RESUMO
Despite growing interest in droplet microfluidic methods for droplet interface bilayer (DIB) formation, there is a dearth of information regarding how phospholipids impact device function. Limited characterization has been carried out for phospholipids, either computationally (in silico) or experimentally (in situ) in polydimethylsiloxane (PDMS) microfluidic devices, despite recent work providing a better understanding of how other surfactants behave in microfluidic systems. Hence, microfluidic device design for DIB applications relies heavily on trial and error, with many assumptions made about the impact of phospholipids on droplet formation and surface properties. Here, we examine the effects of phospholipids on interfacial tension, droplet formation, wetting, and hence device longevity, using DPhPC as the most widely used lipid for DIB formation. We use a customized COMSOL in silico model in comparison with in situ experimental data to establish that the stabilization of droplet formation seen when the lipid is dosed in the aqueous phase (lipid-in) or in the oil phase (lipid-out) is directly dependent on the effects of lipids on the device surface properties, rather than on how fast they coat the droplet. Furthermore, we establish a means to visually characterize surface property evolution in the presence of lipids and explore rates of device failure in the absence of lipid, lipid-out, and lipid-in. This first exploration of the effects of lipids on device function may serve to inform the design of microfluidic devices for DIB formation as well as to troubleshoot causes of device failure during microfluidic DIB experiments.
RESUMO
The detection of pollutant traces in the public and environmental waters is essential for safety of the population. Bisphenol A (BPA) is a toxic chemical widely used for the production of food storage containers by plastic industries to increase the storage ability. However, the insertion of BPA in water medium leads to serious health risks. Therefore, the development of low-cost, practical, sensitive, and selective devices to monitor BPA levels on-site in the environment is highly needed. Herein, for the first time, we present a homemade portable potentiostat device integrated to a laser-scribed graphene (LSG) sensor for BPA detection as a practical environmental pollutant monitoring tool. Recently, there has been an increasing need regarding the development of graphene-based electrochemical transducers (e.g., electrodes) to obtain efficient biosensing platforms. LSG platform is combined with molecularly imprinted polymer (MIP) matrix. LSG electrodes were modified with gold nanostructures and PEDOT polymer electrodeposition to create a specific MIP biomimetic receptor for ultrasensitive BPA detection. The sensing device has a Bluetooth connection, wirelessly connected to a smartphone providing high sensitivity and sensitivity (LOD: 3.97 nM in a linear range of .01-10 µM) toward BPA. Two commercial bottled water samples, tap water, commercial milk, and baby formula samples have been used to validate the reliability of the portable sensor device.
RESUMO
The COVID-19 pandemic has been the most critical public health issue in modern history due to its highly infectious and deathly potential, and the limited access to massive, low-cost, and reliable testing has significantly worsened the crisis. The recovery and the vaccination of millions of people against COVID-19 have made serological tests highly relevant to identify the presence and levels of SARS-CoV-2 antibodies. Due to its advantages, microfluidic-based technologies represent an attractive alternative to the conventional testing methodologies used for these purposes. In this work, we described the development of an automated ELISA on-chip capable of detecting anti-SARS-CoV-2 antibodies in serum samples from COVID-19 patients and vaccinated individuals. The colorimetric reactions were analyzed with a microplate reader. No statistically significant differences were observed when comparing the results of our automated ELISA on-chip against the ones obtained from a traditional ELISA on a microplate. Moreover, we demonstrated that it is possible to carry out the analysis of the colorimetric reaction by performing basic image analysis of photos taken with a smartphone, which constitutes a useful alternative when lacking specialized equipment or a laboratory setting. Our automated ELISA on-chip has the potential to be used in a clinical setting and mitigates some of the burden caused by testing deficiencies.
