In vitro potentiation of doxorubicin by unseeded controlled non-inertial ultrasound cavitation

Engineering of Erythrocytes as Drug Carriers for Therapeutic Applications

Erythrocytes, also known as red blood cells (RBCs), have garnered considerable attention as potential carriers for drug delivery, owing to their inherent properties such as biocompatibility, biodegradability, and prolonged circulation half-life. This paper presents a comprehensive overview of the role of erythrocytes in drug delivery, elucidating recent advancements in delivering a diverse array of therapeutic agents, including small molecules, nucleic acids, antibodies, protein enzymes, and nanoparticles. Two primary strategies for encapsulating drugs within erythrocytes are systematically discussed: internal loading and surface loading. Each strategy offers distinct advantages in terms of drug stability and release kinetics. Notably, the utilization of erythrocyte membrane camouflaged nanocarriers holds promise for enhancing the biocompatibility of conventional nanoparticles and facilitating targeted drug delivery. Furthermore, the broad spectrum of biomedical applications of erythrocyte-based drug delivery systems are examined, ranging from cancer treatment to diabetes management, thrombosis prevention, and immunotherapy. This review provides a comprehensive evaluation of current technologies in erythrocyte-loaded drug delivery, highlighting the strengths, weaknesses, and future directions for advancing therapeutic interventions in various disease contexts.

Enhanced Stable Cavitation and Nonlinear Acoustic Properties of Poly(butyl cyanoacrylate) Polymeric Microbubbles after Bioconjugation

Microbubbles (MB) are used as ultrasound (US) contrast agents in clinical settings because of their ability to oscillate upon exposure to acoustic pulses and generate nonlinear responses with a stable cavitation profile. Polymeric MB have recently attracted increasing attention as molecular imaging probes and drug delivery agents based on their tailorable acoustic responses, high drug loading capacity, and surface functionalization capabilities. While many of these applications require MB to be functionalized with biological ligands, the impact of bioconjugation on polymeric MB cavitation and acoustic properties remains poorly understood. Hence, we here evaluated the effects of MB shell hydrolysis and subsequent streptavidin conjugation on the acoustic behavior of poly(butyl cyanoacrylate) (PBCA) MB. We show that upon biofunctionalization, MB display higher acoustic stability, stronger stable cavitation, and enhanced second harmonic generation. Furthermore, functionalized MB preserve the binding capabilities of streptavidin conjugated on their surface. These findings provide insights into the effects of bioconjugation chemistry on polymeric MB acoustic properties, and they contribute to improving the performance of polymer-based US imaging and theranostic agents.

Ultrasound-excited temozolomide sonosensitization induces necroptosis in glioblastoma

Temozolomide (TMZ) has been determined to be the chemotherapeutic drug with efficacy for glioblastoma (GBM). Thus, potentiating the therapeutic effect of TMZ can undoubtedly yield twice the result with half the effort. In this study, we found for the first time that TMZ can produce reactive oxygen species (ROS) under the influence of ultrasound (US). This property allows TMZ-US therapy to have better efficacy in the treatment of GBM. Given that the increasing use of US in central nervous system (CNS) diseases and the importance of TMZ for GBM therapy, our results will facilitate the development of TMZ-associated glioblastoma therapies. Moreover, we found that chemotherapeutic drugs might have the ability to generate ROS under the excitation of US. On a larger scale, our findings may be applicable to a wide range of known drugs.

Ultrasound boosts doxorubicin efficacy against sensitive and resistant ovarian cancer cells

Ovarian cancer (OC) is characterised by the highest mortality of all gynaecological malignancies, frequent relapses, and the development of resistance to drug therapy. Sonodynamic therapy (SDT) is an innovative anticancer approach that combines a chemical/drug (sonosensitizer) with low-intensity ultrasound (US), which are both harmless per sé, with the sonosensitizer being acoustically activated, thus yielding localized cytotoxicity often via reactive oxygen species (ROS) generation. Doxorubicin (Doxo) is a potent chemotherapeutic drug that has also been recommended as a first-line treatment against OC. This research work aims to investigate whether Doxo can be used at very low concentrations, in order to avoid its significant side effects, as a sonosensitiser under US exposure to promote cancer cell death in Doxo non-resistant (A2780/WT) and Doxo resistant (A2780/ADR) human OC cell lines. Moreover, since recurrence is an important issue in OC, we have also investigated whether the proposed SDT with Doxo induces immunogenic cell death (ICD) and thus hinders OC recurrence. Our results show that the sonodynamic anticancer approach with Doxo is effective in both A2780/WT and A2780/ADR cell lines, and that it proceeds via a ROS-dependent mechanism of action and immune sensitization that is based on the activation of the ICD pathway.

Pancreatic Ductal Adenocarcinoma: Current and Emerging Therapeutic Uses of Focused Ultrasound

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is an increasingly prevalent form of cancer with a low patient survival rate following diagnosis. Focused Ultrasound is an emerging modality that provides exciting opportunities in treating PDAC. This review provides an overview of the clinical application and scientific research of therapeutic focused ultrasound for the treatment of PDAC for use by clinicians and scientific researchers. In addition to providing a description of various physical mechanism underlying therapeutic applications, the current benefits, challenges, and possible future avenues for the application and development of focused ultrasound in the treatment of PDAC are summarized.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) diagnosis accompanies a somber prognosis for the patient, with dismal survival odds: 5% at 5 years. Despite extensive research, PDAC is expected to become the second leading cause of mortality by cancer by 2030. Ultrasound (US) has been used successfully in treating other types of cancer and evidence is flourishing that it could benefit PDAC patients. High-intensity focused US (HIFU) is currently used for pain management in palliative care. In addition, clinical work is being performed to use US to downstage borderline resectable tumors and increase the proportion of patients eligible for surgical ablation. Focused US (FUS) can also induce mechanical effects, which may elicit an anti-tumor response through disruption of the stroma and can be used for targeted drug delivery. More recently, sonodynamic therapy (akin to photodynamic therapy) and immunomodulation have brought new perspectives in treating PDAC. The aim of this review is to summarize the current state of those techniques and share our opinion on their future and challenges.

Proof of Concept: Protein Delivery into Human Erythrocytes Using Stable Cavitation

Human erythrocytes represent candidates of choice as carriers for a wide range of drugs due to their unique biophysical and physiological properties. In this study, we used a sonoporation device generating and monitoring acoustic stable cavitation without any addition of contrast or nucleation agents. The device was evaluated for bovine serum albumin (BSA) delivery into human erythrocytes. After determining the adequate hematocrit percentage compatible with the generation of stable cavitation, we determined the optimal sonoporation conditions allowing BSA delivery while preserving erythrocyte integrity. Our results demonstrate that stable cavitation allows efficient delivery of proteins into human erythrocytes with limited lysis of these cells. In conclusion, our study allowed for the development of a stable and regulated cavitation program and the establishment of sonoporation conditions suitable for intracellular protein delivery while maintaining erythrocyte integrity. Additional investigations are needed to move from the proof of concept to a larger-scale application.

Effect of Therapeutic Ultrasound on the Release of Insulin, Glucagon, and Alpha-Amylase from Ex Vivo Pancreatic Models

OBJECTIVES

Our previously published studies showed the potential of therapeutic ultrasound (US) as a novel non-pharmacological alternative for the treatment of secretory deficiencies in type 2 diabetes. Despite showing enhanced insulin release from beta cells, these studies did not explore the potential effects of US treatment on other cells in the islets of Langerhans such as glucagon-secreting alpha cells or acinar cells of the exocrine pancreas.

METHODS

We applied US parameters found capable of safely stimulating insulin secretion from pancreatic beta cells (f = 800 kHz, ISPTA  = 0.5-1 W/cm2 , 5 minutes) to a diced rabbit pancreas model in culture plates (n = 6 per group). Released quantities of insulin and glucagon in response to US treatment were measured by collecting aliquots of the extracellular medium prior to the start of the treatment (t = 0 minute), immediately after treatment (t = 5 minutes) and 30 minutes after the end of treatment (t = 35 minutes). Potential release of digestive enzyme alpha-amylase as a result of US treatment was evaluated in rabbit pancreas experiments. Preliminary studies were also performed in a small number of human pancreatic islets in culture plates (n = 3 per group). The general integrity of the US-treated rabbit pancreatic tissue and human pancreatic islets was evaluated through histological analysis.

RESULTS

While sham-treated rabbit pancreas samples showed decreased extracellular insulin content, there was an increase in insulin release at t = 5 minutes from samples treated with US at 800 kHz and 1 W/cm2 (P <.005). Furthermore, no further insulin release was detected at t = 35 minutes. No statistically significant difference in extracellular glucagon and alpha-amylase concentrations was observed between US-treated and sham rabbit pancreas groups. Preliminary studies in human islets appeared to follow trends observed in rabbit pancreas studies. Islet and other pancreatic tissue integrity did not appear to be affected by the US treatment.

CONCLUSION

A potential US-based strategy for enhanced insulin release would require optimization of insulin secretion from pancreatic beta cells while minimizing glucagon and pancreatic enzyme secretions.

Ultrasound Molecular Imaging for the Guidance of Ultrasound-Triggered Release of Liposomal Doxorubicin and Its Treatment Monitoring in an Orthotopic Prostatic Tumor Model in Rat

Liposome encapsulation of drugs is an interesting approach in cancer therapy to specifically release the encapsulated drug at the desired treatment site. In addition to thermo-, pH-, light-, enzyme- or redox-responsive liposomes, which have had promising results in (pre-) clinical studies, ultrasound-triggered sonosensitive liposomes represent an exciting alternative to locally trigger the release from these cargos. Localized drug release requires precise tumor visualization to produce a targeted and ultrasound stimulus. We used ultrasound molecular imaging (USMI) with BR55, a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasound contrast agent, to guide ultrasound-triggered release of sonosensitive liposomes encapsulating doxorubicin (L-DXR) in an orthotopic prostatic rodent tumor model. Forty-eight hours after L-DXR injection, local release of doxorubicin was triggered with a confocal ultrasound device with two focused transducers, 1.1-MHz center frequency, and peak positive and negative pressures of 20.5 and 13 MPa at focus. Tumor size decreased by 20% in 2 wk with L-DXR alone (n = 9) and by 70% after treatment with L-DXR and confocal ultrasound (n = 7) (p < 0.01). The effect of doxorubicin on perfusion/vascularity and VEGFR2 expression was evaluated by USMI and immunohistochemistry of CD31 and VEGFR2 and did not reveal differences in perfusion or VEGFR2 expression in the absence or after the triggered release of liposomes. USMI can provide precise guidance for ultrasound-triggered release of liposomal doxorubicin mediated by a confocal ultrasound device; moreover, the combination of B-mode imaging and USMI can help to follow the response of the tumor to the therapy.

Neurostimulation success rate of repetitive-pulse focused ultrasound in an in vivo giant axon model: An acoustic parametric study

PURPOSE

Focused ultrasound (FUS) is a promising tool to develop new modalities of therapeutic neurostimulation. The ability of FUS to stimulate the nervous system, in a noninvasive and spatiotemporally precise manner, has been demonstrated in animals and human subjects, but the underlying biomechanisms are not fully understood yet. The objective of the present study was to investigate the bioeffects involved in the generation of trains of action potentials (APs) by repetitive-pulse FUS stimuli in a simple invertebrate neural model.

METHODS

The respective influences of different acoustic parameters on the neurostimulation success rate (NSR), defined as the rate of FUS stimuli capable of evoking at least one AP, were explored using the system of afferent nerves and giant fibers of Lumbricus terrestris as neural model. Each parameter was studied independently by administering random FUS sequences while keeping all but one FUS parameter constant. The NSR was evaluated as a function of (i) the spatial-average pulse-average intensity (I_sapa ); (ii) the pulse duration (PD); (iii) the pulse repetition frequency (PRF); iv) the number of cycles per pulse (N_cycles ); (v) two ultrasound frequencies, f₀  = 1.1 MHz and f₃  = 3.3 MHz, corresponding to the fundamental and third-harmonic resonant frequencies of the FUS transducer, respectively (spherical, radius of curvature: 50 mm); and (vi) levels of emerging stable cavitation and inertial cavitation.

RESULTS

The NSR associated to 1.1 MHz repetitive-pulse FUS stimuli was found to increase as a function of increasing I_sapa , PD, PRF, and N_cycles . When evaluating each parameter at f = 1.1 MHz, it was observed that NSRs close to 100% were achieved when sufficiently elevating their respective values. When computing the NSR as a function of the spatial-average, temporal-average intensity (I_sata ), defined as the product of PRF, PD, and I_sapa , a significant elevation of the NSR from 0% to close to 100% was measured by increasing I_sata from values approximate to 4 W/cm² to values higher than 12 W/cm² . No clear and consistent trend was observed in trials aimed at exploring the effects of different levels of stable and inertial acoustic cavitation on the NSR. Finally, the feasibility of inducing neural responses with 3.3 MHz repetitive-pulse FUS stimuli was also demonstrated with NSRs reaching up to 60%, in the range of FUS parameters studied.

CONCLUSION

The time-averaged value of the radiation force per unit volume of tissue is proportional to the acoustic intensity. As a result, the observations from this study suggest that the neural structure responding to the stimulus is sensitive to the mean radiation force carried by the FUS sequence, regardless of the combination of FUS parameters giving rise to such force. The results from this study further revealed the existence of a minimal activation threshold with regard to I_sapa .

DNA Double-Strand Breaks in Murine Mammary Tumor Cells Induced by Combined Treatment with Doxorubicin and Controlled Stable Cavitation

Chemotherapeutic agents such as doxorubicin induce cell cytotoxicity through induction of DNA double-strand breaks. Recent studies have reported the occurrence of DNA double-strand breaks in different cell lines exposed to cavitational ultrasound. As ultrasound stable cavitation can potentiate the therapeutic effects of cytotoxic drugs, we hypothesized that combined treatment with unseeded stable cavitation and doxorubicin would lead to increased DNA damage and would reduce cell viability and proliferation in vitro. In this study, we describe how we determined, using 4T1 murine mammary carcinoma as a model cell line, that unseeded stable cavitation combined with doxorubicin leads to additive DNA double-strand break induction. Combined treatment with doxorubicin and unseeded stable cavitation significantly reduced cell viability and proliferation at 72 h. A mechanistic study of the potential mechanisms of action of the combined treatment identified the presence of cavitation necessary to increase early DNA double-strand break induction, likely mediated by a bystander effect with release of extracellular calcium.