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Delivery of Ovarian Hormones for Bone Health
Published in Emmanuel Opara, Controlled Drug Delivery Systems, 2020
Thus, diffusional limitations in general are a potential challenge for all cell-encapsulation systems. The primary reasons for this are associated with the diffusion of oxygen and nutrients (e.g., glucose) into the cells within the encapsulation system and diffusion of metabolic waste products out of the encapsulation system. It is straightforward to mathematically model the system to determine a concentration profile for a given species (nutrient or waste product) based on the continuity equation in radial coordinates (see Figure 7.5c): ∂G∂t+[1r2∂∂r(r2NG,r)+1rsinθ∂∂θ(NG,θsinθ)+1rsinθ∂NG,φ∂φ]=Rateofreaction
Nanotechnology in Cell Delivery Systems
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Ali Golchin, Parisa Kangari, Sepideh Mousazadehe, Faeza Moradi, Simzar Hosseinzadeh
Encapsulation is defined as a membrane with a pore structure to entrap cells or tissue in a biocompatible material that has permeability for nutrients, oxygen and hormones while preventing entry of immune cells into the cell-containing matrix. Cell encapsulation represents a strategy for regulated delivery of protein and morphogen, drug delivery, cell delivery and 3D culture in stem cell research field. Encapsulated cell-based therapies are under study for a variety of diseases such as bone and cartilage defects, treatment of chronic anemia, myocardial regeneration and neurological diseases (Orive et al. 2014).
Hyaluronan-Based Hydrogels as Functional Vectors for Standardised Therapeutics in Tissue Engineering and Regenerative Medicine
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
Alexandre Porcello, Alexis Laurent, Nathalie Hirt-Burri, Philippe Abdel-Sayed, Anthony de Buys Roessingh, Wassim Raffoul, Olivier Jordan, Eric Allémann, Lee Ann Applegate
As a non-adherent material allowing generation of moist and sterile “in vivo-like” environments, hyaluronan hydrogels allow for rehydration of tissues and absorption of skin lesion exudates in a reversible manner, depending on environmental stimuli (i.e. temperature, pH). Various hyaluronan-based products have been proposed for the topical management of burn wounds, including cell-free (e.g. Hyalomatrix®, Hyalosafe®, HYAFF®-11, Ialugen®) and cell-laden constructs (e.g. Hyalograft 3D™, Laserskin™) (Turner et al. 2004; Tezel and Fredrickson 2008; Shevchenko et al. 2010; Longinotti 2014; Dalmedico et al. 2016). Clinical studies have confirmed the benefits of such constructs in the treatments of burn victims (Harris et al. 1999; Price et al. 2007; Gravante et al. 2010; Voigt and Driver 2012; Fino et al. 2015). Hyaluronan hydrogels have been characterised as moderately beneficial for topical delivery of therapeutic materials, depending on the extent and gravity of cutaneous lesions, with variable tissue penetration capacities, wherein a MW of 100 kDa enabled optimal passage through the disrupted skin barrier (Mesa et al. 2002; Witting et al. 2015). Qualitatively, hyaluronan hydrogels provide comfort during application, with a refreshing sensation and soothing effect which may contribute to significantly alleviate pain (Jones and Vaughan 2005). Structurally, hyaluronan hydrogels mimic native ECM and promote maintenance of tissue hydration and oxygenation via water retention, detritus and pathogenic microorganisms trapping, and cell protection by creating a physical barrier (Madaghiele et al. 2014; Guo et al. 2015). Their use as a supporting matrix for wound treatment may be complemented by the combined use of therapeutic cells, which may be encapsulated within the hydrogel, wherein culture conditions within such three-dimensional environments have been shown to be optimal. In addition to intrinsic biocompatibility and biological activity, natural hyaluronan confers various benefits in tissue engineering workflows, such as ECM remodelling chaperoning or the promotion of cellular functions of both therapeutic transplanted cells and recipient endogenous cells (Khademhosseini et al. 2006; Dicker et al. 2014; Thönes et al. 2017). Additionally, cell encapsulation within a biomaterial may potentially reduce inherent immunogenicity of therapeutic materials (Schmidt et al. 2008).
Review of the immobilized microbial cell systems for bioremediation of petroleum hydrocarbons polluted environments
Published in Critical Reviews in Environmental Science and Technology, 2018
Entrapment is one of the cell immobilization techniques in which microorganisms are enclosed in a porous polymeric matrix to allow the diffusion of substrate and product (Martins et al., 2013). Therefore, mass transfer is one of the major factors affecting the activity and efficiency of IC systems (Barreto et al., 2010; Cassidy et al., 1996; Siripattanakul and Khan, 2010). Entrapment involves inclusion of cells within a polymer network (lattice entrapment), or a membrane, or a microcapsule (Přenosil et al., 2009). Gel entrapment and preformed porous matrices are two different techniques for cell entrapment within porous matrices. In gel entrapment, the porous matrix is synthesized in situ around the cell, while for preformed systems, cells diffuse into the preformed porous matrix and grow until they are immobilized (Ha, 2005; Karel et al., 1985). The gel entrapment technique confines microbial cells within the pores of a matrix. The entrapped cells are surrounded by a bulky thick layer. Cell encapsulation is similar to entrapment technique in which the cells are free in the solution, but restricted inside a thin layer (shell) (Kampf, 2002; Siripattanakul and Khan, 2010). These techniques are sometimes interchanged as the same type of cell immobilization. However, entrapment matrices are recognized to be more durable than encapsulation matrices and therefore are more suitable for environmental applications (Siripattanakul and Khan, 2010).
Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment
Published in International Journal of Phytoremediation, 2022
Palak Saket, Mrinal Kashyap, Kiran Bala, Abhijeet Joshi
Immobilization of microalgae in polymeric carriers employs several techniques of encapsulation, which enables localization of micro-algal cells and does not allow the cells to move freely in the aqueous medium (Rouf et al.2017). The most common methods for immobilization of living cells are using gel or any reliable support like polymer (Chen et al.2007). The advantages of this technique, in comparison to suspended cells, include the protection of cells against toxic substances and avoid the costly processes of recovery and cell recycle (Dursun and Tepe 2005). The gel matrix provides mechanical strength, along with characteristics like rigidness and permeability (Annadurai et al.2000). Many gel matrices are used as possible carriers for the encapsulation of microalgae. Natural polymers like polysaccharides, alginate, carrageenan, chitosan or synthetic polymers like polyurethane and polyesters are common choices for cell encapsulation (Hameed et al.2007) (Figure 3). The most commonly used method of immobilization include the syringe dropping technique where polymer solution is dropped into a non-solvent or a cross-linker (e.g., divalent or multivalent cations) to precipitate or gel encapsulating the cells (Hunik and Tramper 1993; de-Bashan and Bashan 2010). Encapsulation of cells and their industrial-level scale-up has been highly investigated. Formation of droplets by extrusion technique is the rate-limiting step for the creation of beads in large quantity (Hunik and Tramper 1993). In one of the attempts of scale-up, a device was developed for the production of a large number of beads (2–4mm) like an open showered box having an array of 64 individual shaped apertures formed in the bottom plate. The liquid polymer was poured into the box and beads formed under gravity (de-Bashan and Bashan 2010).