Reducing Tumour Hypoxia via Oral Administration of Oxygen Nanobubbles.

Hypoxia has been shown to be a key factor inhibiting the successful treatment of solid tumours. Existing strategies for reducing hypoxia, however, have shown limited efficacy and/or adverse side effects. The aim of this study was to investigate the potential for reducing tumour hypoxia using an orally delivered suspension of surfactant-stabilised oxygen nanobubbles. Experiments were carried out in a mouse xenograft tumour model for human pancreatic cancer (BxPc-3 cells in male SCID mice). A single dose of 100 µL of oxygen saturated water, oxygen nanobubbles or argon nanobubbles was administered via gavage. Animals were sacrificed 30 minutes post-treatment (3 per group) and expression of hypoxia-inducible-factor-1α (HIF1α) protein measured by real time quantitative polymerase chain reaction and Western blot analysis of the excised tumour tissue. Neither the oxygen saturated water nor argon nanobubbles produced a statistically significant change in HIF1α expression at the transcriptional level. In contrast, a reduction of 75% and 25% in the transcriptional and translational expression of HIF1α respectively (p<0.001) was found for the animals receiving the oxygen nanobubbles. This magnitude of reduction has been shown in previous studies to be commensurate with an improvement in outcome with both radiation and drug-based treatments. In addition, there was a significant reduction in the expression of vascular endothelial growth factor (VEGF) in this group and corresponding increase in the expression of arrest-defective protein 1 homolog A (ARD1A).

Comparing the efficacy of photodynamic and sonodynamic therapy in non-melanoma and melanoma skin cancer.

Sonodynamic therapy (SDT) involves the activation of a non-toxic sensitiser drug using low-intensity ultrasound to produce cytotoxic reactive oxygen species (ROS). Given the low tissue attenuation of ultrasound, SDT provides a significant benefit over the more established photodynamic therapy (PDT) as it enables activation of sensitisers at a greater depth within human tissue. In this manuscript, we compare the efficacy of aminolevulinic acid (ALA) mediated PDT and SDT in a squamous cell carcinoma (A431) cell line as well as the ability of these treatments to reduce the size of A431 ectopic tumours in mice. Similarly, the relative cytotoxic ability of Rose Bengal mediated PDT and SDT was investigated in a B16-melanoma cell line and also in a B16 ectopic tumour model. The results reveal no statistically significant difference in efficacy between ALA mediated PDT or SDT in the non-melanoma model while Rose Bengal mediated SDT was significantly more efficacious than PDT in the melanoma model. This difference in efficacy was, at least in part, attributed to the dark pigmentation of the melanoma cells that effectively filtered the excitation light preventing it from activating the sensitiser while the use of ultrasound circumvented this problem. These results suggest SDT may provide a better outcome than PDT when treating highly pigmented cancerous skin lesions.

Diagnostic and Therapeutic Applications of Quantum Dots in Nanomedicine.

The interest in Quantum Dots as a class of nanomaterials has grown considerably since their discovery by Ekimov and Efros in the early 1980s. Although this early work focussed primarily on CdSe-based nanocrystals, the field has now expanded to include various classes of nanoparticles with different types of core, shell or passivation chemistry. Such differences can have a profound effect on the optical properties and potential biocompatibility of the resulting constructs. Although QDs have predominantly been used for imaging and sensing applications, more examples of their use as therapeutics are beginning to emerge. In this chapter we discuss the progress made over the past decade in developing QDs for imaging and therapeutic applications.

Combined sonodynamic and antimetabolite therapy for the improved treatment of pancreatic cancer using oxygen loaded microbubbles as a delivery vehicle.

In this manuscript we describe the preparation of an oxygen-loaded microbubble (O2MB) platform for the targeted treatment of pancreatic cancer using both sonodynamic therapy (SDT) and antimetabolite therapy. O2MB were prepared with either the sensitiser Rose Bengal (O2MB-RB) or the antimetabolite 5-fluorouracil (O2MB-5FU) attached to the microbubble (MB) surface. The MB were characterised with respect to size, physical stability and oxygen retention. A statistically significant reduction in cell viability was observed when three different pancreatic cancer cell lines (BxPc-3, MIA PaCa-2 and PANC-1), cultured in an anaerobic cabinet, were treated with both SDT and antimetabolite therapy compared to either therapy alone. In addition, a statistically significant reduction in tumour growth was also observed when ectopic human xenograft BxPC-3 tumours in SCID mice were treated with the combined therapy compared to treatment with either therapy alone. These results illustrate not only the potential of combined SDT/antimetabolite therapy as a stand alone treatment option in pancreatic cancer, but also the capability of O2-loaded MBs to deliver O2 to the tumour microenvironment in order to enhance the efficacy of therapies that depend on O2 to mediate their therapeutic effect. Furthermore, the use of MBs to facilitate delivery of O2 as well as the sensitiser/antimetabolite, combined with the possibility to activate the sensitiser using externally applied ultrasound, provides a more targeted approach with improved efficacy and reduced side effects when compared with conventional systemic administration of antimetabolite drugs alone.

Modulation of ROS production in photodynamic therapy using a pH controlled photoinduced electron transfer (PET) based sensitiser.

A new sensitiser (4) for use in photodynamic therapy (PDT) has been developed to enable control of ROS production as a function of pH. This pH dependent PDT behaviour was tested in HeLa cells and in SCID mice bearing human xenograft pancreatic cancer (BxPC-3) tumours.

Oxygen carrying microbubbles for enhanced sonodynamic therapy of hypoxic tumours.

Tumour hypoxia represents a major challenge in the effective treatment of solid cancerous tumours using conventional approaches. As oxygen is a key substrate for Photo-/Sono-dynamic Therapy (PDT/SDT), hypoxia is also problematic for the treatment of solid tumours using these techniques. The ability to deliver oxygen to the vicinity of the tumour increases its local partial pressure improving the possibility of ROS generation in PDT/SDT. In this manuscript, we investigate the use of oxygen-loaded, lipid-stabilised microbubbles (MBs), decorated with a Rose Bengal sensitiser, for SDT-based treatment of a pancreatic cancer model (BxPc-3) in vitro and in vivo. We directly compare the effectiveness of the oxygen-loaded MBs with sulphur hexafluoride (SF6)-loaded MBs and reveal a significant improvement in therapeutic efficacy. The combination of oxygen-carrying, ultrasound-responsive MBs, with an ultrasound-responsive therapeutic sensitiser, offers the possibility of delivering and activating the MB-sensitiser conjugate at the tumour site in a non-invasive manner, providing enhanced sonodynamic activation at that site.

Polymeric microbubbles as delivery vehicles for sensitizers in sonodynamic therapy.

Microbubbles (MBs) have recently emerged as promising delivery vehicles for sensitizer drugs in sonodynamic therapy (SDT). The ability to selectively destroy the MB and activate the sensitizer using an external ultrasound trigger could provide a minimally invasive and highly targeted therapy. While lipid MBs have been approved for use as contrast agents in diagnostic ultrasound, the attachment of sensitizer drugs to their surface results in a significant reduction in particle stability. In this Article, we prepare both lipid and polymer (PLGA) MBs with rose bengal attached to their surface and demonstrate that PLGA MB conjugates are significantly more stable than their lipid counterparts. In addition, the improved stability offered by the PLGA shell does not hinder their selective destruction using therapeutically acceptable ultrasound intensities. Furthermore, we demonstrate that treatment of ectopic human tumors (BxPC-3) in mice with the PLGA MB-rose bengal conjugate and ultrasound reduced tumor volume by 34% 4 days after treatment while tumors treated with the conjugate alone increased in volume by 48% over the same time period. Therefore, PLGA MBs may offer a more stable alternative to lipid MBs for the site specific delivery of sensitizers in SDT.