Ultrasound-Mediated Drug Delivery With a Clinical Ultrasound System: In Vitro Evaluation

A synergistic approach for modulating the tumor microenvironment to enhance nano-immunotherapy in sarcomas

The lack of properly perfused blood vessels within tumors can significantly hinder the distribution of drugs, leading to reduced treatment effectiveness and having a negative impact on the quality of life of patients with cancer. This problem is particularly pronounced in desmoplastic cancers, where interactions between cancer cells, stromal cells, and the fibrotic matrix lead to tumor stiffness and the compression of most blood vessels within the tumor. To address this issue, two mechanotherapy approaches-mechanotherapeutics and ultrasound sonopermeation-have been employed separately to treat vascular abnormalities in tumors and have reached clinical trials. Here, we performed in vivo studies in sarcomas, to explore the conditions under which these two mechanotherapy strategies could be optimally combined to enhance perfusion and the efficacy of nano-immunotherapy. Our findings demonstrate that combination of the anti-histamine drug ketotifen, as a mechanotherapeutic, and sonopermeation effectively alleviates mechanical forces by decreasing 50 % collagen and hyaluronan levels and thus, reshaping the tumor microenvironment. Furthermore, the combined therapy normalizes the tumor vasculature by increasing two-fold the pericytes coverage. This combination not only improves six times tumor perfusion but also enhances drug delivery. As a result, blood vessel functionality is enhanced, leading to increased infiltration by 40 % of immune cells (CD4+ and CD8+ T-cells) and improving the antitumor efficacy of Doxil nanomedicine and anti-PD-1 immunotherapy. In conclusion, our research underscores the unique and synergistic potential of combining mechanotherapeutics and sonopermeation. Both approaches are undergoing clinical trials to enhance cancer therapy and have the potential to significantly improve nano-immunotherapy in sarcomas.

RGD-coated polymeric microbubbles promote ultrasound-mediated drug delivery in an inflamed endothelium-pericyte co-culture model of the blood-brain barrier

Drug delivery to central nervous pathologies is compromised by the blood-brain barrier (BBB). A clinically explored strategy to promote drug delivery across the BBB is sonopermeation, which relies on the combined use of ultrasound (US) and microbubbles (MB) to induce temporally and spatially controlled opening of the BBB. We developed an advanced in vitro BBB model to study the impact of sonopermeation on the delivery of the prototypic polymeric drug carrier pHPMA as a larger molecule and the small molecule antiviral drug ribavirin. This was done under standard and under inflammatory conditions, employing both untargeted and RGD peptide-coated MB. The BBB model is based on human cerebral capillary endothelial cells and human placental pericytes, which are co-cultivated in transwell inserts and which present with proper transendothelial electrical resistance (TEER). Sonopermeation induced a significant decrease in TEER values and facilitated the trans-BBB delivery of fluorescently labeled pHPMA (Atto488-pHPMA). To study drug delivery under inflamed endothelial conditions, which are typical for e.g. tumors, neurodegenerative diseases and CNS infections, tumor necrosis factor (TNF) was employed to induce inflammation in the BBB model. RGD-coated MB bound to and permeabilized the inflamed endothelium-pericyte co-culture model, and potently improved Atto488-pHPMA and ribavirin delivery. Taken together, our work combines in vitro BBB bioengineering with MB-mediated drug delivery enhancement, thereby providing a framework for future studies on optimization of US-mediated drug delivery to the brain.

Implantable smart hyperthermia nanofibers for cancer therapy: Challenges and opportunities

Nanofibers (NFs) with practical drug-loading capacities, high stability, and controllable release have caught the attention of investigators due to their potential applications in on-demand drug delivery devices. Developing novel and efficient multidisciplinary management of locoregional cancer treatment through the design of smart NF-based systems integrated with combined chemotherapy and hyperthermia could provide stronger therapeutic advantages. On the other hand, implanting directly at the tumor area is a remarkable benefit of hyperthermia NF-based drug delivery approaches. Hence, implantable smart hyperthermia NFs might be very hopeful for tumor treatment in the future and provide new avenues for developing highly efficient localized drug delivery systems. Indeed, features of the smart NFs lead to the construction of a reversibly flexible nanostructure that enables hyperthermia and facile switchable release of antitumor agents to eradicate cancer cells. Accordingly, this study covers recent updates on applications of implantable smart hyperthermia NFs regarding their current scope and future outlook. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Microbubble-Assisted Ultrasound for Drug Delivery to the Retina in an Ex Vivo Eye Model

Drug delivery to the retina is one of the major challenges in ophthalmology due to the biological barriers that protect it from harmful substances in the body. Despite the advancement in ocular therapeutics, there are many unmet needs for the treatment of retinal diseases. Ultrasound combined with microbubbles (USMB) was proposed as a minimally invasive method for improving delivery of drugs in the retina from the blood circulation. This study aimed to investigate the applicability of USMB for the delivery of model drugs (molecular weight varying from 600 Da to 20 kDa) in the retina of ex vivo porcine eyes. A clinical ultrasound system, in combination with microbubbles approved for clinical ultrasound imaging, was used for the treatment. Intracellular accumulation of model drugs was observed in the cells lining blood vessels in the retina and choroid of eyes treated with USMB but not in eyes that received ultrasound only. Specifically, 25.6 ± 2.9% of cells had intracellular uptake at mechanical index (MI) 0.2 and 34.5 ± 6.0% at MI 0.4. Histological examination of retinal and choroid tissues revealed that at these USMB conditions, no irreversible alterations were induced at the USMB conditions used. These results indicate that USMB can be used as a minimally invasive targeted means to induce intracellular accumulation of drugs for the treatment of retinal diseases.

Ultrasound and Microbubbles Mediated Bleomycin Delivery in Feline Oral Squamous Cell Carcinoma—An In Vivo Veterinary Study

To investigate the feasibility and tolerability of ultrasound and microbubbles (USMB)-enhanced chemotherapy delivery for head and neck cancer, we performed a veterinary trial in feline companion animals with oral squamous cell carcinomas. Six cats were treated with a combination of bleomycin and USMB therapy three times, using the Pulse Wave Doppler mode on a clinical ultrasound system and EMA/FDA approved microbubbles. They were evaluated for adverse events, quality of life, tumour response and survival. Furthermore, tumour perfusion was monitored before and after USMB therapy using contrast-enhanced ultrasound (CEUS). USMB treatments were feasible and well tolerated. Among 5 cats treated with optimized US settings, 3 had stable disease at first, but showed disease progression 5 or 11 weeks after first treatment. One cat had progressive disease one week after the first treatment session, maintaining a stable disease thereafter. Eventually, all cats except one showed progressive disease, but each survived longer than the median overall survival time of 44 days reported in literature. CEUS performed immediately before and after USMB therapy suggested an increase in tumour perfusion based on an increase in median area under the curve (AUC) in 6 out of 12 evaluated treatment sessions. In this small hypothesis-generating study, USMB plus chemotherapy was feasible and well-tolerated in a feline companion animal model and showed potential for enhancing tumour perfusion in order to increase drug delivery. This could be a forward step toward clinical translation of USMB therapy to human patients with a clinical need for locally enhanced treatment.

Plug and Pop: A 3D-Printed, Modular Platform for Drug Delivery Using Clinical Ultrasound and Microbubbles

Targeted drug and gene delivery using ultrasound and microbubbles (USMB) has the potential to treat several diseases. In vitro investigation of USMB-mediated delivery is of prime importance prior to in vivo studies because it is cost-efficient and allows for the rapid optimization of experimental parameters. Most in vitro USMB studies are carried out with non-clinical, research-grade ultrasound systems, which are not approved for clinical use and are difficult to replicate by other labs. A standardized, low-cost, and easy-to-use in vitro experimental setup using a clinical ultrasound system would facilitate the eventual translation of the technology to the bedside. In this paper, we report a modular 3D-printed experimental setup using a clinical ultrasound transducer that can be used to study USMB-mediated drug delivery. We demonstrate its utility for optimizing various cargo delivery parameters in the HEK293 cell line, as well as for the CMT167 lung carcinoma cell line, using dextran as a model drug. We found that the proportion of dextran-positive cells increases with increasing mechanical index and ultrasound treatment time and decreases with increasing pulse interval (PI). We also observed that dextran delivery is most efficient for a narrow range of microbubble concentrations.

Inducible endothelial leakiness in nanotherapeutic applications

All intravenous delivered nanomedicine needs to escape from the blood vessel to exert their therapeutic efficacy at their designated site of action. Failure to do so increases the possibility of detrimental side effects and negates their therapeutic intent. Many powerful anticancer nanomedicine strategies rely solely on the tumor derived enhanced permeability and retention (EPR) effect for the only mode of escaping from the tumor vasculature. However, not all tumors have the EPR effect nor can the EPR effect be induced or controlled for its location and timeliness. In recent years, there have been exciting developments along the lines of inducing endothelial leakiness at the tumor to decrease the dependence of EPR. Physical disruption of the endothelial-endothelial cell junctions with coordinated biological intrinsic pathways have been proposed that includes various modalities like ultrasound, radiotherapy, heat and even nanoparticles, appear to show good progress towards the goal of inducing endothelial leakiness. This review explains the intricate and complex biological background behind the endothelial cells with linkages on how updated reported nanomedicine strategies managed to induce endothelial leakiness. This review will also end off with fresh insights on where the future of inducible endothelial leakiness holds.

Delivery of anti-cancer drugs using microbubble-assisted ultrasound in digestive oncology: From preclinical to clinical studies

INTRODUCTION

The combination of microbubbles (MBs) and ultrasound (US) is an emerging method for the noninvasive and targeted enhancement of intratumor chemotherapeutic uptake. This method showed an increased local drug extravasation in tumor tissue while reducing the systemic adverse effects in various tumor models.

AREA COVERED

We focused on preclinical and clinical studies investigating the therapeutic efficacy and safety of this technology for the treatment of colorectal, pancreatic and liver cancers. We discussed the limitations of the current investigations and future perspectives.

EXPERT OPINION

The therapeutic efficacy and the safety of delivery of standard chemotherapy regimen using MB-assisted US have been mainly demonstrated in subcutaneous models of digestive cancers. Although some clinical trials on pancreatic ductal carcinoma and hepatic metastases from various digestive cancers have shown promising results, successful evaluation of this method in terms of US settings, chemotherapeutic schemes and MBs-related parameters will need to be addressed in more relevant preclinical models of digestive cancers, in small and large animals before fully and successfully translating this technology for clinic use. Ultimately, a clear evidence of the correlation between the enhanced intratumoral concentrations of therapeutics and the increased therapeutic response of tumors have to be provided in clinical trials.

Safety Assessment of Ultrasound-Assisted Intravesical Chemotherapy in Normal Dogs: A Pilot Study

Intravesical chemotherapy after transurethral resection is a treatment option in patients with non-muscle invasive bladder cancer. The efficacy of intravesical chemotherapy is determined by the cellular uptake of intravesical drugs. Therefore, drug delivery technologies in the urinary bladder are promising tools for enhancing the efficacy of intravesical chemotherapy. Ultrasound-triggered microbubble cavitation may enhance the permeability of the urothelium, and thus may have potential as a drug delivery technology in the urinary bladder. Meanwhile, the enhanced permeability may increase systemic absorption of intravesical drugs, which may increase the adverse effects of the drug. The aim of this preliminary safety study was to assess the systemic absorption of an intravesical drug that was delivered by ultrasound-triggered microbubble cavitation in the urinary bladder of normal dogs. Pirarubicin, a derivative of doxorubicin, and an ultrasound contrast agent (Sonazoid) microbubbles were administered in the urinary bladder. Ultrasound (transmitting frequency 5 MHz; pulse duration 0.44 μsec; pulse repetition frequency 7.7 kHz; peak negative pressure −1.2 MPa) was exposed to the bladder using a diagnostic ultrasound probe (PLT-704SBT). The combination of ultrasound and microbubbles did not increase the plasma concentration of intravesical pirarubicin. In addition, hematoxylin and eosin staining showed that the combination of ultrasound and microbubble did not cause observable damages to the urothelium. Tissue pirarubicin concentration in the sonicated region was higher than that of the non-sonicated region in two of three dogs. The results of this pilot study demonstrate the safety of the combination of intravesical pirarubicin and ultrasound-triggered microbubble cavitation, that is, ultrasound-assisted intravesical chemotherapy.

The Effect of Microbubble-Assisted Ultrasound on Molecular Permeability across Cell Barriers

The combination of ultrasound and microbubbles (USMB) has been applied to enhance drug permeability across tissue barriers. Most studies focused on only one physicochemical aspect (i.e., molecular weight of the delivered molecule). Using an in vitro epithelial (MDCK II) cell barrier, we examined the effects of USMB on the permeability of five molecules varying in molecular weight (182 Da to 20 kDa) and hydrophilicity (LogD at pH 7.4 from 1.5 to highly hydrophilic). Treatment of cells with USMB at increasing ultrasound pressures did not have a significant effect on the permeability of small molecules (molecular weight 259 to 376 Da), despite their differences in hydrophilicity (LogD at pH 7.4 from −3.2 to 1.5). The largest molecules (molecular weight 4 and 20 kDa) showed the highest increase in the epithelial permeability (3-7-fold). Simultaneously, USMB enhanced intracellular accumulation of the same molecules. In the case of the clinically relevant anti- C-X-C Chemokine Receptor Type 4 (CXCR4) nanobody (molecular weight 15 kDa), USMB enhanced paracellular permeability by two-fold and increased binding to retinoblastoma cells by five-fold. Consequently, USMB is a potential tool to improve the efficacy and safety of the delivery of drugs to organs protected by tissue barriers, such as the eye and the brain.

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.