Novel magnetic and fluorescent nanocomposite as a sensitive probe for the determination of proteins

The Fe(3)O(4)/(sodium oleic acid/ethyltrimethyl ammonium bromide)(n)/4-aminobenzoic acid (Fe(3)O(4)/(NaOL/CTAB)(n)/PABA) nanocomposites have been prepared by a layer-by-layer self-assembly approach. This kind of nanocomposites have fluorescent, magnetic and water-soluble properties. Taking advantage of the magnetic property of nanocomposites, we can separated them from solution easily by using a permanent magnet. By using their strong fluorescence, we can detect proteins. At pH 6.98, the fluorescence of Fe(3)O(4)/(NaOL/CTAB)(n)/PABA nanocomposites can be enhanced by the proteins. Under optimal conditions, the linear ranges of calibration curves were 0.2-20, 0.2-13, 0.2-10 microg mL(-1) for gamma-globulin (gamma-IgG), human serum albumin (HSA), and bovine serum albumin (BSA), respectively. The detection limits were 0.02, 0.01, 0.02 for gamma-IgG, HSA and BSA, respectively. The method has been applied to analyze the total proteins in human samples and the results were in good agreement with those reported by the hospital. This method is sensitive, simple and potential in many areas.