Efficient ultrasound-mediated drug delivery to orthotopic liver tumors - Direct comparison of doxorubicin-loaded nanobubbles and microbubbles.

Liver metastasis is a major obstacle in treating aggressive cancers, and current therapeutic options often prove insufficient. To overcome these challenges, there has been growing interest in ultrasound-mediated drug delivery using lipid-shelled microbubbles (MBs) and nanobubbles (NBs) as promising strategies for enhancing drug delivery to tumors. Our previous work demonstrated the potential of Doxorubicin-loaded C3F8 NBs (hDox-NB, 280 ± 123 nm) in improving cancer treatment in vitro using low-frequency unfocused therapeutic ultrasound (TUS). In this study, we investigated the pharmacokinetics and biodistribution of sonicated hDox-NBs in orthotopic rat liver tumors. We compared their delivery and therapeutic efficiency with size-isolated MBs (hDox-MB, 1104 ± 373 nm) made from identical shell material and core gas. Results showed a similar accumulation of hDox in tumors treated with hDox-MBs and unfocused therapeutic ultrasound (hDox-MB + TUS) and hDox-NB + TUS. However, significantly increased apoptotic cell death in the tumor and fewer off-target apoptotic cells in the normal liver were found upon the treatment with hDox-NB + TUS. The tumor-to-liver apoptotic ratio was elevated 9.4-fold following treatment with hDox-NB + TUS compared to hDox-MB + TUS, suggesting that the therapeutic efficacy and specificity are significantly increased when using hDox-NB + TUS. These findings highlight the potential of this approach as a viable treatment modality for liver tumors. By elucidating the behavior of drug-loaded bubbles in vivo, we aim to contribute to developing more effective liver cancer treatments that could ultimately improve patient outcomes and decrease off-target side effects.

Efficient ultrasound-mediated drug delivery to orthotopic liver tumors - Direct comparison of doxorubicin-loaded nanobubbles and microbubbles.

Liver metastasis is a major obstacle in treating aggressive cancers, and current therapeutic options often prove insufficient. To overcome these challenges, there has been growing interest in ultrasound-mediated drug delivery using lipid-shelled microbubbles (MBs) and nanobubbles (NBs) as promising strategies for enhancing drug delivery to tumors. Our previous work demonstrated the potential of Doxorubicin-loaded C3F8 NBs (hDox-NB, 280 ± 123 nm) in improving cancer treatment in vitro using low-frequency ultrasound. In this study, we investigated the pharmacokinetics and biodistribution of sonicated hDox-NBs in orthotopic rat liver tumors. We compared their delivery and therapeutic efficiency with size-isolated MBs (hDox-MB, 1104 ± 373 nm). Results showed a similar accumulation of hDox in tumors treated with hDox-MBs and unfocused therapeutic ultrasound (hDox-MB+TUS) and hDox-NB+TUS. However, significantly increased apoptotic cell death in the tumor and fewer off-target apoptotic cells in the normal liver were found upon the treatment with hDox-NB+TUS. The tumor-to-liver apoptotic ratio was elevated 9.4-fold following treatment with hDox-NB+TUS compared to hDox-MB+TUS, suggesting that the therapeutic efficacy and specificity are significantly increased when using hDox-NB+TUS. These findings highlight the potential of this approach as a viable treatment modality for liver tumors. By elucidating the behavior of drug-loaded bubbles in vivo, we aim to contribute to developing more effective liver cancer treatments that could ultimately improve patient outcomes and decrease off-target side effects.

Extrusion: A New Method for Rapid Formulation of High-Yield, Monodisperse Nanobubbles.

Shell-stabilized gas microbubbles (MB) and nanobubbles (NB) are frequently used for biomedical ultrasound imaging and therapeutic applications. While it is widely recognized that monodisperse bubbles can be more effective in these applications, the efficient formulation of uniform bubbles at high concentrations is difficult to achieve. Here, it is demonstrated that a standard mini-extruder setup, commonly used to make vesicles or liposomes, can be used to quickly and efficiently generate monodisperse NBs with high yield. In this highly reproducible technique, the NBs obtained have an average diameter of 0.16 ± 0.05 µm and concentration of 6.2 ± 1.8 × 1010  NBs mL-1 compared to 0.32 ± 0.1 µm and 3.2 ± 0.7 × 1011  mL-1 for NBs made using mechanical agitation. Parameters affecting the extrusion and NB generation process including the temperature, concentration of the lipid solution, and the number of passages through the extruder are also examined. Moreover, it is demonstrated that extruded NBs show a strong acoustic response in vitro and a strong and persistent US signal enhancement under nonlinear contrast enhanced ultrasound imaging in mice. The extrusion process is a new, efficient, and scalable technique that can be used to easily produce high yield smaller monodispersed nanobubbles.

First quantitative assessment of the adsorption of a fluorocarbon gas on phospholipid monolayers at the air/water interface.

HYPOTHESIS: Fluorocarbon gases introduced above monolayers of phospholipids at the air/water interface were recently found to promote the adsorption of diverse molecular compounds, with potential application in drug-loaded microbubble design. Quantitative determination of the fluorocarbon present in the monolayers is strongly needed for the development of such applications. We hypothesized that neutron reflectometry (NR) and ellipsometry experiments would allow quantification of the fluorocarbon trapped in the monolayers. EXPERIMENTS: We report the first quantitative determination of the extents of adsorption of perfluorohexane (F-hexane) on different phospholipid monolayers with respect to both their phase and isotopic form. To this aim, we applied an approach based on co-modeling the data obtained from NR and ellipsometry. FINDINGS: We found that F-hexane adsorbs strongly in monolayers of dipalmitoylphosphatidylcholine (DPPC) when they are both in the liquid expanded (LE) and liquid condensed (LC) phases, but to different extents according to the isotopic form of the phospholipid. Kinetic resolution of the interfacial composition from data on both isotopic contrasts (assuming chemical identicality) was therefore not possible using NR alone, so an alternative NR/ellipsometry co-modeling treatment was applied to data from each isotopic contrast. F-hexane adsorbs more abundantly on monolayers of hydrogenous DPPC than chain-deuterated DPPC when they are in the LE phase, whilst the opposite was observed when they monolayers are in the LC phase. The extents of adsorption of F-hexane in monolayers of dimyristoylphosphatidylcholine (DMPC, LE phase) and distearoylphosphatidylcholine (DSPC, LC phase) concurs with the strong dependence of those with phospholipids of different isotopic contrasts according to the monolayer phase. This new methodology can lead to advances in the novel characterization of fluorocarbons interacting with phospholipid monolayers of relevance to applications such as in the shells of fluorocarbon-stabilized medically-oriented microbubbles.

Synthesis and Antimicrobial Properties of a Ciprofloxacin and PAMAM-dendrimer Conjugate.

Infections caused by bacteria resistant to antibiotics are an increasing problem. Multivalent antibiotics could be a solution. In the present study, a covalent conjugate between Ciprofloxacin and a G0-PAMAM dendrimer has been synthesized and tested against clinically relevant Gram-positive and Gram-negative bacteria. The conjugate has antimicrobial activity and there is a positive dendritic effect compared to Ciprofloxacin itself.

Fluorocarbon Exposure Mode Markedly Affects Phospholipid Monolayer Behavior at the Gas/Liquid Interface: Impact on Size and Stability of Microbubbles.

Although most phospholipid-shelled microbubbles (MBs) investigated for medical applications are stabilized by a fluorocarbon (FC) gas, information on the interactions between the phospholipid and FC molecules at the gas/water interface remains scarce. We report that the procedure of introduction of perfluorohexane (F-hexane), that is, either in the gas phase above dimyristoylphosphatidylcholine (DMPC) or dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers, or in the aqueous subphase, radically affects the compression isotherms. When introduced in the gas phase, F-hexane is rapidly incorporated in the interfacial film, but is also readily desorbed upon compression and eventually totally expelled from the phospholipid monolayers. By contrast, when introduced in the aqueous phase, F-hexane remains trapped at the interface. These dissimilar outcomes demonstrate that the phospholipid monolayer acts as a barrier that effectively hinders the transfer of the FC across the interfacial film. F-hexane was also found to significantly accelerate the adsorption kinetics of the phospholipids at the gas/water interface and to lower the interfacial tension, as assessed by bubble profile analysis tensiometry. The extent of these effects is more pronounced when F-hexane is provided from the gas phase. The size and stability characteristics of DMPC- and DPPC-shelled microbubbles were also found to depend on how the FC is introduced. As compared to reference MBs prepared under nitrogen only, introduction of F-hexane always causes a decrease in MB mean radius. However, while for DMPC this decrease depends on the F-hexane introduction procedure, it is independent from the procedure and most pronounced (from ∼2.0 µm to ∼1.0 µm) for DPPC. Introducing the FC in the gas phase has the strongest effect on MB half-life (t1/2 = ∼1.8 and 6.8 h for DMPC and DPPC, respectively), as compared to when it is delivered through the aqueous phase (∼0.8 and ∼1.7 h). Fluorocarbonless reference DMPC and DPPC bubbles had a half-life of ∼0.5 and 0.8 h, respectively. The effects of F-hexane on MB characteristics are discussed with regard to the interactions between phospholipids and F-hexane and monolayer fluidization effect, as revealed by the Langmuir and tensiometric studies.