Polycation detection membranes

Soon after the initial development of the heparin sensor, an electrode for the detection of the polycation protamine was proposed [38] based on a polymeric membrane doped with the cation exchanger tetrakis-(4-chlorophenyl)borate. Protamine is a polypeptide and usually administered as a heparin antidote. Protamine is a polycation with an average charge of +20 and is rich in arginine (Fig. 4.8). The response function of protamine-selective electrodes is similar to the heparin response function (Fig. 4.9b). 

Abd-Rabboh HSM, Nevins SA, Dilriist N, Meyerhoflf ME. Electrochemical assay of protease activities based on polycation/polyanion complex as substrate and polyion sensitive membrane electrode detection. Biosensors and Bioelectronics 2003 18 229-36. http //dx.doi.org/10.1016/S0956-5663(02)00181-l. 

There are several major parameters that need to be well considered before the polyelectrolyte solutions are employed for the fabrication or modification of NF membranes. These adjustments are especially important when the polyelectrolyte solutions need to be self-adsorbed onto the membrane surfaces. One of the parameters studied by researchers was the solution pH. A detailed study on the role of polyelectrolyte solution pH was carried out using weak polyelectrolytes in the construction of polyelectrolyte multilayers (PEMs) using poly(acrylic acid) and poly(allylamine hydrochloride) (PAH) (Shiratori and Rubner 2000). Researchers postulated that through the polyelectrolyte solution pH adjustment, the thickness of an adsorbed polyanion or polycation layer can be varied from SA to 80A. Besides, researchers also found that a significant change in the polyelectrolyte adsorption behavior, and an alteration in the polyelectrolyte layer thickness can be detected over a very narrow pH range. This research work has provided some insightful ideas in the development of NF membranes with controllable adsorption behaviors and characteristics. 

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