 40%) comparatively to the control data. In conclusion, we have shown that nerve entrapment is associated with a local intraneural increase in CSPG expression, segmental demyelination, perineurial and endoneurial fibrosis, and other histopathological findings.
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Affiliation(s)
- Rafael Augusto Dantas Prinz
- Departamento de Anatomia, Universidade Federal do Rio de Janeiro, CCS, Bloco F, Cidade Universitária, 21941-590, Rio de Janeiro, Brazil
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