Valtencir Zucolotto - Academia.edu (original) (raw)

Papers by Valtencir Zucolotto

As exigências de mercado atuais fazem com que a agroindústria brasileira esteja sempre na busca i... more As exigências de mercado atuais fazem com que a agroindústria brasileira esteja sempre na busca incessante da melhoria dos processos com vistas ao aumento da produtividade, qualidade e competitividade. No mercado internacional de agroprodutos, as exigências por qualidade são ainda maiores, muitas vezes ultrapassando as características do produto em si e englobando o processo de produção, no qual o impacto ambiental das atividades ganha cada vez mais importância. Paralelamente, o foco em procedimentos industriais de sanidade e redução de contaminação biológica, principalmente em processos na indústria alimentícia, vem freqüentemente ganhando destaque, tanto na mídia quanto em trabalhos de pesquisa. Na indústria de polímeros esta é uma preocupação legítima, tanto pelo alto uso destes materiais como embalagens de alimentos como também pelo fato de serem significativamente estáveis, gerando resíduos de difícil degradação, agindo como potenciais vetores de proliferação de microorganismos quando contaminados (seja em processo ou pelo uso) e descartados (PADULA e CUERVO, 2004).

The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of ... more The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of new systems/devices to be fabricated, with properties that may be tuned upon synergistic interactions between the film components. Films produced with the Layer-by-Layer (LbL) technique, in particular, have opened up the way for new approaches in electrochomism, electrocatalysis, bioelectrochemistry and electroanalysis, for organic and inorganic-organic hybrid nanoarchitectures may be achieved. In addition to the fabrication of novel, optimized materials, with the LbL method fundamental processes such as charge transfer mechanisms involving biomolecules and nanoparticles can be investigated at the molecular level. In this paper we highlight the recent trends in the electrochemistry of LbL films, with emphasis on their promising technological applications in sensing/biosensing and electrochromic devices.

Biosensors and Bioelectronics, Feb 1, 2010

This paper brings an overview of the use of nanostructured films in several types of biosensors, ... more This paper brings an overview of the use of nanostructured films in several types of biosensors, with emphasis on the advantageous control of molecular architecture which is typical of the layer-by-layer (LbL) and Langmuir-Blodgett films. Following introductory sections on film fabrication and detection methods, we concentrate on the immobilization of biomolecules on these nanostructured films used in units for biosensing. Important contributions in the literature in biosensors based on electrochemical and optical measurements are highlighted. Furthermore, a discussion is presented on how the concept of electronic tongues has been extended to biosensing, which resulted in increased sensitivity and selectivity. The integration of sensing units with micro-electronics is commented upon, especially in the context of using field-effect transistors (FETs) for biosensing. Examples of LbL and LB films containing proteins, lipids, metallic nanoparticles and carbon nanotubes, which are used for detecting a variety of analytes, will be provided. The prospects for clinical diagnosis with such biosensors are also assessed. Throughout the review, emphasis is placed on the importance of control of molecular architecture, particularly with synergistic combination of organic and inorganic materials. For example, nanostructured films containing capped gold nanoparticles or carbon nanotubes exhibited enhanced performance in biosensing. It is hoped that this survey may assist researchers in choosing materials, molecular architectures, and detection principles, which may be tailored for specific applications.

Journal of Macromolecular Science Part a, 2001

ABSTRACT

Synthetic Metals, Apr 1, 2003

Eprint Arxiv Cs 0611013, Nov 3, 2006

In this paper we introduce the AMADEUS strategy, which has been used to produce scientific writin... more In this paper we introduce the AMADEUS strategy, which has been used to produce scientific writing tools for non-native users of English for 15 years, and emphasize a learn-by-doing approach through which students and novice writers can improve their scientific writing. More specifically, we provide a 9-step recipe for the students to compile writing material according to a procedure that has proven efficient in scientific writing courses.

Journal of Nanoscience and Nanotechnology, Feb 1, 2011

Liposomes have been applied to many fields as nanocarriers, especially in drug delivery as active... more Liposomes have been applied to many fields as nanocarriers, especially in drug delivery as active molecules may be entrapped either in their aqueous interior or onto the hydrophobic surface. In this paper we describe the fabrication of layer-by-layer (LbL) films made with liposomes incorporating the anti-inflammatory ibuprofen. The liposomes were made with dipalmitoyl phosphatidyl choline (DPPC), dipalmitoyl phosphatidyl glycerol (DPPG) and palmitoyl oleoyl phosphatidyl glycerol (POPG). LbL films were assembled via alternate adsorption of the polyamidoamine dendrimer (PAMAM), generation 4, and liposomes containing ibuprofen. According to dynamic light scattering measurements, the incorporation of ibuprofen caused DPPC and DPPG liposomes to become more stable, with a decrease in diameter from 140 to 74 nm and 132 to 63 nm, respectively. In contrast, liposomes from POPG became less stable, with an increase in size from 110 to 160 nm after ibuprofen incorporation. These results were confirmed by atomic force microscopy images of LbL films, which showed a large tendency to rupture for POPG liposomes. Film growth was monitored using nanogravimetry and UV-Vis spectroscopy, indicating that growth stops after 10 bilayers. The release of ibuprofen obtained with fluorescence measurements was slower for the liposomes, with decay times of 9.2 and 8.5 h for DPPG and POPG liposomes, respectively, than for the free drug with a decay time of 5.2 h. Ibuprofen could also be released from the LbL films made with DPPG and POPG liposomes, which is promising for further uses in patches.

Environmental Science and Technology, Aug 1, 2005

Humic acids (HAs), naturally occurring biomacromolecules, were incorporated into nanostructured p... more Humic acids (HAs), naturally occurring biomacromolecules, were incorporated into nanostructured polymeric films using the layer-by-layer (LbL) technique, in which HA layers were alternated with layers of poly(allylamine hydrochloride) (PAH). Atomic force microscopy (AFM) revealed very smooth films, with mean roughness varying from 0.89 to 1.19 nm for films containing 5 and 15 PAH/HA bilayers, respectively. The films displayed electroactivity, with the presence of only one reduction peak at ca. 0.675 V (vs Ag/AgCl). Such a well-defined electroactivity allowed the films to be used as highly sensitive pesticide sensors, with detection of pentachlorophenol (PCP) in solutions at concentrations as low as 10 -9 mol L -1 .

Analytical Chemistry, 2010

The integration of nanostructured films containing biomolecules and silicon-based technologies is... more The integration of nanostructured films containing biomolecules and silicon-based technologies is a promising direction for reaching miniaturized biosensors that exhibit high sensitivity and selectivity. A challenge, however, is to avoid cross talk among sensing units in an array with multiple sensors located on a small area. In this letter, we describe an array of 16 sensing units of a light-addressable potentiometric sensor (LAPS), which was made with layer-by-layer (LbL) films of a poly(amidomine) dendrimer (PAMAM) and single-walled carbon nanotubes (SWNTs), coated with a layer of the enzyme penicillinase. A visual inspection of the data from constant-current measurements with liquid samples containing distinct concentrations of penicillin, glucose, or a buffer indicated a possible cross talk between units that contained penicillinase and those that did not. With the use of multidimensional data projection techniques, normally employed in information visualization methods, we managed to distinguish the results from the modified LAPS, even in cases where the units were adjacent to each other. Furthermore, the plots generated with the interactive document map (IDMAP) projection technique enabled the distinction of the different concentrations of penicillin, from 5 mmol L -1 down to 0.5 mmol L -1 . Data visualization also confirmed the enhanced performance of the sensing units containing carbon nanotubes, consistent with the analysis of results for LAPS sensors. The use of visual analytics, as with projection methods, may be essential to handle a large amount of data generated in multiple sensor arrays to achieve high performance in miniaturized systems.

Biosensors and Bioelectronics, Aug 1, 2009

Silicon-based sensors incorporating biomolecules are advantageous for processing and possible bio... more Silicon-based sensors incorporating biomolecules are advantageous for processing and possible biological recognition in a small, reliable and rugged manufactured device. In this study, we report on the functionalization of field-effect (bio-)chemical sensors with layer-by-layer (LbL) films containing single-walled carbon nanotubes (SWNTs) and polyamidoamine (PAMAM) dendrimers. A capacitive electrolyte-insulator-semiconductor (EIS) structure modified with carbon nanotubes (EIS-NT) was built, which could be used as a penicillin biosensor. From atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) images, the LbL films were shown to be highly porous due to interpenetration of SWNTs into the dendrimer layers. Capacitance-voltage (C/V) measurements pointed to a high pH sensitivity of ca. 55 mV/pH for the EIS-NT structures. The biosensing ability towards penicillin of an EIS-NT-penicillinase biosensor was also observed as the flat-band voltage shifted to lower potentials at different penicillin concentrations. A dynamic response of penicillin concentrations, ranging from 5.0 M to 25 mM, was evaluated for an EIS-NT with the penicillinase enzyme immobilized onto the surfaces, via constant-capacitance (ConCap) measurements, achieving a sensitivity of ca. 116 mV/decade. The presence of the nanostructured PAMAM/SWNT LbL film led to sensors with higher sensitivity and better performance.

Synthetic Metals, Apr 1, 2003

The Journal of Physical Chemistry B, Jul 3, 2003

Nanoscale composites of polyaniline (PANI) and vanadium oxide (V 2 O 5 ) were assembled via the e... more Nanoscale composites of polyaniline (PANI) and vanadium oxide (V 2 O 5 ) were assembled via the electrostatic layer-by-layer (LBL) technique, with a thickness per bilayer of 2.5 nm. Interactions between PANI and V 2 O 5 are maximized in comparison to the usual xerogel films due to the nanostructured nature of the LBL films, in which V 2 O 5 causes PANI to be oxidized. This has been demonstrated in Raman spectroscopy measurements and is consistent with electrochemical data. These strong interactions make the LBL film to display a color that is different from the colors of the individual materials. Furthermore, they promote a cooperative effect that enhances the charge storage capability of the films, with a total charge of 2.25 mC cm -2 for the PANI/ V 2 O 5 LBL films, in comparison with 1.86 mC cm -2 for the sum of the isolated contributions from PANI and V 2 O 5 .

Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel te... more Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel tetrasulfonated phthalocyanine (NiTsPc) from electrochemical and electronic absorption measurements in layer-by-Layer (LbL) films with chitosan in the cationic layers. This was made possible because the chitosan/FeTsPc and chitosan/NiTsPc modified electrodes exhibited a reversible, highly stable electrochemical response, with the voltammetric signal being preserved after several cycles in the range between 0 and 1.0V vs Ag/AgCl. The ionization potential (IP), electroa nity (EA) and energy gap (E g ) were similar for both systems, suggesting that the coordinating metal atom does not play an important role in the elelctronic properties of the immobilized phthalocyanines. Chitosan was found suitable for the cationic layers as it did not affect the electrochemical current appreciably. The anodic peak current varied linearly with the scan rate for chitosan/NiTsPc and chitosan/FeTsPc films, denoting charge transport via electron hopping within the film, typical of a polymer-modified electrode.

The Journal of Physical Chemistry C, Apr 8, 2009

We describe a simple and efficient strategy to fabricate enzymatic devices based on the depositio... more We describe a simple and efficient strategy to fabricate enzymatic devices based on the deposition of glucose oxidase on aligned and highly oriented CoNiMo metallic nanowires. CoNiMo nanowires with an average diameter of 200 nm and length of 50 µm were electrodeposited on Au-covered alumina substrates via electrodeposition, using alumina membranes as templates. Enzyme-modified electrodes were fabricated via enzyme immobilization using a cross-linker. To minimize nonspecific reactions in the presence of interfering agents, a permselective membrane composed of poly(vinylsulfonic acid) and polyamidoamine dendrimer was deposited via electrostatic interaction. The formation of hydrogen peroxide as a product of the enzymatic reaction was monitored at low overpotential, 0.0 V (vs Ag/AgCl). The detection limit was estimated at 22 µM under an applied potential of 0.0 V. The apparent Michaelis-Menten constant determined from the Lineweaver-Burke plot was 2 mM.

Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid... more Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid (HA) and natural rubber latex (NR) extracted from Hevea brasiliensis, were investigated for their cell-attachment interaction with human fibroblast cells. Layer-by-layer (LbL) films with up to 10 bilayers of PAH/HA or PAH/(HA+Latex) were deposited directly on tissue culture polystyrene substrates (TCPS). In control experiments, cast films were fabricated on TCPS using 0.5% (v/v) of fresh latex and 0.5 g/L solutions of HA in different proportions (latex:HA = 10:1, 5:1, 1:1, 1:2). Both PAH/HA and PAH/(HA+Latex) LbL films exhibited good performance on cell adhesion and growth. On the other hand, the cast films were found to be cell resistant and bioinert coatings. The viability for creating cell interactive materials has been demonstrated for these natural macromolecules using the LbL technique.

Surface-relief gratings are photoinscribed on ionically adsorbed layer-by-layer (LBL) films of an... more Surface-relief gratings are photoinscribed on ionically adsorbed layer-by-layer (LBL) films of an azodye, Brilliant Yellow (BY), which was layered alternately with a polyelectrolyte. Photoinscription is performed by impinging an interference pattern of p- or s-polarized laser light with moderate intensity onto the LBL film, which is unlikely to cause thermal effects. Large-scale mass transport occurs due to the force associated

As exigências de mercado atuais fazem com que a agroindústria brasileira esteja sempre na busca i... more As exigências de mercado atuais fazem com que a agroindústria brasileira esteja sempre na busca incessante da melhoria dos processos com vistas ao aumento da produtividade, qualidade e competitividade. No mercado internacional de agroprodutos, as exigências por qualidade são ainda maiores, muitas vezes ultrapassando as características do produto em si e englobando o processo de produção, no qual o impacto ambiental das atividades ganha cada vez mais importância. Paralelamente, o foco em procedimentos industriais de sanidade e redução de contaminação biológica, principalmente em processos na indústria alimentícia, vem freqüentemente ganhando destaque, tanto na mídia quanto em trabalhos de pesquisa. Na indústria de polímeros esta é uma preocupação legítima, tanto pelo alto uso destes materiais como embalagens de alimentos como também pelo fato de serem significativamente estáveis, gerando resíduos de difícil degradação, agindo como potenciais vetores de proliferação de microorganismos quando contaminados (seja em processo ou pelo uso) e descartados (PADULA e CUERVO, 2004).

The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of ... more The use of nanostructured films to modify electrochemical electrodes has allowed a whole host of new systems/devices to be fabricated, with properties that may be tuned upon synergistic interactions between the film components. Films produced with the Layer-by-Layer (LbL) technique, in particular, have opened up the way for new approaches in electrochomism, electrocatalysis, bioelectrochemistry and electroanalysis, for organic and inorganic-organic hybrid nanoarchitectures may be achieved. In addition to the fabrication of novel, optimized materials, with the LbL method fundamental processes such as charge transfer mechanisms involving biomolecules and nanoparticles can be investigated at the molecular level. In this paper we highlight the recent trends in the electrochemistry of LbL films, with emphasis on their promising technological applications in sensing/biosensing and electrochromic devices.

Biosensors and Bioelectronics, Feb 1, 2010

This paper brings an overview of the use of nanostructured films in several types of biosensors, ... more This paper brings an overview of the use of nanostructured films in several types of biosensors, with emphasis on the advantageous control of molecular architecture which is typical of the layer-by-layer (LbL) and Langmuir-Blodgett films. Following introductory sections on film fabrication and detection methods, we concentrate on the immobilization of biomolecules on these nanostructured films used in units for biosensing. Important contributions in the literature in biosensors based on electrochemical and optical measurements are highlighted. Furthermore, a discussion is presented on how the concept of electronic tongues has been extended to biosensing, which resulted in increased sensitivity and selectivity. The integration of sensing units with micro-electronics is commented upon, especially in the context of using field-effect transistors (FETs) for biosensing. Examples of LbL and LB films containing proteins, lipids, metallic nanoparticles and carbon nanotubes, which are used for detecting a variety of analytes, will be provided. The prospects for clinical diagnosis with such biosensors are also assessed. Throughout the review, emphasis is placed on the importance of control of molecular architecture, particularly with synergistic combination of organic and inorganic materials. For example, nanostructured films containing capped gold nanoparticles or carbon nanotubes exhibited enhanced performance in biosensing. It is hoped that this survey may assist researchers in choosing materials, molecular architectures, and detection principles, which may be tailored for specific applications.

Journal of Macromolecular Science Part a, 2001

ABSTRACT

Synthetic Metals, Apr 1, 2003

Eprint Arxiv Cs 0611013, Nov 3, 2006

In this paper we introduce the AMADEUS strategy, which has been used to produce scientific writin... more In this paper we introduce the AMADEUS strategy, which has been used to produce scientific writing tools for non-native users of English for 15 years, and emphasize a learn-by-doing approach through which students and novice writers can improve their scientific writing. More specifically, we provide a 9-step recipe for the students to compile writing material according to a procedure that has proven efficient in scientific writing courses.

Journal of Nanoscience and Nanotechnology, Feb 1, 2011

Liposomes have been applied to many fields as nanocarriers, especially in drug delivery as active... more Liposomes have been applied to many fields as nanocarriers, especially in drug delivery as active molecules may be entrapped either in their aqueous interior or onto the hydrophobic surface. In this paper we describe the fabrication of layer-by-layer (LbL) films made with liposomes incorporating the anti-inflammatory ibuprofen. The liposomes were made with dipalmitoyl phosphatidyl choline (DPPC), dipalmitoyl phosphatidyl glycerol (DPPG) and palmitoyl oleoyl phosphatidyl glycerol (POPG). LbL films were assembled via alternate adsorption of the polyamidoamine dendrimer (PAMAM), generation 4, and liposomes containing ibuprofen. According to dynamic light scattering measurements, the incorporation of ibuprofen caused DPPC and DPPG liposomes to become more stable, with a decrease in diameter from 140 to 74 nm and 132 to 63 nm, respectively. In contrast, liposomes from POPG became less stable, with an increase in size from 110 to 160 nm after ibuprofen incorporation. These results were confirmed by atomic force microscopy images of LbL films, which showed a large tendency to rupture for POPG liposomes. Film growth was monitored using nanogravimetry and UV-Vis spectroscopy, indicating that growth stops after 10 bilayers. The release of ibuprofen obtained with fluorescence measurements was slower for the liposomes, with decay times of 9.2 and 8.5 h for DPPG and POPG liposomes, respectively, than for the free drug with a decay time of 5.2 h. Ibuprofen could also be released from the LbL films made with DPPG and POPG liposomes, which is promising for further uses in patches.

Environmental Science and Technology, Aug 1, 2005

Humic acids (HAs), naturally occurring biomacromolecules, were incorporated into nanostructured p... more Humic acids (HAs), naturally occurring biomacromolecules, were incorporated into nanostructured polymeric films using the layer-by-layer (LbL) technique, in which HA layers were alternated with layers of poly(allylamine hydrochloride) (PAH). Atomic force microscopy (AFM) revealed very smooth films, with mean roughness varying from 0.89 to 1.19 nm for films containing 5 and 15 PAH/HA bilayers, respectively. The films displayed electroactivity, with the presence of only one reduction peak at ca. 0.675 V (vs Ag/AgCl). Such a well-defined electroactivity allowed the films to be used as highly sensitive pesticide sensors, with detection of pentachlorophenol (PCP) in solutions at concentrations as low as 10 -9 mol L -1 .

Analytical Chemistry, 2010

The integration of nanostructured films containing biomolecules and silicon-based technologies is... more The integration of nanostructured films containing biomolecules and silicon-based technologies is a promising direction for reaching miniaturized biosensors that exhibit high sensitivity and selectivity. A challenge, however, is to avoid cross talk among sensing units in an array with multiple sensors located on a small area. In this letter, we describe an array of 16 sensing units of a light-addressable potentiometric sensor (LAPS), which was made with layer-by-layer (LbL) films of a poly(amidomine) dendrimer (PAMAM) and single-walled carbon nanotubes (SWNTs), coated with a layer of the enzyme penicillinase. A visual inspection of the data from constant-current measurements with liquid samples containing distinct concentrations of penicillin, glucose, or a buffer indicated a possible cross talk between units that contained penicillinase and those that did not. With the use of multidimensional data projection techniques, normally employed in information visualization methods, we managed to distinguish the results from the modified LAPS, even in cases where the units were adjacent to each other. Furthermore, the plots generated with the interactive document map (IDMAP) projection technique enabled the distinction of the different concentrations of penicillin, from 5 mmol L -1 down to 0.5 mmol L -1 . Data visualization also confirmed the enhanced performance of the sensing units containing carbon nanotubes, consistent with the analysis of results for LAPS sensors. The use of visual analytics, as with projection methods, may be essential to handle a large amount of data generated in multiple sensor arrays to achieve high performance in miniaturized systems.

Biosensors and Bioelectronics, Aug 1, 2009

Silicon-based sensors incorporating biomolecules are advantageous for processing and possible bio... more Silicon-based sensors incorporating biomolecules are advantageous for processing and possible biological recognition in a small, reliable and rugged manufactured device. In this study, we report on the functionalization of field-effect (bio-)chemical sensors with layer-by-layer (LbL) films containing single-walled carbon nanotubes (SWNTs) and polyamidoamine (PAMAM) dendrimers. A capacitive electrolyte-insulator-semiconductor (EIS) structure modified with carbon nanotubes (EIS-NT) was built, which could be used as a penicillin biosensor. From atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) images, the LbL films were shown to be highly porous due to interpenetration of SWNTs into the dendrimer layers. Capacitance-voltage (C/V) measurements pointed to a high pH sensitivity of ca. 55 mV/pH for the EIS-NT structures. The biosensing ability towards penicillin of an EIS-NT-penicillinase biosensor was also observed as the flat-band voltage shifted to lower potentials at different penicillin concentrations. A dynamic response of penicillin concentrations, ranging from 5.0 M to 25 mM, was evaluated for an EIS-NT with the penicillinase enzyme immobilized onto the surfaces, via constant-capacitance (ConCap) measurements, achieving a sensitivity of ca. 116 mV/decade. The presence of the nanostructured PAMAM/SWNT LbL film led to sensors with higher sensitivity and better performance.

Synthetic Metals, Apr 1, 2003

The Journal of Physical Chemistry B, Jul 3, 2003

Nanoscale composites of polyaniline (PANI) and vanadium oxide (V 2 O 5 ) were assembled via the e... more Nanoscale composites of polyaniline (PANI) and vanadium oxide (V 2 O 5 ) were assembled via the electrostatic layer-by-layer (LBL) technique, with a thickness per bilayer of 2.5 nm. Interactions between PANI and V 2 O 5 are maximized in comparison to the usual xerogel films due to the nanostructured nature of the LBL films, in which V 2 O 5 causes PANI to be oxidized. This has been demonstrated in Raman spectroscopy measurements and is consistent with electrochemical data. These strong interactions make the LBL film to display a color that is different from the colors of the individual materials. Furthermore, they promote a cooperative effect that enhances the charge storage capability of the films, with a total charge of 2.25 mC cm -2 for the PANI/ V 2 O 5 LBL films, in comparison with 1.86 mC cm -2 for the sum of the isolated contributions from PANI and V 2 O 5 .

Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel te... more Energy diagrams have been obtained for iron tetrasulfonated phthalocyanine (FeTsPc) and nickel tetrasulfonated phthalocyanine (NiTsPc) from electrochemical and electronic absorption measurements in layer-by-Layer (LbL) films with chitosan in the cationic layers. This was made possible because the chitosan/FeTsPc and chitosan/NiTsPc modified electrodes exhibited a reversible, highly stable electrochemical response, with the voltammetric signal being preserved after several cycles in the range between 0 and 1.0V vs Ag/AgCl. The ionization potential (IP), electroa nity (EA) and energy gap (E g ) were similar for both systems, suggesting that the coordinating metal atom does not play an important role in the elelctronic properties of the immobilized phthalocyanines. Chitosan was found suitable for the cationic layers as it did not affect the electrochemical current appreciably. The anodic peak current varied linearly with the scan rate for chitosan/NiTsPc and chitosan/FeTsPc films, denoting charge transport via electron hopping within the film, typical of a polymer-modified electrode.

The Journal of Physical Chemistry C, Apr 8, 2009

We describe a simple and efficient strategy to fabricate enzymatic devices based on the depositio... more We describe a simple and efficient strategy to fabricate enzymatic devices based on the deposition of glucose oxidase on aligned and highly oriented CoNiMo metallic nanowires. CoNiMo nanowires with an average diameter of 200 nm and length of 50 µm were electrodeposited on Au-covered alumina substrates via electrodeposition, using alumina membranes as templates. Enzyme-modified electrodes were fabricated via enzyme immobilization using a cross-linker. To minimize nonspecific reactions in the presence of interfering agents, a permselective membrane composed of poly(vinylsulfonic acid) and polyamidoamine dendrimer was deposited via electrostatic interaction. The formation of hydrogen peroxide as a product of the enzymatic reaction was monitored at low overpotential, 0.0 V (vs Ag/AgCl). The detection limit was estimated at 22 µM under an applied potential of 0.0 V. The apparent Michaelis-Menten constant determined from the Lineweaver-Burke plot was 2 mM.

Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid... more Thin polymer films produced by alternating bilayers of natural macromolecules, such as humic acid (HA) and natural rubber latex (NR) extracted from Hevea brasiliensis, were investigated for their cell-attachment interaction with human fibroblast cells. Layer-by-layer (LbL) films with up to 10 bilayers of PAH/HA or PAH/(HA+Latex) were deposited directly on tissue culture polystyrene substrates (TCPS). In control experiments, cast films were fabricated on TCPS using 0.5% (v/v) of fresh latex and 0.5 g/L solutions of HA in different proportions (latex:HA = 10:1, 5:1, 1:1, 1:2). Both PAH/HA and PAH/(HA+Latex) LbL films exhibited good performance on cell adhesion and growth. On the other hand, the cast films were found to be cell resistant and bioinert coatings. The viability for creating cell interactive materials has been demonstrated for these natural macromolecules using the LbL technique.

Surface-relief gratings are photoinscribed on ionically adsorbed layer-by-layer (LBL) films of an... more Surface-relief gratings are photoinscribed on ionically adsorbed layer-by-layer (LBL) films of an azodye, Brilliant Yellow (BY), which was layered alternately with a polyelectrolyte. Photoinscription is performed by impinging an interference pattern of p- or s-polarized laser light with moderate intensity onto the LBL film, which is unlikely to cause thermal effects. Large-scale mass transport occurs due to the force associated