Navegando por Palavras-chave "Filmes Langmuir-Blodgett"

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    Influência do óxido de grafeno em filmes de Langmuir-Blodgett de fosfolipídio para a nano e biotecnologia de biossensoriamento e armazenamento de energia
    (Universidade Federal de São Paulo (UNIFESP), 2021) Scholl, Fabio Antonio [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo
    Bioinspired systems are an interesting alternative for incorporating biomolecules and bioactive species, enabling a favorable environment, for example, for the specificity of enzymes. Particularly, graphene oxide (GO) incorporated in devices containing enzymes can give them additional or improved properties, influencing the optical and electrical properties of the device. This idea can then be extended to the study of enzymatic activity and energy storage of devices formed by enzymes and GO, aiming at applications in biosensors and supercapacitors, respectively. With these ideas in mind, in this work, the coincorporation of the enzyme penicillinase and GO in Langmuir films of dimyristoyl phosphatidic acid phospholipid (DMPA) was studied, as well as the transfer of the floating hybrid monolayers to solid supports using the Langmuir-Blodgett technique (LB), aiming at the formation of active layers that could be used as electrodes of supercapacitors. The incorporation of the enzyme and GO was evaluated through measurements of surface pressure and surface potential-area isotherms, surface compressibility, Brewster angle microscopy (BAM), and Infrared Absorption and Reflection Spectroscopy with Modulated Polarization (PM-IRRAS). The Langmuir films were stable, and the morphology of the films observed by BAM, as well as the isotherms’ profile, and the vibrational spectra indicated the incorporation of penicillinase, as well as the interaction of graphene oxides in suspension, with the monolayer. The LB films were evaluated by fluorescence spectroscopy, PM-IRRAS, and morphology by Atomic Force Microscopy (AFM) and tested for enzymatic activity by spectroscopy in the ultraviolet-visible (UV-Vis) region. The immobilization was effective, and the GO cotransfer improved performance in detecting penicillin using electrical and optical signals. The presence of the enzyme was detected by electronic excitation and fluorescent emission, being more expressive in a more significant number of layers. The presence of GO increased the penicillin G detection devices' catalytic activity by 22% in LB films with one layer and by 36% in LB films with five layers. The morphology of the samples showed heterogeneity and greater roughness with the incorporation of the enzyme and GO, facilitating the permeability of the analyte to the active sites of penicillinase. ITO / DMPA-GO-MnO2 electrodes were subjected to cyclic voltammetry and galvanostatic charge and discharge measurements, which showed capacitive properties allowed by incorporating the GO MnO2 species. The results showed relevant aspects that can be considered in the proposal to develop or improve electrochemical biosensors and supercapacitors.
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    Interação da enzima Beta-galactosidase em filmes lipídicos e poliméricos de Langmuir e Langmuir-Blodgett
    (Universidade Federal de São Paulo (UNIFESP), 2019-11-29) Araujo, Felipe Tejada [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    In this work we studied the interaction of β-galactosidase in Langmuir and Langmuir-Blodgett (LB) films of stearic acid (HSt) and poly (9,9-dioctylfluorene) -co-thiophene polymer (PDF-TF). The lipid was spread at the air-water interface forming Langmuir monolayers and the enzyme was inserted into the supporting aqueous phase of the lipid monolayer. The adsorption of the enzyme to the monolayer was studied by surface-area pressure isotherms, surface-area potential isotherms, Brewster angle microscopy and vibrational spectroscopy. The mixed monolayer (lipid / enzyme / polymer) was transferred to solid supports by the LB methodology and characterized by luminescence spectroscopy, vibrational spectroscopy, and atomic force microscopy, indicating the presence of the polymer and the enzyme. The enzymatic activity of immobilized lactase as LB film was evaluated against lactose hydrolysis was evaluated with UV-visible spectroscopy. In conclusion, the enzyme can be inserted into lipid films, partially maintaining its secondary structures and altering the morphology of LB films. Catalytic activity could be maintained at up to 60% of activity after one month after transfer to LB film, which makes the system viable for future applications in lactose biosensors.