Advances in diagnostic technologies enabled scientists to link a large number of diseases with structural changes of the intracellular organisation. This intrinsic biophysical characteristic opened up the possibility to perform clinical assessments based on the measurement of single-cell mechanical properties. In this work, we combine microfluidics, high speed imaging and computational automatic tracking to measure the single-cell deformability of large samples of prostate cancer cells at a rate of ~ 104cells/s. Such a high throughput accounts for the inherent heterogeneity of biological samples and enabled us to extract statistically meaningful signatures from each cell population. In addition, using our technique we investigate the effect of Latrunculin A to the cellular stiffness.
We investigated the occurrence of small but significant inaccuracies in the temporal integrity of a commercial high-speed
[rotating mirror] imaging system (a Cordin 550-62 camera). Utilizing a relatively straightforward hardware addition,
independent measurements of the actual frame rate at the point of camera triggering were conducted, and then compared
to the Cordin system's self-reported frame rate values for each recording. The present data thus represents a follow-up to
our earlier preliminary report on this instrument's performance, where we initially discovered that disparities between
the true and reported values could arise. Interestingly, the data trends observed in the present report suggest a disparity,
the nature of which is consistent with the Cordin camera reporting a frame rate that arises a short time before the trigger
event, i.e. that the system's sampling algorithm senses the frame rate with a finite pre-trigger implemented, which runs
counter to the procedure suggested by the manufacturer. As well as presenting the context, and supporting evidence for
our own conclusions, we also developed an approach to reduce the error in the reported values by a factor of 7, from an
average of 0.78% +/- 0.04% to 0.11% +/- 0.08% over the present data set.
This study has observed microscopic level cavitation processes in shelled second generation ultrasound contrast agent
microbubbles. The spatial and temporal resolutions required for this undertaking have been achieved via a unique
hybridisation of optical trapping with ultra high speed microphotography. Upon insonation with ultrasound in the region
of 0.5-4MPa, microjets were observed to develop within, and subsequently issue from, cavitating bubbles. Jet impact
into target substrates, including monolayers of biological cells, was observed. These observations provide direct
evidence for the involvement of microjetting events during ultrasound exposure on live cells, a process that may have
future potential as a novel non-invasive route to drug- and gene-based therapies.
Sonoluminescence (SL) involves the conversion of mechanical [ultra]sound energy into light. Whilst the phenomenon is
invariably inefficient, typically converting just 10-4 of the incident acoustic energy into photons, it is nonetheless
extraordinary, as the resultant energy density of the emergent photons exceeds that of the ultrasonic driving field by a
factor of some 1012. Sonoluminescence has specific [as yet untapped] advantages in that it can be effected at remote
locations in an essentially wireless format. The only [usual] requirement is energy transduction via the violent oscillation
of microscopic bubbles within the propagating medium. The dependence of sonoluminescent output on the generating
sound field's parameters, such as pulse duration, duty cycle, and position within the field, have been observed and
measured previously, and several relevant aspects are discussed presently. We also extrapolate the logic from a recently
published analysis relating to the ensuing dynamics of bubble 'clouds' that have been stimulated by ultrasound. Here, the
intention was to develop a relevant [yet computationally simplistic] model that captured the essential physical qualities
expected from real sonoluminescent microbubble clouds. We focused on the inferred temporal characteristics of SL light
output from a population of such bubbles, subjected to intermediate [0.5-2MPa] ultrasonic pressures. Finally, whilst
direct applications for sonoluminescent light output are thought unlikely in the main, we proceed to frame the state-of-the-
art against several presently existing technologies that could form adjunct approaches with distinct potential for
enhancing present sonoluminescent light output that may prove useful in real world [biomedical] applications.
Cells that are exposed to varying amounts of ultrasonic energy in the presence of ultrasound contrast agent (UCA) may undergo either permanent cell membrane damage (lethal sonoporation), or a transient enhancement of membrane permeability (reversible or non lethal sonoporation). The merits of each mode are clear; lethal sonoporation constitutes a significant tumour therapy weapon, whilst its less intrusive counterpart, reversible sonoporation, represents an effective non-invasive targeted drug delivery technique.
Our working hypothesis for understanding this problem was that the root cause and effect in sonoporation involves the interaction of individual cells with single microbubbles, and to that end we devised an experiment that facilitates video rate observation of this specific scenario under well defined optical control. Specifically, we have constructed an innovative hybridization apparatus involving holographic optical trapping of single and multiple UCA microbubbles, together with the facility to irradiate with MHz pulsed ultrasound energy in the presence cancerous cells. This approach allows the isolation of a target microbubble from a resident population and the relocation to a [controllable] predetermined position relative to a cell within a monolayer. Frame extraction from standard framing rate video microscopy demonstrates the individuality of single microbubble-cell interactions. We describe a fluorescence microscopy protocol that will allow future study of the potential to deliver molecular species to cells, the dependence of the delivery on the initial microbubble-cell distance and to determine the targeted cell survival.