Jason Lawrence Raymond

Hydroxyl-radical (˙OH) responsive fluorescent probes (Umb-DHB and Res-DHB) were developed that utilise the 3,5-dihydroxybenzyl (DHB) functionality. Res-DHB responded to ultrasound-induced hydroxyl radical production in solution and in cells.

Summary: The ability to directly modify native and established biofilms has enormous potential in understanding microbial ecology and application of biofilm in 'real‐world' systems. However, efficient genetic transformation of established biofilms at any scale remains challenging. In this study, we applied an ultrasound‐mediated DNA delivery (UDD) technique to introduce plasmid to established non‐competent biofilms in situ . Two different plasmids containing genes coding for superfolder green fluorescent protein (sfGFP) and the flavin synthesis pathway were introduced into established bacterial biofilms in microfluidic flow (transformation efficiency of 3.9 ± 0.3 × 10 ^‐7 cells in biofilm) and microbial fuel cells (MFCs), respectively, both employing UDD. Gene expression and functional effects of genetically modified bacterial biofilms were observed, where some cells in UDD‐treated Pseudomonas putida UWC1 biofilms expressed sfGFP in flow cells and UDD‐treated Shewanella oneidensis MR‐1 biofilms generated significantly ( P < 0.05) greater (61%) bioelectricity production (21.9 ± 1.2 µA cm ⁻² ) in MFC than a wild‐type control group (~ 13.6 ± 1.6 µA cm ⁻² ). The effects of UDD were amplified in subsequent growth under selection pressure due to antibiotic resistance and metabolism enhancement. UDD‐induced gene transfer on biofilms grown in both microbial flow cells and MFC systems was successfully demonstrated, with working volumes of 0.16 cm ³ and 300 cm ³ , respectively, demonstrating a significant scale‐up in operating volume. This is the first study to report on a potentially scalable direct genetic engineering method for established non‐competent biofilms, which can be exploited in enhancing their capability towards environmental, industrial and medical applications.

Acoustic droplet vaporization (ADV) is an important process that enables the theragnostic application of acoustically activated droplets, where the nucleation of inertial cavitation (IC) activity must be precisely controlled. This Letter describes threshold pressure measurements for ADV and acoustic emissions consistent with IC activity of lipid-shelled non-superheated perfluoropentane nanodroplets over a range of physiologically relevant concentrations at 1.1-MHz. Under the frequency investigated, results show that the thresholds were relatively independent of concentration for intermediate concentrations (105, 106, and 107 droplets/ml), thus indicating an optimal range of droplet concentrations for conducting threshold studies. For the highest concentration, the difference between the threshold for IC and the threshold for ADV was greatly reduced, suggesting that it might prove difficult to induce ADV without concomitant IC in applications that employ higher concentrations.

The measurement of cardiac and aortic pressures enables diagnostic insight into cardiac contractility and stiffness. However, these pressures are currently assessed invasively using pressure catheters. It may be possible to estimate these pressures less invasively by applying microbubble ultrasound contrast agents as pressure sensors. The aim of this study was to investigate the subharmonic response of the microbubble ultrasound contrast agent SonoVue (Bracco Spa, Milan, Italy) at physiological pressures using a static pressure phantom. A commercially available cell culture cassette with Luer connections was used as a static pressure chamber. SonoVue was added to the phantom, and radio frequency data were recorded on the ULtrasound Advanced Open Platform (ULA-OP). The mean subharmonic amplitude over a 40% bandwidth was extracted at 0-200-mmHg hydrostatic pressures, across 1.7-7.0-MHz transmit frequencies and 3.5%-100% maximum scanner acoustic output. The Rayleigh-Plesset equation for single-bubble oscillations and additional hysteresis experiments were used to provide insight into the mechanisms underlying the subharmonic pressure response of SonoVue. The subharmonic amplitude of SonoVue increased with hydrostatic pressure up to 50 mmHg across all transmit frequencies and decreased thereafter. A decreasing microbubble surface tension may drive the initial increase in the subharmonic amplitude of SonoVue with hydrostatic pressure, while shell buckling and microbubble destruction may contribute to the subsequent decrease above 125-mmHg pressure. In conclusion, a practical operating regime that may be applied to estimate cardiac and aortic blood pressures from the subharmonic signal of SonoVue has been identified.

It has been previously established that the subharmonic signal of microbubble ultrasound contrast agents follows an inverse linear relationship with the ambient hydrostatic pressure. However, contradictory results have been reported for SonoVue (Bracco Spa, Milan, Italy). Therefore, the aim of this study was to investigate the subharmonic response of SonoVue across a range of physiologically-relevant hydrostatic pressures (10–220 mmHg), and to compare it with Sonazoid (GE, Oslo, Norway). A modified GE Logiq 9 scanner was used to acquire the subharmonic signals from Sonazoid and SonoVue in a sealed water tank. In addition, the Ultrasound Advanced Open Platform (ULA-OP) was used to acquire the subharmonic signal of SonoVue at 0–200 mmHg in a cell culture cassette over approximately 3 min. Sonazoid showed an inverse linear relationship between subharmonic amplitude and hydrostatic pressure (slope −0.11 dB/mmHg; r = −0.81), as expected. SonoVue exhibited an increase in subharmonic amplitude from 0–100 mmHg hydrostatic pressure (slope 0.06 dB/mmHg, r = 0.81), a plateau between 100–140 mmHg, and a decrease from 140–220 mmHg (slope −0.26 dB/mmHg, r = −0.98). The subharmonic amplitude of SonoVue increased over 3 min at 0 and 25 mmHg hydrostatic pressure, did not change with time at 50–100 mmHg, and decreased over time at 125–200 mmHg. However, the effects of time on the subharmonic amplitude of SonoVue were smaller than the effects of hydrostatic pressure. The subharmonic response of SonoVue to hydrostatic pressure differs from Sonazoid and other microbubble ultrasound contrast agents.

The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-controlled water bath, however, there is scant data for optical properties of lesions created by HIFU. In this work, the optical scattering and absorption coefficients from 400-1300 nm of excised chicken breast exposed to HIFU were measured using an integrating sphere spectrophotometric technique. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. Results obtained over a range of thermal dose spanning 9 orders of magnitude show that the reduced scattering coefficient increases for HIFU exposures exceeding a threshold thermal dose of CEM43 = 600 ± 81 cumulative equivalent minutes. HIFU-induced thermal damage results in changes in scattering over all optical wavelengths, with a 2.5-fold increase for thermal lesions exceeding 70 °C. The tissue absorption coefficient was also found to increase for thermally lesioned tissue, however, the magnitude was strongly dependent on the optical wavelength and there was substantial sample-to-sample variability, such that the existence of a threshold thermal dose could not be determined. Therapeutic windows, where the optical penetration depth is expected to be greatest, were identified in the near infrared regime centered near 900 nm and 1100 nm. These data motivate further research to improve the real-time AO and PA sensing of lesion formation during HIFU therapy as an alternative to thermometry.

In May 2015, I arrived in London after completing my Ph.D. work under the direction of Prof. Christy Holland at the University of Cincinnati and moved shortly thereafter with a goal to help establish one of the principal physical acoustics laboratories in the UK at Oxford. At the outset, it was my hope and expectation that the F. V. Hunt Fellowship would help to define a unique trajectory for my career. During the fellowship and along with the support of my mentor, Prof. Ronald Roy, I have been able to develop a network of collaborators and conduct research which will help to define the next phase of my career and work in acoustics. A highlight of my term as a Hunt Fellow was the opportunity to travel to China, during which I visited four research laboratories relating to my work in therapeutic ultrasound and delivered two invited seminars. I am grateful to the Hunt family estate and the Acoustical Society of America for offering this fellowship, which has not only provided me with the opportunity to conduct research, but also the flexibility to develop as an independent scientist and to work with international collaborators.

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Baseline changes in optical properties have been previously measured as a function of thermal dose for chicken breast exposed to a temperature-controlled water bath (doi:10.1088/0031-9155/59/13/3249). In this work, the wavelength-dependent optical scattering and absorption coefficients of ex vivo chicken breast tissue exposed to HIFU were measured using an integrating sphere spectrophotometric technique employed previously. A focused HIFU transducer coupled to an acoustic lens was used to produce a large focal heating area in a thin (approximately 2 mm) section of tissue. Spatiotemporal surface temperature elevations were measured using an infrared camera and used to calculate the spatially dependent thermal dose delivered to a localized region of tissue as the exposure intensity and time were varied. Results will show how wavelength-dependent optical property changes can be used to improve the AO sensing of lesion formation during HIFU therapy as an alternative to thermometry and dosimetery. [Work supported by the F. V. Hunt Postdoctoral Fellowship, the University of Oxford, and EPSRC grant number EP/K02020X/1.]

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Baseline changes in optical properties have been previously measured as a function of thermal-dose for tissues exposed to a temperature-controlled water bath (doi:10.1088/0031-9155/59/13/3249). In this work, the wavelength-dependent optical scattering and absorption of ex vivo tissues exposed to HIFU were measured using an integrating sphere spectrophotometric technique employed previously. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. We consider the impact of thermal dose, temperature elevation, and heating rate on the formation of HIFU lesions and the resulting changes in tissue optical properties. Recently, reported results (doi:10.1088/0031-9155/59/13/3249) refute the hypothesis that optical property changes in tissue are based solely on accumulated thermal dose—this claim will be explored further through the optical characterization of lesions formed in clinically relevant tissues. Results will show how wavelength-dependent optical property changes in tissues can be used to improve the AO sensing of lesion formation during HIFU therapy as an alternative to thermometry. [Work supported by the ASA F.V. Hunt Fellowship and the University of Oxford.]

An optical characterization method is presented based on the use of the impulse response to characterize the damping imparted by the shell of an air-filled ultrasound contrast agent (UCA). The interfacial shell viscosity was estimated based on the unforced decaying response of individual echogenic liposomes (ELIP) exposed to a broadband acoustic impulse excitation. Radius versus time response was measured optically based on recordings acquired using an ultra-high-speed camera. The method provided an efficient approach that enabled statistical measurements on 106 individual ELIP. A decrease in shell viscosity, from 2.1 × 10−8 to 2.5 × 10−9 kg/s, was observed with increasing dilatation rate, from 0.5 × 106 to 1 × 107 s−1. This nonlinear behavior has been reported in other studies of lipid-shelled UCAs and is consistent with rheological shear-thinning. The measured shell viscosity for the ELIP formulation used in this study [κs = (2.1 ± 1.0) × 10−8 kg/s] was in quantitative agreement with previously reported values on a population of ELIP and is consistent with other lipid-shelled UCAs. The acoustic response of ELIP therefore is similar to other lipid-shelled UCAs despite loading with air instead of perfluorocarbon gas. The methods described here can provide an accurate estimate of the shell viscosity and damping for individual UCA microbubbles.