Pyroelectric Catalysis-Based "Nano-Lymphatic" Reduces Tumor Interstitial Pressure for Enhanced Penetration and Hydrodynamic Therapy

The application of nanomaterials in tumor therapy based on the regulation of mechanical properties

Mechanical properties, as crucial physical properties, have a significant impact on the occurrence, development, and metastasis of tumors. Regulating the mechanical properties of tumors to enhance their sensitivity to radiotherapy and chemotherapy has become an important strategy in the field of cancer treatment. Over the past few decades, nanomaterials have made remarkable progress in cancer therapy, either based on their intrinsic properties or as drug delivery carriers. However, the investigation of nanomaterials of mechanical regulation in tumor therapy is currently in its initial stages. The mechanical properties of nanomaterials themselves, drug carrier targeting, and regulation of the mechanical environment of tumor tissue have far-reaching effects on the efficient uptake of drugs and clinical tumor treatment. Therefore, this review aims to comprehensively summarize the applications and research progress of nanomaterials in tumor therapy based on the regulation of mechanical properties, in order to provide strong support for further research and the development of treatment strategies in this field.

Natural MOF-Like Photocatalytic Nanozymes Alleviate Tumor Pressure for Enhanced Nanodrug Penetration

In oncological nanomedicine, overcoming the dual-phase high interstitial pressure in the tumor microenvironment is pivotal for enhancing the penetration and efficacy of nanotherapeutics. The elevated tumor interstitial solid pressure (TISP) is largely attributed to the overaccumulation of collagen in the extracellular matrix, while the increased tumor interstitial fluid pressure (TIFP) stems from the accumulation of fluid due to the aberrant vascular architecture. In this context, metal-organic frameworks (MOFs) with catalytic efficiency have shown potential in degrading tumor interstitial components, thereby reducing interstitial pressure. However, the potential biotoxicity of the organic components of MOFs limits their clinical translation. To circumvent this, a MOF-like photocatalytic nanozyme, RPC@M, using naturally derived cobalt phytate (CoPA) and resveratrol (Res) is developed. This nanozyme not only facilitates the decomposition of water in the tumor interstitium under photoactivation to reduce TIFP, but also generates an abundance of reactive oxygen species through its peroxidase-like activity to exert cytotoxic effects on tumor cells. Moreover, Res contributes to the reduction of collagen deposition, thereby lowering TISP. The concurrent diminution of both TISP and TIFP by RPC@M leads to enhanced tumor penetration and potent antitumor activity, presenting an innovative approach in constructing tumor therapeutic nanozymes from natural products.

MXene-Mediated Catalytic Redox Reactions for Biomedical Applications

Reactive oxygen species (ROS) play a crucial role in orchestrating a myriad of physiological processes within living systems. With the advent of materdicine, an array of nanomaterials has been intricately engineered to influence the redox equilibrium in biological milieus, thereby pioneering a distinctive therapeutic paradigm predicated on ROS-centric biochemistry. Among these, two-dimensional carbides, nitrides, and carbonitrides, collectively known as MXenes, stand out due to their multi-valent and multi-elemental compositions, large surface area, high conductivity, and pronounced local surface plasmon resonance effects, positioning them as prominent contributors in ROS modulation. This review aims to provide an overview of the advancements in harnessing MXenes for catalytic redox reactions in various biological applications, including tumor, anti-infective, and anti-inflammatory therapies. The emphasis lies on elucidating the therapeutic mechanism of MXenes, involving both pro-oxidation and anti-oxidation processes, underscoring the redox-related therapeutic applications facilitated by self-catalysis, photo-excitation, and sono-excitation properties of MXenes. Furthermore, this review highlights the existing challenges and outlines future development trends in leveraging MXenes for ROS-involving disease treatments, marking a significant step towards the integration of these nanomaterials into clinical practice.

Piezoelectric Catalysis Induces Tumor Cell Senescence to Boost Chemo-Immunotherapy

Cellular senescence, a vulnerable state of growth arrest, has been regarded as a potential strategy to weaken the resistance of tumor cells, leading to dramatic improvements in treatment efficacy. However, a selective and efficient strategy for inducing local tumor cellular senescence has not yet been reported. Herein, piezoelectric catalysis is utilized to reduce intracellular NAD+ to NADH for local tumor cell senescence for the first time. In detail, a biocompatible nanomedicine (BTO/Rh-D@M) is constructed by wrapping the piezoelectric BaTiO3/(Cp*RhCl2)2 (BTO/Rh) and doxorubicin (DOX) in the homologous cytomembrane with tumor target. After tumors are stimulated by ultrasound, negative and positive charges are generated on the BTO/Rh by piezoelectric catalysis, which reduce the intracellular NAD+ to NADH for cellular senescence and oxidize H2O to reactive oxygen species (ROS) for mitochondrial damage. Thus, the therapeutic efficacy of tumor immunogenic cell death-induced chemo-immunotherapy is boosted by combining cellular senescence, DOX, and ROS. The results indicate that 23.9% of the piezoelectric catalysis-treated tumor cells senesced, and solid tumors in mice disappeared completely after therapy. Collectively, this study highlights a novel strategy to realize cellular senescence utilizing piezoelectric catalysis and the significance of inducing tumor cellular senescence to improve therapeutic efficacy.

Curvature-mediated rapid extravasation and penetration of nanoparticles against interstitial fluid pressure for improved drug delivery

Elevated interstitial fluid pressure (IFP) within pathological tissues (e.g., tumors, obstructed kidneys, and cirrhotic livers) creates a significant hindrance to the transport of nanomedicine, ultimately impairing the therapeutic efficiency. Among these tissues, solid tumors present the most challenging scenario. While several strategies through reducing tumor IFP have been devised to enhance nanoparticle delivery, few approaches focus on modulating the intrinsic properties of nanoparticles to effectively counteract IFP during extravasation and penetration, which are precisely the stages obstructed by elevated IFP. Herein, we propose an innovative solution by engineering nanoparticles with a fusiform shape of high curvature, enabling efficient surmounting of IFP barriers during extravasation and penetration within tumor tissues. Through experimental and theoretical analyses, we demonstrate that the elongated nanoparticles with the highest mean curvature outperform spherical and rod-shaped counterparts against elevated IFP, leading to superior intratumoral accumulation and antitumor efficacy. Super-resolution microscopy and molecular dynamics simulations uncover the underlying mechanisms in which the high curvature contributes to diminished drag force in surmounting high-pressure differentials during extravasation. Simultaneously, the facilitated rotational movement augments the hopping frequency during penetration. This study effectively addresses the limitations posed by high-pressure impediments, uncovers the mutual interactions between the physical properties of NPs and their environment, and presents a promising avenue for advancing cancer treatment through nanomedicine.

Highly Effective Pyroelectric Catalysis for Simultaneous Tumor-Targeted Dynamic Therapy and Gentle Photothermal Therapy by Oxygen-Vacancy-Rich CeO2-BaTiO3 Nanorods

Pyroelectric nanostructures can effectively generate temperature-mediated reactive oxygen species (ROS) through the pyroelectric effect, providing promise for treating hypoxic tumors; and therefore, the synergistic application of photothermal therapy (PTT) and pyroelectric dynamic therapy (PEDT) presents an intriguing approach for cancer therapy. However, this method still faces challenges in improving pyroelectric catalysis and achieving precise tumor localization. In this study, a nano-heterojunction based on CeO2-BaTiO3 nanorods (IR1061@PCBNR) is reported, which exhibits highly effective pyroelectric catalysis for simultaneous tumor-targeted dynamic therapy and gentle photothermal therapy through the utilization of the rich oxygen vacancies. The oxygen vacancies create active sites that facilitate the migration of pyroelectrically-induced charge carriers, improving charge separation and ROS generation. IR1061@PCBNR also demonstrates high tumor penetration; while, minimizing damage to normal cells. This precise nanomedicine strategy holds great potential for advancing dynamic cancer therapies by overcoming the limitations of conventional approaches.

Achieving deep intratumoral penetration and multimodal combined therapy for tumor through algal photosynthesis

BACKGROUND

Elevated interstitial fluid pressure within tumors, resulting from impaired lymphatic drainage, constitutes a critical barrier to effective drug penetration and therapeutic outcomes.

RESULTS

In this study, based on the photosynthetic characteristics of algae, an active drug carrier (CP@ICG) derived from Chlorella pyrenoidosa (CP) was designed and constructed. Leveraging the hypoxia tropism and phototropism exhibited by CP, we achieved targeted transport of the carrier to tumor sites. Additionally, dual near-infrared (NIR) irradiation at the tumor site facilitated photosynthesis in CP, enabling the breakdown of excessive intratumoral interstitial fluid by generating oxygen from water decomposition. This process effectively reduced the interstitial pressure, thereby promoting enhanced perfusion of blood into the tumor, significantly improving deep-seated penetration of chemotherapeutic agents, and alleviating tumor hypoxia.

CONCLUSIONS

CP@ICG demonstrated a combined effect of photothermal/photodynamic/starvation therapy, exhibiting excellent in vitro/in vivo anti-tumor efficacy and favorable biocompatibility. This work provides a scientific foundation for the application of microbial-enhanced intratumoral drug delivery and tumor therapy.

Tumor microenvironment reprogramming by nanomedicine to enhance the effect of tumor immunotherapy

With the rapid development of the fields of tumor biology and immunology, tumor immunotherapy has been used in clinical practice and has demonstrated significant therapeutic potential, particularly for treating tumors that do not respond to standard treatment options. Despite its advances, immunotherapy still has limitations, such as poor clinical response rates and differences in individual patient responses, largely because tumor tissues have strong immunosuppressive microenvironments. Many tumors have a tumor microenvironment (TME) that is characterized by hypoxia, low pH, and substantial numbers of immunosuppressive cells, and these are the main factors limiting the efficacy of antitumor immunotherapy. The TME is crucial to the occurrence, growth, and metastasis of tumors. Therefore, numerous studies have been devoted to improving the effects of immunotherapy by remodeling the TME. Effective regulation of the TME and reversal of immunosuppressive conditions are effective strategies for improving tumor immunotherapy. The use of multidrug combinations to improve the TME is an efficient way to enhance antitumor immune efficacy. However, the inability to effectively target drugs decreases therapeutic effects and causes toxic side effects. Nanodrug delivery carriers have the advantageous ability to enhance drug bioavailability and improve drug targeting. Importantly, they can also regulate the TME and deliver large or small therapeutic molecules to decrease the inhibitory effect of the TME on immune cells. Therefore, nanomedicine has great potential for reprogramming immunosuppressive microenvironments and represents a new immunotherapeutic strategy. Therefore, this article reviews strategies for improving the TME and summarizes research on synergistic nanomedicine approaches that enhance the efficacy of tumor immunotherapy.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Enhancing drug penetration in solid tumors via nanomedicine: Evaluation models, strategies and perspectives

Effective tumor treatment depends on optimizing drug penetration and accumulation in tumor tissue while minimizing systemic toxicity. Nanomedicine has emerged as a key solution that addresses the rapid clearance of free drugs, but achieving deep drug penetration into solid tumors remains elusive. This review discusses various strategies to enhance drug penetration, including manipulation of the tumor microenvironment, exploitation of both external and internal stimuli, pioneering nanocarrier surface engineering, and development of innovative tactics for active tumor penetration. One outstanding strategy is organelle-affinitive transfer, which exploits the unique properties of specific tumor cell organelles and heralds a potentially transformative approach to active transcellular transfer for deep tumor penetration. Rigorous models are essential to evaluate the efficacy of these strategies. The patient-derived xenograft (PDX) model is gaining traction as a bridge between laboratory discovery and clinical application. However, the journey from bench to bedside for nanomedicines is fraught with challenges. Future efforts should prioritize deepening our understanding of nanoparticle-tumor interactions, re-evaluating the EPR effect, and exploring novel nanoparticle transport mechanisms.

Piezoelectricity, Pyroelectricity, and Ferroelectricity in Biomaterials and Biomedical Applications

Piezoelectric, pyroelectric, and ferroelectric materials are considered unique biomedical materials due to their dielectric crystals and asymmetric centers that allow them to directly convert various primary forms of energy in the environment, such as sunlight, mechanical energy, and thermal energy, into secondary energy, such as electricity and chemical energy. These materials possess exceptional energy conversion ability and excellent catalytic properties, which have led to their widespread usage within biomedical fields. Numerous biomedical applications have demonstrated great potential with these materials, including disease treatment, biosensors, and tissue engineering. For example, piezoelectric materials are used to stimulate cell growth in bone regeneration, while pyroelectric materials are applied in skin cancer detection and imaging. Ferroelectric materials have even found use in neural implants that record and stimulate electrical activity in the brain. This paper reviews the relationship between ferroelectric, piezoelectric, and pyroelectric effects and the fundamental principles of different catalytic reactions. It also highlights the preparation methods of these three materials and the significant progress made in their biomedical applications. The review concludes by presenting key challenges and future prospects for efficient catalysts based on piezoelectric, pyroelectric, and ferroelectric nanomaterials for biomedical applications.

Cascaded Antitumor Therapy Excited by Dual Nanozymes Based on Energy Restriction and Photocatalysis

In nanocatalytic medicine, drugs can be transformed into toxic components through highly selective and highly specific catalytic reactions in the tumor microenvironment, avoiding toxic side effects on normal tissues. Due to the coexistence of Ce3+ and Ce4+, CeO2 is endowed with dual nanozyme activities. Herein, CeO2 nanoparticles served as templates to construct a biomimetic nanodrug delivery system (C/CeO2@M) by electrostatic adsorption of carbon quantum dots (CQDs) and coating a homologous tumor cytomembrane. After homologous targeting to tumors, the CQDs emitted 350-600 nm light under 660 nm laser irradiation by upconversion luminescence, which caused a CeO2-mediated photocatalytic reaction to generate reactive oxygen species. The catalase-like activity of CeO2-enabled converting excess H2O2 to O2, which not only alleviated tumor hypoxia and promoted intratumor drug delivery but also provided substrates for subsequent catalytic reactions. Meanwhile, the phosphatase activity of CeO2 could consume adenosine triphosphate (ATP) to block the energy supply for tumor cells, thus limiting cell proliferation and metastasis. The strategy of energy restriction and photocatalysis of dual nanozyme stimulation offers great potentials in enhancing drug penetration and eradicating solid tumors.

Self-triggered thermoelectric nanoheterojunction for cancer catalytic and immunotherapy

The exogenous excitation requirement and electron-hole recombination are the key elements limiting the application of catalytic therapies. Here a tumor microenvironment (TME)-specific self-triggered thermoelectric nanoheterojunction (Bi0.5Sb1.5Te3/CaO2 nanosheets, BST/CaO2 NSs) with self-built-in electric field facilitated charge separation is fabricated. Upon exposure to TME, the CaO2 coating undergoes rapid hydrolysis, releasing Ca2+, H2O2, and heat. The resulting temperature difference on the BST NSs initiates a thermoelectric effect, driving reactive oxygen species production. H2O2 not only serves as a substrate supplement for ROS generation but also dysregulates Ca2+ channels, preventing Ca2+ efflux. This further exacerbates calcium overload-mediated therapy. Additionally, Ca2+ promotes DC maturation and tumor antigen presentation, facilitating immunotherapy. It is worth noting that the CaO2 NP coating hydrolyzes very slowly in normal cells, releasing Ca2+ and O2 without causing any adverse effects. Tumor-specific self-triggered thermoelectric nanoheterojunction combined catalytic therapy, ion interference therapy, and immunotherapy exhibit excellent antitumor performance in female mice.

Ultrasound-Chargeable Persistent Luminescence Nanoparticles to Generate Self-Propelled Motion and Photothermal/NO Therapy for Synergistic Tumor Treatment

Cancer phototherapy indicates advantages in ease of manipulation, negligible drug resistance, and spatiotemporal control but is confronted with challenges in tumor cell accessibility and intermittent light excitation. Herein, we propose a strategy with persistent luminescence (PL)-excited photothermal therapy (PTT), concurrent thermophoresis-propelled motion, and PL-triggered NO release, where PL emission is chargeable by ultrasonication for readily applicable to deep tumors. Mechanoluminescent (ML) nanodots of SrAl2O4:Eu2+ (SAOE) and PL nanodots of ZnGa2O4:Cr3+ (ZGC) were deposited on mesoporous silicates to obtain mSZ nanoparticles (NPs), followed by partially coating with polydopamine (PDA) caps and loading NO donors to prepare Janus mSZ@PDA-NO NPs. The ML emission bands of SAOE nanodots overlap with the excitation band of ZGC, and the persistent near-infrared (NIR) emission could be repeatedly activated by ultrasonication. The PL emission acts as an internal NIR source to produce a thermophoretic force and NO gas propellers to drive the motion of Janus NPs. Compared with the commonly used intermittent NIR illumination at both 660 and 808 nm, the persistent motion of ultrasound-activated NPs enhances cellular uptake and long-lasting PTT and intracellular NO levels to combat tumor cells without the use of any chemotherapeutic drugs. The ultrasound-activated persistent motion promotes intratumoral accumulation and tumor distribution of PTT/NO therapeutics and exhibits significantly higher tumor growth inhibition, longer animal survival, and larger intratumoral NO levels than those who experience external NIR illumination. Thus, this study demonstrates a strategy to activate PL emissions and construct PL-excited nanomotors for phototherapy in deep tissues.

Photothermal Propelling and Pyroelectric Potential-Promoted Cell Internalization of Janus Nanoparticles and Pyroelectrodynamic Tumor Therapy

Cancer phototherapy experiences limitations in tissue diffusion and cell internalization of phototherapeutic agents and dose-dependent side effects. Herein, Janus pyroelectric nanoparticles (NPs) are designed to generate self-powered motion and built-in electric fields to overcome the delivery barriers. Polydopamine (PDA) layers are partially coated on tetragonal BaTiO3 (tBT) NPs to prepare Janus tBT@PDA, and Au NPs are deposited on the PDA caps to obtain Janus tBT@PDA-Au NPs. Near-infrared (NIR) illumination of tBT@PDA-Au builds in situ pyroelectric potentials on NPs, which selectively affect the membrane potential of tumor cells rather than normal cells to enhance tumor cell internalization and produce reactive oxygen species (ROS) for pyroelectric dynamic therapy (PEDT). The asymmetric photothermal effect of the Janus NPs creates thermophoretic force to propel NP motion, which enhances tumor diffusion and cellular uptake of NPs and boosts cytotoxicity and intracellular ROS levels. The inoculation of Au NPs increases the photothermal effect, exhibits larger motion velocities, produces higher pyroelectric potentials, and elevates cellular uptake rates, resulting in significant induction of tumor cell apoptosis, suppression of tumor growth, and extension of animal survival. Thus, the concise design of tBT@PDA-Au/NIR treatment has achieved thermophoretic motion-promoted tissue diffusion, built-in electric field-enhanced cell internalization, and photothermal/PEDT-synergized antitumor efficacy.

Bimodal Antimicrobial Surfaces of Phytic Acid-Prussian Blue Nanoparticles-Cationic Polymer Networks

Surface modification plays a pivotal role in tailoring the functionalities of a solid material. Introduction of antimicrobial function on material surfaces can provide additional protection against life-threatening bacterial infections. Herein, a simple and universal surface modification method based on surface adhesion and electrostatic interaction of phytic acid (PA) is developed. PA is first functionalized with Prussian blue nanoparticles (PB NPs) via metal chelation and then conjugates with cationic polymers (CPs) through electrostatic interaction. With the aid of surface adherent PA and gravitation effect, the as-formed PA-PB-CP network aggregates are deposited on the solid materials in a substrate-independent manner. Synergistic bactericidal effects of "contact-killing" induced by the CPs and localized photothermal effect caused by the PB NPs endow the substrates with strong antibacterial performance. Membrane integrity, enzymatic activity, and metabolism function of the bacteria are disturbed in contact with the PA-PB-CP coating under near-infrared (NIR) irradiation. The PA-PB-CP modified biomedical implant surfaces exhibit good biocompatibility and synergistic antibacterial effect under NIR irradiation, and eliminate the adhered bacteria both in vitro and in vivo.

Multifunctional manganese oxide-based nanocomposite theranostic agent with glucose/light-responsive singlet oxygen generation and dual-modal imaging for cancer treatment

Development of tumor microenvironment (TME) modifying nanomedicine with cooperative effect between multiple stimuli responsive therapeutic modalities is necessary to achieve lower dosage induced tumor specific therapy. Accordingly, herein, a multifunctional MnOx NSs@BSA-IR780-GOx nanocomposite (MBIG NCs) is developed to modulate the oxidative stress in TME, and thus attain higher therapeutic efficacy. In the presence of glucose, the as-synthesized MBIG NCs are served as a chemodynamic agents and generated reactive oxygen species (ROS) by self-activation through a cascade of reactions from glucose oxidase (GOx) and manganese oxide nanosheets (MnOx NSs). Also, the MBIG NCs demonstrated excellent photodynamic properties upon irradiation with 808 nm laser owing to the presence of IR780. The combination of glucose-mediated chemodynamic and light-mediated photodynamic properties generated higher ROS than that obtained with individual stimuli. Further, the MBIG NCs exhibited photothermal effect with conversion efficiency of 33.8 %, which helped to enhance the enzymatic activities. In in vitro studies, the MBIG NCs exhibited good biocompatibility to cancerous and non-cancerous cells under non-stimulus conditions. Nevertheless, in the presence of glucose and light stimuli, they triggered more than 90 % cell toxicity at 200 ppm concentration via the cooperative effect between starvation therapy, chemodynamic therapy, and phototherapy. Furthermore, the MBIG NCs demonstrated magnetic resonance and fluorescence imaging properties. These results are suggesting that MBIG NCs would be potential theranostic agents to for cancer diagnosis and target specific therapy. More importantly, the fabrication process is paving a way to improve the aqueous dispersibility, stability, and bio-applicability of MnOx NSs and IR780.

The fundamentals and applications of piezoelectric materials for tumor therapy: recent advances and outlook

Malignant tumors are one of the main diseases leading to death, and the vigorous development of nanotechnology has opened up new frontiers for antitumor therapy. Currently, researchers are focused on solving the biomedical challenges associated with traditional anti-tumor medical methods, promoting the research and development of nano-drug carriers and new nano-drugs, which brings great hope for improving the curative effect and reducing toxic and side effects. Among the new systems being investigated, piezoelectric nano biomaterials, including ferroelectrics, piezoelectric and pyroelectric materials, have recently received extensive attention for antitumor applications. By coupling force, light, magnetism or heat and electricity, polarized charges are generated in these materials microscopically, forming a piezo-potential and establishing a built-in electric field. Polarized charges can directly act on the materials in the tumor micro-environment and also assist in the separation of carriers and inhibit recombination based on piezoelectric theory and piezoelectric optoelectronic theory. Based on this, piezoelectric materials convert various forms of primary energy (such as light energy, mechanical energy, thermal energy and magnetic energy) from the surrounding environment into secondary energy (such as electrical energy and chemical energy). Herein, we review the basic theory and principles of piezoelectric materials, pyroelectric materials and ferroelectric materials as nanomedicine. Then, we summarize the types of piezoelectric materials reported to date and their wide applications in treatment, imaging, device construction and probe detection in various tumor treatment fields. Based on this, we discuss the relevant characteristics and post-processing strategies of nano piezoelectric biomaterials to obtain the maximum piezoelectric response. Finally, we present the key challenges and future prospects for the development of ferroelectric, piezoelectric and pyroelectric nanomaterial-based nanoagents for efficient energy harvesting and conversion for desirable therapeutic outcomes.

Pyroelectric Janus nanomotors for synergistic electrodynamic-photothermal-antibiotic therapies of bacterial infections

Antibacterial electrotherapy is currently activated by external electric field or self-powered generators, but usually needs complicated power management circuits. Herein, near-infrared illumination (NIR) of pyroelectric nanoparticles (NPs) produces a built-in electric field to address the effectiveness and safety concerns in the antibacterial treatment. Janus tBT@PDA NPs were obtained by capping polydopamine (PDA) on tetragonal BaTiO₃ (tBT) NPs through defining the polymerization time, followed by ciprofloxacin (CIP) loading on the PDA caps to fabricate Janus tBT@PDA-Cip NPs. NIR illumination of PDA caps creates temperature variations on tBT NPs to generate photothermal and pyroelectric effects. Finite element simulation reveals a pyroelectric potential of over 1 V and sufficient reactive oxygen species (ROS) are produced to exhibit pyroelectric dynamic therapy (PEDT). The elevated temperature on one side of the Janus NPs produces thermophoretic force to drive NP motion, which enhances interactions with bacteria and overcomes limitations in the short action distance and lifespan of ROS. The pyroelectric field accelerates CIP release through weakening the π-π stacking and electrostatic interaction with PDA and also interrupts membrane potentials of bacteria to enhance CIP invasion into bacteria. The synergistic antibacterial effect of pyroelectric tBT@PDA-Cip NPs causes the fully recovery of S. aureus-infected skin wounds and regeneration of intact epidermis, blood vessels and hair follicles, while no obvious pathological change or inflammatory lesion is detected in the major organs. Thus, the pyroelectric Janus nanomotors demonstrate synergistic PEDT/photothermal/antibiotic effects to enhance antibacterial efficacy while avoiding the necessity of excessive heat, ROS and antibiotic doses. STATEMENT OF SIGNIFICANCE: Antibacterial treatment is challenged by antibiotics-derived side effects and the evolution of resistant strains. Phototherapy is commonly associated with excessive heat and oxidative stress, and their combinations with other agents are especially encouraged to strengthen antibacterial efficacy while alleviating the associated side effects. Electric field is another activator to generate antibacterial abilities, but usually requires complicated power management and bulk electrodes, making it inconvenient in a biological setup. To address these challenges, we propose a strategy to generate microelectric field on nanoparticles themselves and achieve synergistic electrodynamic-photothermal-antibiotic therapies. The pyroelectric effect weakens interactions between nanoparticles and antibiotics to accelerate drug release, and the built-in pyroelectric field increases membrane fluidity to enhance bacterial uptake of antibiotics.

Rational Design of Biomaterials to Potentiate Cancer Thermal Therapy

Cancer thermal therapy, also known as hyperthermia therapy, has long been exploited to eradicate mass lesions that are now defined as cancer. With the development of corresponding technologies and equipment, local hyperthermia therapies such as radiofrequency ablation, microwave ablation, and high-intensity focused ultrasound, have has been validated to effectively ablate tumors in modern clinical practice. However, they still face many shortcomings, including nonspecific damages to adjacent normal tissues and incomplete ablation particularly for large tumors, restricting their wide clinical usage. Attributed to their versatile physiochemical properties, biomaterials have been specially designed to potentiate local hyperthermia treatments according to their unique working principles. Meanwhile, biomaterial-based delivery systems are able to bridge hyperthermia therapies with other types of treatment strategies such as chemotherapy, radiotherapy and immunotherapy. Therefore, in this review, we discuss recent progress in the development of functional biomaterials to reinforce local hyperthermia by functioning as thermal sensitizers to endow more efficient tumor-localized thermal ablation and/or as delivery vehicles to synergize with other therapeutic modalities for combined cancer treatments. Thereafter, we provide a critical perspective on the further development of biomaterial-assisted local hyperthermia toward clinical applications.

Polysaccharide-based nanocarriers for efficient transvascular drug delivery

Polysaccharide-based nanocarriers (PBNs) are the focus of extensive investigation because of their biocompatibility, low cost, wide availability, and chemical versatility, which allow a wide range of anticancer agents to be loaded within the nanocarriers. Similar to other nanocarriers, most PBNs are designed to extravasate out of tumor vessels, depending on the enhanced permeability and retention (EPR) effect. However, the EPR effect is compromised in some tumors due to the heterogeneity of tumor structures. Transvascular transport efficacy is decreased by complex blood vessels and condensed tumor stroma. The limited extravasation impedes efficient drug delivery into tumor parenchyma, and thus affects the subsequent tumor accumulation, which hinders the therapeutic effect of PBNs. Therefore, overcoming the biological barriers that restrict extravasation from tumor vessels is of great importance in PBN design. Many strategies have been developed to enhance the EPR effect that involve nanocarrier property regulation and tumor structure remodeling. Moreover, some researchers have proposed active transcytosis pathways that are complementary to the paracellular EPR effect to increase the transvascular extravasation efficiency of PBNs. In this review, we summarize the recent advances in the design of PBNs with enhanced transvascular transport to enable optimization of PBNs in the extravasation of the drug delivery process. We also discuss the obstacles and challenges that need to be addressed to clarify the transendothemial mechanism of PBNs and the potential interactions between extravasation and other drug delivery steps.

Enzyme-Triggered Size-Switchable Nanosystem for Deep Tumor Penetration and Hydrogen Therapy

The poor penetration of nanocarriers within tumor dense extracellular matrices (ECM) greatly restricts the access of anticancer drugs to the deep tumor cells, resulting in low therapeutic efficacy. Moreover, the high toxicity of the traditional chemotherapeutics inevitably causes undesirable side effects. Herein, taking the advantages of biosafe H₂ and small-sized nanoparticles in diffusion within tumor ECM, we develop a matrix metalloprotease 2 (MMP-2) responsive size-switchable nanoparticle (UAMSN@Gel-PEG) that is composed of ultrasmall amino-modified mesoporous silica nanoparticles (UAMSN) wrapped within a PEG-conjugated gelatin to deliver H₂ to the deep part of tumors for effective gas therapy. Ammonia borane (AB) is chosen as the H₂ prodrug that can be effectively loaded into UAMSN by hydrogen-bonding adsorption. Gelatin is used as the substrate of MMP-2 to trigger size change and block AB inside UAMSN during blood circulation. PEG is introduced to further increase the particle size and endow the nanoparticle with long blood circulation to achieve effective tumor accumulation via the EPR effect. After accumulation into the tumor site, MMP-2 promptly digests gelatin to expose UAMSN loading AB for deep tumor penetration. Upon stimulation by the acidic tumor microenvironment, AB decomposes into H₂ for further intratumor diffusion to achieve effective hydrogen therapy. Consequently, such a simultaneous deep tumor penetration of nanocarriers and H₂ results in an evident suppression on tumor growth in a 4T1 tumor-bearing model without any obvious toxicity on normal tissues. Our synthetic nanosystem provides a promising strategy for the development of nanomedicines with enhanced tumor permeability and good biosafety for efficient tumor treatment.

Highly Efficient Flexocatalysis of Two-Dimensional Semiconductors

Catalysis is vitally important for chemical engineering, energy, and environment. It is critical to discover new mechanisms for efficient catalysis. For piezoelectric/pyroelectric/ferroelectric materials that have a non-centrosymmetric structure, interfacial polarization-induced redox reactions at surfaces leads to advanced mechanocatalysis. Here, the first flexocatalysis for 2D centrosymmetric semiconductors, such as MnO₂  nanosheets, is demonstrated largely expanding the polarization-based-mechanocatalysis to 2D centrosymmetric materials. Under ultrasonic excitation, the reactive species are created due to the strain-gradient-induced flexoelectric polarization in MnO₂  nanosheets composed nanoflowers. The organic pollutants (Methylene Blue et al.) can be effectively degraded within 5 min; the performance of the flexocatalysis is comparable to that of state-of-the-art piezocatalysis, with excellent stability and reproducibility. Moreover, the factors related to flexocatalysis such as material morphology, adsorption, mechanical vibration intensity, and temperature are explored, which give deep insights into the mechanocatalysis. This study opens the field of flexoelectric effect-based mechanochemistry in 2D centrosymmetric semiconductors.

Cold Nanozyme for Precise Enzymatic Antitumor Immunity

Precise catalysis is pursued for the biomedical applications of artificial enzymes. It is feasible to precisely control the catalysis of artificial enzymes via tunning the temperature-dependent enzymatic kinetics. The safety window of cold temperatures (4-37 °C) for the human body is much wider than that of thermal temperatures (37-42 °C). Although the development of cold-activated artificial enzymes is promising, there is currently a lack of suitable candidates. Herein, a cold-activated artificial enzyme is presented with Bi₂Fe₄O₉ nanosheets (NSs) as a paradigm. The as-obtained Bi₂Fe₄O₉ NSs possess glutathione oxidase (GSHOx)-like activity under cold temperature due to their pyroelectricity. Bi₂Fe₄O₉ NSs trigger the cold-enzymatic death of tumor cells via apoptosis and ferroptosis, and minimize the off-target toxicity to normal tissues. Moreover, an interventional device is fabricated to intelligently and remotely control the enzymatic activity of Bi₂Fe₄O₉ NSs on a smartphone. With Bi₂Fe₄O₉ NSs as an in situ vaccine, systemic antitumor immunity is successfully activated to suppress tumor metastasis and relapse. Moreover, blood biochemistry analysis and histological examination indicate the high biosafety of Bi₂Fe₄O₉ NSs for in vivo applications. This cold nanozyme provides a strategy for cancer vaccines, which can benefit the precise control over catalytic nanomedicines.

Ultrasmall AgBiSe2 nanodots for CT/thermal imaging-guided photothermal tumor therapy in the NIR-II biowindow

Stimulus-responsive ternary chalcogenide nanomaterials are regarded as promising 'all-in-one' nanotheranostics agents on account of their tunable band structures and multi-metal intrinsic properties. Herein, ultrasmall AgBiSe₂ nanodots are prepared by a simple thermal injection method. It shows a narrow band gap of 0.91 eV and high absorption coefficient in the NIR-II biowindow, resulting in excellent photothermal performance. Under the irradiation of a 1064 nm laser, AgBiSe₂ can induce the overexpression of intracellular heat shock protein (Hsp70) and cell apoptosis to inhibit the growth of tumor cells. The strong signal from CT/thermal imaging also provides guidance for tumor diagnosis. Importantly, AgBiSe₂ can be rapidly excreted from the body, thus avoiding long term toxicity. This study presents the first biomedical application of AgBiSe₂ nanodots in cancer treatment and extends the development of ternary chalcogenide-based semiconductor nanomedicine.

Matrix Metalloproteinase-2-Responsive Surface-Changeable Liposomes Decorated by Multifunctional Peptides to Overcome the Drug Resistance of Triple-Negative Breast Cancer through Enhanced Targeting and Penetrability

Although nanomedicine has demonstrated great potential for combating drug resistance, its suboptimal recognition of malignant cells and limited transport across multiple biological obstacles seriously impede the efficacious accumulation of drugs in tumor lesions, which strikingly limits its application in the clinical therapy of drug-resistant triple-negative breast cancer (TNBC). Hence, a surface-variable drug delivery vehicle based on the modification of liposomes with a multifunctional peptide (named EMC) was fabricated in this work and used for encapsulating doxorubicin and the p-glycoprotein inhibitor tariquidar. This EMC peptide contains an EGFR-targeting bullet that was screened from a "one-bead one-compound" combinatorial library, an MMP-2-cleaved substrate, and a cell-penetrating segment. The EGFR-targeting sequence has been validated to possess excellent specificity and affinity for EGFR at both the cellular and molecular levels and could be unloaded from the EMC peptide by MMP-2 in the tumor microenvironment. This doxorubicin/tariquidar-coloaded and peptide-functionalized liposome (DT-pLip) exhibited superior efficacy in tumor growth inhibition to drug-resistant TNBC both in vitro and in vivo through EGFR targeting, osmotic enhancement in response to MMP-2, controllable release, and inhibited efflux. Consequently, our systematic studies indicated the potential of this liposome-based nanoplatform in the therapy of drug-resistant TNBC through targeting effects and tumor microenvironment-triggered penetration enhancement.

Cold-catalytic antitumor immunity with pyroelectric black phosphorus nanosheets

Catalytic nanomedicine with the innate features of catalysts brings incomparable properties to biomedicine over traditional drugs. The temperature-dependent activity of catalysts provides catalytic nanomedicines with a facile strategy to control their therapeutic performance. Tuning catalytic nanomedicine by cold treatment (4-37 °C) is safe and desired for practical applications, but there is a lack of cold-catalytic platforms. Herein, with black phosphorus (BP) as a model pyroelectric nanocatalyst, we explored the potential of cold-catalysts for antitumor therapy. BP nanosheets with pyro-catalytic activity catalyze the generation of oxidative stress to activate antitumor immunity under cold treatment. Due to the cold-catalytic immunomodulation, immune memory was successfully achieved to prevent tumor metastasis and recurrence. Considering the safety and conductive depth (>10 mm) of cold in the body, pyroelectric nanocatalysts open up exciting opportunities for the development of cold-catalytic nanomedicine.

Enhanced delivery of theranostic liposomes through NO-mediated tumor microenvironment remodeling

Highly efficient delivery of nanoagents to the tumor region remains the primary challenge for cancer nanomedicine. Herein, we propose a NO-mediated tumor microenvironment (TME) remodeling strategy for the high-efficient delivery of nanoagents into tumor. Quantum dots (QDs) with bright fluorescence in the near-infrared IIb (NIR-IIb, 1500-1700 nm) window and high photothermal conversion efficiency were encapsulated into liposomes for the imaging-guided photothermal therapy (PTT) of tumor. The fabrication of PEG and arginine-glycine-aspartate (RGD) peptide on liposomes ensured the prolonged circulation in vivo and active targeting to tumor. Moreover, the loading of a natural NO generator L-arginine in liposomes realized the continuous generation of NO in the acidic TME. By co-localization fluorescence imaging and western blot of tumor tissue, we confirmed that the release of NO activated the expression of metalloproteinases in TME and further degraded Collagen I in the peripheral region of the tumor, thus removing the barrier for the permeation of liposomes. Attributed to the enhanced accumulation of liposomes inside the tumor, NIR IIb imaging-guided PTT was achieved with remarkable therapeutic efficacy.

Nanotechnology-based combinatorial phototherapy for enhanced cancer treatment

Nanotechnology-based phototherapy has attracted enormous attention to cancer treatment owning to its non-invasiveness, high controllability and accuracy. Given the fast development of anti-tumor strategies, we summarize various examples of multifunctional nanosystems to highlight the recent advances in nanotechnology-based combinatorial phototherapy towards improving cancer treatment. The limitations of the monotherapeutic approach and the superiority of the photo-involved combinatorial strategies are discussed in each part. The future breakthroughs and clinical perspectives of combinatorial phototherapy are also outlooked. Our perspectives may inspire researchers to develop more effective phototherapy-based cancer-treating approaches.

Unveiling Mechanism of Organic Photogenerator for Hydroxyl Radicals Generation by Molecular Modulation

Photodynamic therapy (PDT) with organic photosensitizers generally goes through the oxygen-dependent process, generating singlet oxygen and/or superoxide anion. However, the generation of reactive oxygen species is often suppressed as a result of hypoxia, one of the common features in tumors, therefore limiting the effectiveness of the tumor treatments. Consequently, it is urgent and significant to develop an oxygen-independent hydroxyl radical photogenerator and unveil the mechanism. In this work, a hydroxyl radical (·OH) photogenerator originating from the electron transfer process is engineered. Detailed mechanism studies reveal that the optimized photosensitizer, WS2D, which contains a bithiophene unit, could both promote charge carrier generation and accelerate reaction efficiency, resulting in the efficient production of ·OH. In addition, WS2D nanoparticles are constructed to improve the polydispersity and stability in aqueous solution, which exhibit excellent biocompatibility and mitochondrial targeting. Bearing the above advantages, WS2D is employed in phototheranostics, which could release ·OH effectively and damage mitochondria precisely, achieving high PDT efficiency in vitro and in vivo. Overall, this work successfully provides valuable insights into the structural design of a hydroxyl radicals (·OH) photogenerator with great practical perspectives.

Strong π-π Stacking Stabilized Nanophotosensitizers: Improving Tumor Retention for Enhanced Therapy for Large Tumors in Mice

Conventional photosensitizers (PSs) often show poor tumor retention and are rapidly cleared from the bloodstream, which is one of the key hindrances to guarantee precise and efficient photodynamic therapy (PDT) in vivo. In this work, a photosensitizer assembly nanosystem that sharply enhances tumor retention up to ≈10 days is present. The PSs are synthesized by meso-substituting anthracene onto a BODIPY scaffold (AN-BDP), which then self-assembles into stable nanoparticles (AN-BDP NPs) with amphiphilic block copolymers due to the strong intermolecular π-π interaction of the anthracene. Additionally, the incorporated anthracene excites the PSs, producing singlet oxygen under red-light irradiation. Although AN-BDP NPs can completely suppress regular test size tumors (≈100 mm³ ) by one-time radiation, only 12% tumor growth inhibition rate is observed in the case of large-size tumors (≈350 mm³ ) under the same conditions. Due to the long-time tumor retention, AN-BDP NPs allow single-dose injection and three-time light treatments, resulting in an inhibition rate over 90%, much more efficient than single-time radiation of conventional clinically used PSs including chlorin-e6 (Ce6) and porphyrin with poor tumor retention. The results reveal the importance of long tumor retention time of PSs for efficient PDT, which can accelerate the clinical development of nanophotosensitizers.

Engineering Electronic Band Structure of Binary Thermoelectric Nanocatalysts for Augmented Pyrocatalytic Tumor Nanotherapy

Photothermal therapy (PTT) has emerged as a distinct therapeutic modality owing to its noninvasiveness and spatiotemporal selectivity. However, heat-shock proteins (HSPs) endow tumor cells with resistance to heat-induced apoptosis, severely lowering the therapeutic efficacy of PTT. Here, a high-performance pyroelectric nanocatalyst, Bi₁₃ S₁₈ I₂ nanorods (NRs), with prominent pyroelectric conversion and photothermal conversion performance for augmented pyrocatalytic tumor nanotherapy, is developed. Canonical binary compounds are reconstructed by inserting a third biocompatible agent, thus facilitating the formation of Bi₁₃ S₁₈ I₂ NRs with enhanced pyrocatalytic conversion efficiency. Under 808 nm laser irradiation, Bi₁₃ S₁₈ I₂ NRs induce a conspicuous temperature elevation for photonic hyperthermia. In particular, Bi₁₃ S₁₈ I₂ NRs harvest pyrocatalytic energy from the heating and cooling alterations to produce abundant reactive oxygen species, which results in the depletion of HSPs and hence the reduction of thermoresistance of tumor cells, thereby significantly augmenting the therapeutic efficacy of photothermal tumor hyperthermia. By synergizing the pyroelectric dynamic therapy with PTT, tumor suppression with a significant tumor inhibition rate of 97.2% is achieved after intravenous administration of Bi₁₃ S₁₈ I₂ NRs and subsequent exposure to an 808 nm laser. This work opens an avenue for the design of high-performance pyroelectric nanocatalysts by reconstructing canonical binary compounds for therapeutic applications in biocatalytic nanomedicine.

Multifunctional Nanosystems with Enhanced Cellular Uptake for Tumor Therapy

Rapid development of nanotechnology provides promising strategies in biomedicine, especially in tumor therapy. In particular, the cellular uptake of nanosystems is not only a basic premise to realize various biomedical applications, but also a fatal factor for determining the final therapeutic effect. Thus, a systematic and comprehensive summary is necessary to overview the recent research progress on the improvement of nanosystem cellular uptake for cancer treatment. According to the process of nanosystems entering the body, they can be classified into three categories. The first segment is to enhance the accumulation and permeation of nanosystems to tumor cells through extracellular microenvironment stimulation. The second segment is to improve cellular internalization from extracellular to intracellular via active targeting. The third segment is to enhance the intracellular retention of therapeutics by subcellular localization. The major factors in the delivery can be utilized to develop multifunctional nanosystems for strengthening the tumor therapy. Ultimately, the key challenges and prospective in the emerging research frontier are thoroughly outlined. This review is expected to provide inspiring ideas, promising strategies and potential pathways for developing advanced anticancer nanosystems in clinical practice.