Multifunctional envelope-type mesoporous silica nanoparticles for pH-responsive drug delivery and magnetic resonance imaging

Introduction of magnetic and supermagnetic nanoparticles in new approach of targeting drug delivery and cancer therapy application

In this article, the recent applications of different types of magnetic nanoparticles such as α-Fe₂O₃ (hematite), γ-Fe₂O₃ (maghemite), Fe₃O₄ (magnetite), hexagonal (MFe₁₂O₁₉), garnet (M₃Fe₅O₁₂) and spinel (MFe₂O₄), where M represents one or more bivalent transition metals (Mn, Fe, Co, Ni, Ba, Sr, Cu, and Zn), and different materials for coating the surface of magnetic nanoparticles like poly lactic acid (PLA), doxorubicin hydrophobic (DOX-HCL), paclitaxel (PTX), EPPT-FITC, oleic acid, tannin, 3-Aminopropyltriethoxysilane (APTES), multi-wall carbon nanotubes (CNTs), polyethylenimine (PEI) and polyarabic acid in drug delivery, biomedicine and treatment of cancer, specially chemotherapy, are reviewed. MNPs possess large surface area to volume ratios because of their nano-size, low surface charge at physiological pH and they aggregate easily in solution due to their essential magnetic nature. These materials are widely used in biology and medicine in many cases. One targeted delivery technique that has gained prominence in recent years is the use of magnetic nanoparticles. In these systems, therapeutic compounds are attached to biocompatible magnetic nanoparticles and magnetic fields generated outside the body are focused on specific targets in vivo. The fields capture the particle complex, resulting in enhanced delivery to the target site. Also, the application of brand new supermagnetic nanoparticles, like Ba,SrFe₁₂O₁₉, is considered and studied in this paper.

Magnetic nanoparticles in nanomedicine: a review of recent advances

Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticles (MNPs) are one important class of nanomaterials that have been widely studied for their potential applications in nanomedicine. Due to the fact that MNPs can be detected and manipulated by remote magnetic fields, it opens a wide opportunity for them to be used in vivo. Nowadays, MNPs have been used for diverse applications including magnetic biosensing (diagnostics), magnetic imaging, magnetic separation, drug and gene delivery, and hyperthermia therapy, etc. Specifically, we reviewed some emerging techniques in magnetic diagnostics such as magnetoresistive (MR) and micro-Hall (μHall) biosensors, as well as the magnetic particle spectroscopy, magnetic relaxation switching and surface enhanced Raman spectroscopy (SERS)-based bioassays. Recent advances in applying MNPs as contrast agents in magnetic resonance imaging and as tracer materials in magnetic particle imaging are reviewed. In addition, the development of high magnetic moment MNPs with proper surface functionalization has progressed exponentially over the past decade. To this end, different MNP synthesis approaches and surface coating strategies are reviewed and the biocompatibility and toxicity of surface functionalized MNP nanocomposites are also discussed. Herein, we are aiming to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications of MNPs. This review is not only to provide in-depth insights into the different synthesis, biofunctionalization, biosensing, imaging, and therapy methods but also to give an overview of limitations and possibilities of each technology.

Tumor self-responsive upconversion nanomedicines for theranostic applications

To date, malignant tumors continue to be the most lethal disease, causing more than 8.2 million deaths worldwide each year. In recent years, nanostructures based on rare-earth upconversion luminescent nanoparticles have shown significant advantages in the integration of multimodal imaging and therapy. Compared with normal tissues, the tumor microenvironment (TME) exhibits unique characteristics including high interstitial fluid pressure, abnormal blood vessels, a hypoxic and slightly acidic environment, and high levels of glutathione (GSH) and hydrogen peroxide (H2O2). According to these characteristics, increasing attention in the antitumor field has been given to designing nanomedicines with specific responses to the TME based on rare-earth upconversion nanoparticles (UCNPs) and to achieving efficient tumor diagnosis and treatment under the premise of reducing side effects. Nevertheless, a review that systematically summarizes TME-responsive upconversion nanomedicines (UCNMs) for realizing tumor self-enhanced theranostics has not been published to date. In this review, we summarize the recent progress made in UCNP-based nanotherapeutics by highlighting the increasingly developing trend of TME-responsive UCNMs. The general characteristics of the TME are introduced in detail and their utilization in designing TME-responsive UCNMs is systematically discussed. Based on NIR light-excited optical imaging, we discuss the superiority of UCNMs when applied in tumor theranostics with an emphasis on how to use them to realize TME-mediated multimodal imaging-guided therapy.

Functionalized mesoporous silica nanoparticles in anticancer therapeutics

The application of nanomedicines in tumor targeting and attaining meaningful therapeutic benefits for the treatment of cancers has been going on for almost two decades. Beyond the lipidic and polymeric nanomedicines-based passive and active targeting, the quest for inventing the new generation of carriers has no end. This has lead to the evolution of some of the unique carrier systems with supramolecular assembly structures. Mesoporous nanoparticulate systems (MSNPs) are the recently explored substances with favorable potential for drug delivery and drug targeting applications especially in cancer chemotherapeutics. Notwithstanding their physical properties that makes them a suitable carrier for cancer treatment, but their outstanding ability towards chemical functionalization helps in delivering the imaging agents for diagnostic applications. MSNPs can improve the dissolution rate and systemic availability of the poorly water soluble drugs due to their mesoporous structures. Besides, guest molecules including targeting ligands, biomimetic agents, fluorescent dyes, and biocompatible polymers can be efficiently encapsulated in their tunable porous structure for targeting purpose. Some special features of the MSNPs which make them one of the highly effective nanocarrier systems include their ability to encapsulate non-crystalline drugs in their mesopores, high dispersion ability as a function of large surface area and wetting properties. For anticancer drug delivery, MSNPs are worthful to provide excellent drug loading capacity and endocytotic behavior. Moreover, the external surface of MSNPs can be precisely modified for tumor-recognition and developing sensitivity of the antitumor agents towards the cancer cells. Owing to the innumerable applications of MSNPs till now in cancer treatment, the present article particularly focuses to provide an overview account with complete details on the topic to make the readers abreast with details on physiochemical and material properties of MSNPs, their applications and current innovations for the purpose.

Platelet-Membrane-Camouflaged Black Phosphorus Quantum Dots Enhance Anticancer Effect Mediated by Apoptosis and Autophagy

Hederagenin (HED) has poor anticancer activity whose mechanism remains unclear and unsystematic. Free drugs for cancer treatment exhibit disadvantages such as poor targeting and efficacy. To address this problem, we constructed a nanoplatform of black phosphorus quantum dots (BPQDs) camouflaged with a platelet membrane (PLTm) carrying HED, termed PLT@BPQDs-HED. PLTm vesicles serve as a shell to encapsulate multiple high-efficiency drug-loaded nanocores, which can target tumor sites and significantly improve antitumor activity. Compared with free HED, this platform significantly reduced tumor cell viability and the mitochondrial membrane potential (MMP), while increasing the production of intracellular reactive oxygen species (ROS). The platform also significantly increased the amounts of terminal deoxyribonucleotide transferase mediated dUTP nick-end-labeling (TUNEL)-positive cells and decreased the number of Ki-67-positive cells. In addition, the platform upregulated proapoptotic factor Bax, downregulated the anti-apoptotic molecule Bcl-2, activated Caspase-9 and Caspase-3, and stimulated Cytochrome C release. Moreover, the platform promoted the formation of autophagosomes, upregulated Beclin-1, and promoted LC3-I conversion into LC3-II. This study demonstrated that the above platform significantly enhances tumor targeting and promotes mitochondria-mediated cell apoptosis and autophagy in tumor cells.

Current trends and challenges in cancer management and therapy using designer nanomaterials

Nanotechnology has the potential to circumvent several drawbacks of conventional therapeutic formulations. In fact, significant strides have been made towards the application of engineered nanomaterials for the treatment of cancer with high specificity, sensitivity and efficacy. Tailor-made nanomaterials functionalized with specific ligands can target cancer cells in a predictable manner and deliver encapsulated payloads effectively. Moreover, nanomaterials can also be designed for increased drug loading, improved half-life in the body, controlled release, and selective distribution by modifying their composition, size, morphology, and surface chemistry. To date, polymeric nanomaterials, metallic nanoparticles, carbon-based materials, liposomes, and dendrimers have been developed as smart drug delivery systems for cancer treatment, demonstrating enhanced pharmacokinetic and pharmacodynamic profiles over conventional formulations due to their nanoscale size and unique physicochemical characteristics. The data present in the literature suggest that nanotechnology will provide next-generation platforms for cancer management and anticancer therapy. Therefore, in this critical review, we summarize a range of nanomaterials which are currently being employed for anticancer therapies and discuss the fundamental role of their physicochemical properties in cancer management. We further elaborate on the topical progress made to date toward nanomaterial engineering for cancer therapy, including current strategies for drug targeting and release for efficient cancer administration. We also discuss issues of nanotoxicity, which is an often-neglected feature of nanotechnology. Finally, we attempt to summarize the current challenges in nanotherapeutics and provide an outlook on the future of this important field.

Controlled drug delivery systems for cancer based on mesoporous silica nanoparticles

The implementation of nanotechnology in medicine has opened new research horizons particularly in the field of therapeutic delivery. Mesoporous silica particles have emerged as biocompatible drug delivery systems with an enormous potential in the treatment of cancer among many other pathologies. In this review, we focus on the unique properties of these particles as chemotherapy delivery carriers. Here, we summarize the general characteristics of these nanomaterials - including their physicochemical properties and customizable surfaces - different stimuli that can be used to trigger targeted drug release, biocompatibility and finally, the drawbacks of these types of nanomaterials, highlighting some of the most important features of mesoporous silica nanoparticles in drug delivery.

Recent advancements in mesoporous silica nanoparticles towards therapeutic applications for cancer

Recently, drug delivery systems based on nanotechnology have received great attention in cancer therapeutics and diagnostics since they can not only improve the treatment efficacy but also reduce the side effects. Among them, mesoporous silica nanoparticles (MSNs) with large surface area, high pore volume, tunable pore size, abundant surface chemistry, and acceptable biocompatibility exhibit unique advantages and are considered as promising candidates for cancer diagnosis and therapy. In this review, we update the recent progress on MSN-based systems for cancer treatment purposes. We also discuss the drug loading mechanism of MSNs, stimuli-responsive drug release, and surface modification strategies for improving biocompatibility, and targeting functionalities. STATEMENT OF SIGNIFICANCE: The development of MSN-based delivery systems that can be used in both diagnosis and treatment of cancer has attracted tremendous interest in the past decade. MSN-based delivery systems can improve therapeutic efficacy and reduce cytotoxicity to normal tissue. To further improve the in vivo properties of MSNs and potential translation to the clinics, it is critical to design MSNs with appropriate surface engineering and desirable cancer targeting. This review is intended to provide the readers a comprehensive background of the vast literature till date on silica-based drug delivery systems, and to inspire further innovations in silica nanomedicine in the future.

Challenges and Recent Progress in Oral Drug Delivery Systems for Biopharmaceuticals

Routes of drug administration and the corresponding physicochemical characteristics of a given route play significant roles in therapeutic efficacy and short term/long term biological effects. Each delivery method has favorable aspects and limitations, each requiring a specific delivery vehicles design. Among various routes, oral delivery has been recognized as the most attractive method, mainly due to its potential for solid formulations with long shelf life, sustained delivery, ease of administration and intensified immune response. At the same time, a few challenges exist in oral delivery, which have been the main research focus in the field in the past few years. The present work concisely reviews different administration routes as well as the advantages and disadvantages of each method, highlighting why oral delivery is currently the most promising approach. Subsequently, the present work discusses the main obstacles for oral systems and explains the most recent solutions proposed to deal with each issue.

Tumor-specific macrophage targeting through recognition of retinoid X receptor beta

Macrophages play important and diverse roles during cancer progression. However, cancer therapies based on macrophage modulation are lacking in tools that can recognize and deliver therapeutic payloads to macrophages in a tumor-specific manner. As a result, treatments tend to interfere with normal macrophage functions in healthy organs. We previously identified a macrophage-binding peptide, termed CRV. Here, we show that upon systemic administration into tumor-bearing mice, CRV selectively homes to tumors, extravasates, and preferentially binds to macrophages within. CRV exhibits a higher affinity for tumor macrophages than for other cells in tumors or for other macrophage types elsewhere in the body. We further identified and validated retinoid X receptor beta (RXRB) as the CRV receptor. Intriguingly, although it is known as a nuclear receptor, RXRB shows a prominent cell surface localization that is largely restricted to tumor macrophages. Systemic administration of anti-RXRB antibodies also results in tumor-selective binding to macrophages similar to CRV. Lastly, we demonstrate the ability of CRV to improve the delivery of nano-carriers into solid tumors and macrophages within. In summary, we describe here a novel cell surface marker and targeting tools for tumor macrophages that may aid in future development of macrophage-modulatory cancer therapies.

d-Glucose recognition based on phenylboronic acid-functionalized polyoligomeric silsesquioxane fluorescent probe

We report a new strategy to synthesize hybrid fluorescent nanosensors consisting of phenylboronic acid-functionalized POSS (POSS-PBA) and diol-modified 8-anilino-1-naphthalenesulfonic acid (ANSA (a fluorescent dye)) for the detection of the biologically important d-glucose. The probe was characterized by FT-IR and ¹H NMR analyses, and the photoluminescence intensity was measured under various conditions to confirm its glucose sensing ability. Our POSS-APBA-dye probe could detect glucose at concentrations of 0-20 mg/mL, with a good linear relationship even at low glucose concentrations of 0-1 mg/mL. The properties of the POSS-APBA-dye probe were evaluated and compared with those of an APBA-dye probe. The glucose sensing ability of our POSS-APBA-dye probe was largely unaffected by the presence of interfering substances. The probe showed high sensing ability in a pH 5 environment and long-term (approximately 40 days) fluorescence stability.

Functionalized mesoporous silica nanoparticles and biomedical applications

Since the first report in early 1990s, mesoporous silica nanoparticles (MSNs) have progressively attracted the attention of scientists due to their potential applications in physic, energy storage, imaging, and especially in biomedical engineering. Owning the unique physiochemical properties, such as highly porosity, large surface area and pore volume, functionalizable, tunable pore and particle sizes and biocompatibility, and high loading cavity, MSNs offer efficient encapsulation and then controlled release, and in some cases, intracellular delivery of bioactive molecules for biomedical applications. During the last decade, functionalized MSNs that show respond upon the surrounding stimulus changes, such as temperature, pH, redox, light, ultrasound, magnetic or electric fields, enzyme, redox, ROS, glucose, and ATP, or their combinations, have continuously revolutionized their potential applications in biomedical engineering. Therefore, this review focuses on discussion the recent fabrication of functionalized MSNs and their potential applications in drug delivery, therapeutic treatments, diagnostic imaging, and biocatalyst. In addition, some potential clinical applications and challenges will also be discussed.

Versatile Nanocarrier Based on Functionalized Mesoporous Silica Nanoparticles to Codeliver Osteogenic Gene and Drug for Enhanced Osteodifferentiation

To achieve enhanced stimulatory effects on the osteogenic differentiation of stem cells, the combination of dual factors with synergistic bioactivity has been regarded as the most effective and powerful strategy. In this study, polylysine-modified polyethylenimine (PEI-PLL) copolymers with various molecular weight PEI blocks were first synthesized and evaluated focusing on their cytotoxicity and gene transfection efficiency, and the results demonstrated that the synthesized copolymer PEI-PLL-25k (synthesized using 25 kDa PEI) exhibited lower cytotoxicity and higher in vitro transfection efficiency than commercial PEI-25k (M_w = 25 kDa). In order to effectively load and deliver plasmid DNA and osteogenic drug dexamethasone (DEX), PEI-PLL-25k copolymer and arginine-glycine-aspartate (RGD) peptide were successively anchored onto the surface of mesoporous silica nanoparticles (MSNs) to construct the dual-factor delivery system, which allows the surface adsorption of DNA and DEX loading in the mesopores of MSNs. The modification of PEI-PLL-25k copolymer and RGD on nanoparticles was successfully characterized by various techniques. The functionalized MSNs with RGD conjugation on the surface showed good cytocompatibility as evidenced by in vitro cell viability assays and cytoskeleton observation. The dual-factor delivery system could quickly release plasmid DNA (pDNA), while releasing DEX in a sustained manner. When cultured with the vector bearing bone morphogenetic protein-2 (BMP-2) pDNA, the transfected bone mesenchymal stem cells (BMSCs) were capable of expressing BMP-2 protein. With the simultaneous delivery of DEX and the BMP-2 gene, this dual-factor delivery system could significantly enhance the level of osteogenic differentiation of BMSCs, as demonstrated by in vitro results of alkaline phosphatase (ALP) activity, expression of osteo-related genes, and calcium deposition. Therefore, the versatile functionalized MSNs nanocarrier for codelivery of osteogenic gene and drug may be considered as a promising dual-delivery system to synergistically enhance the osteogenic outcomes of stem cells.

Core–shell noble-metal@zeolitic-imidazolate-framework nanocarriers with high cancer treatment efficiency in vitro

Core–shell Au@zeolitic-imidazolate-framework nanocarriers with high drug-loading, controlled drug release properties, and high cancer treatment efficiency.

Acid-breakable TPGS-functionalized and diallyl disulfide-crosslinked nanogels for enhanced inhibition of MCF-7/ADR solid tumours

Herein, the dual-functionalized nanogels were used for multidrug resistance (MDR) solid tumour therapy by combining ROS with inhibition of efflux.

Theragnostic potentials of core/shell mesoporous silica nanostructures

Theragnostics is considered as an emerging treatment strategy that integrates therapeutics and diagnostics thus allowing delivery of therapeutics and simultaneous monitoring of the progression of treatment. Among the different types of inorganic nanomaterials that are being used for nanomedicine, core shell mesoporous silica nanoparticles have emerged as promising multifunctional nanoplatform for theragnostic application. Research in the design of core/shell mesoporous silica nanoparticles is steadily diversifying owing to the various interesting properties of these nanomaterials that are advantageous for advanced biomedical applications. Core/shell mesoporous silica nanoparticles, have garnered substantial attention in recent years because of their exceptional properties including large surface area, low density, ease of functionalization, high loading capacity of drugs, control of the morphology, particle size, tunable hollow interior space and mesoporous shell and possibility of incorporating multifunctional interior core material. In the past decade researcher's demonstrated tremendous development in design of functionalized core/shell mesoporous silica nanoparticles with different inorganic functional nanomaterial incorporated into mesoporous nanosystem for simultaneous therapeutic and diagnostic (theragnostic) applications in cancer. In this review, we recapitulate the progress in commonly used synthetic strategies and theragnostic applications of core/shell mesoporous silica nanoparticles with special emphasis on therapeutic and diagnostic modalities. Finally, we discuss the challenges and some perspectives on the future research and development of theragnostic core/shell mesoporous silica nanoparticles.

Recent Development of pH-Responsive Polymers for Cancer Nanomedicine

Cancer remains a leading cause of death worldwide with more than 10 million new cases every year. Tumor-targeted nanomedicines have shown substantial improvements of the therapeutic index of anticancer agents, addressing the deficiencies of conventional chemotherapy, and have had a tremendous growth over past several decades. Due to the pathophysiological characteristics that almost all tumor tissues have lower pH in comparison to normal healthy tissues, among various tumor-targeted nanomaterials, pH-responsive polymeric materials have been one of the most prevalent approaches for cancer diagnosis and treatment. In this review, we summarized the types of pH-responsive polymers, describing their chemical structures and pH-response mechanisms; we illustrated the structure-property relationships of pH-responsive polymers and introduced the approaches to regulating their pH-responsive behaviors; we also highlighted the most representative applications of pH-responsive polymers in cancer imaging and therapy. This review article aims to provide general guidelines for the rational design of more effective pH-responsive nanomaterials for cancer diagnosis and treatment.

Synthesis and Biomedical Applications of Multifunctional Nanoparticles

The accumulated knowledge of nanoparticle (NP) synthesis for the last 30 years has enabled the development of functional NPs for biomedical applications. Especially, NPs with multifunctional capabilities are gaining popularity as the demand for versatile and efficient NP agents increases. Various combinations of functional materials are integrated to form multicomponent NPs with designed size, structure, and multifunctionality. Their use as diagnostic and/or therapeutic tools is demonstrated, suggesting their application potentials in healthcare and medical practice. Here, the recent achievements in the synthesis and biomedical applications of multifunctional NPs are summarized. Starting with a brief overview regarding the advances in NP synthesis and accompanying progress in nanobiotechnology, various components to construct the multifunctional NP agents, which include polymers and mesoporous, magnetic, catalytic, and semiconducting NPs, are discussed together with their overall integration forms, such as NP assembly, hollow/porous structures, or hybrid/doped systems. Following the explanation of the features that multifunctional NP agents can offer, an outlook and a brief comment regarding the future research directions are provided.

Delivery of Doxorubicin Using Double-Layered Core-Shell Nanocarrier Based on Magnetic Fe3O4 Core and Salep Shells

Herein, we developed a magnetic drug delivery system based on magnetic Fe₃O₄ nanoparticles with double shells of modified salep polysaccharide for the delivery of doxorubicin (Dox). The drug-loaded nanocarrier was synthesized in an easy way, and large amounts of drug molecules were loaded into the nanocarrier. The drug-loaded nanocarrier showed excellent pH responsibility in vitro, and large amounts of Dox were released at lower pH (60% release), whereas the nanocarrier was stable at neutral pH. The hemolysis assay results showed that the nanocarrier has negligible hemolytic effects on human red blood cells and showed good biocompatibility. Moreover, the result of coagulation assays showed that the nanocarrier was not active in any coagulation pathways. Cytotoxicity assays of nanocarrier and drug-loaded nanocarrier toward HeLa cells demonstrated that the nanocarrier has negligible toxicity, whereas the drug-loaded nanocarrier kills more than 90% of cells during 48 h. The flow cytometry analysis also showed that the uptake of drug-loaded nanocarrier into the cancerous cells is time-dependent and higher concentrations of drug internalized into the cells at longer incubation time. On the basis of the results, we suggest that the present nanocarrier can be applicable for in vivo drug delivery as an easy-made and cheap nanocarrier.

Synchronized Ratiometric Codelivery of Metformin and Topotecan through Engineered Nanocarrier Facilitates In Vivo Synergistic Precision Levels at Tumor Site

The combination of metabolic modulators with chemotherapy holds vast promise for effective inhibition of tumor progression and invasion. Herein, a ratiometric codelivery platform is developed for metformin (MET), a known metabolic modulator and topotecan (TPT), a chemotherapeutic drug, by engineering lipid bilayer-camouflaged mesoporous silica nanoparticles (LB-MSNs). In an attempt to deliver and maintain high tumor site concentrations of MET and TPT, a novel ion pairing-assisted loading procedure is developed using pamoic acid (PA) as an in situ trapping agent. PA, a hydrophobic counterion, increases the hydrophobicity of MET and TPT and facilitates MSNs with exceptionally high payload capacity (>40 and 32 wt%, respectively) and controlled release profile. Further, the synergy between MET and TPT determined by a modeling approach helps to afford synchronized delivery of both the drugs. Coloaded MET and TPT LB-MSNs present synergistic cytotoxicity against MDA-MB-231/4T1 cells and effectively promote apoptosis via mitochondrial membrane depolarization and cell cycle arrest. Extended pharmacokinetic profiles in preclinical models with fourfold to sevenfold longer circulation half-life and 7.5-100 times higher tumor site concentrations correspond to a significant increase in pharmacodynamic efficacy. Taken together, the developed codelivery approach effectively addresses the challenges in the chemotherapeutic efficacy of MET and TPT collectively.

Porous Inorganic Carriers Based on Silica, Calcium Carbonate and Calcium Phosphate for Controlled/Modulated Drug Delivery: Fresh Outlook and Future Perspectives

Porous inorganic nanostructured materials are widely used nowadays as drug delivery carriers due to their adventurous features: suitable architecture, large surface area and stability in the biological fluids. Among the different types of inorganic porous materials, silica, calcium carbonate, and calcium phosphate have received significant attention in the last decade. The use of porous inorganic materials as drug carriers for cancer therapy, gene delivery etc. has the potential to improve the life expectancy of the patients affected by the disease. The main goal of this review is to provide general information on the current state of the art of synthesis of the inorganic porous particles based on silica, calcium carbonate and calcium phosphate. Special focus is dedicated to the loading capacity, controllable release of drugs under internal biological stimuli (e.g., pH, redox, enzymes) and external noninvasive stimuli (e.g., light, magnetic field, and ultrasound). Moreover, the diverse compounds to deliver with silica, calcium carbonate and calcium phosphate particles, ranging from the commercial drugs to genetic materials are also discussed.

Nanosizing Noncrystalline and Porous Silica Material-Naturally Occurring Opal Shale for Systemic Tumor Targeting Drug Delivery

Opal shale, as a naturally occurring and noncrystalline silica material with porous structure, has the potential to be a drug delivery carrier. In this study, we obtained opal shale nanoparticles (OS NPs) through the techniques of ultrasonic emulsion and differential centrifugation. The OS NPs exhibited markedly lower cytotoxicity than crystalline mesoporous silica nanoparticles. The highly porous structure and the strong adsorbability endowed OS NPs with the ability of loading and sustained release of doxorubicin (DOX). DOX-loaded OS NPs improved tumor cellular uptake and antiproliferation compared with free drug. Interestingly, OS NPs possessed strong binding with the nuclear envelope, which can be beneficial to the nucleus localization and apoptosis inducing of loaded DOX. We further demonstrated the tumor passive targeting ability, prolonged blood circulation, and enhanced antitumor effect with limited in vivo toxicity. Our results suggest that OS NPs can be applied for tumor targeting drug delivery, which may have a significant influence on the development of silica-based drug delivery system.

MIL-100(Al) Gels as an Excellent Platform Loaded with Doxorubicin Hydrochloride for pH-Triggered Drug Release and Anticancer Effect

Slow and controlled release systems for drugs have attracted increasing interest recently. A highly efficient metal-organic gel (MOGs) drug delivery carrier, i.e., MIL-100(Al) gel, has been fabricated by a facile, low cost, and environmentally friendly one-pot process. The unique structure of MIL-100(Al) gels has led to a high loading efficiency (620 mg/g) towards doxorubicin hydrochloride (DOX) as a kind of anticancer drug. DOX-loaded MOGs exhibited high stability under physiological conditions and sustained release capacity of DOX for up to three days (under acidic environments). They further showed sustained drug release behavior and excellent antitumor effects in in vitro experiments on HeLa cells, in contrast with the extremely low biotoxicity of MOGs. Our work provides a promising way for anticancer therapy by utilizing this MOGs-based drug delivery system as an efficient and safe vehicle.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

From proof-of-concept material to PEGylated and modularly targeted ultrasound-responsive mesoporous silica nanoparticles

In this work we present the synthesis, characterization and in vitro biological evaluation of PEGylated and actively-targeted ultrasound-responsive hybrid mesoporous silica nanoparticles. This work covers the development of the chemical strategies necessary to afford a modular nanocarrier starting from a proof-of-concept material presented in previous work. This functional ultrasound-responsive material can be adapted to different specific pathological conditions by carefully choosing the appropriate targeting moieties. The new ultrasound responsive material is able to target HeLa cells when conjugated with biotin or an RGD peptide. Ultrasound-responsive cytotoxicity towards cancer cells of doxorubicin-loaded nanoparticles is demonstrated in an in vitro cytotoxicity assay.

AIEgen-Functionalized Mesoporous Silica Gated by Cyclodextrin-Modified CuS for Cell Imaging and Chemo-Photothermal Cancer Therapy

A novel multifunctional drug delivery system has been constructed by assembling per-6-thio-β-cyclodextrin-modified ultrasmall CuS nanoparticles (CD-CuS) onto fluorescent AIEgen-containing mesoporous silica nanoparticles (FMSN). The CD-CuS nanoparticles are anchored on the surface of benzimidazole-grafted FMSN, acting as a gatekeeper and photothermal agent. The prepared blue-emitting nanocomposite (FMSN@CuS) exhibits good biocompatibility and cell imaging capability. Anticancer drug doxorubicin hydrochloride (DOX) molecules are loaded into FMSN@CuS, and zero prerelease at physiological pH (7.4) and on-demand drug release at an acidic environment can be achieved due to the pH-responsive gate-opening of CD-CuS only at an acidic condition. The FMSN@CuS nanocomposite can generate obvious thermal effect after the exposure of 808 nm laser, which can also accelerate the DOX release. Meanwhile, the fluorescence intensity of DOX-loaded FMSN@CuS increases with the release of DOX, and the intracellular drug release process can be tracked according to the change of luminescence intensity. More importantly, DOX-loaded FMSN@CuS displays efficient anticancer effects in vitro upon 808 nm laser irradiation, demonstrating a good synergistic therapeutic effect via combining enhanced chemotherapy and photothermal therapy.

Bioresponsive and near infrared photon co-enhanced cancer theranostic based on upconversion nanocapsules

Developing nanotheranostics responsive to tumor microenvironments has attracted tremendous attention for on-demand cancer diagnosis and treatment. Herein, a facile Mn-doping strategy was adopted to transform mesoporous silica coated upconversion nanoparticles (UCNPs) to yolk-like upconversion nanostructures which possess a tumor-responsive biodegradation nature. The huge internal space of the innovated nanocarriers is suitable for doxorubicin (DOX) storage, besides, the Mn-doped shell is sensitive to the intratumoral acidity and reducibility, which enables shell biodegradation and further accelerates the breakage of Si-O-Si bonds within the silica framework. This tumor-responsive shell degradation is beneficial for realizing tumor-specific DOX release. Subsequently, polyoxometalate (POM) nanoclusters that can enhance photothermal conversion in response to the tumor reducibility and acidity were modified on the surface of the silica shell, thereby achieving NIR-enhanced shell degradation and also preventing premature DOX leakage. The as-produced thermal effect of the POM couples with the chemotherapy effect of the released DOX to perform a synergetic chemo-photothermal therapy. Additionally, the shell degradation brings size shrinkage to the nanocarriers, allowing faster nanoparticle diffusion and deeper tumor penetration, which is significant for improving theranostic outcomes. Also, the drastic decline of the red/green (R/G) ratio caused by the DOX release can be used to monitor the DOX release content through a fluorescence resonance energy transfer (FRET) method. The MRI effect caused by Mn release together with the MRI/CT/UCL imaging derived from Gd3+/Yb3+/Nd3+/Er3+ co-doped UCNPs under 808 nm laser excitation endow the nanosystem with multiple imaging capability, thus realizing imaging-guided cancer therapy.

Metal-Phenolic Encapsulated Mesoporous Silica Nanoparticles for pH-Responsive Drug Delivery and Magnetic Resonance Imaging

The anticancer drug doxorubicin (DOX) is locked in the mesoporous silica nanoparticle by coating FeIII-TA polymer, and its burst release can be achieved under acidic environment, along with the decreased longitudinal relaxivity. This nanoplatform shows great potential to monitoring the drug delivery process and the fate of the nanocarrier.

Se@SiO2-FA-CuS nanocomposites for targeted delivery of DOX and nano selenium in synergistic combination of chemo-photothermal therapy

In this study, a versatile tumor-targeted and multi-stimuli-responsive drug delivery vehicle (Se particle@porous silica-folic acid-copper sulfide/doxorubicin (Se@SiO₂-FA-CuS/DOX)) was fabricated for combined photothermal therapy with chemotherapy in cancer treatment. Due to excellent targeting ability, the Se@SiO₂-FA-CuS/DOX nanocomposites actively accumulated in tumor tissues and thus provided photothermal therapy under NIR irradiation and chemotherapy through the release of DOX and Se. Owing to the synergistic effect of chemotherapy (Se and DOX) and photothermal therapy, the Se@SiO₂-FA-CuS/DOX nanocomposites could efficiently inhibit cancer cells both in vitro and in vivo and even completely eliminate tumors. Moreover, as the toxicity of DOX could be reduced by Se, the treatment using Se@SiO₂-FA-CuS/DOX nanocomposites exhibited no appreciable adverse reactions. Thus, the Se@SiO₂-FA-CuS/DOX nanocomposites have great potential as a multifunctional nanoplatform in future clinical applications.

pH sensitive chitosan-mesoporous silica nanoparticles for targeted delivery of a ruthenium complex with enhanced anticancer effects

Nanocarriers are widely used for delivering drugs to tumors and their development is progressing steadily. In this study, a pH sensitive mesoporous silica nanocarrier, RuNHC@MSNs-CTS-Biotin (CTS = chitosan), is developed for the targeted delivery and controlled release of a ruthenium(ii) N-heterocyclic carbene (RuNHC) complex. The RuNHC@MSNs-CTS-Biotin nanoparticles were composed of RuNHC loaded mesoporous silica nanoparticles (MSNs) coated with chitosan-biotin (CTS-Biotin) conjugates. CTS traps the RuNHC complex inside the mesopores and biotin is used as a targeting ligand to improve specific cell uptake. The particle size of RuNHC@MSNs-CTS-Biotin was around 90 nm with a zeta potential of 12.0 mV and the RuNHC loading capacity was 26.31%. The release of RuNHC from RuNHC@MSNs-CTS-Biotin was in a pH-dependent manner, and it exhibited a 59.71% terminal release ratio at pH 5.0, but almost no release under neutral conditions (pH 7.4). Its in vitro cellular uptake and anticancer activity revealed that RuNHC@MSNs-CTS-Biotin could be selectively internalized in cancer cells by biotin receptor-mediated endocytosis and this resulted in a significant improvement in anticancer activities as compared with the RuNHC complex. This multifunctional nanocarrier system provides a promising platform for the development of precisely controllable cancer therapy.

Near-infrared light-triggered drug release from UV-responsive diblock copolymer-coated upconversion nanoparticles with high monodispersity

The preparation of a new near-infrared (NIR) light-responsive nanocarrier for controlled drug release is demonstrated.

Intrabilayer 64Cu Labeling of Photoactivatable, Doxorubicin-Loaded Stealth Liposomes

Doxorubicin (Dox)-loaded stealth liposomes (similar to those in clinical use) can incorporate small amounts of porphyrin-phospholipid (PoP) to enable chemophototherapy (CPT). PoP is also an intrinsic and intrabilayer ⁶⁴Cu chelator, although how radiolabeling impacts drug delivery has not yet been assessed. Here, we show that ⁶⁴Cu can radiolabel the stable bilayer of preformed Dox-loaded PoP liposomes with inclusion of 1% ethanol without inducing drug leakage. Dox-PoP liposomes labeled with intrabilayer copper behaved nearly identically to unlabeled ones in vitro and in vivo with respect to physical parameters, pharmacokinetics, and CPT efficacy. Positron emission tomography and near-infrared fluorescence imaging visualized orthotopic mammary tumors in mice with passive liposome accumulation following administration. A single CPT treatment with 665 nm light (200 J/cm²) strongly inhibited primary tumor growth. Liposomes accumulated in lung metastases, based on NIR imaging. These results establish the feasibility of CPT interventions guided by intrinsic multimodal imaging of Dox-loaded stealth PoP liposomes.

pH-Responsive Nanoscale Coordination Polymer for Efficient Drug Delivery and Real-Time Release Monitoring

Both excess dosages of drug and unwanted drug carrier can lead to severe side effects as well as the failure of tumor therapy. Here, an Fe³⁺ -gallic acid based drug delivery system is designed for efficient monitoring of drug release in tumor. Fe³⁺ and polyphenol gallic acid can form polygonal nanoscale coordination polymer in aqueous solution, which exhibits certain antitumor effect. Importantly, this coordination polymer possesses extremely high doxorubicin (DOX) loading efficacy (up to 48.3%). In vitro studies demonstrate that the fluorescence of DOX can be quenched efficiently when DOX is loaded on the coordination polymer. The acidity in lysosome also triggers the release of DOX and fluorescence recovery simultaneously, which realizes real-time monitoring of drug release in tumor cells. In vivo studies further indicate that this polyphenol-rich drug delivery system can significantly inhibit tumor growth with negligible heart toxicity of DOX. This system with minimal side effects should be a promising nanoplatform for tumor treatment.

Thermo-responsive magnetic Fe3O4@P(MEO2MAX-OEGMA100-X) NPs and their applications as drug delivery systems

The unique physical properties of the superparamagnetic nanoparticles (SPIONs) have made them candidates of choice in nanomedicine especially for diagnostic imaging, therapeutic applications and drug delivery based systems. In this study, superparamagnetic Fe₃O₄ NPs were synthesized and functionalized with a biocompatible thermoresponsive copolymer to obtain temperature responsive core/shell NPs. The ultimate goal of this work is to build a drug delivery system able to release anticancer drugs in the physiological temperatures range. The core/shell NPs were first synthesized and their chemical, physical, magnetic and thermo-responsive properties where fully characterized in a second step. The lower critical solution temperature (LCST) of the core/shell NPs was tuned in physiological media in order to release the cancer drug at a controlled temperature slightly above the body temperature to avoid any premature release of the drug. The core/shell NPs exhibiting the targeted LCST were then loaded with Doxurubicin (DOX) and the drug release properties were then studied with the temperature. Moreover the cytotoxicity tests have shown that the core/shell NPs had a very limited cytotoxicity up to concentration of 25μg/mL. This investigation showed that the significant release occurred at the targeted temperature in the physiological media making those nano-systems very promising for further use in drug delivery platform.

Temperature responsive fluorescent polymer nanoparticles (TRFNPs) for cellular imaging and controlled releasing of drug to living cells

Recent studies have demonstrated that drug delivery by using functional nanomaterials with imaging capability could afford plenty of insightful information for the better control of the delivery process. In this work, we developed temperature responsive fluorescent nanoparticles (TRFNPs) for drug delivery and cellular imaging. The TRFNP was fabricated by one-pot co-precipitation of thermal sensitive amphiphilic block copolymers polystyrene-b-poly(N-isopropyl acrylamide) (PS-b-PNIPAM) and fluorescent conjugated polymer poly [(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo(2,1',3)-thiadiazole)] (PFBT) in the presence of desired small guest molecules. The dynamic light scattering (DLS) measurements verified that this functional nanoparticle exhibited temperature dependent size variation, which could therefore regulate the releasing rate of loaded guest molecules (e.g. drugs) inside the polymer core. Besides, the TRFNPs displayed good photostability in terms of optical characterization. The cellular cytotoxicity characterization demonstrated that this nanoparticle exhibited good biocompatibility even under the mass concentration of 10μg/mL. By using Nile Red as a model molecule, the temperature-controlled releasing process from TRFNPs in solution as well as inside living cells was monitored directly according to the spectroscopic and microscopic characterizations. Furthermore, anti-cancer drug was successfully delivered into living cells via TRFNPs and released in a temperature dependent manner. As a consequence, owing the attractive merits as mentioned above, this nanostructure would find broad applications in nanomedicine in the future.

A Core-Shell-Satellite Structured Fe3 O4 @g-C3 N4 -UCNPs-PEG for T1 /T2 -Weighted Dual-Modal MRI-Guided Photodynamic Therapy

Reactive oxygen species (ROS) produced in the specific tumor site plays the key role in photodynamic therapy (PDT). Herein, a multifunctional nanoplatform is designed by absorbing ultrasmall upconversion nanoparticles (UCNPs) on mesoporous graphitic-phase carbon nitride (g-C₃ N₄ ) coated superparamagnetic iron oxide nanospheres, then further modified with polyethylene glycol (PEG)molecules (abbreviated as Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG). The inert g-C₃ N₄ layer between Fe₃ O₄ core and outer UCNPs can substantially depress the quenching effect of Fe₃ O₄ on the upconversion emission. Upon near-infrared (NIR) laser irradiation, the UCNPs convert the energy to the photosensitizer (g-C₃ N₄ layer) through fluorescence resonance energy transfer process, thus producing a vast amount of ROS. In vitro experiment exhibits an obvious NIR-triggered cell inhibition due to the cellular uptake of nanoparticles and the effective PDT efficacy. Notably, this platform is responsive to magnetic field, which enables targeted delivery under the guidance of an external magnetic field and supervises the therapeutic effect by T₁ /T₂ -weighted dual-modal magnetic resonance imaging. Moreover, in vivo therapeutic effect reveals that the magnetism guided accumulation of Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG can almost trigger a complete tumor inhibition without any perceived side effects. The experiments emphasize that the excellent prospect of Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG as a magnetic targeted platform for PDT application.

Electrostatic wrapping of doxorubicin with curdlan to construct an efficient pH-responsive drug delivery system

The development of environmentally responsive drug delivery systems for the treatment of cancer has attracted particular interest in recent years. However, the enhancement of drug loading capacity and realization of pH-responsive drug delivery remain challenging. Herein, we employ carboxymethyl curdlan as a hydrophilic carrier to wrap doxorubicin (DOX) directly via electrostatic interaction. The sizes of the formed nanoparticles can be simply tuned by changing their feeding ratios. In particular, the nanoparticles are highly stable in aqueous solution without size variation. In vitro drug release and cytotoxicity assays illustrate that this delivery system can release DOX differentially under various environmental conditions and transport it into cell nuclei efficiently, with comparable therapeutic effect to the free drug. These results suggest that the carrying of antitumor drugs by polysaccharide via electrostatic interaction is a simple but effective way to construct a pH-dependent drug delivery platform.