Entity

Time filter

Source Type


Gualdino A.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Chu V.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Conde J.P.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Conde J.P.,University of Lisbon
Journal of Applied Physics | Year: 2013

Thin-film silicon micro resonators are fabricated by surface micromachining at temperatures that are CMOS and large area substrate-compatible. Disk resonators offer large working surfaces and a large number of vibrational modes. The vibrational modes of micromechanical disk resonators made from hydrogenated amorphous silicon thin films were studied in this work. The dynamic behavior of these structures is shown to be mechanically described to be in the transition between a membrane and a plate due to the influence of residual stresses generated during the film growth and to thermal mismatch with underlying layers. Non-degenerate modes are observed as a consequence of the radial symmetry and their effective stiffness is related to the anchor geometry and the parity of the number of diametric nodal lines. The experimentally measured frequencies were compared with the simulated values from finite element modeling with good agreement. Investigation of the intrinsic quality factors shows that there is a dependence of the energy dissipation per cycle with the mode order that is related to the clamping anchors. Thermal annealing experiments show that enhanced quality factors can be obtained using low temperature annealing for a limited period of time. © 2013 AIP Publishing LLC. Source


Novo P.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Moulas G.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Prazeres D.M.F.,University of Lisbon | Prazeres D.M.F.,IBB Institute for Biotechnology And Bioengineering | And 3 more authors.
Sensors and Actuators, B: Chemical | Year: 2013

Ochratoxin A (OTA) is a mycotoxin produced by naturally occurring fungi in crops such as grapes and cereals. OTA has demonstrated toxicity and carcinogenicity in animals and therefore biosensing systems are required for its detection and quantification in commercialized goods. This work demonstrates an integrated analytical system that conjugates an indirect competitive enzyme-linked immunosorbent assay strategy developed in PDMS microfluidics with integrated microfabricated hydrogenated amorphous silicon photodiodes for chemiluminescence detection. A limit of detection of 0.85 ng/mL was obtained for OTA detection in a PBS solution using a straight-channel configuration. Comparable limits of detection were obtained for beer extracts but for red wine extracts a higher limit of detection of OTA of 28 ng/mL was obtained. A two-channel U-shaped microfluidic device was developed to perform the simultaneous analysis of a reference solution and of an ochratoxin A contaminated solution. This configuration efficiently reduced measurement errors resulting in an improvement of one order of magnitude in the limits of detection of OTA in beer and red wine extracts. The results show that the miniaturized system can be developed into one stage of a future highly sensitive, portable, and fully integrated "toxin-chip" for monitoring food safety applications. © 2012 Elsevier B.V. All rights reserved. Source


Pereira A.T.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Pereira A.T.,IBB Institute for Biotechnology And Bioengineering | Novo P.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Prazeres D.M.F.,IBB Institute for Biotechnology And Bioengineering | And 4 more authors.
Biomicrofluidics | Year: 2011

Miniaturization of immunoassays through microfluidic technology has the potential to decrease the time and the quantity of reactants required for analysis, together with the potential of achieving multiplexing and portability. A lab-on-chip system incorporating a thin-film amorphous silicon (a-Si:H) photodiode microfabricated on a glass substrate with a thin-film amorphous silicon-carbon alloy directly deposited above the photodiode and acting as a fluorescence filter is integrated with a polydimethylsiloxane-based microfluidic network for the direct detection of antibody-antigen molecular recognition reactions using fluorescence. The model immunoassay used consists of primary antibody adsorption to the microchannel walls followed by its recognition by a secondary antibody labeled with a fluorescent quantum-dot tag. The conditions for the flow-through analysis in the microfluidic format were defined and the total assay time was 30 min. Specific molecular recognition was quantitatively detected. The measurements made with the a-Si:H photodiode are consistent with that obtained with a fluorescence microscope and both show a linear dependence on the antibody concentration in the nanomolar-micromolar range. © 2011 American Institute of Physics. Source


Soares R.R.G.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Soares R.R.G.,IBB Institute for Biotechnology And Bioengineering | Novo P.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Novo P.,Leibniz Institute for Analytical Sciences | And 9 more authors.
Journal of Chromatography A | Year: 2014

Immunoassays have a broad application range, from environmental and food toxicology to biomedical analysis, providing rapid and simple methods for analyte quantification. Immunoassays, however, are often challenging at nM and sub nM concentrations and are affected by detrimental matrix interference effects, as is the case of the detection of ochratoxin A (OTA) and Aflatoxin B1 (AFB1). These are widespread mycotoxins found in food and feed, with serious potential implications for human health. This work demonstrates the use of polymer-salt aqueous two phase systems (ATPSs) for the simultaneous concentration of mycotoxins and neutralization of matrix interference. In particular, polyethylene glycol (PEG)-phosphate salt ATPSs were used to enhance the detection sensitivity of OTA and AFB1 in wines and beer by an indirect competitive ELISA. Using this methodology it was possible to quantify both analytes spiked in red wine with limits-of-detection (LoD) down to 0.19ng/mL and 0.035ng/mL, respectively, with results comparable to those obtained using solutions of toxins in phosphate buffered saline (PBS) buffer (0.7ng/mL and 0.009ng/mL, respectively). Furthermore, a very low matrix-to matrix variability was observed, with LoD and half inhibitory concentration (IC50) values of 5.17±1.08 and 33.2±3.5ng/mL (±SD) obtained in the detection of OTA spiked in red and white wines, beer or PBS buffer. These results indicate the potential of ATPS as a fast and simple concentration step and in providing matrix-independent analyte quantification for enhanced immunoassay sensitivity below regulatory levels. © 2014 Elsevier B.V. Source


Jacinto M.J.,University of Lisbon | Soares R.R.G.,University of Lisbon | Soares R.R.G.,INESC Microsistemas e Nanotecnologias and IN Institute of Nanoscience and Nanotechnology | Azevedo A.M.,University of Lisbon | And 5 more authors.
Separation and Purification Technology | Year: 2015

Virus-like particles (VLPs) are promising candidates for a new generation of biopharmaceuticals, with a high impact in gene therapy, vaccination and also in the construction of delivery vehicles. Despite the growing interest in these particles, their production is currently limited by the low capacities and throughputs of classical downstream processing technologies. Aqueous two-phase extraction (ATPE) is a promising bioprocessing technique allowing clarification, concentration and purification to be accomplished in a single step. ATPE also combines a high biocompatibility with a simple and reliable scale-up and can also be performed in a continuous mode of operation. In this work, ATPE conditions for the purification of a Human Immunodeficiency Virus (HIV) VLP were screened and optimized in mL scale batch conditions. Polyethylene glycol (PEG)-salt (potassium phosphate, ammonium sulfate and trisodium citrate) and polymer-polymer (PEG-dextran) systems were investigated, among which the PEG-ammonium sulfate system demonstrated the higher partition coefficient (K = 4.4). This parameter was then compared with the obtained in a continuous microfluidic setting, performed by flowing both immiscible phases through a 100 width × 20 μm wide microchannel. The batch optimization results showed good agreement with the continuous miniaturized extraction, both in terms of K (K = 3.9 in microfluidic scale) and protein purity. These novel findings show that PEG-ammonium sulfate ATPE is a promising system for primary HIV-VLP recovery and demonstrate the potential of a miniaturized ATPE for massive parallelization (scale-out) at the preparative scale or integrated in analytical miniaturized systems. © 2015 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations