Browsing by Subject "Body fluids"

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    Biocatalytic protein membranes fabricated by electrospinning
    (Elsevier B.V., 2016) Kabay, G.; Kaleli, G.; Sultanova, Z.; Ölmez, T. T.; Şeker, U. Ö. Ş.; Mutlu, M.
    In this study, a protein-based catalytic membrane was produced by electrospinning. Membrane activity was characterised in terms of response current for various glucose concentrations. We focused on the preparation of a scaffold by converting a globular protein to other structural forms using catastrophic solvents. A scaffolding protein, bovine serum albumin, and an enzyme, glucose oxidase (GOD), were selected as a model natural carrier matrix and a biologically active agent, respectively. Beta-mercaptoethanol (β-ME) was used to convert the globular protein to an amyloid-like form. A structural stabilising agent, 2,2,2-triflouroethanol (TFE), was used to maintain the final α-helical structure of the amyloid-like protein. The TFE:PBS (phosphate-buffered saline) ratio and various electrospinning parameters were analysed to minimise activity loss. Using this approach, we applied electrospinning to an active enzyme to obtain biocatalytic nanofibrous membranes. After optimising the protein electrospinning process, the activities of the protein nanofibrous membranes were monitored. GOD remained active in the new membrane structure. The highest enzyme activity was observed for the membranes prepared with a 1.5:1 (v:v) TFE:PBS solvent ratio. In that particular case, the immobilized enzyme created a current of 0.7 μA and the apparent activity was 2547 ± 132 U/m2.
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    ItemOpen Access
    pH-dependent ionic-current-rectification in nanopipettes modified with glutaraldehyde cross-linked protein membranes
    (Royal Society of Chemistry, 2016) Şen, M.; Demirci, A.
    In this study, we investigated for the first time the influence of an artificial membrane on the ionic current rectification of nanopipettes at various pH levels. The nanopipettes were fabricated and then modified with bovine serum albumin-glutaraldehyde (BSA-GA) artificial membranes. We determined the degree of ionic current rectification of these nanopipettes and compared them with those of bare nanopipettes. In contrast to the bare nanopipettes, the BSA-GA-modified nanopipettes demonstrated pH-dependent ionic current rectification. We also examined the tunability of the degree of rectification using streptavidin (STV) whose isoelectric point differs from that of BSA. The results showed that the ionic current rectification of nanopipettes can be tuned as the addition of STV into the BSA-GA artificial membrane increases the degree of rectification. Using the proposed approach, nanoscale spearhead pH sensors could be fabricated for highly localized extracellular or intracellular pH measurement. Moreover, it is possible to realize the applications of nano-sized channels in relatively larger channels using the present method.