Multiplexed Paper Microfluidics for Titration and Detection of Ingredients in Beverages

Food safety and access to systematic approaches for ensuring detection of food hazards is an important issue in most developing countries. With the arrival of paper-based analytical devices (mu PADs) as a promising, rapid, easy-to-use, and low-cost analytical tool, we demonstrated a simple microfluidic-based titration study for the analysis of packaged fruit juices. Similar, to the titration experiments using traditional glassware in chemistry laboratories, in this study the titration experiments were developed using paper microfluidics for the analysis of several analytes such as pH, vitamin C, sugars, and preservatives present in the packaged fruit juices. The allergen found commonly in dairy based mixtures and the non-pathogenic biochemical component responsible for food spoilage in cider based fruit juices were also determined. The results obtained using paper microfluidics were compared with those obtained using a conventional spectrophotometric technique. Finally, a paper microfluidics based multiplexed sensor was developed for the analysis of common nutritional ingredients, an allergen, and a non-pathogenic byproduct present in packaged fruit juices on a single platform. Overall, the results presented in this study reveal that the proposed paper microfluidic assisted colorimetric multiplexed sensor offers a quick and reliable tool for on-spot routine analysis for food safety applications

Optical Properties and Behavior of Whispering Gallery Mode Resonators in Complex Microsphere Configurations: Insights for Sensing and Information Processing Applications

Whispering gallery mode (WGM) resonators are garnering significant attention due to their unique characteristics and remarkable properties. When integrated with optical sensing and processing technology, WGM resonators offer numerous advantages, including compact size, high sensitivity, rapid response, and tunability. This paper comprehensively investigates the optical properties and behavior of WGMs in complex microsphere resonator configurations. The findings underscore the potential of WGMs in sensing applications and their role in advancing future optical information processing. The study explores the impact of configuration, size, excitation, polarization, and coupling effects on the WGMs properties. The paper provides crucial insights and valuable guidance for designing and optimizing microsphere resonator systems, enabling their realization for practical applications.Comment: 11 pages, 13 figure

Label-free lipidome study of paraventricular thalamic nucleus (PVT) of rat brain with post-traumatic stress injury by Raman imaging

© 2021 The Royal Society of Chemistry. Post-traumatic stress disorder (PTSD) is a widespread psychiatric injury that develops serious life-threatening symptoms like substance abuse, severe depression, cognitive impairments, and persistent anxiety. However, the mechanisms of post-traumatic stress injury in brain are poorly understood due to the lack of practical methods to reveal biochemical alterations in various brain regions affected by this type of injury. Here, we introduce a novel method that provides quantitative results from Raman maps in the paraventricular nucleus of the thalamus (PVT) region. By means of this approach, we have shown a lipidome comparison in PVT regions of control and PTSD rat brains. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was also employed for validation of the Raman results. Lipid alterations can reveal invaluable information regarding the PTSD mechanisms in affected regions of brain. We have showed that the concentration of cholesterol, cholesteryl palmitate, phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, sphingomyelin, ganglioside, glyceryl tripalmitate and sulfatide changes in the PVT region of PTSD compared to control rats. A higher concentration of cholesterol suggests a higher level of corticosterone in the brain. Moreover, concentration changes of phospholipids and sphingolipids suggest the alteration of phospholipase A2 (PLA2) which is associated with inflammatory processes in the brain. Our results have broadened the understanding of biomolecular mechanisms for PTSD in the PVT region of the brain. This is the first report regarding the application of Raman spectroscopy for PTSD studies. This method has a wide spectrum of applications and can be applied to various other brain related disorders or other regions of the brain

Ultra-Sensitive Colorimetric Plasmonic Sensing and Microfluidics for Biofluid Diagnostics Using Nanohole Array

Colorimetric techniques provide a useful approach for sensing application because of their low cost, use of inexpensive equipment, requirement of fewer signal transduction hardware, and, above all, their simple-to-understand results. Colorimetric sensor can be used for both qualitative analyte identification as well as quantitative analysis for many application areas such as clinical diagnosis, food quality control, and environmental monitoring. A gap exists between high-end, accurate, and expensive laboratory equipment and low-cost qualitative point-of-care testing tools. Here, we present a label-free plasmonic-based colorimetric sensor fabricated on a transparent plastic substrate consisting of about one billion nanocups in an array with a subwavelength opening and decorated with metal nanoparticles on the side walls, to bridge that gap. The fabrication techniques of the plasmonic sensor, integration to portable microfluidic devices for lab on chip applications, demonstration of highly sensitive refractive-index sensing, DNA hybridization detection, and protein-protein interaction will be reviewed. Further, we anticipate that the colorimetric sensor can be applied to point-of-care diagnostics by utilizing proper surface functionalization techniques, which seems to be one of the current limiting factors. Finally, the future outlook for the colorimetric plasmonic sensors is discussed

Nanoplasmonics and silicon nanophotonics devices for sensing applications

Nanophotonics deals with the interaction of light with matter in nanometer scale. One of the subsets of nanophotonics is nanoplasmonics, which deals with manipulation of light using the unique optical properties of metal nanostructures. Manipulation of light in nanoscale using properties of surface plasmon will make it possible to accomplish a myriad of applications ranging from global security to healthcare and environmental sensing. This thesis studies silicon-based nanophotonics and noble metal based nanoplasmonics devices, and explores their utilities for energy, sensing, and photonics applications. Three dimensional (3D) sub-wavelength tapered periodic hole array plasmonic structure has been designed and fabricated. In contrast to the surface plasmon polariton (SPP) mediated extraordinary optical transmission (EOT), the proposed structure relies on the localized surface plasmon (LSP) enhanced optical transmission. The advantage of LSPs is that the enhanced transmission at different wavelengths and with different dispersion properties can be tuned by controlling the size, shape and materials of the 3D holes. The tapered geometry will funnel and adiabatically focus the photons on to the sub-wavelength plasmonic structure at the bottom, leading to a large local electric field and the enhancement of EOT (due to radiative coupling of surface plasmons). The design principle of such devices for surface enhanced Raman spectroscopy (SERS) applications based on the classical electromagnetic simulations (Finite Difference Time Domain, FDTD) and the quantum mechanical density functional theory (DFT) has been performed. Due to large transmission and reflection resonance wavelength shifts upon binding of molecules on the above flexible, high throughput, large area 3D plasmonic device, the device showed highest ever reported sensitivity of 46,000 nm per refractive-index unit and unprecedented figure of merit of 1,022. The utility of the sensor for highly sensitive refractive-index sensing, DNA hybridization detection, protein-protein interaction and integration to portable microfluidics device for lab on chip applications have been achieved. The thesis discusses how to transform the nanoplasmonic spectroscopy sensing to become colorimetric sensing with requiring only naked eyes or ordinary visible color photography, eliminating the need for precision spectrometer or fluorescence labeling. The device can also be utilized for preparing beyond diffraction limit DNA/proteomics microarray using plasmonic nanolithography techniques. The second part of thesis addresses an important scientific question – how to increase long range energy transfer efficiency in nanoscale. Energy transfer between light and matter (e.g. photons-molecule, molecule-molecule) is essential in sustaining life in nature. One of such examples is photosynthesis. In contrast to the efficient energy transfer processes in the living system (e.g. resonance energy transfer efficiency in reaction center of light harvesting complex for photosynthesis process is over 90%), man-made photonics and plasmonics system are impaired with low energy transfer efficiencies. This poses a serious challenge for the realization of efficient plasmonic devices for signal guiding, modulation and active information processing on nanoscale. Although, many near field energy transfer schemes such as Förster Resonance Energy Transfer (FRET), Dexter Energy Transfer (DET), and Plasmon Resonance Energy Transfer (PRET) have been explored, they are mostly short-ranged (< 100 nm) and the energy transfer efficiency decreases drastically with distance. This thesis proposes a new energy transport route through a hybrid plasmonic-photonic system coupling the dipole-photonic-plasmonic resonance energy transfer (DiP-PRET) to achieve over 90% energy transfer efficiency

Raman Spectroscopy and Microscopy Applications in Cardiovascular Diseases: From Molecules to Organs

Noninvasive and label-free vibrational spectroscopy and microscopy methods have shown great potential for clinical diagnosis applications. Raman spectroscopy is based on inelastic light scattering due to rotational and vibrational modes of molecular bonds. It has been shown that Raman spectra provide chemical signatures of changes in biological tissues in different diseases, and this technique can be employed in label-free monitoring and clinical diagnosis of several diseases, including cardiovascular studies. However, there are very few literature reviews available to summarize the state of art and future applications of Raman spectroscopy in cardiovascular diseases, particularly cardiac hypertrophy. In addition to conventional clinical approaches such as electrocardiography (ECG), echocardiogram (cardiac ultrasound), positron emission tomography (PET), cardiac computed tomography (CT), and single photon emission computed tomography (SPECT), applications of vibrational spectroscopy and microscopy will provide invaluable information useful for the prevention, diagnosis, and treatment of cardiovascular diseases. Various in vivo and ex vivo investigations can potentially be performed using Raman imaging to study and distinguish pathological and physiological cardiac hypertrophies and understand the mechanisms of other cardiac diseases. Here, we have reviewed the recent literature on Raman spectroscopy to study cardiovascular diseases covering investigations on the molecular, cellular, tissue, and organ level

Multiplexed Paper Microfluidics for Titration and Detection of Ingredients in Beverages

Food safety and access to systematic approaches for ensuring detection of food hazards is an important issue in most developing countries. With the arrival of paper-based analytical devices (&micro;PADs) as a promising, rapid, easy-to-use, and low-cost analytical tool, we demonstrated a simple microfluidic-based titration study for the analysis of packaged fruit juices. Similar, to the titration experiments using traditional glassware in chemistry laboratories, in this study the titration experiments were developed using paper microfluidics for the analysis of several analytes such as pH, vitamin C, sugars, and preservatives present in the packaged fruit juices. The allergen found commonly in dairy based mixtures and the non-pathogenic biochemical component responsible for food spoilage in cider based fruit juices were also determined. The results obtained using paper microfluidics were compared with those obtained using a conventional spectrophotometric technique. Finally, a paper microfluidics based multiplexed sensor was developed for the analysis of common nutritional ingredients, an allergen, and a non-pathogenic byproduct present in packaged fruit juices on a single platform. Overall, the results presented in this study reveal that the proposed paper microfluidic assisted colorimetric multiplexed sensor offers a quick and reliable tool for on-spot routine analysis for food safety applications

Nanomaterial-Based CO2 Sensors

The detection of carbon dioxide (CO) is critical for environmental monitoring, chemical safety control, and many industrial applications. The manifold application fields as well as the huge range of CO concentration to be measured make CO sensing a challenging task. Thus, the ability to reliably and quantitatively detect carbon dioxide requires vastly improved materials and approaches that can work under different environmental conditions. Due to their unique favorable chemical, optical, physical, and electrical properties, nanomaterials are considered state-of-the-art sensing materials. This mini-review documents the advancement of nanomaterial-based CO sensors in the last two decades and discusses their strengths, weaknesses, and major applications. The use of nanomaterials for CO sensing offers several improvements in terms of selectivity, sensitivity, response time, and detection, demonstrating the advantage of using nanomaterials for developing high-performance CO sensors. Anticipated future trends in the area of nanomaterial-based CO sensors are also discussed in light of the existing limitations