Parmiss Mojir Shaibani

Detection of Volatile Organic Compounds Using Microwave Sensors

A microwave (MW)-based sensing platform for detection of acetone vapor is demonstrated. The sensing platform comprises of an MW resonator coated with a thin layer of polydimethylsiloxane (PDMS) that acts as a sorbent layer for acetone. Absorption-induced swelling of PDMS changes the permittivity and results in reproducible variations in the resonance frequency of the resonator. Here, we demonstrate the detection of acetone, as the model analyte, with the concentrations of 0-265 ppt. In addition, since the technique is based on electromagnetic fields spilling into space, we show the ability of the sensor to detect acetone in a noncontact fashion.

A novel technique for rapid vapor detection using swelling polymer covered microstrip ring resonator

A state of the art technique is presented to enable the use of a planar RF resonator in Volatile Organic Compound (VOC) vapors detection as a simple and low cost sensor platform. In the proposed solution, swelling polymer (polydimethylsiloxane; PDMS) film is deposited on top of a Microstrip ring resonator. At the exposure of the PDMS layer to various concentrations of VOCs such as ethanol and acetone, the PDMS layer adsorbs the vapors. This results in a change in the PDMS thickness and permittivity, which is then detected by a shift in the resonance frequency of the resonator. It is believed that the combination of swelling polymers and the Microstrip resonators can pave the way towards application of planar RF resonators for gas phase detection.

Metabolic Study of Cancer Cells Using a pH Sensitive Hydrogel Nanofiber Light Addressable Potentiometric Sensor

We report a simple, fast, and cost-effective approach that measures cancer cell metabolism and their response to anticancer drugs in real time. Using a Light Addressable Potentiometric Sensor integrated with pH sensitive hydrogel nanofibers (NF-LAPS), we detect localized changes in pH of the media as cancer cells consume glucose and release lactate. NF-LAPS shows a sensitivity response of 74 mV/pH for cancer cells. Cancer cells (MDA MB231) showed a response of ∼0.4 unit change in pH compared to virtually no change observed for normal cells (MCF10A). We also observed a drop in pH for the multidrug-resistant cancer cells (MDA-MB-435MDR) in the presence of doxorubicin. However, inhibition of the metabolic enzymes such as hexokinase and lactate dehydrogenase-A suggested an improvement in the efficacy of doxorubicin by decreasing the level of acidification. This approach, based on extracellular acidification, enhances our understanding of cancer cell metabolic modes and their response to chemotherapies, which will help in the development of better treatments, including choice of drugs and dosages.

Photocatalytic BiFeO3Nanofibrous Mats for Effective Water Treatment

One-dimensional BiFeO3 (BFO) nanofibers fabricated by electrospinning of a solution of Nylon6/BFO followed by calcination were used for photocatalytic degradation of contaminants in water. The BFO fibers were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-Vis spectroscopy. The SEM images of the as-spun samples demonstrated the successful production of nanofibers and the SEM images of the samples after calcination confirmed the integrity of the continuous BFO nanofibers. XRD analysis indicated the dominant presence of BFO phase throughout the calcinated nanofibers. Photocatalytic activity of the nanofibers and their application in water purification were investigated against 4-chlorophenol (4CP) as a model water contaminant. The results of the UV-Vis spectroscopy show the degradation of the 4CP by means of the photocatalytic activity of the BFO nanofibers. The kinetics of the photodegradation of 4CP is believed to be governed by a pseudo-first-order kinetics model.

Rapid label-free detection of E. coli using antimicrobial peptide assisted impedance spectroscopy

There is an increasing demand for rapid detection of waterborne pathogens to monitor drinking water safety. We demonstrate a compact, label-free sensor array for rapid detection of Escherichia coli (E. coli) in contaminated water samples using antimicrobial peptide assisted impedimetric sensor platform. Interdigitated electrode arrays immobilized with the antimicrobial peptide Colicin V (ColV) were used to screen the affinity towards different bacterial strains by monitoring impedance variations in real-time. This ColV assisted impedance biosensor exhibited high selectivity towards Gram-negative strains particularly towards E. coli strains. This selective detection of E. coli from other strains was observed at 102 cfu mL−1, which is clinically relevant. The sensor can detect E. coli from 102 to 106 cfu mL−1 in water sample at pH 7 to 9. These results show that the antimicrobial peptide ColV assisted impedimetric array is capable of rapid, specific detection of E. coli in contaminated water samples.

The Effect of Applied Electric Field on the Diameter and Size Distribution of Electrospun Nylon6 Nanofibers

One-dimensional Nylon6 nanofibers were fabricated through the electrospinning process. The effect of the applied electric field and voltage-distance combinations on the diameter and size distribution of the fibers was examined systematically by analyzing scanning electron microscopy (SEM) images. The results indicated that maintaining the electric field at 1 kV/cm with the voltage-distance combination of 15 kV-15 cm among all other combinations would result in the optimum average diameter as well as a narrow size distribution of the fibers.

The role of chloride ions in plasma-activated water treatment processes

The effect of chloride ions (Cl−) on the efficiency of hydroxyl-based (OH˙) water treatment processes, especially plasma treatment systems, remains controversial with conflicting reports of enhanced and deteriorating roles. In this study, we show that during the plasma treatment stage, the scavenging nature of Cl− towards OH˙ decreases the percentage of contaminant removal. On the other hand, the percentage of contaminant removal increases during the post-treatment phase due to the formation of singlet oxygen (1O2) from the reaction of hypochlorous acid (HOCl) and hydrogen peroxide (H2O2). Our results show that there exists an optimum Cl− concentration at which the removal percentage is at its maximum. We also investigated the effect of pH on the role of Cl−. We present possible solution characteristic-dependent reaction pathways and their effect on the treatment process.

Portable Nanofiber-Light Addressable Potentiometric Sensor for Rapid Escherichia coli Detection in Orange Juice

The growing need to prevent pathogen outbreaks is irrefutable in the case of the food industry. Early detection in products, especially beverages, contaminated with bacterial strains is vital to avoid infected foods from reaching the consumer. If E. coli is pesent in such foods, it can cause infections. It can also be an indicator of the existence of other harmful coliforms. In this study, we have investigated the detection of Escherichia coli ( E. coli) in orange juice using a portable nanofiber-light addressable potentiometric sensor (NF-LAPS). We have chosen electrospun pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) hydrogel NFs as the sensitive layer. The successful detection of E. coli was reported with the NF-LAPS in less than 1 h. The limit of detection (LOD) measured in the sensor is found to be102 CFU/mL. We have confirmed the selectivity of the biosensor toward E. coli by examining the response of the NF-LAPS against Salmonella typhimurium ( S. typhi), also commonly found in orange juice. Despite the complex nature of orange juice, the response of the biosensor is in no way affected while orange juice is tested as is.