Developing a drug delivery vehicle that can control the release kinetics of a therapeutic drug on demand has great potential to improve health by allowing health care professionals to maintain the drug concentration in its therapeutic window and increase the efficiency at which treatment is administered. On-demand release can be triggered by a range of stimuli including magnetic, radiation, and ultrasound activation. Of the three, ultrasound is the only one indiscriminate of the chemical properties of the material and is the most widely available clinically, which makes it versatile and applicable for many systems. However, existing strategies that use ultrasound as a release stimulus either pop the microcapsules altogether (enabling no subsequent effective control over the kinetics of drug release) or require continuous ultrasonic administration (typically impractical in a clinical setting), both of which are suboptimal. Overcoming at least of these shortcomings would vastly improve on the technology. In this thesis, microcapsules with a complex shell were fabricated using a modified electrohydrodynamic approach named immersion coaxial electrospraying, which allowed for an increased polymer loading in the shell and improved manipulation of microcapsule size. The complex shell structure of the microcapsules incorporated silica microparticles that acted as corks plugging pores between the inside and outside of the microcapsule. The modified microcapsules were shown to release their payload in the presence of a focused ultrasound signal, while uncorked microcapsules do not release. Release kinetics were shown to be adjustable based on the number of corks initially present in the shell of the microcapsule material. Altogether, the cork-shell microcapsules fabricated in this thesis show promise as a tunable on-demand drug delivery vehicle that is able to better control release compared to conventional ultrasound triggered microcapsules. / Thesis / Master of Applied Science (MASc) / This thesis focuses on the fabrication of complex microcapsules that can be deliver therapeutic drugs on-demand using ultrasound waves. These microcapsules are composed of a water-based core and a biologically inert shell into which particles are embedded. Upon the application of ultrasound, these embedded particles (like corks on a bottle) are popped out to release the “corks” from the shell, creating pores from which the drug in the microcapsule core can be released. In the absence of ultrasound signals, the microcapsules do not release any of their contents, making these effective for “on-demand” release. These microcapsules are made using a modified process based on electrospraying which allows very precise control over the microcapsules’ physical properties, incorporating a key modification that overcomes an inherent issue with the general technique. These microcapsules also improve on currently used ultrasound triggered drug delivery systems by requiring shorter periods of ultrasound and/or enabling better control over the dynamics of drug release following the ultrasound pulse.

Background: Achilles tendinopathy is a common and debilitating condition among female ballet dancers due to the large repetitive loading forces placed on their Achilles tendons during rehearsals and performances. Tendon health problems in females are exacerbated by a lack of understanding about how energy availability influences tendons. Ballet dancers, as aesthetic athletes, are vulnerable to low energy availability and can enter a spectrum disorder, relative energy deficiency in sport, that consists of low energy availability (with or without disordered eating), menstrual cycle dysfunction, and low bone mineral density (BMD). Aims: 1) To investigate the relationship between insufficient caloric intake and Achilles tendon health in pre-professional ballet dancers. 2) To evaluate if symptoms of relative energy deficiency in sport such as low BMD and menstrual irregularity can be matched with Achilles tendon structural damage in pre-professional ballet dancers. 3) To analyze if there is a relationship between BMD and nutrition in pre-professional ballet dancers. Methods: 30 pre-professional ballet dancers were recruited. Over the course of a 16-week training and performance period, the dancers underwent four ultrasound imaging sessions and two MRI sessions investigating their Achilles tendons. They also underwent one full body DXA scan and completed four ASA24 dietary recall surveys. The dancers additionally filled out questionnaires describing their menstrual history and current Achilles tendon health. At the end of the study, dancers were organized into calorie sufficiency groups (sufficient or insufficient). Results: Within both calorie groups, the Achilles tendon was significantly thicker at the end of the study as compared to the start of the study (p=.046). Within both calorie groups, echogenicity was significantly higher at the first two ultrasound imaging sessions than it was at the last two (p<.05). Additionally, the calorie sufficient group's tendons had a significantly higher echogenicity than the calorie insufficient group at the first two ultrasound imaging sessions (p<.05). There were significantly more dancers in the calorie insufficient group that experienced changes to their menstrual cycle (p=.007). Conclusion: Participants in the calorie sufficient group had significantly more hyperechoic tendons than those in the calorie insufficient group at the start of the study, and all participants saw a significant drop in tendon echogenicity halfway through the study. The results of this study suggest that a better understanding of how average caloric intake affects tendon health in dancers is necessary in order to help treat and prevent AT injuries in this dance population.

Nanoparticle-based delivery vehicles have received substantial interest in the field of drug delivery particularly pertaining to chemotherapeutics. By virtue of their size, nanoscale drug delivery vehicles overcome many obstacles encountered by traditional systems. Moreover, nanocarriers can be fabricated to be ‘smart’, meaning they can be responsive to internal stimuli relating to the microenvironment of the tumor and/or external stimuli that can be delivered non-invasively from outside of the body. One such external trigger is ultrasound, well-known for its role in biomedical imaging based on its wide availability, non-invasiveness, and safety but increasingly being applied for drug delivery. This thesis proposes solutions to two key challenges associated with locally-targeted polymer-based drug delivery: enhanced tumor accumulation and externally-triggered control over release kinetics. In the former case, brush polymer PLA-PEG analogues are synthesized and explored to correlate how the architecture of these brush blocks affects the resulting self-assembled nanoparticle size, zeta potential, cytotoxicity in vitro, circulation time, and accumulation profiles in vivo. Indeed, brush copolymer analogues allow for copolymerization with additional monomers while conserving ‘stealth properties of linear copolymers, as well as exhibit superior circulation times and longer-term tumor accumulation. In the latter case, a new ultrasound-triggered drug delivery platform is designed consisting of a hollow polymeric shell in which silica “corks” are entrapped; the application of ultrasound can exploit the high difference in the compressibility between the polymeric shell and the silica corks to pop out or otherwise perturb the cork particles, allowing for both on-demand drug release as well as a pulsatile release profiles to be achieved. Overall, by manipulating the surface properties and/or morphologies of polymer-based micro/nanoparticles, the results of this thesis show that key challenges in local drug delivery can be addressed and applied specifically to applications in cancer therapy. / Dissertation / Doctor of Philosophy (PhD) / Drug delivery vehicles attempt to address many of the shortcomings of traditional therapeutics, in particular their low solubility and a lack of tissue targeting, which result in poor efficacy and unwanted side-effects. Polymers specifically have been commonly employed in biomedical applications as there are a wide range of biodegradable polymers that do not cause adverse effects during intended application and can be removed from the body through normal biological function. More recently, more advanced, ‘smart’ materials have been developed that can respond to internal or external stimuli to better address treatment needs. This thesis presents novel polymer-based drug delivery vehicles with new structures useful to passively target particular sites in the body and/or alter drug release profiles, enabling improved drug efficacy and reduced side-effects.

The ability of Listeria monocytogenes, to attach to various food contact surfaces such as stainless steel, polypropylene, and rubber compounds is well documented. The retention of these or other pathogenic bacteria on food contact surfaces increases the risk of transmission to food products. The objective of this study was to compare several methods for quantitative recovery of Listeria monocytogenes from stainless steel surfaces. A cocktail of four serotypes of Listeria monocytogenes (Scott A (4b)), 1/2b, 3b, and 4b) were mixed in equivalent concentrations and inoculated onto type 304 stainless steel coupons in a 2cm x 2cm area. After a one hour exposure, coupons were sampled by one of the following methods: 1) swabbing using a pre-moistened Dacron swab, 2) rinsing with phosphate buffered saline, 3) direct contact onto a Tryptic Soy Agar containing 0.6% yeast extract (TSA+YE) plate surface for 10 seconds, 4) sonication in an ultrasonic water bath (40 kHz), 5) contact with the bristles of a sonicating brush head for 1 min, and 6) indirect contact (2-4 mm) with the bristles of a sonicating brush head for 1 min. Coupon rinses were plated onto TSA containing 0.6% yeast extract and incubated for 24 hours at 35°C. The three sonication methods yielded higher recovery than the other three methods (p < 0.05). Brushing the coupons with the sonicating brush head yielded a recovery level of 58% and indirect exposure to the sonicating brush head permitted a recovery level of 65% from the initial microbial load. The lowest cell recovery (~20%) was observed with the swab and direct agar contact methods. / Master of Science

There is currently no solution for imaging fibrin-rich adhesions following surgery, yet the condition costs healthcare providers upwards of $2 billion annually. Over the past decade the development of ultrasound contrast agents has seen an increase in commercialization of generic microbubble formulations for standard diagnostic applications such as echocardiography. To enhance diagnostic power, molecularly targeted microbubbles are formulated with the addition of a ligand to the outer shell. The microbubble formulation must be modified so that the contrast agents are stable over time and targeted with the appropriate ligand while maintaining their echogenicity relative to surrounding soft tissue. We used a dual approach to look at microbubbles optically to predict their relative signal enhancement in vivo given their size distribution and concentration. An ImageJ macro script was developed based off BubblesizerJ, a previously developed open-source program. To confirm that modified microbubbles maintain acoustic properties relative to soft tissue, an agarose phantom model was developed that allows for high throughput testing of multiple microbubble formulations. / 2026-09-03T00:00:00Z

Yes / The hydrophobicity of a drug can be a major challenge in its development and prevents the clinical translation of highly potent anti-cancer agents. We have used a lipid-based nanoemulsion termed Lipid-Oil-Nanodroplets (LONDs) for the encapsulation and in vivo delivery of the poorly bioavailable Combretastatin A4 (CA4). Drug delivery with CA4 LONDs was assessed in a xenograft model of colorectal cancer. LC-MS/MS analysis revealed that CA4 LONDs, administered at a drug dose four times lower than drug control, achieved equivalent concentrations of CA4 intratumorally. We then attached CA4 LONDs to microbubbles (MBs) and targeted this construct to VEGFR2. A reduction in tumor perfusion was observed in CA4 LONDs-MBs treated tumors. A combination study with irinotecan demonstrated a greater reduction in tumor growth and perfusion (P = 0.01) compared to irinotecan alone. This study suggests that LONDs, either alone or attached to targeted MBs, have the potential to significantly enhance tumor-specific hydrophobic drug delivery. / The work was funded by the Medical Research Council (grant number: MR/L01629X MRC Medical Bioinformatics Centre) and the EPSRC (grant number EP/P023266/1 Health Impact Partnership). EPSRC (EP/I000623/1, EP/K023845/1). Laura E. McVeigh was funded by an EPSRC PhD Studentship (EP/L504993/1).

Yes / Advanced drug delivery systems, such as ultrasound-mediated drug delivery, show great promise for increasing the therapeutic index. Improvements in delivery by altering the ultrasound parameters have been studied heavily in vitro but relatively little in vivo. Here, the same therapeutic microbubble and tumour type are used to determine whether altering ultrasound parameters can improve drug delivery. Liposomes were loaded with SN38 and attached via avidin: biotin linkages to microbubbles. The whole structure was targeted to the tumour vasculature by the addition of anti-vascular endothelial growth factor receptor 2 antibodies. Tumour drug delivery and metabolism were quantified in SW480 xenografts after application of an ultrasound trigger to the tumour region. Increasing the trigger duration from 5 s to 2 min or increasing the number of 5 s triggers did not improve drug delivery, nor did changing to a chirp trigger designed to stimulate a greater proportion of the microbubble population, although this did show that the short tone trigger resulted in greater release of free SN38. Examination of ultrasound triggers in vivo to improve drug delivery is justified as there are multiple mechanisms at play that may not allow direct translation from in vitro findings. In this setting, a short tone burst gives the best ultrasound parameters for tumoural drug delivery. / This research was funded by the EPSRC (EP/I000623/1, EP/L504993/1 and EP/P023266/1). S.D.E. is supported by the National Institute for Health Research infrastructure at Leeds. J.R.M. is supported by an EPSRC UKRI Innovation Fellowship (EP/S001069/1).

Yes / An ultrasound sensor system has been applied to the mould of both the water and gas assisted injection moulding processes. The mould has a cavity wall mounted pressure sensor and instrumentation to monitor the injection moulding machine. Two ultrasound sensors are used to monitor the arrival of the fluid (gas or water) bubble tip through the detection of reflected ultrasound energy from the fluid polymer boundary and the fluid bubble tip velocity through the polymer melt is estimated. The polymer contact with the cavity wall is observed through the reflected ultrasound energy from that boundary. A theoretically based estimation of the residual wall thickness is made using the ultrasound reflection from the fluid (gas or water) polymer boundary whilst the samples are still inside the mould and a good correlation with a physical measurement is observed.

Yes / In recent years, imaging has played an increasing role in the clinical management of patients with rheumatic diseases with respect to aiding diagnosis, guiding therapy and monitoring disease progression. These roles have been underpinned by research which has enhanced our understanding of disease pathogenesis and pathophysiology of rheumatology conditions, in addition to their key role in outcome measurement in clinical trials. However, compared to joints, imaging research of muscles is less established, despite the fact that muscle symptoms are very common and debilitating in many rheumatic diseases. Recently, it has been shown that even though patients with rheumatoid arthritis may achieve clinical remission, defined by asymptomatic joints, many remain affected by lingering constitutional systemic symptoms like fatigue, tiredness, weakness and myalgia, which may be attributed to changes in the muscles. Recent improvements in imaging technology, coupled with an increasing clinical interest, has started to ignite new interest in the area. This perspective discusses the rationale for using imaging, particularly ultrasound and MRI, for investigating muscle pathology involved in common inflammatory rheumatic diseases. The muscles associated with rheumatic diseases can be affected in many ways, including myositis—an inflammatory muscle condition, and myopathy secondary to medications, such as glucocorticoids. In addition to non-invasive visual assessment of muscles in these conditions, novel imaging techniques like shear wave elastography and quantitative MRI can provide further useful information regarding the physiological and biomechanical status of the muscle. / This research is funded by the NIHR infrastructure at Leeds.

The use of brightness mode (B-mode) ultrasound (US), color Doppler (CD), and power Doppler (PD) can all help evaluate and characterize splenic lesions. A relatively new non-Doppler technology used to evaluate vasculature called B-Flow helps overcome certain limitations of CD and PD that affect visualization of blood flow. There are no studies describing the use of B-Flow characterizing splenic lesions in dogs. A total of 97 splenic lesions were evaluated. Splenic lesions that were larger than 2 cm, distorted the splenic capsule, or accompanied free fluid were significantly associated with malignancy. Lesions with tortuous internal vessels on CD or B-Flow were significantly associated with malignancy. Lesions with large internal vessels compared to external vessels on PD and B-Flow were significantly associated with malignancy. In conclusion, these B-mode and vascular characteristics on CD, PD and B-flow may help clinicians prioritize malignant etiologies over benign ones and prompt more aggressive diagnostic recommendations.