ABSTRACT:To get higher performances of virus removability and permeability of protein than those of the previous cuprammonium regenerated cellulose hollow fiber (referred to as BMM) novel spinning conditions such as minimerized tension loaded on a fiber in addition to high accurate control of temperature and composition were employed (the novel BMM hollow fiber thus obtained is referred to as i-BMM). Comprehensive analysis of the pore structure of i-BMM using electron microscope and its filtration characteristics concerning to virus removability and protein permeability indicated that (1) the degree of orientation of the cellulosic substrate and "voids" in i-BMM to the direction of the fiber axis decreased comparied with that of BMM and this led to the disappearance of the breakage of the cellulosic wall between neighbouring voids, (2) the size of the capillary of i-BMM was larger than that of BMM, (3) the virus removability of i-BMM for Japanese encephalitis virus was about 10 3 times BMM when the comparison was made under the same mean pore size. These indicate that the existence probability of"voids" linking side by side and penetrating the membrane from the inner to the outer surface decreased for i-BMM and this is the reason i-BMM is superior to BMM in virus removal.KEY WORDS Regenerated Cellulose / Hollow Fiber / Electron Micrography / Gold Particle / Virus / Protein / Because of the complexity of pore structure and difficulty to investigate pore structure, most theoretical approaches or practical interpretations for membrane permselectivity have based their structures on a straightthrough cylindrical pore model. 1 It is nearly impossible to explain high performance of microporous cuprammonium regenerated cellulose hollow fiber (referred to as BMM in short) 2 -4 in virus removability and protein permeability by this simple model. This indicates sophisticated investigation about pore structure of actual membrane is necessary for better understanding of the high performance of BMM and for improvement to get higher performance.We investigated the pore structure of BMM using an electron microscope 5 and the 1085

ABSTRACT:An attempt to analyze the pore structure of the cuprammonium regenerated cellulose hollow fiber (BMM hollow fiber) in order to clear up its filtration mechanism was made. The electron microscopy was employed to get the concrete images of the structure. The cellulose particles of rod-like shape with circular cross section having mean diameter of about 50 nm were its constructing units. The pores were classified into two types, i.e., the pore with the average diameter of about 50 nm and another with the diameter of several hundreds to several thousands nm. The former was estimated to be the capillary formed among neighboring cellulose particles and the latter to be the void formed as a vacant space which was originated by the phase separation as polymer Jean phase. The frequency distribution curve of the void size showed several peaks indicating the occurrence of the boundary breakage between voids originated by the elongation of the fiber in the spinning process. The performances of BMM depends mainly on the existence of capillaries, then BMM with higher ability may be obtained by means of the spinning method which can decrease the occurrence of structure breakage due to the elongation during spinning.KEY WORDS Regenerated Cellulose/ Hollow Fiber/ Electron Micrography / Membrane Structure / Pore / Virus / Several years ago we developed the cuprammonium regenerated cellulose hollow fiber (BMM hollow fiber) for virus remova1. 1 -4 The performance of this hollow fiber was evaluated through many tests and it has proved to have the high rejection rate for HIV (causative agent of AIDS) and HBV (hepatitis B virus) while showing the high permeability for proteins even with high molecular weight such as clotting factor eight and nine. structure dominate its performance. The detailed structure of the connection of "voids" and "capillaries" in a membrane should be clarified using direct observation of pores in addition to demonstrating the existence of "voids" and "capillaries" experimentally.According to our previous paper, 5 it was deduced that viruses are caught by BMM hollow fiber through two kinds of mechanism, that is, trapping within "voids" and plugging of "capillaries" and the characteristics of pore In this article we intend to analyze thoroughly the membrane structure of BMM hollow fiber by means of electron microscopy to elucidate its filtration performance and to get the basic concept for improving its performance.751

ABSTRACT:In order to clarify the mechanism of removing viruses with cuprammonium regenerated cellulose hollow fiber (BMM hollow fiber), monodisperse gold particles were used. The dependences of the concentration of gold particles in the filtrate on the particle concentration and the particle size were investigated. The particles were considered to be caught by BMM through two mechanisms, that is, plugging of capillaries and trapping within voids. Here, the capillaries stand for the narrow pathway among neighboring cellulose particles which construct the membrane and the voids the bulky space surrounded by the aggregated cellulose particles. In the initial stage, the plugging of the capillaries causes decrease in the particle concentration. On the other hand, trapping leads to the occupation of spaces within the voids. When the voids near the inner surface are occupied by gold particles, the particles proceed inwards through channels formed by voids and finally flow out from the outer surface of the membrane. This leads to increase in the particle concentration in the preceding stage. The removability of the particles depends both on the relative size bewtween the capillary (or the void) and the particle and on the trapping capacity.KEY WORDS Regenerated Cellulose I Hollow Fiber I Gold Particle I Virus I Membrane Structure I Ultrafiltration I In the 19th century, viruses were named a filtrable microbe because of their filtrability through a porcelain plate, In 1937, Elford used a membrane filter prepared from collodion solution in order to decide the size of viruses. 1 From this result, a virus was known to be a particle larger size than protein molecule. He imaged the membrane was constructed with the straight through cylindrical pores and viruses were caught on the membrane surface not in its inside. Recently, this sieving mechanism of viruses with the membrane was again applied to decide the dimension of nonAnonB hepatitis virus. 2 That is, the straight through cylindrical pores in the membrane were coated with albumin so as to minimize the adsorption of virus by the polymeric membrane. He assumed that the pore size distribution was very sharp such as being expressed as <5 function and that all viruses having larger diameter than pore size were caught only on the membrane surface. When an appropriate membrane having smaller pore size than the size of virus is used in a laboratory the filtrate obtained may become virus-free, but this membrane is not adequate for industrial usage. This is because it cannot meet the following demands to the filtration performance:1) The virus logarithmic rejection coefficient cf>v defined by eq 1 is not less than 4, 304 Polym.

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We intended to clarify the mechanism of virus removal in aqueous protein solution and human plasma solution through conventional and high performance regenerated cellulose hollow fiber (i.e., BMM and i-BMM). We employed Japanese encephalitis virus (JEV) as a typical virus. Two kinds of disperse gold particles (GP) with different size were represented as model particles of a virus and protein particles. We investigated the filtration characteristics concerning removability of GP and JEV (