Cellophane, surface area

The only type of semi-permeable tubing suitable and available at that time was the cellophane skin used for sausages. Kolff evaluated that a surface area of about 1 m was suitable for an efficient and fast enough dialysis. This same surface area is still the reference for haemodialysis membranes. A mandatory requirement is that albumin should not cross the membrane. 

All of the fibrous cellulose samples and the cellophane film conform to a linear relationship with larger surface areas corresponding to higher amounts of... 

The anode is a high surface area, amalgamated, gelled zinc metal powder housed in a top cup which serves as the external negative terminal for the cell. The top cup is pressed from a triclad metal sheet the outer surface is a protective layer of nickel over a core of steel. The inner surface that is in direct contact with the zinc is high-purity copper or tin. The cathode pellet is consolidated into the positive can, which is formed from nickel-plated steel and serves as the positive terminal for the cell. To keep the anode and cathode separated, a barrier disk of cellophane or a grafted plastic membrane is placed over the consolidated cathode. The entire system is wetted with potassium or sodium hydroxide electrolyte. 

Previously13 investigators usually used back or forearm skin for the experiment. It was easier to induce scaly skin on back skin than on forearm skin. In the case of back skin, we stripped SC nine times with adhesive cellophane tape. At that time, the transepidermal water loss (TEWL) value was over 10 mg/cm2/h and most of the SC was removed. In the case of forearm, to induce dry, scaly skin, stripping for 30 to 50 times was needed. One week after treatment, TEWL was higher than the normal level, skin surface conductance decreased, and SC cell area also decreased (Table 10.1). The skin surface became scaly and flaky. Figure 10.1 shows skin surface pictures of the forearm skin with and without barrier disruption. Abnormal scaling is observed on the surface of skin, which was treated with tape stripping. These phenomena are commonly observed in natural dry skin, such as atopic dermatitis and psoriasis. 

The untreated cellulose substrates were examined by scanning electron microscopy prior to the autoclave experiments. The dissolving pulp (Figure la) and the cotton fibers have textured surfaces with clearly visible fibrils. The lyocell fibers on the other hand are nearly devoid of surface features (Figure lb). The cellophane film has a completely flat surface with a few spherical shaped inhomogeneities, while the cellulose membranes display distinct porous structures. The 1.0 pm cellulose membranes were clearly inhomogeneous, with large flat areas interspersed with porous structures. 

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