Browsing by Author "Velinov T."

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    Effects of the flow type on the immobilization of Horseradish peroxidase on polymers
    (2018-01-01) Yaneva S.; Velinov T.; Yotova L.
    This paper presents the investigation of Horseradish peroxidase (HPR) immobilization on poly-(acrylonitrile- co-acrylamide) and polyamide membranes using three different regimes of a fluid movement: a turbulent, a laminar and an intermediate one. The turbulent movement of the liquid is realized through a magnetic stirrer application. The laminar flow is achieved in a microfluidic system, while the attached amount of enzymes is monitored by a quartz crystal microbalance (QCM). The third type of movement, a fluid movement in an inclined pipe with a varied angle of inclination, is realized in a laboratory made rig. We find that the type of flow influences the immobilized enzyme amount, the time of the immobilization and the structure of the immobilized film. The main conclusion is that the laminar flow favours the process of covalent immobilization most probably because of the orientation of the molecules and their movement parallel to the carrier surface.
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    IN SITU INVESTIGATION OF TYROSINASE IMMOBILIZATION ON POLY-(ACRYLONITRILE- CO-ACRYLAMIDE) BY QUARTZ CRYSTAL MICROBALANCE
    (2021-01-01) Yaneva S.; Velinov T.
    In this paper, we report the results of the covalent immobilization of tyrosinase onto polymer based on poly-(acrylonitrile-co-acrylamide) poly-(AN-co-AM) using two methods - in a microfluidic cell with quartz crystal microbalance (QCM) detection and in self-constructed laboratory immobilizer. Poly-(AN-co-AM) is a well-known polymer for enzyme immobilization which is low cost, easy for manipulation and with good chemical stability. This polymer is also biocompatible, insoluble in water, contains suitable functional groups for covalent immobilization, and can easily be deposited as thin layer. The results from Fourier-transform infrared spectroscopy show two sharp absorption peaks at 2243 cm-1 and 1690 cm-1 are attributed to stretching of -CN and -CONH2 groups, respectively, and are related to the covalent binding between the enzyme and the polymer. Spin-coating method was used for thin film deposition. The prepared polymer layer was less than 100 nm thickness. A QCM was used to monitor the amount of protein attached to the sensor surface during the laminar liquid flow in the microfluidic cell. Scanning Electron Microscopy and Atomic Force Microscopy show the stages of covering of quartz resonator surface by enzyme.