Oxygen permeability waste

An important feature of cell membranes is that they are semi-permeable, which means that some substances can pass through them, but others cannot. This way, a cell can control what it needs to allow in (nutrients, oxygen, water) and out (waste products from reactions). 

The following conclusions may be drawn from these studies. For example, the process of encapsulation is sufficiently mild that entrapped cells retain the ability to divide and multiply. The cells must also be substantially protected from the cationic polymer during encapsulation. The capsule wall must, therefore, be permeable to required nutrients including high molecular weight components of FBS and oxygen, and allow for a rapid removal of cell waste products and for equilibration of osmolarity and pH with the capsule exterior. 

PLA is a semicrystaUine plastic that can be injection molded, extruded or blown into film, spun into fibers, blow molded, extruded, and expansion molded. The somewhat lower thermal stability and impact strength (Lim et al., 2008) as well as the moderate oxygen/water permeability (van Tuil et al., 2000) may limit its use in some applications despite its low cost (Lunt, 1998). Compostability of PLA is emphasized in marketing PLA products even though the product is compostable, it does not readily biodegrade under ambient conditions or under anaerobic conditions (Integrated Waste Management Board, 2007) (see also Chapter 6). 

All cells are bounded by a plasma membrane. This membrane is selectively permeable—allowing certain things in and out while excluding others. Useful substances like oxygen and nutrients enter through the membrane, while waste products like carbon dioxide leave through it. These movements involve physical (passive) processes such as ... 

The miniPERM Bioreactor (30, 31) consists of two components, the production module (40 ml) containing the ceUs and the nutrient module (600 ml of medirrm). The modules are separated by a semi-permeable dialysis membrane (MWCO 12.5 kDa) which retains the cells and mAb in the production module but allows metabolic waste products to diffuse out to the nutrient module. There is a permeable silicone rubber membrane for oxygenation and gas exchange in the production module. The whole unit rotates (up to 40 r.p.m.) within a CO2 incubator. It can be purchased as a complete disposable ready to use unit or the nutrient module (polycarbonate) can be autoclaved and reused at least ten times. 

Adequate permeability for diffusion of essential nutrients (e.g., oxygen and glucose for islets of Langerhans) and cell secretory products (such as insulin, metabolic waste) Impermeability to secreted antibodies of the host s immune system (e.g., immunoglobulins and glycoproteins after complement activation ... 

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