Nanotechnology-enabled sonodynamic therapy against malignant tumors

Sonodynamic therapy (SDT) is an emerging approach for malignant tumor treatment, offering high precision, deep tissue penetration, and minimal side effects. The rapid advancements in nanotechnology, particularly in cancer treatment, have enhanced the efficacy and targeting specificity of SDT. Combining sonodynamic therapy with nanotechnology offers a promising direction for future cancer treatments. In this review, we first systematically discussed the anti-tumor mechanism of SDT and then summarized the common nanotechnology-related sonosensitizers and their recent applications. Subsequently, nanotechnology-related therapies derived using the SDT mechanism were elaborated. Finally, the role of nanomaterials in SDT combined therapy was also introduced.

Recent Developments of Inorganic Nanosensitizers for Sonodynamic Therapy

As a noninvasive treatment, sonodynamic therapy (SDT) has been widely used in the treatment of tumors because of its ability to penetrate deep tissue with few side effects. As the key factor of SDT, it is meaningful to design and synthesize efficient sonosensitizers. Compared with organic sonosensitizers, inorganic sonosensitizers can be easily excited by ultrasound. In addition, inorganic sonosensitizers with stable properties, good dispersion, and long blood circulation time, have great development potential in SDT. This review summarizes possible mechanisms of SDT (sonoexcitation and ultrasonic cavitation) in detail. Based on these mechanisms, the design and synthesis of inorganic nanosonosensitizers can be divided into three categories: traditional inorganic semiconductor sonosensitizers, enhanced inorganic semiconductor sonosensitizers, and cavitation-enhanced sonosensitizers. Subsequently, the current efficient construction methods of sonosensitizers are summarized including accelerated semiconductor charge separation and enhanced production of reactive oxygen species through ultrasonic cavitation. Furthermore, the advantages and disadvantages of different inorganic sonosensitizers and detailed strategies are systematically discussed on how to enhance SDT. Hopefully, this review could provide new insights into the design and synthesis of efficient inorganic nano-sonosensitizers for SDT.

Ultrasound nanotheranostics: Toward precision medicine

Ultrasound (US) is a mechanical wave that can penetrate biological tissues and trigger complex bioeffects. The mechanisms of US in different diagnosis and treatment are different, and the functional application of commercial US is also expanding. In particular, recent developments in nanotechnology have led to a wider use of US in precision medicine. In this review, we focus on US in combination with versatile micro and nanoparticles (NPs)/nanovesicles for tumor theranostics. We first introduce US-assisted drug delivery as a stimulus-responsive approach that spatiotemporally regulates the deposit of nanomedicines in target tissues. Multiple functionalized NPs and their US-regulated drug-release curves are analyzed in detail. Moreover, as a typical representative of US therapy, sonodynamic antitumor strategy is attracting researchers' attention. The collaborative efficiency and mechanisms of US and various nano-sensitizers such as nano-porphyrins and organic/inorganic nanosized sensitizers are outlined in this paper. A series of physicochemical processes during ultrasonic cavitation and NPs activation are also discussed. Finally, the new applications of US and diagnostic NPs in tumor-monitoring and image-guided combined therapy are summarized. Diagnostic NPs contain substances with imaging properties that enhance US contrast and photoacoustic imaging. The development of such high-resolution, low-background US-based imaging methods has contributed to modern precision medicine. It is expected that the integration of non-invasive US and nanotechnology will lead to significant breakthroughs in future clinical applications.

Recent Advances in 3D Printing of Photocurable Polymers: Types, Mechanism, and Tissue Engineering Application

The conversion of liquid resin into solid structures upon exposure to light of a specific wavelength is known as photopolymerization. In recent years, photopolymerization-based 3D printing has gained enormous attention for constructing complex tissue-specific constructs. Due to the economic and environmental benefits of the biopolymers employed, photo-curable 3D printing is considered an alternative method for replacing damaged tissues. However, the lack of suitable bio-based photopolymers, their characterization, effective crosslinking strategies, and optimal printing conditions are hindering the extensive application of 3D printed materials in the global market. This review highlights the present status of various photopolymers, their synthesis, and their optimization parameters for biomedical applications. Moreover, a glimpse of various photopolymerization techniques currently employed for 3D printing is also discussed. Furthermore, various naturally derived nanomaterials reinforced polymerization and their influence on printability and shape fidelity are also reviewed. Finally, the ultimate use of those photopolymerized hydrogel scaffolds in tissue engineering is also discussed. Taken together, it is believed that photopolymerized 3D printing has a great future, whereas conventional 3D printing requires considerable sophistication, and this review can provide readers with a comprehensive approach to developing light-mediated 3D printing for tissue-engineering applications.

3D-CEUS tracking of injectable chemo-sonodynamic therapy-enabled mop-up of residual renal cell carcinoma after thermal ablation

Thermal ablation (TA), as a minimally invasive therapeutic technique, has been extensively used to the treatment of solid tumors, such as renal cell carcinoma (RCC), which, unfortunately, still fails to overcome the high risk of local recurrence and distant metastasis since the incomplete ablation cannot be ignored due to various factors such as the indistinguishable tumor margins and limited ablation zone. Herein, we report the injectable thermosensitive hydrogel by confining curcumin (Cur)-loaded hollow mesoporous organosilica nanoparticles (Cur@HMON@gel) which can locate in tumor site more than half a month and mop up the residual RCC under ultrasound (US) irradiation after transforming from colloidal sol status to elastic gel matrix at physiological temperature. Based on the US-triggered accelerated diffusion of the model chemotherapy drug with multi-pharmacologic functions, the sustained and controlled release of Cur has been demonstrated in vitro. Significantly, US is employed as an external energy to trigger Cur, as a sonosensitizer also, to generate reactive oxygen species (ROS) for sonodynamic tumor therapy (SDT) in parallel. Tracking by the three-dimensional contrast-enhanced ultrasound (3D-CEUS) imaging, the typical decreased blood perfusions have been observed since the residual xenograft tumor after incomplete TA were effectively suppressed during the chemo-sonodynamic therapy process. The high in vivo biocompatibility and biodegradability of the multifunctional nanoplatform confined by thermogel provide the potential of their further clinical translation for the solid tumor eradication under the guidance and monitoring of 3D-CEUS.

The crosstalk between sonodynamic therapy and autophagy in cancer

As a noninvasive treatment approach for cancer and other diseases, sonodynamic therapy (SDT) has attracted extensive attention due to the deep penetration of ultrasound, good focusing, and selective irradiation sites. However, intrinsic limitations of traditional sonosensitizers hinder the widespread application of SDT. With the development of nanotechnology, nanoparticles as sonosensitizers or as a vehicle to deliver sonosensitizers have been designed and used to target tissues or tumor cells with high specificity and accuracy. Autophagy is a common metabolic alteration in both normal cells and tumor cells. When autophagy happens, a double-membrane autophagosome with sequestrated intracellular components is delivered and fused with lysosomes for degradation. Recycling these cell materials can promote survival under a variety of stress conditions. Numerous studies have revealed that both apoptosis and autophagy occur after SDT. This review summarizes recent progress in autophagy activation by SDT through multiple mechanisms in tumor therapies, drug resistance, and lipid catabolism. A promising tumor therapy, which combines SDT with autophagy inhibition using a nanoparticle delivering system, is presented and investigated.

Mesoporous Silica Nanoprodrug Encapsulated with Near-Infrared Absorption Dye for Photothermal Therapy Combined with Chemotherapy

Based on the tumor microenvironment with weak acidic characteristics, a nano-drug delivery system that achieves controlled release of drugs through the pH response has been a popular strategy to improve the effectiveness of tumor therapy and reduce toxic side effects, and combining photothermal therapy (PTT) on this basis can help improve the antitumor effect. In this study, mesoporous silica nanoparticles (MSNs) were surface-modified with polymer poly(PEGMA-co-HEMA) via surface-initiated atom transfer radical polymerization, and a multifunctional nanoplatform MSN@poly(PEGMA-co-HEMA-g-doxorubicin (DOX)/indocyanine green (ICG) was designed for effective photothermal/chemotherapy combination therapy. The anticancer drug DOX was anchored to the polymer on the surface of MSN by reversible covalent bond cis-aconitic anhydride with a drug loading of 10%. Meanwhile, the small-molecule dye was loaded into the pores of MSN, and PTT mediated by near-infrared (NIR) radiation could further kill cancer cells. Under low-pH stimulation, the cis-aconitic anhydride bond breaks and DOX is released, with a 65% increase in cumulative drug release over 50 h compared to that at pH 7.4 (normal physiological environment). The high temperature induced by photothermal conversion accelerated the reversible covalent bond breakage, and the cumulative drug release at pH 5.0 for 3 h at elevated temperature up to 50 °C increased by 24.3% compared with that under normal physiological conditions (T = 37 °C), demonstrating that increasing the temperature can reduce the time required to reach blood drug concentration. In vitro cytotoxicity results revealed that the prodrug delivery system showed stronger cytotoxicity under NIR light irradiation compared with free DOX, with more than 90% of tumor cells killed after 48 h. Therefore, MSN@poly(PEGMA-co-HEMA-g-DOX)/ICG enhanced the synergistic effect of chemotherapy through photothermal action and accelerated reversible chemical bond cleavage, which has great potential in the combined therapy of cancer.

Solvent-Dependent Adsorption-Driven Mechanism for MOFs-Based Yolk-Shell Nanostructures

Metal-organic frameworks (MOFs)-based yolk-shell nanostructures have drawn enormous attention recently due to their multifunctionality. However, the regulations of the size and morphology of yolk-shell nanostructures are still limited by the unclear formation mechanism. Herein, we first demonstrated a solvent-dependent adsorption-driven mechanism for synthesizing yolk-shelled MOFs-based nanostructures coated with mesoporous SiO₂ shells (ZIF-8@mSiO₂ ) with tunable size and morphology. The selective and competitive adsorption of methanol (CH₃ OH) and water (H₂ O) on ZIF-8 core were found to have decisive effects on inducing the morphology evolution of yolk-shell nanostructures. The obtained yolk-shelled ZIF-8@mSiO₂ nanostructures show great promise in generating acoustic cavitation effect for sonodynamic cancer therapy in vitro. We believe that this work will not only help us to design novel MOFs-based yolk-shell nanostructures, but also promote the widespread application of MOFs materials.

Construction of Enzyme Nanoreactors to Enable Tumor Microenvironment Modulation and Enhanced Cancer Treatment

Enzymes play pivotal roles in regulating and maintaining the normal functions of all living systems, and some of them are extensively employed for diagnosis and treatment of diverse diseases. More recently, several kinds of enzymes with unique catalytic activities have been found to be promising options to directly suppress tumor growth and/or augment the therapeutic efficacy of other treatments by modulating the hostile tumor microenvironment (TME), which is reported to negatively impair the therapeutic efficacy of different cancer treatments. In this review, first a summary is presented on the chemical approaches utilized for the construction of distinct enzyme nanoreactors with well-retained catalytic performance and reduced immunogenicity. Then, the utilization of such enzyme nanoreactors in attenuating tumor hypoxia, modulating extracellular matrix, and amplifying tumor oxidative stress is discussed in depth. Afterward, some perspectives are presented on the future development of such enzyme nanoreactors in TME modulation and enhanced cancer treatment.

A Review of Mesoporous Silica Nanoparticle Delivery Systems in Chemo-Based Combination Cancer Therapies

Chemotherapy is an important anti-tumor treatment in clinic to date, however, the effectiveness of traditional chemotherapy is limited by its poor selectivity, high systemic toxicity, and multidrug resistance. In recent years, mesoporous silica nanoparticles (MSNs) have become exciting drug delivery systems (DDS) due to their unique advantages, such as easy large-scale production, adjustable uniform pore size, large surface area and pore volumes. While mesoporous silica-based DDS can improve chemotherapy to a certain extent, when used in combination with other cancer therapies MSN based chemotherapy exhibits a synergistic effect, greatly improving therapeutic outcomes. In this review, we discuss the applications of MSN DDS for a diverse range of chemotherapeutic combination anti-tumor therapies, including phototherapy, gene therapy, immunotherapy and other less common modalities. Furthermore, we focus on the characteristics of each nanomaterial and the synergistic advantages of the combination therapies. Lastly, we examine the challenges and future prospects of MSN based chemotherapeutic combination therapies.

Spatiotemporally Controlled Photoresponsive Hydrogels: Design and Predictive Modeling from Processing through Application

Photoresponsive hydrogels (PRHs) are soft materials whose mechanical and chemical properties can be tuned spatially and temporally with relative ease. Both photo-crosslinkable and photodegradable hydrogels find utility in a range of biomedical applications that require tissue-like properties or programmable responses. Progress in engineering with PRHs is facilitated by the development of theoretical tools that enable optimization of their photochemistry, polymer matrices, nanofillers, and architecture. This review brings together models and design principles that enable key applications of PRHs in tissue engineering, drug delivery, and soft robotics, and highlights ongoing challenges in both modeling and application.

Integration of microbubbles with biomaterials in tissue engineering for pharmaceutical purposes

Tissue engineering with the aid of biomaterials is a novel and promising knowledge aiming at improving human life expectancy. Besides, microbubbles are increasingly employed in biomedical applications due to their capability as a reservoir of therapeutic agents and oxygen molecules. In the present study, Microbubbles as the backbone of the research are produced as one of the potent devices in tissue engineering approaches, including drug delivery, wound healing, 3D printing, and scaffolding. It was shown that microbubbles are capable of promoting oxygen penetration and boosting the wound healing process by supplying adequate oxygen. Microbubbles also demonstrated their strength and potency in advancing drug delivery systems by reinforcing mass transfer phenomena. Furthermore, microbubbles developed the mechanical and biological characteristics of engineered scaffolds by manipulating the pores. Increasing cell survival, the biological activity of cells, angiogenesis, cell migration, and also nutrient diffusion into the inner layers of the scaffold were other achievements by microbubbles. In conclusion, the interest of biomedical communities in simultaneous usage of microbubbles and biomaterials under tissue engineering approaches experiences remarkable growth in Pharmaceutical studies.

New Advances in In Vivo Applications of Gated Mesoporous Silica as Drug Delivery Nanocarriers

One appealing concept in the field of hybrid materials is related to the design of gated materials. These materials are prepared in such a way that the release of chemical or biochemical species from voids of porous supports to a solution is triggered upon the application of external stimuli. Such gated materials are mainly composed of two subunits: i) a porous inorganic scaffold in which a cargo is stored, and ii) certain molecular or supramolecular entities, grafted onto the external surface, that can control mass transport from the interior of the pores. On the basis of this concept, a large number of examples are developed in the past ten years. A comprehensive overview of gated materials used in drug delivery applications in in vivo models from 2016 to date is thus given here.

ROS-Responsive Blended Nanoparticles: Cascade-Amplifying Synergistic Effects of Sonochemotherapy with On-demand Boosted Drug Release During SDT Process

Sonodynamic therapy (SDT) not only has greater tissue-penetrating depth compared to photo-stimulated therapies, but also can also trigger rapid drug release to achieve synergistic sonochemotherapy. Here, reactive oxygen species (ROS)-responsive IR780/PTL- nanoparticles (NPs) are designed by self-assembly, which contain ROS-cleavable thioketal linkers (TL) to promote paclitaxel (PTX) release during SDT. Under ultrasound (US) stimulation, IR780/PTL-NPs produce high amounts of ROS, which not only induces apoptosis in human glioma (U87) cells but also boosts PTX released by decomposing the ROS-sensitive TL. In the U87 tumor-bearing mouse model, the IR780/PTL-NPs releases the drug at the target sites in a controlled manner upon US irradiation, which significantly inhibits tumor growth and induces apoptosis in the tumor tissues with no obvious toxicity. Taken together, the IR780/PTL-NPs are a novel platform for sonochemotherapy, and can control the spatio-temporal release of chemotherapeutic drugs during SDT.

New insights towards mesoporous silica nanoparticles as a technological platform for chemotherapeutic drugs delivery

Mesoporous silica nanoparticles (MSNs) displays interesting properties for biomedical applications such as high chemical stability, large surface area and tunable pores diameters and volumes, allowing the incorporation of large amounts of drugs, protecting them from deactivation and degradation processes acting as an excellent nanoplatform for drug delivery. However, the functional MSNs do not present the ability to transport the therapeutics without any leakage until reach the targeted cells causing side effects. On the other hand, the hydroxyls groups available on MSNs surface allows the conjugation of specific molecules which can binds to the overexpressed Enhanced Growth Factor Receptor (EGFR) in many tumors, representing a potential strategy for the cancer treatment. Beyond that, the targeting molecules conjugate onto mesoporous surface increase its cell internalization and act as gatekeepers blocking the mesopores controlling the drug release. In this context, multifunctional MSNs emerge as stimuli-responsive controlled drug delivery systems (CDDS) to overcome drawbacks as low internalization, premature release before to reach the region of interest, several side effects and low effectiveness of the current treatments. This review presents an overview of MSNs fabrication methods and its properties that affects drug delivery as well as stimuli-responsive CDDS for cancer treatment.

Recent advances in photo-crosslinkable hydrogels for biomedical applications

Photo-crosslinkable hydrogels have recently attracted significant scientific interest. Their properties can be manipulated in a spatiotemporal manner through exposure to light to achieve the desirable functionality for various biomedical applications. This review article discusses the recent advances of the most common photo-crosslinkable hydrogels, including poly(ethylene glycol) diacrylate, gelatin methacryloyl and methacrylated hyaluronic acid, for various biomedical applications. We first highlight the advantages of photopolymerization and discuss diverse photosensitive systems used for the synthesis of photo-crosslinkable hydrogels. We then introduce their synthesis methods and review their latest state of development in biomedical applications, including tissue engineering and regenerative medicine, drug delivery, cancer therapies and biosensing. Lastly, the existing challenges and future perspectives of engineering photo-crosslinkable hydrogels for biomedical applications are briefly discussed.

Pre-drug Self-assembled Nanoparticles: Recovering activity and overcoming glutathione-associated cell antioxidant resistance against photodynamic therapy

In photodynamic therapy (PDT), the elevated glutathione (GSH) of cancer cells have two sides for treatment efficacy, activation pre-drug by removing activity suppressor part (advantages) and consumption reactive oxygen species (ROS) to confer PDT resistance (disadvantages). Preparation all-in-one system by simple method to make best use of the advantages and bypass the disadvantages still were remains a technical challenge. Herein, we report a robust PDT nanoparticle with above function based on a self-assembled pyridine modified Zinc phthalocyanine (ZnPc-DTP). The activity suppressor and active part of ZnPc-DTP were linked by disulfide bond. After targeting cancer cells, GSH can react with ZnPc-DTP nanoparticles by cutting disulfide bond to release its active part (ZnPc-SH) and oxidize GSH. In vitro and in vivo results indicated that ZnPc-SH can effective suppress tumor growth under the low antioxidant tumor microenvironment (TME).

Nanotechnology for Cancer Therapy Based on Chemotherapy

Chemotherapy has been widely applied in clinics. However, the therapeutic potential of chemotherapy against cancer is seriously dissatisfactory due to the nonspecific drug distribution, multidrug resistance (MDR) and the heterogeneity of cancer. Therefore, combinational therapy based on chemotherapy mediated by nanotechnology, has been the trend in clinical research at present, which can result in a remarkably increased therapeutic efficiency with few side effects to normal tissues. Moreover, to achieve the accurate pre-diagnosis and real-time monitoring for tumor, the research of nano-theranostics, which integrates diagnosis with treatment process, is a promising field in cancer treatment. In this review, the recent studies on combinational therapy based on chemotherapy will be systematically discussed. Furthermore, as a current trend in cancer treatment, advance in theranostic nanoparticles based on chemotherapy will be exemplified briefly. Finally, the present challenges and improvement tips will be presented in combination therapy and nano-theranostics.

Sonodynamic therapy (SDT): a novel strategy for cancer nanotheranostics

Sonodynamic therapy (SDT) is a promising non-invasive therapeutic modality. Compared to photo-inspired therapy, SDT provides many opportunities and benefits, including deeper tissue penetration, high precision, less side effects, and good patient compliance. Thanks to the facile engineerable nature of nanotechnology, nanoparticles-based sonosensitizers exhibit predominant advantages, such as increased SDT efficacy, binding avidity, and targeting specificity. This review aims to summarize the possible mechanisms of SDT, which can be expected to provide the theoretical basis for SDT development in the future. We also extensively discuss nanoparticle-assisted sonosensitizers to enhance the outcome of SDT. Additionally, we focus on the potential strategy of combinational SDT with other therapeutic modalities and discuss the limitations and challenges of SDT toward clinical applications.