Protein fouling

The present state of the art in blood pH measurements allows for rapid (1 minute) determination of pH between 6.4 and 8.0 to within at least 0.005 units for whole blood sample volumes < 100 microliters. The temperature of the electrodes and sample is generally controlled to within 0.1 °C for this level of precision and frequent calibration is carried out (in some cases a one point calibration for each sample). The electrodes require (both the glass and external reference) some maintenance due to protein fouling, however this procedure is largely automated. The useful life of an electrode is one year or less and the cost is well over 100 (U.S.) each. New technologies, both electrochemical and non-electrochemical, must compete with this attractive performance and provide for lower operating costs in order to be successful. 

For the conditions in Fig. 9, improvements of 35-50% in the permeate flux were observed when a secondary membrane was used, owing to a reduction in the protein fouling of the primary membrane. Little or no flux recovery was observed with each backpulse, as might be expected from the relatively low resistance of the yeast layer and the irreversible nature of the protein fouling. The flux continuously declined with time owing to irreversible fouling, though the rate of decline was reduced by the SMY. 

Ho CC, Zydney AL (2000), A combined pore blockage and cake filtration model for protein fouling during microfiltration, J. Colloid Interface Sci. 232 389-399. 

Chan R and Chen V. Characterization of protein fouling on membranes opportunities and challenges. J. Membr. Sci. 2004 242 169-188. Rosenbloom AJ, Sipe DM, Shishkin Y, Ke Y, Devaty RP, and Choyke WJ. Nanoporous SiC a candidate semi-permeable material for biomedical applications. Biomed. Microdev. 2004 6(4) 261-267. 

FIGURE 22.12 Protein fouling of internal pore surfaces of MF membrane following filtration of skimmed milk at 300 psi TMP for 30 min. (From James, B.J., Jing, Y., and Chen, X.D.,. Food Eng., 60, 431, 2003. With permission.)... 

Marshall, A.D., Munro, P.A., and Tragardh, G., The effect of protein fouling in microfiltration and ultrafiltration on permeate flux, protein retention and selectivity A literature review, Desalination, 91, 65, 1993. 

Sheldon, J.M., Reed, I.M., and Hawes, C.R., The fine-stmeture of ultrafiltration membranes. II. Protein fouled membranes, J. Membr. 

Mourouzidis-Mourouzis, S.A. and Karabelas, A.J., Whey protein fouling of microfiltration ceramic membranes— pressure effects, J. Membr. Sci., 282, 124, 2006. 

Palacio, L., Ho, C.-C., and Zydney, A.L., Application of a pore-blockage—cake-filtration model to protein fouling during microfiltration, Biotech. Bioeng., 79, 260, 2002. 

Belfer, S. et al., Surface characterization by FT-IR-ATR spectroscopy of polyethersulfone membranes—unmodified, modified and protein fouled, J. Membr. Sci., 172, 113, 1997. 

P. Pradanos, A. Hernandez, J. I. Calvo, and F. Tejerina, Mechanisms of protein fouling in cross-flow UF through an asymmetric inorganic membrane. J. Membr. Sci. 114, 115-126 (1996). 

An example of a hemodialyzer is shown in Figure 45-17. The most important fimctional part is the dialyzer membrane. Biocompatibihty of the dialyzer membrane is an essential requirement because of high surface areas and long contact times with blood. The most important physiological interactions that occur, apart from protein fouling of tubing and membranes, are complement activation and induction of cytokine release. 

Rios et al. [72] show that with small pores (< 0.2 pm) protein fouling remains on the outside of the membrane, whereas with the larger pore sizes the pores become blocked by the intrusion of protein into these pores. 

Kim, K.J. et al., Chemical and elechical characterization of virgin and protein-fouled polycarbonate track-etched membranes by FTIR and sheaming-potential measurements,/. Membr. Sci., 134, 199, 1997. 

Much work has been done with polymers to create biocompatible surfaces that resist protein fouling, i.e., non specific adsorption. A membrane composed of modified polyethersulfone (PES) (Omega Membrane) resisted albumin (ALB) absorption 24 times better than unmodified PES, and three times better than regenerated cellulose, a material known to resist biofouling. We compared porous SiC, both n-type and p-type, to the Omega Membrane [14] and found a very similar resistance to ALB absorption (Figure 12.3). 

Fouling with proteins has been measured with C marked proteins. Fouling was much higher for hydrophobic membranes like PA and PS, compared to CA. An inflection point in the adsorption isotherms indicated that two mechanisms of adsorption existed. A relationship between adsorption and hydraulic permeabilitj existed (Matthiasson (1983)). 

M. Taniguchi and G. Belfort. Low protein fouling synthetic membranes by UV-assisted surface grafting modification Varying monomer type. J. Membr. Set, 231(1-2) 147-157, March 2004. 

Wavhal DS and Fisher ER, Membrane surface modification by plasma-induced polymerization of acrylamide for improved surface properties and reduced protein fouling, Langmuir 2003,19, 79-85. 

Chan R and Chen V. Characterization of protein fouling on membranes Opportunities and challenges. J. Membr. Sci. 2004 242 169-188. 

Most chemical cleaning protocols consist of an alkali detergent step followed by an acid step, with appropriate rinses in between. However, for polymeric membranes, it is also common to follow the acid cleaning step with a second alkali cleaning step supplemented with chlorine as this further improves flux [179,183], In some cases, acid cleaning has been recommended as the first step, especially for whey applications, where mineral fouling may be more important than protein fouling [179],... 

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