127 research outputs found
Fabrication of a corneal-limbal tissue substitute using silk fibroin
No full textFibroin extracted from silkworm cocoon silk provides an intriguing and potentially important biomaterial for corneal reconstruction. In the present chapter we outline our methods for producing a composite of two fibroin-based materials that supports the co-cultivation of human limbal epithelial (HLE) cells and human limbal stromal (HLS) cells. The resulting tissue substitute consists of a stratified epithelium overlying a three-dimensional arrangement of extracellular matrix components (principally ‘degummed’ fibroin fibers) and mesenchymal stromal cells. This tissue substitute is currently being evaluated as a tool for reconstructing the corneal limbus and corneal epithelium
Enzyme-responsive hydrogels for biomedical applications
No full textThis chapter highlights recent developments in enzyme-responsive gels. The focus is on peptide-based small-molecule hydrogels, for biomedical applications. The use of enzymes in this context provides a powerful methodology for controlled assembly, taking advantage of both biological selectivity and catalytic amplification. The building blocks for self-assembly and basic design rules for small molecule peptide gelators are discussed first. This is followed by a discussion of key features of biocatalytic self-assembly of hydrogels, focusing on control of nanoscale organization and consequent function. Finally, the potential applications of the enzyme-responsive hydrogels as biomaterials are discussed in the areas of cell culture, drug delivery, biosensing, and control of cell fate
Challenges of Scale-up of Cell Separation and Purification Techniques
No full textThis chapter focuses on methodologies suitable for mammalian cell separation as opposed to purification of other biological entities like particles, proteins and non-mammalian cells. It describes reported separation methods that may lend themselves to large-scale cell separation. Resolution requirements for the separation platform will be largely dictated by the nature of the starting population. Open versus closed systems for cell processing refers to the extent to which cells are exposed to the ambient environment, with a 'closed' environment limited by the boundaries of the vessel or device the cells are contained in. Cell-based products create new issues for bio-production and processing, requiring a re-think of current manufacturing strategy. The health economics of cell production and the therapeutic efficacy of the therapy on which it is based must be competitive with existing non-cellular treatments or management of a disease and its symptoms.</p
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Microencapsulation of probiotic bacteria into alginate hydrogels
No full textMechanical characterization of hydrogels and its implications for cellular activities
No full textHydrogels are viscoelastic materials routinely used for the development of culture models in tissue engineering and regenerative medicine. They act as a temporary matrix, providing topographical, biochemical, and biophysical cues which cells can remodel and develop into a tissue. The mechanical properties of the hydrogel mutually affect the construct and the cells alike. It is important to determine and monitor a construct's material properties in order to recapitulate the in vivo environment, which usually involves strategies aimed at improving the mechanical properties. The mechanical properties of soft tissues are closely related to their physiological function and so can act as cellular biomarkers. Time, culture, and conditioning environments can all influence the structural and biochemical aspects of the tissue, which are important to their performance and durability, ultimately dictating whether the construct will be successful or not in a given application. This chapter begins with the discussion of current characterization tools for hydrogel mechanical properties with the focus on non-destructive testing modalities. How mechanical properties can become a biomarker in regenerative medicine has been demonstrated through corneal stromal and ageing models. Various strategies for improving and tailoring the mechanical properties of hydrogels are discussed
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Influence of substrate on corneal epithelial cell viability within ocular surface models
No full textCorneal tissue engineering has improved dramatically over recent years. It is now possible to apply these technological advancements to the development of superior in vitro ocular surface models to reduce animal testing. We aim to show the effect different substrates can have on the viability of expanded corneal epithelial cells and that those which more accurately mimic the stromal surface provide the most protection against toxic assault. Compressed collagen gel as a substrate for the expansion of a human epithelial cell line was compared against two well-known substrates for modeling the ocular surface (polycarbonate membrane and conventional collagen gel). Cells were expanded over 10 days at which point cell stratification, cell number and expression of junctional proteins were assessed by electron microscopy, immunohistochemistry and RT-PCR. The effect of increasing concentrations of sodium lauryl sulphate on epithelial cell viability was quantified by MTT assay. Results showed improvement in terms of stratification, cell number and tight junction expression in human epithelial cells expanded upon either the polycarbonate membrane or compressed collagen gel when compared to a the use of a conventional collagen gel. However, cell viability was significantly higher in cells expanded upon the compressed collagen gel. We conclude that the more naturalistic composition and mechanical properties of compressed collagen gels produces a more robust corneal model
Approaches to Corneal Tissue Engineering: Top-down or Bottom-up?
No full textAbstractTissue engineering creates biological tissues that aim to improve the function of diseased or damaged tissues such as the cornea (the main refractive component of the eye). Traditional tissue engineering strategies employ a “top-down” approach, in which cells are seeded on a polymeric scaffold that they then populate and create the appropriate extracellular matrix (ECM) often with the aid of perfusion, growth factors and/or mechanical stimulation. However, in highly organised tissues, such as the cornea, top-down approaches have difficulty recreating intricate but necessary microstructural features.With the desire to create more complex corneal tissues with features such as anisotropic hierarchical molecular assemblies, appropriate mechanical properties, cell binding motifs and corneal specific morphology, we are developing tissue engineering techniques that are moving away from the traditional top-down approach and instead focusing on building modular micro-tissues with repeated functional units which facilitate a bottom-up approach.Here we report on the success and shortcomings of both top-down and bottom-up approaches to creating engineered corneal tissues. Specifically, we will discuss recent work demonstrating the importance of engineering corneal ECM with appropriate levels of tissue compliance using a top-down approach. We will then highlight a bottom-up approach, which focuses on fabricating discreet bio-prosthetic ECM building blocks (corneal lamellae) with specific micro-architectural features derived solely from human corneal keratocytes under serum free conditions using enzyme responsive templates. These building blocks will then be used to generate a whole cornea whilst maintaining the intricate architecture and complexity of native corneal ECM
Françoise Rubellin (sous la direction de), Théâtre de la Foire. Anthologie de pièces inédites (1712-1736)
No full textIl Teatro della Foire, dopo gli studi pionieristici di Marcello Spazioni, e quelli, più recenti, di Dominique Lurcel, Renzo Guardenti, Derreck Connon, George Evans, David Trott e Isabelle Martin, per non citare che i più noti ed importanti, è, come fenomeno sociale e letterario, ormai abbastanza ben conosciuto. Meno sicure sono, a tutt’oggi, le nostre conoscenze per quanto riguarda il suo repertorio. Di fondamentale importanza, il Théâtre de la Foire pubblicato da Lesage e d’Orneval negli ann..
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