Browsing by Author "Afonso, André S. [UFVJM]"

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Fully disposable microfluidic electrochemical device for detection of estrogen receptor alpha breast cancer biomarker
(2017-07-20) Uliana, Carolina V.; Peverari, Camila R.; Afonso, André S. [UFVJM]; Cominetti, Marcia R.; Faria, Ronaldo C.; Universidade Federal de São Carlos; Universidade Federal dos Vales do Jequitinhonha e Mucuri
A novel fully disposable microfluidic electrochemical array device (µFED) was developed and successfully applied for detection of the biomarker estrogen receptor alpha (ERα). The µFED was constructed using low-cost materials and an inexpensive home cutter printer enabled the manufacture of dozens of µFEDs in less than 2h, at a cost of less than US$ 0.20 in material per device. The µFED incorporates counter and reference electrodes and eight carbon-based working electrodes, which were modified with DNA sequences known as estrogen response elements (DNA-ERE), where ERα binds specifically. Paramagnetic particles heavily decorated with anti-ERα antibody and horseradish peroxidase (MP-Ab-HRP) were used to efficiently capture ERα from the sample solution. The ERα-MP-Ab-HRP bioconjugate formed was injected into the µFED and incubated with the DNA-ERE-modified electrodes, followed by amperometric detection with application of -0.2V vs. Ag|AgCl while a mixture of H2O2 and hydroquinone was injected into the microfluidic device. An ultralow limit of detection of 10.0 fg mL(-1) was obtained with the proposed method. The performance of the assay, in terms of sensitivity and reproducibility, was studied using undiluted calf serum, and excellent recoveries in the range of 94.7-108% were achieved for the detection of ERα in MCF-7 cell lysate. The µFED system can be easily constructed and applied for multiplex biomarker detection, making the device an excellent cost-effective alternative for cancer diagnosis, especially in developing countries.
A hole inversion layer at the BiVO4/Bi4V2O11 interface produces a high tunable photovoltage for water splitting
(2016-08-09) Santos, Wayler S. dos [UFVJM]; Rodriguez, Mariandry [UFVJM]; Afonso, André S. [UFVJM]; Mesquita, João P. [UFVJM]; Nascimento, Lucas L.; Patrocínio, Antônio O. T.; Silva, Adilson C.; Oliveira, Luiz C. A.; Fabris, José D. [UFVJM]; Pereira, Márcio C. [UFVJM]; Universidade Federal dos Vales do Jequitinhonha e Mucuri; Universidade Federal de Uberlândia; Universidade Federal de Ouro Preto; Universidade Federal de Minas Gerais
The conversion of solar energy into hydrogen fuel by splitting water into photoelectrochemical cells (PEC) is an appealing strategy to store energy and minimize the extensive use of fossil fuels. The key requirement for efficient water splitting is producing a large band bending (photovoltage) at the semiconductor to improve the separation of the photogenerated charge carriers. Therefore, an attractive method consists in creating internal electrical fields inside the PEC to render more favorable band bending for water splitting. Coupling ferroelectric materials exhibiting spontaneous polarization with visible light photoactive semiconductors can be a likely approach to getting higher photovoltage outputs. The spontaneous electric polarization tends to promote the desirable separation of photogenerated electron- hole pairs and can produce photovoltages higher than that obtained from a conventional p-n heterojunction. Herein, we demonstrate that a hole inversion layer induced by a ferroelectric Bi4V2O11 perovskite at the n-type BiVO4 interface creates a virtual p-n junction with high photovoltage, which is suitable for water splitting. The photovoltage output can be boosted by changing the polarization by doping the ferroelectric material with tungsten in order to produce the relatively large photovoltage of 1.39 V, decreasing the surface recombination and enhancing the photocurrent as much as 180%.