Ultrasound-targeted microbubble destruction: toward a new strategy for diabetes treatment

Ultrasound-induced biophysical effects in controlled drug delivery

Ultrasound is widely used in biomedical engineering and has applications in conventional diagnosis and drug delivery. Recent advances in ultrasound-induced drug delivery have been summarized previously in several reviews that have primarily focused on the fabrication of drug delivery carriers. This review discusses the mechanisms underlying ultrasound-induced drug delivery and factors affecting delivery efficiency, including the characteristics of drug delivery carriers and ultrasound parameters. Firstly, biophysical effects induced by ultrasound, namely thermal effects, cavitation effects, and acoustic radiation forces, are illustrated. Secondly, the use of these biophysical effects to enhance drug delivery by affecting drug carriers and corresponding tissues is clarified in detail. Thirdly, recent advances in ultrasound-triggered drug delivery are detailed. Safety issues and optimization strategies to improve therapeutic outcomes and reduce side effects are summarized. Finally, current progress and future directions are discussed.

Recent ultrasound advancements for the manipulation of nanobiomaterials and nanoformulations for drug delivery

Recent advances in ultrasound (US) have shown its great potential in biomedical applications as diagnostic and therapeutic tools. The coupling of US-assisted drug delivery systems with nanobiomaterials possessing tailor-made functions has been shown to remove the limitations of conventional drug delivery systems. The low-frequency US has significantly enhanced the targeted drug delivery effect and efficacy, reducing limitations posed by conventional treatments such as a limited therapeutic window. The acoustic cavitation effect induced by the US-mediated microbubbles (MBs) has been reported to replace drugs in certain acute diseases such as ischemic stroke. This review briefly discusses the US principles, with particular attention to the recent advancements in drug delivery applications. Furthermore, US-assisted drug delivery coupled with nanobiomaterials to treat different diseases (cancer, neurodegenerative disease, diabetes, thrombosis, and COVID-19) are discussed in detail. Finally, this review covers the future perspectives and challenges on the applications of US-mediated nanobiomaterials.

Ultrasound-targeted microbubble destruction augmented synergistic therapy of rheumatoid arthritis via targeted liposomes

Rheumatoid arthritis (RA) can lead to joint destruction and deformity, which is a significant cause of the loss of the young and middle-aged labor force. However, the treatment of RA is still filled with challenges. Though dexamethasone, one of the glucocorticoids, is commonly used in the treatment of RA, its clinical use is limited because of the required high-dose and long-term use, unsatisfactory therapeutic effects, and various side-effects. Ultrasound-targeted microbubble destruction (UTMD) can augment the ultrasonic cavitation effects and trigger drug release from targeted nanocarriers in the synovial cavity, which makes it a more effective synergistic treatment strategy for RA. In this work, we aim to utilize the UTMD effect to augment the synergistic therapy of RA by using polyethylene glycol (PEG)-modified folate (FA)-conjugated liposomes (LPs) loaded with dexamethasone sodium phosphate (DexSP) (DexSP@LPs-PEG-FA). The UTMD-mediated DexSP@LPs-PEG-FA for targeted delivery of DexSP including a synergistic ultrasonic cavitation effect and drug therapy were investigated through in vitro RAW264.7 cell experiments and in vivo collagen-induced arthritis SD rat model animal experiments. The results show the DexSP release from targeted liposomes was improved under the UTMD effect. Likewise, the folate-conjugated liposomes displayed targeting association to RAW264.7 cells. Together with the application of ultrasound and microbubbles, liposomes-delivered DexSP potently reduced joints swelling, bone erosion, and inflammation in both joints and serum with a low dose. These results demonstrated that UTMD-mediated folate-conjugated liposomes are not only a promising method for targeted synergistic treatment of RA but also may show high potential for serving as nanomedicines for many other biomedical fields.

Gold nanoparticle-mediated bubbles in cancer nanotechnology

Microbubbles (MBs) have been extensively investigated in the field of biomedicine for the past few decades. Ultrasound and laser are the most frequently used sources of energy to produce MBs. Traditional acoustic methods induce MBs with poor localized areas of action. A high energy level is required to generate MBs through the focused continuous laser, which can be harmful to healthy tissues. As an alternative, plasmonic light-responsive nanoparticles, such as gold nanoparticles (AuNPs), are preferably used with continuous laser to decrease the energy threshold and reduce the bubbles area of action. It is also well-known that the utilization of the pulsed lasers instead of the continuous lasers decreases the needed AuNPs doses as well as laser power threshold. When well-confined bubbles are generated in biological environments, they play their own unique mechanical and optical roles. The collapse of a bubble can mechanically affect its surrounding area. Such a capability can be used for cargo delivery to cancer cells and cell surgery, destruction, and transfection. Moreover, the excellent ability of light scattering makes the bubbles suitable for cancer imaging. This review firstly provides an overview of the fundamental aspects of AuNPs-mediated bubbles and then their emerging applications in the field of cancer nanotechnology will be reviewed. Although the pre-clinical studies on the AuNP-mediated bubbles have shown promising data, it seems that this technique would not be applicable to every kind of cancer. The clinical application of this technique may basically be limited to the good accessible lesions like the superficial, intracavity and intraluminal tumors. The other essential challenges against the clinical translation of AuNP-mediated bubbles are also discussed.

Cell-penetrating Peptide-modified Targeted Drug-loaded Phase-transformation Lipid Nanoparticles Combined with Low-intensity Focused Ultrasound for Precision Theranostics against Hepatocellular Carcinoma

Objective: Prepare a multifunctional ultrasound molecular probe, hyaluronic acid-mediated cell-penetrating peptide-modified 10-hydroxycamptothecin-loaded phase-transformation lipid nanoparticles (HA/CPPs-10-HCPT-NPs), and to combine HA/CPPs-10-HCPT-NPs with low-intensity focused ultrasound (LIFU) for precision theranostics against hepatocellular carcinoma (HCC).

Methods: HA/CPPs-10-HCPT-NPs were prepared using thin-film dispersion, ultrasound emulsification, and electrostatic effects. HA/CPPs-10-HCPT-NPs were characterized for particle size, zeta potential, encapsulation efficiency and drug-loading efficiency. In vitro, HA/CPPs-10-HCPT-NPs were tested for acoustic droplet vaporization (ADV) at different time points/acoustic intensities; the ability of HA/CPPs-10-HCPT-NPs to target SMMC-7721 cells was detected by confocal laser scanning microscopy (CLSM); the penetrating ability of CG-TAT-GC-modified NPs was verified by CLSM in a 3D multicellular tumor spheroid (MCTS) model; the effect of HA/CPPs-10-HCPT-NPs combined with LIFU on killing SMMC-7721 cells was measured by CCK-8 and flow cytometry. In vivo, the tumor-target efficiency of HA/CPPs-10-HCPT-NPs was evaluated by a small-animal fluorescence imaging system and CLSM; the enhanced ultrasound imaging efficiency of HA/CPPs-10-HCPT-NPs combined with LIFU was measured by an ultrasound imaging analyzer; the therapeutic effect of HA/CPPs-10-HCPT-NPs combined with LIFU was evaluated by tumor volume, tumor inhibition rate, and staining (hematoxylin and eosin (H & E), proliferating cell nuclear antigen (PCNA) and TUNEL).

Results: Mean particle size and mean zeta potential of HA/CPPs-10-HCPT-NPs were 284.2±13.3 nm and - 16.55±1.50 mV, respectively. HA/CPPs-10-HCPT-NPs could bind to SMMC-7721 cells more readily than CPPs-10-HCPT-NPs. Penetration depth into 3D MCTS of HA/CPPs-10-HCPT-NPs was 2.76-fold larger than that of NPs without CG-TAT-GC. HA/CPPs-10-HCPT-NPs could enhance ultrasound imaging by undergoing ADV triggered by LIFU. HA/CPPs-10-HCPT-NPs+LIFU group demonstrated significantly higher efficiency of anti-proliferation and apoptosis percentage than all other groups. In mouse liver tumor xenografts, HA/CPPs-10-HCPT-NPs could target tumor sites and enhance ultrasound imaging under LIFU. HA/CPPs-10-HCPT-NPs+LIFU group had a significantly smaller tumor volume, lower proliferative index (PI), and higher tumor inhibition and apoptotic index (AI) than all other groups.

Conclusions: Combined application of HA/CPPs-10-HCPT-NPs and LIFU should be a valuable and promising strategy for precise HCC theranostics.

The use of 5-fluorouracil-loaded nanobubbles combined with low-frequency ultrasound to treat hepatocellular carcinoma in nude mice

OBJECTIVE

This study aimed to investigate the therapeutic effects of 5-fluorouracil (5-FU)-loaded nanobubbles irradiated with low-intensity, low-frequency ultrasound in nude mice with hepatocellular carcinoma (HCC).

METHODS

A transplanted tumor model of HCC in nude mice was established in 40 mice, which were then randomly divided equally into four groups: group A (saline), group B (5-FU-loaded nanobubbles), group C (5-FU-loaded nanobubbles with non-low-frequency ultrasound), and group D (5-FU-loaded nanobubbles with low-frequency ultrasound). The tumor size in each mouse was observed via ultrasound before and after the treatments. Inhibition of the tumor growth in each group was compared, and survival curves were generated. Tumor tissues were removed to determine the apoptotic index using the TUNEL method and quantitative analysis. Tumor tissues with CD34-positive microvessels were observed by immunohistochemistry, and the tumor microvessel densities were calculated.

RESULTS

The growth rate of the tumor volumes in group D was significantly slower than that in the other groups, while the tumor inhibition rates and apoptotic index in group D were significantly higher than those of the other groups. The number of microvessels staining positive for CD34 was decreased in group D. Therefore, group D presented the most significant inhibitory effects.

CONCLUSIONS

Therefore, 5-FU-loaded nanobubbles subjected to irradiation with low-frequency ultrasound could further improve drug targeting and effectively inhibit the growth of transplanted tumors, which is expected to become an ideal drug carrier and targeted drug delivery system for the treatment of HCC in the future.

Low-intensity focused ultrasound (LIFU)-induced acoustic droplet vaporization in phase-transition perfluoropentane nanodroplets modified by folate for ultrasound molecular imaging

The commonly used ultrasound (US) molecular probes, such as targeted microbubbles and perfluorocarbon emulsions, present a number of inherent problems including the conflict between US visualization and particle penetration. This study describes the successful fabrication of phase changeable folate-targeted perfluoropentane nanodroplets (termed FA-NDs), a novel US molecular probe for tumor molecular imaging with US. Notably, these FA-NDs can be triggered by low-intensity focused US (LIFU) sonication, providing excellent US enhancement in B-mode and contrast-enhanced US mode in vitro. After intravenous administration into nude mice bearing SKOV3 ovarian carcinomas, 1,1′-dioctadecyl-3,3,3′,3′ -tetramethylindotricarbocya-nine iodide-labeled FA-NDs were found to accumulate in the tumor region. FA-NDs injection followed by LIFU sonication exhibited remarkable US contrast enhancement in the tumor region. In conclusion, combining our elaborately developed FA-NDs with LIFU sonication provides a potential protocol for US molecular imaging in folate receptor-overexpressing tumors.