Gold-coated collagen nanofibers (GCNFs) were produced by a single-step reduction process and used for the growth and differentiation of human adult stem cells. The nanomaterials were characterized by a number of analytical techniques including electron microscopy and spectroscopy. They were found to be biocompatible and to improve the myocardial and neuronal differentiation process of the mesenchymal stem cells isolated from the placental chorionic component. The expression of specific differentiation markers (atrium, natriuretic peptide, actin F and actin monomer, glial fibrilary acidic protein, and neurofilaments) was investigated by immunocytochemistry.
"Mechanical stimulation of osteoblasts or stem cells induced by the properties of the implant surface triggers the reorganization of the focal adhesion plaques followed by the rearrangement of the cytoskeleton and the activation of signaling pathways involved in osteogenic cell differentiation such as transcription factors Cbfa1 (Core Binding Factor A1) and Osterix. As a consequence osteoblasts synthesize higher amounts of collagen I, osteopontin, osteocalcin and bone sialoprotein, and induce higher levels of alkaline phosphatase activity
[55-57]. The canonical Wnt (Wingless/Integrated) signaling pathway is also activated with consequences on β-catenin, alkaline phosphatase and osteocalcin expression, as Galli et al. showed in a study using mesenchymal and osteoblastic cells growing on polished titanium discs versus acid-etched and sand-blasted (SLA) surfaces. "
[Show abstract][Hide abstract] ABSTRACT: Background
The development of novel biomaterials able to control cell activities and direct their fate is warranted for engineering functional bone tissues. Adding bioactive materials can improve new bone formation and better osseointegration. Three types of titanium (Ti) implants were tested for in vitro biocompatibility in this comparative study: Ti6Al7Nb implants with 25% total porosity used as controls, implants infiltrated using a sol–gel method with hydroxyapatite (Ti HA) and silicatitanate (Ti SiO2). The behavior of human osteoblasts was observed in terms of adhesion, cell growth and differentiation.
The two coating methods have provided different morphological and chemical properties (SEM and EDX analysis). Cell attachment in the first hour was slower on the Ti HA scaffolds when compared to Ti SiO2 and porous uncoated Ti implants. The Alamar blue test and the assessment of total protein content uncovered a peak of metabolic activity at day 8–9 with an advantage for Ti SiO2 implants. Osteoblast differentiation and de novo mineralization, evaluated by osteopontin (OP) expression (ELISA and immnocytochemistry), alkaline phosphatase (ALP) activity, calcium deposition (alizarin red), collagen synthesis (SIRCOL test and immnocytochemical staining) and osteocalcin (OC) expression, highlighted the higher osteoconductive ability of Ti HA implants. Higher soluble collagen levels were found for cells cultured in simple osteogenic differentiation medium on control Ti and Ti SiO2 implants. Osteocalcin (OC), a marker of terminal osteoblastic differentiation, was most strongly expressed in osteoblasts cultivated on Ti SiO2 implants.
The behavior of osteoblasts depends on the type of implant and culture conditions. Ti SiO2 scaffolds sustain osteoblast adhesion and promote differentiation with increased collagen and non-collagenic proteins (OP and OC) production. Ti HA implants have a lower ability to induce cell adhesion and proliferation but an increased capacity to induce early mineralization. Addition of growth factors BMP-2 and TGFβ1 in differentiation medium did not improve the mineralization process. Both types of infiltrates have their advantages and limitations, which can be exploited depending on local conditions of bone lesions that have to be repaired. These limitations can also be offset through methods of functionalization with biomolecules involved in osteogenesis.
[Show abstract][Hide abstract] ABSTRACT: Multidimensional scaffolds are considered to be ideal candidates for regenerative medicine and tissue engineering based on their potential to provide an excellent microenvironment and direct the fate of the cultured cells. More recently, the use of stem cells in medicine has opened a new technological opportunity for controlled tissue formation. However, the mechanism through which the substrate directs the differentiation of stem cells is still rather unclear. Data concerning its specific surface chemistry, topology, and its signaling ability need to be further understood and analyzed. In our study, atomic force microscopy was used to study the stiffness, roughness, and topology of the collagen (Coll) and metallized collagen (MC) substrates, proposed as an excellent substrate for regenerative medicine. The importance of signaling molecules was studied by constructing a new hybrid signaling substrate that contains both collagen and laminin extracellular matrix (ECM) proteins. The cellular response-such as attachment capability, proliferation and cardiac and neuronal phenotype expression on the metallized and non-metallized hybrid substrates (collagen + laminin)-was studied using MTT viability assay and immunohistochemistry studies. Our findings indicate that such hybrid materials could play an important role in the regeneration of complex tissues.
"However, with the synergy of carbon nano-dimensional materials, researchers have been able to overcome these tissue engineering and regenerative medicine obstacles and have begun developing treatments for strokes, bone failure, cardiovascular disease, and many other ailments. Application of nanomaterials including CNTs in the biomedical field provides a provision of an appropriate nano-biointerface for the control of cellular behavior, and, therefore, optimizes tissue regeneration [20, 21]. "
[Show abstract][Hide abstract] ABSTRACT: Cases reporting traumatic injuries to the brain and spinal cord are extended range of disorders that affect a large percentage of the world's population. But, there are only few effective treatments available for central nervous system (CNS) injuries because the CNS is refractory to axonal regeneration and relatively inaccessible to many pharmacological treatments. The use of stem cell therapy in regenerative medicine has been extensively examined to replace lost cells during CNS injuries. But, given the complexity of CNS injuries oxidative stress, toxic byproducts, which prevails in the microenvironment during the diseased condition, may limit the survival of the transplanted stem cells affecting tissue regeneration and even longevity. Carbon nanotubes (CNT) are a new class of nanomaterials, which have been shown to be promising in different areas of nanomedicine for the prevention, diagnosis and therapy of certain diseases, including CNS diseases. In particular, the use of CNTs as substrates/scaffolds for supporting the stem cell differentiation has been an area of active research. Single-walled and multi-walled CNT's have been increasingly used as scaffolds for neuronal growth and more recently for neural stem cell growth and differentiation. This review summarizes recent research on the application of CNT-based materials to direct the differentiation of progenitor and stem cells toward specific neurons and to enhance axon regeneration and synaptogenesis for the effective treatment of CNS injuries. Nonetheless, accumulating data support the use of CNTs as a biocompatible and permissive substrate/scaffold for neural cells and such application holds great potential in neurological research.
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