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| Author(s): |
Edson Giuliani Ramos Fernandes
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2012-02-23 |
| Examining board members: |
Valtencir Zucolotto;
Luiz Henrique da Silva Gasparotto;
Sergio Antonio Spinola Machado;
Luiz Henrique Capparelli Mattoso;
Antonio Riul Júnior
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| Advisor: | Valtencir Zucolotto |
| Abstract | |
This thesis describes the preparation, characterization and development of biosensors based on nanostructured films containing immobilized enzymes and metallophthalocyanines. The films were obtained using the Layer-by-Layer (LbL) or Langmuir-Blodgett (LB) techniques. In the first part of the thesis we describe the development of nanostructured thin films containing the enzyme tyrosinase (Tyr) and their use as biosensors for detection of antioxidants molecules (polyphenols), which find applications in the food industry, specialy red wines. The enzyme was incorporated into the mixed LB films of arachidic acid (AA) and lutetium bisphthalocyanine (LuPc2) by injection into the aqueous subphase followed by transference to ITO or Pt electrodes. The representative phenolic compound molecule to be detected was pyrogallol. Cyclic voltammetry studies shown that the biosensor response is highly reproducible with a standard deviation of ca. 2% (n = 4), dynamic range up to 400 \'mü\'M (applied potential of 0.4 V; R2: 0.993), sensitivity of 1.54 \'mü\'A/\'mü\'M.\'CM POT.2\' and detection limit (3 \'sigma\'0/m criteria) of 4.87 x \'10 POT.-2\' \'mü\'M (n = 10). The second part of this thesis focus on the development of electrochemical sensors based on LbL films of poly(allylamine hydrochloride) (PAH) and LuPc2. The purpose of the study was to change the biological material (Tyr) by LuPc2. LuPc2 was used as an artificial enzyme in the quantification of catechol and pyrogallol as representative of phenolic compounds. In voltammetric measurements, the LbL PAH/LuPc2 sensors presented good linearity (R2 = 0.992) in the range up to 500 \'mü\'M with a sensitivity of 90 nA/\'mü\'M and detection limit of 8 \'mü\'M. As revealed by chronoamperometry measurements, the sensors exhibited a wide linear range (R2 = 0.994; response time of 60 s) up to 900 M and detection limit of 37.5 × \'10 POT.-8\' \'mü\'M (sensibility of 20 nA/\'mü\'M) for catechol. Finally, we investigated the fabrication of LbL films based on poly(propylene imine) dendrimer (PPID) and nickel tetrasulfonated phthalocyanine (NiTsPc) as active elements in devices based on field effect transistors (FET). The films were used as sensitive membranes applied as pH and \'H IND.2\'O IND.2\' sensors. It was shown the importance on the LbL technique and its application in FET-based sensors such as the separated and extended gate FET (SEGFET). LBL films based on artificial enzymes exhibit great promise in real applications due to their low cost and simplicity. The use of these films in devices based on SEGFET structures allows miniaturization of the sensors and their production combining conventional microelectronics fabrication and nanotechnological tools. (AU) | |
| FAPESP's process: | 08/01138-8 - Enzymes Immobilization on Sub-Microstructures Plataforms for Biossensor Applications |
| Grantee: | Edson Giuliani Ramos Fernandes |
| Support Opportunities: | Scholarships in Brazil - Doctorate |