Development of a microbiosensor based on immobilized living chromatophores of Siamese fighting fish, Betta splendens, for the detection of microbial and environmental toxins is described in this paper. Chromatophores were immobilized on ferromagnetic gelatin microbeads (d=250 m). Kinetics of cell attachment, immobilization efficiency, population density, and an optimum content of ferromagnetic powder (iron(II,III) oxide, dp<5 m) with respect to preservation of the viability of cells was

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... The rate of cell attachment to the gelatin microbeads followed first-order kinetics with attachment efficiency of more than 95 %. Pretreatment of beads with fibronectin, known as a cell attachment promoting agent, resulted in a 10 % increase of the attachment rate constant compared to the attachment rate constant obtained without fibronectin. A detrimental effect on cell viability was observed when more than 10 % of ferromagnetic material was added to the beads. Operation of microbiosensor was tested with the neurotoxin analog clonidine as a model toxin. A double-exponential model is proposed to describe the toxin-induced change of cell area covered with pigment. Experimental data fitted well the proposed model.