Perfusion-guided sonopermeation of neuroblastoma: a novel strategy for monitoring and predicting liposomal doxorubicin uptake

Neuroblastoma (NB) is the most common extracranial solid tumor in infants and children, and imposes significant morbidity and mortality in this population. The aggressive chemoradiotherapy required to treat high-risk NB results in survival of less than 50%, yet is associated with significant long-term adverse effects in survivors. Boosting efficacy and reducing morbidity are therefore key goals of treatment for affected children. We hypothesize that these may be achieved by developing strategies that both focus and limit toxic therapies to the region of the tumor. One such strategy is the use of targeted image-guided drug delivery (IGDD), which is growing in popularity in personalized therapy to simultaneously improve on-target drug deposition and assess drug pharmacodynamics in individual patients. IGDD strategies can utilize a variety of imaging modalities and methods of actively targeting pharmaceutical drugs, however in vivo imaging in combination with focused ultrasound is one of the most promising approaches already being deployed for clinical applications. Over the last two decades, IGDD using focused ultrasound with microbubble ultrasound contrast agents (UCAs) has been increasingly explored as a method of targeting a wide variety of diseases, including cancer. This technique, known as sonopermeation, mechanically augments vascular permeability, enabling increased penetration of drugs into target tissue. However, to date, methods of monitoring the vascular bioeffects of sonopermeation in vivo are lacking. UCAs are excellent vascular probes in contrast-enhanced ultrasound (CEUS) imaging, and are thus uniquely suited for monitoring the effects of sonopermeation in tumors. Methods: To monitor the therapeutic efficacy of sonopermeation in vivo, we developed a novel system using 2D and 3D quantitative contrast-enhanced ultrasound imaging (qCEUS). 3D tumor volume and contrast enhancement was used to evaluate changes in blood volume during sonopermeation. 2D qCEUS-derived time-intensity curves (TICs) were used to assess reperfusion rates following sonopermeation therapy. Intratumoral doxorubicin (and liposome) uptake in NB was evalauted ex vivo along with associated vascular changes. Results: In this study, we demonstrate that combining focused ultrasound therapy with UCAs can significantly enhance chemotherapeutic payload to NB in an orthotopic xenograft model, by improving delivery and tumoral uptake of long-circulating liposomal doxorubicin (L-DOX) nanoparticles. qCEUS imaging suggests that changes in flow rates are highly sensitive to sonopermeation and could be used to monitor the efficacy of treatment in vivo. Additionally, initial tumor perfusion may be a good predictor of drug uptake during sonopermeation. Following sonopermeation treatment, vascular biomarkers show increased permeability due to reduced pericyte coverage and rapid onset of doxorubicin-induced apoptosis of NB cells but without damage to blood vessels. Conclusion: Our results suggest that significant L-DOX uptake can occur by increasing tumor vascular permeability with microbubble sonopermeation without otherwise damaging the vasculature, as confirmed by in vivo qCEUS imaging and ex vivo analysis. The use of qCEUS imaging to monitor sonopermeation efficiency and predict drug uptake could potentially provide real-time feedback to clinicians for determining treatment efficacy in tumors, leading to better and more efficient personalized therapies. Finally, we demonstrate how the IGDD strategy outlined in this study could be implemented in human patients using a single case study

The effect of injected dose on localized tumor accumulation and cardiac uptake of doxorubicin in a Vx2 rabbit tumor model using MR-HIFU mild hyperthermia and thermosensitive liposomes

Purpose When doxorubicin (DOX) is administered via lyso-thermosensitive liposomes (LTLD), mild hyperthermia enhances localized delivery to heated vs. unheated tumors. The optimal LTLD dose and the impact of different doses on systemic drug distribution are unknown. Materials and methods: In this study, we evaluated local and systemic DOX delivery with three LTLD doses (0.1, 0.5, and 2.5 mg/kg) in a Vx2 rabbit tumor model. Temporally and spatially accurate controlled hyperthermia was achieved using a clinical MR-HIFU system for the intended heating duration (40 min). Results: DOX concentration in tissues delivered from LTLD combined with MR-HIFU mild hyperthermia are dose-dependent, including heated/unheated tumor, heart, and other healthy organs. Higher DOX accumulation and tumor-to-heart drug concentration ratio, defined as the ratio of DOX delivered into the tumor vs the heart, were observed in heated tumors compared to unheated tumors in all three tested doses. The DOX uptake efficiency for each mg/kg of LTLD injected IV of heated tumor was significantly higher than that of unheated tumor and heart within the tested dose range (0.1-2.5 mg/kg). The DOX uptake for the heart linearly scaled up as a function of dose while that for the heated tumor showed some evidence of saturation at the high dose of 2.5 mg/kg. Conclusions: These results provide guidance on clinical protocol design of hyperthermia-triggered drug delivery

Intermittent alternating magnetic fields diminish metal-associated biofilm in vivo

Abstract Prosthetic joint infection (PJI) is a complication of arthroplasty that results in significant morbidity. The presence of biofilm makes treatment difficult, and removal of the prosthesis is frequently required. We have developed a non-invasive approach for biofilm eradication from metal implants using intermittent alternating magnetic fields (iAMF) to generate targeted heating at the implant surface. The goal of this study was to determine whether iAMF demonstrated efficacy in an in vivo implant biofilm infection model. iAMF combined with antibiotics led to enhanced reduction of biofilm on metallic implants in vivo compared to antibiotics or untreated control. iAMF-antibiotic combinations resulted in a > 1 − log further reduction in biofilm burden compared to antibiotics or iAMF alone. This combination effect was seen in both S. aureus and P. aeruginosa and seen with multiple antibiotics used to treat infections with these pathogens. In addition, efficacy was temperature dependent with increasing temperatures resulting in a greater reduction of biofilm. Tissue damage was limited (< 1 mm from implant-tissue interface). This non-invasive approach to eradicating biofilm could serve as a new paradigm in treating PJI

Persistent symptoms and conditions among children and adolescents hospitalised with COVID-19 illness: a qualitative study

Objectives There is limited in-depth research exploring persistent symptoms and conditions among children and adolescents who contracted COVID-19 illness that required hospitalisation. The main objective of this study was to conduct qualitative interviews among families who had a child hospitalised with COVID-19 illness to elucidate their child’s physical, mental and social health outcomes months after initial acute infection.Design, setting and participants A qualitative study that composed of in-depth interviews among families with a child hospitalised with COVID-19 illness in one large urban US paediatric healthcare system. Parents (N=25) were recruited from an ongoing quantitative study to estimate the prevalence of long COVID in children hospitalised with COVID-19 illness. During in-depth interviews, parents were invited to describe their child’s post-COVID-19 symptoms and experiences. Interviews were audiotaped, transcribed and coded in NVivo.Results Seven themes were identified concerning the child’s prolonged COVID-19 experiences: (1) post-traumatic stress disorder, (2) social anxiety, (3) severe symptoms on reinfection, (4) worsened pre-existing conditions, (5) lack of insurance coverage for costly treatments, (6) access and utilisation of support systems and (7) overall resilience and recovery. Four parent-specific themes were identified: (1) fear of COVID-19 unknowns, (2) mixed messaging from health information sources, (3) schools being both a support system and a hindrance and (4) desire for and access to support systems.Conclusions A subset of children who were hospitalised with COVID-19 illness are experiencing a range of serious mental health impacts related to persistent COVID-19 symptoms. Clinical and public health support strategies should be developed to support these children and their families as they reintegrate in school, social and community activities

Remote acoustic sensing as a safety mechanism during exposure of metal implants to alternating magnetic fields

<div><p>Treatment of prosthetic joint infections often involves multiple surgeries and prolonged antibiotic administration, resulting in a significant burden to patients and the healthcare system. We are exploring a non-invasive method to eradicate biofilm on metal implants utilizing high-frequency alternating magnetic fields (AMF) which can achieve surface induction heating. Although proof-of-concept studies demonstrate the ability of AMF to eradicate biofilm in vitro, there is a legitimate safety concern related to the potential for thermal damage to surrounding tissues when considering heating implanted metal objects. The goal of this study was to explore the feasibility of detecting acoustic emissions associated with boiling at the interface between a metal implant and surrounding soft tissue as a wireless safety sensing mechanism. Acoustic emissions generated during in vitro and in vivo AMF exposures were captured with a hydrophone, and the relationship with surface temperature analyzed. The effect of AMF exposure power, surrounding media composition, implant location within the AMF transmitter, and implant geometry on acoustic detection during AMF therapy was also evaluated. Acoustic emissions were reliably identified in both tissue-mimicking phantom and mouse studies, and their onset coincided with the implant temperature reaching the boiling threshold. The viscosity of the surrounding medium did not impact the production of acoustic emissions; however, emissions were not present when the medium was oil due to the higher boiling point. Results of simulations and in vivo studies suggest that short-duration, high-power AMF exposures combined with acoustic sensing can be used to minimize the amount of thermal damage in surrounding tissues. These studies support the hypothesis that detection of boiling associated acoustic emissions at a metal/tissue interface could serve as a real-time, wireless safety indicator during AMF treatment of biofilm on metallic implants.</p></div

Comparison between H&E- and Masson’s trichrome-stained sections showing tissue thermal damage.

<p>A mouse 7 days after an 800 W AMF exposure lasting 4 seconds exhibits a circumferential pattern of damage in both (a) H&E staining and (b) Masson’s trichrome staining. In H&E-stained section (a), robust regenerative activity is seen at the edge of the thermal damage boundary (purple area). To representatively show the details, a high-magnification image of the area indicated by a blue-dashed box in was obtained and showed as the inset with the scale bar of 200 μm. In Masson’s trichrome-stained section (b), the blue area indicates necrotic muscle fibers, matching that seen in H&E-stained sections. (c,d) A mouse 7 days after a 4300 W AMF exposure shows similar findings. In all cases, the transition from damaged to normal muscle is abrupt and is best visualized on Masson’s trichrome stain. Scale bars represent 1 mm.</p

AMF exposures produce highly localized tissue damage in vivo.

<p>H&E-stained sections through the thighs of mice receiving AMF exposures. The cavity (CAV) represents the location of a surgically implanted 4.8 mm stainless steel ball. A sham-treated mouse (a) 7 days after surgical implantation shows a residual inflammatory response at the edge of the cavity. A mouse receiving a 190 W AMF exposure for 220 s (b) exhibits a rim of thermal damage surrounding the implant and extending approximately 3 mm from the cavity. The boundary between the damaged area and normal tissue is marked by a yellow-dashed line. A similar pattern of damage is seen for a mouse exposed to 800 W for 15 seconds (c), however the radial extent is only approximately 1.3 mm. A mouse after a 4300 W AMF exposure for 1.5 s (d) exhibits a circumferential pattern of damage extending to approximately 0.6 mm from the cavity rim. In all cases, the transition from damaged to normal muscle (dashed line in top panels) is abrupt. Scale bars represent 1 mm. To representatively show the details in the transition zone, a high-magnification image of the area indicated by a blue-dashed box in (c) was obtained and showed as the inset with the scale bar of 200 μm. (e-f) Numerical simulations of the mouse AMF exposures shows the relationship between AMF power, duration and thermal damage. The distance to the 240 CEM43 boundary (extent of irreversible thermal damage), the 80 CEM43 boundary (extent of reversible damage), and 16 CEM43 boundary (extent of initial bone damage) from the surface of the implanted metal ball are shown as a function of the time required to reach a surface temperature of 100°C on the ball. The construct of the 2D axisymmetric model is shown in e), while the trend for the damage contours is shown in f). The graph shows the rapidly reduced thermal damage distance as the time to boiling is decreased due to the increasing AMF power, indicating the enhanced safety of high power short AMF exposures. In addition, the distance between the black and red curves decreases as the time to boiling decreases, indicating a sharper thermal gradient in tissue for these exposures.</p

Time to boiling decreases with increasing AMF power in both tissue-mimicking phantom and in vivo.

<p>The red curve (squares) depicts the result for a ball embedded in a tissue-mimicking phantom, while the blue curve (triangles) depicts the result for the same ball embedded in the thigh muscle of mice. The relationship between time to boiling and power was similar for both experimental groups. Statistics: mean ± std (n = 4).</p

Boiling detection of a human-sized knee phantom.

<p>(a) A human-scale AMF system set up, including a human-sized knee implant, a customized coil which fits the knee size, and a hydrophone on top. (b) Sound signal during AMF-induction heating. The red dashed line indicates boiling signal detection threshold (0.001). The figure demonstrates that efficient heating on the human knee implant was achieved with the customized AMF system, and acoustic emissions related to boiling were successfully detected. Power: 4300 W.</p