Biology subjects

Rowlands, C. J.

Publications and source records attributed to Rowlands, C. J..

4 recordsLinked to original sources

bioRxiv2024

Synthesis of arbitrary interference patterns using a single galvanometric mirror, and its application to Structured Illumination Microscopy

We present a new interferometer concept called SWIFT, able to project arbitrary interference patterns constructed from small numbers of plane waves. SWIFT can control each plane waves orientation, intensity, polarization and phase using just a single galvanometric mirror. We demonstrate the application of SWIFT to both 2D and 3D Structured Illumination Microscopy, characterizing performance on fluorescent nanoparticles and iFluor 488 phalloidin-stained U-2 OS cells.

bioengineering↗

bioRxiv2023

Microbubble dynamics in brain microvessels

BackgroundFocused ultrasound stimulation of microbubbles is being tested in clinical trials for its ability to deliver drugs across the blood-brain barrier (BBB). This technique has the potential to treat neurological diseases by preferentially delivering drugs to targeted regions. Yet despite its potential, the physical mechanisms by which microbubbles alter the BBB permeability remain unclear, as direct observations of microbubbles oscillating in cerebral capillaries have never been previously recorded. The purpose of this study was to reveal how microbubbles respond to ultrasound when within the microvessels of living brain tissue. MethodsMicrobubbles in acute brain slices acquired from juvenile rats perfused with a concentrated solution of SonoVue(R) and dye were exposed to ultrasound pulses typically used in BBB disruption (center frequency: 1 MHz, peak-negative pressure: 0.2-1 MPa, pulse length: up to 10 ms) and observed using high-speed microscopy at up to 10 million frames per second. ResultsWe observed that microbubbles can exert mechanical stresses on a wide region of tissue beyond their initial location and immediate surroundings. A single microbubble can apply mechanical stress to parenchymal tissues several micrometers away from the vessel. Microbubbles can travel at high velocities within the microvessels, extending their influence across tens of micrometers during a single pulse. With longer pulses and higher pressures, microbubbles could penetrate the vessel wall and move through the parenchyma, refuting a previous assumption that microbubbles are confined to vessels. The probability of extravasation scales approximately with mechanical index, being rare at low pressures, but much more common at a mechanical index [≥] 0.6. ConclusionsThese observations provide important insight into microbubble dynamics in microvessels, and are critical leads into ultimately identifying the microbubble activities that lead to both safe drug delivery and into activities we seek to avoid, such as petechiae and other bioeffects.

bioengineering↗

bioRxiv2023

Hyperspectral Oblique Plane Microscopy

Spontaneous Raman imaging has emerged as powerful label-free technique for investigating the molecular composition of biological specimens. Although Raman imaging can facilitate understanding of complex biological phenomena in vivo, current imaging modalities are limited in speed and sample compatibility. Here, we introduce a single-objective light-sheet microscope, named{lambda} -OPM, which records Raman images on a timescale of minutes to milliseconds. To demonstrate its function, we use{lambda} -OPM to map and identify micro-plastic particles based on their Raman spectral characteristics. In live zebrafish embryos, we show that{lambda} -OPM can capture wound dynamics at five-minute intervals, revealing rapid changes in cellular and extracellular matrix composition in the wounded region. Finally, we use{lambda} -OPM to obtain Raman scattering maps of a zebrafish embryos beating heart at an effective 28 frames per second, recording compositional changes at different points in the cardiac cycle.

bioengineering↗

bioRxiv2022

Shortwave-Infrared Line-Scan Confocal Microscope for Deep Tissue Imaging in Intact Organs

Imaging at wavelengths beyond the visible spectrum enables imaging depths of hundreds of microns in intact tissue, making this attractive for volumetric imaging applications. The development of fluorophores with photoemission beyond 1000nm provide the opportunity to develop novel fluorescence microscopes sensitive to those wavelengths. Here, we present a shortwave-infrared line-scan confocal microscope that is capable of deep imaging of biological specimens, as demonstrated by visualization of labelled glomeruli in a fixed uncleared kidney at depths beyond 400 m. We also show imaging of brain vasculature labelled with the near-infrared organic dye indocyanine green, the shortwave-infrared organic dye Chrom7, and rare earth-doped nanoparticles, thus encompassing the entire spectrum detectable by a typical shortwave-infrared sensitive InGaAs detector.

bioengineering↗