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A gas sensor array was developed and evaluated using four high-frequency quartz crystal microbalance devices (with a 30 MHz resonant frequency in fundamental mode). The QCM devices were coated with ethyl cellulose (EC), polymethylmethacrylate (PMMA), Apiezon L (ApL), and Apiezon T (ApT) sensing films, and deposited by the ultrasonic atomization method. The objective of this research was to propose a non-invasive technique for acetone biomarker detection, which is associated with diabetes mellitus disease. The gas sensor array was exposed to methanol, ethanol, isopropanol, and acetone biomarkers in four different concentrations, corresponding to 1, 5, 10, and 15 µL, at temperature of 22 °C and relative humidity of 20%. These samples were used because human breath contains them and they are used for disease detection. Moreover, the gas sensor responses were analyzed using principal component analysis and discriminant analysis, achieving the classification of the acetone biomarker with a 100% membership percentage when its concentration varies from 327 to 4908 ppm, and its identification from methanol, ethanol, and isopropanol.
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Diabetes Mellitus , Técnicas de Microbalança de Cristal de Quartzo , Humanos , Acetona/análise , 2-Propanol , Metanol , Biomarcadores , Etanol , Quartzo/química , Diabetes Mellitus/diagnósticoRESUMO
Advances in sensors have revolutionized the biomedical engineering field, having an extreme affinity for specific analytes also providing an effective, real-time, point-of-care testing for an accurate diagnosis. Quartz Crystal Microbalance (QCM) is a well-established sensor that has been successfully applied in a broad range of applications to monitor and explore various surface interactions, in situ thin-film formations, and layer properties. This technology has gained interest in biomedical applications since novel QCM systems are able to work in liquid media. QCM with dissipation monitoring (QCM-D) is an expanded version of a QCM that measures changes in damping properties of adsorbed layers thus providing information on its viscoelastic nature. In this article, an open source and low cost QCM-D prototype for biomedical applications was developed. In addition, the system was validated using different Polyethylene Glycol (PEG) concentrations due to its importance for many medical applications. The statistics show a bigger dissipation of the system as the fluid becomes more viscous, also having a very acceptable sensibility when temperature is controlled.
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Melanoma is a highly metastatic and rapidly progressing cancer, a leading cause of mortality among skin cancers. The melanoma microenvironment, formed from the activity of malignant cells on the extracellular matrix and the recruitment of immune cells, plays an active role in the development of drug resistance and tumor recurrence, which are clinical challenges in cancer treatment. These tumoral metabolic processes are affected by proteins, including Galectin-3 (Gal-3), which is extensively involved in cancer development. Previously, we characterized a partially methylated mannogalactan (MG-Pe) with antimelanoma activities. In vivo models of melanoma were used to observe MG-Pe effects in survival, spontaneous, and experimental metastases and in tissue oxidative stress. Analytical assays for the molecular interaction of MG-Pe and Gal-3 were performed using a quartz crystal microbalance, atomic force microscopy, and contact angle tensiometer. MG-Pe exhibits an additive effect when administered together with the chemotherapeutic agent dacarbazine, leading to increased survival of treated mice, metastases reduction, and the modulation of oxidative stress. MG-Pe binds to galectin-3. Furthermore, MG-Pe antitumor effects were substantially reduced in Gal-3/KO mice. Our results showed that the novel Gal-3 ligand, MG-Pe, has both antitumor and antimetastatic effects, alone or in combination with chemotherapy.
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Antineoplásicos , Galectina 3 , Melanoma , Neoplasias Cutâneas , Animais , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Dacarbazina/metabolismo , Dacarbazina/farmacologia , Dacarbazina/uso terapêutico , Galectina 3/metabolismo , Galectina 3/farmacologia , Galectina 3/uso terapêutico , Ligantes , Melanoma/tratamento farmacológico , Melanoma/metabolismo , Camundongos , Recidiva Local de Neoplasia , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/metabolismo , Microambiente Tumoral/efeitos dos fármacos , Microambiente Tumoral/fisiologiaRESUMO
Biocompatible smart interfaces play a crucial role in biomedical or tissue engineering applications, where their ability to actively change their conformation or physico-chemical properties permits finely tuning their surface attributes. Polyelectrolytes, such as acrylic acid, are a particular type of smart polymers that present pH responsiveness. This work aims to fabricate stable hydrogel films with reversible pH responsiveness that could spontaneously form wrinkled surface patterns. For this purpose, the photosensitive reaction mixtures were deposited via spin-coating over functionalized glasses. Following vacuum, UV, or either plasma treatments, it is possible to spontaneously form wrinkles, which could increase cell adherence. The pH responsiveness of the material was evaluated, observing an abrupt variation in the film thickness as a function of the environmental pH. Moreover, the presence of the carboxylic acid functional groups at the interface was evidenced by analyzing the adsorption/desorption capacity using methylene blue as a cationic dye model. The results demonstrated that increasing the acrylic acid in the microwrinkled hydrogel effectively improved the adsorption and release capacity and the ability of the carboxylic groups to establish ionic interactions with methylene blue. Finally, the role of the acrylic acid groups and the surface topography (smooth or wrinkled) on the final antibacterial properties were investigated, demonstrating their efficacy against both gram-positive and gram-negative bacteria model strains (E. coli and S. Aureus). According to our findings, microwrinkled hydrogels presented excellent antibacterial properties improving the results obtained for planar (smooth) hydrogels.
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HYPOTHESIS: Dimensionally stable electroactive films displaying spatially addressed redox sites is still a challenging goal due to gel-like structure. Polyelectrolyte and surfactants can yield highly mesostructured films using simple buildup strategies as layer-by-layer. The use of redox modified surfactants is expected to introduce order and an electroactive response in thin films. EXPERIMENTS: The assembly of polyacrylic acid and different combinations of redox-modified and unmodified hexadecyltrimethylammonium bromide yields highly structured and electroactive thin films. The growth, viscoelastic properties, mass, and electron transport of these films were studied by combining electrochemical and quartz crystal balance with dissipation experiments. FINDINGS: Our results show that the films are highly rigid and poorly hydrated. The mass and charge transport reveal that the ingress (egress) of the counter ions during the electrochemical oxidation (reduction) is accompanied with a small amount of water, which is close to their hydration sphere. Thus, the generated mesostructured films present an efficient charge transport with negligible changes in their structures during the electron transfer process. The control over the meso-organization and its stability represents a promising tool in the construction of devices where the vectorial transfer of electrons, or ions, is required.
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The discrimination improvement of an array of four highly sensitive 30 MHz gas quartz crystal microbalance (QCM) sensors was performed and compared to a similar system based on a 12-MHz QCM. The sensing polymeric films were ethyl cellulose (EC), poly-methyl methacrylate (PMMA), Apiezon L (ApL), and Apiezon T (ApT) and they were coated over the AT-cut QCM devices by the drop casting technique. All the sensors had almost the same film thickness (0.2 µm). The fabricated QCM sensor arrays were exposed to three different concentrations, corresponding to 5, 10, and 15 µL, of ethanol, ethyl acetate, and heptane vapors. The steady state sensor responses were measured in a static system at a temperature of 20 °C and relative humidity of 22%. Our results showed that the 30-MHz sensors have a higher sensitivity than 12-MHz ones (around 5.73 times), independently of the sensing film and measured sample. On the other hand, principal component analysis and discriminant analysis were performed using the raw data of the responses. An improvement of the classification percentage between 12 MHz and 30 MHz sensors was found. However, it was not sufficient, especially for low concentrations. Furthermore, using partition coefficient and discriminant analysis (DA), an improvement of 100% classification of the three samples was achieved for the case of the 30-MHz sensor array.
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One of the intended applications for the modification of ion exchange membranes with polyaniline (PAni) is to use it as a matrix to include chemical species that confer a special property such as resistance to fouling or ion selectivity. In particular, the inclusion of polyelectrolyte molecules into the PAni matrix appears to be the way to modulate these properties of selective membranes. Therefore, it must be clearly understood how the polyelectrolyte is incorporated into the matrix of polyaniline. Among the results obtained in this paper using poly(sodium 4-styrenesulfonate) (PSS) and an electrochemical quartz crystal microbalance, the amount of polyelectrolyte incorporated into PAni is found to be proportional to the PSS concentration in solution if its value is between 0 and 20 mM, while it reaches a maximum value when the PSS in solution is greater than 20 mM. When the anion exchange membranes are modified with these composite deposits, the transport number of chloride was found to decrease progressively (when the PSS concentration in solution is between 0 and 20 mM) to reach a practically constant value when a concentration of PSS greater than 20 mM was used.
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The potential use of hybrid nanomaterials based on inorganic optically active nanoparticles known as quantum dots (QDs) and horseradish peroxidase (HRP) has been proposed by several authors as light-controllable nanocatalyzers, moreover, the immobilization within or over silica based supports represents an advantage over bulk-dispersed systems. However, the implications of the immobilization of such hybrid photoactivatable catalyzing systems have not been clarified with detail. Here, we present a thorough study of the functional photoactive efficiency and recycling of immobilized CdS QDs and HRP systems with different configurations, immobilized over silanized silica quartz crystal microbalance (QCM) sensors, allowing an accurate measure of the immobilized mass of each component and its correlation with the initial reaction rate of conversion of Amplex Red (AR) to resorufin. As well, the conversion efficiency is compared between the different systems and also to non-immobilized QD-HRP complexed systems.
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Compostos de Cádmio/química , Enzimas Imobilizadas/química , Peroxidase do Rábano Silvestre/química , Pontos Quânticos/química , Sulfetos/química , Adsorção , Técnicas Biossensoriais/métodos , Catálise , Cinética , Luz , Microesferas , Oxazinas/química , Oxirredução , Tamanho da Partícula , Processos Fotoquímicos , Dióxido de Silício/química , Eletricidade Estática , Propriedades de SuperfícieRESUMO
Low-cost piezoelectric devices, such as simple frequency monitoring quartz crystal microbalance (QCM) devices, have good clinical utility as fast diagnostic tools for the detection of several diseases. However, unspecific antigen recognition, poor molecular probe adsorption and the need for sample dilution are still common drawbacks that hinder their use in routine diagnosis. In this work, piezoelectric sensors were previously coated with thin films of bacterial cellulose nanocrystals (CN) to provide a more sensitive and adapted interface for the attachment of monoclonal immunoglobulin G (IgGNS1) and to favor specific detection of non-structural protein 1 (NS1) of dengue fever. The assembly of the immunochip surface was analyzed by atomic force microscopy (AFM) and the NS1 detection was followed by quartz crystal microbalance with (QCM-D) and without energy dissipation monitoring (QCM). The CN surface was able to immobilize 2.30±0.5mgm-2 of IgGNS1, as confirmed by AFM topography and phase images along with QCM-D. The system was able to detect the NS1 protein in serum with only 10-fold dilution in the range of 0.01-10µgmL-1 by both QCM and QCM-D. The limits of detection of the two devices were 0.1µgmL-1 for QCM-D and 0.32µgmL-1 for QCM. As a result, QCM-D and QCM apparatuses can be used to follow NS1 recognition and have good potential for more sensitive, fast and/or less expensive diagnostic assays for dengue.
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Vírus da Dengue/isolamento & purificação , Dengue/diagnóstico , Nanopartículas/química , Polissacarídeos Bacterianos/química , Técnicas de Microbalança de Cristal de Quartzo/instrumentação , Proteínas não Estruturais Virais/sangue , Anticorpos Imobilizados/química , Bactérias/química , Técnicas Biossensoriais/instrumentação , Celulose/química , Dengue/sangue , Dengue/virologia , Desenho de Equipamento , Humanos , Imunoensaio/instrumentação , Dispositivos Lab-On-A-Chip , Nanopartículas/ultraestrutura , Proteínas não Estruturais Virais/análiseRESUMO
The hemoglobin (Hb) released from erythrocytes is a primary nutritive component for many blood-feeding parasites. The aspartic protease cathepsin D is a hemoglobinase that is involved in the Hb degradation process and is considered an interesting target for chemotherapy intervention. However, traditional enzymatic assays for studying Hb degradation utilize spectrophotometric techniques, which do not allow real-time monitoring and can present serious interference problems. Herein, we describe a biosensor using simple approach for the real-time monitoring of Hb hydrolysis as well as an efficient screening method for natural products as enzymatic inhibitors using a quartz crystal microbalance (QCM) technique. Hemoglobin was anchored on the quartz crystal surface using mixed self-assembled monolayers. The addition of the enzyme caused a mass change (frequency shift) due to Hb hydrolysis, which was monitored in real time. From the frequency change patterns of the Hb-functionalized QCM, we evaluated the enzymatic reaction by determining the kinetic parameters of product formation (k(cat)). The QCM enzymatic assay using immobilized human Hb was shown to be an excellent approach for screening possible inhibitors in complex mixtures, opening up a new avenue for the discovery of novel inhibitors.
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Produtos Biológicos/análise , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Hemoglobinas/metabolismo , Inibidores de Proteases/análise , Técnicas de Microbalança de Cristal de Quartzo , Produtos Biológicos/farmacologia , Catepsina D/antagonistas & inibidores , Catepsina D/metabolismo , Hemoglobinas/análise , Humanos , Hidrólise/efeitos dos fármacos , Inibidores de Proteases/farmacologia , Relação Estrutura-Atividade , Fatores de TempoRESUMO
Un paso crucial en el desarrollo de un inmunosensor piezoeléctrico para la detección de tuberculosis (TB), es la selección y obtención de los inmunoreactivos empleados en el inmunoensayo y la estrategia para la biofuncionalización del transductor. Diversos estudios han reportado el uso del antígeno proteico 38kDa (Ag38kDa) de Mycobacterium tuberculosis (Mtb) como un buen biomarcador de la enfermedad y el cumplimiento de las características físicas y bioquímicas para ser inmovilizado por monocapas autoensambladas (SAMs), en la superficie del electrodo de oro de cristales piezoeléctricos. Un inmunosensor piezoeléctrico desarrollado a partir de un antígeno nativo purificado de Mtb podría ser un método alternativo simple para la detección de Mtb con ventajas de rapidez y reusabilidad, contribuyendo al control y el tratamiento oportuno de la enfermedad. En este estudio se presenta el proceso de purificación del Ag38kDa a partir de proteínas de secreción filtradas de cultivo (CFP) de Mtb para ser usado como inmunoreactivo con potencial aplicación en la detección de Mtb con inmunosensores piezoeléctricos. Se obtuvieron cristales funcionalizados mediante la técnica modificada de monocapas autoensambladas (SAMs), con el antígeno nativo purificado y CFP. Las superficies biofuncionalizadas fueron caracterizadas cualitativamente con microscopía de fuerza atómica (AFM) para validar las condiciones de optimización del protocolo de inmovilización con antígenos de secreción de Mtb. Estos cristales modificados pueden ser acoplados a un sistema de caracterización de un inmunosensor piezoeléctrico para la detección de Mtb mediante un inmunoensayo competitivo directo.
The selection and procurance of the immunoreagents used in the immunoassay and biofunctionalisation transducer strategy, are a key in the piezoelectric immunosensor development for the detection of tuberculosis (TB). Many have reported the use of 38kDa protein antigen (Ag38kDa) from Mycobacterium tuberculosis (Mtb) such as good biomarker of TB disease and compliance with physical and biochemical characteristics to be immobilized by self-assembled monolayers (SAMs), in the gold electrode of piezoelectrics crystals surfaces. A piezoelectric immunosensor developed from purified native antigens of Mtb may be an alternative simple method for detection of Mtb with speed and reusable advantages, contributing to the control and early treatment of disease. In this paper, the purification process of Ag38kDa Mtb from secretory proteins filtered culture (CFP) from Mtb is presented as an immunoreactive with potential application in the detection of Mtb by piezoelectric immunosensors. Functionalized crystals were obtained by using the modified self-assembled monolayers (SAMs) technique, with purified native antigen and CFP. The functionalized surfaces were qualitatively characterized using atomic force microscopy (AFM) in order to validate the immobilization protocol optimal conditions for secretion antigens from Mtb. These modified crystals may be coupled to piezoelectric immunosensor characterization system for detecting of Mtb by a direct competition immunoassay.