RESUMO
The development of novel high-sensitivity DNA-based biosensors is beneficial, as these devices have applications in the identification of genetic risk factors, medical diagnostics, and environmental monitoring. Herein, we report on the first robust device capable of detecting DNA on a microliter drop with a zepto-molar (10-21) concentration. To accomplish this, we engineered an electrical-electrochemical vertical device (EEVD) that comprises a novel drain and source terminal in a short-circuited configuration, paired with an ideal non-polarizable reference electrode. Vertical electron transfer occurs perpendicularly to the graphene plane, while the electronic current flows through the graphene van der Waals (vdW) heterojunctions. Ferrocene adsorbed on graphene was strategically chosen as the vdW heterojunction redox component. Charge carrier insertion into the graphene makes the EEVD 10 times more sensitive than traditional graphene field-effect transistors. Interfacial potential changes were measured for single-stranded DNA detection with an unprecedented zepto-molar limit of detection.
Assuntos
Técnicas Biossensoriais , Grafite , DNA/genética , DNA de Cadeia Simples , Dente MolarRESUMO
Nonstructural protein 1 (NS1) is secreted by dengue virus in the first days of infection and acts as an excellent dengue biomarker. Here, the direct electrical detection of NS1 from dengue type 2 virus has been achieved by the measurement of variations in open circuit potential (OCP) between a reference electrode and a disposable Au electrode containing immobilized anti-NS1 antibodies acting as immunosensor. Egg yolk immunoglobulin (IgY) was utilized for the first time as the biological recognition element alternatively to conventional mammalian antibodies in the detection of dengue virus NS1 protein. NS1 protein was detected in standard samples in a 0.1 to 10 µg.mL(-1) concentration range with (3.2 ± 0.3) mV/µg.mL(-1) of sensitivity and 0.09â µg.mL(-1) of detection limit. Therefore, the proposed system can be extended to detect NS1 in real samples and provide an early diagnosis of dengue.
Assuntos
Anticorpos Antivirais/imunologia , Dengue/diagnóstico , Gema de Ovo/imunologia , Proteínas não Estruturais Virais/imunologia , Anticorpos Antivirais/isolamento & purificação , Antígenos Virais/química , Antígenos Virais/imunologia , Biomarcadores/química , Dengue/imunologia , Vírus da Dengue/imunologia , Vírus da Dengue/isolamento & purificação , Vírus da Dengue/patogenicidade , Eletrodos , Ensaio de Imunoadsorção Enzimática , Imunoglobulinas/isolamento & purificação , Proteínas não Estruturais Virais/química , Proteínas não Estruturais Virais/isolamento & purificaçãoRESUMO
This paper reports on the use of the crude extract of avocado (CEA) fruit (Persea americana) as a source of tyrosinase enzyme. CEA was immobilized via layer by layer (LbL) technique onto indium tin oxide (ITO) substrates and applied in the detection of monophenol using a potentiometric biosensor. Poly(propylene imine) dendrimer of generation 3 (PPI-G3) was used as a counter ion in the layer by layer process due to its highly porous structure and functional groups suitable for enzyme linkage. After the immobilization of the crude CEA as multilayered films, standard samples of monophenol were detected in the 0.25-4.00 mM linear range with approximately 28 mV mM(-1) of sensitivity. This sensitivity is 14 times higher than the values found in the literature for a similar system. The results show that it is possible to obtain efficient and low-cost biosensors for monophenol detection using potentiometric transducers and alternative sources of enzymes without purification.
Assuntos
Técnicas Biossensoriais/métodos , Misturas Complexas/química , Monofenol Mono-Oxigenase/metabolismo , Persea/enzimologia , Fenol/análise , Fenóis/análise , Catecóis/análise , Polipropilenos/química , Potenciometria , Soluções , Espectrofotometria Ultravioleta , Compostos de Estanho/químicaRESUMO
Separative extended gate field effect transistor (SEGFET) type devices have been used as an ion sensor or biosensor as an alternative to traditional ion sensitive field effect transistors (ISFETs) due to their robustness, ease of fabrication, low cost and possibility of FET isolation from the chemical environment. The layer-by-layer technique allows the combination of different materials with suitable properties for enzyme immobilization on simple platforms such as the extended gate of SEGFET devices enabling the fabrication of biosensors. Here, glucose biosensors based on dendrimers and metallophthalocyanines (MPcs) in the form of layer-by-layer (LbL) films, assembled on indium tin oxide (ITO) as separative extended gate material, has been produced. NH(3)(+) groups in the dendrimer allow electrostatic interactions or covalent bonds with the enzyme (glucose oxidase). Relevant parameters such as optimum pH, buffer concentration and presence of serum bovine albumin (BSA) in the immobilization process were analyzed. The relationship between the output voltage and glucose concentration shows that upon detection of a specific analyte, the sub-products of the enzymatic reaction change the pH locally, affecting the output signal of the FET transducer. In addition, dendritic layers offer a nanoporous environment, which may be permeable to H(+) ions, improving the sensibility as modified electrodes for glucose biosensing.