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Abstract-ZnO nano-rods grown by gaseous-disperse synthesis (GDS) are confirmed by XRD analysis to have the wurtzite crystal structure. The obtained crystallites, as found from SEM studies, are 57±9 nm in diameter and 470±30 nm long on the average. Two emission bands of photoluminescence from ZnO nano-rods observed at room temperature are centered at 376 nm and 520 nm. A bio-sensitive layer is prepared by immobilization of Anti-Salmonella antibodies (Ab) from liquid solutions on the ZnO surface. Immobilization of the bio-sensitive layer onto ZnO nano-rods is found to increase the intensity of PL. After further reaction with Salmonella antigens (Ag) the PL intensity is found to decrease proportional to antigen concentrations in the range of 1000 -1000000 cell/ml. The possible mechanism of biosensor response is suggested and discussed.

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Bovine leukaemia virus (BLV) proteins gp51, which are serving as antigens for specific antibodies against BLV proteins (anti-gp51), were applied as biological recognition part in the design of immunosensor devoted for the determination of anti-gp51. The efficiency of the immobilization of BLV proteins gp51 on ZnO nanorod (ZnO-NR) modified glass (ZnO-NR/glass) surface was evaluated. The formation of antigen-antibody complex on the ZnO/glass modified by the BLV proteins gp51 (gp51/ZnO-NR/glass) was investigated by the determination of changes in ZnO photoluminescence. The applicability of gp51/ZnO-NR/glass in the design of photoluminescence based immunosensor was evaluated. Bovine serum albumin (BSA) was applied for the modification of sensing gp51 layer in order to form gp51&BSA layer with advanced selectivity. Polyallylamine hydrochloride (PAH) was applied in order to improve the immobilization of gp51 and BSA based sensing layer (gp51&BSA) on the surface of ZnO-NR/glass. PAH was applied during the formation of gp51&BSA/PAH/ZnO-NR/glass structure. Some aspects of the mechanism of interaction between biomolecules (gp51, BSA and anti-gp51) and ZnO-NR during the preparation and action of gp51&BSA/ZnO-NR/glass-and gp51&BSA/PAH/ZnO-NR/glass-based immunosensors have been discussed.

Quality control of food and agriculture production is an inseparable part of human safety and well-being. Salmonella infections belong to one of the most monitored pathogens in the world, therefore advanced determination of this pathogen can decrease the risks of human diseases caused by this microorganism. In this research we introduce a novel optical immunosensor for determination of Salmonella typhimurium. The immunosensor is based on Titanium dioxide (TiO2) nanoparticles deposited on glass substrates (glass/TiO2). TiO2 nanoparticles exhibit an intense photoluminescence (PL) in the visible range of spectrum at room temperature. The direct immobilization of antibodies (anti-S-Ab) against Salmonella antigens on the surface of glass/TiO2 has resulted in the formation of glass/TiO2/anti-S-Ab-based structure, which was characterized by increased PL intensity and IR-shifted position of the PL peak in comparison to the same characteristics of glass/TiO2-based structure. The changes of the PL intensity and peak positions after interaction of the immobilized anti-S-Ab with Salmonella antigens (Salmonella-Ag) were used as immunosensor signal, allowing sensitive and selective detection of Salmonella-Ag in a label-free configuration. The sensitivity of the reported optical immunosensor towards Salmonella-Ag is in the range from 10 3 to 10 5 cell/ml. Some aspects of the interaction between TiO2 and biological compounds have been discussed. This work opens up new possibilities for 1 the development of optical label-free immunosensors suitable for fast, simple and efficient analysis of Salmonella infections.

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