Thermo-Triggered In Situ Chitosan-Based Gelation System for Repeated and Enhanced Sonodynamic Therapy Post a Single Injection

External stimuli-driven catalytic hydrogels for biomedical applications

Hydrogels, bearing three-dimensional networks formed through chemical or physical crosslinking of hydrophilic macromolecules, benefit from their biocompatibility, tunable properties, and high loading capacities, and thus hold great promise for biomedical applications. Recent advancements have increasingly focused on the integration of non-invasive external stimuli-such as light, heat, electricity, magnetism, and ultrasound-into hydrogel design. These external stimuli-driven catalytic hydrogels can dynamically respond to these stimuli, allowing for high spatial and temporal precision in their application. This capability enables in situ activation, controlled degradation, and catalytic reactions, making them ideal for next-generation clinical interventions. This review discusses the design strategies for external stimuli-driven catalytic hydrogels, concentrating on essential mechanisms of catalytic processes aimed at optimizing therapeutic efficacy. The discussion highlights the importance of precise control over the chemical and physical properties of hydrogels in response to specific stimuli, elucidating the regulatory mechanisms that dictate hydrogel behavior and deepening the understanding of their applications with enhanced spatial and temporal resolution.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Ultrasound-Triggered Azo Free Radicals for Cervical Cancer Immunotherapy

PD-1 blockade is a first-line treatment for recurrent/metastatic cervical cancer but benefits only a small number of patients due to low preexisting tumor immunogenicity. Using immunogenic cell death (ICD) inducers is a promising strategy for improving immunotherapy, but these compounds are limited by the hypoxic environment of solid tumors. To overcome this issue, the nanosensitizer AIBA@MSNs were designed based on sonodynamic therapy (SDT), which induces tumor cell death under hypoxic conditions through azo free radicals in a method of nonoxygen radicals. Mechanistically, the azo free radicals disrupt both the structure and function of tumor mitochondria by reversing the mitochondrial membrane potential and facilitating the collapse of electron transport chain complexes. More importantly, the AIBA@MSN-based SDT serves as an effective ICD inducer and improves the antitumor immune capacity. The combination of an AIBA@MSN-based SDT with a PD-1 blockade has the potential to improve response rates and provide protection against relapse. This study provides insights into the use of azo free radicals as a promising SDT strategy for cancer treatment and establishes a basic foundation for nonoxygen-dependent SDT-triggered immunotherapy in cervical cancer treatment.

Nanozyme-Integrated Thermoresponsive In Situ Forming Hydrogel Enhances Mesenchymal Stem Cell Viability and Paracrine Effect for Efficient Spinal Cord Repair

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising strategy for the treatment of spinal cord injury (SCI). However, the hostile microenvironment of SCI, which can adversely affect the survival and paracrine effect of the implanted MSCs, severely limits the therapeutic efficacy of this approach. Here, we report on a ceria nanozyme-integrated thermoresponsive in situ forming hydrogel (CeNZ-gel) that can enable dual enhancement of MSC viability and paracrine effect, leading to highly efficient spinal cord repair. The sol-gel transition property of the CeNZ-gel at body temperature ensures uniform coverage of the hydrogel in injured spinal cord tissues. Our results demonstrate that the CeNZ-gel significantly increases the viability of transplanted MSCs in the microenvironment by attenuating oxidative stress and, more importantly, promotes the secretion of angiogenic factors from MSCs by inducing autophagy of MSCs. The synergy between the oxidative stress-relieving effect of CeNZs and the paracrine effect of MSCs accelerates angiogenesis, nerve repair, and motor function recovery after SCI, providing an efficient strategy for MSC-based SCI therapy.

Research progress on reactive oxygen species production mechanisms in tumor sonodynamic therapy

In recent years, because of the growing desire to improve the noninvasiveness and safety of tumor treatments, sonodynamic therapy has gradually become a popular research topic. However, due to the complexity of the therapeutic process, the relevant mechanisms have not yet been fully elucidated. One of the widely accepted possibilities involves the effect of reactive oxygen species. In this review, the mechanism of reactive oxygen species production by sonodynamic therapy (SDT) and ways to enhance the sonodynamic production of reactive oxygen species are reviewed. Then, the clinical application and limitations of SDT are discussed. In conclusion, current research on sonodynamic therapy should focus on the development of sonosensitizers that efficiently produce active oxygen, exhibit biological safety, and promote the clinical transformation of sonodynamic therapy.

Research progress on reactive oxygen species production mechanisms in tumor sonodynamic therapy

In recent years, because of the growing desire to improve the noninvasiveness and safety of tumor treatments, sonodynamic therapy has gradually become a popular research topic. However, due to the complexity of the therapeutic process, the relevant mechanisms have not yet been fully elucidated. One of the widely accepted possibilities involves the effect of reactive oxygen species. In this review, the mechanism of reactive oxygen species production by sonodynamic therapy (SDT) and ways to enhance the sonodynamic production of reactive oxygen species are reviewed. Then, the clinical application and limitations of SDT are discussed. In conclusion, current research on sonodynamic therapy should focus on the development of sonosensitizers that efficiently produce active oxygen, exhibit biological safety, and promote the clinical transformation of sonodynamic therapy.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

Hypoxia is a typical feature of most solid tumors and has important effects on tumor cells' proliferation, invasion, and metastasis. This is the key factor that leads to poor efficacy of different kinds of therapy including chemotherapy, radiotherapy, photodynamic therapy, etc. In recent years, the construction of hypoxia-relieving functional nanoplatforms through nanotechnology has become a new strategy to reverse the current situation of tumor microenvironment hypoxia and improve the effectiveness of tumor treatment. Here, the main strategies and recent progress in constructing nanoplatforms are focused on to directly carry oxygen, generate oxygen in situ, inhibit mitochondrial respiration, and enhance blood perfusion to alleviate tumor hypoxia. The advantages and disadvantages of these nanoplatforms are compared. Meanwhile, nanoplatforms based on organic and inorganic substances are also summarized and classified. Through the comprehensive overview, it is hoped that the summary of these nanoplatforms for alleviating hypoxia could provide new enlightenment and prospects for the construction of nanomaterials in this field.

Nanosonosensitizers-engineered injectable thermogel for augmented chemo-sonodynamic therapy of melanoma and infected wound healing

Easy recurrence and bacteria infected-wound healing after surgery excision pose severe challenges to clinical melanoma therapy. Herein, an injectable CuO2 nanodots-engineered thermosensitive chitosan hydrogel (CuO2-BSO@Gel) for enhanced melanoma chemo-sonodynamic therapy and improved infected wound healing was rationally constructed by facilely integrating the CuO2 nanodots and L-Buthionine-(S, R)-sulfoximine (BSO) with thermoresponsive hydrogel. Favored by the Fenton catalytic activity of Cu2+, the CuO2 nanodots can achieve enhanced chemodynamic therapy (CDT) by self-supplying H2O2 under acidic tumor microenvironment. Simultaneously, the CuO2 nanodots with a narrow bandgap (2.29 ​eV) were proven to be the efficient sonosensitizers, and the corresponding quantum yield of singlet oxygen (1O2) could be boosted by the O2 generation during Fenton-like reactions. Additionally, combining with the glutathione (GSH) depletion of loaded BSO, intracellular oxidative stress induced by SDT and CDT was further amplified, leading to the specific ferroptosis. Importantly, this multifunctional hydrogel significantly promoted the proliferation of normal skin cells and accelerated the bacteria-infected wound healing by the effective chemo-sonodynamic antibacterial activity and the enhanced angiogenesis. Thus, the engineered thermogel features the distinct chemo-sonodynamic performance, desirable biocompatibility and bioactivity, providing a competitive strategy for eradicating melanoma and infected wound healing.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Biomedical engineered nanomaterials to alleviate tumor hypoxia for enhanced photodynamic therapy

Photodynamic therapy (PDT), as a highly selective, widely applicable, and non-invasive therapeutic modality that is an alternative to radiotherapy and chemotherapy, is extensively applied to cancer therapy. Practically, the efficiency of PDT is severely hindered by the existence of hypoxia in tumor tissue. Hypoxia is a typical hallmark of malignant solid tumors, which remains an essential impediment to many current treatments, thereby leading to poor clinical prognosis after therapy. To address this issue, studies have been focused on modulating tumor hypoxia to augment the therapeutic efficacy. Although nanomaterials to relieve tumor hypoxia for enhanced PDT have been demonstrated in many research articles, a systematical summary of the role of nanomaterials in alleviating tumor hypoxia is scarce. In this review, we introduced the mechanism of PDT, and the involved therapeutic modality of PDT for ablation of tumor cells was specifically summarized. Moreover, current advances in nanomaterials-mediated tumor oxygenation via oxygen-carrying or oxygen-generation tactics to alleviate tumor hypoxia are emphasized. Based on these considerable summaries and analyses, we proposed some feasible perspectives on nanoparticle-based tumor oxygenation to ameliorate the therapeutic outcomes, which may provide some detailed information in designing new oxygenation nanomaterials in this burgeneous field.

Newly developed gas-assisted sonodynamic therapy in cancer treatment

Sonodynamic therapy (SDT) is an emerging noninvasive treatment modality that utilizes low-frequency and low-intensity ultrasound (US) to trigger sensitizers to kill tumor cells with reactive oxygen species (ROS). Although SDT has attracted much attention for its properties including high tumor specificity and deep tissue penetration, its anticancer efficacy is still far from satisfactory. As a result, new strategies such as gas-assisted therapy have been proposed to further promote the effectiveness of SDT. In this review, the mechanisms of SDT and gas-assisted SDT are first summarized. Then, the applications of gas-assisted SDT for cancer therapy are introduced and categorized by gas types. Next, therapeutic systems for SDT that can realize real-time imaging are further presented. Finally, the challenges and perspectives of gas-assisted SDT for future clinical applications are discussed.

Tumor microenvironment penetrating chitosan nanoparticles for elimination of cancer relapse and minimal residual disease

Chitosan and its derivatives are among biomaterials with numerous medical applications, especially in cancer. Chitosan is amenable to forming innumerable shapes such as micelles, niosomes, hydrogels, nanoparticles, and scaffolds, among others. Chitosan derivatives can also bring unprecedented potential to cross numerous biological barriers. Combined with other biomaterials, hybrid and multitasking chitosan-based systems can be realized for many applications. These include controlled drug release, targeted drug delivery, post-surgery implants (immunovaccines), theranostics, biosensing of tumor-derived circulating materials, multimodal systems, and combination therapy platforms with the potential to eliminate bulk tumors as well as lingering tumor cells to treat minimal residual disease (MRD) and recurrent cancer. We first introduce different formats, derivatives, and properties of chitosan. Next, given the barriers to therapeutic efficacy in solid tumors, we review advanced formulations of chitosan modules as efficient drug delivery systems to overcome tumor heterogeneity, multi-drug resistance, MRD, and metastasis. Finally, we discuss chitosan NPs for clinical translation and treatment of recurrent cancer and their future perspective.

Ultrasound Responsive Smart Implantable Hydrogels for Targeted Delivery of Drugs: Reviewing Current Practices

Over the last two decades, the process of delivering therapeutic drugs to a patient with a controlled release profile has been a significant focus of drug delivery research. Scientists have given tremendous attention to ultrasound-responsive hydrogels for several decades. These smart nanosystems are more applicable than other stimuli-responsive drug delivery vehicles (ie UV-, pH- and thermal-, responsive materials) because they enable more efficient targeted treatment via relatively non-invasive means. Ultrasound (US) is capable of safely transporting energy through opaque and complex media with minimal loss of energy. It is capable of being localized to smaller regions and coupled to systems operating at various time scales. However, the properties enabling the US to propagate effectively in materials also make it very difficult to transform acoustic energy into other forms that may be used. Recent research from a variety of domains has attempted to deal with this issue, proving that ultrasonic effects can be used to control chemical and physical systems with remarkable specificity. By obviating the need for multiple intravenous injections, implantable US responsive hydrogel systems can enhance the quality of life for patients who undergo treatment with a varied dosage regimen. Ideally, the ease of self-dosing in these systems would lead to increased patient compliance with a particular therapy as well. However, excessive literature has been reported based on implanted US responsive hydrogel in various fields, but there is no comprehensive review article showing the strategies to control drug delivery profile. So, this review was aimed at discussing the current strategies for controlling and targeting drug delivery profiles using implantable hydrogel systems.

Application of Hydrogels as Carrier in Tumor Therapy: A Review

Cancer is one of the most intractable diseases in the world because of its high recurrence rate, high metastasis rate and high lethality rate. Traditional chemotherapy, radiotherapy and surgery have unsatisfactory therapeutic effects and cause many severe side effects at the same time. Hydrogel is a new type of biomaterial with the advantages of good biocompatibility and easy degradation, which can be used as a carrier of functional nanomaterials for tumor therapy. Herein, we represent the progress of hydrogels with different skeletons and their application as carrier in tumor treatment. The hydrogels are listed as polyethylene glycol-based hydrogels, chitosan-based hydrogels, peptide-based hydrogels, hyaluronic acid-based hydrogels, steroid-based hydrogels and other hydrogels by skeletons, and their properties, modifications and toxicities were introduced. Some representative applications of combined hydrogels with nanomaterial for chemotherapy, photodynamic therapy, photothermal therapy, sonodynamic therapy, chemodynamic therapy and synergistic therapy are highlighted.

Application of nanosonosensitizer materials in cancer sono-dynamic therapy

Sonodynamic therapy (SDT) is a novel non-invasive treatment for cancer combining low-intensity ultrasound and sonosensitizers. SDT activates sonosensitizers through ultrasound, releasing energy and generating reactive oxygen species to kill tumor cells. Compared with traditional photodynamic therapy (PDT), SDT is a promising anti-cancer therapy with the advantages of better targeting, deeper tissue penetration, and higher focusing ability. With the development and broad application of nanomaterials, novel sonosensitizers with tumor-targeting specificity can deliver to deep tumors and enhance the tumor microenvironment. In this review, we first review the mechanisms of sonodynamic therapy. In addition, we also focus on the current types of sonosensitizers and the latest design strategies of nanomaterials in sonosensitizers. Finally, we summarize the combined strategy of sonodynamic therapy.

Nanomedicines for Overcoming Cancer Drug Resistance

Clinically, cancer drug resistance to chemotherapy, targeted therapy or immunotherapy remains the main impediment towards curative cancer therapy, which leads directly to treatment failure along with extended hospital stays, increased medical costs and high mortality. Therefore, increasing attention has been paid to nanotechnology-based delivery systems for overcoming drug resistance in cancer. In this respect, novel tumor-targeting nanomedicines offer fairly effective therapeutic strategies for surmounting the various limitations of chemotherapy, targeted therapy and immunotherapy, enabling more precise cancer treatment, more convenient monitoring of treatment agents, as well as surmounting cancer drug resistance, including multidrug resistance (MDR). Nanotechnology-based delivery systems, including liposomes, polymer micelles, nanoparticles (NPs), and DNA nanostructures, enable a large number of properly designed therapeutic nanomedicines. In this paper, we review the different mechanisms of cancer drug resistance to chemotherapy, targeted therapy and immunotherapy, and discuss the latest developments in nanomedicines for overcoming cancer drug resistance.

Tumor Microenvironment Triggered the In Situ Synthesis of an Excellent Sonosensitizer in Tumor for Sonodynamic Therapy

An ultrasound-triggered sonodynamic therapy has shown great promise for cancer therapy. However, its clinical applications are very limited because the traditional sonosensitizers tend to suffer from very poor efficiency combined with low retention in cancer cells and low tumor selectivity. Therefore, sonosensitizers with higher effectivity, higher tumor cell retention, and higher tumor cell specificity are highly required. Herein, we constructed a Ti2C(OH)X nanosheet, which was a poor sonosensitizer but had a long circulation in the blood system. However, it was very interesting to find that the tumor microenvironment could in situ turn Ti2C(OH)X nanosheet into a novel and excellent sonosensitizer with a nanofiber structure in tumors, exhibiting excellent ability to generate reactive oxygen species (ROS) under ultrasound. Moreover, the nanofiber structure made it very difficult to get out of cancer cells, highly enhancing the retention of the sonosensitizer in the tumor, thereby enabling it to effectively and selectively kill cancer cells in vivo. Our findings demonstrate that the strategy of the tumor microenvironment triggering the in situ synthesis of an effective sonosensitizer in tumor provided a promising means to simultaneously increase the efficiency, sonosensitizer retention in cancer cells, and cancer selectivity, thereby effectively killing cancer cells but causing little damage to healthy tissues via the sonodynamic therapy.

Hydrogels for Antitumor and Antibacterial Therapy

As a highly absorbent and hydrophobic material with a three-dimensional network structure, hydrogels are widely used in biomedical fields for their excellent biocompatibility, low immunogenicity, adjustable physicochemical properties, ability to encapsulate a variety of drugs, controllability, and degradability. Hydrogels can be used not only for wound dressings and tissue repair, but also as drug carriers for the treatment of tumors. As multifunctional hydrogels are the focus for many researchers, this review focuses on hydrogels for antitumor therapy, hydrogels for antibacterial therapy, and hydrogels for co-use in tumor therapy and bacterial infection. We highlighted the advantages and representative applications of hydrogels in these fields and also outlined the shortages and future orientations of this useful tool, which might give inspirations for future studies.

Perfluorocarbon loaded fluorinated covalent organic polymers with effective sonosensitization and tumor hypoxia relief enable synergistic sonodynamic-immunotherapy

Relieving tumor hypoxia has recently been found to be a promising approach to reverse tumor immunosuppression and thus enhance the treatment outcomes of diverse cancer treatments. Herein, we prepared a type of fluorinated covalent conjugate polymers (COPs) with sonosensitizer meso-5, 10, 15, 20-tetra (4-hydroxylphenyl) porphyrin (THPP) and perfluorosebacic acid (PFSEA) as cross-linkers, yielding THPP_pf-COPs with efficient sonodynamic efficacy and loading capacity towards perfluoro-15-crown-5-ether (PFCE), a model perfluorocarbon molecule. Upon intratumoral injection, such PFCE@THPP_pf-COPs could not only attenuate tumor hypoxia, but also exhibit the most effective suppression effect on tumor growth in the presence of ultrasound exposure by inducing immunogenic cell death of cancer cells. Furthermore, we found that the sonodynamic therapy of PFCE@THPP_pf-COPs together with anti-CD47 immunotherapy would synergistically suppress tumor growth by increasing the tumor-infiltrating frequencies of phagocytic M1 macrophages and cytotoxic CD3⁺CD8⁺ T cells, while reducing the frequency of immunosuppressive regulatory T cells. Moreover, such combination treatment could also elicit potent protective memory antitumor immunity to prevent tumor challenge. Therefore, this work presents PFCE@THPP_pf-COPs are a type of multifunctional nano-sonosensitizers potent in removing negative impacts of inherent tumor hypoxia and immunosuppression, and suppressing tumor growth and tumor recurrence by priming host's antitumor immunity, particularly in synergizing with anti-CD47 immunotherapy.

SR-A-Targeted Nanoplatform for Sequential Photothermal/Photodynamic Ablation of Activated Macrophages to Alleviate Atherosclerosis

Cardiovascular and cerebrovascular diseases induced by atherosclerosis (AS) have become the dominant cause of disability and mortality throughout the world. The typical early pathological process of AS involves the activation of inflammatory macrophages in the vulnerable plaque. In this work, we first employed chitosan-coated carbon nanocages (CS-CNCs) as nanocarriers to load Chlorin e6 (Ce6) and then linked dextran sulfate (DS) to the outermost layer by electrostatic adsorption to create a multifunctional therapeutic nanoplatform, CS-CNCs@Ce6/DS. The DS of the nanoplatform can recognize and bind to the type A scavenger receptor (SR-A), which is expressed only on the activated macrophages of the arterial plaque, so the proposed nanoplatform selectively targets these macrophages and accumulates there. Furthermore, DS can competitively inhibit cellular endocytosis of oxidized low-density lipoproteins via blocking of SR-A. The rapid photothermal conversion capability of CS-CNCs enables efficient therapeutic delivery during photothermal therapy (PTT). Interestingly, near-infrared-accelerated drug release induced by initial 808-nm laser irradiation was observed, thus enhancing the Ce6 concentration in the atherosclerotic plaque area and the efficiency of photodynamic therapy (PDT). Sequential photothermal/photodynamic ablation of the activated macrophages reduced pro-inflammatory cytokine secretion and alleviated the proliferation and migration of smooth muscle cells. These finally resulted in the stabilization and shrinkage of atherosclerotic plaques, further inhibiting the development and exacerbation of AS. Therefore, this work achieved a "1 + 1 greater than 2" effect by providing a novel approach to the treatment of atherosclerotic plaques, which is promising for the prevention of AS-related diseases.