Ultrasound for the delivery of a nanocarrier across biological barriers in tumors: impact of cavitation and acoustic radiation force

Ultrasound for the delivery of a nanocarrier across biological barriers in tumors: impact of cavitation and acoustic radiation force Although conventional chemotherapy is the still one of the most important treatment modalities, it is often insufficient resulting in limited efficacy and systemic off-target effects. Ultrasound (US) alone and in combination with microbubbles (MBs) have been shown to produce a variety ofbiological effects on tissue that can result in transiently enhanced permeability of biological barriers such as blood vessel walls, the extracellular matrix (ECM), cell membranes, and the blood-brain barrier, leading to enhanced accumulation of co-injected drug molecules at the target site. However, a full understanding of how US alone and combined with injected MBs improves thee therapeutic effect of drugs against tumors is lacking. In this thesis, a nano-carrier delivery study assessing the performance of the combination of US with nanoparticles (NPs), and NPs-stabilized MBs or commercial contrast agents (SonoVue) in overcoming the biological barriers, including blood vessel walls and the ECM to the extravasation and transport of NPs as a model therapeutic agents is conducted. US combined with injected MBs induced cavitation in the vasculature were observed in real time using optical microscope and found significant extravasation and penetration of the NPs under the range of pressures applied. Majority of the extravasation took place at vessel branching points, and a higher pressure is required to achieve extravasation from the smaller blood vessels than from larger vessels. US alters nanoparticle flow velocity and blood flow direction. In addition, we investigated the impact of US and MBs on the ECM and found insignificant changes in the collagen content and structure for the acoustic pressures applied. In addition, we found that the mechanical effect of US through acoustic radiation force (ARF) and acoustic streaming improved the transport of NPs in the tumor ECM. This penetration of the NPs might facilitate enhanced therapeutic efficacy against tumor sites. However, we found no effect of ARF on the transport of NPs in the tissue-mimicking collagen phantom, whereas a large deformation of the collagen gel was found for the acoustic pressures tested. ARF could play an important role in overcoming the barriers created by vasculature and ECM if the US parameters are well optimized. Using several experimental investigations, important insights were gained concerning the mechanisms involved in the non-thermal effect of US (cavitation and ARF) on enhancing drug delivery. Interestingly, the results are highly useful for understanding the mechanisms, optimizing the US-mediated delivery of NPs and supplying important insights for future studies. It is also noted that the US-induced drug delivery of nano-carriers across biological barriers can enhanced cancer treatment

Ultrasound radiation force transport of drugs in tumors

Delivery of chemotherapeutic agents administered intravenously tosolid tumors tissue in optimal quantities is one of the challenges in theclinic. However, ultrasound improves the delivery of the chemothera-peutic agents various ways depending on the frequency and the acous-tic intensity applied though thermal and/or mechanical interactionswith the biological tissues. The mechanical interaction arises due tothe ultrasound parameters through acoustic radiation force or cavita-tion. The purpose of this study was hence to investigate the potentialof ultrasound radiation force for the enhancement of drug uptake inprostate tumors in vivo using poly(butylcyanoacrylate)(PBCA) nanoparticles and doxorubicin(Dox) .In this work, the performance of the transducer (3D probe: LA8.0/128/4D -1169) used of this experiment was studied. The safetyissues for both the transducer and the patient that can occur due tothe mechanical and thermal damage which are the main critical limitswere discussed. In addition, a high power acoustic waves that are pre-cisely localized and precisely controlled in amplitude was the secondlimit which was required, hence studied. The optimal drive voltageand duty cycle for probe was therefore found to be 18V and 1.25%respectively at 8MHz transmitted frequency and 1.25 sec long pulsewith reputation frequency of (PRF) 10KHz.In addition, form the maximum possible settings of the transducer,the ultrasound radiation force (URF), ultrasound thermal heating ofthe tissue (UTH), and temperature on the tissue were simulated, andfound 9800N/m3, 49 X 10^-6 J/m and 4 X 10^-6 oK respectively. Lastly, based onthese findings, in vivo animal experiment on mice, in which a prostatecancer cells model implemented, was performed, and the distributionof the administered doxorubicin (Dox) and poly(butylcyanoacrylate)(PBCA) nanoparticles on the target tissue was tested. Hence, al-though it is a little dificult to give a concrete conclusion on the impact of URF on the distribution and penetration of the Dox and thePBCA nano particle with out analyzing in a quantified way, the con-focal laser scanning microscopy reveled no legible significant differencewas observed for the distribution of the two drugs when we comparedwithout and with ultrasound exposures

Effect of ultrasound on the vasculature and extravasation of nanoscale particles imaged in real time

Ultrasound and microbubbles have been found to improve the delivery of drugs and nanoparticles to tumor tissue. To obtain new knowledge on the influence of vascular parameters on extravasation and to elucidate the effect of acoustic pressure on extravasation and penetration of nanoscale particles into the extracellular matrix, real-time intravital multiphoton microscopy was performed during sonication of tumors growing in dorsal window chambers. The impact of vessel diameter, vessel structure and blood flow was characterized. Fluorescein isothiocyanate–dextran (2 MDa) was injected to visualize blood vessels. Mechanical indexes (MI) of 0.2–0.8 and in-house-made, nanoparticle-stabilized microbubbles or Sonovue were applied. The rate and extent of penetration into the extracellular matrix increased with increasing MI. However, to achieve extravasation, smaller vessels required MIs (0.8) higher than those of blood vessels with larger diameters. Ultrasound changed the blood flow rate and direction. Interestingly, the majority of extravasations occurred at vessel branching points.publishedVersio

Effect of acoustic radiation force on displacement of nanoparticles in collagen gels

Penetration of nanoscale therapeutic agents into the extracellular matrix (ECM) of a tumor is a limiting factor for the sufficient delivery of drugs in tumors. Ultrasound (US) in combination with microbubbles causing cavitation is reported to improve delivery of nanoparticles (NPs) and drugs to tumors. Acoustic radiation force (ARF) could also enhance the penetration of NPs in tumor ECM. In this work, a collagen gel was used as a model for tumor ECM to study the effects of ARF on the penetration of NPs as well as the deformation of collagen gels applying different US parameters (varying pressure and duty cycle). The collagen gel was characterized, and the diffusion of water and NPs was measured. The penetration of NPs into the gel was measured by confocal laser scanning microscopy and numerical simulations were performed to determine the ARF and to estimate the penetration distance and extent of deformation. ARF had no effect on the penetration of NPs into the collagen gels for the US parameters and gel used, whereas a substantial deformation was observed. The width of the deformation on the collagen gel surface corresponded to the US beam. Comparing ARF caused by attenuation within the gel and Langevin pressure caused by reflection at the gel-water surface, ARF was the prevalent mechanism for the gel deformation. The experimental and theoretical results were consistent both with respect to the NP penetration and the gel deformation

Effect of Acoustic Radiation Force on the Distribution of Nanoparticles in Solid Tumors.

Acoustic radiation force (ARF) might improve the distribution of nanoparticles (NPs) in tumors. To study this, tumors growing subcutaneously in mice were exposed to focused ultrasound (FUS) either 15 min or 4 h after the injection of NPs, to investigate the effect of ARF on the transport of NPs across the vessel wall and through the extracellular matrix. Quantitative analysis of confocal microscopy images from frozen tumor sections was performed to estimate the displacement of NPs from blood vessels. Using the same experimental exposure parameters, ARF was simulated and compared to the experimental data. Enhanced interstitial transport of NPs in tumor tissues were observed when FUS (10 MHz, acoustic power 234 W/cm2, 3.3 % duty cycle) was given either 15 min or 4 h after NP administration. According to acoustic simulations, the FUS generated an ARF per unit volume of 2.0 x 106 N/m3. The displacement of NPs was larger when FUS was applied 4h after NP injection compared to after 15 min. This study shows that ARF might contribute to a modest improved distribution of NPs into the tumor interstitium

Effect of ultrasound on the vasculature and extravasation of nanoscale particles imaged in real time

Ultrasound and microbubbles have been found to improve the delivery of drugs and nanoparticles to tumor tissue. To obtain new knowledge on the influence of vascular parameters on extravasation and to elucidate the effect of acoustic pressure on extravasation and penetration of nanoscale particles into the extracellular matrix, real-time intravital multiphoton microscopy was performed during sonication of tumors growing in dorsal window chambers. The impact of vessel diameter, vessel structure and blood flow was characterized. Fluorescein isothiocyanate–dextran (2 MDa) was injected to visualize blood vessels. Mechanical indexes (MI) of 0.2–0.8 and in-house-made, nanoparticle-stabilized microbubbles or Sonovue were applied. The rate and extent of penetration into the extracellular matrix increased with increasing MI. However, to achieve extravasation, smaller vessels required MIs (0.8) higher than those of blood vessels with larger diameters. Ultrasound changed the blood flow rate and direction. Interestingly, the majority of extravasations occurred at vessel branching points

Effect of ultrasound on the vasculature and extravasation of nanoscale particles imaged in real time

Ultrasound and microbubbles have been found to improve the delivery of drugs and nanoparticles to tumor tissue. To obtain new knowledge on the influence of vascular parameters on extravasation and to elucidate the effect of acoustic pressure on extravasation and penetration of nanoscale particles into the extracellular matrix, real-time intravital multiphoton microscopy was performed during sonication of tumors growing in dorsal window chambers. The impact of vessel diameter, vessel structure and blood flow was characterized. Fluorescein isothiocyanate–dextran (2 MDa) was injected to visualize blood vessels. Mechanical indexes (MI) of 0.2–0.8 and in-house-made, nanoparticle-stabilized microbubbles or Sonovue were applied. The rate and extent of penetration into the extracellular matrix increased with increasing MI. However, to achieve extravasation, smaller vessels required MIs (0.8) higher than those of blood vessels with larger diameters. Ultrasound changed the blood flow rate and direction. Interestingly, the majority of extravasations occurred at vessel branching points

The Effect of Sonication on Extravasation and Distribution of Nanoparticles and Dextrans in Tumor Tissue Imaged by Multiphoton Microscopy

Ultrasound (US)and systemic administration of microbubbles (MBs)have been shown to improve the delivery of drugs and nanoparticles (NPs)to tumor tissue. A better understanding of the mechanisms is crucial for effective delivery of NPs and drugs. To elucidate the kinetics of extravasation events, and relate it to the vessel diameter and flow, we have performed real-time intravital multiphoton microscopy during US sonication of tumors growing in dorsal window chambers. We studied the effects of four different mechanical index (MI)levels (0.2 to 0.8)while injecting SonoVue or in-house made MBs with NPs in the shell (NPMB). We found that high MI of 0.8 induced a violent extravasation of both NPs and dextrans. Using lower MIs (0.2-0.6), less extravasation was detected and it occurred in vessels with larger diameters compared to sonication at MI 0.8. The rate of extravasation of both NPs and dextrans, and the displacement of NPs and dextrans from the vessel into the tumor tissue, correlated with MI. The observed extravasation events happened within milliseconds to minutes after the US exposure started. Moreover, we have observed a change of blood flow rate and direction with all the MIs teste

The Effect of Sonication on Extravasation and Distribution of Nanoparticles and Dextrans in Tumor Tissue Imaged by Multiphoton Microscopy

Ultrasound (US)and systemic administration of microbubbles (MBs)have been shown to improve the delivery of drugs and nanoparticles (NPs)to tumor tissue. A better understanding of the mechanisms is crucial for effective delivery of NPs and drugs. To elucidate the kinetics of extravasation events, and relate it to the vessel diameter and flow, we have performed real-time intravital multiphoton microscopy during US sonication of tumors growing in dorsal window chambers. We studied the effects of four different mechanical index (MI)levels (0.2 to 0.8)while injecting SonoVue or in-house made MBs with NPs in the shell (NPMB). We found that high MI of 0.8 induced a violent extravasation of both NPs and dextrans. Using lower MIs (0.2-0.6), less extravasation was detected and it occurred in vessels with larger diameters compared to sonication at MI 0.8. The rate of extravasation of both NPs and dextrans, and the displacement of NPs and dextrans from the vessel into the tumor tissue, correlated with MI. The observed extravasation events happened within milliseconds to minutes after the US exposure started. Moreover, we have observed a change of blood flow rate and direction with all the MIs testedThe Effect of Sonication on Extravasation and Distribution of Nanoparticles and Dextrans in Tumor Tissue Imaged by Multiphoton MicroscopyacceptedVersio