The goal of this work was to quantify the mechanical properties of cellulose nanocrystal (CNC)-based thin films using a polystyrene (PS) structuring approach. This structuring approach was used to biaxially wrinkle CNC-polymer and all-CNC films, in order to assess how changes in the film fabrication process affected the elastic modulus of these films. All films were prepared on pre-stressed PS substrates and structured by heating them above the glass transition temperature of PS, which caused the substrates to shrink and the films to wrinkle biaxially. CNC-polymer films were prepared using the layer-by-layer approach, where three parameters were modified to obtain films of varying compositions: 1) type of polymer (xyloglucan, XG, or polyethyleneimine, PEI), 2) polymer concentration (0.1 wt% or 1 wt%), and 3) film thickness (i.e., number of deposited bilayers). After these films were structured, their elastic moduli were calculated to be 70 ± 2 GPa for CNC-XG0.1, 72 ± 2 GPa for CNC-PEI0.1, and 32.2 ± 0.8 GPa for CNC-PEI1.0 films, indicating that the mechanical properties of CNC-polymer films changed with film composition. This structuring method was also found to provide a humidity-independent measurement of the modulus due to the irreversible nature of the wrinkling. Next, to prepare all-CNC films, CNC suspensions were evaporated under conditions designed to control the film thickness (using 0.005 wt% – 8 wt% CNC suspensions) and CNC nanoparticle orientation (chiral nematic, isotropic, or uniaxial). Suspensions were dried slowly under vacuum, quickly by heating, or by spin-coating to form films with chiral nematic, isotropic, or uniaxial (radial) CNC orientations, respectively. Following structuring, these wrinkled films showed unique morphologies that changed with nanoparticle orientation, suggesting that their mechanical properties are dependent on the CNC orientation within the films. The work presented in this thesis implies that the mechanical properties of films fabricated from hygroscopic bio-based nanomaterials can be assessed in a humidity-independent way by using the structuring method presented. Quantifying the mechanical properties of these films is critical to assess the potential applications of CNCs, where CNC-based materials may be used in developing paper-based electronics, extracellular matrix mimics, and plant cell wall mimics. / Thesis / Master of Science (MSc)

Organic materials exhibiting second-order non-linear optical (NLO) properties are a key to the development of advanced electro-optic (EO) modulators used in fiber-optic communications system. This work addresses the fabrication and characterization of organic materials with NLO properties using a self-assembly approach by alternately dipping a charged substrate into positively and negatively charged polymers to build up layer-by-layer (LbL) films. The effect of solution pH on the formation of LbL films fabricated using the polycation poly(allylamine hydrochloride) (PAH) and the polyanion poly{1-[p-(3–-carboxy-4–-hydroxyphenylazo)benzenesulfonamido]-1,2-ethandiyl} (PCBS) was studied using a quartz crystal microbalance with dissipation (QCM-D) monitoring, ellipsometry, absorbance, and second harmonic generation (SHG) measurements. PCBS has an azo-benzene chromophore side group that, when sufficiently oriented, results in measurable SHG. Films of PAH/PCBS fabricated at neutral pH where both PAH and PCBS are highly charged led to thin bilayers, ~1 nm, with a 1:1 molar ratio of PCBS:PAH. This molar ratio was found to be important for long-range polar ordering of PCBS in these films. Increasing the rate of convection was found to reduce the time required for complete adsorption of the polyion. This can have a significant impact on fabrication of films with high bilayer numbers. A variation of the above technique, which involves adsorbing one of the constituents electrostatically and another covalently, was studied using PAH and a reactive dye, Procion Brown (PB), which has a significantly higher hyperpolarizability than PCBS. It was found that a high pH, ~10.5, was important for achieving covalent attachment of the PB to the underlying PAH films. This resulted in much higher SHG intensities compared to when PB was deposited pH at 8.5-9.5 where the attachment of PB was due to a combination of electrostatic and covalent interactions. QCM-D results for PAH/PB films revealed the presence of a high percentage of unreacted amine groups in the underlying PAH film. A rate constant value for PB attachment step to the underlying PAH was also calculated. To enhance the SHG intensity of these films, silver nanoprisms were synthesized and deposited onto films using physisorption. An enhancement in the SHG intensity was observed for both PAH/PCBS and PAH/PB films. / Ph. D.

DNA is the substance that encodes the genetic information that cells need to replicate and to produce proteins. The detection of DNA sequences is of great importance in a broad range of areas including genetics, pathology, criminology, pharmacogenetics, public health, food safety, civil defense, and environmental monitoring. However, the established techniques suffer from a number of problems such as the bulky size, high equipment costs, and time-consuming algorithms so that they are limited to research laboratories and cannot be applied for in-vivo situations. In our research, we developed a novel sensing scheme for DNA sequence detection, featuring sequence specificity, cost efficiency, speed, and ease of use. Without the need for labels or indicators, it may be ideal for direct in-cell application. The principle is simple. With capture DNA immobilized onto the probe by layer-by-layer selfassembly, the hybridization of a complementary strand of target DNA increases the optical thickness of the probe. Three kinds of sensors were developed. The optical fiber tip sensor has been demonstrated with good specificity and high sensitivity for target DNA quantities as small as 1.7 ng. To demonstrate the potential of this structure for practical applications, tularemia bacteria were tested. Two other micrometric structures were designed with specific advantages for different applications. The micro-fiber Bragg grating interferometer (Micro-FBGI) has the intrinsic temperature compensation capability. The micro-intrinsic Fabry-Perot interferometer (Micro-IFPI)features simple signal processing due to its simple configuration. Successful DNA immobilization and hybridization have been demonstrated onto the 25μm Micro-IFPI. Both structures have great potential for nanometric protrusion, allowing future in-cell DNA direct detection. In addition, its quick response time leads to the potential for express diagnosis. What's more, the idea of nanoscale probe has a broad impact in scanning near-field optical microscopy (SNOM), intracellular surgery in cell sensing, manipulation, and injection. / Ph. D.

In order to achieve efficient therapeutic effect, it is important to understand the structure of biomaterials that are used in the therapeutic delivery system. This dissertation is dedicated towards understanding the hydrolysis pattern of plasmid DNA (pDNA) delivery vehicles comprised of poly(glycoamidoamine)s (PGAAs) under physiological conditions and effects of subtle changes in the chemical structure of the PGAAs on its biological performance. The unusual hydrolysis of the tartarate and galactarate based PGAAs was investigated by studying the hydrolysis of small model molecules which mimic the repeat unit of the respective polymers. In the case of galactarate and tartarate based molecules with terminal amines showed faster hydrolysis of the amide bonds. In addition for the tartarate based compounds, it was also found that it is necessary to have terminal amine functionality for the intramolecular hydrolysis to occur. The model compounds consists of two amide bonds and were designed symmetric, however amide bond on only one side of the tartarate moiety show underwent hydrolysis. Further studies show that one side of the amine assists the hydrolysis of the amide bond on the other side of the tartarate moiety. The degradation of poly(L-tartaramidopentaethylenetetramine) (<strong>T4</strong>) was also used to study the sustained release of pDNA from the layer-by-layer constructs of <strong>T4</strong>/pDNA. The thickness of the constructs was characterized by ellipsometry while the UV-visible spectroscopy was used to characterize the loading capacity of the constructs for pDNA. The indirect sustained release of pDNA under the physiological conditions with respect to time was characterized by the cellular uptake studies in HeLa cells. The increase in the uptake of the Cy5 labeled pDNA was seen at extended period of eleven days. The integrity of the sustained released pDNA for the transgene expression was characterized with an assay to see the expression of the green fluorescent protein (GFP) from the <strong>T4</strong>/GFP-pDNA layer-by-layer constructs. PGAAs show a very efficient delivery of the pDNA in a non-toxic manner. The chemical structure of the polymer can dictate the binding with pDNA and also the release of the pDNA form the polymer-pDNA complexes. In order to better understand the fundamentals of the nucleic acid delivery and to better design the nucleic acid delivery vehicles, subtle changes in the chemical structure of the PGAAs were designed and studied for the biological activity. The effect of charge type was investigated by designing and synthesizing guanidine based polymer series analogues to galactarate and tartarate based PGAAs (<strong>G1</strong> and <strong>T1</strong>) which incorporate secondary amines as the charge type on the polymer backbone. The guanidine based polymer series, poly(glycoamidoguanidine)s (PGAGs), show very non toxic behavior in HeLa cells at all the different polymer to pDNA ratio (<i>N/P</i> ratio) studied. Interestingly PGAGs are the only non-toxic guanidine containing polymers which are reported in the literature to the date. The cellular uptake of pDNA assisted from the PGAGs is a little higher than PGAAs compared although both the series of polymers show similar transgene expression. The transgene expression in case of PGAGs also imply the release of the polymer-pDNA complexes from the endosome. In another study of structure-bioactivity relationship based on the degree of polymerization (DP) of poly(galactaramidopentaethylenetetramine) (<strong>G4</strong>), it was found that the increase in the DP of <strong>G4</strong> increases the toxicity of the polymers in the HeLa cells. / Ph. D.

Ionic self-assembled multilayer (ISAM) thin film nanostructures, including highly porous and conductive gold nanoparticles (GNP), and highly porous and thermally stable silica nanoparticles (SNP), were fabricated via the layer-by-layer (LbL) self-assembly technique. Their application in ionic polymer-metal composite (IPMC) electromechanical bending actuators and microfabricated gas chromatography (microGC) devices were investigated and significant performance improvements of these devices were achieved. IPMC bending actuators, consisting of an ionic electroactive polymer (iEAP) membrane as backbone, ionic liquids (IL) as electrolyte, and ISAM GNP thin film as porous electrode, were fabricated and investigated. The influences of humidity, conductive network composite (CNC), and IL uptake on the bending performance were examined and discussed. An equivalent circuit model to simulate both the electrical and mechanical responses was also proposed and experimentally verified. Moreover, IPMC actuators made from other newly synthesized iEAP membranes were fabricated and tested. Some of them showed promising performance that was comparable or even better as compared to the ones made from Nafion. LbL fabricated ISAM SNPs thin film coatings were also applied in the microGC devices including micro fabricated thermal preconcentrators (microTPC) and separation columns (microSC) as adsorbent and stationary phase materials, respectively. New fabrication approaches were developed to selectively coat uniform conformal ISAM SNP coatings in these devices with different 3D microstructures. Thus, functionalized microTPCs and microSCs showed good performance, which can be further improved by using the ISAM SNPs coating as a nanotemplate for modifying additional polymer adsorbents or as the anchor sites for incorporating functional molecules for targeting detection. / Ph. D.

Yes / Creation of functional skin substitutes within a clinically acceptable time window is essential for timely repair and management of large wounds such as extensive burns. The aim of this study was to investigate the possibility of fabricating skin substitutes via a bottom-up nanofiber-enabled cell assembly approach and using such substitutes for full-thickness wound repair in nude mice. Following a layer-by-layer (L-b-L) manner, human primary skin cells (fibroblasts and keratinocytes) were rapidly assembled together with electrospun polycaprolactone (PCL)/collagen (3:1 w/w, 8% w/v) nanofibers into 3D constructs, in which fibroblasts and keratinocytes were located in the bottom and upper portion respectively. Following culture, the constructs developed into a skin-like structure with expression of basal keratinocyte markers and deposition of new matrix while exhibited good mechanical strength (as high as 4.0 MPa by 14 days). Treatment of the full-thickness wounds created on the back of nude mice with various grafts (acellular nanofiber meshes, dermal substitutes, skin substitutes and autografts) revealed that 14-day-cultured skin substitutes facilitated a rapid wound closure with complete epithelialization comparable to autografts. Taken together, skin-like substitutes can be formed by L-b-L assembling human skin cells and biomimetic nanofibers and they are effective to heal acute full-thickness wounds in nude mice.

Des couches fonctionnelles hybrides organiques/inorganiques ont été générées à une interface solide/liquide à l’aide d’une nouvelle technique de fabrication ascendante (bottomup) dénommée Croissance de Couche à partir d’une Surface (Surface Grown Layers - SgL)grâce à une modulation très fine de l’interaction électrostatique entre nano-objets decharges opposés en fonction de la force ionique de la dispersion aqueuse. Différents nanoparticules/tubes à la fois cationiques et anioniques et très stables vis-à-vis d’un environnement fortement salin ont été développés. La complexation électrostatique entre ces nanomatériaux a été étudiée en solution et près d’une interface au travers du concept de “transition de dessalage”. Dans un deuxième temps la croissance de couches hybrides à partird’un substrat a été étudiée en comparant l’approche SgL et la méthode classique d’adsorption séquentielle couche par couche (Layer by layer - LbL). Des expériences préliminaires ont montré le potentiel de cette approche dans le développement de substrats fonctionnels. / In this manuscript, one-step bottom-up fabrication of “smart organic-inorganic hybridfunctional layers” at a liquid/solid interface were fabricated via a novel surfacefunctionalization pathway termed as “Surface Grown Hybrid Functional Layers” or SgLthrough fine tuning of electrostatic interaction between “highly stable” and oppositelycharged nanomaterials as a function of ionic strength of the dispersion. Cationic and anionicnanomaterials based on different hybrid nanoparticles/nanotubes that are very stable towardshigh saline environment have been formulated. The electrostatic complexation between theseoppositely charged nanomaterials has been studied in bulk and at an interface through theconcept of “desalting transition” pathway. In a second step, the growth of functional hybridlayers directly from a substrate via the novel SgL approach was then compared with theconventional Layer-by-Layer approach (LbL). Finally the preliminary experiments haveshown the potential applications of generated functional surfaces.

A soja é um produto de grande importância para a economia brasileira, pois o Brasil é o segundo produtor mundial de soja. Sua aplicação mais conhecida é como óleo refinado, entretanto, a soja é bastante utilizada nas mais variadas indústrias. Do ponto de vista nutricional, a soja se destaca por possuir um alto valor protéico, sendo por isso muito empregada em indústrias alimentícias. Porém, os produtos alimentícios a base de soja ainda enfrentam uma grande resistência por parte dos consumidores. Esta resistência do mercado consumidor tem motivado os produtores de soja e as indústrias a buscarem o desenvolvimento de grãos com características especiais. Este trabalho auxilia nesta busca, pesquisando um método capaz de discriminar cultivares de soja fornecidos pela Embrapa Soja através da utilização de uma Língua Eletrônica (LE). A Língua Eletrônica é um sistema multissensorial composto por um conjunto de sensores não-específicos que respondem diferentemente para cada analito, sendo capaz de reconhecer e diferenciar amostras através da obtenção de impressões digitais destas. Neste trabalho, os sensores da Língua Eletrônica foram construídos a partir de filmes automontados de polímeros condutores. Foram realizados testes de repetibilidade e reprodutibilidade, além do estudo de sensibilidade dos sensores que compõem o sistema multissensorial. A Língua Eletrônica construída mostrou-se capaz de diferenciar os cinco cultivares estudados, especialmente aqueles que possuíam características notadamente distintas. Foram observadas variações das medidas ao longo dos dias, o que foi atribuído a uma possível degradação dos grãos de soja e do extrato de soja preparado. Foi proposto ainda um método alternativo de preparação do extrato de soja sem a utilização de tratamento térmico. Devido ao seu bom desempenho nos estudos citados, a Língua Eletrônica se mostrou viável para o emprego em uma pré-seleção de cultivares de soja. / Soy is a commodity of great importance to the Brazilian economy since Brazil is the second biggest producer of soy in the world. Soybeans are usually employed in the production of refined oil for cooking as well as in many other foodstuff industries due to its high protein content. However, foodstuffs based on soy still face some resistance by consumers mainly because of the characteristic soy taste imposed to their respective products. This actual scenario has motivated producers and foodstuff industries to develop new soybeans varieties with improved and more pleasant taste. This work was intended to provide a methodology based on an electronic tongue system (ET) in order to help both producer and industries to develop and identify different soybean cultivars. Different soybeans cultivars developed by Embrapa Soja were evaluated by the ET. The ET is a multisensorial system composed by an array of non-specific, layer-by-layer assembled conducting polymer chemical sensors, which display distinct electrical fingerprints to different samples. The distinct responses make the ET capable to distinguish as well as recognize different samples when previously trained. The sensitivity, repeatability and reproducibility of chemical sensors responses to soybeans liquid extracts were evaluated and confirmed by exhaustive cyclic operation. The ET was indeed able to discriminate 5 different soybeans cultivars, in particular those with pronounced distinct properties. It was observed a systematic variation on the ET responses in a same day of analysis as well as for prolonged days which we have attributed to possible degradation of raw soybeans and its respective liquid extracts. An alternative procedure for soybean extract preparation absent of cooking was developed. The remarkable performance of the ET makes the system of great potential to perform the pre-selection of soybeans cultivars, with reliability and output.

Made available in DSpace on 2017-07-24T19:38:05Z (GMT). No. of bitstreams: 1 RolfIntema.pdf: 3696203 bytes, checksum: 9dabc8dc5e71a01ee4c010a743e2f479 (MD5) Previous issue date: 2011-03-04 / Nanocomposites in the form of ultrathin films with bilayer and tetralayer structure using the polyelectrolyte chloride 3-n-propyl-1-azonia-4-azabicyclo [2.2.2] octane silsesquioxane (designated as SiDb+Cl-) or polyelectrolyte chloride 3-n-propylpyridinium silsesquioxane (designated as SiPy+Cl-) and tetrasulfonated nickel phthalocyanine (NiTsPc), together with a natural polysaccharide, were produced using the Layer-by-Layer (LbL) technique on a FTO substrate (tin oxide doped with fluorine). The formation of the films was monitored by UV-VIS spectroscopy, accompanying the Q band of phthalocyanine. It was observed that for all the films studied that the absorbance of the Q band at 620 nm linearly increased with the number of bilayers indicating that the same amount of material is adsorbed to each bi/tetralayers prepared. It was also observed that the spectra of the films (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc) and SiDb+Cl /Goma/SiDb+Cl-/NiTsPc), the bands related to the monomeric species were more intense when compared to the films obtained without gum, which s an indication that the inclusion of the gum between the layers of the films can proportionate more organized films with higher interaction between the polymeric species. FTIR spectra showed a shift in the band referring to the NiTsPc sulfonic groups indicating that an electrostatic interaction occurs between NiTsPc and the polycations studied. AFM images showed up the interaction between the polycations of the film, which can be notice by the decrease on the films roughness with the increase of the number of bilayers. In this case, when comparing the SiDb+Cl- containing films with SiPy+Cl- ones, it was observed a more considerable decrease in the rugosity values for the SiPy+Cl- films. Results of cyclic voltammetry carried out with these films with architectures (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc), (SiPy+Cl- /NiTsPc), (SiDb+Cl-/Goma/SiDb+Cl-/NiTsPc) and (SiDb+Cl-/NiTsPc) showed a peak related to the aromatic ring of NiTsPc at 1.4 V. The stability as a function of the number of the voltammetry cycles of the electrodes modified with SiPy+Clwas considerably greater than for the SiDb+Cl- films. These films were sensitive to DA detection at different concentrations in a range of 9.9.10-6 molL-1 to 9.1.10-5 mol L-1 with a detection limit of 7.72.10-6 mol L-1 and 8.34.10-6 molL-1 for architectures (SiPy+Cl-/NiTsPc) and (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc), respectively. / Nanocompósitos na forma de filmes ultrafinos com estrutura em bicamadas e tetracamadas, utilizando o polieletrólito cloreto de 3-n-propil-1- azonia-4-azabiciclo[2.2.2] octano silsesquioxano (designado como SiDb+Cl-) ou o polieletrólito cloreto de 3-n-propilpiridínio silsesquioxano (designado como SiPy+Cl-) e ftalocianina tetrassulfonada de níquel (NiTsPc) juntamente com polissacarídeos naturais, foram produzidos utilizando a técnica Layer-by-Layer (LbL) sobre substrato de FTO (óxido de estanho dopado com flúor. A formação dos filmes foi monitorada por espectroscopia na região do UV-VIS, monitorando a banda Q da ftalocianina. Observou-se que a absorbância da banda Q em 620 nm aumentou linearmente com o número de bicamadas depositadas, para todos os filmes estudados indicando que a mesma quantidade de material é adsorvido a cada bi/tetracamada preparada. Pode ser observado que para os espectros dos filmes (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc) e (SiDb+Cl-/Goma/ SiDb+Cl-/NiTsPc), já nas primeiras tetracamadas, as bandas relativas às espécies monoméricas apresentaram-se mais intensas em relação aos filmes sem goma, o que é uma indicação de que a inclusão da goma pode além de proporcionar, maior organização aos filmes, maior interação entre as espécies poliméricas. Espectros de FTIR demonstraram um deslocamento na banda referente aos grupos sulfônicos da NiTsPc, indicando que ocorre uma interação eletrostática entre a NiTsPc e os policátions estudados. Imagens de AFM evidenciaram essa interação, a qual pode ser constatada a partir da diminuição da rugosidade com o aumento do número de bicamadas. Ao comparar os filmes que contêm o policátion SiDb+Cl- com os filmes contendo SiPy+Clobservou- se que houve uma diminuição mais acentuada da rugosidade para os filmes onde SiPy+Cl- estava presente. Resultados de voltametria cíclica realizados com estes filmes com arquiteturas (SiPy+Cl-/Goma/SiPy+Cl -/NiTsPc)n, (SiPy+Cl-/NiTsPc)n, (SiDb+Cl-/Goma/SiDb+Cl-/NiTsPc)n e (SiDb+Cl- /NiTsPc)n apresentaram um pico referente ao anel aromático da NiTsPc em 1,4 V. Os filmes com a goma apresentaram uma maior estabilidade em função do número de ciclos voltamétricos do que os sem a mesma. Os eletrodos modificados com os filmes foram aplicados para determinação de dopamina em uma faixa de concentração de 9,9.10-6 mol L-1 a 9,09.10-5 mol L-1 com um limite de detecção de 7,72.10-6 mol L-1 e 8,34.10-6 mol L-1 para arquiteturas (SiPy+Cl-/NiTsPc)n e (SiPy+Cl-/Goma/SiPy+Cl-/NiTsPc)n, respectivamente.

A imobilização de moléculas de interesse biológico em superfícies sólidas é essencial para uma série de aplicações biotecnológicas. Dentre as técnicas de imobilização, a automontagem camada por camada por adsorção física possui inúmeras vantagens, incluindo condições brandas e fisiológicas de preparação, capacidade de incorporar diferentes biomoléculas, e controle molecular. Nesta tese foram explorados filmes nanoestruturados de materiais de interesse biológico, bem como modelos de membranas, em que foram empregadas a técnica de automontagem e a preparação de lipossomos. Os lipossomos, que serviram como modelos de membrana, foram imobilizados em filmes automontados e sua integridade estrutural foi mantida. Também foram utilizados para incorporar e estabilizar melanina, e então imobilizados em filmes automontados, com preservação da propriedade fluorescente da melanina. A automontagem também foi utilizada para imobilização das enzimas uricase, fitase e colesterol oxidase, alternadas com camadas de polieletrólitos. Estes filmes mostraram bom desempenho como biossensores amperométricos para uricase e fitase, e como biossensores usando espectroscopia de impedância para a fitase e colesterol oxidase. Tais biossensores foram usados para detectar baixas quantidades de ácido úrico, ácido fítico e colesterol, respectivamente. Não houve efeitos de interferentes nos sensores amperométricos devido à utilização de eletrodos previamente modificados com azul da Prússia, que funcionou como mediador redox. A alta sensibilidade e seletividade dos biossensores foram atribuídas à natureza do filme ultrafino e à capacidade de reconhecimento das biomoléculas, respectivamente. Esta abordagem abre caminho para novas tecnologias de dispositivos para diagnósticos clínicos e análises de alimentos, bem como para entender mecanismos de interação da biomolécula com a membrana celular para o desenvolvimento de agentes terapêuticos. / The immobilization of molecules of biological interest on solid surfaces is essential for a number of biotechnological applications. Among the techniques for immobilization the layer-by-layer (LbL) method based on physical adsorption exhibits several advantages, including mild, physiological conditions for film preparation, ability to incorporate different biomolecules and molecular control. In this thesis, nanostructured films made with materials of biological interest were exploited as model membranes, where use was made of the LbL technique and liposomes. The latter, which served as membrane models, were immobilized in LbL films and had their structural integrity preserved. Liposomes were also used to incorporate and stabilize melanin, which were then deposited on LbL films with the fluorescence of melanin being preserved. The LbL method was also used to immobilize the enzymes uricase, phytase and cholesterol oxidase, alternated with layers of polyelectrolytes. These LbL films were employed in amperometric biosensors with uricase and phytase, and in biosensors based on impedance spectroscopy for phytase and cholesterol oxidase. Low amounts of uric acid, phytic acid and cholesterol were detected, respectively. There was no effect from interferents in the amperometric biosensors because the electrodes were previously modified with a layer of Prussian Blue, which acted as a redox mediator. The high sensitivity and selectivity were attributed to the ultrathin nature of the films and the ability of molecular recognition of the biomolecules, respectively. The approaches used here open the way for novel devices for clinical diagnostics and food quality control, in addition to understanding the interaction mechanisms between the biomolecules and the cell membranes, which is important for developing therapeutic agents.