Sonoporation: Gene transfer using ultrasound

Acoustofluidic Measurements on Polymer-Coated Microbubbles: Primary and Secondary Bjerknes Forces

The acoustically-driven dynamics of isolated particle-like objects in microfluidic environments is a well-characterised phenomenon, which has been the subject of many studies. Conversely, very few acoustofluidic researchers looked at coated microbubbles, despite their widespread use in diagnostic imaging and the need for a precise characterisation of their acoustically-driven behaviour, underpinning therapeutic applications. The main reason is that microbubbles behave differently, due to their larger compressibility, exhibiting much stronger interactions with the unperturbed acoustic field (primary Bjerknes forces) or with other bubbles (secondary Bjerknes forces). In this paper, we study the translational dynamics of commercially-available polymer-coated microbubbles in a standing-wave acoustofluidic device. At increasing acoustic driving pressures, we measure acoustic forces on isolated bubbles, quantify bubble-bubble interaction forces during doublet formation and study the occurrence of sub-wavelength structures during aggregation. We present a dynamic characterisation of microbubble compressibility with acoustic pressure, highlighting a threshold pressure below which bubbles can be treated as uncoated. Thanks to benchmarking measurements under a scanning electron microscope, we interpret this threshold as the onset of buckling, providing a quantitative measurement of this parameter at the single-bubble level. For acoustofluidic applications, our results highlight the limitations of treating microbubbles as a special case of solid particles. Our findings will impact applications where knowing the buckling pressure of coated microbubbles has a key role, like diagnostics and drug delivery.

Nucleic acid-based vaccines targeting respiratory syncytial virus: Delivering the goods

Respiratory syncytial virus (RSV) is a massive medical burden on a global scale. Infants, children and the elderly represent the vulnerable populations. Currently there is no approved vaccine to protect against the disease. Vaccine development has been hindered by several factors including vaccine enhanced disease (VED) associated with formalin-inactivated RSV vaccines, inability of target populations to raise protective immune responses after vaccination or natural viral infection, and a lack of consensus concerning the most appropriate virus-associated target antigen. However, with recent advances in the molecular understanding of the virus, and design of highly characterized vaccines with enhanced immunogenicity there is new belief a RSV vaccine is possible. One promising approach is nucleic acid-based vaccinology. Both DNA and mRNA RSV vaccines are showing promising results in clinically relevant animal models, supporting their transition into humans. Here we will discuss this strategy to target RSV, and the ongoing studies to advance the nucleic acid vaccine platform as a viable option to protect vulnerable populations from this important disease.

Pre-Treatment with Either L-Carnitine or Piracetam Increases Ultrasound-Mediated Gene Transfection by Reducing Sonoporation-Associated Apoptosis

Sonoporation, the use of ultrasound to alter the permeability of cell membranes, is a non-viral technique used to facilitate gene delivery, possibly by opening transient pores in the cell membrane. However, sonoporation may have negative bio-effects on cells, such as causing apoptosis, which limits its efficacy in gene delivery. In this study, we investigated whether pre-treatment with either L-carnitine or piracetam could protect cells from undergoing apoptosis after sonoporation and the possible mechanisms. We found that either L-carnitine or piracetam can promote gene transfection without reducing cell viability, possibly by reducing cavitation-induced reactive oxygen species generation, reversing alterations of mitochondrial membrane potential, preventing caspase-3/7 activity and facilitating mitochondrial ATP production. In conclusion, pre-treatment with either L-carnitine or piracetam could protect cells from sonoporation-associated apoptosis by preserving mitochondrial function.

Multiparametric US for scrotal diseases

Multiparametric US is increasingly recognized as a valuable problem-solving technique in scrotal pathologies. Compared to conventional Doppler modes, contrast-enhanced ultrasonography (CEUS) has higher sensitivity in assessing the presence or absence of flows, and to improve differentiation between poorly vascularized tumors and non-neoplastic, avascular lesions. Characterization of benign and malignant complex cysts is improved. In trauma patients, CEUS can help evaluating the viability of testicular parenchyma. In patients with severe epididymo-orchitis, it allows unequivocal assessment of post-inflammatory ischemic changes and abscess formation. CEUS does not add significantly to conventional Doppler modes in spermatic cord torsion. Attempt of differentiating benign and malignant tumors remains a research tool. In the clinical practice, elastography has a limited role for tumor characterization. The majority of malignant tumors are stiff at elastography, but they may display soft areas, or appear globally soft. A quantitative evaluation of testicular stiffness is feasible using shear-wave elastography. Potential clinical applications for elastographic modes could include work-up of infertile patients.

Interstitial Matrix Prevents Therapeutic Ultrasound From Causing Inertial Cavitation in Tumescent Subcutaneous Tissue

We search for cavitation in tumescent subcutaneous tissue of a live pig under application of pulsed, 1-MHz ultrasound at 8 W cm^-2 spatial peak and pulse-averaged intensity. We find no evidence of broadband acoustic emission indicative of inertial cavitation. These acoustic parameters are representative of those used in external-ultrasound-assisted lipoplasty and in physical therapy and our null result brings into question the role of cavitation in those applications. A comparison of broadband acoustic emission from a suspension of ultrasound contrast agent in bulk water with a suspension injected subcutaneously indicates that the interstitial matrix suppresses cavitation and provides an additional mechanism behind the apparent lack of in-vivo cavitation to supplement the absence of nuclei explanation offered in the literature. We also find a short-lived cavitation signal in normal, non-tumesced tissue that disappears after the first pulse, consistent with cavitation nuclei depletion in vivo.

Biomaterial-Guided Gene Delivery for Musculoskeletal Tissue Repair

Gene therapy is a promising strategy for musculoskeletal tissue repair and regeneration where local and sustained expression of proteins and/or therapeutic nucleic acids can be achieved. However, the musculoskeletal tissues present unique engineering and biological challenges as recipients of genetic vectors. Targeting specific cell populations, regulating expression in vivo, and overcoming the harsh environment of damaged tissue accompany the general concerns of safety and efficacy common to all applications of gene therapy. In this review, we will first summarize these challenges and then discuss how biomaterial carriers for genetic vectors can address these issues. Second, we will review how limitations specific to given vectors further motivate the utility of biomaterial carriers. Finally, we will discuss how these concepts have been combined with tissue engineering strategies and approaches to improve the delivery of these vectors for musculoskeletal tissue regeneration.

Intracellular triggered release of DNA-quaternary ammonium polyplex by ultrasound

2-Methacryloyloxy ethyl trimethyl ammonium chloride (TMA) is a potent polymeric plasma DNA (pDNA) carrier. The present study shows that TMA/pDNA polyplexes could be internalized into cells efficiently, but could not mediate gene transfection on its own. The transfection process of TMA/pDNA polyplexes is turned on only when ultrasound (US) was applied 4-8h after incubating TMA/pDNA polyplexes with target cells (with a gene expression 1000 times that of the immediate US group). US is a widely used physical method for gene delivery; its transfection efficiency can be significantly enhanced when combined with cationic polymer vectors. Traditionally, US is given simultaneously with genetic materials, carriers and microbubbles to exert maximal efficacy. The unique on-off phenomenon of TMA/pDNA polyplexes, controlled by US exposure, was found to relate to the endosomal escape effect of US since the polyplexes colocalized well with the lysosome marker if no US was given or was given at inappropriate times. The proposed delivery system using US and TMA carriers has potential in many pharmaceutical applications requiring precise temporal and spatial release control.

Introduction of plasmids into gastric cancer cells by endoscopic ultrasound

Short hairpin RNA of frizzled-2 (shRNA-Fz2) suppresses the cell proliferation of gastric cancer cells. Endoscopic ultrasound (EUS) is considered a suitable method for the introduction of therapeutic plasmids into cells, since the device enables the access and real-time monitoring of gastric cancer tissues. In the present study, plasmids were introduced into cells by sonoporation, as evidenced by the production of H2O2. The production of H2O2 was measured by absorbance of a potassium-starch solution irradiated with EUS. Luciferase activity was analyzed in the cells irradiated with EUS after the addition of a pMetLuc2-control in the media, and cell proliferation was analyzed using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt assay after irradiation with EUS following the addition of shRNA-Fz2. Absorbance levels corresponding to free radical levels were found to be higher in the cells irradiated with EUS. Luciferase activities were found to be significantly higher in the transfected cells (plasmid with Lipofectamine LTX) than in untreated cells and were furthermore found to be higher in MKN45 cells irradiated for 0.5 min than in cells not subjected to irradiation. Luciferase activity was also found to be higher in MKN74 cells irradiated for 2 min than in cells that were not irradiated. Although the cell proliferation of the MKN45 cells tended to be suppressed by irradiation with EUS, this was non-significant suppression, while the cell proliferation of MKN74 cells was found to be suppressed by irradiation with 12 MHz for 2 min (P<0.05). In conclusion, plasmids were introduced into cultured gastric cancer cells by irradiation with EUS due to sonoporation, as evidenced by the production of H2O2; however, the efficiency of the plasmid introduction was low compared with a traditional transfection approach.

Journey to the Center of the Cell: Current Nanocarrier Design Strategies Targeting Biopharmaceuticals to the Cytoplasm and Nucleus

New biopharmaceutical molecules, potentially able to provide more personalized and effective treatments, are being identified through the advent of advanced synthetic biology strategies, sophisticated chemical synthesis approaches, and new analytical methods to assess biological potency. However, translation of many of these structures has been significantly limited due to the need for more efficient strategies to deliver macromolecular therapeutics to desirable intracellular sites of action. Engineered nanocarriers that encapsulate peptides, proteins, or nucleic acids are generally internalized into target cells via one of several endocytic pathways. These nanostructures, entrapped within endosomes, must navigate the intracellular milieu to orchestrate delivery to the intended destination, typically the cytoplasm or nucleus. For therapeutics active in the cytoplasm, endosomal escape continues to represent a limiting step to effective treatment, since a majority of nanocarriers trapped within endosomes are ultimately marked for enzymatic degradation in lysosomes. Therapeutics active in the nucleus have the added challenges of reaching and penetrating the nuclear envelope, and nuclear delivery remains a preeminent challenge preventing clinical translation of gene therapy applications. Herein, we review cutting-edge peptide- and polymer-based design strategies with the potential to enable significant improvements in biopharmaceutical efficacy through improved intracellular targeting. These strategies often mimic the activities of pathogens, which have developed innate and highly effective mechanisms to penetrate plasma membranes and enter the nucleus of host cells. Understanding these mechanisms has enabled advances in synthetic peptide and polymer design that may ultimately improve intracellular trafficking and bioavailability, leading to increased access to new classes of biotherapeutics.

Irreversible electroporation inhibits pro-cancer inflammatory signaling in triple negative breast cancer cells

Low-level electric fields have been demonstrated to induce spatial re-distribution of cell membrane receptors when applied for minutes or hours. However, there is limited literature on the influence on cell signaling with short transient high-amplitude pulses typically used in irreversible electroporation (IRE) for cancer treatment. Moreover, literature on signaling pertaining to immune cell trafficking after IRE is conflicting. We hypothesized that pulse parameters (field strength and exposure time) influence cell signaling and subsequently impact immune-cell trafficking. This hypothesis was tested in-vitro on triple negative breast cancer cells treated with IRE, where the effects of pulse parameters on key cell signaling factors were investigated. Importantly, real time PCR mRNA measurements and ELISA protein analyses revealed that thymic stromal lymphopoietin (TSLP) signaling was down regulated by electric field strengths above a critical threshold, irrespective of exposure times spanning those typically used clinically. Comparison with other treatments (thermal shock, chemical poration, kinase inhibitors) revealed that IRE has a unique effect on TSLP. Because TSLP signaling has been demonstrated to drive pro-cancerous immune cell phenotypes in breast and pancreatic cancers, our finding motivates further investigation into the potential use of IRE for induction of an anti-tumor immune response in vivo.

Efficacy of Combined Ultrasound-and-Microbubbles-Mediated Diclofenac Gel Delivery to Enhance Transdermal Permeation in Adjuvant-Induced Rheumatoid Arthritis in the Rat

A previous study that investigated the effect of ultrasound (US) on the transdermal permeation of the non-steroidal anti-inflammatory drug diclofenac found that therapeutic US can increase circulation in an inflamed joint and decrease arthritic pain. Transdermal drug delivery has recently been demonstrated by US combined with microbubbles (MB) contrast agent (henceforth referred to as "US-MB"). The present study evaluated the efficacy of US-MB-mediated diclofenac delivery for treating adjuvant-induced rheumatoid arthritis (RA) in rats. RA was induced by injecting 100 μL of complete Freund's adjuvant into the ankle joint of male Sprague-Dawley rats (250-300 g) that were randomly divided into five treatment groups: (i) carbopol gel alone (the control [group C]), (ii) diclofenac-carbopol gel (group D), (iii) US plus carbopol gel (group U), (iv) US plus diclofenac-carbopol gel (group DU) and (v) US-MB plus diclofenac-carbopol gel (group DUB). The ankle width was measured over 10 d using high-frequency (40-MHz) US B-mode and color Doppler-mode imaging, covering the period before and after treatment. Longitudinal US images of the induced RA showed synovitis and neovascularity. Only a small amount of neovascularity was observed after treatment. The recovery rate on day 10 was significantly higher in group DUB (97.7% ± 2.7%, mean ± standard deviation [SD]) than in groups C (1.0% ± 2.7%), D (37.5% ± 4.6%), U (75.5% ± 4.2%) and DU (87.3% ± 5.2%) (p < 0.05). The results obtained indicate that combining US and MB can increase the skin permeability and thereby enhance the delivery of diclofenac sodium gel and thereby inhibit inflammation of the tissues surrounding the arthritic ankle. Color Doppler-mode imaging revealed that US-MB treatment induced a rapid reduction in synovial neoangiogenesis in the arthritic area.

Low-frequency ultrasound-mediated microvessel disruption combined with docetaxel to treat prostate carcinoma xenografts in nude mice: A novel type of chemoembolization

The aim of the present study was to investigate whether low-frequency ultrasound (US)-mediated microvessel disruption combined with docetaxel (DTX) can be used as a novel type of chemoembolization. Mice were assigned to four groups: i) The USMB group, treated with low-frequency US combined with microbubbles (USMB); ii) the DTX group, treated with DTX; iii) the USMB + DTX group, treated with combined therapy; and iv) the control group, which was untreated. Immediately after the first treatment, the average peak intensity (API) on contrast-enhanced US was calculated, and tumors were excised for hematoxylin and eosin (HE) staining. At 2 weeks post-treatment, the tumor volumes and wet weights were calculated, and tumors were excised for immunohistochemistry to calculate apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) values. Immediately after the first treatment, in the DTX and control groups, the tumors demonstrated abundant perfusion enhancement, while in the USMB + DTX and USMB groups, blood perfusion of the tumors was interrupted. Compared with that of the control group, the API was significantly lower in the USMB + DTX USMB groups (all P<0.001). HE staining showed that tumor microvasculature was disrupted into flaky hematomas and severely dilated microvessels in the USMB + DTX and USMB groups. In the DTX and control groups, there was no distinct evidence of the disruption and dilation of blood microvessels. At the end of the treatment, the mean tumor inhibition ratio was 73.33, 46.67 and 33.33% for the USMB + DTX, DTX and USMB groups, respectively. The USMB + DTX group had the highest AI, and the lowest PI and MVD compared with the other groups, although the difference between the USMB + DTX and DTX groups with regard to PI and MVD was not significant (USMB + DTX vs. DTX group, P=0.345 and P=0.059, respectively). In conclusion, as a novel type of chemoembolization, USMB combined with DTX is more effective than USMB or DTX alone in inhibiting tumor growth via the enhancement of apoptosis, and the suppression of proliferation and angiogenesis.

Liposome-mediated transfection of wild-type P53 DNA into human prostate cancer cells is improved by low-frequency ultrasound combined with microbubbles

Prostate cancer is a common type of cancer in elderly men. The aim of the present study was to evaluate the effects of ultrasound exposure in combination with SonoVue microbubbles on liposome-mediated transfection of wild-type P53 genes into human prostate cancer cells. PC-3 human prostate cancer cells were exposed to ultrasound; duty cycle was controlled at 20% (2 sec on, 8 sec off) for 5 min with and without SonoVue microbubble echo-contrast agent using a digital sonifier (frequency, 21 kHz; intensity, 46 mW/cm²). The cells were divided into eight groups, as follows: Group A (SonoVue + wild-type P53), group B (ultrasound + wild-type P53), group C (SonoVue + ultrasound + wild-type P53), group D (liposome + wild-type P53), group E (liposome + SonoVue + wild-type P53), group F (liposome + wild-type P53 + ultrasound), group G (liposome + wild-type P53 + ultrasound + SonoVue) and the control group (wild-type P53). Following treatment, a hemocytometer was used to measure cell lysis, reverse transcription-quantitative polymerase chain reaction and western blotting were performed to detect P53 gene transfection efficiency, Cell Counting Kit-8 was employed to reveal cell proliferation and Annexin V/propidium iodide staining was used to determine cell apoptosis. Cell lysis was minimal in each group. Wild-type P53 gene and protein expression were significantly increased in the PC-3 cells in group G compared with the control and all other groups (P<0.01). Cell proliferation was significantly suppressed in group G compared with the control group and all other groups (P<0.01). Cell apoptosis levels in group G were significantly improved compared with the control group and all other groups (P<0.01). Thus, the results of the present study indicate that the use of low-frequency and low-energy ultrasound in combination with SonoVue microbubbles may be a potent physical method for increasing liposome gene delivery efficiency.

Targeted gene delivery to the synovial pannus in antigen-induced arthritis by ultrasound-targeted microbubble destruction in vivo

The purpose of this study was to optimize an ultrasound-targeted microbubble destruction (UTMD) technique to improve the in vivo transfection efficiency of the gene encoding enhanced green fluorescent protein (EGFP) in the synovial pannus in an antigen-induced arthritis rabbit model. A mixture of microbubbles and plasmids was locally injected into the knee joints of an antigen-induced arthritis (AIA) rabbits. The plasmid concentrations and ultrasound conditions were varied in the experiments. We also tested local articular and intravenous injections. The rabbits were divided into five groups: (1) ultrasound+microbubbles+plasmid; (2) ultrasound+plasmid; (3) microbubble+plasmid; (4) plasmid only; (5) untreated controls. EGFP expression was observed by fluorescent microscope and immunohistochemical staining in the synovial pannus of each group. The optimal plasmid dosage and ultrasound parameter were determined based on the results of EGFP expression and the present and absent of tissue damage under light microscopy. The irradiation procedure was performed to observe the duration of the EGFP expression in the synovial pannus and other tissues and organs, as well as the damage to the normal cells. The optimal condition was determined to be a 1-MHz ultrasound pulse applied for 5 min with a power output of 2 W/cm(2) and a 20% duty cycle along with 300 μg of plasmid. Under these conditions, the synovial pannus showed significant EGFP expression without significant damage to the surrounding normal tissue. The EGFP expression induced by the local intra-articular injection was significantly more increased than that induced by the intravenous injection. The EGFP expression in the synovial pannus of the ultrasound+microbubbles+plasmid group was significantly higher than that of the other four groups (P<0.05). The expression peaked on day 5, remained detectable on day 40 and disappeared on day 60. No EGFP expression was detected in the other tissues and organs. The UTMD technique can significantly enhance the in vivo gene transfection efficiency without significant tissue damage in the synovial pannus of an AIA model. Thus, this could become a safe and effective non-viral gene transfection procedure for arthritis therapy.

Suppression of hepatocellular carcinoma cell proliferation by short hairpin RNA of frizzled 2 with Sonazoid-enhanced irradiation

Short-hairpin RNA of frizzled-2 (shRNA-Fz2) is known to suppress the proliferation of hepatocellular carcinoma (HCC) cells; however, its effect on HCC cell motility is unknown. In this study, suppression of HCC cell motility by shRNA-Fz2 was analyzed, and introduction of shRNA-Fz2 into HCC cells was facilitated with ultrasound (US) irradiation generated from a diagnostic US device, which was enhanced by the contrast-enhanced US reagent Sonazoid. The HCC cell lines HLF and PLC/PRF/5 that were transfected with shRNA-Fz2 were plated to form monolayers, following which the cell monolayers were scratched with a sterile razor. After 48 h, the cells were stained with hematoxylin and eosin, and the distance between the growing edge of the cell layer and the scratch lines was measured. Total RNA from the cells was isolated and subjected to real-time quantitative PCR to quantify matrix metalloproteinase 9 expression at 48 h after transfection of shRNA-Fz2. Starch-iodide method was applied to analyze the generation of H2O2 following US irradiation with the addition of Sonazoid in the liquid, and cell proliferation was analyzed 72 h later. The distances between the growing edge of the cell layer and the scratch lines and MMP9 expression levels were significantly decreased with transfection of shRNA-Fz2 (P<0.05). In the starch-iodide method, absorbance significantly decreased with the addition of Sonazoid (P<0.05), which suggested that US irradiation with Sonazoid generated H2O2 and enhanced sonoporation. ShRNA-Fz2 suppressed cell proliferation of both cell lines at a mechanical index of 0.4. Motility of HLF cells and PLC/PRF/5 cells was suppressed by shRNA-FZ2. Sonazoid enhanced sonoporation of the cells with the diagnostic US device and the suppression of proliferation of both HCC cell lines by shRNA-Fz2.

Ultrasound-targeted microbubble destruction (UTMD) assisted delivery of shRNA against PHD2 into H9C2 cells

Gene therapy has great potential for human diseases. Development of efficient delivery systems is critical to its clinical translation. Recent studies have shown that microbubbles in combination with ultrasound (US) can be used to facilitate gene delivery. An aim of this study is to investigate whether the combination of US-targeted microbubble destruction (UTMD) and polyethylenimine (PEI) (UTMD/PEI) can mediate even greater gene transfection efficiency than UTMD alone and to optimize ultrasonic irradiation parameters. Another aim of this study is to investigate the biological effects of PHD2-shRNA after its transfection into H9C2 cells. pEGFP-N1 or eukaryotic shPHD2-EGFP plasmid was mixed with albumin-coated microbubbles and PEI to form complexes for transfection. After these were added into H9C2 cells, the cells were exposed to US with various sets of parameters. The cells were then harvested and analyzed for gene expression. UTMD/PEI was shown to be highly efficient in gene transfection. An US intensity of 1.5 W/cm², a microbubble concentration of 300μl/ml, an exposure time of 45s, and a plasmid concentration of 15μg/ml were found to be optimal for transfection. UTMD/PEI-mediated PHD2-shRNA transfection in H9C2 cells significantly down regulated the expression of PHD2 and increased expression of HIF-1α and downstream angiogenesis factors VEGF, TGF-β and bFGF. UTMD/PEI, combined with albumin-coated microbubbles, warrants further investigation for therapeutic gene delivery.

Multiple sessions of liposomal doxorubicin delivery via focused ultrasound mediated blood-brain barrier disruption: a safety study

Transcranial MRI-guided focused ultrasound is a rapidly advancing method for delivering therapeutic and imaging agents to the brain. It has the ability to facilitate the passage of therapeutics from the vasculature to the brain parenchyma, which is normally protected by the blood-brain barrier (BBB). The method's main advantages are that it is both targeted and noninvasive, and that it can be easily repeated. Studies have shown that liposomal doxorubicin (Lipo-DOX), a chemotherapy agent with promise for tumors in the central nervous system, can be delivered into the brain across BBB. However, prior studies have suggested that doxorubicin can be significantly neurotoxic, even at small concentrations. Here, we studied whether multiple sessions of Lipo-DOX administered after FUS-induced BBB disruption (FUS-BBBD) induces severe adverse events in the normal brain tissues. First, we used fluorometry to measure the doxorubicin concentrations in the brain after FUS-BBBD to ensure that a clinically relevant doxorubicin concentration was achieved in the brain. Next, we performed three weekly sessions with FUS-BBBD±Lipo-DOX administration. Five to twelve targets were sonicated each week, following a schedule described previously in a survival study in glioma-bearing rats (Aryal et al., 2013). Five rats received three weekly sessions where i.v. injected Lipo-DOX was combined with FUS-BBBD; an additional four rats received FUS-BBBD only. Animals were euthanized 70days from the first session and brains were examined in histology. We found that clinically-relevant concentrations of doxorubicin (4.8±0.5μg/g) were delivered to the brain with the sonication parameters (0.69MHz; 0.55-0.81MPa; 10ms bursts; 1Hz PRF; 60s duration), microbubble concentration (Definity, 10μl/kg), and the administered Lipo-DOX dose (5.67mg/kg) used. The resulting concentration of Lipo-DOX was reduced by 32% when it was injected 10min after the last sonication compared to cases where the agent was delivered before sonication. In histology, the severe neurotoxicity observed in some previous studies with doxorubicin by other investigators was not observed here. However, four of the five rats who received FUS-BBBD and Lipo-DOX had regions (dimensions: 0.5-2mm) at the focal targets with evidence of minor prior damage, either a small scar (n=4) or a small cyst (n=1). The focal targets were unaffected in rats who received FUS-BBBD alone. The result indicates that while delivery of Lipo-DOX to the rat brain might result in minor damage, the severe neurotoxicity seen in earlier works does not appear to occur with delivery via FUS-BBB disruption. The damage may be related to capillary damage produced by inertial cavitation, which might have resulted in excessive doxorubicin concentrations in some areas.