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1.
Cureus ; 15(9): e45105, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37842465

RESUMO

OBJECTIVE: The objective of this study was to determine the prevalence of end-organ damage in hypertensive patients attending an outpatient consultation. MATERIALS AND METHODS: Patients were selected from an outpatient consultation at a tertiary hospital care center. All patients who consulted between July 2022 and March 2023 were included. Data on demographic characteristics, blood pressure records, hypertension etiology, medication use, and the presence of target organ damage were collected. RESULTS: A total of 73 patients were included in the study, with 34 patients being male (46.6%) and 39 patients being female (53.4%). The mean age of the patients was 49.8 years. Among the cases of hypertension, 14 (19.2%) were classified as secondary arterial hypertension (AH). The most common cause of secondary AH was obstructive sleep apnea (OSA) (42.9%). Approximately 23.2% of patients had documented end-organ damage potentially related to hypertension, with kidney disease being the most frequent (n = 10, 13.7%). The most commonly prescribed pharmacological classes were angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists (n = 46, 63%). CONCLUSION: Despite numerous studies and trials on arterial hypertension, it remains a significant contributor to morbidity and mortality, necessitating the continued awareness of its long-term implications.

2.
Cureus ; 15(5): e39240, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37342741

RESUMO

Chorea is a hyperkinetic movement disorder characterized by a continuous flow of rapid, random, and involuntary bodily contractions, usually affecting the distal limbs. When these movements are more proximal or assume a larger amplitude with a flinging or kicking character, they're referred to as ballism. These disorders can be associated with several causes, ranging from genetic and neurovascular to toxic, autoimmune, and metabolic. Non-ketotic hyperglycemic hemichorea-hemiballismus is a rare consequence of decompensated diabetes mellitus with a poorly understood pathogenesis but with characteristic MRI T1 and T2 hyperintense abnormalities in the contralateral basal ganglia. We present the case of a 74-year-old woman with a history of poorly controlled type 2 diabetes mellitus, dyslipidemia, and arterial hypertension who was admitted to the emergency room due to a two-day history of rapid non-stereotypical involuntary movements of the left side of her body. A neurological exam showed large amplitude and repetitive left-side body movements. Glycemia was 541 mg/dL with no ketosis. Her glycosylated hemoglobin was 14%. A brain CT excluded acute abnormalities. Brain MRI showed a discrete T1 hyperintense signal involving the right corpus striatum, compatible with non-ketotic hyperglycemic hemichorea-hemiballism syndrome. After metabolic optimization with insulin and haloperidol, the movements resolved. Early recognition and metabolic control are essential to the resolution of choreiform movements. Our aim is to raise awareness for hyperglycemic hemichorea-hemiballismus, in which decompensated diabetes is the early sign of diagnosis.

3.
Cureus ; 15(1): e33651, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36788849

RESUMO

Löfgren syndrome is an acute presentation of sarcoidosis that comprises fever, bilateral and symmetric hilar lymphadenopathies, polyarthritis, and erythema. We present the case of a 34-year-old male patient who presented with ankle monoarthritis without a history of a traumatic event. Contralateral ankle arthritis associated with erythema nodosum and fever developed one week later. Laboratory tests showed anemia, thrombocytosis, and elevated inflammatory parameters. A chest CT revealed symmetrical mediastinal and hilar adenopathies. A transbronchial biopsy was compatible with granulomatous lymphadenitis, and the diagnosis of Löfgren syndrome was confirmed. Our case report and literature review emphasize the wide web of mimicry of acute sarcoidosis. Secondary forms of acute sarcoidosis are likely to benefit from additional and more complex immunomodulatory therapies. Close monitoring and follow-up should be conducted because it is possible that these patients experience higher rates of recurrence or relapse.

4.
Cureus ; 15(1): e33820, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36819315

RESUMO

Severe secondary hyperparathyroidism in advanced stages of chronic kidney disease (CKD) is associated with CKD-related mineral and bone disease (CKD-MBD). A 70-year-old woman was admitted at the Hospital for generalized bone pain and peripheral edema. Initial laboratory tests revealed normocytic anemia and severe renal dysfunction, and further tests evidenced severe secondary hyperparathyroidism. Full-body computerized tomography showed an osteolytic lesion in the right iliac wing. The iliac bone lesion was biopsied and histological examination was consistent with the diagnosis of a brown tumor of hyperparathyroidism. Brown tumors are a rare variant of osteitis fibrosa cystica that results from sustained high levels of parathyroid hormone in CKD. This case sheds light on rare complications that are experienced today in CKD. The clinical and biochemical setting, as well as the clinical suspicion, are essential to the diagnosis.

5.
Cureus ; 14(11): e31976, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36589195

RESUMO

Common variable immunodeficiency (CVID) is a disease characterized by severe antibody deficiency due to impaired B cell differentiation. It represents the most common form of primary immunodeficiency in children and adults, and its clinical manifestations include recurrent infections and chronic lung disease, gastrointestinal infections, and autoimmunity. Here, we present the case of a 47-year-old female patient with a history of CVID and recurrent Campylobacter jejuni bacteremia. She was undergoing biweekly administration of intravenous immunoglobulin for over 15 years. During hospitalization rapidly progressive oliguric renal failure was observed in association with anasarca and nephrotic syndrome. Bilateral nephromegaly was noted on an abdominal pelvic computed tomography scan. Renal biopsy was consistent with amyloidosis, and serum amyloid A protein was elevated. The diagnosis of AA amyloidosis secondary to CVID was made. The patient was started on hemodialysis and weekly intravenous immunoglobulin administration with favorable clinical outcomes.

6.
Acta Biomater ; 128: 222-235, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-33878475

RESUMO

The sublingual mucosa is an appealing route for drug administration. However, in the context of increased use of therapeutic proteins, development of protein delivery systems that will protect the protein bioactivity is needed. As proteins are fragile and complex molecules, current sublingual formulations of proteins are in liquid dosage. Yet, protein dilution and short residence time at the sublingual mucosa are the main barriers for the control of the dose that is delivered. In this work, a simple delivery scaffold based on the assembly of two polysaccharides, chitosan and hyaluronic acid, is presented. The natural polymers were assembled by the Layer-by-Layer methodology to produce a mucoadhesive and oro-dispersible freestanding membrane, shown to be innocuous for epithelial human cells. The functionalization of the membrane with proteins led to the production of a bioactive patch with efficient loading and release of proteins, and suitable mechanical properties for manipulation. Sublingual administration of the patch in mouse evidenced the absence of inflammation and an extended time of contact between the model protein ovalbumin and the mucosa compared to liquid formulation. The delivery of fluorescent ovalbumin in mouse sublingual mucosa demonstrated the penetration of the protein in the epithelium 10 min after the patch administration. Moreover, a migration assay with a chemokine incorporated into the patch showed no decrease in bioactivity of the loaded protein after enzymatic release. This study therefore provides a promising strategy to develop a sublingual protein delivery system. STATEMENT OF SIGNIFICANCE: Although the oral route is largely used for drug delivery, it has limitations for the delivery of proteins that can be degraded by pH or gastric enzymes. The sublingual route therefore appears as an interesting approach for protein administration. In this work, a simple delivery scaffold is presented based on the assembly of two polysaccharides by the Layer-by-Layer methodology to produce a mucoadhesive patch. The produced patch allowed efficient loading and release of proteins, as well as protection of their bioactivity. An extended time of contact between the protein and the mucosa compared to liquid formulation was highlighted in mouse model. This study provides a promising strategy to develop a sublingual protein delivery system.


Assuntos
Mucosa Bucal , Polímeros , Administração Sublingual , Animais , Sistemas de Liberação de Medicamentos , Camundongos , Proteínas
7.
Eur J Case Rep Intern Med ; 7(8): 001614, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32789126

RESUMO

A 77-year-old man with arterial hypertension and dyslipidaemia, treated with olmesartan/hydrochlorothiazide and simvastatin, was admitted with a 3-week history of anorexia, nausea, vomiting, profuse diarrhoea and weight loss. He was dehydrated and blood tests showed acute kidney injury. The aetiological study was inconclusive. The patient had a favourable clinical evolution during hospitalization and was discharged. However, after about 10 days at home, he was re-admitted to hospital with the same clinical presentation. It was noticed that olmesartan had not been prescribed during the previous admission but had been restarted on an outpatient basis. Biopsy examination showed duodenal mucosa with villous atrophy and polymorphic inflammatory infiltrate. Antibody testing for coeliac disease was negative. Based on these facts, it was hypothesized that the patient had olmesartan-induced enteropathy, which was subsequently confirmed. LEARNING POINTS: Drug-induced sprue-like enteropathy must be considered in the differential diagnosis of patients with diarrhoea, weight loss, and villous atrophy of the duodenal mucosa of unknow origin.Olmesartan has been associated with the development of enteropathy.Olmesartan-induced enteropathy can happen years after drug initiation.

8.
Eur J Case Rep Intern Med ; 6(12): 001352, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31893208

RESUMO

A woman in her early 40s, with a history of excessive alcohol intake, presented with purpuric, ulcerative lesions on the lower limbs. On examination, hirsutism and generalized stiffening and thickening of the skin were noted. Laboratory investigations revealed hyperbilirubinemia, hypergammaglobulinemia and positive anti-smooth muscle antibodies. Histologic examination of the skin was compatible with scleroderma. Histologic examination of the liver was suggestive of autoimmune and alcoholic hepatitis. LEARNING POINTS: Alcohol intake is a main cause of hepatic disease but it is mandatory to exclude other causes.Autoimmune hepatitis and systemic sclerosis may be associated, therefore patients with these diseases should be monitored closely.There exist scores that can be helpful in the diagnosis of both autoimmune hepatitis and systemic sclerosis.

9.
Acta Biomater ; 69: 183-195, 2018 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-29378324

RESUMO

This work is the first reporting the use of layer-by-layer to produce adhesive free-standing (FS) films fully produced using natural-based macromolecules: chitosan (CHI), alginate (ALG) and sulfated levan (L-S). The deposition conditions of the natural polymers were studied through zeta potential measurements and quartz crystal microbalance with dissipation monitoring analysis. The properties of the FS films were evaluated and compared with the control ones composed of only CHI and ALG in order to assess the influence of levan polysaccharide introduced in the multilayers. Tensile tests, dynamic mechanical analysis and single lap shear strength tests were performed to evaluate the mechanical properties of the prepared FS films. The presence of L-S conferred both higher tensile strength and shear strength to the developed FS membranes. The results showed an adhesion strength 4 times higher than the control (CHI/ALG) FS films demonstrating the adhesive character of the FS films containing L-S. Morphological and topography studies were carried out revealing that the crosslinking reaction granted the L-S based FS film with a higher roughness and surface homogeneity. Preliminary biological assays were performed by cultivating myoblasts cells on the surface of the produced FS films. Both crosslinked and uncrosslinked FS films containing L-S were cytocompatible and myoconductive. STATEMENT OF SIGNIFICANCE: Sutures remain as the "gold standard" for wound closure and bleeding control; however they still have limitations such as, high infection rate, inconvenience in handling, and concern over possible transmission of blood-borne disease through the use of needles. One of the challenges of tissue engineering consist on the design and development of biocompatible tissue adhesives and sealants with high adhesion properties to repair or attach devices to tissues. In this work, the introduction of sulfated levan (L-S) on multilayered free-standing membranes was proposed to confer adhesive properties. Moreover, the films were myoconductive even in the absence of crosslinking just by the presence of L-S. This study provides a promising strategy to develop biological adhesives and for cardiac tissue engineering applications.


Assuntos
Alginatos/química , Bandagens , Quitosana/química , Frutanos/química , Teste de Materiais , Membranas Artificiais , Adesivos Teciduais/química , Adesão Celular , Linhagem Celular , Humanos
10.
Tissue Eng Part A ; 23(23-24): 1502-1533, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28903686

RESUMO

This review is focused on the use of membranes for the specific application of bone regeneration. The first section focuses on the relevance of membranes in this context and what are the specifications that they should possess to improve the regeneration of bone. Afterward, several techniques to engineer bone membranes by using "bulk"-like methods are discussed, where different parameters to induce bone formation are disclosed in a way to have desirable structural and functional properties. Subsequently, the production of nanostructured membranes using a bottom-up approach is discussed by highlighting the main advances in the field of bone regeneration. Primordial importance is given to the promotion of osteoconductive and osteoinductive capability during the membrane design. Whenever possible, the films prepared using different techniques are compared in terms of handability, bone guiding ability, osteoinductivity, adequate mechanical properties, or biodegradability. A last chapter contemplates membranes only composed by cells, disclosing their potential to regenerate bone.


Assuntos
Regeneração Óssea , Membranas Artificiais , Osteogênese , Engenharia Tecidual/métodos , Animais , Humanos
11.
Adv Healthc Mater ; 6(15)2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28371516

RESUMO

Inspired by native extracellular matrix (ECM) together with the multilevel architecture observed in nature, a material which topography recapitulates topographic features of the ECM and the internal architecture mimics the biological materials organization is engineered. The nanopatterned design along the XY plane is combined with a nanostructured organization along the Z axis on freestanding membranes prepared by layer-by-layer deposition of chitosan and chondroitin sulfate. Cellular behavior is monitored using two different mammalian cell lines, fibroblasts (L929) and myoblasts (C2C12), in order to perceive the response to topography. Viability, proliferation, and morphology of L929 are sensitively controlled by topography; also differentiation of C2C12 into myotubes is influenced by the presence of nanogrooves. This kind of nanopatterned structure has also been associated with strong cellular alignment. To the best of the knowledge, it is the first time that such a straightforward and inexpensive strategy is proposed to produce nanopatterned freestanding multilayer membranes. Controlling cellular alignment plays a critical role in many human tissues, such as muscles, nerves, or blood vessels, so these membranes can be potentially useful in specific tissue regeneration strategies.


Assuntos
Materiais Biomiméticos/síntese química , Polaridade Celular/fisiologia , Tamanho Celular , Matriz Extracelular/química , Fibroblastos/fisiologia , Membranas Artificiais , Impressão Tridimensional , Fibroblastos/citologia , Humanos , Teste de Materiais , Mioblastos/citologia , Mioblastos/fisiologia , Propriedades de Superfície , Engenharia Tecidual/métodos
12.
Biomacromolecules ; 17(4): 1347-57, 2016 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-26957012

RESUMO

The lack of knowledge on the degradation of layer-by-layer structures is one of the causes hindering its translation to preclinical assays. The enzymatic degradation of chitosan/hyaluronic acid films in the form of ultrathin films, freestanding membranes, and microcapsules was studied resorting to hyaluronidase. The reduction of the thickness of ultrathin films was dependent on the hyaluronidase concentration, leading to thickness and topography variations. Freestanding membranes exhibited accelerated weight loss up to 120 h in the presence of the enzyme, achieving complete degradation. Microcapsules with around 5 µm loaded simultaneously with FITC-BSA and hyaluronidase showed that the coencapsulation of such enzyme and protein mixture led to a FITC-BSA release four times higher than in the absence of hyaluronidase. The results suggest that the degradation of LbL devices may be tuned via embedded enzymes, namely, in the controlled release of active agents in biomedical applications.


Assuntos
Cápsulas/química , Quitosana/metabolismo , Preparações de Ação Retardada/síntese química , Sistemas de Liberação de Medicamentos/métodos , Ácido Hialurônico/metabolismo , Hialuronoglucosaminidase/metabolismo
13.
BMJ Case Rep ; 20162016 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-26791119

RESUMO

A 49-year-old woman presented at the emergency department, with acute hepatic failure, 2 weeks after taking nimesulide. Presenting with a MELD score of 25.0, the patient was transferred to a specialised liver transplant unit, with the probable diagnosis of toxic hepatitis. After a clinical improvement with supportive care and acetylcysteine, a liver biopsy was executed. The histology revealed micronodular cirrhosis associated with acute hepatitis, with features suggestive of autoimmune hepatitis. The patient was then started on azathioprine 50 mg/day and prednisolone 30 mg/day, and tapering of prednisolone was carried out in the following months. Twenty eight months after treatment, another liver biopsy was performed, showing almost full remission of the disease, with only mild fibrosis and no significant inflammatory infiltrate.


Assuntos
Anti-Inflamatórios não Esteroides/efeitos adversos , Hepatite Autoimune/diagnóstico , Fígado/patologia , Sulfonamidas/efeitos adversos , Feminino , Hepatite Autoimune/complicações , Hepatite Autoimune/patologia , Humanos , Fígado/efeitos dos fármacos , Cirrose Hepática/diagnóstico , Cirrose Hepática/etiologia , Falência Hepática Aguda/diagnóstico , Falência Hepática Aguda/etiologia , Pessoa de Meia-Idade , Dor/tratamento farmacológico , Sulfonamidas/uso terapêutico
15.
Soft Matter ; 12(4): 1200-9, 2016 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-26617221

RESUMO

The design of self-standing multilayered structures based on biopolymers has been attracting increasing interest due to their potential in the biomedical field. However, their use has been limited due to their gel-like properties. Herein, we report the combination of covalent and ionic cross-linking, using natural and non-cytotoxic cross-linkers, such as genipin and calcium chloride (CaCl2). Combining both cross-linking types the mechanical properties of the multilayers increased and the water uptake ability decreased. The ionic cross-linking of multilayered chitosan (CHI)-alginate (ALG) films led to freestanding membranes with multiple interesting properties, such as: improved mechanical strength, calcium-induced adhesion and shape memory ability. The use of CaCl2 also offered the possibility of reversibly switching all of these properties by simple immersion in a chelate solution. We attribute the switch-ability of the mechanical properties, shape memory ability and the propensity for induced-adhesion to the ionic cross-linking of the multilayers. These findings suggested the potential of the developed polysaccharide freestanding membranes in a plethora of research fields, including in biomedical and biotechnological fields.


Assuntos
Alginatos/química , Quitosana/química , Membranas Artificiais , Adesividade , Cálcio/química , Reagentes de Ligações Cruzadas/química , Resistência à Tração
16.
Langmuir ; 31(41): 11318-28, 2015 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-26421873

RESUMO

We investigated the pH-dependent properties of multilayered films made of chitosan (CHI) and alginate (ALG) and focused on their postassembly response to different pH environments using a quartz crystal microbalance with dissipation monitoring (QCM-D), swelling studies, ζ potential measurements, and dynamic mechanical analysis (DMA). In an acidic environment, the multilayers presented lower dissipation values and, consequently, higher moduli when compared with the values obtained for the pH used during the assembly (5.5). When the multilayers were exposed to alkaline environments, the opposite behavior occurred. These results were further corroborated by the ability of this multilayered system to exhibit a reversible swelling-deswelling behavior within the pH range from 3 to 9. The changes in the physicochemical properties of the multilayer system were gradual and different from those of individual solubilized polyelectrolytes. This behavior is related to electrostatic interactions between the ionizable groups combined with hydrogen bonding and hydrophobic interactions. Beyond the pH range of 3-9, the multilayers were stabilized by genipin cross-linking. The multilayered films also became more rigid while the pH responsiveness conferred by the ionizable moieties of the polyelectrolytes was preserved. This work demonstrates the versatility and feasibility of LbL methodology to generate inherently pH stimulus-responsive nanostructured films. Surface functionalization using pH responsiveness endows several biomedical applications with abilities such as drug delivery, diagnostics, microfluidics, biosensing, and biomimetic implantable membranes.


Assuntos
Alginatos/química , Quitosana/química , Eletrólitos/química , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Técnicas de Microbalança de Cristal de Quartzo , Eletricidade Estática
17.
Bioconjug Chem ; 26(8): 1571-81, 2015 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-26106949

RESUMO

Injectable hyaluronic acid (HA)-based hydrogels compose a promising class of materials for tissue engineering and regenerative medicine applications. However, their limited mechanical properties restrict the potential range of application. In this study, cellulose nanocrystals (CNCs) were employed as nanofillers in a fully biobased strategy for the production of reinforced HA nanocomposite hydrogels. Herein we report the development of a new class of injectable hydrogels composed of adipic acid dihydrazide-modified HA (ADH-HA) and aldehyde-modified HA (a-HA) reinforced with varying contents of aldehyde-modified CNCs (a-CNCs). The obtained hydrogels were characterized in terms of internal morphology, mechanical properties, swelling, and degradation behavior in the presence of hyaluronidase. Our findings suggest that the incorporation of a-CNCs in the hydrogel resulted in a more organized and compact network structure and led to stiffer hydrogels (maximum storage modulus, E', of 152.4 kPa for 0.25 wt % a-CNCs content) with improvements of E' up to 135% in comparison to unfilled hydrogels. In general, increased amounts of a-CNCs led to lower equilibrium swelling ratios and higher resistance to degradation. The biological performance of the developed nanocomposites was assessed toward human adipose derived stem cells (hASCs). HA-CNCs nanocomposite hydrogels exhibited preferential cell supportive properties in in vitro culture conditions due to higher structural integrity and potential interaction of microenvironmental cues with CNC's sulfate groups. hASCs encapsulated in HA-CNCs hydrogels demonstrated the ability to spread within the volume of gels and exhibited pronounced proliferative activity. Together, these results demonstrate that the proposed strategy is a valuable toolbox for fine-tuning the structural, biomechanical, and biochemical properties of injectable HA hydrogels, expanding their potential range of application in the biomedical field.


Assuntos
Tecido Adiposo/citologia , Celulose/química , Ácido Hialurônico/química , Hidrogéis/administração & dosagem , Células-Tronco Mesenquimais/citologia , Nanopartículas/química , Engenharia Tecidual , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Humanos , Hidrogéis/química , Células-Tronco Mesenquimais/efeitos dos fármacos , Células-Tronco Mesenquimais/metabolismo , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Macromol Rapid Commun ; 36(4): 405-12, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25639465

RESUMO

This work investigates the influence of the hydration level on the molecular mobility and glass transition dynamics of freestanding chitosan/alginate (CHT/ALG) nanolayered systems. Nonconventional dynamic mechanical analysis identifies two relaxation processes assigned to the α-relaxation of the two biopolymers, respectively, CHT and ALG, when immersed in water/ethanol mixtures. This phenomenon explains the shape memory properties of the multilayered systems induced by hydration, thus constituting promising smart materials that would be of paramount importance in a plethora of research fields, including in the biomedical and biotechnological fields.


Assuntos
Nanoestruturas/química , Polímeros/química , Alginatos/química , Quitosana/química , Etanol/química , Vidro/química , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Água/química
19.
Acta Biomater ; 15: 139-49, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25575853

RESUMO

Free-standing (FS) membranes have increasing applications in the biomedical field as drug delivery systems for wound healing and tissue engineering. Here, we studied the potential of free-standing membranes made by the layer-by-layer assembly of chitosan and alginate to be used as a simple biomimetic system of the periosteum. The design of a periosteum-like membrane implies the elaboration of a thick membrane suitable for both muscle and bone formation. Our aim was to produce well-defined ∼50 µm thick polysaccharide membranes that could be easily manipulated, were mechanically resistant, and would enable both myogenesis and osteogenesis in vitro and in vivo. The membranes were chemically crosslinked to improve their mechanical properties. Crosslinking chemistry was followed via Fourier transform infrared spectroscopy and the mechanical properties of the membranes were assessed using dynamic mechanical analysis. The loading and release of the potent osteoinductive growth factor bone morphogenetic protein 2 (BMP-2) inside and outside of the FS membrane was followed by fluorescence spectroscopy in a physiological buffer over 1 month. The myogenic and osteogenic potentials of the membranes in vitro were assessed using BMP-2-responsive skeletal myoblasts. Finally, their osteoinductive properties in vivo were studied in a preliminary experiment using a mouse ectopic model. Our results showed that the more crosslinked FS membranes enabled a more efficient myoblast differentiation in myotubes. In addition, we showed that a tunable amount of BMP-2 can be loaded into and subsequently released from the membranes, depending on the crosslinking degree and the initial BMP-2 concentration in solution. Only the more crosslinked membranes were found to be osteoinductive in vivo. These polysaccharide-based membranes have strong potential as a periosteum-mimetic scaffold for bone tissue regeneration.


Assuntos
Membranas Artificiais , Desenvolvimento Muscular/efeitos dos fármacos , Mioblastos/citologia , Osseointegração/efeitos dos fármacos , Polissacarídeos/farmacologia , Animais , Proteína Morfogenética Óssea 2/farmacologia , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Reagentes de Ligações Cruzadas/farmacologia , Humanos , Camundongos , Microscopia Eletrônica de Varredura , Mioblastos/efeitos dos fármacos , Osteogênese/efeitos dos fármacos , Proteínas Recombinantes/farmacologia , Imagem com Lapso de Tempo , Fator de Crescimento Transformador beta/farmacologia , Microtomografia por Raio-X
20.
J Mater Chem B ; 3(22): 4555-4568, 2015 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-32262400

RESUMO

Tissues presenting continuous variations of properties in one direction have inspired the development of functional graded materials. In this work, we developed a new facile method for the development of continuous gradients in chitosan (CHIT) and alginate (ALG) polyelectrolyte multilayers (PEMs) obtained layer-by-layer based on the gradual dipping of CHIT/ALG coated glass slides in genipin solution. Stiffness gradients were produced in the cm scale by varying the reaction time with genipin. Quartz crystal microbalance, colorimetric measurements, trypan blue assay, attenuated total reflection-Fourier transform infrared spectroscopy, swelling ability, water contact angle and dynamic mechanical analysis (DMA) were used to find suitable conditions for the stiffness gradient. The PEMs can be successfully built up and cross-linked with genipin to yield surfaces with uniform physicochemical properties or with gradients of different physicochemical properties. It was found that a large reduction in the hydrophobic nature of the CHIT/ALG PEMs could be produced with higher cross-linking reaction times, regardless of the decrease in their swelling ability. Moreover, the mechanical properties were evaluated using an innovative and non-conventional DMA to monitor the cross-linking reaction in situ. The results confirm an enhancement on the tensile storage modulus with increasing reaction times from 60 to 140 MPa. In another original DMA testing protocol the local compression storage modulus was also measured directly on the films along the stiffness gradient, with results consistent with the tensile tests obtained on the freestanding membranes with different cross-linking degrees. The in vitro biological performance demonstrates that L929 adhered and spread more in the stiffer regions. This work demonstrates the versatility and feasibility of the LbL methodology to generate functional biomimetic surfaces with tuned mechanical and physicochemical properties, which hold great promise for the study of cell-substrate interactions.

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