Structure of Cuprammonium Regenerated Cellulose Hollow Fiber (BMM Hollow Fiber) for Virus Removal

Abstract

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

Structure and Filtration Performances of Improved Cuprammonium Regenerated Cellulose Hollow Fiber (Improved BMM Hollow Fiber) for Virus Removal

“…We investigated the pore structure of BMM using an electron microscope 5 and the mechanism of the capture of particles by this BMM employing the monodisperse gold particles as a model substance of virus. 6 The results are summerized as follows:…”

“…One is "capillaries" with a diameter of several tens nm, scattering everywhere in the membrane and constructing network-like passages and the other is "voids" with the diameter of several hundreds nm having bulky block-like shape. 5 (2) "Channels" composed of "voids" continuously linking side by side and penetrating membrane from the inner to the outer surface are formed by elongation of fibers in a direction parallel to the fiber axis during spinning. 5 (3) The capture mechanism of the particles such as gold particles and viruses by BMM is classified, as plugging in "capillaries" and trapping in "voids".…”

“…5 (2) "Channels" composed of "voids" continuously linking side by side and penetrating membrane from the inner to the outer surface are formed by elongation of fibers in a direction parallel to the fiber axis during spinning. 5 (3) The capture mechanism of the particles such as gold particles and viruses by BMM is classified, as plugging in "capillaries" and trapping in "voids". 6 (4) "Channels" composed of "voids" play the role of a pathway for viruses resulting in decrease in the virus removability.…”

“…6 (4) "Channels" composed of "voids" play the role of a pathway for viruses resulting in decrease in the virus removability. 5 (5) The membrane which has "neuronic capillary-void structure" near the outer surface can be considered ideal for virus removal. This ideal structure may be realized by minimizing elongation of fl.bes during spinning.…”

Mechanism of Removing Monodisperse Gold Particles from a Suspension Using Cuprammonium Regenerated Cellulose Hollow Fiber (BMM Hollow Fiber)

“…Figure 9 shows a schematic representation of the pore structure of the membrane. 8 Capillaries are very narrow and constitute a large number of channels (A) linking themselves throughout the whole thickness of the membrane. The pores formed by voids are large and classified into three types: the first is the pore which is linked to other voids only by capillaries (B), the second is the pore which is neighbored by several voids and open to either inner surface or outer surface (C) (not depicted in the figure) and the third is the pore which constitute channels penetrating the membrane from one surface to the other surface (D).…”