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1.
Drug Deliv Transl Res ; 5(2): 125-36, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25787738

RESUMO

Biofunctionalized polyethylene glycol maleimide (PEG-MAL) hydrogels were engineered as a platform to deliver pancreatic islets to the small bowel mesentery and promote graft vascularization. VEGF, a potent stimulator of angiogenesis, was incorporated into the hydrogel to be released in an on-demand manner through enzymatic degradation. PEG-MAL hydrogel enabled extended in vivo release of VEGF. Isolated rat islets encapsulated in PEG-MAL hydrogels remained viable in culture and secreted insulin. Islets encapsulated in PEG-MAL matrix and transplanted to the small bowel mesentery of healthy rats grafted to the host tissue and revascularized by 4 weeks. Addition of VEGF release to the PEG-MAL matrix greatly augmented the vascularization response. These results establish PEG-MAL engineered matrices as a vascular-inductive cell delivery vehicle and warrant their further investigation as islet transplantation vehicles in diabetic animal models.


Assuntos
Hidrogéis/administração & dosagem , Ilhotas Pancreáticas/efeitos dos fármacos , Maleimidas/química , Polietilenoglicóis/química , Fator A de Crescimento do Endotélio Vascular/administração & dosagem , Alginatos/química , Animais , Colágeno/química , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Hidrogéis/química , Intestino Delgado/irrigação sanguínea , Intestino Delgado/efeitos dos fármacos , Intestino Delgado/fisiologia , Ilhotas Pancreáticas/irrigação sanguínea , Ilhotas Pancreáticas/fisiologia , Transplante das Ilhotas Pancreáticas , Masculino , Mesentério/efeitos dos fármacos , Mesentério/fisiologia , Neovascularização Fisiológica/efeitos dos fármacos , Ratos Endogâmicos Lew , Fator A de Crescimento do Endotélio Vascular/química
2.
Biomaterials ; 44: 55-70, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25617126

RESUMO

Neural electrodes are an important part of brain-machine interface devices that can restore functionality to patients with sensory and movement disorders. Chronically implanted neural electrodes induce an unfavorable tissue response which includes inflammation, scar formation, and neuronal cell death, eventually causing loss of electrode function. We developed a poly(ethylene glycol) hydrogel coating for neural electrodes with non-fouling characteristics, incorporated an anti-inflammatory agent, and engineered a stimulus-responsive degradable portion for on-demand release of the anti-inflammatory agent in response to inflammatory stimuli. This coating reduces in vitro glial cell adhesion, cell spreading, and cytokine release compared to uncoated controls. We also analyzed the in vivo tissue response using immunohistochemistry and microarray qRT-PCR. Although no differences were observed among coated and uncoated electrodes for inflammatory cell markers, lower IgG penetration into the tissue around PEG+IL-1Ra coated electrodes indicates an improvement in blood-brain barrier integrity. Gene expression analysis showed higher expression of IL-6 and MMP-2 around PEG+IL-1Ra samples, as well as an increase in CNTF expression, an important marker for neuronal survival. Importantly, increased neuronal survival around coated electrodes compared to uncoated controls was observed. Collectively, these results indicate promising findings for an engineered coating to increase neuronal survival and improve tissue response around implanted neural electrodes.


Assuntos
Materiais Revestidos Biocompatíveis/farmacologia , Eletrodos Implantados , Proteína Antagonista do Receptor de Interleucina 1/metabolismo , Maleimidas/farmacologia , Neurônios/efeitos dos fármacos , Peptídeo Hidrolases/metabolismo , Polietilenoglicóis/farmacologia , Sequência de Aminoácidos , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/patologia , Barreira Hematoencefálica/efeitos dos fármacos , Barreira Hematoencefálica/patologia , Adesão Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Sulfatos de Condroitina/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Proteína Glial Fibrilar Ácida/metabolismo , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Imunoglobulina G/metabolismo , Mediadores da Inflamação/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , Microglia/efeitos dos fármacos , Dados de Sequência Molecular , Polietilenoglicóis/química , Ratos Sprague-Dawley , Propriedades de Superfície
3.
J Biomed Mater Res A ; 102(5): 1486-99, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-23666919

RESUMO

The performance of neural electrodes implanted in the brain is often limited by host response in the surrounding brain tissue, including astrocytic scar formation, neuronal cell death, and inflammation around the implant. We applied conformal microgel coatings to silicon neural electrodes and examined host responses to microgel-coated and uncoated electrodes following implantation in the rat brain. In vitro analyses demonstrated significantly reduced astrocyte and microglia adhesion to microgel-coated electrodes compared to uncoated controls. Microgel-coated and uncoated electrodes were implanted in the rat brain cortex and the extent of activated microglia and astrocytes as well as neuron density around the implant were evaluated at 1, 4, and 24 weeks postimplantation. Microgel coatings reduced astrocytic recruitment around the implant at later time points. However, microglial response indicated persistence of inflammation in the area around the electrode. Neuronal density around the implanted electrodes was also lower for both implant groups compared to the uninjured control. These results demonstrate that microgel coatings do not significantly improve host responses to implanted neural electrodes and underscore the need for further improvements in implantable materials.


Assuntos
Encéfalo/fisiologia , Materiais Revestidos Biocompatíveis/farmacologia , Eletrodos Implantados , Géis/farmacologia , Neurônios/fisiologia , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação Mielomonocítica/metabolismo , Encéfalo/efeitos dos fármacos , Antígeno CD11b/metabolismo , Adesão Celular/efeitos dos fármacos , Proteína Glial Fibrilar Ácida/metabolismo , Imuno-Histoquímica , Neuroglia/citologia , Neurônios/efeitos dos fármacos , Ratos
4.
Biomaterials ; 32(31): 7785-92, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21813173

RESUMO

Implant-associated inflammation is a major cause for the reduced performance/lifetime and failure of numerous medical devices. Therefore, the ability to non-invasively and quantitatively monitor implant-associated inflammation is critically important. Here we show that implant-associated inflammation can be imaged via fluorescence imaging using near-infrared hydrocyanine dyes delivered either locally or intravenously in living mice. This imaging strategy allowed quantitative longitudinal monitoring of inflammation by detecting reactive oxygen species (ROS) released by inflammatory cells in response to implanted poly(ethylene terephthalate) (PET) disks or injected poly (lactic-co-glycolic acid) (PLGA) microparticles, and exhibited a strong correlation to conventional analysis of inflammation. Furthermore, modulation of inflammatory responses via controlled release of the anti-inflammatory agent dexamethasone was detected using this sensitive imaging approach. Thus, hydrocyanine-based fluorescence imaging of ROS could serve as a surrogate measure for monitoring implant-associated inflammation as well as evaluating the efficacy of therapeutic approaches to modulate host responses to implanted medical devices.


Assuntos
Materiais Biocompatíveis/efeitos adversos , Imageamento Tridimensional/métodos , Inflamação/etiologia , Inflamação/patologia , Animais , Dexametasona/farmacologia , Fluorescência , Imuno-Histoquímica , Implantes Experimentais/efeitos adversos , Verde de Indocianina/administração & dosagem , Verde de Indocianina/farmacologia , Ácido Láctico/farmacologia , Macrófagos/efeitos dos fármacos , Camundongos , Microesferas , Neutrófilos/efeitos dos fármacos , Ácido Poliglicólico/farmacologia , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Espécies Reativas de Oxigênio/metabolismo , Espectroscopia de Luz Próxima ao Infravermelho
5.
Sci Transl Med ; 2(45): 45ra60, 2010 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-20720217

RESUMO

Engineered biointerfaces covered with biomimetic motifs, including short bioadhesive ligands, are a promising material-based strategy for tissue repair in regenerative medicine. Potentially useful coating molecules are ligands for the integrins, major extracellular matrix receptors that require both ligand binding and nanoscale clustering for maximal signaling efficiency. We prepared coatings consisting of well-defined multimer constructs with a precise number of recombinant fragments of fibronectin (monomer, dimer, tetramer, and pentamer) to assess how nanoscale ligand clustering affects integrin binding, stem cell responses, tissue healing, and biomaterial integration. Clinical-grade titanium was grafted with polymer brushes that presented monomers, dimers, trimers, or pentamers of the alpha(5)beta(1) integrin-specific fibronectin III (7 to 10) domain (FNIII(7-10)). Coatings consisting of trimers and pentamers enhanced integrin-mediated adhesion in vitro, osteogenic signaling, and differentiation in human mesenchymal stem cells more than did surfaces presenting monomers and dimers. Furthermore, ligand clustering promoted bone formation and functional integration of the implant into bone in rat tibiae. This study establishes that a material-based strategy in which implants are coated with clustered bioadhesive ligands can promote robust implant-tissue integration.


Assuntos
Materiais Biocompatíveis/farmacologia , Fibronectinas/metabolismo , Receptores de Vitronectina/metabolismo , Cicatrização/efeitos dos fármacos , Animais , Sítios de Ligação , Fibronectinas/química , Humanos , Implantes Experimentais , Ligantes , Masculino , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Células-Tronco Mesenquimais/metabolismo , Nanoestruturas/química , Osseointegração/efeitos dos fármacos , Estrutura Terciária de Proteína , Ratos , Ratos Sprague-Dawley , Receptores de Vitronectina/química , Especificidade por Substrato
6.
Tissue Eng Part A ; 16(9): 2795-808, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20412027

RESUMO

The repair of large nonunions in long bones remains a significant clinical problem due to high failure rates and limited tissue availability for auto- and allografts. Many cell-based strategies for healing bone defects deliver bone marrow stromal cells (BMSCs) to the defect site to take advantage of the inherent osteogenic capacity of this cell type. However, many factors, including donor age and ex vivo expansion of the cells, cause BMSCs to lose their differentiation ability. To overcome these limitations, we have genetically engineered BMSCs to constitutively overexpress the osteoblast-specific transcription factor Runx2. In the present study, we examined Runx2-modified BMSCs, delivered via polycaprolactone scaffolds loaded with type I collagen meshes, in critical-sized segmental defects in rats compared to unmodified cells, cell-free scaffolds, and empty defects. Runx2 expression in BMSCs accelerated healing of critical-sized defects compared to unmodified BMSCs and defects receiving cell-free treatments. These findings provide an accelerated method for healing large bone defects, which may reduce recovery time and the need for external fixation of critical-sized defects.


Assuntos
Células da Medula Óssea/citologia , Células da Medula Óssea/metabolismo , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Fêmur/patologia , Engenharia Genética/métodos , Osteogênese/fisiologia , Células Estromais/citologia , Animais , Sobrevivência Celular/genética , Sobrevivência Celular/fisiologia , Células Cultivadas , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Feminino , Fêmur/cirurgia , Citometria de Fluxo , Masculino , Osteogênese/genética , Poliésteres/química , Ratos , Espectroscopia de Infravermelho com Transformada de Fourier , Alicerces Teciduais/química , Microtomografia por Raio-X
7.
J Biomed Mater Res A ; 94(1): 252-8, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20166218

RESUMO

Inflammatory responses to implanted biomedical devices elicit a foreign body fibrotic reaction that limits device integration and performance in various biomedical applications. We examined chronic inflammatory responses to microgel conformal coatings consisting of thin films of poly(N-isopropylacrylamide) hydrogel microparticles cross-linked with poly(ethylene glycol) diacrylate deposited on poly(ethylene terephthalate) (PET). Unmodified and microgel-coated PET disks were implanted subcutaneously in rats for 4 weeks and explants were analyzed by histology and immunohistochemistry. Microgel coatings reduced chronic inflammation and resulted in a more mature/organized fibrous capsule. Microgel-coated samples exhibited 22% thinner fibrous capsules that contained 40% fewer cells compared to unmodified PET disks. Furthermore, microgel-coated samples contained significantly higher levels of macrophages (80%) than unmodified PET controls. These results demonstrate that microgel coatings reduce chronic inflammation to implanted biomaterials. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.


Assuntos
Materiais Revestidos Biocompatíveis/metabolismo , Hidrogéis/metabolismo , Implantes Experimentais , Acrilamidas/química , Acrilamidas/imunologia , Resinas Acrílicas , Animais , Materiais Revestidos Biocompatíveis/química , Reação a Corpo Estranho/imunologia , Reação a Corpo Estranho/patologia , Hidrogéis/química , Implantes Experimentais/efeitos adversos , Inflamação , Masculino , Teste de Materiais , Polímeros/química , Ratos , Ratos Wistar
8.
Biomaterials ; 31(9): 2574-82, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20056517

RESUMO

Healing large bone defects and non-unions remains a significant clinical problem. Current treatments, consisting of auto and allografts, are limited by donor supply and morbidity, insufficient bioactivity and risk of infection. Biotherapeutics, including cells, genes and proteins, represent promising alternative therapies, but these strategies are limited by technical roadblocks to biotherapeutic delivery, cell sourcing, high cost, and regulatory hurdles. In the present study, the collagen-mimetic peptide, GFOGER, was used to coat synthetic PCL scaffolds to promote bone formation in critically-sized segmental defects in rats. GFOGER is a synthetic triple helical peptide that binds to the alpha(2)beta(1) integrin receptor involved in osteogenesis. GFOGER coatings passively adsorbed onto polymeric scaffolds, in the absence of exogenous cells or growth factors, significantly accelerated and increased bone formation in non-healing femoral defects compared to uncoated scaffolds and empty defects. Despite differences in bone volume, no differences in torsional strength were detected after 12 weeks, indicating that bone mass but not bone quality was improved in this model. This work demonstrates a simple, cell/growth factor-free strategy to promote bone formation in challenging, non-healing bone defects. This biomaterial coating strategy represents a cost-effective and facile approach, translatable into a robust clinical therapy for musculoskeletal applications.


Assuntos
Materiais Biomiméticos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Colágeno/farmacologia , Fêmur/patologia , Peptídeos/farmacologia , Alicerces Teciduais/química , Cicatrização/efeitos dos fármacos , Adsorção/efeitos dos fármacos , Sequência de Aminoácidos , Animais , Fêmur/efeitos dos fármacos , Fêmur/cirurgia , Fenômenos Mecânicos/efeitos dos fármacos , Modelos Moleculares , Dados de Sequência Molecular , Osteogênese/efeitos dos fármacos , Peptídeos/química , Poliésteres/farmacologia , Ratos , Ratos Endogâmicos Lew , Microtomografia por Raio-X
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