Multiplexed fluorescence and scatter detection with single cell resolution using on-chip fiber optics for droplet microfluidic applications.

Droplet microfluidics has emerged as a critical component of several high-throughput single-cell analysis techniques in biomedical research and diagnostics. Despite significant progress in the development of individual assays, multiparametric optical sensing of droplets and their encapsulated contents has been challenging. The current approaches, most commonly involving microscopy-based high-speed imaging of droplets, are technically complex and require expensive instrumentation, limiting their widespread adoption. To address these limitations, we developed the OptiDrop platform; this platform is a novel optofluidic setup that leverages the principles of flow cytometry. Our platform enables on-chip detection of the scatter and multiple fluorescence signals from the microfluidic droplets and their contents using optical fibers. The highly customizable on-chip optical fiber-based signal detection system enables simplified, miniaturized, low-cost, multiparametric sensing of optical signals with high sensitivity and single-cell resolution within each droplet. To demonstrate the ability of the OptiDrop platform, we conducted a differential expression analysis of the major histocompatibility complex (MHC) protein in response to IFNγ stimulation. Our results showed the platform's ability to sensitively detect cell surface biomarkers using fluorescently labeled antibodies. Thus, the OptiDrop platform combines the versatility of flow cytometry with the power of droplet microfluidics to provide wide-ranging, scalable optical sensing solutions for research and diagnostics.

Realization of pitch-rotational torque wrench in two-beam optical tweezers.

3D Pitch (out-of-plane) rotational motion has been generated in spherical particles by maneuvering the laser spots of holographic optical tweezers. However, since the spherical particles, which are required to minimise drag are perfectly isotropic, a controllable torque cannot be applied with it. It remains free to spin about any axis even after moving the tweezers beams. It is here that we trap birefringent particles of about 3 µm diameter in two tweezers beams and then change the depth of one of the beam foci controllably to generate a pitch rotational torque-wrench and avoid the free spinning of the particle. We also detect the rotation with newly developed pitch motion detection technique and apply controlled torques on the particle.

Estimation of rolling work of adhesion at the nanoscale with soft probing using optical tweezers.

Conventionally, the work of adhesion at the nanoscale is estimated using an atomic force microscope with a tip of the size of 10 nm. It is pressed into a surface with nano-Newton forces and then retracted to ascertain when the tip breaks away from the surface. Thus this ensures "hard probing" of a surface. However there can be another configuration where the particle is barely placed into the surface when the work of adhesion attaches the particle to the surface and this can be called "soft probing". In this configuration, if a birefringent particle is confined in linearly polarized optical tweezers, and then the surface is moved in the direction tangential to the plane, a rolling motion can be induced. Study of this rolling motion can also show the work of adhesion. We use this configuration to find the rolling work of adhesion of a 3 µm diameter birefringent particle on a glass surface. We go on to study the effects of changing the surface to a hydrophobic slippery surface like polydimethyl siloxane (PDMS). Then we go on to show that even 500 nm diameter diamonds bearing nitrogen vacancy (NV) centers which are birefringent due to the stresses on the crystal could also be trapped and rolled to generate pitch (out-of-plane rotation) motion with 50 nm contact diameters. We find that this mode of soft probing yields a work of adhesion of about 1 mJ m-2 while the conventional nanoscale probing with atomic force microscopes (AFM) yields about 50 mJ m-2.

A low-cost 3D printed microfluidic bioreactor and imaging chamber for live-organoid imaging.

Organoids are biological systems grown in vitro and are observed to self-organize into 3D cellular tissues of specific organs. Brain organoids have emerged as valuable models for the study of human brain development in health and disease. Researchers are now in need of improved culturing and imaging tools to capture the in vitro dynamics of development processes in the brain. Here, we describe the design of a microfluidic chip and bioreactor, to enable in situ tracking and imaging of brain organoids on-chip. The low-cost 3D printed microfluidic bioreactor supports organoid growth and provides an optimal imaging chamber for live-organoid imaging, with drug delivery support. This fully isolated design of a live-cell imaging and culturing platform enables long-term live-imaging of the intact live brain organoids as it grows. We can thus analyze their self-organization in a controlled environment with high temporal and spatial resolution.

A comprehensive review of the antibacterial, antifungal and antiviral potential of essential oils and their chemical constituents against drug-resistant microbial pathogens.

Essential oils are a complex mixture of odoriferous, volatile organic compounds. There are an extensive number of published articles which highlight the antimicrobial action of a variety of essential oils from various parts of the world. The main aim of this review article is to compile these antimicrobial essential oils and their constituents from reliable sources and put them together. The published literature indicates that essential oils possess a wide-spectrum of antibacterial, antifungal and even anti-viral activity. Essential oils have also been shown to inhibit the growth of drug-resistant microbial strains which are even difficult to be treated by conventional antibiotics. As for as their mode of action is concerned, in fungal pathogens, essential oils establish a membrane potential across cell wall and disrupt ATP assembly, leading to cell wall damage. Essential oils can also disintegrate mitochondrial membrane interfering with the electron transport system (ETS) pathway. In bacterial pathogens, essential oils primarily destabilize the cellular architecture, leading to breakdown of membrane integrity, disrupting many cellular activities including energy production and membrane transport. Membrane rupture induced by essential oils can lead to leakage of cellular components and loss of ions. Several essential oils have antiviral activities against many RNA and DNA viruses, such as type 1 and type 2 herpes simplex virus (HSV-1 and HSV-2), dengue virus type 2, influenza virusadeno virus type 3, poliovirus, Junin virus, and coxsackievirus B1. In conclusion, the current review article discusses in detail the various aspects of antimicrobial activity of essential oils in a comprehensive manner.

Secondary Metabolites from Endophytic Fungus Penicillium pinophilum Induce ROS-Mediated Apoptosis through Mitochondrial Pathway in Pancreatic Cancer Cells.

The endophytic fungus strain MRCJ-326, isolated from Allium schoenoprasum, which is also known as Snow Mountain Garlic or Kashmiri garlic, was identified as Penicillium pinophilum on the basis of morphological characteristics and internal transcribed spacer region nucleotide sequence analysis. The endophytic fungus extract was subjected to 2D-SEPBOX bioactivity-guided fractionation and purification. The anthraquinone class of the bioactive secondary metabolites were isolated and characterized as oxyskyrin (1), skyrin (2), dicatenarin (3), and 1,6,8-trihydroxy-3-hydroxy methylanthraquinone (4) by spectral analysis. Dicatenarin and skyrin showed marked growth inhibition against the NCI60/ATCC panel of human cancer cell lines with least IC50 values of 12 µg/mL and 27 µg/mL, respectively, against the human pancreatic cancer (MIA PaCa-2) cell line. The phenolic hydroxyl group in anthraquinones plays a crucial role in the oxidative process and bioactivity. Mechanistically, these compounds, i.e., dicatenarin and skyrin, significantly induce apoptosis and transmit the apoptotic signal via intracellular reactive oxygen species generation, thereby inducing a change in the mitochondrial transmembrane potential and induction of the mitochondrial-mediated apoptotic pathway. Our data indicated that dicatenarin and skyrin induce reactive oxygen species-mediated mitochondrial permeability transition and resulted in an increased induction of caspase-3 apoptotic proteins in human pancreatic cancer (MIA PaCa-2) cells. Dicatenarin showed a more pronounced cytotoxic/proapopotic effect than skyrin due to the presence of an additional phenolic hydroxyl group at C-4, which increases oxidative reactive oxygen species generation. This is the first report from P. pinophilum secreating these cytotoxic/proapoptotic secondary metabolites.

An inertial sensor-based system to develop motor capacity in children with cerebral palsy.

Learning to communicate with alternative augmentative communication devices can be difficult because of the difficulty of achieving controlled interaction while simultaneously learning to communicate. What is needed is a device that harnesses a child's natural motor capabilities and provides the means to reinforce them. We present a kinematic sensor-based system that learns a child's natural gestural capability and allows him/her to practice those capabilities in the context of a game. Movement is captured with a single kinematic sensor that can be worn anywhere on the body. A gesture recognition algorithm interactively learns gesture models using kinematic data with the help of a nearby teacher. Learned gesture models are applied in the context of a game to help the child practice gestures to gain better consistency. The system was successfully tested with a child over two sessions. The system learned four candidate gestures: lift hand, sweep right, twist right and punch forward. These were then used in a game. The child showed better consistency in performing the gestures as each session progressed. We aim to expand on this work by developing qualitative scores of movement quality and quantifying algorithm accuracy on a larger population over long periods of time.

All-fiber interferometry: design and analysis.

This paper presents a design procedure for a fiber interferometer, the optical system, and its associated electronic control. Analog and digital circuits were optimized to achieve an inexpensive and compact system. The lock-in amplifier required for phase control was designed using a field programmable gate array that was also configured to carry out the required phase stepping. The interferometer was built into two stages. The first stage used only one wavelength to measure samples with step heights in the hundreds of nanometers, with improvements in accuracy through averaging of data. The next stage included two measurement wavelengths to extend the measurement range to a few hundreds of micrometers. The paper conducts a systematic study of sources of errors. A least squares method that minimizes measurement time but retains accuracy has been used to measure height.

A new iridoid glycoside from Vitex negundo Linn (Verbenacea).

Five compounds have been isolated from the leaves of Vitex negundo Linn (Verbenacea) and their structures established by spectral analysis. Compound 1 has been identified and characterised as a new iridoid with a novel structure which has never before been reported in literature from Vitex or any other source. Its structure has been established as 1,4a,5,7a-tetrahydro-1-beta-D-glucosyl-7-(3',4'-dihydroxybenzoyloxymethyl)-5-ketocyclopenta[c]pyran-4-carboxylic acid. Other compounds, 2, 3, 4 and 5, have been identified as luteolin-7-O-beta-D glucoside, nishindaside, negundoside, and agnuside, respectively. Compound 2, a flavone-O-glycoside, is being reported from this plant for the first time, and compounds 3, 4 and 5 are structurally known iridoids.

Effect of chaotic vasomotion in skeletal muscle on tissue oxygenation.

Vasomotion refers to spontaneous variations in the lumen size of small vessels, with a plausible role in regulation of various aspects of microcirculation. We propose a computational model of vasomotion in skeletal muscle in which the pattern of vasomotion is shown to critically determine the efficiency of oxygenation of a muscle fiber. In this model, precapillary sphincters are modeled as nonlinear oscillators. We hypothesize that these sphincters interact via exchange of vasoactive substances. As a consequence, vasomotion is described as a phenomenon associated with a network of nonlinear oscillators. As a specific instance, we model the vasomotion of precapillary sphincters surrounding an active fiber. The sphincters coordinate their rhythms so as to minimize oxygen deficit in the fiber. Our modeling studies indicate that efficient oxygenation of the fiber depends crucially on the mode of interaction among the vasomotions of individual sphincters. While chaotic forms of vasomotion enhanced oxygenation, regular patterns of vasomotion failed to meet the oxygenation demand accurately.