Targeted vascular delivery of antisense molecules using intravenous microbubbles

Targeted Microbubbles for Drug, Gene, and Cell Delivery in Therapy and Immunotherapy

Microbubbles are 1-10 μm diameter gas-filled acoustically-active particles, typically stabilized by a phospholipid monolayer shell. Microbubbles can be engineered through bioconjugation of a ligand, drug and/or cell. Since their inception a few decades ago, several targeted microbubble (tMB) formulations have been developed as ultrasound imaging probes and ultrasound-responsive carriers to promote the local delivery and uptake of a wide variety of drugs, genes, and cells in different therapeutic applications. The aim of this review is to summarize the state-of-the-art of current tMB formulations and their ultrasound-targeted delivery applications. We provide an overview of different carriers used to increase drug loading capacity and different targeting strategies that can be used to enhance local delivery, potentiate therapeutic efficacy, and minimize side effects. Additionally, future directions are proposed to improve the tMB performance in diagnostic and therapeutic applications.

Targeted, Site-Specific, Delivery Vehicles of Therapeutics for COVID-19 Patients. Brief Review

Definitive pharmacological therapies for COVID-19 have yet to be identified. Several hundred trials are ongoing globally in the hope of a solution. However, nearly all treatments rely on systemic delivery but COVID-19 damages the lungs preferentially. The use of a targeted delivery approach is reviewed where engineered products are able to reach damaged lung tissue directly, which includes catheter-based and aerosol-based approaches. In this review we have outlined various target directed approaches which include microbubbles, extracellular vesicles including exosomes, adenosine nanoparticles, novel bio-objects, direct aerosol targeted pulmonary delivery and catheter-based drug delivery with reference to their relative effectiveness for the specific lesions. Currently several trials are ongoing to determine the effectiveness of such delivery systems alone and in conjunction with systemic therapies. Such approaches may prove to be very effective in the controlled and localized COVID-19 viral lesions in the lungs and potential sites. Moreover, localized delivery offered a safer delivery mode for such drugs which may have systemic adverse effects.

The ultrasound contrast imaging properties of lipid microbubbles loaded with urokinase in dog livers and their thrombolytic effects when combined with low-frequency ultrasound in vitro

A new microbubble loaded with urokinase (uPA-MB) was explored in a previous study. However, its zeta potential and ultrasound contrast imaging properties and its thrombolytic effects when combined with low-frequency ultrasound (LFUS) were unclear. The zeta potential and ultrasound contrast imaging property of 5 uPA-MBs loading with 50,000 IU uPA was respectively detected using a Malvern laser particle analyzer and a Logiq 9 digital premium ultrasound system. Its ultrasound contrast imaging property was performed on the livers of two healthy dogs to compare with SonoVue. And the clot mass loss rate, D-dimer concentration and surface morphology of the clot residues were measured to evaluate the thrombolytic effect after treatment with three doses of 5 uPA-MBs combined with LFUS in vitro. The zeta potential of 5 uPA-MBs (-27.0 ± 2.40 mV) was higher than that of normal microbubbles (-36.95 ± 1.77 mV). Contrast-enhanced imaging of the hepatic vessels using 5 uPA-MBs was similar to SonoVue, while the imaging duration of 5 uPA-MBs (10 min) was longer than SonoVue (6 min). The thrombolytic effect of three doses of uPA-MBs combined with LFUS was significantly better than that of the control group and showed dose dependence. The 5 uPA-MBs have a negative charge on their surface and good echogenicity as ultrasound contrast agents. The 5 uPA-MBs combined with LFUS can promote thrombolysis in a dose-dependent manner.

Nucleic acid delivery with microbubbles and ultrasound

Nucleic acid-based therapy is a growing field of drug delivery research. Although ultrasound has been suggested to enhance transfection decades ago, it took a combination of ultrasound with nucleic acid carrier systems (microbubbles, liposomes, polyplexes, and viral carriers) to achieve reasonable nucleic acid delivery efficacy. Microbubbles serve as foci for local deposition of ultrasound energy near the target cell, and greatly enhance sonoporation. The major advantage of this approach is in the minimal transfection in the non-insonated non-target tissues. Microbubbles can be simply co-administered with the nucleic acid carrier or can be modified to carry nucleic acid themselves. Liposomes with embedded gas or gas precursor particles can also be used to carry nucleic acid, release and deliver it by the ultrasound trigger. Successful testing in a wide variety of animal models (myocardium, solid tumors, skeletal muscle, and pancreas) proves the potential usefulness of this technique for nucleic acid drug delivery.

Treatment of acute heart failure in the emergency department

Millions of patients are hospitalized for acute heart failure (AHF) every year throughout the world. Despite tremendous advances in cardiovascular care, morbidity and mortality for AHF remain high, consuming billions of health care dollars. With the aging of the population, the incidence and prevalence of HF is projected to increase. Yet, initial treatment of AHF today is similar to 40 years ago. Multiple studies have yielded new insights regarding initial management, with regards to both treatment and strategies of care. These advances will be reviewed in the context of initial or early AHF management. There remains, however, an unmet need to improve outcomes for AHF patients.

Clinical course and predictive value of congestion during hospitalization in patients admitted for worsening signs and symptoms of heart failure with reduced ejection fraction: findings from the EVEREST trial

AIMS

Signs and symptoms of congestion are the most common cause for hospitalization for heart failure (HHF). The clinical course and prognostic value of congestion during HHF has not been systemically characterized.

METHODS AND RESULTS

A post hoc analysis was performed of the placebo group (n = 2061) of the EVEREST trial, which enrolled patients within 48 h of admission (median ~24 h) for worsening HF with an EF ≤ 40% and two or more signs or symptoms of fluid overload [dyspnoea, oedema, or jugular venous distension (JVD)] for a median follow-up of 9.9 months. Clinician-investigators assessed patients daily for dyspnoea, orthopnoea, fatigue, rales, pedal oedema, and JVD and rated signs and symptoms on a standardized 4-point scale ranging from 0 to 3. A modified composite congestion score (CCS) was calculated by summing the individual scores for orthopnoea, JVD, and pedal oedema. Endpoints were HHF, all-cause mortality (ACM), and ACM + HHF. Multivariable Cox regression models were used to evaluate the risk of CCS at discharge on outcomes at 30 days and for the entire follow-up period. The mean CCS obtained after initial therapy decreased from the mean ± SD of 4.07 ± 1.84 and the median (25th, 75th) of 4 (3, 5) at baseline to 1.11 ± 1.42 and 1 (0, 2) at discharge. At discharge, nearly three-quarters of study participants had a CCS of 0 or 1 and fewer than 10% of patients had a CCS >3. B-type natriuretic peptide (BNP) and amino terminal-proBNP, respectively, decreased from 734 (313, 1523) pg/mL and 4857 (2251, 9642) pg/mL at baseline to 477 (199, 1079) pg/mL, and 2834 (1218, 6075) pg/mL at discharge/Day 7. A CCS at discharge was associated with increased risk (HR/point CCS, 95% CI) for a subset of endpoints at 30 days (HHF: 1.06, 0.95-1.19; ACM: 1.34, 1.14-1.58; and ACM + HHF: 1.13, 1.03-1.25) and all outcomes for the overall study period (HHF: 1.07, 1.01-1.14; ACM: 1.16, 1.09-1.24; and ACM + HHF 1.11, 1.06-1.17). Patients with a CCS of 0 at discharge experienced HHF of 26.2% and ACM of 19.1% during the follow-up.

CONCLUSION

Among patients admitted for worsening signs and symptoms of HF and reduced EF, congestion improves substantially during hospitalization in response to standard therapy alone. However, patients with absent or minimal resting signs and symptoms at discharge still experienced a high mortality and readmission rate.

The preparation of a new self-made microbubble-loading urokinase and its thrombolysis combined with low-frequency ultrasound in vitro

Urokinase (uPA) is used widely for thrombosis therapy in the clinic. However, ways to minimize its adverse effect of hemorrhage are still being studied. As a new technique for the local delivery of genes and drugs, ultrasound (US) contrast agents, microbubbles (MBs), have been mentioned. The purpose of this study is to explore a more efficacious and safer thrombolytic method by preparing three groups of self-made microbubble-loading uPA (uPA-MBs) (1 uPA-MBs, 5 uPA-MBs and 10 uPA-MBs) using freeze-drying methods and measuring their thrombolysis when combined in vitro with low-frequency US. The results showed the mean concentration, mean diameter, pH value and encapsulation efficiency of uPA of the three groups of uPA-MBs were approximately 2.08-2.82 × 10(8)/mL, ∼3.13 μm, 6.89-6.99 and from (78.08% ± 0.57%) to (57.23% ± 0.94%), respectively. Under US exposure, the loaded uPA demonstrated bioactivity by agarose fibrin plate and in vitro thrombolysis of the three uPA-MBs also showed higher effects than in the group of those who received uPA-MBs alone, the control group or the US group. In conclusion, the physiochemical properties of these self-made uPA-MBs are suitable for intravenous administration but 1 uPA-MB and 5 uPA-MBs are better than 10 uPA-MBs. uPA-MBs combined with US can decrease the in vitro dosage of uPA for thrombolysis.

Focused in vivo delivery of plasmid DNA to the porcine vascular wall via intravascular ultrasound destruction of microbubbles

BACKGROUND

Safety concerns associated with drug-eluting stents have spurred interest in alternative vessel therapeutics following angioplasty. Microbubble contrast agents have been shown to increase gene transfection in vivo in the presence of ultrasound.

OBJECTIVES/METHODS

The purpose of this study was to determine whether an intravascular ultrasound (IVUS) catheter could mediate plasmid DNA transfection from microbubble carriers to the porcine coronary artery wall following balloon angioplasty.

RESULTS

In the presence of plasmid-coupled microbubbles in vitro only cells exposed to ultrasound from the modified IVUS catheter significantly expressed the transgene. A porcine left anterior descending coronary artery underwent balloon angioplasty followed by injection and insonation of microbubbles from the IVUS catheter at the site of angioplasty. After 3 days, an approximately 6.5-fold increase in transgene expression was observed in arteries that received microbubbles and IVUS compared to those that received microbubbles with no IVUS.

CONCLUSIONS

The results of this study demonstrate for the first time that IVUS is required to enhance gene transfection from microbubble carriers to the vessel wall in vivo. This technology may be applied to both drug and gene therapy to reduce vessel restenosis.

Ultrasonic gene and drug delivery to the cardiovascular system

Ultrasound targeted microbubble destruction has evolved as a promising tool for organ specific gene and drug delivery. This technique has initially been developed as a method in myocardial contrast echocardiography, destroying intramyocardial microbubbles to characterize refill kinetics. When loading similar microbubbles with a bioactive substance, ultrasonic destruction of microbubbles may release the transported substance in the targeted organ. Furthermore, high amplitude oscillations of microbubbles lead to increased capillary and cell membrane permeability, thus facilitating tissue and cell penetration of the released substance. While this technique has been successfully used in many organs, its application in the cardiovascular system has dominated so far. Drug delivery using microbubbles has played a minor role in the cardiovascular system. In contrast, gene transfer has been successfully achieved in many studies. Both viral and non-viral vectors were used for loading on microbubbles. This review article will give an overview on studies that have applied ultrasound targeted microbubble destruction to deliver substances in the heart and blood vessels. It will show potential therapeutic targets, especially for gene therapy, describe feasible substances that can be loaded on microbubbles, and critically discuss prospects and limitations of this technique.

Encapsulated ultrasound microbubbles: Therapeutic application in drug/gene delivery

Encapsulated gas microbubbles are well known as ultrasound contrast agents for medical ultrasound imaging. Nonetheless, not only do these microbubbles help to image, but they can also be used as drug/gene carriers. The microbubbles as drug/gene carriers have an average size less than that of red blood cells, i.e. they are capable of penetrating even into the small blood capillaries and releasing drug and genes under the action of ultrasound field. The application of ultrasound and microbubbles to targeted drug and gene delivery has been the subject of intense experimental research. Under exposure of sufficiently high-amplitude ultrasound, these targeted microbubbles would rupture, spewing drugs or genes, which are contained in its encapsulating layer, to targeted cells or tissues. Recently, targeting ligands are attached to the surface of the microbubbles (i.e. targeted-microbubbles), which have been widely used in cardiovascular system and tumor diagnosis and therapy. In this paper, the characterization of novel targeted ultrasonic contrast agents or microbubbles and their potential applications in drug delivery or gene therapy are reviewed.