Pogorilyi R. Urease in hybrid polysiloxane matrices: immobilization, properties, applications

The technique of urease immobilization on hybrid polysiloxane matrices was developed. It has been witnessed that the introduction of the enzyme during the xerogel formation leads to the loss of its activity, whereas adsorption on the ready maid carriers preserves activity of the enzyme. The residual activity of urease immobilized on mercapto-containing matrix is the highest. It has been shown that the modification of SBA-15 type materials using silanes with diffent functional groups does not change the internal structure of the carriers. The affinity of the surface groups to urease increases in the row ОН<-SH<=NH<-NH2, whereas the value of adsorption varies in the line =NH<OH<-NH2 <-SH with residual activity of enzyme exceeding 80%. The technique for the synthesis of composites based on magnetite nanoparticles with of mono- or bifunctional organopolysiloxane layers with urease immobilized at 100-600 mg/g was suggested. It was determined that increasing length of the alkyl radical in the amine-containing bifunctional layers increases the value of enzyme adsorption. It was shown that urease formulation on the basis of mercapto-containing composite carriers provides high performance of urea hydrolysis process. Such urease formulations can be used without significant loss of their characteristics, at least in 40 cycles of urea hydrolysis. In addition, it was revealed that such immobilization of enzyme by its adsorption on magnetite provides an increasing stability of the formulation to heavy metal ions. The reduction of the enzyme activity is linear, which can be used to develop sensor systems and for other analytical purposes.