Simple modification to allow high-efficiency and high-resolution multi-material 3D-printing fabrication of microfluidic devices.

Advances in the instrumentation and materials for photopolymerization 3D printing aided the use of this powerful technique in the fabrication of microfluidic devices. The costs of printers and supplies have been reduced to the point where this technique becomes attractive for prototyping microfluidic systems with good resolution. With all the development of multi-material 3D printers, most of the microfluidic devices prepared by photopolymerization 3D printing are based on a single substrate material.

The Integration of Field Effect Transistors to Microfluidic Devices.

Devices that integrate field effect transistors into microfluidic channels are becoming increasingly promising in the medical, environmental, and food realms, among other applications. The uniqueness of this type of sensor lies in its ability to reduce the background signals existing in the measurements, which interfere in obtaining good limits of detection for the target analyte. This and other advantages intensify the development of selective new sensors and biosensors with coupling configuration.

Microfluidic devices based on textile threads for analytical applications: state of the art and prospects.

Microfluidic devices based on textile threads have interesting advantages when compared to systems made with traditional materials, such as polymers and inorganic substrates (especially silicon and glass). One of these significant advantages is the device fabrication process, made more cheap and simple, with little or no microfabrication apparatus. This review describes the fundamentals, applications, challenges, and prospects of microfluidic devices fabricated with textile threads.

Understanding and improving FDM 3D printing to fabricate high-resolution and optically transparent microfluidic devices.

The fabrication of microfluidic devices through fused deposition modeling (FDM) 3D printing has faced several challenges, mainly regarding obtaining microchannels with suitable transparency and sizes. Thus, the use of this printing system to fabricate microdevices for analytical and bioanalytical applications is commonly limited when compared to other printing technologies. However, for the first time, this work shows a systematic study to improve the potential of FDM 3D printers for the fabrication of transparent microfluidic devices.

Ready-to-use 3D-printed electrochemical cell for in situ voltammetry of immobilized microparticles and Raman spectroscopy.

We report in this communication a ready-to-use fused deposition modeling (FDM) based 3D-printed spectroelectrochemical cell to perform for the first time voltammetry of immobilized microparticles (VIMP) and Raman spectroscopy in situ using acrylonitrile butadiene styrene (ABS) as the filament material for printing. The 3D-printed cell was applied to evaluate solid state electrochemical behavior of tadalafil as a proof-of-concept. Several advantages were achieved in the use of the developed device, such as less manipulation of the working electrode, monitoring the same region of the solid microparticles before and after electrochemical measurements, better control of the laser incidence, low-cost and low-time production.

Microchip Electrophoresis Containing Electrodes for Integrated Electrochemical Detection.

Microchip electrophoresis is a versatile separation technique. Electrochemical detection is suitable to apply to microdevices due to its easy integration to the fabrication process and good sensitivity and selectivity. Here we describe the procedures to prepare Pt band electrodes deposited on glass to couple to polydimethylsiloxane (PDMS) microchips aiming the separation and detection of nitrite using an isolated potentiostat.

Integrated microfluidic device for the separation, decomposition and detection of low molecular weight S-nitrosothiols.

S-nitrosothiols (RSNOs) are very important biomolecules that play crucial roles in many physiological and physiopathological processes. They act as NO-donors and are candidates for future medicines. Their identification and quantitation are therefore important for biomedical applications.

Capillary electrophoresis with capacitively coupled contactless conductivity detection for the determination of propionate and sorbate in bread.

We propose a simple and fast method for the determination of the preservatives propionate and sorbate in bread using capillary electrophoresis with capacitively coupled contactless conductivity detection. The preservatives were quickly extracted from bread using ultra-pure water and ultrasonic energy. The separation of the analytes, with good resolution, was achieved in about 7 min.

Characterization of Off-Stoichiometry Microfluidic Devices for Bioanalytical Applications.

In this paper, we further investigate the properties of off-stoichiometry thiol-ene polymers (OSTE) aiming its application in microchip electrophoresis for bioanalytical applications. The proportion of 1.3:1 (allyl:thiol) and 1:2.

Chemotaxonomic study of Chrysobalanus icaco Linnaeus (Chrysobalanaceae) using ultra-high performance liquid chromatography coupled with diode array detection fingerprint in combination with multivariate analysis.

We investigated a strategy for the chemotaxonomy study of Chrysobalanus icaco Linnaeus (Chrysobalanaceae) based on ultra-high performance liquid chromatography coupled with diode array detection fingerprint in combination with multivariate analysis. Two models using principal component analysis and partial least squares discriminant analysis were developed, and the samples could be successfully classified into two classes: Class 1 (red morphotype) and Class 2 (white and black morphotypes). Furthermore, ultra-high performance liquid chromatography coupled with diode array and electrospray ionization tandem mass spectrometry was used to identify the main compounds responsible for class separation.

Elimination of the artefact peaks in capillary electrophoresis determination of glutamate by using organic solvents in sample preparation.

Focusing on the demand from the food industry for fast and reliable alternative methods to control the quality of food products, we present in this paper a method for amino acid separation and glutamic acid quantification in complex matrices employing capillary electrophoresis with capacitively coupled contactless conductivity detection. We demonstrate by simulation and experimentally the use of organic solvents in sample preparation to prevent peak splitting and increase stacking in capillary electrophoretic separations of amino acids. Additionally, we obtained results for glutamic acid quantification comparable to those obtained via traditional methods used at industrial sites.

Capillary electrophoresis with mass spectrometric detection for separation of S-nitrosoglutathione and its decomposition products: a deeper insight into the decomposition pathways.

S-Nitrosoglutathione (GSNO) is a very important biomolecule that has crucial functions in many physiological and physiopathological processes. GSNO acts as NO donor and is a candidate for future medicines. This work describes, for the first time, the separation and the detection of GSNO and its decomposition products using capillary electrophoresis coupled to mass spectrometry (CE-MS).

Capillary electrophoresis coupled to contactless conductivity detection for the analysis of S-nitrosothiols decomposition and reactivity.

S-Nitrosothiols (RSNO) are composed of a NO group bound to the sulfhydryl group of a peptide or protein. RSNO are very important biological molecules, since they have many effects on human health. RSNO are easily naturally decomposed by metal ions, light, and heat, with different kinetics.

Metalless electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips.

This paper describes the use of ionic solutions as sensing electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips. Initially, two channels were engraved in a PMMA holder by using a CO2 laser system and sealed with a thin adhesive membrane. PDMS electrophoresis chips were fabricated by soft lithography and reversibly sealed against the polymer membrane.

Surface modification of PDMS microchips with poly(ethylene glycol) derivatives for μTAS applications.

In this work is presented a method for the modification of native PDMS surface in order to improve its applicability as a substrate for microfluidic devices, especially in the analysis of nonpolar analytes. Therefore, poly(ethylene glycol) divinyl ether modified PDMS substrate was obtained by surface modification of native PDMS. The modified substrate was characterized by attenuated total reflectance infrared spectroscopy, water contact angle measurements, and by evaluating the adsorption of rhodamine B and the magnitude of the EOF mobility.

An integrated microfluidic device for monitoring changes in nitric oxide production in single T-lymphocyte (Jurkat) cells.

A considerable amount of attention has been focused on the analysis of single cells in an effort to better understand cell heterogeneity in cancer and neurodegenerative diseases. Although microfluidic devices have several advantages for single cell analysis, few papers have actually demonstrated the ability of these devices to monitor chemical changes in perturbed biological systems. In this paper, a new microfluidic channel manifold is described that integrates cell transport, lysis, injection, electrophoretic separation, and fluorescence detection into a single device, making it possible to analyze individual cells at a rate of 10 cells/min in an automated fashion.

Identification of the oxidation products of cysteamine and cystamine by CE-MS interfaced by a noncommercial electrospray ionization source.

Sodium cysteamine phosphate is a prodrug derivative of cysteamine that can be used in cystinosis treatment. Although titrimetric assays are very well established and precise, iodimetric determination of sodium cysteamine phosphate requires considerably more carefulness and time from the analyst than usual. The possibility to assess sodium cysteamine phosphate by CE was evaluated by means of the quantification of its oxidation product, cystamine, which is a more suitable substance to be used as primary standard than sodium cysteamine phosphate.

Raman imaging spectroscopic characterization of modified poly(dimethylsiloxane) for micro total analysis systems applications.

Methacryloxypropyl-modified poly(dimethylsiloxane) rubbers were obtained from poly(dimethylsiloxane), PDMS, and methacryloxypropyltrimethoxysilane, MPTMS, by polycondensation reactions. The modified rubbers, prepared with 20 and 30% (v/v) of MPTMS, were used as substrates for microchannel fabrication by the CO(2) laser ablation technique. Raman imaging spectroscopy was used for the surface characterization, showing the homogeneity of the rubbery material, with uniform distribution of the crosslinking centers.

Microchip electrophoresis with amperometric detection for the study of the generation of nitric oxide by NONOate salts.

Microchip electrophoresis (ME) with electrochemical detection was used to monitor nitric oxide (NO) production from diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) and 1-(hydroxyl-NNO-azoxy)-L-proline disodium salt (PROLI/NO). NO was generated through acid hydrolysis of these NONOate salts. The products of acid hydrolysis were introduced into a 5-cm separation channel using gated injection.

Toner and paper-based fabrication techniques for microfluidic applications.

The interest in low-cost microfluidic platforms as well as emerging microfabrication techniques has increased considerably over the last years. Toner- and paper-based techniques have appeared as two of the most promising platforms for the production of disposable devices for on-chip applications. This review focuses on recent advances in the fabrication techniques and in the analytical/bioanalytical applications of toner and paper-based devices.

Fast determination of ethambutol in pharmaceutical formulations using capillary electrophoresis with capacitively coupled contactless conductivity detection.

A method for the determination of ethambutol (EMB), a first-line drug against tuberculosis, based on CE with capacitively coupled contactless conductivity detection is proposed. The separation of EMB and its main product of degradation were achieved in less than 3 min with a resolution of 2.0 using a BGE composed of 50 mmol/L histidine and 30 mmol/L MES, pH 6.

Simultaneous determination of free fluoride and monofluorophosphate in toothpaste by capillary electrophoresis with capacitively coupled contactless conductivity detection.

Capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C(4)D) was used for rapid, accurate and simultaneous determination of free fluoride and monofluorophosphate (MFP) in six different toothpaste samples. A buffer solution containing 15 mmol L(-1) histine, 25 mmol L(-1) lactic acid, and 2.5 mmol L(-1) tetradecyltrimethylammonium bromide (TTAB) was used as background electrolyte (BGE).

Fabrication of a multichannel PDMS/glass analytical microsystem with integrated electrodes for amperometric detection.

The fabrication process of novel multichannel microfluidic devices with integrated electrodes for amperometric detection is described. Soft-lithography, lift-off and O(2) plasma surface activation sealing techniques were employed for rapid prototyping of cost effective PDMS/glass microchips. The capabilities of the proposed microdevices were demonstrated by the electrooxidation of hydroquinone and N-acetyl-p-aminophenol (APAP) on a Au working electrode at +800 mV and +700 mV, respectively, against a Au pseudo reference electrode, and of thiocyanate on a Cu working electrode at +700 mV against a Ag/AgCl (KCl saturated) reference electrode.

Use of experimental design and effective mobility calculations to develop a method for the determination of antimicrobials by capillary electrophoresis.

A capillary zone electrophoresis (CZE) method for the determination of chloramphenicol (CLP), danofloxacin (DANO), ciprofloxacin (CIPRO), enrofloxacin (ENRO), sulfamethazine (SMZ), sulfaquinoxaline (SQX) and sulfamethoxazole (SMX) is described. For the development, the effective mobilities were estimated and a central composite design was performed. The method was in-house validated for CLP, CIPRO, ENRO and SMX determination in pharmaceuticals.

Fabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner electrophoresis microchips.

In this report, we describe the microfabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner (PT) electrophoresis microchips using toner masks. Planar electrodes were fabricated by three simple steps: (i) drawing and laser-printing the electrode geometry on polyester films, (ii) sputtering deposition onto substrates, and (iii) removal of toner layer by a lift-off process. The polyester film with anchored electrodes was integrated to PT electrophoresis microchannels by lamination at 120 degrees C in less than 1 min.