Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Biomed Res Int ; 2022: 7799812, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35480141

RESUMO

Brain cancer is one of the cell synthesis diseases. Brain cancer cells are analyzed for patient diagnosis. Due to this composite cell, the conceptual classifications differ from each and every brain cancer investigation. In the gene test, patient prognosis is identified based on individual biocell appearance. Classification of advanced artificial neural network subtypes attains improved performance compared to previous enhanced artificial neural network (EANN) biocell subtype investigation. In this research, the proposed features are selected based on improved gene expression programming (IGEP) with modified brute force algorithm. Then, the maximum and minimum term survivals are classified by using PCA with enhanced artificial neural network (EANN). In this, the improved gene expression programming (IGEP) effectual features are selected by using remainder performance to improve the prognosis efficiency. This system is estimated by using the Cancer Genome Atlas (CGA) dataset. Simulation outputs present improved gene expression programming (IGEP) with modified brute force algorithm which achieves accurate efficiency of 96.37%, specificity of 96.37%, sensitivity of 98.37%, precision of 78.78%, F-measure of 80.22%, and recall of 64.29% when compared to generalized regression neural network (GRNN), improved extreme learning machine (IELM) with minimum redundancy maximum relevance (MRMR) method, and support vector machine (SVM).


Assuntos
Neoplasias Encefálicas , Redes Neurais de Computação , Algoritmos , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/genética , Simulação por Computador , Humanos , Máquina de Vetores de Suporte
2.
Mater Sci Eng C Mater Biol Appl ; 99: 357-366, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30889709

RESUMO

Silver nanoparticles loaded fibrillar collagen-chitosan matrix (CC) was prepared by biomimetic approach by blending silver nanoparticles (tAgNPs), collagen fibril and chitosan hydrogel followed by cross-linking and biomineralization. Electron micrograph showed that the surface of the composites exhibited native fibrillar morphology of collagen and their cross-section revealed layer-like arrangement of native fibrillar collagen. The mineralized composites exhibited surface mineralization of calcium phosphates incorporated with magnesium. FT-IR ATR analysis revealed the uniform blending of collagen and chitosan without any chemical interaction between them. XRD analysis showed incorporation of silver nanoparticles and lamellar structure of collagen and chitosan. The mechanical property of the dry composite film showed increase in tensile strength with the addition of chitosan and raised to 4.6 fold in M-CC4 composite. The incorporation of chitosan in M-CC3 led to 2.2 fold increase in mineralization as confirmed by the TGA analysis. Contact angle analysis revealed the hydrophilic nature of the composite. Hemolysis analysis of the composites verified the hemocompatible nature of composites with hemolysis < 5%. MTT assay for the composites was carried by seeding MG-63 cells and indicated cell viability > 80%. Antibacterial activity analysis showed the percent growth inhibition of about 27% and 37% for S. aureus and E. coli respectively. The prepared composite would possess silver nanoparticles loaded collagen fibril in the native state and the formed biomineral will be similar to the bone mineral. Hence the fabricated composite -could be used as a biomaterial for bone tissue engineering applications.


Assuntos
Biomimética/métodos , Quitosana/farmacologia , Colágenos Fibrilares/farmacologia , Minerais/química , Prata/farmacologia , Animais , Antibacterianos/farmacologia , Adesão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Contagem de Colônia Microbiana , Escherichia coli/efeitos dos fármacos , Cabras , Hemólise/efeitos dos fármacos , Humanos , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Staphylococcus aureus/efeitos dos fármacos , Termogravimetria , Difração de Raios X
3.
Ann Med Surg (Lond) ; 4(4): 388-94, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26594357

RESUMO

BACKGROUND: Abdominal wall defects and hernias are commonly repaired with synthetic or biological materials. Adhesions and recurrences are a common problem. A study was conducted to compare Chitosan coated polypropylene mesh and a polypropylene-polydioxanone composite with oxidized cellulose coating mesh (Proceed™) in repair of abdominal wall defect in a Rabbit hernia model. METHODS: A randomized controlled experimental study was done on twelve New Zealand white rabbits. A ventral abdominal defect was created in each of the rabbits. The rabbits were divided into two groups. In one group the defect was repaired with Chitosan coated polypropylene mesh and Proceed mesh™ in the other. The rabbits were operated in two phases. They were followed up at four weeks and twelve weeks respectively after which the rabbits were sacrificed. They were evaluated by open exploration and histopathological examination. Their efficacy in reducing adhesion and ability of remodeling and tissue integration were studied. RESULTS: There was no statistical significance in the area of adhesion, the force required to remove the adhesions, tissue integration and remodeling between Chitosan and Proceed™ group. Histological analysis revealed that the inflammatory response, fibrosis, material degradation and remodeling were similar in both the groups. There were no hernias, wound infection or dehiscence in any of the studied animals. CONCLUSION: Chitosan coated polypropylene mesh was found to have similar efficacy to Proceed™ mesh. Chitosan coated polypropylene mesh, can act as an anti adhesive barrier when used in the repair of incisional hernias and abdominal wall defects.

4.
Aliment Pharmacol Ther ; 42(11-12): 1271-80, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26510540

RESUMO

BACKGROUND: Infection is the most common cause of mortality in end-stage liver disease (ESLD). The impact of obesity on infection risk in ESLD is not established. AIM: To characterise the impact of obesity on infection risk in ESLD. METHODS: We evaluated the association between infection and obesity in patients with ESLD. Patients grouped as non-obese, obesity class I-II and obesity class III were studied using the Nationwide Inpatient Sample. Validated diagnostic code based algorithms were utilised to determine weight category and infections, including bacteraemia, skin/soft tissue infection, urinary tract infection (UTI), pneumonia/respiratory infection, Clostridium difficile infection (CDI) and spontaneous bacterial peritonitis (SBP). Risk factors for infection and mortality were assessed using multivariable logistic regression analysis. RESULTS: Of 115 465 patients identified, 100 957 (87.5%) were non-obese and 14 508 (12.5%) were obese, with 9489 (8.2%) as obesity class I-II and 5019 (4.3%) as obesity class III. 37 117 patients (32.1%) had an infection diagnosis. Infection was most prevalent among obesity class III (44.0%), followed by obesity class I-II (38.9%) and then non-obese (31.9%). In multivariable modelling, class III obesity (OR = 1.41; 95% CI 1.32-1.51; P < 0.001), and class I-II obesity (OR = 1.08; 95% CI 1.01-1.15; P = 0.026) were associated with infection. Compared to non-obese patients, obese individuals had greater prevalence of bacteraemia, UTI, and skin/soft tissue infection as compared to non-obese patients. CONCLUSIONS: Obesity is newly identified to be independently associated with infection in end-stage liver disease. The distribution of infection sites varies based on weight category.


Assuntos
Infecções Bacterianas/epidemiologia , Doença Hepática Terminal/complicações , Obesidade/complicações , Idoso , Infecções por Clostridium/epidemiologia , Bases de Dados Factuais , Feminino , Humanos , Pacientes Internados , Masculino , Pessoa de Meia-Idade , Pneumonia/epidemiologia , Prevalência , Fatores de Risco
5.
Biometals ; 28(1): 21-33, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25326906

RESUMO

Environmental exposure of Cr(VI) and Ni(II) due to rapid industrialization causes adverse effects in living tissues. Small quantities of these ions also find their way into tissues when metal alloys are used as implants. Even though considerable research has been done on the effects due to their exposure in animal cells, there are only very few reports on how they can affect stem cells which have been shown to be found in adult tissues as well, albeit in small quantities. Hence this study was aimed at understanding how Cr(VI) and Ni(II) affect human adipose derived stem cells (hADSCs) in a cell culture environment. Our results indicate that both ions induce apoptosis in a concentration and time dependent manner with loss of mitochondrial membrane potential (MMP) and corresponding increase in caspase-3 activity. With regard to Ni(II), apoptosis seems to occur only in a small percentage of cells while necrosis is predominant. It can be inferred that the long term exposure of these metals may cause adverse effects in stem cell proliferation and differentiation.


Assuntos
Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Cromo/farmacologia , Níquel/farmacologia , Caspase 3/metabolismo , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Humanos , Células-Tronco/efeitos dos fármacos
6.
Mater Sci Eng C Mater Biol Appl ; 47: 222-9, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25492192

RESUMO

Biodegradable, antimicrobial composite of various silver ion concentrations was synthesized using zeta potential and isoelectric point measurements, for a controlled release of silver ions, and in addition to assess the effect of protein adsorption with the increase of the silver ion concentration. The interaction between hydroxyapatite (HAp) and silver incorporated hydroxyapatite (AgHAp) with gelatin was increased by optimally adjusting the zeta potential and isoelectric point of the ceramic (HAp and AgHAp), and bio-polymer individually. The electrostatic interactions between the ceramic and biopolymer were confirmed, through shifts in N-H stretching, decrease in the swelling ratio, and increase in the degradation temperature observed by the derivative thermo-gravimetric analysis (DTG). These results substantiate that, the zeta potential is a novel tool to increase the ceramic-biopolymer interaction. Increasing electrostatic interaction between the biopolymer and ceramic, decreases the release of silver ions in the simulated body fluid, due to the controlled degradation of the biopolymer. The isoelectric point decreases with the increase of the silver ion concentration, which evidenced the change in the net surface charge. With the increase of the silver ion concentration, the protein adsorption decreases due to an increase in hydrophilic character of the composite. This study examines the minimum concentration of silver ion essential for maximum protein adsorption, antimicrobial and hemocompatibility. This study provides a novel route to control the release of silver ions by enhancing the ceramic-polymer interaction and estimate the silver ion concentration suitable for protein adsorption. The prepared composite is nontoxic, degradable, and antimicrobial, with the controlled release of silver ions in the simulated body fluid.


Assuntos
Materiais Biocompatíveis/química , Íons/química , Compostos de Prata/química , Prata/química , Adsorção , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Materiais Biocompatíveis/farmacologia , Líquidos Corporais/efeitos dos fármacos , Cerâmica/química , Cerâmica/farmacologia , Durapatita/química , Durapatita/farmacologia , Gelatina/química , Bactérias Gram-Negativas/efeitos dos fármacos , Humanos , Íons/farmacologia , Teste de Materiais/métodos , Polímeros/química , Prata/farmacologia , Compostos de Prata/farmacologia , Eletricidade Estática , Temperatura
7.
Colloids Surf B Biointerfaces ; 90: 83-90, 2012 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-22019452

RESUMO

This paper reports the effect of L-lysine on the conformational, rheological, and thermal properties of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross linked collagen and investigates the influence of l-lysine on the self assembly processes of collagen. In the absence of L-lysine, the rheological characterization of collagen cross linked with EDC/NHS showed an increase in shearing stress with shearing speed indicating that the collagen chains become rigid and the molecules are reluctant to flow. On the other hand, the increase in shearing stress with shearing speed is comparatively much less in the presence of L-lysine indicating a greater flexibility of the collagen molecules. The self assembly processes of collagen treated with EDC/NHS in the absence and presence of L-lysine were characterized using powder XRD, FT-IR, polarizing optical microscopy and kinetic studies. XRD studies show an increase in peak intensity and sharpness in the presence of L-lysine indicating the enhancement of crystallinity of collagen nano-fibrils. FT-IR results suggest that the incorporation of L-lysine in the EDC/NHS cross linking favors the molecular stability of collagen. From the present study, it is possible to conclude that the pre-treatment of collagen with L-lysine enhances EDC/NHS cross linking and can be used for biomaterial applications.


Assuntos
Materiais Biocompatíveis/química , Colágeno/química , Lisina/química , Engenharia Tecidual/métodos , Alicerces Teciduais , Animais , Materiais Biocompatíveis/metabolismo , Reagentes de Ligações Cruzadas/química , Etildimetilaminopropil Carbodi-Imida/química , Matriz Extracelular/química , Humanos , Cinética , Teste de Materiais , Maleabilidade , Ratos , Reologia , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Succinimidas/química , Difração de Raios X
8.
J Biomed Nanotechnol ; 7(1): 56, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21485801

RESUMO

The use of nano-particles in several areas necessitates the understanding of their interaction with cells, tissues and experimental animals. In the present study, the effect of a curcumin conjugated gold nano-particle on peripheral blood lymphocytes was investigated. The treated lymphocytes revealed features typical of apoptosis which include chromatin condensation, and membrane blebbing and occurrence of apoptotic bodies. The observations indicate that these nanoparticle conjugates may find use as drugs in non-toxic range observed in cytotoxicity studies.


Assuntos
Curcumina/administração & dosagem , Ouro/efeitos adversos , Leucócitos Mononucleares/citologia , Leucócitos Mononucleares/efeitos dos fármacos , Nanocápsulas/efeitos adversos , Nanocápsulas/química , Nanopartículas/efeitos adversos , Anti-Inflamatórios não Esteroides/administração & dosagem , Anti-Inflamatórios não Esteroides/efeitos adversos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Curcumina/química , Relação Dose-Resposta a Droga , Ouro/química , Humanos , Nanopartículas/química
9.
Int J Biol Macromol ; 47(3): 402-9, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20600266

RESUMO

Non-enzymatic glycation of collagen has been used in modern biomaterials science. This paper deals with in vitro studies on the effects of amino guanidine (AG) and aspirin in the non-enzymatic glycation (NEG) of collagen using thermal, conformational, fluorescence, turbidity and powder XRD measurements. There is no significant change in the fluorescence emission spectra for different concentrations of AG treated NEG of collagen whereas the emission intensity decreases as the concentration of aspirin increases. Circular dichroism (CD) revealed the disappearance of the positive peak at 220nm for glycated collagen in the presence of amino guanidine and aspirin suggesting the collapse of triple helical configuration. Nearly 15 degrees C decrease is observed in shrinkage temperature of glycated rat tail tendon (RTT) collagen fibres in the presence of aspirin. Powder XRD of glycated collagen nano-fibrils in the presence of amino guanidine reveals high crystalline nature and the enhancement of self assembly processes when compared to aspirin. To the best of our knowledge, this is the first report of powder XRD of the self assembly of collagen nano-fibrils without mineralization. Our experimental results suggest that in the non-enzymatic glycation of collagen both AG and aspirin play a pivotal role in the aggregation and self assembly processes. From the present study, it is possible to conclude that while AG significantly influences the self assembly processes, aspirin facilitates the aggregation processes.


Assuntos
Aspirina/farmacologia , Colágeno/metabolismo , Guanidinas/farmacologia , Absorção , Animais , Varredura Diferencial de Calorimetria , Dicroísmo Circular , Colágeno/química , Glicosilação/efeitos dos fármacos , Nefelometria e Turbidimetria , Conformação Proteica , Ratos , Espectrometria de Fluorescência , Temperatura , Viscosidade , Difração de Raios X
10.
J Photochem Photobiol B ; 97(1): 34-9, 2009 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-19716709

RESUMO

Many cross-linking agents for collagen are available with varying levels of toxicity and some are in use in biomedical implants of collagen. L-DOPA (3,4-dihydroxyphenylalanine), a neurotransmitter, is a naturally present compound in the living system and is the target in therapeutic strategy of Parkinson's disease. This work reports the effect of the neurotransmitter DOPA on the stability of collagen solution using circular dichroism (CD), fluorescence spectroscopy, melting and shrinkage temperature. Collagen solution treated with various concentrations of DOPA ranging from 10(-2) to 10(-5)M was analyzed using fluorescence and CD spectra. When collagen was treated with DOPA, the intensity of emission was found to increase indicating the possibility of interaction of DOPA with collagen and maximum emission intensity was observed between 10(-3) and 10(-4)M for L-DOPA and DL-DOPA, respectively. CD studies show possible aggregation of collagen even in the presence of low concentrations of DOPA. The shrinkage temperature of DOPA treated collagen fibres was experimentally determined to be 69+/-1 degrees C. The melting temperature of DOPA cross linked collagen solution also exhibited a significant increase from 35 to 40 degrees C (+/-0.1) (P<0.05). The experimental results suggest that the optimum concentration for cross linking collagen with DOPA ranges between 10(-3) and 10(-4)M. Thus, DOPA may be a useful stabilizing agent for collagen for biomedical applications.


Assuntos
Colágeno/química , Reagentes de Ligações Cruzadas/química , Di-Hidroxifenilalanina/química , Levodopa/química , Dicroísmo Circular , Espectrometria de Fluorescência , Temperatura de Transição
11.
J Mater Sci Mater Med ; 20 Suppl 1: S131-6, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18568388

RESUMO

A self-assembled right handed helical ribbon of bone mineral, hydroxyapatite (HAp) was crystallized in sodium meta silicate gel matrix at 27 degrees C and the physiological pH (7.4). At temperatures 37 and 47 degrees C, helical structures were followed by many Liesegang rings. The samples were characterized by FT-IR, XRD, SEM, ICP-OES and TG-DTA techniques. The helical ribbon consisted of platy Ca-deficient apatite crystals of size 2.8 microm. Liesegang ring had a continuous network of fibers with interconnected pores. The samples exhibited bioactivity when soaked in SBF.


Assuntos
Substitutos Ósseos/química , Durapatita/química , Líquidos Corporais/fisiologia , Substitutos Ósseos/síntese química , Precipitação Química , Cristalização , Durapatita/síntese química , Conformação Molecular , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Alicerces Teciduais/química , Difração de Raios X
12.
Skeletal Radiol ; 37(6): 559-62, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18369616

RESUMO

Periosteal chondroma is a slow-growing, cartilaginous, surface tumor that usually occurs in the second and third decades of life. The youngest reported age at diagnosis is 5 years. Marginal excision is the treatment of choice. We report a case of a periosteal chondroma noted at birth and treated conservatively. This report expands the age range of periosteal chondroma to include neonates and suggests a role for observation in its management.


Assuntos
Neoplasias Ósseas/congênito , Neoplasias Ósseas/diagnóstico por imagem , Condroma/congênito , Condroma/diagnóstico por imagem , Úmero , Periósteo , Neoplasias Ósseas/patologia , Condroma/patologia , Feminino , Humanos , Recém-Nascido , Radiografia
13.
Chemosphere ; 70(6): 1015-24, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17983644

RESUMO

The ever-increasing attention to the environmental impact of leather industry has necessitated the development of enzyme-based processes as potent alternatives to pollution causing chemicals. In this study, a hair saving process is developed for dehairing of skins and hides using a bacterial alkaline protease preparation, completely eliminating the use of lime and sulfide. To evaluate the efficacy of the enzymatic process, comparative studies have been carried out with two controls; a conventional lime-sulfide process and enzyme-assisted process using commercial dehairing enzyme with reduced quantities of lime and sulfide. The developed process requires a shorter duration of 6h for complete dehairing of skins and hides than control groups and also, it avoids the use of silicate carriers since the enzymatic dehairing is carried out by dip method. Histological and scanning electron microscopic analyses of the dehaired pelts obtained from enzymatic process reveal complete removal of hair and epidermis with moderate opening up of fiber structure in both dermis and corium. Moreover, the collagen is not damaged and resulting in a leather of good quality. The developed process has resulted in a remarkable reduction of effluent load in terms of biochemical oxygen demand, chemical oxygen demand, total dissolved solids and total suspended solids. Physicochemical studies conclusively show that the leathers produced by enzymatic process are equivalent to or better than that obtained by control systems. Thus, the developed enzymatic process offers immense potential for greener mode of dehairing of skins and hides in leather industry coupled with environmental excellence.


Assuntos
Proteínas de Bactérias/metabolismo , Compostos de Cálcio/química , Endopeptidases/metabolismo , Remoção de Cabelo/métodos , Óxidos/química , Sulfetos/química , Animais , Bovinos , Cromatografia Líquida de Alta Pressão , Cabras , Microscopia Eletrônica de Varredura , Pele/química , Pele/metabolismo , Pele/ultraestrutura , Curtume/métodos , Poluição Química da Água/prevenção & controle
14.
Science ; 303(5657): 507-10, 2004 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-14739454

RESUMO

Well-ordered mesoporous silicate films were prepared by infusion and selective condensation of silicon alkoxides within microphase-separated block copolymer templates dilated with supercritical carbon dioxide. Confinement of metal oxide deposition to specific subdomains of the preorganized template yields high-fidelity, three-dimensional replication of the copolymer morphology, enabling the preparation of structures with multiscale order in a process that closely resembles biomineralization. Ordered mesoporous silicate films were synthesized with dielectric constants as low as 1.8 and excellent mechanical properties. The films survive the chemical-mechanical polishing step required for device manufacturing.

15.
Biomaterials ; 24(5): 759-67, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12485794

RESUMO

The physical properties of collagen-based biomaterials are profoundly influenced by the method and extent of crosslinking. In this study, the influence of various crosslinking treatments on the physical properties of reconstituted collagen membranes was assessed. Five crosslinking agents viz., GTA, DMS, DTBP, a combination of DMS and GTA and acyl azide method were used to stabilize collagen matrices. Crosslinking density, swelling ratio, thermo-mechanical properties, stress-strain characteristics and resistance to collagenase digestion were determined to evaluate the physical properties of crosslinked matrices. GTA treatment induced the maximum number of crosslinks (13) while DMS treatment induced the minimum (7). Of the two diimidoesters (DMS and DTBP), DTBP was a more effective crosslinking agent due to the presence of disulphide bonds in the DTBP crosslinks. T(s) for DTBP and DMS crosslinked collagen were 80 degrees C and 70 degrees C, and their HIT values were 5.4 and 2.85MN/m(2), respectively. Low concentration of GTA (0.01%) increased the crosslinking density of an already crosslinked matrix (DMS treated matrix) from 7 to 12. Lowest fracture energy was observed for the acyl azide treated matrix (0.61MJ/m(3)) while the highest was observed for the GTA treated matrix (1.97MJ/m(3)). The tensile strength of GTA treated matrix was maximum (12.4MPa) and that of acyl azide treated matrix was minimum (7.2MPa). GTA, DTBP and acyl azide treated matrices were equally resistant to collagenase degradation with approximately 6% solubilization after 5h while the DMS treated was least stable with 52.4% solubilization after the same time period. The spatial orientation of amino acid side chain residues on collagen plays an important role in determining the crosslinking density and consequent physical properties of the collagen matrix.


Assuntos
Materiais Biocompatíveis , Colágeno/química , Colagenases/metabolismo , Reagentes de Ligações Cruzadas/química , Colágeno/efeitos dos fármacos , Reagentes de Ligações Cruzadas/farmacologia , Hidroxiprolina/análise , Membranas Artificiais , Estresse Mecânico , Resistência à Tração , Termodinâmica
16.
J Biomed Mater Res ; 54(1): 122-8, 2001 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11077411

RESUMO

Crosslinking agents are used for improving the physical properties and durability of collagenous implants, glutaraldehyde (GTA) being the most widely used. Many of these reagents, including GTA, are known to be cytotoxic and to induce calcification. Hence, it is desirable to develop new crosslinking methods for collagen, so that biocompatibility and physical properties are improved. In the present study, dimethyl 3,3' -dithiobispropionimidate (DTBP) has been tried as a novel crosslinking reagent for collagen. Collagen purified from rat tail tendon has been crosslinked with DTBP and GTA. An increase of 22 degrees C in shrinkage temperature is observed for collagen treated with DTBP under optimal conditions. Crosslinking density determination shows that DTBP induces 10 crosslinks per mole, compared to 13 by GTA. While the tensile strength of GTA-treated samples is greater than those treated with DTBP, the latter shows more extensibility. In vitro degradation studies show that both GTA- and DTBP-treated samples are resistant to degradation by collagenase. The biocompatibility of crosslinked collagen samples studied by subcutaneous implantation in rats show that while both GTA- and DTBP-treated collagen do not degrade for up to 4 weeks, ultrastructural and histological studies indicate that DTBP collagen is far more biocompatible than GTA-treated matrices.


Assuntos
Colágeno/química , Reagentes de Ligações Cruzadas/química , Imidoésteres/química , Animais , Materiais Biocompatíveis/efeitos adversos , Materiais Biocompatíveis/química , Colagenases/química , Glutaral/química , Hidrólise , Hidroxiprolina/química , Lisina/química , Masculino , Membranas Artificiais , Microscopia Eletrônica , Ratos , Ratos Wistar , Estresse Mecânico
17.
J Biomed Mater Res ; 36(4): 478-86, 1997 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-9294763

RESUMO

Collagen was purified from bovine Achilles tendon and crosslinked with dimethyl suberimidate (DMS) and glutaraldehyde (GTA). Under optimal conditions, the shrinkage temperature (Ts) was raised to 74 degrees C for collagen crosslinked with DMS and to 80 degrees C for those crosslinked with GTA. Crosslinking density measurements were done on the hydrothermally denatured collagen by the method based on the Flory-Rehner equation. GTA treatment was found to introduce more number of crosslinks than DMS. The maximum tension attained during heating (after shrinkage has occurred) was greater for GTA-treated collagen than for DMS and control. The control collagen membranes broke during heating (at 73 degrees C), while for the crosslinked membranes the tension kept on increasing up to 100 degrees C. The crosslinking density correlated well with the data determined from the in vitro and in vivo degradation studies. Uncrosslinked and DMS crosslinked collagen membranes were more susceptible to degradation by enzymes in vitro, while GTA-treated collagen was highly resistant to degradation. The biocompatibility of the collagen membranes was studied by subcutaneous implantation in rats. Uncrosslinked collagen membranes degraded within 14 days with the formation of granulation tissue. DMS crosslinked membranes degraded within 21 days and the area was replaced by numerous fibroblasts and newly formed collagen. No calcification was observed. For GTA-treated membranes, necrosis was observed after 7 days implantation and by 14 days the membrane had started to calcify.


Assuntos
Colágeno/química , Reagentes de Ligações Cruzadas/química , Dimetil Suberimidato/química , Animais , Colagenases , Hidrólise , Hidroxiprolina , Lisina , Masculino , Teste de Materiais , Pepsina A , Ratos , Temperatura , Resistência à Tração , Termodinâmica , Tripsina
18.
J Biomater Sci Polym Ed ; 1(3): 167-72, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2125838

RESUMO

The effect of glutaraldehyde (GTA) on the course of collagen gel formation was studied by measuring the absorbance against time. It was found that the t1/2 of fibril formation decreased with the addition of GTA and reached a minimum at a concentration of 6 microliters of GTA per g of collagen. For GTA concentrations, [GTA], above this value, t1/2 increased again and fibril formation was inhibited at concentrations of about 50-60 microliters of GTA per g of collagen. Thermal analysis showed that the denaturation temperature was the highest for the gels formed with [GTA] of 6 microliters/g, the transition peak also being the sharpest. At this [GTA], the compressive rigidity of the gels was also the highest. For low [GTA], above and below the optimum value, the fibrils formed had the normal collagen periodicity when observed in the electron microscope. This study shows that collagen gels which find applications as biomaterials can be effectively crosslinked at the gelation stage itself by the addition of low concentrations of GTA.


Assuntos
Colágeno/química , Glutaral , Materiais Biocompatíveis , Varredura Diferencial de Calorimetria , Colágeno/ultraestrutura , Géis , Cinética , Microscopia Eletrônica
19.
Calcif Tissue Int ; 34(3): 301-5, 1982 May.
Artigo em Inglês | MEDLINE | ID: mdl-6809293

RESUMO

The tensile deformation characteristics of compact bone from deer antler were measured in both the "dry" and "wet" states and compared with published values for bovine compact bone. The tensile strength in the wet state (108 +/- 5.1 MN/m2) was comparable to the value for bovine compact bone tested at the same strain rate. The modulus values was very low: 7.5 +/- 0.9 GN/m2. The work to fracture was comparatively high, about 3 times that for bovine compact bone. Fractographic examination revealed fibrillar and osteonal shear for samples fractured in the dry state. In the samples tested in the wet state, some regions exhibited pullout of lamellar segments from within a Haversian system. The results are explained in terms of the higher collagen content and lesser degree of mineralization in the antler.


Assuntos
Chifres de Veado/fisiologia , Osso e Ossos/fisiologia , Cornos/fisiologia , Animais , Osso e Ossos/ultraestrutura , Cervos , Técnica de Fratura por Congelamento , Microscopia Eletrônica de Varredura , Resistência à Tração
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...