Near-infrared light-triggered, targeted drug delivery to cancer cells by aptamer gated nanovehicles

Mitochondrial Targeted Thermosensitive Nanocarrier for Near-Infrared-Triggered Precise Synergetic Photothermal Nitric Oxide Chemotherapy

Nitric oxide (NO) intervenes, that is, a potential treatment strategy, and has attracted wide attention in the field of tumor therapy. However, the therapeutic effect of NO is still poor, due to its short half-life and instability. Therapeutic concentration ranges of NO should be delivered to the target tissue sites, cell, and even subcellular organelles and to control NO generation. Mitochondria have been considered a major target in cancer therapy for their essential roles in cancer cell metabolism and apoptosis. In this study, mesoporous silicon-coated gold nanorods encapsulated with a mitochondria targeted and the thermosensitive lipid layer (AuNR@MSN-lipid-DOX) served as the carrier to load NO prodrug (BNN6) to build the near-infrared-triggered synergetic photothermal NO-chemotherapy platform (AuNR@MSN(BNN6)-lipid-DOX). The core of AuNR@MSN exhibited excellent photothermal conversion capability and high loading efficiency in terms of BNN6, reaching a high value of 220 mg/g (w/w), which achieved near-infrared-triggered precise release of NO. The outer biocompatible lipid layer, comprising thermosensitive phospholipid DPPC and mitochondrial-targeted DSPE-PEG2000-DOX, guided the whole nanoparticle to the mitochondria of 4T1 cells observed through confocal microscopy. In the mitochondria, the nanoparticles increased the local temperature over 42 °C under NIR irradiation, and a high NO concentration from BNN6 detected by the NO probe and DSPE-PEG2000-DOX significantly inhibited 4T1 cancer cells in vitro and in vivo under the synergetic photothermal therapy (PTT)-NO therapy-chemotherapy modes. The built NIR-triggered combination therapy nanoplatform can serve as a strategy for multimodal collaboration.

Active Targeted Janus Theranostic Nanoplatforms Enable Chemo-Photothermal Therapy to Inhibit the Growth of Breast Cancer

Nanoscale structures have been developed to serve various functions in cancer therapy, encompassing areas such as diagnosis, biomedical visualization, tissue regeneration, and drug delivery. Based on biocompatible chitosan oligosaccharides (COS) and gold nanorods (GNRs), we designed the drug delivery systems (GNR@polyacrylic acid-Mn@COS Janus nanoparticles (JNPs)), which achieved paclitaxel (PTX) loaded on the side of GNRs, and the PAA-Mn domain served as magnetic resonance imaging contrast agents. This system was found to be effectively delivered to tumor sites through the enhanced permeability and retention (EPR) effect and the active target of the COS. The uniform JNPs selectively targeted cancer cells instead of normal cells through interacting with the COS on the surface of tumor cells, and the pH/NIR-responsive drug release behavior further enhanced their therapeutic effects. The in vivo effects of JNPs against tumors were evaluated using subcutaneous and orthotopic lung metastasis models, yielding promising outcomes for both tumor diagnosis and cancer treatment. In conclusion, the obtained JNPs hold great promise as a theranostic nanoplatform with synergistic chemotherapeutic and photothermal effects.

Effective Distribution of Gold Nanorods in Ordered Thick Mesoporous Silica: A Choice of Noninvasive Theranostics

Porous silica coated gold nanorod core-shell structures demonstrate a multifunctional role in bioimaging, drug delivery, and cancer therapeutics applications. Here, we address a new approach for effective distribution of gold nanorods (GNRs) in a mesoporous silica (MS) shell, viz., one nanorod in one silica particle (GMS). We have studied that silica coating presents major advantages for the better biocompatibility and stability of GNRs. In this study, two different thicknesses of silica shell over GNRs have been discussed as per the application's need; GNRs in thin silica (11 nm) are fit for phototherapy and bioimaging, whereas thick and porous silica (51 nm) coated gold nanorods are suitable for triggered drug delivery and theranostics. However, effective distribution of GNRs in ordered architecture of thick mesoporous silica (MS, more than 50 nm thickness) with high surface area (more than 1000 m2/g) is not well understood so far. Here, we present methodical investigations for uniform and highly ordered mesoporous silica coating over GNRs with tunable thickness (6 to 51 nm). Judicious identification and optimization of different reaction parameters like concentrations of silica precursor (TEOS, 1.85-43.9 mM), template (CTAB, 0.9-5.7 mM), effect of temperature, pH (8.6-10.8), stirring speed (100-400 rpm), and, most importantly, the mode of addition of TEOS with GNRs have been discussed. Studies with thick, porous silica coated GNRs simplify the highest ever reported surface area (1100 m2/g) and cargo capacity (57%) with better product yield (g/batch). First and foremost, we report a highly scalable (more than 500 mL) and rapid direct deposition of an ordered MS shell around GNRs. These engineered core-shell nanoparticles demonstrate X-ray contrast property, synergistic photothermal-chemotherapeutics, and imaging of tumor cell (96% cell death) due to released fluorescent anticancer drug molecules and photothermal effect (52 °C) of embedded GNRs. A deeper insight into their influence on the architectural features and superior theranostics performances has been illustrated in detail. Hence, these findings indicate the potential impact of individual GMS for image guided combination therapeutics of cancer.

Endogenous NO-release multi-responsive hollow mesoporous silica nanoparticles for drug encapsulation and delivery

Novel multi-responsive drug delivery vehicles (CDs/PNVCL@HMSNs) were prepared by grafting amino-terminated poly (N-vinyl caprolactam) (PNVCL-NH₂) and amino-rich carbon dots (CDs) on the surface of aldehyde-functionalized HMSNs (HMSNs-CHO) via Schiff base reaction. The CDs were prepared from L-arginine and their surfaces were rich in guanidine. Doxorubicin (DOX) was loaded into the nanoparticles to form drug loaded vehicles (CDs/PNVCL@HMSNs-DOX) and the drug loading efficiency was 58.38%. The drug release behaviors of CDs/PNVCL@HMSNs-DOX showed temperature and pH responsiveness due to the poly (N-vinyl caprolactam) (PNVCL) and Schiff base bond. The high concentration of NO released in high concentration H₂O₂ of tumor site could induce tumor cells apoptosis. The multi-responsive CDs/PNVCL@HMSNs are intriguing drug carriers, which combine drug delivery and NO release in one.

Advanced cancer targeting using aptamer functionalized nanocarriers for site-specific cargo delivery

The non-specificity of standard anticancer therapies has profound detrimental consequences in clinical treatment. Therapeutic specificity can be precisely achieved using cutting-edge ligands. Small synthetic oligonucleotide-ligands chosen through Systematic evolution of ligands by exponential enrichment (SELEX) would be an unceasing innovation in using nucleic acids as aptamers, frequently referred to as "chemical antibodies." Aptamers act as externally controlled switching materials that can attach to various substrates, for example, membrane proteins or nucleic acid structures. Aptamers pose excellent specificity and affinity for target molecules and can be used as medicines to suppress tumor cell growth directly. The creation of aptamer-conjugated nanoconstructs has recently opened up innovative options in cancer therapy that are more effective and target tumor cells with minor toxicity to healthy tissues. This review focuses on a comprehensive description of the most capable classes of aptamer-tethered nanocarriers for precise recognition of cancer cells with significant development in proficiency, selectivity, and targetability for cancer therapy. Existing theranostic applications with the problems and future directions are also highlighted.

Stimulus-responsive strategy based on MnO2 nanosheet-modified mesoporous silica nanoprobes for accurate multiple mRNAs detection

Fluorescence detection of multiple mRNAs has attracted great attention for disease diagnosis. In this work, a stimulus-responsive strategy for highly sensitive and accurate multiple mRNAs detection was proposed. This stimulus-responsive detection system was prepared by mesoporous silica nanoparticles (MSN), manganese dioxide (MnO₂) nanosheets, and DNA probes. DNA probes were loaded into the pores of MSN, which were closed with MnO₂ nanosheets. In the presence of glutathione (GSH) and target mRNAs, MnO₂ nanosheets were degraded by GSH, resulting in the release of DNA probes. These DNA probes hybridized to the corresponding target mRNA, thereby changing the fluorescence intensity of fluorophores of DNA probes, which could achieve the quantification of target mRNA. This system could simultaneously detect survivin mRNA and Thymidine kinase 1 mRNA at low background levels with relative limits of detection of 0.9 nM and 0.7 nM, respectively. Moreover, this assay has been successfully applied to detect multiple mRNAs with adequate anti-interference ability in the biological sample.

Mesoporous Silica Nanoparticles as a Potential Nanoplatform: Therapeutic Applications and Considerations

With advances in nanotechnology, nanoparticles have come to be regarded as carriers of therapeutic agents and have been widely studied to overcome various diseases in the biomedical field. Among these particles, mesoporous silica nanoparticles (MSNs) have been investigated as potential nanocarriers to deliver drug molecules to various target sites in the body. This review introduces the physicochemical properties of MSNs and synthesis procedures of MSN-based nanoplatforms. Moreover, we focus on updating biomedical applications of MSNs as a carrier of therapeutic or diagnostic cargo and review clinical trials using silica-nanoparticle-based systems. Herein, on the one hand, we pay attention to the pharmaceutical advantages of MSNs, including nanometer particle size, high surface area, and porous structures, thus enabling efficient delivery of high drug-loading content. On the other hand, we look through biosafety and toxicity issues associated with MSN-based platforms. Based on many reports so far, MSNs have been widely applied to construct tissue engineering platforms as well as treat various diseases, including cancer, by surface functionalization or incorporation of stimuli-responsive components. However, even with the advantageous aspects that MSNs possess, there are still considerations, such as optimizing physicochemical properties or dosage regimens, regarding use of MSNs in clinics. Progress in synthesis procedures and scale-up production as well as a thorough investigation into the biosafety of MSNs would enable design of innovative and safe MSN-based platforms in biomedical fields.

Navigating zinc-involved nanomedicine in oncotherapy

Zinc (Zn), extolled as "the flower of life" in modern medicine, has been extensively highlighted with its physiological functions to maintain growth, development, and metabolism homeostasis. Driven by the substantial advancement of nanotechnology and oncology, Zn-involved nanomedicines integrating the intrinsic bioactivity of Zn species and the physiochemical attributes of Zn-composed nanosystems have blazed a highly efficient and relatively biosafe antineoplastic path. In this review, we aim to highlight and discuss the recent representative modalities of emerging Zn-involved oncology nanomedicine, mainly emphasizing the rational design, biological effect and biosafety, and therapeutic strategies. In addition, we provide the underlying critical obstacles and future perspectives of Zn-involved oncology nanomedicines, primarily focusing on the chances and challenges of clinical translation. Furthermore, we hope the review can give rise to opportunities within oncology nanomedicine and other biomedical fields, promoting the prosperity and progress of the "Zincic Age".

Carbohydrate ligands-directed active tumor targeting of combinatorial chemotherapy/phototherapy-based nanomedicine: A review

Phototherapies or light mediated therapies, including mutually photothermal and photodynamic therapy that encompass irradiation of the target organs with light, have been widely employed as minimally invasive approach associated with negligible drug resistance for eradicating multiple tumors with minimal hazards to normal organs. Despite all these advantages, many obstacles in phototherapy hinder progress toward clinical application. Therefore, researchers have developed nano-particulate delivery systems integrated with phototherapy and therapeutic cytotoxic drugs to overcome these obstacles and achieve maximum efficacy in cancer treatment. Active targeting ligands were integrated into their surfaces to improve the selectivity and tumor targeting ability, enabling easy binding and recognition by cellular receptors overexpressed on the tumor tissue compared to normal ones. This enhances intratumoral accumulation with minimal toxicity on the adjacent normal cells. Various active targeting ligands, including antibodies, aptamers, peptides, lactoferrin, folic acid and carbohydrates, have been explored for the targeted delivery of chemotherapy/phototherapy-based nanomedicine. Among these ligands, carbohydrates have been applied due to their unique features that ameliorate the bioadhesive, noncovalent conjugation to biological tissues. In this review, the up-to-date techniques of employing carbohydrates active targeting ligands will be highlighted concerning the surface modification of the nanoparticles for ameliorating the targeting ability of the chemo/phototherapy.

DNA-Tetrahedra Corona-Modified Hydrogel Microcapsules: "Smart" ATP- or microRNA-Responsive Drug Carriers

The assembly of adenosine triphosphate (ATP)-responsive and miRNA-responsive DNA tetrahedra-functionalized carboxymethyl cellulose hydrogel microcapsules is presented. The microcapsules are loaded with the doxorubicin-dextran drug or with CdSe/ZnS quantum dots as a drug model. Selective unlocking of the respective microcapsules and the release of the loads in the presence of ATP or miRNA-141 are demonstrated. Functionalization of the hydrogel microcapsules a with corona of DNA tetrahedra nanostructures yields microcarriers that revealed superior permeation into cells. This is demonstrated by the effective permeation of the DNA tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to epithelial MCF-10A nonmalignant breast cells. The superior permeation of the tetrahedra-functionalized microcapsules into MDA-MB-231 breast cancer cells, as compared to analog control hydrogel microcapsules modified with a corona of nucleic acid duplexes. The effective permeation of the stimuli-responsive, drug-loaded, DNA tetrahedra-modified microcapsules yields drug carriers of superior and selective cytotoxicity toward cancer cells.

Dynamic Catalysis Guided by Nucleic Acid Networks and DNA Nanostructures

Nucleic acid networks conjugated to native enzymes and supramolecular DNA nanostructures modified with enzymes or DNAzymes act as functional reaction modules for guiding dynamic catalytic transformations. These systems are exemplified with the assembly of constitutional dynamic networks (CDNs) composed of nucleic acid-functionalized enzymes, as constituents, undergoing triggered structural reconfiguration, leading to dynamically switched biocatalytic cascades. By coupling two nucleic acid/enzyme networks, the intercommunicated feedback-driven dynamic biocatalytic operation of the system is demonstrated. In addition, the tailoring of a nucleic acid/enzyme reaction network driving a dissipative, transient, biocatalytic cascade is introduced as a model system for out-of-equilibrium dynamically modulated biocatalytic transformation in nature. Also, supramolecular nucleic acid machines or DNA nanostructures, modified with DNAzyme or enzyme constituents, act as functional reaction modules driving temporal dynamic catalysis. The design of dynamic supramolecular machines is exemplified with the introduction of an interlocked two-ring catenane device that is dynamically reversibly switched between two states operating two different DNAzymes, and with the tailoring of a DNA-tweezers device functionalized with enzyme/DNAzyme constituents that guides the dynamic ON/OFF operation of a biocatalytic cascade by opening and closing the molecular device. In addition, DNA origami nanostructures provide functional scaffolds for the programmed positioning of enzymes or DNAzyme for the switchable operation of catalytic transformations. This is introduced by the tailored functionalization of the edges of origami tiles with nucleic acids guiding the switchable formation of DNAzyme catalysts through the dimerization/separation of the tiles. In addition, the programmed deposition of two-enzyme/cofactor constituents on the origami raft allowed the dynamic photochemical activation of the cofactor-mediated biocatalytic cascade on the spatially biocatalytic assembly on the scaffold. Furthermore, photoinduced "mechanical" switchable and reversible unlocking and closing of nanoholes in the origami frameworks allow the "ON" and "OFF" operation of DNAzyme units in the nanoholes, confined environments. The future challenges and potential applications of dynamic nucleic acid/enzyme and DNAzyme conjugates are discussed in the conclusion paragraph.

Nanomaterial-Based Drug Delivery System Targeting Lymph Nodes

The lymphatic system plays an indispensable role in humoral balance, lipid metabolism, and immune regulation. The lymph nodes (LNs) are known as the primary sites of tumor metastasis and the metastatic LNs largely affected the prognosis of the patiens. A well-designed lymphatic-targeted system favors disease treatment as well as vaccination efficacy. In recent years, development of nanotechnologies and emerging biomaterials have gained increasing attention in developing lymph-node-targeted drug-delivery systems. By mimicking the endogenous macromolecules or lipid conjugates, lymph-node-targeted nanocarries hold potential for disease diagnosis and tumor therapy. This review gives an introduction to the physiological functions of LNs and the roles of LNs in diseases, followed by a review of typical lymph-node-targeted nanomaterial-based drug-delivery systems (e.g., liposomes, micelles, inorganic nanomaterials, hydrogel, and nanocapsules). Future perspectives and conclusions concerned with lymph-node-targeted drug-delivery systems are also provided.

Glutathione-Sensitive Mesoporous Organosilica-Coated Gold Nanorods as Drug Delivery System for Photothermal Therapy-Enhanced Precise Chemotherapy

The combination of photothermal therapy (PTT) and chemotherapy can remarkably improve the permeability of the cell membrane and reduce the concentration of chemotherapy agents that not only kill the tumor cells effectively but also have adverse effects on normal tissues. It is of great meaning to construct nanomaterials that could be simultaneously applied for tumor eradication with PTT and chemotherapy. In this work, we developed a novel gold nanorod coated with mesoporous organosilica nanoparticles (oMSN-GNR), which presented as an optimal photothermal contrast agent. Moreover, after doxorubicin loading (oMSN-GNR–DOX), the organosilica shell exhibited biodegradable properties under high glutathione in the tumor microenvironment, resulting in massively releasing doxorubicin to kill tumor cells. More importantly, the hyperthermia effect of GNR cores under near-infrared light provided promising opportunities for localized photothermal ablation in vivo. Therefore, the combination of precise chemotherapy and highly effective PTT successfully inhibited tumor growth in liver tumor-bearing mice. This versatile synergistic therapy with local heating and chemotherapeutics precise release opens up the potential clinical application of PTT and chemotherapy therapeutics for malignant tumor eradication.

Tailored Nucleic Acid Architectures at Gold Surfaces for Controlled Therapeutic Release

Nucleic acids are versatile materials capable of forming smart nanocarriers with highly controllable therapeutic delivery. DNA-gated release is a mechanism by which DNA oligonucleotides physically block the release of encapsulated drugs from porous nanoparticles. We extend this mechanism to be used with drugs bound to the surface of DNA-capped gold nanoparticles (AuNPs). We investigated DNA monolayers of different thicknesses and hybridization states to determine how DNA surface architecture can affect the release of a template drug bound to the gold surface. DNA layers are investigated on the planar gold surface via quartz crystal microbalance with dissipation and on AuNPs via dynamic light scattering. The resultant layer architectures were studied for their effect on the release rate of drugs. We observed that varying DNA architectures on AuNPs result in different release rates of the drug. The rate of drug release can be slowed using either folded or randomly coiled DNA sequences, which act as a physical barrier to diffusion. DNA monolayers with upright orientation release drugs more quickly. When the longer single-stranded DNA is used, the drug release is slowed even further. However, even upright DNA layers provide a barrier to drug diffusion at longer sequence lengths. We hypothesize that it is the architecture of the DNA layer, influenced by the folded or upright orientation of individual DNA molecules, that affects the free diffusion of the drug away from the AuNP surface. This mechanism may improve the biological availability of many surface-bound drugs on solid, DNA-capped nanoparticles.

Breast Cancer Bone Metastasis: A Narrative Review of Emerging Targeted Drug Delivery Systems

Bone is one of the most common metastatic sites among breast cancer (BC) patients. Once bone metastasis is developed, patients' survival and quality of life will be significantly declined. At present, there are limited therapeutic options for BC patients with bone metastasis. Different nanotechnology-based delivery systems have been developed aiming to specifically deliver the therapeutic agents to the bone. The conjugation of targeting agents to nanoparticles can enhance the selective delivery of various payloads to the metastatic bone lesion. The current review highlights promising and emerging advanced nanotechnologies designed for targeted delivery of anticancer therapeutics, contrast agents, photodynamic and photothermal materials to the bone to achieve the goal of treatment, diagnosis, and prevention of BC bone metastasis. A better understanding of various properties of these new therapeutic approaches may open up new landscapes in medicine towards improving the quality of life and overall survival of BC patients who experience bone metastasis.

Active targeted Janus nanoparticles enable anti-angiogenic drug combining chemotherapy agent to prevent postoperative hepatocellular carcinoma recurrence

Surgery is one of the main effective strategies for the treatment of solid tumors, but high postoperative recurrence is also the main cause of death in current cancer therapy. The prevention of postoperative hepatocellular carcinoma (HCC) recurrence is a clinical problem that needs to be solved urgently. At present, there are still some problems to be solved, such as, how to achieve free drugs to target the site of surgical resection; develop a strategy for the simultaneous administration of multiple drugs to inhibit postoperative recurrence; and provide the appropriate animal model that mimics the process of postoperative HCC recurrence. In this study, we used a facile and reproducible method to successfully prepare amphiphilic Janus nanoparticles (JNPs). In order to improve targeting of the JNPs to residual HCC cells after surgery, we modified the side of gold nanorods (GNRs) with lactobionic acid (LA), thus creating LA-JNPs. This provided an active and targeted co-delivery system for hydrophilic and hydrophobic drugs in separate rooms, thus avoiding mutual effects. Next, we established two models to simulate postoperative HCC recurrence: a subcutaneous postoperative recurrence model based on patient-derived tumor xenograft (PDX) tissues and a postoperative recurrence model of orthotopic HCC. By applying these models, the enhanced permeability and retention effect (EPR) based tumor targeting and LA based active targeting can jointly promote the enrichment and uptake of JNPs at tumor site. LA-JNPs represented an efficient targeting system for the co-delivery of Sorafenib/Doxorubicin with an optimized anti-recurrence effect and significantly improved the survival of mice during treatment for postoperative recurrence.

In situ formation of a near-infrared controlled dual-antibacterial platform

An in situ formed antibacterial platform was designed for near-infrared controlled pharmacotherapy and photothermal therapy of drug-resistant bacteria.

Stimuli-responsive nanomaterials for cancer treatment: boundaries, opportunities and applications

Small molecule drugs, including most chemotherapies, are rapidly degraded and/or eliminated from the body, which is why high doses of these drugs are necessary, potentially producing toxic effects. Several types of nanoparticles loaded with anti-cancer drugs have been designed to overcome the disadvantages of conventional therapies. Modified nanoparticles can circulate for a long time, thus improving the solubility and biodistribution of drugs. Furthermore, they also allow the controlled release of the payload once its target tissue has been reached. These mechanisms can reduce the exposure of healthy tissues to chemotherapeutics, since the drugs are only released in the presence of specific tumour stimuli. Overall, these properties can improve the effectiveness of treatments while reducing undesirable side effects. In this article, we review the recent advances in stimuli-responsive albumin, gold and magnetic nanostructures for controlled anti-cancer drug delivery. These nanostructures were designed to release drugs in response to different internal and external stimuli of the cellular environment, including pH, redox, light and magnetic fields. We also describe various examples of applications of these nanomaterials. Overall, we shed light on the properties, potential clinical translation and limitations of stimuli-responsive nanoparticles for cancer treatment.

Regulation of oligonucleotide adsorption by a thermo and pH dual-responsive copolymer layer

Oligonucleotides hold great promise as therapeutic agents to specifically and selectively inhibit gene expression. In order to achieve better targeting efficiency and treatment efficacy, nanocarriers that are dual-responsive to both temperature and pH are more attractive and suitable due to the fact that certain malignancies can cause a slight increase of local temperature and a minor decrease in extracellular pH around the tumor site at the same time. Here, we systematically study oligonucleotide adsorption on the poly(ethyleneimine)-b-poly(N-isopropylacrylamide) (PEI-b-PNIPAm) copolymer layer grafted on a planar surface and nanoparticles with various radii, where the single effect of temperature or pH alone on oligonucleotide adsorption has been extensively investigated, but the combined effect of temperature and pH is less discussed. The theoretical results show that the surface density of the adsorbed oligonucleotides exhibits thermo and pH dual-responsive behavior, in which temperature and pH exhibit a combined effect on the loading capacity of the oligonucleotides. The underlying molecular mechanism of the dual-responsive behavior is revealed. Besides, the effect of important but coupled parameters in nanocarrier design such as polymer surface coverage and length, salt concentration as well as surface curvature (inverse nanoparticle radius) that may influence the dual-responsive behavior of oligonucleotide adsorption is further discussed, which is of great significance to direct the optimal design of PNIPAm/PEI-based nanocarriers to improve the transfection efficiency by achieving the maximal loading capacity of oligonucleotides at different temperatures and pH values.

The facile formation of hierarchical mesoporous silica nanocarriers for tumor-selective multimodal theranostics

The combination of therapeutic and diagnostic functions in a single platform has aroused great interest due to the more optimal synergistic effects that can be obtained as compared to any single theranostic approach alone. However, current nanotheranostics are normally formed via complicated construction steps involving the pre-synthesis of each component and further conjugation via chemical bonds, which may cause low integration efficiency and limit production and applications. Herein, a tumor-targeting and tumor-responsive all-in-one nanoplatform based on mesoporous silica nanocarriers (MSNs) was fabricated via a facile approach utilizing efficient and nondestructive physical interactions for long-wavelength fluorescence imaging-guided synergistic chemo-catalytic-photothermal tumor therapy. The MSNs were endowed with these multimodal theranostics via a simple hydrothermal method after coordinating with Fe2+ and glutathione (GSH) to introduce ferroferric oxide and carbon dots in situ. The former acts as a photothermal agent and catalytic agent to generate local heat under 808 nm irradiation and also when toxic hydroxyl radicals (˙OH) are in contact with abundant hydrogen peroxide in cancer cells, while the latter participates in fluorescence imaging. After loading with paclitaxel (PTX), polyester and folic-acid-conjugated cyclodextrin were employed to serve as an esterase-sensitive gatekeeper controlling PTX release from the MSN pores and as a tumor-targeting agent for accurate therapy, respectively. As expected, the nanoplatform was efficiently taken up by tumor cells over healthy cells, and then, synergetic chemo-catalytic-photothermal therapy was performed, resulting in 5-fold greater apoptosis of tumor cells as compared to healthy cells under 808 nm irradiation. Moreover, in vivo data from tumor-bearing mouse models showed that tumors were significantly inhibited, and the survival rates of these mice increased to greater than 80% after 5 weeks of treatment with our nanoplatform. These therapeutic processes could be directly tracked via fluorescence imaging enabled by carbon dots and, therefore, our nanoplatform provides a promising theranostics approach for tumor treatment.

The Multifunctionally Graded System for a Controlled Size Effect on Iron Oxide-Gold Based Core-Shell Nanoparticles

We report that Fe3O4@Au core-shell nanoparticles (NPs) serve as a multifunctional molecule delivery platform. This platform is also suitable for sensing the doxorubicin (DOX) through DNA hybridization, and the amount of carried DOX molecules was determined by size-dependent Fe3O4@Au NPs. The limits of detection (LODs) for DOX was found to be 1.839 nM. In our approach, an Au nano-shell coating was coupled with a specially designed DNA sequence using thiol bonding. By means of a high-frequency magnetic field (HFMF), a high release percentage of such a molecule could be efficiently achieved in a relatively short period of time. Furthermore, the thickness increase of the Au nano-shell affords Fe3O4@Au NPs with a larger surface area and a smaller temperature increment due to shielding effects from magnetic field. The change of magnetic property may enable the developed Fe3O4@Au-dsDNA/DOX NPs to be used as future nanocarrier material. More importantly, the core-shell NP structures were demonstrated to act as a controllable and efficient factor for molecule delivery.

Biomacromolecule-based photo-thermal agents for tumor treatment

Cancer treatment has become one of the biggest challenges in modern medicine. Recently, many efforts have been devoted to treat tumors by surgical resection, radiotherapy, or chemotherapy. In comparison to these methods, photo-thermal therapy (PTT) with noninvasive, controllable, direct, and precise characteristics has received tremendous attention in eliminating tumor cells over the past decades. In particular, PTT based on biomacromolecule-based photo-thermal agents (PTAs) outperforms other systems with high photo-thermal efficiency, simple coating, and low immunogenicity. Considering the unique advantages of biomacromolecule-based PTAs in tumor treatment, it is necessary to summarize the recent progress in the field of biomacromolecule-based PTAs for tumor treatment. Herein, this minireview outlines recent progress in the fabrication and applications of biomacromolecule-based PTAs. Within this framework, various types of biomacromolecule-based PTAs are highlighted, including cell-based agents, protein-based agents, nucleotide-based agents, and polysaccharide-based PTAs. In each section, the functional design, photo-thermal effects, and potential clinical applications of each type of PTA are discussed. Finally, a brief perspective for the development of biomacromolecule-based PTAs is presented.

Recent Progress in DNA Motor-Based Functional Systems

The designability, functionalization, and diverse secondary structures of DNA enable the construction of DNA motors with stimuli-responsiveness. Therefore, it has been widely used to fabricate functional systems or generate mechanical power under external stimuli, such as pH, light, heat, electrical, and chemical molecular signals. Furthermore, the DNA motor has also been demonstrated to promote the applications of smart devices and materials, particularly in controllable drug delivery and reversible molecular switching. In this review, we have summarized and discussed recent progress of the construction and applications of DNA motor-based functional systems, such as responsive nanodevices, modified surfaces, and hydrogels.

Stimuli-responsive metal-organic framework nanoparticles for controlled drug delivery and medical applications

Stimuli-responsive metal-organic framework nanoparticles, NMOFs, provide a versatile platform for the controlled release of drugs and biomedical applications. The porous structure of NMOFs, their biocompatibility, low toxicity, and efficient permeability turn the NMOFs into ideal carriers for therapeutic applications. Two general methods to gate the drug-loaded NMOFs and to release the loads were developed: by one method, the loaded NMOFs are coated or surface-modified with stimuli-responsive gates being unlocked in the presence of appropriate chemical (e.g., ions or reducing agents), physical (e.g., light or heat), or biomarker (e.g., miRNA or ATP) triggers. By a second approach, the drug-loaded NMOFs include encoded structural information or co-added agents to induce the structural distortion or stimulate the degradation of the NMOFs. Different chemical triggers such as pH changes, ions, ATP, or redox agents, and physical stimuli such as light or heat are applied to degrade the NMOFs, resulting in the release of the loads. In addition, enzymes, DNAzymes, and disease-specific biomarkers are used to unlock the gated NMOFs. The triggered release of drugs for cancer therapy, anti-blood clotting, and the design of autonomous insulin-delivery systems ("artificial pancreas") are discussed. Specifically, multi-drug carrier systems and functional NMOFs exhibiting dual and cooperative therapeutic functions are introduced. The future perspectives and applications of stimuli-responsive particles are addressed.

DNA-Assisted Smart Nanocarriers: Progress, Challenges, and Opportunities

Due to powerful breakthroughs in nanotechnology, smart delivery mechanisms have rapidly emerged for use in diverse applications across biomedical research and therapeutic development. Recent efforts toward understanding stimuli-responsive strategies have led to substantial improvements in their conceptual application and in vitro efficiency. Because disease targets for therapy are often localized in specific cells, organs, or tissues, an enhanced permeability and retention (EPR)-based strategy remains inadequate for accurate drug delivery and release to target regions, resulting in an insufficient drug concentration reaching the target region and undesired side effects. To address these issues, more precise and remote-controlled stimuli-responsive systems, which recognize and react to changes in the pathophysiological microenvironment, were recently elucidated as feasible on-demand drug-delivery systems. In this Perspective, we focus on progress toward stimuli-responsive drug-delivery systems that utilize dynamic DNA molecules by exploiting DNA nanotechnology. DNA structures can be precisely reconfigured by external and internal stimuli to drive the release of a loaded drug in a target region with appropriate microenvironments. We describe the chemical, physical, and biological engineering principles and strategies for constructing DNA-assisted nanocarriers. We also provide a summary of smart nanocarrier systems, organized with respect to the structural changes in the DNA strand in the microenvironment, resulting from changes in pH and temperature and the presence of intracellular oligonucleotides. To do so, we highlight recent advances in related biomedical research and applications as well as discuss major challenges and opportunities for DNA-assisted nanocarriers to guide the development of future in vivo therapies and clinical translation strategies.

Preparation of Composite Cypate Nanoparticles and Its Application in the Treatment of Pediatric Bladder Tumors

Cypate is an organic material with tumor treatment function, which has photothermal effect. Based on the characteristics of this material, this study adopted the coupling method to obtain FB-Cypate nano-microspheres, BDI-1-FB-Cypate albumin nano-microsphere diad and CPPs-BDI-1-FB-Cypate albumin nano-microsphere triad. Cypate and FB-Cypate materials were characterized by scanning TEM, particle size analyzer, and spectrophotometer. An injection-ureter introduction device was used to perfuse pediatric bladder cancer cells into the bladder cavity of nude mice, and different Cypate-type material solutions were perfused into the bladder cavity at the same time. Then, the anti-bladdertumor performance of different materials on tumor cells was compared. The test proves that the average particle diameter of FB-Cypate material is (102.3 ±8.6) nm, which can be used for near-infrared imaging, and the temperature rise is obvious under light conditions. In the test of inhibiting bladder cancer cells in children, the use of Cypate type materials can significantly inhibit the survival of bladder tumor cells, and it has less negative impact on physiological functions after surgery.

Phototriggerable Transient Electronics via Fullerene-Mediated Degradation of Polymer:Fullerene Encapsulation Layer

Transient electronics is an emerging class of electronics that has attracted a lot of attention because of its potential as an environmental-friendly alternative to the existing end-of-life product disposal or treatments. However, the controlled degradation of transient electronics under environmentally benign conditions remains a challenge. In this work, the tunable degradation of transient electronics including passive resistor devices and active memory devices was realized by photodegradable thin polymer films comprising fullerene derivatives, [6,6]-phenyl-C61-butyric acid methyl esters (PCBM). The photodegradation of polymer:PCBM under an aqueous environment is triggered by ultraviolet (UV) light. Experimental results demonstrate that the addition of PCBM in commodity polymers, including but not limited to polystyrene, results in a catalytic effect on polymer photodegradation when triggered by UV light. The degradation mechanism of transient electronics is ascribed to the photodegradation of polymer:PCBM encapsulation layers caused by the synergistic effect between UV and water exposure. The polymer:PCBM encapsulation system presented herein offers a simple way to achieve the realization of light-triggered device degradation for bioapplication and expands the material options for tailorable degradation of transient electronics.

Microfluidics for core-shell drug carrier particles - a review

Core-shell drug-carrier particles are known for their unique features. Due to the combination of superior properties not exhibited by the individual components, core-shell particles have gained a lot of interest. The structures could integrate core and shell characteristics and properties. These particles were designed for controlled drug release in the desired location. Therefore, the side effects would be minimized. So, these particles' advantages have led to the introduction of new methods and ideas for their fabrication. In the past few years, the generation of drug carrier core-shell particles in microfluidic chips has attracted much attention. This method makes it possible to produce particles at nanometer and micrometer levels of the same shape and size; it usually costs less than other methods. The other advantages of using microfluidic techniques compared to conventional bulk methods are integration capability, reproducibility, and higher efficiency. These advantages have created a positive outlook on this approach. This review gives an overview of the various fluidic concepts that are used to generate microparticles or nanoparticles. Also, an overview of traditional and more recent microfluidic devices and their design and structure for the generation of core-shell particles is given. The unique benefits of the microfluidic technique for core-shell drug carrier particle generation are demonstrated.

Polydopamine Nanoparticles Camouflaged by Stem Cell Membranes for Synergistic Chemo-Photothermal Therapy of Malignant Bone Tumors

Purpose

Nanoparticle (NP)-based chemo-photothermal therapy (CPT) has been shown to be a promising non-invasive approach for antitumor treatment. However, NPs must overcome the limitations of opsonization, clearance of the reticuloendothelial system, and ineffective targeting of tumor tissue sites. To solve these problems, stem cell membrane (SCM)-camouflaged polydopamine nanoparticles (PDA@SCM NPs) carrying the hydrophobic anticancer drug 7-ethyl-10-hydroxycamptothecin (SN38) were constructed for CPT of malignant bone tumors.

Methods

We developed umbilical-cord mesenchymal stem cell membrane-coated polydopamine nanoparticles encapsulating SN38 (PDA-SN38@SCM NPs) as an efficient tumor-targeting drug-delivery platform for CPT of malignant bone tumors. We characterized PDA@SCM NPs and evaluated the biocompatibility and anti-phagocytosis properties of PDA@SCM NPs. The antitumor activity of PDA-SN38@SCM NPs was evaluated in MG63 lines and an MG63 xenograft model in mice.

Results

Synthesized PDA-SN38@SCM NPs retained an excellent photothermal effect after SN38 loading. The drug release of PDA-SN38@SCM NPs could be triggered by near-infrared irradiation and an acidic stimulus. PDA@SCM NPs exhibited lower nonspecific macrophage uptake, longer retention in blood, and more effective accumulation at tumor sites than that shown by PDA NPs. Confocal laser scanning microscopy (CLSM) and flow cytometry showed that MG63 cells took up more PDA-SN38@SCM NPs than PDA-SN38 NPs. In vitro and in vivo antitumor studies demonstrated the outstanding performance of PDA-SN38@SCM NPs in synergistic CPT for bone tumors.

Conclusion

PDA-SN38@SCM NPs demonstrated an extraordinary synergistic CPT effect and could be a promising strategy for the treatment of malignant bone tumors.

Aptamer-Functionalized Nanoparticles in Targeted Delivery and Cancer Therapy

Using nanoparticles to carry and delivery anticancer drugs holds much promise in cancer therapy, but nanoparticles per se are lacking specificity. Active targeting, that is, using specific ligands to functionalize nanoparticles, is attracting much attention in recent years. Aptamers, with their several favorable features like high specificity and affinity, small size, very low immunogenicity, relatively low cost for production, and easiness to store, are one of the best candidates for the specific ligands of nanoparticle functionalization. This review discusses the benefits and challenges of using aptamers to functionalize nanoparticles for active targeting and especially presents nearly all of the published works that address the topic of using aptamers to functionalize nanoparticles for targeted drug delivery and cancer therapy.

Nucleic acid biohybrid nanocarriers with high-therapeutic payload and controllable extended release of daunomycin for cancer therapy

We have developed a novel, nanosized drug carrier with high-therapeutic payload, controllable release, and the potential for active tumor targeting. It consists of a 15 nm gold nanoparticle with dense surface loading of DNA duplexes. We utilize the natural intercalating behavior of daunomycin to load the drug between DNA base pairs. We obtained a high-therapeutic payload of >1,000 drug molecules per gold nanoparticle (AuNP), one of the highest loadings reported in literature to date. We have engineered unique DNA sequences to control release of daunomycin for over 48 hr and show higher cell death compared to equivalent concentrations of free daunomycin. We have also explored cell internalization mechanisms to identify the pathways by which our gold nanoparticles enter the cell. This nanocarrier is in the ideal size range of 16-100 nm in diameter to utilize the enhanced permeability and retention effect for passive targeting to tumors. Our AuNP platform is effective as a therapeutic drug delivery device and can easily incorporate any aptamer of choice through complementary base pairing. Our work has produced an innovative nanoscale drug-delivery platform potentially leading to personalized cancer therapies through careful selection of aptamers and an adjustable drug release profile.

Photocontrolled activation of small molecule cancer therapeutics

Cancer remains one of the leading causes of death worldwide. Conventional treatment of the disease is comprised of chemotherapy, radiation and surgery among other treatment approaches. Chemotherapy is plagued by multiple side-effects caused due to non-specific drug action. Light-based therapies offer an alternative treatment approach that can be fine tuned to achieve the desired effect to treat the disease and address challenges posed by chemotherapeutic side-effects. Photodynamic therapy (PDT) is one of the light mediated treatment modalities that has been successfully applied to treat superficial malignancies with high-efficiency, although its dependence on normoxic conditions limits its efficiency to treat deep-seated tumors. On the other hand, light-sensitive drug-mimetics and drug-release platforms have been deemed efficient in preclinical settings to induce cancer cell death with minimal collateral damage. Drawing from about a decade's worth of examples, we highlight the application of photosensitive molecules as an alternative therapeutic option to PDT and describe their designs that influence the biology of the cancer cells, in turn affecting their viability with high spatio-temporal control.

Photosensitive properties, synergistic antibacterial abilities of intelligent response-type self-assembled nanoparticle TiO2@V2O5

Representative pathogenic bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are widespread in nature and pose a threat to human health. To control the propagation of these pathogens from the source, the key is to design broad-spectrum antibacterial materials to reduce the serious damage of pathogenic bacteria. At present, more and more nanoparticles are widely researched and applied due to their multi-pathway antibacterial properties, such as regulating physiology, biochemistry and physical chemistry. In this work, we synthesized a uniformly dispersed and stable spherical nanoparticle (TiO₂@V₂O₅) synthesized by self-assembly of tianium dioxide and vanadium pentoxide. Based on its excellent photosensitive properties, TiO₂@V₂O₅ nanoparticles have showed excellent antibacterial properties under the light irradiation due to the production of hydroxyl radicals in antibacterial and mechanism tests. In addtion, related cell and plant experiments have showed that TiO₂@V₂O₅ nanoparticles are excellent biocompatible materials, it could be widely used in environmental pollution control, limiting the serious damage caused by pathogens.

Gold-based Inorganic Nanohybrids for Nanomedicine Applications

Noble metal Au nanoparticles have attracted extensive interests in the past decades, due to their size and morphology dependent localized surface plasmon resonances. Their unique optical property, high chemical stability, good biocompatibility, and easy functionalization make them promising candidates for a variety of biomedical applications, including bioimaging, biosensing, and cancer therapy. With the intention of enhancing their optical response in the near infrared window and endowing them with additional magnetic properties, Au nanoparticles have been integrated with other functional nanomaterials that possess complementary attributes, such as copper chalcogenides and magnetic metal oxides. The as constructed hybrid nanostructures are expected to exhibit unconventional properties compared to their separate building units, due to nanoscale interactions between materials with different physicochemical properties, thus broadening the application scope and enhancing the overall performance of the hybrid nanostructures. In this review, we summarize some recent progresses in the design and synthesis of noble metal Au-based hybrid inorganic nanostructures for nanomedicine applications, and the potential and challenges for their clinical translations.

Integrating Artificial Intelligence and Nanotechnology for Precision Cancer Medicine

Artificial intelligence (AI) and nanotechnology are two fields that are instrumental in realizing the goal of precision medicine-tailoring the best treatment for each cancer patient. Recent conversion between these two fields is enabling better patient data acquisition and improved design of nanomaterials for precision cancer medicine. Diagnostic nanomaterials are used to assemble a patient-specific disease profile, which is then leveraged, through a set of therapeutic nanotechnologies, to improve the treatment outcome. However, high intratumor and interpatient heterogeneities make the rational design of diagnostic and therapeutic platforms, and analysis of their output, extremely difficult. Integration of AI approaches can bridge this gap, using pattern analysis and classification algorithms for improved diagnostic and therapeutic accuracy. Nanomedicine design also benefits from the application of AI, by optimizing material properties according to predicted interactions with the target drug, biological fluids, immune system, vasculature, and cell membranes, all affecting therapeutic efficacy. Here, fundamental concepts in AI are described and the contributions and promise of nanotechnology coupled with AI to the future of precision cancer medicine are reviewed.

In Vivo Imaging of Hypoxia Associated with Inflammatory Bowel Disease by a Cytoplasmic Protein-Powered Fluorescence Cascade Amplifier

Accurate and sensitive imaging of hypoxia associated with inflammatory bowel disease (IBD) is significant for the precise diagnosis and treatment of this disease, but it remains a challenge for traditional hypoxia-activatable fluorescence probes because of a more moderate hypoxic state during IBD than under other pathological conditions. To address this issue, herein, we designed a hypoxia-activatable and cytoplasmic protein-powered fluorescence cascade amplifier, named HCFA, to image hypoxia associated with IBD in vivo. In our design, a 4-aminobenzoic acid (azo)-modified mesoporous silica nanoparticle (MSN) was used as a container to load black hole quencher 2 (BHQ2) and cytoplasmic protein-binding squarylium dye (SQ); then, the β-cyclodextrin polymer (β-CDP) combined with azo through a host-guest interaction to form HCFA. Upon passive stagnation in the inflamed tissue of IBD, the azo band would be cleaved under a hypoxic microenvironment, and SQ was released to activate the fluorescence of HCFA. Moreover, the unconstrained SQ can bind with cytoplasmic protein to exhibit drastic fluorescence intensity enhancement, realizing the fluorescence signal amplification for imaging of hypoxia. When one takes advantage of the large load capacity of MSN and the unique property of SQ, HCFA can sense oxygen levels in the range of 0% to 10%. Meanwhile, the fluorescence imaging results demonstrate that HCFA can sensitively distinguish different levels of cellular hypoxia and monitor the variations of hypoxia in vivo, highlighting HCFA as a promising tool for the detection of hypoxia associated with IBD.

Studies on interaction potency model based on drug synergy and therapeutic potential of triple stimuli-responsive delivery of doxorubicin and 5-fluoro-2-deoxyuridine against lymphoma using disulfide-bridged cysteine over mesoporous silica nanoparticles

A triple stimuli-responsive drug delivery platform involving doxorubicin, 5-fluoro-2-deoxy uridine and folic acid was fabricated on mesoporous silica nanoparticles for targeting delivery against a highly aggressive murine lymphoma called Dalton's lymphoma. Fabrication of the unique construct by amalgamating active and passive targeting mechanisms offers a novel hyper-chimeric platform for a stimuli-responsive drug delivery system. The novel construct enables efficient and precise delivery of the precious cargo to the tumor sites. Active targeting by folic acid directs the doxorubicin and 5-fluoro-2-deoxy uridine in the close proximities of the tumor cells, causing efficient killing and significant growth inhibition. Isobologram models, zero interaction potency dose-response surface plots and matrices were generated to evaluate the combination synergism of the two drugs. Therapy with the dual drug-bearing construct in mice with established tumors significantly reduced the tumor load and enhanced the survival of the animals compared with the untreated control. Therapy with the dual delivery system also augmented the innate and adaptive immune defense mechanisms of the treated animals. CD8⁺ T cells, natural killer cells and the dendritic cells from the treated group following successful therapy with the novel construct showed enhanced cytotoxicity and growth inhibitory capacities against DL tumor cells.

Magnetic and light-responsive nanogels based on chitosan functionalized with Au nanoparticles and poly(N-isopropylacrylamide) as a remotely triggered drug carrier

Synthesis of thermosensitive nanogels based on functionalized chitosan with Au nanoparticles (NPs) and poly(NIPAM) to release of drug molecules under light exposure.

Realization of red plasmon shifts by the selective etching of Ag nanorods

The red plasmon shifts is realized through selective deposition of Au atoms and etching of Ag atoms on the Ag nanorods.

Core–shell nanoparticles used in drug delivery-microfluidics: a review

Developments in the fields of lab-on-a-chip and microfluidic technology have benefited nanomaterial production processes due to fluid miniaturization. The ability to acquire, manage, create, and modify structures on a nanoscale is of great interest in scientific and technological fields. Recently, more attention has been paid to the production of core–shell nanomaterials because of their use in various fields, such as drug delivery. Heterostructured nanomaterials have more reliable performance than the individual core or shell materials. Nanoparticle synthesis is a complex process; therefore, various techniques exist for the production of different types of nanoparticles. Among these techniques, microfluidic methods are unique and reliable routes, which can be used to produce nanoparticles for drug delivery applications.

Developments in the fields of lab-on-a-chip and microfluidic technology have benefited nanomaterial production processes due to fluid miniaturization.

Biointerface engineering nanoplatforms for cancer-targeted drug delivery

Over the past decade, nanoparticle-based therapeutic modalities have become promising strategies in cancer therapy. Selective delivery of anticancer drugs to the lesion sites is critical for elimination of the tumor and an improved prognosis. Innovative design and advanced biointerface engineering have promoted the development of various nanocarriers for optimized drug delivery. Keeping in mind the biological framework of the tumor microenvironment, biomembrane-camouflaged nanoplatforms have been a research focus, reflecting their superiority in cancer targeting. In this review, we summarize the development of various biomimetic cell membrane-camouflaged nanoplatforms for cancer-targeted drug delivery, which are classified according to the membranes from different cells. The challenges and opportunities of the advanced biointerface engineering drug delivery nanosystems in cancer therapy are discussed.

Aptamers Chemistry: Chemical Modifications and Conjugation Strategies

Soon after they were first described in 1990, aptamers were largely recognized as a new class of biological ligands that can rival antibodies in various analytical, diagnostic, and therapeutic applications. Aptamers are short single-stranded RNA or DNA oligonucleotides capable of folding into complex 3D structures, enabling them to bind to a large variety of targets ranging from small ions to an entire organism. Their high binding specificity and affinity make them comparable to antibodies, but they are superior regarding a longer shelf life, simple production and chemical modification, in addition to low toxicity and immunogenicity. In the past three decades, aptamers have been used in a plethora of therapeutics and drug delivery systems that involve innovative delivery mechanisms and carrying various types of drug cargos. However, the successful translation of aptamer research from bench to bedside has been challenged by several limitations that slow down the realization of promising aptamer applications as therapeutics at the clinical level. The main limitations include the susceptibility to degradation by nucleases, fast renal clearance, low thermal stability, and the limited functional group diversity. The solution to overcome such limitations lies in the chemistry of aptamers. The current review will focus on the recent arts of aptamer chemistry that have been evolved to refine the pharmacological properties of aptamers. Moreover, this review will analyze the advantages and disadvantages of such chemical modifications and how they impact the pharmacological properties of aptamers. Finally, this review will summarize the conjugation strategies of aptamers to nanocarriers for developing targeted drug delivery systems.