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Oncolytic viruses (OV) and ultrasound-enhanced drug delivery are powerful novel technologies. OV selectively self-amplify and kill cancer cells but their clinical use has been restricted by limited delivery from the bloodstream into the tumor. Ultrasound has been previously exploited for targeted release of OV in vivo, but its use to induce cavitation, microbubble oscillations, for enhanced OV tumor extravasation and delivery has not been previously reported. By identifying and optimizing the underlying physical mechanism, this work demonstrates that focused ultrasound significantly enhances the delivery and biodistribution of systemically administered OV co-injected with microbubbles. Up to a fiftyfold increase in tumor transgene expression was achieved, without any observable tissue damage. Ultrasound exposure parameters were optimized as a function of tumor reperfusion time to sustain inertial cavitation, a type of microbubble activity, throughout the exposure. Passive detection of acoustic emissions during treatment confirmed inertial cavitation as the mechanism responsible for enhanced delivery and enabled real-time monitoring of successful viral delivery.

We investigated whether ultrasound-induced cavitation at 0.5 MHz could improve the extravasation and distribution of a potent breast cancer-selective oncolytic adenovirus, AdEHE2F-Luc, to tumour regions that are remote from blood vessels. We developed a novel tumour-mimicking model consisting of a gel matrix containing human breast cancer cells traversed by a fluid channel simulating a tumour blood vessel, through which the virus and microbubbles could be made to flow. Ultrasonic pressures were chosen to maximize either broadband emissions, associated with inertial cavitation, or ultraharmonic emissions, associated with stable cavitation, while varying duty cycle to keep the total acoustic energy delivered constant for comparison across exposures. None of the exposure conditions tested affected cell viability in the absence of the adenovirus. When AdEHE2F-Luc was delivered via the vessel, inertial cavitation increased transgene expression in tumour cells by up to 200 times. This increase was not observed in the absence of Coxsackie and Adenovirus Receptor cell expression, discounting sonoporation as the mechanism of action. In the presence of inertial cavitation, AdEHE2F-Luc distribution was greatly improved in the matrix surrounding the vessel, particularly in the direction of the ultrasound beam; this enabled AdEHE2F-Luc to kill up to 80% of cancer cells within the ultrasound focal volume in the gel 24 hours after delivery, compared to 0% in the absence of cavitation. © 2011 Elsevier Ltd. All rights reserved.

Using a large consortium of undergraduate students in an organized program at the University of California, Los Angeles (UCLA), we have undertaken a functional genomic screen in the Drosophila eye. In addition to the educational value of discovery-based learning, this article presents the first comprehensive genomewide analysis of essential genes involved in eye development. The data reveal the surprising result that the X chromosome has almost twice the frequency of essential genes involved in eye development as that found on the autosomes.

A flow-through tissue-mimicking phantom composed of a biocompatible hydro-gel with embedded tumour cells was used to assess and optimize the role of ultrasound-induced cavitation on the extravasation of a macromolecular compound from a channel mimicking vessel in the gel, namely a non-replicating luciferase-expressing adenovirus (Ad-Luc). Using a 500 KHz therapeutic ultrasound transducer confocally aligned with a focussed passive cavitation detector, different exposure conditions and burst mode timings were selected by performing time and frequency domain analysis of passively recorded acoustic emissions, in the absence and in the presence of ultrasound contrast agents acting as cavitation nuclei. In the presence of Sonovue, maximum ultraharmonic emissions were detected for peak rarefactional pressures of 360 kPa, and maximum broadband emissions occurred at 1250 kPa. The energy of the recorded acoustic emissions was used to optimise the pulse repetition frequency and duty cycle in order to maximize either ultraharmonic or broadband emissions while keeping the acoustic energy delivered to the focus constant. Cell viability measurements indicated that none of the insonation conditions investigated induces cell death in the absence of a therapeutic agent (i.e. virus). Phase contrast images of the tissue-mimicking phantom showed that short range vessel disruption can occur when ultra-harmonic emissions (nf0/2) are maximised whereas formation of a micro-channel perpendicular to the flow can be obtained in the presence of broadband acoustic emissions. Following Ad-Luc delivery, luciferase expression measurements showed that a 60-fold increase in its bioavailability can be achieved when broadband noise emissions are present during insonation, even for modest contrast agent concentrations. The findings of the present study suggest that drug delivery systems based on acoustic cavitation may help enhance the extravasation of anticancer agents, thus increasing their penetration distance to hypoxic regions and poorly vascularised tumour regions.

Poor drug penetration through tumor tissue has emerged as a fundamental obstacle to cancer therapy. The aim of this study was to examine the ability of cavitation instigated by high-intensity focused ultrasound (HIFU) to increase convective transport of a model therapeutic in an in vitro tumor model. Cavitation activity was quantified by analyzing passively recorded acoustic emissions, and mass transfer was quantified using post-treatment image analysis of the distribution of a dye-labeled macromolecule. The strong correlation between cavitation activity and drug delivery suggests the potential for non-invasive treatment and monitoring.

Forecasting of the future commercial value of drugs is a crucial activity that affects many decisions by pharmaceutical companies. However, this analysis indicates that many forecasts are wrong, often substantially.

Stable and inertial cavitation have been shown to play a key role in several therapeutic ultrasound applications, ranging from non-invasive ablation to drug delivery. In order to achieve meaningful quantification of therapeutically relevant cavitation, a hypothesis as to the underlying mechanism by which bubbles enhance energy delivery and momentum transfer to their surroundings must first be formulated. Based on this hypothesis, correlations can be sought between time-based or frequency-based metrics of a relevant cavitation 'dose' and the desirable associated bioeffects, enabling the establishment of thresholds for therapeutically relevant processes to occur. However, the problem is complicated further by the fact that a single type of cavitation activity rarely occurs throughout an ultrasound exposure, or throughout the acoustic field of a therapeutic transducer. A recently developed method, known as passive acoustic mapping, makes it possible to obtain real-time maps of inertial and stable cavitation activity and could thus enable improved dosimetry of therapeutically relevant cavitational processes. The use of passive acoustic mapping for spatiotemporal classification and quantification of cavitation will be illustrated in the context of HIFU ablation, drug release from thermosensitive liposomes and drug delivery.

Acoustic cavitation has been recently shown to have tremendous potential as a mechanism for releasing and enabling improved uptake and biodistribution of therapeutic agents for the pharmacological treatment of cancer, cardiovascular, and neurodengenerative diseases. Passive cavitation mapping makes it possible to localize, characterize, and quantify cavitation activity by detecting the acoustic emissions produced by cavitating bubbles on an array of receivers, which are then back‐propagated to form a cavitation‐selective image with high spatio‐temporal accuracy. In the present study, a 64‐element diagnostic linear array was used to construct passive cavitation maps during pulsed HIFU exposure of a narrow channel transporting fluorescent dextran nanoparticles through a biocompatible porous hydrogel in the presence or absence of ultrasound contrast agents. Spectral analysis of the resulting acoustic emissions confirmed that different cavitation regimes were successfully instigated over the HIFU parameter range that was investigated. Superposition of cavitation selective images over the treatment course was used to construct maps of cavitation activity and dose as a function of location for treatment assessment and was found to correlate well with dextran extravasation. It is concluded that passive mapping of cavitation activity shows great promise for assessment and real‐time monitoring of cavitation based drug delivery.

The excitement of scientific research and discovery cannot be fully conveyed by didactic lectures alone. Several recent initiatives and proposals, therefore, have supported a more participatory, discovery-based instruction for undergraduate science education [1,2]. In functional genomics, we have found an ideal platform to simultaneously benefit students and contribute to scientific discovery. The sequencing of eukaryotic genomes has facilitated the identification of complete sets of genes in humans and model genetic organisms. This has allowed many forms of high-throughput analyses of transcriptional profiles, protein interactions, structural motifs, and even genome-wide knock-downs in cell lines or in selected organisms. However, one of the best tools to provide functional information about gene action— obtaining in vivo evidence about the phenotype resulting from heritable loss of function—is difficult and less amenable to high-throughput research. We were able to achieve a large-scale in vivo analysis with a significant number of undergraduate students at UCLA, called the UCLA Undergraduate Consortium for Functional Genomics. This work, a practical manifestation of policy positions proposing discoverybased education, is described in summary form here (and in Box 1) and in detail online at http://www.bruinfly.ucla.edu. This effort combines professional-quality research with a strategy for research-based undergraduate education.