Ultrasound Sensitive Liposomes Research Articles

Oscillatory effects of ketamine using focused ultrasound sensitive liposomes

The blood brain barrier (BBB) poses a significant challenge in the treatment of neurological disorders by preventing the diffusion of medications into the brain. Focused ultrasound (FUS) enables noninvasive modulation of the central nervous system by targeting millimeter-sized regions of the cortical and sub-cortical brain. We have synthesized ultrasound-sensitive nanoparticles (NPs) to encapsulate small, hydrophobic neuromodulators. Recent data has shown that our NPs deliver pharmacological drugs across the BBB when paired with FUS to the desired region of the brain with targeted accuracy. This method enables us to study the impact of small hydrophobic anesthetics across different regions of the brain. The aim of the study is to determine the electrophysiological effects of FUS neuromodulation in an awake small animal model. Specifically, we aim to understand the oscillatory effects of localized ketamine activity on the thalamocortical system. We hypothesized that localized delivery of ketamine in the central thalamus (CL) will induce slow-delta and gamma oscillations comparable to the recorded frequencies obtained from systemic delivery of ketamine. Using in-house electrocorticogram (ECoG) hardware, we recorded signals from the prefrontal cortex, CL, and visual cortex in awake-restraint rats. Preliminary results suggest that FUS-only neuromodulation of the brain induced undetectable oscillatory differences from baseline signals. We then investigated the electrophysiologic signatures of localized ketamine activity. Ketamine-loaded NPs were administered intravenously to rats via bolus injection and FUS was applied to the desired brain region for site-specific drug uncaging. Initial evidence indicated localized delivery of ketamine induced similar slow-delta and gamma oscillations in a smaller timeframe than those recorded after systemic ketamine administration. These results provide insight into the impacts of pharmacological modulation in relation to brain activity. Future directions include analyzing the thalamocortical system as a potential binding site for ketamine to induce anesthetic-specific oscillations.

Ultrasound-Sensitive Liposomes for Triggered Macromolecular Drug Delivery: Formulation and In Vitro Characterization.

Mistletoe lectin-1 (ML1) is a nature-derived macromolecular cytotoxin that potently induces apoptosis in target cells. Non-specific cytotoxicity to normal cells is one of the major risks in its clinical application, and we therefore propose to encapsulate ML1 in a nanocarrier that can specifically release its cargo intratumorally, thus improving the efficacy to toxicity ratio of the cytotoxin. We investigated the encapsulation of ML1 in ultrasound-sensitive liposomes (USL) and studied its release by high-intensity focused ultrasound (HAccessedIFU). USL were prepared by entrapment of perfluorocarbon nanodroplets in pegylated liposomes. The liposomes were prepared with different DPPC/cholesterol/DSPE-PEG2000 lipid molar ratios (60/20/20 for USL20; 60/30/10 for USL10; 65/30/5 for USL5) before combination with perfluorocarbon (PFC) nanoemulsions (composed of DPPC and perfluoropentane). When triggered with HIFU (peak negative pressure, 2–24 MPa; frequency, 1.3 MHz), PFC nanodroplets can undergo phase transition from liquid to gas thus rupturing the lipid bilayer of usl. Small unilamellar liposomes were obtained with appropriate polydispersity and stability. ML1 and the model protein horseradish peroxidase (HRP) were co-encapsulated with the PFC nanodroplets in USL, with 3% and 7% encapsulation efficiency for USL20 and USL10/USL5, respectively. Acoustic characterization experiments indicated that release is induced by cavitation. HIFU-triggered release of HRP from USL was investigated for optimization of liposomal composition and resulted in 80% triggered release for USL with USL10 (60/30/10) lipid composition. ML1 release from the final USL10 composition was also 80%. Given its high stability, suitable release, and ultrasound sensitivity, USL10 encapsulating ML1 was further used to study released ML1 bioactivity against murine CT26 colon carcinoma cells. Confocal live-cell imaging demonstrated its functional activity regarding the interaction with the target cells. We furthermore demonstrated the cytotoxicity of the released ML1 (I.E., After USL were treated with HIFU). The potent cytotoxicity (IC50 400 ng/ml; free ML1 IC50 345 ng/ml) was compared to non-triggered USL loaded with ML1. Our study shows that USL in combination with HIFU hold promise as trigger-sensitive nanomedicines for local delivery of macromolecular cytotoxins.

State of the Art of Stimuli-Responsive Liposomes for Cancer Therapy.

Specific delivery of therapeutic agents to solid tumors and their bioavailability at the target site are the most clinically important and challenging goals in cancer therapy. Liposomes are promising nanocarriers and have been well investigated for cancer therapy. In spite of preferred accumulation in tumors via the enhanced permeability and retention (EPR) effect, inefficient drug release at the target site and endosomal entrapment of long circulating liposomes are very important obstacles for achieving maximum anticancer efficacy. Thus, additional strategies such as stimulus-sensitive drug release are necessary to improve efficacy. Stimuli-sensitive liposomes are stable in blood circulation, however, activated by responding to external or internal stimuli and control the cargo release at the target site. This review focuses on state of the art of stimuli-responsive liposomes. Both external stimuli-responsive liposomes, including hyperthermia (HT), magnetic, light, and ultrasound-sensitive liposomes and internal stimuli (pH, reduction, and enzyme) responsive liposomes are covered.

하이드록시아파타이트 코팅 리포솜의 초음파에 의한 약물방출

리포솜은 표적 약물을 봉입하여 병소에 안전하게 전달할 수 있는 약물전달체로서 연구되고 있다. 그러나 일반적인 리포솜은 표적부위에서 약물방출이 제한적인 문제점이 있다. 따라서 본 연구에서는 리포솜의 안정성을 향상시키고 표적부위에서 외부 초음파로부터 약물의 방출을 극대화시키기 위하여 하이드록시아파타이트(hydroxyapatite, HA)가 코팅된 리포솜을 개발하였다. 대조군 리포솜은 인지질과 콜레스테롤을 이용하여 제조하였고, 대조군 리포솜의 표면에 칼슘 아세테이트, 포스포릭에시드, 그리고 25% 암모니아용액을 이용하여 HA를 코팅하였다. 모델 약물로는 독소루비신을 사용하였다. HA코팅 리포솜의 크기는 120 nm 이었고, 약물봉입효율은 95% 이상이었다. 30% 혈장용액 내에서 HA코팅 리포솜의 입자크기는 일정한 상태를 유지하였으며, 대조군 리포솜은 크기가 1.4배 증가하였다. 외부 초음파 자극에 의한 리포솜으로부터 약물 방출을 유도한 후, 방출된 약물의 세포 이입율은 HA 코팅된 리포솜이 3배 이상 대조군 리포솜에 비하여 증가하였다. 본 연구에서는 외부 초음파 자극에 의하여 리포솜으로부터 약물의 방출을 극대화시키기 위한 초음파 민감형 리포솜을 개발하였고, 본 제형은 표적부위에서 약물의 방출을 효과적으로 제어하기 위한 분야에 활용이 가능할 것이다. Liposomes, which can deliver payload at target site, have been studied as drug carrier. However, conventional liposomes have limitation for drug release at target site. Therefore, we developed hydroxyapatite (HA) coated ultrasound sensitive liposomes to increase drug release at target site and to enhance stability in blood stream. Control liposome was prepared using hydrogenated soy phosphatidylcholine (HSPC) and cholesterol, and then we assessed HA coating on the surface of control liposomes using calcium acetate, phosphoric acid, and 25% ammonium solution. Doxorubicin was used as a model drug. Size of HA coated liposomes was 120 nm and encapsulation efficiency of doxorubicin in liposomes was up to 95%. Size of HA coated liposomes are not changed in 30% serum solution, however, the control liposomes was 1.4 fold increased. After ultrasound triggered drug release from liposomes, intracellular efficiency of drug released from HA coated liposomes was 3 fold increased compared to control liposomes. In this study, we developed ultrasound sensitive liposomes to enhance drug release, which will be applied in controlled drug release at disease site.

Dual Functional Gd(III)-DOTA Liposomes for Cancer Therapy and Diagnosis as a Theragnostic Carrier

Development of dual functional liposome has been studied for cancer theragnostics. Therefore, we focused on ultrasound-sensitive liposomes with doxorubicin (DOX) and gadolinium (Gd) as a theragnostic carrier having a potential for cancer therapy and diagnosis. In this study, Gd(III)-DOTA-modified sonosensitive liposomes (GL) was developed using chemically synthesized Gd(III)-DOTA-DPPE lipid. Sonosensitivity of GL to 1 MHz ultrasound induced 25% of DOX release. The relaxivities () of GL were , which was higher than that of MR-bester. Intracellular delivery of DOX from GL by ultrasound irradiation was evaluated according to ultrasound intensity, resulting in increase of uptake of DOX released from ultrasound-triggered GLs compared to GL3 or Doxil without ultrasound. Taken together, this study shows that the paramagnetic and sonosensitive liposomes, GL, is a novel and highly effective delivery system for drug with the potential for broad applications in human disease.

Cancer gene therapy by IL-12 gene delivery using liposomal bubbles and tumoral ultrasound exposure

Interleukin-12 (IL-12) gene therapy is expected to be effective against cancers because it primes the immune system for cancer cells. In this therapy, it is important to induce IL-12 gene expression in the tumor tissue. Sonoporation is an attractive technique for developing non-invasive and non-viral gene delivery systems, but simple sonoporation using only ultrasound is not an effective cancer gene therapy because of the low efficiency of gene delivery. We addressed this problem by combining ultrasound and novel ultrasound-sensitive liposomes (Bubble liposomes) which contain the ultrasound imaging gas perfluoropropane. Our previous work showed that this is an effective gene delivery system, and that Bubble liposome collapse (cavitation) is induced by ultrasound exposure. In this study, we assessed the utility of this system in cancer gene therapy using IL-12 corded plasmid DNA. The combination of Bubble liposomes and ultrasound dramatically suppressed tumor growth. This therapeutic effect was T-cell dependent, requiring mainly CD8 + T lymphocytes in the effector phase, as confirmed by a mouse in vivo depletion assay. In addition, migration of CD8 + T cells was observed in the mice, indicating that the combination of Bubble liposomes and ultrasound is a good non-viral vector system in IL-12 cancer gene therapy.

483. Acoustically Active Liposomes for Oligonucleotide/Drug Encapsulation; Delivery Agents with Capacity for Ultrasound-Triggered Release

Liposomes can carry many different kinds of therapeutic agents. Acoustically active liposomes (AAL), which contain small amounts of air within their bilayers, were previously developed by our group. These AAL also have the potential to carry oligonucleotides and their acoustic activity could enable them to respond to local ultrasound stimulation by releasing their contents at a disease site. Liposomes were composed of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and cholesterol at a molecular ratio of 69:8:8:15 and made acoustically active with a procedure involving hydrating the lipid film, sonication, freezing in the presence of mannitol, lyophilization, and rehydration. A FITC-labeled oligonuleotide (ODN, 12 bp) was added at the hydration step. Encapsulation efficiency was measured after Sepharose 4B chromotography. For other encapsuation as well as for release measurements, calcein was used as a test molecule because it is a convenient fluorescent probe for uptake and leakage determinations. The procedure of freeze-drying in the presence of mannitol has been found to be a superior method for oligonucleotide encapsulation. Approximally 25% encapsulation was obtained with one freeze-thaw cycle (Figure 1), which is similar to the encapsulation of calcein (20%). One MHz ultrasound at 2 W/cm2, 100% duty cycle, was applied to loaded, acoustically active liposomes for 10s intervals and caused 32% release of calcein. Six such applications released 62% of original contents. Release of contents was highly correlated with the loss of air (Figure 2) induced either by ultrasound or rapid pressure reduction, indicating that pressure-induced stress on liposome-associated air pockets is responsible for ultrasound-triggered drug release. This encapsulation and release technique should also be applicable to siRNA's, since recent research has found that delivery methods developed for ODN are also efficient for siRNA. The ultrasound-sensitive liposomes provides the distinct advantage of allowing control and localization of the release of nucleotide-based and other hydrophilic therapeutic agents. Furthermore, the destruction of microbubbles may facilitate nucleotide transport across biological membranes. Ultrasound image enhancement by these liposomes may also facilitate identification of regions of disease, allowing further improvements in site-specific delivery.