Ashai Chemical Industry Co. have developed a porous hollow fiber membrane BEMBERG MICROPOROUS MEMBRANE [BMM] to filter out and isolate AIDS virus [acquired immune deficiency syndrome virus] and hepatitis type B in blood. BMM is made from cellulose fiber [BEMBERG] regenerated from cuprammonium solutions of cotton linters.
Synthetic polymers are known to cause blood clotting as a result of protein adsorption. However, regenerated cellulose is free from this problem, and for this reason, is used for the artificial kidney in the form of hollow fiber. In order to allow proteins to permeate, but isolate viruses using the same membrane, it is necessary to have homogeneous pores in the membrane, which are larger than proteins but smaller than viruses. To produce such cellulose membranes having homogeneously distributed pores of predetermined diameter. Spherical B-type hepatitis virus and AIDS virus have a diameter of 42 nm and 90-100 nm. Respectively. Thus the membrane needs to have pores of 30-40 nm or 40-75 in diameter, respectively, to isolate these viruses. A single layer of membrane is not sufficient to isolate such viruses completely. Consequently BMM has a multi-layer structure of 100-150 layers. This manufacturing multi layer hollow fiber membrane is produced by wet spinning from cuprammonium solution of cotton linter mixed with an organic solvent. The solution undergoes phase separation and is composed of two phases made up of concentrated and a dilute organic solvent. The concentrated phase forms a continuous organic solvent layer, and the dilute phase make up small organic solvent holes of a uniform size in the cotton linter solution. When spun, the resulting hollow fiber is made of 100-150 layers of cellulose membrane, with pores of a predetermined diameter [see Photo6.2] The pore size and the degree of crystallinity of BMM depends on many external factors such as temperature, solvent composition, component purity and time. Usually BMM is 300 to 400 um in outer diameter, 250 to 350 um in inner diameter, and is composed 40 um in thickness. The actual module is made of 300 BMM hollow fibers which together are 3 cm in diameter and 15 cm in length. Each layer of BMM has over a billion pores, which enables complete filtration and isolation of the viruses.
It is capable of removing virus from plasma and so suppresses its multiplication. AIDS virus immersed into lymphocytes, grows there, and then overflows into plasma. If the isolation rate of virus from plasma is fast, the clinical progress of AIDS can be suppressed. This suppression of the AIDS virus can allow the reactivation of the metabolic functions of the human body, so that treatment efficiency will improve when combined with other medical treatments.
Other applications of BMM are found, for example, in the complete isolation of virus during plasma medicines manufacture, the administration of fractionated plasma-producing medicines for hemophiliacs, and the prevention of virus infection during ordinal plasma transfusion.
BMM is also useful for the isolation of hepatitis non-A non-B virus and in the study of unknown viruses or other physiologically active substances