A drug-perfluorocarbon nanoemulsion with an ultrathin silica coating for the synergistic effect of chemotherapy and ablation by high-intensity focused ultrasound

A Retrospective Case Series Of High-Intensity Focused Ultrasound (HIFU) In Combination With Gemcitabine And Oxaliplatin (Gemox) On Treating Elderly Middle And Advanced Pancreatic Cancer

Purpose

This retrospective study was conducted to evaluate the safety and efficacy of high-intensity focused ultrasound (HIFU) ablation combined with Gemcitabine and Oxaliplatin (Gemox) for the treatment of middle and advanced pancreatic cancer in elderly patients.

Methods

Forty-seven patients with pancreatic cancer treated with HIFU and Gemox were evaluated for inclusion, and 38 cases were finally included. The primary endpoint was safety. Secondary endpoints included the response rate, the clinical benefit response (CBR), overall survival (OS), progression-free survival (PFS).

Results

After combination therapy of HIFU and Gemox, severe complications were rarely reported, and no treatment-related death occurred. The rate of three or four-degree myelosuppression was low, and no obvious impairment of hepatorenal function was observed. Pancreatitis and gastrointestinal injury did not occurred. The disease control rate (DCR) was estimated to be 76.3%, including complete remission (CR), partial remission (PR), stable disease (SD) in 1, 6, 22 cases, respectively. And the objective response rate (ORR) was 18.4%. The clinical benefit rate (CBR) was 68.4%, with the pain significantly relieved (P<0.01). The serum level of CA19-9 showed significant changes after HIFU treatment. The median overall survival (OS) was 12.5 months, with a 6-month and 12-month OS rate of 82.13% and 59.34%, respectively. Stratified analyses did not reveal any significant difference between patients in different stages.

Conclusion

Elderly patients (≥ 60 years old) with pancreatic cancer would experience tolerable toxicity and obtain good clinical benefits from the combination therapy of HIFU ablation and Gemox.

Use of Perfluorocarbon based Blood Substitute Perftoran in Correction of Hypoxia During Acute Anemia in Animals

The cause of acute and severe hypoxia of the organism is acute posthemorrhagic anemia. To eliminate posthemorrhagic anemia in animals, the perfluorocarbon blood substitute Perftoran (Russia) with a gas-transporting function was used. The aim of this study was to determine the clinical effectiveness of the perfluorocarbon based blood substitute Perftoran with a gas-carrying function in acute posthemorrhagic anemia in animals and reveal possible side effect of the blood substitute and remove them. In the study conducted in the Clinic of Veterinary Medicine of Pushchino Research Center (Russia) participated 20 cats of both sexes, who were admitted with internal bleeding as a result of injuries. The animals were divided into two groups: the control and the treatment groups (10 per group). All animals with anemia were examined according to the standard scheme: anamnesis vitae and anamnesis morbi, physical examination (basic methods of research were used), additional methods that were used: complete blood count (CBC) and biochemical analysis of blood (BA), microscopy of blood smears, abdominal ultrasonography. Based on the obtained results, we can conclude that the use of the gas-carrying substitute for donor blood Perftoran in the treatment group of animals with posthemorrhagic anemia, which resulted from polytrauma, eliminated tissue hypoxia; the treatment of the animals in the control group with standard solutions (by infusing Stabisol) without gas transport correction led to the development of persistent hypoxia, which persisted to the stage of reticulocyte crisis.

Treating tumors with minimally invasive therapy: A review

With high level of morbidity and mortality, tumor is one of the deadliest diseases worldwide. Aiming to tackle tumor, researchers have developed a lot of strategies. Among these strategies, the minimally invasive therapy (MIT) is very promising, for its capability of targeting tumor cells and resulting in a small incision or no incisions. In this review, we will first illustrate some mechanisms and characteristics of tumor metastasis from the primary tumor to the secondary tumor foci. Then, we will briefly introduce the history, characteristics, and advantages of some of the MITs. Finally, emphasis will be, respectively, focused on an overview of the state-of-the-art of the HIFU-, PDT-, PTT-and SDT-based anti-tumor strategies on each stage of tumor metastasis.

A Responsive Mesoporous Silica Nanoparticle Platform for Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound-Stimulated Cargo Delivery with Controllable Location, Time, and Dose

Magnetic resonance imaging (MRI) is an essential modality for clinical diagnosis, and MRI-guided high-intensity focused ultrasound (MRgHIFU) is a powerful technology for targeted therapy. Clinical applications of MRgHIFU primarily utilize hyperthermia and ablation to treat cancerous tissue, but for drug delivery applications thermal damage is undesirable. A biofriendly MRgHIFU-responsive mesoporous silica nanoparticle (MSN) platform that is stimulated within a physiological safe temperature range has been developed, reducing the possibility of thermal damage to the surrounding healthy tissues. Biocompatible polyethylene glycol (PEG) was employed to cap the pores of MSNs, and the release of cargo molecules by HIFU occurs without substantial temperature increase (∼4 °C). To visualize by MRI and measure the stimulated delivery in situ, a U.S. Food and Drug Administration (FDA)-approved gadolinium-based contrast agent, gadopentetate dimeglumine (Gd(DTPA)^2-), was used as the imageable cargo. Taking advantage of the three-dimensional (3-D) imaging and targeting capabilities of MRgHIFU, the release of Gd(DTPA)^2- stimulated by HIFU was pinpointed at the HIFU focal point in 3-D space in a tissue-mimicking gel phantom. The amount of Gd(DTPA)^2- released was controlled by HIFU stimulation times and power levels. A positive correlation between the amount of Gd(DTPA)^2- released and T₁ was found. The MRgHIFU-stimulated cargo release was further imaged in a sample of ex vivo animal tissue. With this technology, the biodistribution of the nanocarriers can be tracked and the MRgHIFU-stimulated cargo release can be pinpointed, opening up an opportunity for future image-guided theranostic applications.

Gas-Mediated Cancer Bioimaging and Therapy

Gas-involving cancer theranostics have attracted considerable attention in recent years due to their high therapeutic efficacy and biosafety. We have reviewed the recent significant advances in the development of stimuli-responsive gas releasing molecules (GRMs) and gas nanogenerators for cancer bioimaging, targeted and controlled gas therapy, and gas-sensitized synergistic therapy. We have focused on gases with known anticancer effects, such as oxygen (O₂), carbon monoxide (CO), nitric oxide (NO), hydrogen sulfide (H₂S), hydrogen (H₂), sulfur dioxide (SO₂), carbon dioxide (CO₂), and heavy gases that act via the gas-generating process. The GRMs and gas nanogenerators for each gas have been described in terms of the stimulation method, followed by their applications in ultrasound and multimodal imaging, and finally their primary and synergistic actions with other cancer therapeutic modalities. The current challenges and future possibilities of gas therapy and imaging vis-à-vis clinical translation have also been discussed.

Multifunctional Nanodroplets Encapsulating Naphthalocyanine and Perfluorohexane for Bimodal Image-Guided Therapy

Although nanocarriers containing perfluorocarbon (PFC) have been widely investigated as an ultrasound (US) imaging agent and a high intensity focused ultrasound (HIFU) agent, these carriers have suffered from low stability and biocompatibility limiting their further biomedical applications. Here, we developed surface cross-linked polymer nanodroplets as a HIFU therapeutic agent guided by bimodal photoacoustic (PA) and US imaging. Pluronic F127 was reacted with 4-nitrophenyl chloroformate (NPC) and mixed with naphthalocyanine (Nc) in dichloromethane, which was added into the aqueous solution of amine-functionalized six-arm-branched poly(ethylene glycol) (PEG) to form an oil-in-water emulsion for the cross-linking reaction between the terminal NPC of Pluronic F127 and the primary amine of six-arm PEG. The resulting solution was sonicated with liquid perfluorohexane (PFH) to prepare PEG cross-linked Pluronic F127 nanoparticles encapsulating Nc and PFH (Nc/PFH@PCPN). Nc/PFH@PCPN appeared to be stable without any coalescence or vaporization in the physiological condition. Upon the application of HIFU, Nc/PFH@PCPN was vaporized and showed increased US intensity for 180 min. The Nc dye in the nanodroplets enabled the stable encapsulation of PFH and the bimodal US/PA imaging. In vivo PA/US image-guided HIFU ablation therapy confirmed that the nanodroplets increased the cavitation effect, induced necrosis and apoptosis of tumor cells, and reduced tumor growth significantly for 12 days. Taken together, the multifunctional Nc/PFH@PCPN was successfully developed as a new platform for PA/US image-guided HIFU therapy.

Review on Acoustic Droplet Vaporization in Ultrasound Diagnostics and Therapeutics

Acoustic droplet vaporization (ADV) is the physical process in which liquid undergoes phase transition to gas after exposure to a pressure amplitude above a certain threshold. In recent years, new techniques in ultrasound diagnostics and therapeutics have been developed which utilize microformulations with various physical and chemical properties. The purpose of this review is to give the reader a general idea on how ADV can be implemented for the existing biomedical applications of droplet vaporization. In this regard, the recent developments in ultrasound therapy which shed light on the ADV are considered. Modern designs of capsules and nanodroplets (NDs) are shown, and the material choices and their implications for function are discussed. The influence of the physical properties of the induced acoustic field, the surrounding medium, and thermophysical effects on the vaporization are presented. Lastly, current challenges and potential future applications towards the implementation of the therapeutic droplets are discussed.

Engineering temperature-sensitive plateletsomes as a tailored chemotherapy platform in combination with HIFU ablation for cancer treatment

Chemotherapy is widely used in combination with high-intensity focused ultrasound (HIFU) ablation for cancer therapy; however, the spatial and temporal integration of chemotherapy and HIFU ablation remains a challenge. Here, temperature-sensitive plateletsomes (TSPs) composed of platelet (PLT) membrane, 1-stearoyl-2-hydroxy-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine were developed to adequately integrate chemotherapy with HIFU tumor ablation in vivo.

Methods: The thermosensitive permeability of TSPs was evaluated under both water bath heating and HIFU hyperthermia. The targeting performance, pharmacokinetic behavior and therapeutic potential of TSPs in combination with HIFU ablation were evaluated using HeLa cells and a HeLa cell tumor-bearing nude mouse model in comparison with temperature-sensitive liposomes (TSLs).

Results: TSPs showed high drug loading efficiency and temperature-sensitive permeability. When applied in vivo, TSPs showed a circulation lifetime comparable to that of TSLs and exhibited PLT-specific cancer cell affinity and a vascular damage response. Upon HIFU hyperthermia, TSPs displayed ultrafast drug release and enhanced tumor uptake, providing high drug availability in the tumor site to cooperate with HIFU ablation. After HIFU ablation, TSPs rapidly targeted the postoperative tumor site by adhesion to the damaged tumor vasculature, leading to targeted and localized postoperative chemotherapy.

Conclusion: Due to effective integration at both intraoperative and postoperative stages, TSPs could be a promising chemotherapy nanoplatform in combination with HIFU ablation for cancer therapy.

Co-Delivery of Metformin Enhances the Antimultidrug Resistant Tumor Effect of Doxorubicin by Improving Hypoxic Tumor Microenvironment

Doxorubicin (DOX) is a first-line chemo drug for cancer therapy, yet it fails to treat multi-drug-resistant tumors. Hypoxia is a major causative factor leading to chemotherapy failure. Particularly, hypoxia up-regulates its responsive transcription factor-hypoxia-inducible factors (HIF)-to induce the overexpression of drug resistant genes. Metformin (MET) is recently found to cooperate with DOX against multiple tumors. As a mitochondrial inhibitor, MET could suppress tumor oxygen consumption, and thereby modulate the hypoxic tumor microenvironment. In this study, we used cationic liposomes to codeliver both DOX and MET for treating multi-drug-resistant breast cancer cells-MCF7/ADR. Faster release of MET enhanced the cytotoxicity of DOX through attenuating hypoxic stress both in vivo and in vitro. MET diminished the cellular oxygen consumption and inhibited HIF1α and P-glycoprotein (Pgp) expression in vitro. In addition, the dual-drug-loaded liposomes increased tumor targeting and intratumoral blood oxygen saturation, which suggested that the tumor reoxygenation effect of MET facilitated the exertion of its synergistic activity with DOX against MCF7/ADR xenografts. In general, our study represents a feasible strategy to boost the therapeutic effect in treating multi-drug-resistant cancer by improving the hypoxic tumor microenvironment.

On-Demand Detaching Nanosystem for the Spatiotemporal Control of Cancer Theranostics

Engineering multiple theranostic modalities into a single nanoscale entity holds great potential to rejuvenate cancer treatments; however, enabling the sophisticated spatiotemporal control of each component for maximizing theranostic improvement and minimizing side effects concurrently remains a challenge. Herein, an intelligent detachable "nanorocket" is developed to sequentially manipulate and optimize multitheranostic processes for magnetic resonance-assisted ultrasound-drug combined therapy (MR-HIFU-Drug). The "nanorocket" is constructed by integrating multicomponent (MnCO₃, doxorubicin, silica) on the pH-sensitive CaCO₃ nanoparticles step by step via cation exchange and controlled heterogeneous nucleation, in which doxorubicin is encapsulated in both carbonates and silica component. The "nanorocket" can initiate sequential detachment in the acidic tumor microenvironment. Specifically, carbonates decompose instantly, releasing Mn²⁺ as the MR contrast agent and leaving hollow silica nanostructure behind as the HIFU synergistic agent. Consequently, burst release of drug is also triggered, further triggering the degradation of silica, which in turn regulates the slow release of drug from the silica matrix. Thus, efficient tumor inhibition is achieved by enhanced HIFU ablation and biphase release of doxorubicin with a stepwise clearance of Mn and Si. This work establishes a system for the systematic spatiotemporal dispatch of diverse theranostic components for the balance of efficacy and safety in cancer theranostics.

Colloids, nanoparticles, and materials for imaging, delivery, ablation, and theranostics by focused ultrasound (FUS)

This review focuses on different materials and contrast agents that sensitize imaging and therapy with Focused Ultrasound (FUS). At high intensities, FUS is capable of selectively ablating tissue with focus on the millimeter scale, presenting an alternative to surgical intervention or management of malignant growth. At low intensities, FUS can be also used for other medical applications such as local delivery of drugs and blood brain barrier opening (BBBO). Contrast agents offer an opportunity to increase selective acoustic absorption or facilitate destructive cavitation processes by converting incident acoustic energy into thermal and mechanical energy. First, we review the history of FUS and its effects on living tissue. Next, we present different colloidal or nanoparticulate approaches to sensitizing FUS, for example using microbubbles, phase-shift emulsions, hollow-shelled nanoparticles, or hydrophobic silica surfaces. Exploring the science behind these interactions, we also discuss ways to make stimulus-responsive, or "turn-on" contrast agents for improved selectivity. Finally, we discuss acoustically-active hydrogels and membranes. This review will be of interest to those working in materials who wish to explore new applications in acoustics and those in acoustics who are seeking new agents to improve the efficacy of their approaches.

Advances in mesoporous silica nanoparticles for targeted stimuli-responsive drug delivery: an update

INTRODUCTION

Mesoporous silica nanoparticles (MSNs) are outstanding nanoplatforms for drug delivery. Herein, the most recent advances to turn MSN-based carriers into minimal side effect drug delivery agents are covered.

AREAS COVERED

This review summarizes the scientific advances dealing with MSNs for targeted and stimuli-responsive drug delivery since 2015. Delivery aspects to diseased tissues together with approaches to obtain smart MSNs able to respond to internal or external stimuli and their applications are here described. Special emphasis is done on the combination of two or more stimuli on the same nanoplatform and on combined drug therapy.

EXPERT OPINION

The use of MSNs in nanomedicine is a promising research field because they are outstanding platforms for treating different pathologies. This is possible thanks to their structural, chemical, physical and biological properties. However, there are certain issues that should be overcome to improve the suitability of MSNs for clinical applications. All materials must be properly characterized prior to their in vivo evaluation; furthermore, preclinical in vivo studies need to be standardized to demonstrate the MSNs clinical translation potential.

Controllable Preparation of Ordered and Hierarchically Buckled Structures for Inflatable Tumor Ablation, Volumetric Strain Sensor, and Communication via Inflatable Antenna

Inflatable conducting devices providing improved properties and functionalities are needed for diverse applications. However, the difficult part in making high-performance inflatable devices is the enabling of two-dimensional (2D) buckles with controlled structures on inflatable catheters. Here, we report the fabrication of highly inflatable devices with controllable structures by wrapping the super-aligned carbon nanotube sheet (SACNS) on the pre-inflated catheter. The resulting structure exhibits unique 2D buckled structures including quasi-parallel buckles, crisscrossed buckles, and hierarchically buckled structures, which enables reversible structural changes of 7470% volumetric strain. The 2D SACNS buckled structures show stable electrical conductance and surface wettability during large strain inflation/deflation cycles. Inflatable devices including inflatable tumor ablation, capacitive volumetric strain sensor, and communication via inflatable radio frequency antenna based on these structures are demonstrated.

Energy-Converting Nanomedicine

Serious side effects to surrounding normal tissues and unsatisfactory therapeutic efficacy hamper the further clinic applications of conventional cancer-therapeutic strategies, such as chemotherapy and surgery. The fast development of nanotechnology provides unprecedented superiorities for cancer therapeutics. Externally activatable therapeutic modalities mediated by nanomaterials, relying on highly effective energy transformation to release therapeutic elements/effects (cytotoxic reactive oxygen species, thermal effect, photoelectric effect, Compton effect, cavitation effect, mechanical effect or chemotherapeutic drug) for cancer therapies, categorized and termed as "energy-converting nanomedicine," have arouse considerable concern due to their noninvasiveness, desirable tissue-penetration depth, and accurate modulation of therapeutic dose. This review summarizes the recent advances in the engineering of intelligent functional nanotherapeutics for energy-converting nanomedicine, including photo-based, radiation-based, ultrasound-based, magnetic field-based, microwave-based, electric field-based, and radiofrequency-based nanomedicines, which are enabled by external stimuli (light, radiation, ultrasound, magnetic field, microwave, electric field, and radiofrequency). Furthermore, biosafety issues of energy-converting nanomedicine related to future clinical translation are also addressed. Finally, the potential challenges and prospects of energy-converting nanomedicine for future clinical translation are discussed.

Ultrasound responsive mesoporous silica nanoparticles for biomedical applications

Nanotechnology, which has already revolutionised many technological areas, is expected to transform life sciences. In this sense, nanomedicine could address some of the most important limitations of conventional medicine. In general, nanomedicine includes three major objectives: (1) trap and protect a great amount of therapeutic agents; (2) carry them to the specific site of disease avoiding any leakage; and (3) release on-demand high local concentrations of therapeutic agents. This feature article will make special emphasis on mesoporous silica nanoparticles that release their therapeutic cargo in response to ultrasound.

Cellular Internalization-Induced Aggregation of Porous Silicon Nanoparticles for Ultrasound Imaging and Protein-Mediated Protection of Stem Cells

Nanotechnology employs multifunctional engineered materials in the nanoscale range that provides many opportunities for translational stem cell research and therapy. Here, a cell-penetrating peptide (virus-1 transactivator of transcription)-conjugated, porous silicon nanoparticle (TPSi NP) loaded with the Wnt3a protein to increase both the cell survival rate and the delivery precision of stem cell transplantation via a combinational theranostic strategy is presented. The TPSi NP with a pore size of 10.7 nm and inorganic framework enables high-efficiency loading of Wnt3a, prolongs Wnt3a release, and increases antioxidative stress activity in the labeled mesenchymal stem cells (MSCs), which are highly beneficial properties for cell protection in stem cell therapy for myocardial infarction. It is confirmed that the intracellular aggregation of TPSi NPs can highly amplify the acoustic scattering of the labeled MSCs, resulting in a 2.3-fold increase in the ultrasound (US) signal compared with that of unlabeled MSCs. The translational potential of the designed nanoagent for real-time US imaging-guided stem cell transplantation is confirmed via intramyocardial injection of labeled MSCs in a nude mouse model. It is proposed that the intracellular aggregation of protein drug-loaded TPSi NPs could be a simple but robust strategy for improving the therapeutic effect of stem cell therapy.

Exogenous Physical Irradiation on Titania Semiconductors: Materials Chemistry and Tumor-Specific Nanomedicine

Titania semiconductors can be activated by external physical triggers to produce electrons (e-) and holes (h+) pairs from the energy-band structure and subsequently induce the generation of reactive oxygen species for killing cancer cells, but the traditional ultraviolet light with potential phototoxicity and low-tissue-penetrating depth as the irradiation source significantly hinders the further in vivo broad biomedical applications. Here, the very-recent development of novel exogenous physical irradiation of titania semiconductors for tumor-specific therapies based on their unique physiochemical properties, including near infrared (NIR)-triggered photothermal hyperthermia and photodynamic therapy, X-ray/Cerenkov radiation-activated deep-seated photodynamic therapy, ultrasound-triggered sonodynamic therapy, and the intriguing synergistic therapeutic paradigms by combined exogenous physical irradiations are in focus. Most of these promising therapeutic modalities are based on the semiconductor nature of titania nanoplatforms, together with their defect modulation for photothermal hyperthermia. The biocompatibility and biosafety of these titania semiconductors are also highlighted for guaranteeing their further clinical translation. Challenges and future developments of titania-based therapeutic nanoplatforms and the corresponding developed therapeutic modalities for potential clinical translation of tumor-specific therapy are also discussed and outlooked.

Gas-Generating Nanoplatforms: Material Chemistry, Multifunctionality, and Gas Therapy

The fast advances of theranostic nanomedicine enable the rational design and construction of diverse functional nanoplatforms for versatile biomedical applications, among which gas-generating nanoplatforms (GGNs) have emerged very recently as unique theranostic nanoplatforms for broad gas therapies. Here, the recent developments of the rational design and chemical construction of versatile GGNs for efficient gas therapies by either exogenous physical triggers or endogenous disease-environment responsiveness are reviewed. These gases involve some therapeutic gases that can directly change disease status, such as oxygen (O₂ ), nitric oxide (NO), carbon monoxide (CO), hydrogen (H₂ ), hydrogen sulfide (H₂ S) and sulfur dioxide (SO₂ ), and other gases such as carbon dioxide (CO₂ ), dl-menthol (DLM), and gaseous perfluorocarbon (PFC) for supplementary assistance of the theranostic process. Abundant nanocarriers have been adopted for gas delivery into lesions, including poly(d,l-lactic-co-glycolic acid), micelles, silica/mesoporous silica, organosilica, MnO₂ , graphene, Bi₂ Se₃ , upconversion nanoparticles, CaCO₃ , etc. Especially, these GGNs have been successfully developed for versatile biomedical applications, including diagnostic imaging and therapeutic use. The biosafety issue, challenges faced, and future developments on the rational construction of GGNs are also discussed for further promotion of their clinical translation to benefit patients.

Gadolinium-doped hollow CeO2-ZrO2 nanoplatform as multifunctional MRI/CT dual-modal imaging agent and drug delivery vehicle

Developing multifunctional nanoparticle-based theranostic platform for cancer diagnosis and treatment is highly desirable, however, most of the present theranostic platforms are fabricated via complicated structure/composition design and time-consuming synthesis procedures. Herein, the multifunctional Gd/CeO2-ZrO2/DOX-PEG nanoplatform with single nano-structure was fabricated through a facile route, which possessed MR/CT dual-model imaging and chemotherapy ability. The nanoplatform not only exhibited well-defined shapes, tunable compositions and narrow size distributions, but also presented a well anti-cancer effect and MR/CT imaging ability. Therefore, the Gd/CeO2-ZrO2/DOX-PEG nanoplatform could be applied for chemotherapy as well as dual-model MR/CT imaging.

Low-intensity focused ultrasound (LIFU)-activated nanodroplets as a theranostic agent for noninvasive cancer molecular imaging and drug delivery

Theranostics is a new trend in the tumor research field, which involves the integration of diagnostic and therapeutic functions using imageable nanoparticles coupled with therapeutic drugs. Imaging-guided targeted delivery of therapeutics and diagnostics using nanocarriers hold great promise to minimize the side effects of conventional chemotherapy. Ultrasound microbubbles have been employed as theranostic agents over the last decade, which provide both real-time dynamic imaging for diagnosis and precise control for targeted tumor therapy. However, the intrinsic defects of microbubbles such as poor tissue penetration, short circulation time and instability hinder microbubble-based theranostic applications. In recent years, liquid-to-gas transitional perfluorocarbon nanoparticles have been developed as promising diagnostic and therapeutic nanoagents to solve the abovementioned problems. In this study, phase-changeable, folate-targeted perfluoropentane nanodroplets loaded with 10-hydroxycamptothecin (HCPT) and superparamagnetic Fe3O4 (denoted as FA-HCPT-Fe3O4-PFP NDs) are prepared and investigated for multimodal tumor imaging and targeted therapy. After intravenous administration into nude mice bearing SKOV3 ovarian cancer, FA-HCPT-Fe3O4-PFP NDs exhibit the ability to enhance MR and PA imaging. Furthermore, after the phase transition activated by low-intensity focused ultrasound (LIFU) sonication, FA-HCPT-Fe3O4-PFP NDs remarkably enhance US imaging at the tumor location. Meanwhile, the HCPT released from FA-HCPT-Fe3O4-PFP NDs during the liquid-to-gas transition provides a therapeutic effect on tumor cells with relatively low side effects to normal tissue. Therefore, the combination of LIFU and FA-HCPT-Fe3O4-PFPNDs presents an ideal modality for tumor-targeted theranostics.

Mesoporous Silica Nanoparticles for Dual-Mode Chemo-Sonodynamic Therapy by Low-Energy Ultrasound

Low-energy ultrasound (LEUS), exhibiting obvious advantages as a safe therapeutic strategy, would be promising for cancer therapy. We had synthesized a LEUS-responsive targeted drug delivery system based on functional mesoporous silica nanoparticle for cancer therapy. Paclitaxel (PTX) was loaded in mesoporous silica nanoparticles with a hydrophobic internal channel, and folic acid (FA) functionalized β-Cyclodextrin (β-CD) was capped on the surface of the nanoparticles (DESN), which acted as a cancer-targeting moiety and solubilizer. The existence of a hydrophobic internal channel in the DESN was beneficial to the storage of hydrophobic PTX, along with the enhancement of the cavitation effect produced by mild low-energy ultrasound (LEUS, ≤1.0 W/cm², 1 MHz). The DESN showed significantly enhanced cavitation effect, selective targeting, and achieved a rapid drug release under mild LEUS. To investigate the in vivo antitumor efficacy of the DESN upon LEUS irradiation, we established a 4T1 mammary tumor model. The DESN were confirmed to be of great biodegradability/biocompatibility. The tumor growth was significantly inhibited when the mice were treated with DESN (10 mg/kg) + LEUS with the relative tumor volume reduced to 4.72 ± 0.70 compared with the control group (V/V₀ = 17.12 ± 2.75). The DESN with LEUS represented excellent inhibiting effect on tumor cell in vivo. This work demonstrated that DESN mediating dual mode chemo-sonodynamic therapy could be triggered by extracorporeal remote control, may suggest a promising clinical application in cancer therapy.

Controlled Release With Emphasis on Ultrasound-Induced Release

Mesoporous silica nanoparticles (MSNs) represent a promising approach to be used as nanocarriers because they fulfill some basic criteria: biocompatibility, high loading capacity and possibility of easy surface modifications. As a consequence, MSNs have been employed to design sophisticated stimuli-responsive nanocarriers able to release the entrapped cargo on demand. Among those stimuli ultrasound (US) is considered as one of the most promising triggers for drug delivery systems due to the high tissue-penetrating capability and non-invasiveness. Recently, we employed US as a stimulus to control the drug release from MSNs for the first time, and found that acoustic cavitation played a key role in triggering the release. Those US-responsive MSNs were transported using cellular vehicles toward disease areas where they demonstrated their capacity to kill cancer cells when exposed to US. Light is also an excellent trigger because of the high biocompatibility and the capacity to focus to very small regions. However, its poor penetration in living tissues compromises its use in a clinical scenario. An alternative could be the use of near infrared (NIR) as trigger, as it would be described in this chapter. Other option could be the use of magnetic fields as stimulus because it can reach deep areas into the living tissue without damaging the surrounding tissues. MSNs have been combined with magnetic fields in a many different approaches and a quick overview is here provided. This chapter will show how some of these external stimuli represent a valuable tool for fighting complex diseases such as cancer.

Self-Assembled Metal-Phenolic Networks on Emulsions as Low-Fouling and pH-Responsive Particles

Interfacial self-assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self-assembly of pH-responsive metal-phenolic networks (MPNs) on the liquid-liquid interface of oil-in-water emulsions is reported. Oleic acid emulsions of 100-250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)-based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN. PEG provides a protective barrier on the emulsion phase and renders the emulsion low fouling. The MPN-coated emulsions have a similar size and dispersity, but an enhanced stability when compared with the uncoated emulsions, and exhibit a low cell association in vitro, a blood circulation half-life of ≈50 min in vivo, and are nontoxic to healthy mice. Furthermore, a model anticancer drug, doxorubicin, can be encapsulated within the emulsion phase at a high loading capacity (≈5 fg of doxorubicin per emulsion particle). The MPN coating imparts pH-responsiveness to the drug-loaded emulsions, leading to drug release at cell internalization pH and a potent cell cytotoxicity. The results highlight a straightforward strategy for the interfacial nanofabrication of pH-responsive emulsion-MPN systems with potential use in biomedical applications.

Perfluorocarbon-loaded polydopamine nanoparticles as ultrasound contrast agents

A versatile platform for the development of new ultrasound contrast agents is demonstrated through a one-pot synthesis and fluorination of submicron polydopamine (PDA-F) nanoparticles. The fluorophilicity of these particles allows loading with perfluoropentane (PFP) droplets that display strong and persistent ultrasound contrast in aqueous suspension and ex vivo tissue samples. Contrast under continuous imaging by color Doppler persists for 1 h in 135 nm PDA-F samples, even at maximum clinical imaging power (MI = 1.9). Additionally, use of a Cadence Contrast Pulse Sequence (CPS) results in a non-linear response suitable for imaging at 0.5 mg mL-1. Despite the PFP volatility and the lack of a hollow core, PDA-F particles display minimal signal loss after storage for over a week. The ability to tune size, metal-chelation, and add covalently-bound organic functionality offers myriad possibilities for extending this work to multimodal imaging, targeted delivery, and therapeutic functionality.

In Vivo Targeted, Responsive, and Synergistic Cancer Nanotheranostics by Magnetic Resonance Imaging-Guided Synergistic High-Intensity Focused Ultrasound Ablation and Chemotherapy

As one of the most representative noninvasive therapeutic modalities, high-intensity focused ultrasound (HIFU) has shown great promise for cancer therapy, but its low therapeutic efficacy and biosafety significantly hinder further extensive clinical translation and application. In this work, we report on the construction of a multifunctional theranostic nanoplatform to synergistically enhance the HIFU-therapeutic efficacy based on nanomedicine. A targeted and temperature-responsive theranostic nanoplatform (PFH/DOX@PLGA/Fe₃O₄-FA) has been designed and fabricated for efficient ultrasound/magnetic resonance dual-modality imaging-guided HIFU/chemo synergistic therapy. Especially, the folate was conjugated onto the surface of the nanoplatform for achieving active targeting to hepatoma cells by receptor-ligand interaction, which facilitates accumulation of the nanoplatforms into the tumor site. The integrated superparamagnetic iron oxide nanoparticles could generate the contrast enhancement in T₂-weighted magnetic resonance imaging. By virtue of the thermal effect as generated by HIFU, liquid-gas phase transition of perfluorohexane (PFH) in nanocomposites was induced to generate PFH microbubbles, which achieved the contrast-enhanced ultrasound imaging and significantly improved the HIFU ablation efficacy. The loaded anticancer drugs could be released from the nanocomposites in a controllable manner (both pH and HIFU responsiveness). These multifunctional nanocomposites have been demonstrated to efficiently suppress the tumor growth based on the enhanced and synergistic chemotherapy and HIFU ablation, providing an efficient theranostic nanoplatform for cancer treatment.

Size-Modulable Nanoprobe for High-Performance Ultrasound Imaging and Drug Delivery against Cancer

Among medical imaging modalities available in the clinic, ultrasonography is the most convenient, inexpensive, ionizing-radiation-free, and most common. Micrometer-size perfluorocarbon bubbles have been used as efficient contrast for intravascular ultrasonography, but they are too big for tumor penetration. Nanodroplets (250-1000 nm) encapsulating both perfluorocarbon and drug have been used as an ultrasound-triggered release drug delivery platform against cancer, but they are generally not useful as a tumor imaging agent. The present study aims to develop a type of pH-sensitive, polymersome-based, perfluorocarbon encapsulated ultrasonographic nanoprobe, capable of maintaining at 178 nm during circulation and increasing to 437 nm at the acidic tumor microenvironment. Its small size allowed efficient tumor uptake. At the tumor site, the nanoparticle swells, resulting in lowering of the vaporization threshold for the perfluorocarbon, efficient conversion of nanoprobes to echogenic nano/microbubbles for ultrasonic imaging, and eventual release of doxorubicin from the theranostic nanoprobe for deep tissue chemotherapy, triggered by irradiation with low-frequency ultrasound.

Facile Synthesis of Lipid-Perfluorocarbon Nanoemulsion Coated with Silica Shell as an Ultrasound Imaging Agent

A novel organic/inorganic hybrid nanovesicle as an ultrasound imaging agent is synthesized via facile emulsion and silica deposition methods. This nanovesicle, hyaluronate (HA)-docetaxel (DTX)/perfluoro-n-pentane (PFP)@SNC, consists of an encapsulated liquid PFP core, loaded DTX, and an HA-decorated silica shell. The HA-DTX/PFP@SNC has a narrow size distribution of 274.5 ± 3.25 nm, a negative zeta potential of -11.6 ± 0.47 mV, and an entrapment efficiency of 86.70% ± 1.42%. HA-DTX/PFP@SNC possesses an ultrasound (US)-triggered drug release and a temperature-dependent size change behavior. Compared with DTX/PFP@soybean phosphatidylcholine (SPC), which has no silica shell, the HA-DTX/PFP@SNC is more stable under various conditions. The MTT assay indicates that the blank HA-PFP@SNC vehicle has no cytotoxicity to A549 cells. Furthermore, due to the HA-mediated tumor-targeting ability, the HA-DTX/PFP@SNC shows obvious cytotoxicity to A549 cells. In vitro and in vivo US imaging results indicate that HA-DTX/PFP@SNC has a stronger and more durable echo signal than DTX/PFP@SPC. Moreover, the in vivo echo signal of HA-DTX/PFP@SNC is stronger than that of DTX/PFP@SNC due to the HA-mediated tumor targeting. Therefore, this novel organic/inorganic hybrid vesicle is a US contrast agent candidate.

Small PLGA nanocapsules Co-encapsulating copper sulfide nanodots and fluorocarbon compound for photoacoustic imaging-guided HIFU synergistic therapy

High intensity focused ultrasound (HIFU), as a promising and minimally invasive therapeutic modality against various solid tumors, has received considerable attention in the biomedical field. However, both the accuracy and efficacy of this technique are currently unsatisfactory. Herein, a nanometer-sized organic/inorganic hybrid enhancement agent for photoacoustic imaging (PAI)-guided HIFU therapy was designed and fabricated by concurrently encapsulating both Cu_2−xS nanodots (NDs) and perfluorooctyl bromide (PFOB) into a poly(lactic-co-glycolic acid) PLGA nanocapsule (denoted CPPNs). These nanocapsules assumed a unique core/satellite/shell sandwich structure, and combined the merits of small and uniform particle size (about 120 nm), favorable biosafety, and multifunctional theranostic ability into one system. The high performance of Cu_2−xS NDs in the absorption and conversion of near infrared laser confers high PAI contrast capability to the CPPNs, by which the location of the CPPNs within a tumor can be monitored successfully under PAI. Furthermore, our in vitro and in vivo results confirmed that the encapsulated PFOB in CPPNs increased the cavitation effect and thus enhanced the ablation efficacy under HIFU exposure. CPPNs show great potential as an efficient and powerful theranostic agent for future PAI-guided HIFU synergistic therapy.

A nanometer-sized inor-ganic/organic hybrid enhancement agent is constructed for photoacoustic imaging-guided high intensity focused ultrasound therapy.

Erythrocyte-Membrane-Coated Prussian Blue/Manganese Dioxide Nanoparticles as H2O2-Responsive Oxygen Generators To Enhance Cancer Chemotherapy/Photothermal Therapy

Because of the nontargeting release of anticancer drugs, conventional chemotherapy results in serious side effects and poor therapeutic outcomes. In addition, hypoxia situation in the tumor microenvironment also promotes the growth and metastasis of tumors. Multifunctional nanocarriers with stimuli-activation and hypoxia-relieving properties can help overcome some of these limitations. In this study, we have constructed a nanocarrier which is named PBMn-DOX@RBC. A Prussian blue/manganese dioxide (PBMn) nanoparticle is used as an oxygen precursor or catalyzer for H₂O₂ activation, and a red blood cell (RBC) membrane is used to increase the loading capacity of doxorubicin (DOX) and prolong the circulation time in vivo. H₂O₂ is overproduced in tumor tissues and tumor cells. It can be used as a stimulus to activate drug release. In the presence of H₂O₂, the hypoxia inside the tumors is relieved by the administration of PBMn-DOX@RBC. The generated oxygen disrupts the RBC coated on the surface of PBMn, which accelerates the release of DOX. RBCs also prolong the circulation time of the nanometer system in vivo. By combining the photothermal therapy (PTT) and chemotherapy, the tumor growth inhibition mediated by PBMn-DOX@RBC is further enhanced. PBMn-DOX@RBC fulfills the demands to relieve tumor hypoxia and enhance cancer chemotherapy/PTT.

Mesoporous composite nanoparticles for dual-modality ultrasound/magnetic resonance imaging and synergistic chemo-/thermotherapy against deep tumors

High-intensity focused ultrasound (HIFU) is a promising and noninvasive treatment for solid tumors, which has been explored for potential clinical applications. However, the clinical applications of HIFU for large and deep tumors such as hepatocellular carcinoma (HCC) are severely limited by unsatisfactory imaging guidance, long therapeutic times, and damage to normal tissue around the tumor due to the high power applied. In this study, we developed doxorubicin/perfluorohexane-encapsulated hollow mesoporous Prussian blue nanoparticles (HMPBs-DOX/PFH) as theranostic agents, which can effectively guide HIFU therapy and enhance its therapeutic effects in combination with chemotherapy, by decreasing the cavitation threshold. We investigated the effects of this agent on ultrasound and magnetic resonance imaging in vitro and in vivo. In addition, we showed a highly efficient HIFU therapeutic effect against HCC tumors, as well as controlled drug release, owing to the phase-transitional performance of the PFH. We therefore conclude that HMPB-DOX/PFH is a safe and efficient nanoplatform, which holds significant promise for cancer theranostics against deep tumors in clinical settings.

Endogenous Catalytic Generation of O2 Bubbles for In Situ Ultrasound-Guided High Intensity Focused Ultrasound Ablation

High intensity focused ultrasound (HIFU) surgery generally suffers from poor precision and low efficiency in clinical application, especially for cancer therapy. Herein, a multiscale hybrid catalytic nanoreactor (catalase@MONs, abbreviated as C@M) has been developed as a tumor-sensitive contrast and synergistic agent (C&SA) for ultrasound-guided HIFU cancer surgery, by integrating dendritic-structured mesoporous organosilica nanoparticles (MONs) and catalase immobilized in the large open pore channels of MONs. Such a hybrid nanoreactor exhibited sensitive catalytic activity toward H₂O₂, facilitating the continuous O₂ gas generation in a relatively mild manner even if incubated with 10 μM H₂O₂, which finally led to enhanced ablation in the tissue-mimicking PAA gel model after HIFU exposure mainly resulting from intensified cavitation effect. The C@M nanoparticles could be accumulated within the H₂O₂-enriched tumor region through enhanced permeability and retention effect, enabling durable contrast enhancement of ultrasound imaging, and highly efficient tumor ablation under relatively low power of HIFU exposure in vivo. Very different from the traditional perfluorocarbon-based C&SA, such an on-demand catalytic nanoreactor could realize the accurate positioning of tumor without HIFU prestimulation and efficient HIFU ablation with a much safer power output, which is highly desired in clinical HIFU application.

On-Demand Drug Release from Dual-Targeting Small Nanoparticles Triggered by High-Intensity Focused Ultrasound Enhanced Glioblastoma-Targeting Therapy

Glioblastoma is one of the most challenging and intractable tumors with the difficult treatment and poor prognosis. Unsatisfactory traditional systemic chemotherapies for glioblastoma are mainly attributed to the insufficient and nonspecific drug delivery into the brain tumors as well as the incomplete drug release at the tumor sites. Inspired by the facts that angiopep-2 peptide is an acknowledged dual-targeting moiety for brain tumor-targeting delivery and high-intensity focused ultrasound (HIFU) is an ideal trigger for drug release with an ultrahigh energy and millimeter-sized focus ability, in the present study, a novel HIFU-responsive angiopep-2-modified small poly(lactic-co-glycolic acid) (PLGA) hybrid nanoparticle (NP) drug delivery system holding doxorubicin/perfluorooctyl bromide (ANP-D/P) was designed to increase the intratumoral drug accumulation, further trigger on-demand drug release at the glioblastoma sites, and enhance glioblastoma therapy. It was shown that the ANP-D/P was stable and had a small size of 41 nm. The angiopep-2 modification endowed the ANP-D/P with improved blood-brain barrier transportation and specific accumulation in glioblastoma tissues by 17 folds and 13.4 folds compared with unmodified NPs, respectively. Under HIFU irradiation, the ANP-D/P could release 47% of the drug within 2 min and induce the apoptosis of most tumor cells. HIFU-triggered instantaneous drug release at the glioblastoma sites eventually enabled the ANP-D/P to achieve the strongest antiglioblastoma efficacy with the longest median survival time (56 days) of glioblastoma-bearing mice and the minimum vestiges of tumor cells in the pathological slices among all groups. In conclusion, the HIFU-responsive ANP-D/P in this study provided a new way for glioblastoma therapy with a great potential for clinical applications.

Phospholipid Capped Mesoporous Nanoparticles for Targeted High Intensity Focused Ultrasound Ablation

The mechanical effects of cavitation can be effective for therapy but difficult to control, thus potentially leading to off-target side effects in patients. While administration of ultrasound active agents such as fluorocarbon microbubbles and nanodroplets can locally enhance the effects of high intensity focused ultrasound (HIFU), it has been challenging to prepare ultrasound active agents that are small and stable enough to accumulate in tumors and internalize into cancer cells. Here, this paper reports the synthesis of 100 nm nanoparticle ultrasound agents based on phospholipid-coated, mesoporous, hydrophobically functionalized silica nanoparticles that can internalize into cancer cells and remain acoustically active. The ultrasound agents produce bubbles when subjected to short HIFU pulses (≈6 µs) with peak negative pressure as low as ≈7 MPa and at particle concentrations down to 12.5 µg mL-1 (7 × 109 particles mL-1 ). Importantly, ultrasound agents are effectively uptaken by cancer cells without cytotoxic effects, but HIFU insonation causes destruction of the cells by the acoustically generated bubbles, as demonstrated by (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and lactate dehydrogenase assays and flow cytometry. Finally, it is showed that the HIFU dose required to effectively eliminate cancer cells in the presence of ultrasound agents causes only a small temperature increase of ≈3.5 °C.

Construction of Silica-Based Micro/Nanoplatforms for Ultrasound Theranostic Biomedicine

Ultrasound (US)-based biomedicine has been extensively explored for its applications in both diagnostic imaging and disease therapy. The fast development of theranostic nanomedicine significantly promotes the development of US-based biomedicine. This progress report summarizes and discusses the recent developments of rational design and fabrication of silica-based micro/nanoparticles for versatile US-based biomedical applications. The synthetic strategies and surface-engineering approaches of silica-based micro/nanoparticles are initially discussed, followed by detailed introduction on their US-based theranostic applications. They have been extensively explored in contrast-enhanced US imaging, US-based multi-modality imaging, synergistic high-intensity focused US (HIFU) ablation, sonosensitizer-enhanced sonodynamic therapy (SDT), as well as US-triggered chemotherapy. Their biological effects and biosafety have been briefly discussed to guarantee further clinical translation. Based on the high biocompatibility, versatile composition/structure and high performance in US-based theranostic biomedicine, these silica-based theranostic agents are expected to pave a new way for achieving efficient US-based theranostics of disease by taking the specific advantages of material science, nanotechnology and US-based biomedicine.

Nanomedicine for prostate cancer using nanoemulsion: A review

Prostate cancer (PCa) is a worldwide issue, with burgeoning rise in prevalence, morbidity and mortality. Targeted drug delivery, a long sort solution in this regard using controlled release (CR) - nanocarriers, is still a challenge. There is an emerging criticism that, the challenges are due to less appreciation for the biological barriers and lack of corresponding newer technologies. Over the years, more understanding about the biological barriers has come with the progress in characterization techniques. Correspondingly, there is a change in opinion about approaches in clinical trial that; focus of the end point need to be shifted towards disease stabilization for these explorative technologies. Currently, there is a requirement to overcome these newly identified challenges to develop newer affordable therapeutics. The ongoing clinical protocol for therapy using CR-nanocarriers is intravenous injection followed by local targeting to cancer site. This is the most accepted protocol and new CR-nanocarriers are being developed to suit this protocol. In this review, recent progress in treatment of PCa using CR-nanocarriers is analyzed with respect to newly identified biological barriers and design challenges. Possibilities of exploring nanoemulsion (NE) platform for targeted drug delivery to PCa are examined. Repurposing of drugs and combination therapy using NE platform targeted to PCa can be explored for design and development of affordable nanomedicine. In 20yrs. from now there expected to be numerous affordable nanomedicine technologies available in market exploring these lines.

Polylactic acid nano- and microchamber arrays for encapsulation of small hydrophilic molecules featuring drug release via high intensity focused ultrasound

Long term encapsulation combined with spatiotemporal release for a precisely defined quantity of small hydrophilic molecules on demand remains a challenge in various fields ranging from medical drug delivery, controlled release of catalysts to industrial anti-corrosion systems. Free-standing individually sealed polylactic acid (PLA) nano- and microchamber arrays were produced by one-step dip-coating a PDMS stamp into PLA solution for 5 s followed by drying under ambient conditions. The wall thickness of these hydrophobic nano-microchambers is tunable from 150 nm to 7 μm by varying the PLA solution concentration. Furthermore, small hydrophilic molecules were successfully in situ precipitated within individual microchambers in the course of solvent evaporation after sonicating the PLA@PDMS stamp to remove air-bubbles and to load the active substance containing solvent. The cargo capacity of single chambers was determined to be in the range of several picograms, while it amounts to several micrograms per cm². Two different methods for sealing chambers were compared: microcontact printing versus dip-coating whereby microcontact printing onto a flat PLA sheet allows for entrapment of micro-air-bubbles enabling microchambers with both ultrasound responsiveness and reduced permeability. Cargo release triggered by external high intensity focused ultrasound (HIFU) stimuli is demonstrated by experiment and compared with numerical simulations.

Progress in Nanotheranostics Based on Mesoporous Silica Nanomaterial Platforms

Theranostics based on nanoparticles (NPs) is a promising paradigm in nanomedicine. Mesoporous silica nanoparticle (MSN)-based systems offer unique characteristics to enable multimodal imaging or simultaneous diagnosis and therapy. They include large surface area and volume, tunable pore size, functionalizable surface, and acceptable biological safety. Hybridization with other NPs and chemical modification can further potentiate the multifunctionality of MSN-based systems toward translation. Here, we update the recent progress on MSN-based systems for theranostic purposes. We discuss various synthetic approaches used to construct the theranostic platforms either via intrinsic chemistry or extrinsic combination. These include defect generation in the silica structure, encapsulation of diagnostic NPs within silica, their assembly on the silica surface, and direct conjugation of dye chemicals. Collectively, in vitro and in vivo results demonstrate that multimodal imaging capacities can be integrated with the therapeutic functions of these MSN systems for therapy. With further improvement in bioimaging sensitivity and targeting specificity, the multifunctional MSN-based theranostic systems will find many clinical applications in the near future.

Materials Chemistry of Nanoultrasonic Biomedicine

As a special cross-disciplinary research frontier, nanoultrasonic biomedicine refers to the design and synthesis of nanomaterials to solve some critical issues of ultrasound (US)-based biomedicine. The concept of nanoultrasonic biomedicine can also overcome the drawbacks of traditional microbubbles and promote the generation of novel US-based contrast agents or synergistic agents for US theranostics. Here, we discuss the recent developments of material chemistry in advancing the nanoultrasonic biomedicine for diverse US-based bio-applications. We initially introduce the design principles of novel nanoplatforms for serving the nanoultrasonic biomedicine, from the viewpoint of synthetic material chemistry. Based on these principles and diverse US-based bio-application backgrounds, the representative proof-of-concept paradigms on this topic are clarified in detail, including nanodroplet vaporization for intelligent/responsive US imaging, multifunctional nano-contrast agents for US-based multi-modality imaging, activatable synergistic agents for US-based therapy, US-triggered on-demand drug releasing, US-enhanced gene transfection, US-based synergistic therapy on combating the cancer and potential toxicity issue of screening various nanosystems suitable for nanoultrasonic biomedicine. It is highly expected that this novel nanoultrasonic biomedicine and corresponding high performance in US imaging and therapy can significantly promote the generation of new sub-discipline of US-based biomedicine by rationally integrating material chemistry and theranostic nanomedicine with clinical US-based biomedicine.

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.

Tracking Perfluorocarbon Nanoemulsion Delivery by 19F MRI for Precise High Intensity Focused Ultrasound Tumor Ablation

Perfluorocarbon nanoemulsions (PFCNEs) have recently been undergoing rigorous study to investigate their ability to improve the therapeutic efficacy of tumor ablation by high intensity focused ultrasound (HIFU). For precise control of PFCNE delivery and thermal ablation, their accumulation and distribution in a tumor should be quantitatively analyzed. Here, we used fluorine-19 (¹⁹F) magnetic resonance imaging (MRI) to quantitatively track PFCNE accumulation in a tumor, and analyzed how intra-tumoral PFCNE quantities affect the therapeutic efficacy of HIFU treatment. Ablation outcomes were assessed by intra-voxel incoherent motion analysis and bioluminescent imaging up to 14 days after the procedure. Assessment of PFCNE delivery and treatment outcomes showed that 2-3 mg/mL of PFCNE in a tumor produces the largest ablation volume under the same HIFU insonation conditions. Histology showed varying degrees of necrosis depending on the amount of PFCNE delivered. ¹⁹F MRI promises to be a valuable platform for precisely guiding PFCNE-enhanced HIFU ablation of tumors.

Ultrasound Triggered Tumor Oxygenation with Oxygen-Shuttle Nanoperfluorocarbon to Overcome Hypoxia-Associated Resistance in Cancer Therapies

Tumor hypoxia is known to be one of critical reasons that limit the efficacy of cancer therapies, particularly photodynamic therapy (PDT) and radiotherapy (RT) in which oxygen is needed in the process of cancer cell destruction. Herein, taking advantages of the great biocompatibility and high oxygen dissolving ability of perfluorocarbon (PFC), we develop an innovative strategy to modulate the tumor hypoxic microenvironment using nano-PFC as an oxygen shuttle for ultrasound triggered tumor-specific delivery of oxygen. In our experiment, nanodroplets of PFC stabilized by albumin are intravenously injected into tumor-bearing mice under hyperoxic breathing. With a low-power clinically adapted ultrasound transducer applied on their tumor, PFC nanodroplets that adsorb oxygen in the lung would rapidly release oxygen in the tumor under ultrasound stimulation, and then circulate back into the lung for reoxygenation. Such repeated cycles would result in dramatically enhanced tumor oxygenation and thus remarkably improved therapeutic outcomes in both PDT and RT treatment of tumors. Importantly, our strategy may be applied for different types of tumor models. Hence, this work presents a simple strategy to promote tumor oxygenation with great efficiency using agents and instruments readily available in the clinic, so as to overcome the hypoxia-associated resistance in cancer treatment.

Micro/Nanoparticle-Augmented Sonodynamic Therapy (SDT): Breaking the Depth Shallow of Photoactivation

The fast development of photoactivation for cancer treatment provides an efficient photo-therapeutic strategy for cancer treatment, but traditional photodynamic or photothermal therapy suffers from the critical issue of low in vivo penetration depth of tissues. As a non-invasive therapeutic modality, sonodynamic therapy (SDT) can break the depth barrier of photoactivation because ultrasound has an intrinsically high tissue-penetration performance. Micro/nanoparticles can efficiently augment the SDT efficiency based on nanobiotechnology. The state-of-art of the representative achievements on micro/nanoparticle-enhanced SDT is summarized, and specific functions of micro/nanoparticles for SDT are discussed, from the different viewpoints of ultrasound medicine, material science and nanobiotechnology. Emphasis is put on the relationship of structure/composition-SDT performance of micro/nanoparticle-based sonosensitizers. Three types of micro/nanoparticle-augmented SDT are discussed, including organic and inorganic sonosensitizers and micro/nanoparticle-based but sonosensitizer-free strategies to enhance the SDT outcome. SDT-based synergistic cancer therapy augmented by micro/nanoparticles and their biosafety are also included. Some urgent critical issues and potential developments of micro/nanoparticle-augmented SDT for efficient cancer treatment are addressed. It is highly expected that micro/nanoparticle-augmented SDT will be quickly developed as a new and efficient therapeutic modality which will find practical applications in cancer treatment. At the same time, fundamental disciplines regarding materials science, chemistry, medicine and nanotechnology will be advanced.