title: Tunneling of redox enzymes to design nano-probes for monitoring NAD(+) dependent bio-catalytic activity.
abstract: Monitoring of bio-catalytic events by using nano-probes is of immense interest due to unique optical properties of metal nanoparticles. In the present study, tunneling of enzyme activity was achieved using redox cofactors namely oxidized cytochrome-c (Cyt-c) and Co-enzyme-Q (Co-Q) immobilized on Quantum dots (QDs) which acted as a bio-probe for NAD(+) dependent dehydrogenase catalyzed reaction. We studied how electron transfer from substrate to non-native electron acceptors can differentially modify photoluminescence properties of CdTe QDs. Two probes were designed, QD-Ox-Cyt-c and QD-Ox-Co-Q, which were found to quench the fluorescence of QDs. However, formaldehyde dehydrogenase (FDH) catalyzed reduction of Cyt-c and Co-Q on the surface of QDs lead to fluorescence turn-on of CdTe QDs. This phenomenon was successfully used for the detection of HCHO in the range of 0.01-100,000ng/mL (LOD of 0.01ng/mL) using both QD-Ox-Cyt-c (R(2)=0.93) and QD-Ox-Co-Q (R(2)=0.96). Further probe performance and stability in samples like milk, wine and fruit juice matrix were studied and we could detect HCHO in range of 0.001-100,000ng/mL (LOD of 0.001ng/mL) with good stability and sensitivity of probe in real samples (R(2)=0.97). Appreciable recovery and detection sensitivity in the presence of metal ions suggests that the developed nano-probes can be used successfully for monitoring dehydrogenase based bio-catalytic events even in the absence of NAD(+). Proposed method is advantageous over classical methods as clean up/ derivatization of samples is not required for formaldehyde detection.
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Food Technological Research Institute (CFTRI), Mysuru 570020, India; Microbiology & Fermentation Technology Department, CSIR-Central Food Technological Research Institute (CFTRI), Mysuru 570020, India.
authors.forename: Uchangi Satyaprasad
authors.initials: US
authors.lastname: Akshath
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Food Technological Research Institute (CFTRI), Mysuru 570020, India; Microbiology & Fermentation Technology Department, CSIR-Central Food Technological Research Institute (CFTRI), Mysuru 570020, India. Electronic address: praveena@cftri.res.in.
authors.forename: Praveena
authors.initials: P
authors.lastname: Bhatt
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D019187:Cadmium Compounds / Q000737:chemistry; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D005504:Food Analysis / Q000379:methods*; D005557:Formaldehyde / Q000032:analysis*; D000067030:Fruit and Vegetable Juices / Q000032:analysis; D008892:Milk / Q000737:chemistry; D009243:NAD / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D045663:Quantum Dots / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry; D014451:Ubiquinone / Q000737:chemistry / Q000378:metabolism; D014920:Wine / Q000032:analysis
chemical_list: D019187:Cadmium Compounds; D004800:Enzymes, Immobilized; D009243:NAD; D014451:Ubiquinone; D005557:Formaldehyde; D045304:Cytochromes c; D000445:Aldehyde Oxidoreductases; C087006:formaldehyde dehydrogenase, glutathione-independent; D013691:Tellurium; C028337:cadmium telluride
keywords: Co-enzyme-Q; Cytochrome-c; Formaldehyde detection; Quantum dots; Redox enzymes