Co₉ Se₈ nanoplates as a new theranostic platform for photoacoustic/magnetic resonance dual-modal-imaging-guided chemo-photothermal combination therapy

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.

Theoretical simulation and experimental design of selenium and gold incorporated polymer-based microcarriers for ROS-mediated combined photothermal therapy

Recently, multi-modal combined photothermal therapy (PTT) with the use of photo-active materials has attracted significant attention for cancer treatment. However, drug carriers enabling efficient heating at the tumor site are yet to be designed: this is a fundamental requirement for broad implementation of PTT in clinics. In this work, we design and develop hybrid carriers based on multilayer capsules integrated with selenium nanoparticles (Se NPs) and gold nanorods (Au NRs) to realize reactive oxygen species (ROS)-mediated combined PTT. We show theoretically and experimentally that cooperative interaction of Se NPs with Au NRs improves the heat release efficiency of the developed capsules. In addition, after uptake by tumor cells, intracellular ROS level amplified by Se NPs inhibits the tumor growth. As a consequence, the synergy between Se NPs and Au NRs exhibits the advantages of hybrid carriers such as (i) improved photothermal conversion efficiency and (ii) dual-therapeutic effect. The results of in vitro and in vivo experiments demonstrate that the combination of ROS-mediated therapy and PTT has a higher tumor inhibition efficiency compared to the single-agent treatment (using only Se-loaded or Au-loaded capsules). Furthermore, the developed hybrid carriers show negligible in vivo toxicity towards major organs such as the heart, lungs, liver, kidneys and spleen. This study not only provides a potential strategy for the design of multifunctional "all-in-one" carriers, but also contributes to the development of combined PTT in clinical practice.

Thermal Stability and Sublimation of Two-Dimensional Co9Se8 Nanosheets for Ultrathin and Flexible Nanoelectronic Devices

An understanding of the structural and compositional stability of nanomaterials is significant from both fundamental and technological points of view. Here, we investigate the thermal stability of half-unit-cell thick two-dimensional (2D) Co₉Se₈ nanosheets that are exceptionally interesting because of their half-metallic ferromagnetic properties. By employing in situ heating in the transmission electron microscope (TEM), we find that the nanosheets show good structural and chemical stability without changes to the cubic crystal structure until sublimation of the nanosheets starts at temperatures between 460 and 520 °C. The real-time observations of the sublimation process show preferential removal at {110} type crystal facets. From an analysis of sublimation rates at various temperatures, we find that the sublimation occurs through noncontinuous and punctuated mass loss at lower temperatures while the sublimation is continuous and uniform at higher temperatures. Our findings provide an understanding of the nanoscale structural and compositional stability of 2D Co₉Se₈ nanosheets, which is of importance for their reliable application and sustained performance as ultrathin and flexible nanoelectronic devices.

Platinum(II)-Metallaclip-Based Theranostics for Cell Imaging and Synergetic Chemotherapy-Photodynamic Therapy

Supramolecular coordination complexes formed by coordination-induced assembly not only avoid the loss of activity of precursors but also provide an efficient way for controlled release, which can be further used in various fields of biology such as drug delivery, cell imaging, and tumor treatment. In this work, a Pt^II metallaclip (4) was prepared from 4-[4-(1,2,2-triphenylvinyl)phenyl]pyridine (1), 5,10,15-triphenyl-20-(pyridin-4-yl)porphyrin (2), 90^o Pt, and glycol-chain-modified isophthalic acid (3) in an acetone/water mixture through the "coordination-driven self-assembly" method. ³¹P and ¹H NMR spectroscopy and high-resolution mass spectrometry were used to characterize the obtained metallaclip 4. 4 can self-assemble into fluorescent nanostructures in aqueous solution because of the tetraphenylethylene unit and its amphiphilic nature. Importantly, the fluorescent nanoparticles not only can be employed for cell imaging but also can generate singlet oxygen (¹O₂) under 660 nm laser irradiation and the release of Pt drug in the tumor issue for cancer therapy. The work may provide a new way for scientists to construct functional biomaterials with multiple applications via molecular self-assembly.

Recent Advances in Contrast-Enhanced Photoacoustic Imaging: Overcoming the Physical and Practical Challenges

For decades now, photoacoustic imaging (PAI) has been investigated to realize its potential as a niche biomedical imaging modality. Despite its highly desirable optical contrast and ultrasonic spatiotemporal resolution, PAI is challenged by such physical limitations as a low signal-to-noise ratio (SNR), diminished image contrast due to strong optical attenuation, and a lower-bound on spatial resolution in deep tissue. In addition, contrast-enhanced PAI has faced practical limitations such as insufficient cell-specific targeting due to low delivery efficiency and difficulties in developing clinically translatable agents. Identifying these limitations is essential to the continuing expansion of the field, and substantial advances in developing contrast-enhancing agents, complemented by high-performance image acquisition systems, have synergistically dealt with the challenges of conventional PAI. This review covers the past four years of research on pushing the physical and practical challenges of PAI in terms of SNR/contrast, spatial resolution, targeted delivery, and clinical application. Promising strategies for dealing with each challenge are reviewed in detail, and future research directions for next generation contrast-enhanced PAI are discussed.

Advances in Single-component inorganic nanostructures for photoacoustic imaging guided photothermal therapy

Phototheranostic based on photothermal therapy (PTT) and photoacoustic imaging (PAI), as one of avant-garde medical techniques, have sparked growing attention because it allows noninvasive, deeply penetrative, and highly selective and effective therapy. Among a variety of phototheranostic nanoagents, single-component inorganic nanostructures are found to be novel and attractive PAI and PTT combined nanotheranostic agents and received tremendous attention, which not only exhibit structural controllability, high tunability in physiochemical properties, size-dependent optical properties, high reproducibility, simple composition, easy functionalization, and simple synthesis process, but also can be endowed with multiple therapeutic and imaging functions, realizing the superior therapy result along with bringing less foreign materials into body, reducing systemic side effects and improving the bioavailability. In this review, according to their synthetic components, conventional single-component inorganic nanostructures are divided into metallic nanostructures, metal dichalcogenides, metal oxides, carbon based nanostructures, upconversion nanoparticles (UCNPs), metal organic frameworks (MOFs), MXenes, graphdiyne and other nanostructures. On the basis of this category, their detailed applications in PAI guide PTT of tumor treatment are systematically reviewed, including synthesis strategies, corresponding performances, and cancer diagnosis and therapeutic efficacy. Before these, the factors to influence on photothermal effect and the principle of in vivo PAI are briefly presented. Finally, we also comprehensively and thoroughly discussed the limitation, potential barriers, future perspectives for research and clinical translation of this single-component inorganic nanoagent in biomedical therapeutics.

Multifunctional Mesoporous Hollow Cobalt Sulfide Nanoreactors for Synergistic Chemodynamic/Photodynamic/Photothermal Therapy with Enhanced Efficacy

The unique tumor microenvironment (TME) characteristic of severe hypoxia, overexpressed intracellular glutathione (GSH), and elevated hydrogen peroxide (H₂O₂) concentration limit the anticancer effect by monotherapy. In this report, glucose oxidase (GOx)-encapsulated mesoporous hollow Co₉S₈ nanoreactors are constructed with the coverage of polyphenol diblock polymers containing poly(oligo(ethylene glycol) methacrylate) and dopamine moieties containing methacrylate polymeric block, which are termed as GOx@PCoS. After intravenous injection, tumor accumulation, and cellular uptake, GOx@PCoS deplete GSH by Co³⁺ ions. GOx inside the nanoreactors produce H₂O₂ via oxidation of glucose to enhance •OH-based chemodynamic therapy (CDT) through the Fenton-like reaction under the catalysis of Co²⁺. Moreover, Co³⁺ ions possess catalase activity to catalyze production of O₂ from H₂O₂ to relieve tumor hypoxia. Upon 808 nm laser irradiation, GOx@PCoS exhibit photothermal and photodynamic effects with a high photothermal conversion efficiency (45.06%) and generation capacity of the toxic superoxide anion (•O₂^-) for photothermal therapy (PTT) and photodynamic therapy (PDT). The synergetic antitumor effects can be realized by GSH depletion, starvation, and combined CDT, PTT, and PDT with enhanced efficacy. Notably, GOx@PCoS can also be used as a magnetic resonance imaging (MRI) contrast agent to monitor the antitumor performance. Thus, GOx@PCoS show great potentials to effectively modulate TME and perform synergistic multimodal therapy.

Photothermal effects of CuS-BSA nanoparticles on H22 hepatoma-bearing mice

The objective of this study was to evaluate the in vivo application and photothermal ablation effects and mechanism of copper sulfide nanoparticles (CuS NPs) in hepatocellular carcinoma (HCC). Sheet-like CuS-BSA NPs with a particle size of 30 nm were synthesized using bovine serum albumin (BSA) as a biological modifier, and were physically characterized. To provide a reference range for the biosafety dose of CuS-BSA NPs, 36 male Kunming mice were randomly assigned into six groups. Different one-time doses of CuS-BSA NPs were injected via tail vein injection, and the potential damages of liver, kidney and spleen were observed 14 days later. To evaluate the in vivo photothermal effect of CuS-BSA NPs, 48 male Kunming mice were used to establish the H22 hepatoma-bearing mouse model and were randomly assigned into six groups. CuS-BSA NPs (600 μg/kg) were injected via tail vein or intratumoral injection. Irradiations were performed 30 min after injection, with a 980 nm near-infrared laser (2.0 W/cm²) for 10 min once a week for 3 weeks. The results indicated that the CuS-BSA NPs had good dispersibility in three different solvents and had a strong absorption peak at 980 nm. The heating curves demonstrated that the photothermal effects of CuS-BSA NPs aqueous solution exhibited concentration dependence and power density dependence. In the in vivo experiment, when the doses of CuS-BSA NPs were in the range of 1800–7,200 μg/kg, the thymus index and spleen index of mice were not significantly different from those of the control group, and the structures of liver, kidney and spleen were intact without remarkable pathological changes. A lower dose of CuS-BSA NPs (600 μg/kg) could effectively inhibit tumor growth in H22 hepatoma-bearing mice at 980 nm NIR. Moreover, under the near-infrared laser irradiation, both in the tail vein injection group and the intratumoral injection group, a large area of necrosis in the tumor tissue, as well as the up-regulation of apoptotic proteins including cleaved caspase-3 and cleaved caspase-9 were observed. CuS-BSA NPs are promising photothermal agents in the photothermal therapy of cancer.

Microfluidized Dextran Microgels Loaded with Cisplatin/SPION Lipid Nanotherapeutics for Local Colon Cancer Treatment via Oral Administration

Multifunctional sequential targeted delivery system is developed as an efficient therapeutic strategy against malignant tumors with selective accumulation and minimal systemic drug absorption. The therapeutic system is comprised of microfluidized dextran microgels encapsulating cisplatin/superparamagnetic iron oxide nanoparticles (SPIONs)-loaded trilaurin-based lipid nanoparticles (LNPs). The microgel system is imparted hierarchically dual targeting via dextran and folic acid (FA) residues, leading to increases both in retention of the microgels in colon and in cellular uptake of the therapeutic LNPs by colon cancer cells while being used for oral therapeutic delivery. Encapsulation of the therapeutic LNPs into dextran microgels attained by microfluidized crosslinking reaction reduces gastrointestinal adhesion and prevents the FA-modified LNPs from cellular transport by proton-coupled FA transporters in small intestine during their oral delivery to colon. Upon enzymatic degradation of the dextran microgels by dextranase present exclusively in colon, LNPs thus released become more recognizable and readily internalized by FA receptor-overexpressing colon cancer cells. The combined chemo/magnetothermal therapeutic effect of dual targeted lipid nanoparticle-loaded microgels from entrapped lipidized cisplatin and alternating magnetic field-treated SPIONs significantly inhibits tumor growth and suppresses metastatic peritoneal carcinomatosis in orthotopic colon cancer-bearing mice.

In vivo photoacoustic image-guided tumor photothermal therapy and real-time temperature monitoring using a core-shell polypyrrole@CuS nanohybrid

Near-infrared (NIR) laser triggered theranostic platforms are increasingly used in clinical nanomedicine applications. In this work, a core-shell composite consisting of polypyrrole (PPy) coated copper sulfide (CuS) nanospheres with high photothermal efficiency and good photostability has been fabricated via a facile interfacial polymerization. The PPy@CuS nanohybrid had a hydrodynamic diameter of 58.5 nm with a CuS core and PPy shell and exhibited strong optical absorption and photon-to-heat conversion in the NIR region, leading to a sufficient photohyperthermic effect under irradiation with a 808 nm continuous wave laser. In vivo studies showed that the Ppy@CuS nanohybrids produced significant photoacoustic signals and exhibited remarkable photothermal therapeutic efficacy. Furthermore, the core-shell composites exhibited improved temperature elevation and photostability. The temperature-induced changes can be detected and monitored using photoacoustic imaging, thus allowing the control of the thermal dose while minimizing photothermal damage to surrounding healthy tissues. In summary, this study demonstrates that this novel platform could potentially be used for photoacoustic image-guided photothermal therapy and real-time temperature monitoring in cancer theranostics.

Mesoporous Polydopamine-Based Nanovehicles as a Versatile Drug Loading Platform to Enable Tumor-Sufficient Synergistic Therapy

The combination of photothermal therapy and chemotherapy are developing as a promising clinical strategy but it urgently needs the high exploration of intelligent multifunctional drug delivery nanovectors. In this paper, we used a versatile method to construct mesoporous polydopamine nanovehicles (MPDA) with the dendritic mesopores loaded with a clinical chemotherapeutic drug, Doxorubicin (MPDA@DOX). The monodisperse nanoagents are spherical with a size of ∼160 nm and pore size of approximately 10 nm. MPDA could efficiently delivery DOX with π-π stacking interaction and acts as the potent photothermal agents. Importantly, MPDA@DOX are preferentially internalized by cancerous cells, then bursting drug release and local hyperthermia generation were observed in conditions representative of the cytoplasm in tumor cells that highly synergistic cell killing effect were found under 808 nm laser irradiation. The fluorescent imaging results of human breast tumor bearing murine model evidenced that MPDA delivery platform have excellent tumor precise targeting effect and in vivo tumor ablation experiment further revealed that MPDA@DOX showed markedly eradicated tumor growth capability under laser exposure. Therefore, this work provided a fascinating strategy based on biocompatible MPDA based drug delivery system for malignant tumors eradication via synergistic therapy.

Two-Stage Targeted Bismuthene-Based Composite Nanosystem for Multimodal Imaging Guided Enhanced Hyperthermia and Inhibition of Tumor Recurrence

A key challenge for nanomedicines in clinical application is to reduce the dose while achieving excellent efficacy, which has attracted extensive attention in dose toxicity and potential risks. It is thus necessary to reasonably design nanomedicine with high-efficiency targeting and accumulation. Here, we designed and synthesized a tetragonal bismuthene-based "all-in-one" composite nanosystem (TPP-Bi@PDA@CP) with two-stage targeting, multimodal imaging, photothermal therapy, and immune enhancement functions. Through the elaborate design of its structure, the composite nanosystem possesses multiple properties including (i) two-stage targeting function of hepatoma cells and mitochondria [the aggregation at the tumor site is 2.63-fold higher than that of traditional enhanced permeability and retention (EPR) effect]; (ii) computed tomography (CT) contrast-enhancement efficiency as high as ∼51.8 HU mL mg^-1 (3.16-fold that of the clinically available iopromide); (iii) ultrahigh photothermal conversion efficiency (52.3%, 808 nm), promising photothermal therapy (PTT), and high-contrast infrared thermal (IRT)/photoacoustic (PA) imaging of tumor; (iv) benefitting from the two-stage targeting function and excellent photothermal conversion ability, the dose used in this strategy is one of the lowest doses in hyperthermia (the inhibition rate of tumor cells was 50% at a dose of 15 μg mL^-1 and 75% at a dose of 25 μg mL^-1); (v) the compound polysaccharide (CP) shell with hepatoma cell targeting and immune enhancement functions effectively inhibited the recurrence of tumor. Therefore, our work reduces the dose toxicity and potential risk of nanomedicines and highlights the great potential as an all-in-one theranostic nanoplatform for two-stage targeting, integrated diagnostic imaging, photothermal therapy, and inhibition of tumor recurrence.

Tumor-targeted/reduction-triggered composite multifunctional nanoparticles for breast cancer chemo-photothermal combinational therapy

Breast cancer has become the most commonly diagnosed cancer type in the world. A combination of chemotherapy and photothermal therapy (PTT) has emerged as a promising strategy for breast cancer therapy. However, the intricacy of precise delivery and the ability to initiate drug release in specific tumor sites remains a challenging puzzle. Therefore, to ensure that the therapeutic agents are synchronously delivered to the tumor site for their synergistic effect, a multifunctional nanoparticle system (PCRHNs) is developed, which is grafted onto the prussian blue nanoparticles (PB NPs) by reduction-responsive camptothecin (CPT) prodrug copolymer, and then modified with tumor-targeting peptide cyclo(Asp-d-Phe-Lys-Arg-Gly) (cRGD) and hyaluronic acid (HA). PCRHNs exhibited nano-sized structure with good monodispersity, high load efficiency of CPT, triggered CPT release in response to reduction environment, and excellent photothermal conversion under laser irradiation. Furthermore, PCRHNs can act as a photoacoustic imaging contrast agent-guided PTT. In vivo studies indicate that PCRHNs exhibited excellent biocompatibility, prolonged blood circulation, enhanced tumor accumulation, allow tumor-specific chemo-photothermal therapy to achieve synergistic antitumor effects with reduced systemic toxicity. Moreover, hyperthermia-induced upregulation of heat shock protein 70 in the tumor cells could be inhibited by CPT. Collectively, PCRHNs may be a promising therapeutic way for breast cancer therapy.

Emerging Roles of Green-Synthesized Chalcogen and Chalcogenide Nanoparticles in Cancer Theranostics

The last few decades have seen an overwhelming increase in the amount of research carried out on the use of inorganic nanoparticles. More fascinating is the tremendous progress made in the use of chalcogen and chalcogenide nanoparticles in cancer theranostics. These nanomaterials, which were initially synthesized through chemical methods, have now been efficiently produced using different plant materials. The paradigm shift towards the biogenic route of nanoparticle synthesis stems from its superior advantages of biosafety, eco-friendliness, and simplicity, among others. Despite a large number of reviews available on inorganic nanoparticle synthesis through green chemistry, there is currently a dearth of information on the green synthesis of chalcogens and chalcogenides for cancer research. Nanoformulations involving chalcogens such as sulfur, selenium, and tellurium and their respective chalcogenides have recently emerged as promising tools in cancer therapeutics and diagnosis. Similar to other inorganic nanoparticles, chalcogens and chalcogenides have been synthesized using plant extracts and their purified biomolecules. In this review, we provide an up-to-date discussion of the recent progress that has been made in the plant-mediated synthesis of chalcogens and chalcogenides with a special focus on their application in cancer theranostics.

Endogenous MicroRNA Accurate Diagnostics to Guide Photothermal Therapy

Developing an intelligent theranostic nanoplatform with satisfied diagnostic accuracy and therapeutic efficiency holds great promise for personalized nanomedicine. Herein, we constructed a smart nanodevice for the accurate diagnosis of endogenous cancer microRNA (miRNA) biomarkers and efficient photothermal therapy (PTT). The nanodevice was composed of polydopamine (PDA)-functionalized CuS nanosheets (CuS@PDA NSs) and three elaborate DNA hairpin probes (TDHPs). The CuS@PDA NSs acted as efficient delivery vehicles and photothermal agents. They provided a large surface area available for an efficient and facile loading of TDHPs and a high-fluorescence (FL) quenching performance to achieve an ultralow background signal. The intracellular miRNA triggered TDHPs to assemble into three-arm branched junction structures for a strong fluorescence recovery as output signals to discriminate cancer cells from normal cells with an excellent sensitivity. The CuS@PAD NSs showed a good photothermal conversion efficiency in the near-infrared II (NIR II) region to mediate a good photothermal performance to kill cancer cells. A remarkable antitumor therapeutic effect was achieved in vivo. This work integrated highly sensitive detection to endogenous cancer biomarkers and valid therapeutic potency to tumor-bearing mice, indicating its promising biomedical applications.

Recent Development of MOF-Based Photothermal Agent for Tumor Ablation

Metal-organic frameworks (MOFs) are 3D-architecture compounds of metal ions and organic molecules with sufficient and permanent porosity, showing great potential as a versatile platform to load various functional moieties to endow the hybrid materials with specific applications. Currently, a variety of photothermal nanometals have been embedded into organic ligands for integrating the unique photothermal effects with the merits of MOFs to improve their performances for cancer therapy. In this review, we have summarized a series of novel MOF-based photothermal materials for this unique therapeutic modality against tumors from three main aspects according to their chemical compositions and structures, i) metal-doped MOF, ii) organic-doped MOF, and iii) polymer-coated MOF. In addition, we have summarized the latest developments and characteristics of MOF-based photothermal agents, such as good biocompatibility, low toxicity, and responsive photothermal conversion without destroying the structure of hybrid photothermal agent. At last, we addressed the future perspectives of MOF-based photothermal agent in the field of phototherapy.

Photodynamic Therapeutic Effect of Nanostructured Metal Sulfide Photosensitizers on Cancer Treatment

Photodynamic therapy (PDT) utilizes photosensitizers (PSs) to produce reactive oxygen species (ROSs) upon irradiation, which causes the shutdown of vessels and deprives the tumor of nutrients and oxygen, and in turn induces adverse effects on the immune system. However, significant efforts are needed to increase the efficiency in PDT in terms of light delivery to specific PSs for the clinical treatment of tumors located deep under the skin. Even though PDT offers a disease site-specific treatment modality, current efforts are directed to improve the solubility (in body fluids and injectable solvents), photostability, amphiphilicity (for tissue penetration), elimination, and systemic toxicity of traditional PSs based on porphyrin derivatives. Nanostructured materials show promising features to achieve most of such combined efforts. They can be artificially engineered to carry multiple theranostic agents onto targeted tumor sites. However, recent studies on photosensitive Cd-based nanostructures, mostly used in PDT, indicate that leeching of Cd2+ ions is stimulated when they are exposed to harsh biological conditions for continuous periods of time, thus making them acutely toxic and hindering their applications in in vivo settings. Since nanostructured materials are not completely immune to degradation, great strides have been made to seek new alternatives. In this review, we focus on the latest advances of Cd-free nanostructured metal transition sulfides (MTSs) as alternative PSs and study their high-energy transfer efficiency, rational designs, and potential applications in cancer-targeted PDT. Nanostructured MTSs are discussed in the context of their versatility to serve as phototherapy agents and superior properties, including their strong absorption in the NIR region, excellent photothermal conversion efficiency, controlled reactive oxygen species (ROS) production, versatile surface chemistry, high fluorescence, and structural and thermal stability. We discuss the latest advancements in correlating the self-aggregation of MTSs with their passive tumor cell targeting, highlighting their ability to efficiently produce ROSs, and mitigating their dark toxicity through polymeric functionalization. Treatment of deep-seated tumors by using these PSs upon preferential uptake by tumor tissues (due to the enhanced permeability and retention effect) is also reviewed. We finally summarize the main future perspectives of MTSs as next-generation PSs within the context of cancer theranostics.

Ultra-small bimetallic phosphide for dual-modal MRI imaging guided photothermal ablation of tumor

Metal phosphides have been proved to be the potential theranostic agents of tumor. However, the limitation of single-modal imaging or treatment effect of such materials need to be further improved....

Acoustics at the nanoscale (nanoacoustics): A comprehensive literature review.: Part II: Nanoacoustics for biomedical imaging and therapy

In the past decade, acoustics at the nanoscale (i.e., nanoacoustics) has evolved rapidly with continuous and substantial expansion of capabilities and refinement of techniques. Motivated by research innovations in the last decade, for the first time, recent advancements of acoustics-associated nanomaterials/nanostructures and nanodevices for different applications are outlined in this comprehensive review, which is written in two parts. As part II of this two-part review, this paper concentrates on nanoacoustics in biomedical imaging and therapy applications, including molecular ultrasound imaging, photoacoustic imaging, ultrasound-mediated drug delivery and therapy, and photoacoustic drug delivery and therapy. Firstly, the recent developments of nanosized ultrasound and photoacoustic contrast agents as well as their various imaging applications are examined. Secondly, different types of nanomaterials/nanostructures as nanocarriers for ultrasound and photoacoustic therapies are discussed. Finally, a discussion of challenges and future research directions are provided for nanoacoustics in medical imaging and therapy.

Mesoporous Silica Nanoparticle-Based Imaging Agents for Hepatocellular Carcinoma Detection

Hepatocellular carcinoma (HCC) is characterized by poor prognosis and high mortality. The treatment of HCC is closely related to the stage, and the early-stage of HCC patients usually accompanies a more long-term survival rate after clinical treatment. Hence, there are critical needs to develop effective imaging agents with superior diagnostic precision for HCC detection at an early stage. Recently, mesoporous silica nanoparticles (MSNs) based imaging agents have gained extensive attentions in HCC detection, which can serve as a multifunctional nanoplatform with controllable size and facile surface functionalization. This perspective summarizes recent advances in MSNs based imaging agents for HCC detection by the incorporation of several clinical imaging modalities. Multi-modal imaging system has been developed for higher spatial resolution and sensitivity. Even though some limitations and challenges need to be overcome, we envision the development of novel MSNs based imaging agents will offer great potential applications in clinical HCC detection.

Multifunctional Hybrid Hydrogel Enhanced Antitumor Therapy through Multiple Destroying DNA Functions by a Triple-Combination Synergistic Therapy

Brachytherapy, as an effective setting for precise cancer therapy in clinic, can lead to serious DNA damage. However, its therapeutic efficacy is always limited by the DNA self-repair property, tumor hypoxia-associated radiation resistance as well as inhomogeneous distribution of the radioactive material. Herein, a multifunctional hybrid hydrogel (¹³¹ I-hydrogel/DOX/GNPs aggregates) is developed by loading gold nanoparticle aggregates (GNPs aggregates) and DOX into a radionuclide iodine-131 (¹³¹ I) labelled polymeric hydrogels (¹³¹ I-PEG-P(Tyr)₈ ) for tumor destruction by completely damaging DNA self-repair functions. This hybrid hydrogel exhibits excellent photothermal/radiolabel stability, biocompatibility, and fluorescence/photothermal /SPECT imaging properties. After local injection, the sustained releasing DOX within tumor greatly inhibits the DNA replication. Meanwhile, GNPs aggregates as a radiosensitizer and photosensitizer show a significant improvement of brachytherapeutic efficacy and cause serious DNA damage. Simultaneously, GNPs aggregates induce mild photothermal therapy under 808 nm laser irradiation, which not only inhibits self-repair of the damaged DNA but also effectively relieves tumor hypoxic condition to enhance the therapeutic effects of brachytherapy, leading to a triple-synergistic destruction of DNA functions. Therefore, this study provides a highly efficient tumor synergistic therapy platform and insight into the synergistic antitumor mechanism in DNA level.

Multimodal Contrast Agents for Optoacoustic Brain Imaging in Small Animals

Optoacoustic (photoacoustic) imaging has demonstrated versatile applications in biomedical research, visualizing the disease pathophysiology and monitoring the treatment effect in an animal model, as well as toward applications in the clinical setting. Given the complex disease mechanism, multimodal imaging provides important etiological insights with different molecular, structural, and functional readouts in vivo. Various multimodal optoacoustic molecular imaging approaches have been applied in preclinical brain imaging studies, including optoacoustic/fluorescence imaging, optoacoustic imaging/magnetic resonance imaging (MRI), optoacoustic imaging/MRI/Raman, optoacoustic imaging/positron emission tomography, and optoacoustic/computed tomography. There is a rapid development in molecular imaging contrast agents employing a multimodal imaging strategy for pathological targets involved in brain diseases. Many chemical dyes for optoacoustic imaging have fluorescence properties and have been applied in hybrid optoacoustic/fluorescence imaging. Nanoparticles are widely used as hybrid contrast agents for their capability to incorporate different imaging components, tunable spectrum, and photostability. In this review, we summarize contrast agents including chemical dyes and nanoparticles applied in multimodal optoacoustic brain imaging integrated with other modalities in small animals, and provide outlook for further research.

Fluorescent detection of microRNA-21 in MCF-7 cells based on multifunctional gold nanorods and the integration of chemotherapy and phototherapy

MicroRNA-21 is an important biomarker of tumor early prediction and metastasis, and its accurate detection is of great significance for tumor diagnosis and treatment. It will be a meaningful work to combine the detection of RNA with chemotherapy and photothermal therapy on the same composite material. Herein, we designed a multifunctional nanocomposite based on gold nanorods (AuNRs), making use of microRNA-triggered drug release and near-infrared photothermal effect, which has been developed for cancer therapy and microRNA-21detection. Firstly, the AuNRs with photothermal effect were synthesized as carriers for drug delivery. Then the surface of gold nanorods was modified by functional DNA chains to provide an efficient site for doxorubicin (DOX) loading. Finally, folic acid was introduced to achieve the targeted treatment of MCF-7 cells. The microRNA competed with the double-stranded DNA, resulting in the release of DOX and the recovery of fluorescence signal located at 595 nm with an excitation of 488 nm effectively. The nano-biosensor could not only achieve dual-function of diagnosis and treatment of cancer cells, but also accomplish the detection of microRNA in tumor cells. It showed a high selectivity for microRNA-21 determination with a limit of detection (LOD) of 2.1 nM from the linear relationship from 1.0 × 10^-5 M to 5.0 × 10^-7 M. This scheme provides an outstanding strategy for cell imaging, treatment, and detection, which serves as a promising candidate in the field of biomedical research.

Non-stoichiometric cobalt sulfide nanodots enhance photothermal and chemodynamic therapies against solid tumor

Photodynamic therapy (PDT) mainly relies on reactive oxygen species generated by light- activated photosensitizers and oxygen to kill tumor cells. However, a critical limitation of the current PDT is that it is less effective in solid tumors where the microenvironment is hypoxic, and, therefore, repeated treatment is required. Here, non-stoichiometric Co_2.19S₄ nanodots (NDs), which can be rapidly degraded to cobalt (Co²⁺) and sulfur (S^2-) ions, were developed to enhance tumor photothermal therapy (PTT) and chemodynamic therapy (CDT) via the capture of copper (Cu²⁺) ions (starvation therapy) in the hypoxic tumor microenvironment under near-infrared irradiation. Co_2.19S₄ NDs with excellent photothermal conversion efficiency (ɳ = 52%) can be used for PTT, and the Co²⁺ ions produced by their degradation can catalyze the endogenous hydrogen peroxide of tumor cells to produce highly toxic hydroxyl radicals to achieve tumor CDT. The mechanism of starvation therapy was explored using western blotting, and the results indicated that blocking the uptake of Cu²⁺ ions could restrain the growth and proliferation of tumors by inhibiting the BRAF/mitogen-activated extracellular signal regulated kinase (MEK)/extracellular regulated protein kinases (ERK) signaling pathway. Our work highlights the great potential of Co_2.19S₄ NDs as a theranostic agent for implementing photoacoustic/photothermal imaging and starvation therapy-enhanced PTT/CDT.

Fluorinated porphyrin-based theranostics for dual imaging and chemo-photodynamic therapy

Convenient strategies to transform regular liposomes or nano-micelles into multifunctional theranostics would be highly valuable in cancer therapy. Herein, we developed an amphiphilic fluorinated porphyrin dendrimer as a multifunctional "add-on" module which would self-assemble onto liposomal drug delivery systems and conveniently transform the liposomes into novel theranostics. Through cancer cells and murine xenograft tumor model assays, the theranostics showed valuable fluorescence/19F magnetic resonance dual modal imaging and highly efficient chemo-photodynamic therapy. The modular strategy facilitates the convenient and standardized preparation of multifunctional theranostics.

Recent Trends in Photoacoustic Imaging Techniques for 2D Nanomaterial-Based Phototherapy

A variety of 2D materials have been developed for therapeutic biomedical studies. Because of their excellent physicochemical properties, 2D materials can be used as carriers for delivering therapeutic agents into a lesion, leading to phototherapy. Various optical imaging techniques have been used for the monitoring of the treatment process. Among these, photoacoustic imaging has unique advantages including relatively deep imaging depth and large field of view with high spatial resolution. In this review article, we summarize the types of photoacoustic imaging systems used for phototherapy monitoring, then we explore contrast-enhanced photoacoustic images using 2D materials. Finally, photoacoustic image-guided phototherapies are discussed. We conclude that 2D material-based phototherapy can be efficiently monitored by photoacoustic imaging techniques.

Defective transition metal hydroxide-based nanoagents with hypoxia relief for photothermal-enhanced photodynamic therapy

Recently, phototherapy has attracted much attention due to its negligible invasiveness, insignificant toxicity and excellent applicability. The construction of a newly proposed nanosystem with synergistic photothermal and photodynamic tumor-eliminating properties requires a delicate structure design. In this work, a novel therapeutic nanoplatform (denoted as BCS-Ce6) based on defective cobalt hydroxide nanosheets was developed, which realized hypoxia-relieved photothermal-enhanced photodynamic therapy against cancer. Defective cobalt hydroxide exhibited high photothermal conversion efficacy at the near-infrared region (49.49% at 808 nm) as well as enhanced catalase-like activity to produce oxygen and greatly boost the singlet oxygen generation by a photosensitizer, Ce6, realizing efficacious dual-modal phototherapy. In vivo and in vitro experiments revealed that BCS-Ce6 can almost completely extinguish implanted tumors in a mouse model and present satisfactory biocompatibility during the treatment. This work sets a new angle of preparing photothermal agents and constructing comprehensive therapeutic nanosystems with the ability to modulate the hypoxic tumor microenvironment for efficient cancer therapy.

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

Plasmonic particles as gold nanorods have emerged as powerful contrast agents for critical applications as the photoacoustic imaging and photothermal ablation of cancer. However, their unique efficiency of photothermal conversion may turn into a practical disadvantage, and expose them to the risk of overheating and irreversible photodamage. Here, we outline the main ideas behind the technology of photoacoustic imaging and the use of relevant contrast agents, with a main focus on gold nanorods. We delve into the processes of premelting and reshaping of gold nanorods under illumination with optical pulses of a typical duration in the order of few ns, and we present different approaches to mitigate this issue. We undertake a retrospective classification of such approaches according to their underlying, often implicit, principles as: constraining the initial shape; or speeding up their thermal coupling to the environment by lowering their interfacial thermal resistance; or redistributing the input energy among more particles. We discuss advantages, disadvantages and contexts of practical interest where one solution may be more appropriate than the other.

Magnetic-responsive Pickering emulsion and its catalytic application at the water–oil interface

Schematic diagram of interfacial catalysis reactions by MRGO–Pd Pickering emulsion.

Tumor-targeting multi-shelled hollow nanospheres as drug loading platforms for imaging-guided combinational cancer therapy

In this work, we developed multi-shelled hollow nanospheres [RGD@am-ZnO@CuO@Au@DOX HNSs] as multifunctional therapeutic agents to achieve effective and targeted Zn2+/Cu2+ therapy, induced drug delivery under low pH/red-light conditions, and enhanced phototherapy under single red-light. The photothermal and photodynamic performance of am-ZnO@CuO@Au HNSs was enhanced relative to that of am-ZnO nanoparticles (NPs) or am-ZnO@CuO HNSs by utilizing the resonance energy transfer process and broad red-light absorption. The pH-sensitive am-ZnO@CuO@Au HNSs were dissolved to Zn2+/Cu2+ in the acidic endosomes/lysosomes of cancer cells, resulting in a cancer cell killing effect. The release performance of doxorubicin (DOX) from RGD@am-ZnO@CuO@Au@DOX HNSs was evaluated under low pH and red-light-irradiated conditions, and targeting of HNSs was confirmed by dual-modal imaging (magnetic resonance/fluorescence) of the tumor area. Moreover, in vivo synergistic therapy using RGD@am-ZnO@CuO@Au@DOX HNSs was further evaluated in mice bearing human pulmonary adenocarcinoma (A549) cells, achieving a remarkable synergistic antitumor effect superior to that obtained by monotherapy. This study validated that RGD@am-ZnO@CuO@Au@DOX HNSs can be a promising candidate for efficient postoperative cancer therapy.

A review on nanotoxicity and nanogenotoxicity of different shapes of nanomaterials

Nanomaterials (NMs) generally display fascinating physical and chemical properties that are not always present in bulk materials; therefore, any modification to their size, shape, or coating tends to cause significant changes in their chemical/physical and biological characteristics. The dramatic increase in efforts to use NMs renders the risk assessment of their toxicity highly crucial due to the possible health perils of this relatively uncharted territory. The different sizes and shapes of the nanoparticles are known to have an impact on organisms and an important place in clinical applications. The shape of nanoparticles, namely, whether they are rods, wires, or spheres, is a particularly critical parameter to affect cell uptake and site-specific drug delivery, representing a significant factor in determining the potency and magnitude of the effect. This review, therefore, intends to offer a picture of research into the toxicity of different shapes (nanorods, nanowires, and nanospheres) of NMs to in vitro and in vivo models, presenting an in-depth analysis of health risks associated with exposure to such nanostructures and benefits achieved by using certain model organisms in genotoxicity testing. Nanotoxicity experiments use various models and tests, such as cell cultures, cores, shells, and coating materials. This review article also attempts to raise awareness about practical applications of NMs in different shapes in biology, to evaluate their potential genotoxicity, and to suggest approaches to explain underlying mechanisms of their toxicity and genotoxicity depending on nanoparticle shape.

A Redox-Responsive, In-Situ Polymerized Polyplatinum(IV)-Coated Gold Nanorod as An Amplifier of Tumor Accumulation for Enhanced Thermo-Chemotherapy

It remains a major challenge to develop an effective therapeutic system based on gold nanorods (GNRs) for cancer therapy. Herein, we developed a redox-responsive, in-situ polymerized polyplatinum(IV)-coated gold nanorod (GNR@polyPt(IV)) with coupling of the near-infrared (NIR)-induced hyperthermal effect and redox-triggered drug release in one therapeutic platform as an amplifier of tumor accumulation through mild hyperthermia for enhanced synergistical thermo-chemotherapy. After in-situ polymerized with 2-methacryloyloxy ethyl phosphorylcholine (MPC) and Pt(IV) complex-based prodrug monomer (PPM) onto the surface of GNRs, the nanosized GNR@polyPt(IV) exhibited the advantages of high drug encapsulation efficiency, triggered drug release, and reduced side effect. As demonstrated by thermal imaging and photoacoustic imaging in vitro and in vivo, this GNR@polyPt(IV) exhibited an excellent NIR-associated hyperthermal effect and outstanding capacity of tumor accumulation. Importantly, under a mild hyperthermia process, the vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) were upregulation, resulting in angiogenic vessel around the tumor. Combination with accelerated blood flow and angiogenesis by mild hyperthermia, a dramatic increase of drug accumulation in tumor could be realized after systematic administration. As a result, this amplification fashion of tumor accumulation would contribute the GNR@polyPt(IV) to inhibit tumor progression effectively. Such a facile and simple methodology for enhanced therapeutic effect based on GNRs holds great promises for cancer therapy with further development.

Engineering Plasmonic Nanoparticles for Enhanced Photoacoustic Imaging

Photoacoustic (PA) imaging is an emerging imaging modality whereby pulsed laser illumination generates pressure transients that are detectable using conventional ultrasound. Plasmonic nanoparticles such as gold nanorods and nanostars are often used as PA contrast agents. The thermoelastic expansion model best describes the PA response from plasmonic nanoparticles: Light absorption causes a small increase in temperature leading to thermoelastic expansion. The conversion of optical energy into pressure waves (po) is dependent on several features: (i) the absorption coefficient (μa), (ii) the thermal expansion coefficient (β), (iii) specific heat capacity (Cp) of the absorbing material, (iv) speed of sound in the medium (c), and (v) the illumination fluence (F). Controlling the geometry, composition, coatings, and solvents around plasmonic nanostructures can help tune these variables to generate the optimum PA signal. The thermoelastic expansion model is not limited to plasmonic structures and holds true for all absorbing molecules. Here, we focus on ways to engineer these variables to enhance the PA response from plasmonic nanoparticles.

Light-Switchable Yolk-Mesoporous Shell UCNPs@MgSiO3 for Nitric Oxide-Evoked Multidrug Resistance Reversal in Cancer Therapy

Gas therapy has emerged as a forceful strategy for augmenting the effects of chemotherapeutic drugs against cancer cells. However, it remains extremely challenging to effectively deliver gas into tissues of interest and unravel its underlying mechanisms. Herein, we designed a near-infrared (NIR) light-switchable nitric oxide (NO) delivery nanosystem for high-efficacy multidrug resistance (MDR) reversal in cancer therapy based on a yolk-shell upconverting nanoparticles@magnesium silica (UCNP@MgSiO₃). The internal hollow cavity and flower-like mesoporous shell of UCNPs@MgSiO₃ not only enabled a significantly high encapsulation capacity for the NO precursor (BNN6) and doxorubicin (DOX) but also allowed the enhanced cellular uptake, resulting in NIR-triggered NO generation and low pH-triggered DOX release in cancer cells. Mechanistically, intracellular NO can downregulate the drug efflux-related P-glycoprotein and adenosine 5'-triphosphate-binding cassette transporters, thereby increasing the DOX accumulation in the cell nuclei. Such combination therapy of NO and DOX induced the apoptosis of MDR cells and completely inhibited in vivo MDR tumor growth. We further elucidated the therapy mechanism via proteomic profiling, showcasing the downregulation of the ubiquitin-proteasome pathway and nuclear factor kappa-B signaling pathway in the NO-treated MDR cells. Therefore, our findings develop a promising nanoscale gas/drug delivery paradigm for fighting MDR tumors and providing molecular insights into cancer therapy.

Vacancy-induced toxicity of CoSe2 nanomaterials in rat lung macrophages

Rich vacancies of semiconductor nanomaterials (NMs) give rise to great enhancement of their physical and chemical properties such as magnetic, catalytic, optical, etc. These NMs possessing extensive applications could inevitably enter into the environment and increase the toxic effects on organisms, so it is imperative to investigate the cytotoxicity of NMs with different types of vacancies. Here, one-dimensional cobalt selenide (CoSe₂) NMs with different vacancies were synthesized through the same precursor while calcined at different temperatures (P-CoSe₂ which calcined at 200 °C and N-CoSe₂ which calcined at 230 °C). According to the positron annihilation spectrum, the V_SeSe vacancy associate in P-CoSe₂ was endowed with two positive charges, while the V_CoCoCoSeSe vacancy associate in N-CoSe₂ possessed four negative charges. Cell viability assays revealed that N-CoSe₂ had higher toxicity to macrophages than P-CoSe₂, which was attributed to higher levels of intracellular reactive oxygen species induced by N-CoSe₂. Further investigation showed that N-CoSe₂ had higher affinity to the mitochondrion-targeting peptide, leading to its preferential distribution in the mitochondria and consequent induction of mitochondrial superoxide production. In contrast, P-CoSe₂ exhibited higher affinity to the endoplasmic reticulum (ER)-targeting peptide, facilitating its preferential distribution in the ER and the nuclei and causing higher damage to both organelles as compared to N-CoSe₂. These results demonstrated that type of surface vacancies significantly affected biodistribution of NMs in subcellular organelles, which contributed to differential biological behaviors of the NMs.

Oxygen self-enriched nanoplatform combined with US imaging and chemo/photothermal therapy for breast cancer

Oxygen-saturated perfluorohexane-cored, cisplatin (Pt)-decorated hollow gold nanospheres (Pt-HAuNS-PFH@O₂) have been synthesized for ultrasound (US) imaging-guided tumor treatment depending on chemo/photothermal therapy, relief of hypoxia, and photothermal induced US contrast signal. Both NIR laser-induced hyperthermia generation by gold nanospheres and acidity triggered release of Pt resulted in high toxicity after internalization by breast cancer cells. According to ex vivo immunofluorescence investigation and in vivo pharmacodynamic studies on MDA-MB-231 tumor bearing mice, the susceptibility of tumors to Pt-HAuNS-PFH@O₂ was improved by the relief of hypoxia. In addition, US imaging under different conditions verified the amplified US contrast property of Pt-HAuNS-PFH@O₂ by the heat-dependent liquid-gas conversion of PFH. Overall, Pt-HAuNS-PFH@O₂ can be promisingly used as an oxygen self-enriched nanoplatform for US imaging-guided chemo/photothermal therapy.

Applications of inorganic nanoparticles in the diagnosis and therapy of atherosclerosis

Atherosclerosis is a chronic progressive disease, which may result in serious clinical outcomes, such as acute heart events or stroke with high mortality. At present, the clinical problems of atherosclerosis mainly consist of the difficulty in confirming the plaques or identifying the stability of the plaques in the early phase and the shortage of valid treatments. Fortunately, with the development of nanotechnology, various inorganic nanoparticles with imaging enhancement and noninvasive therapy functions have been studied in the imaging and treatment of atherosclerosis, which has brought new hope to patients. This review focuses on the recent progress in the use of inorganic nanoparticles in the diagnosis and therapy of atherosclerosis, including the key processes in the development of atherosclerosis and the mainly involved cells, inorganic nanoparticle-based dual-mode imaging methods classified by the types of targeting cells, and inorganic nanoparticle-based therapeutic approaches, such as photothermal therapy (PTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), drug delivery, gene therapy and imaging-guided therapy for atherosclerosis. Finally, this review discusses the challenges and directions of inorganic nanoparticles in potential clinical translation of anti-atherosclerosis in future. We believe this review will enable readers to systematically understand the progress of the inorganic nanoparticle-based imaging and therapy of atherosclerosis and therefore promote the further development of anti-atherosclerosis.