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Marine biodiversity as a new source of promising polysaccharides
Published in Antonio Trincone, Enzymatic Technologies for Marine Polysaccharides, 2019
Sylvia Colliec-Jouault, Corinne Sinquin, Agata Zykwinska, Christine Delbarre-Ladrat
With their polyanionic properties, the EPS can be considered such as GAG-mimetics, but this similarity can be improved by either chemical or enzymatic modifications. The ability of the native HMW form of HE800 EPS to enhance in vivo bone repair has been demonstrated in a rat model (Zanchetta et al. 2003). We assumed that native HE800 EPS could be a good candidate as a biomaterial employed to design biocompatible scaffolds, especially in association with fibrillar collagens. HE800 EPS has been identified as a good candidate for constructing skin substitutes or dermal equivalent with functional properties, especially in association with fibrillar collagens. It presents HA-like activities, and it can promote both collagen structuring in dermal equivalent and fibroblast colonization of this reconstructed tissue (Senni et al. 2013). A very recent study showed that a biomaterial made of HMW GY785 EPS incorporated in an injectable cellulose-based hydrogel-bearing siloxane group (silated hydroxypropylmethylcellulose or Si-HPMC) and transplanted into nude mice stimulated the production of a cartilage-like extracellular matrix containing high amounts of GAG and type II collagen when compared to Si-HPMC alone. These results indicate that HMW GY785 EPS-enriched Si-HPMC is a promising hydrogel for cartilage tissue engineering (Rederstorff et al. 2017).
Effects of the surrounding medium on terahertz wave scattering loss in intrabody communication
Published in Waves in Random and Complex Media, 2022
Skin consists of epidermis, dermis and subcutaneous fat layers. It contains more than 50% water by weight (viable epidermis consists of 70% water while its stratum corneum contains 15%–30% water. 60%–70% of all the skin water percentage exists in the dermis). Therefore D-Debye model is applicable for skin and its two layers. The epidermis consists mostly of keratinocytes (90%) so the D-Debye parameters of the epidermis are attributed to keratinocytes as scatterers, while that of skin (whole skin) is attributed to its surrounding medium. In the dermis layer, fibroblasts are in a mesh of fiber collagens so a mixture of fibroblast and collagen, which is also called dermal equivalent (DE), is considered as the scatterer and the dermis parameters are taken for the background medium (collagen and dermal equivalent concentrations are 2 mg/ml and 0.1 M/ml, respectively) [37]. Both the keratinocyte and fibroblast have a size much smaller than the terahertz wavelength. Keratinocyte size differs between 15–50 µ m, whereas fibroblast diameter varies in the range of 10–15 µ m. Keratinocytes are born spherical in the deep basal layer and fibroblasts have an elongated shape. The spherical shape is assumed for both cells and due to their small size, their loss is calculated with Rayleigh. This time without modifying, the scattering coefficient of a spherical shape in Rayleigh's regime is [38] Considering the small difference between scatterers and medium in these layers, the Born approximation is applicable. Therefore, As it can be seen, the relationship between refractive indices plays a big role in scattering efficiency. It should be noted that both the refractive indices of the scatterer and its medium are frequency dependent. The scattering Coefficient is calculated as in which =(volume fraction)/(volume of the particle) and is the geometrical cross-section. At a certain distance of d, the scattering path loss is defined as
3D bio-printing technology for body tissues and organs regeneration
Published in Journal of Medical Engineering & Technology, 2018
Esmaeil Biazar, Masoumeh Najafi S., Saeed Heidari K., Meysam Yazdankhah, Ataollah Rafiei, Dariush Biazar
Emerging techniques using 3D bio-printing have shown great potential as a suitable technique for skin regeneration. Using a 3D bio-printer, this technique involves printing bioactive substances to design biocompatible scaffolds that replace traditional skin grafts. The biocompatible and porous structures of these scaffolds facilitate cell adhesion and migration, material exchange such as oxygen and nutrients, and deep tissue growth in the wounds. Gatenholm et al. [40] compared two types of nano-fibrillated cellulose (NFC)-based inks for 3D printing skin. NFC-based inks modified with the tripeptide Arg-Gly-Asp (RGD) (NFC-RGD) have been investigated and compared with NFC-alginate ink in terms of 3D printing of the human skin model. The NFC-alginate and NFC-RGD inks were mixed with alginate and human fibroblasts and bio-printed. After bio-printing, the hydrogels were cross-linked in a 100 mM CaCl2 solution. Cell viability and morphology were investigated as well as gene expression. The RGD peptides were coupled to the NFCs covalently. The formulations of the bio-inks were evaluated in terms of rheology, printability and cross-link ability. NFC-alginate and NFC-RGD demonstrate analogous rheological properties when measuring shear rate-viscosity. After 7 d in the incubator, both NFC-RGD and NFC-alginate showed high-cell viability results. The NFC-alginate has high printability and cell compatibility for printing with human chondrocytes. The RGD modification increased the Human fibroblasts proliferation. Lee et al. [41] describe the development, optimisation and application of a 3D on-demand cell and protein-printing platform for the engineering of biological tissues and organs using human skin as a prototypical example (Figure 1). A multi-layered cell and matrix structure was constructed in which human keratinocytes were grown at the Air–Liquid Interface (ALI) culture on collagen matrices embedded with human dermal FBs. Their studies indicated that printing cells and proteins in nano-to-microlitre droplets on planar surfaces similar to inkjet printing had a minimal effect on cell viability and function either in monocultures or in co-cultures. Viability for both cell types used in this study, keratinocytes and fibroblasts was sufficiently high (∼95% or greater for a majority of conditions) with the ability to achieve uniform distribution of fibroblasts in the dermal compartment and that of keratinocytes in the epidermis. The fully matured skin tissue exhibited 3–7 distinct cell layers in the epidermis, suggesting the stratification of the epidermis into its sub-strata (Figure 2). The presence of tight junctions between keratinocytes in the epidermis indicated a well-formed barrier with extensive cell–cell contacts, as would be expected in vivo. Histological characterisation of mature cultures indicated that a multi-layered epithelium growing on a dermal equivalent containing fibroblasts and collagen matrix is formed by the end of ALI culture. Studies have shown that the epithelial–mesenchymal crosstalk controls epidermal regeneration, implying that the functional status of both the keratinocytes and fibroblasts contributes to epidermal differentiation [41].