Nanoceria-triggered synergetic drug release based on CeO(2) -capped mesoporous silica host-guest interactions and switchable enzymatic activity and cellular effects of CeO(2)

Synergistic and targeted drug delivery based on nano-CeO2 capped with galactose functionalized pillar[5]arene via host-guest interactions

A smart drug delivery system based on porous CeO₂ nano-rods (CeONRs) capped with galactose functionalized pillar[5]arene via host-guest interactions has been constructed, which showed GSH-responsiveness, synergism with anticancer drugs and cancer targeting ability resulting from its disulphide unit, ceria properties and galactose units, respectively.

Cerium oxide nanoparticles: green synthesis and biological applications

CeO2 nanoparticles (NPs) have shown promising approaches as therapeutic agents in biology and medical sciences. The physicochemical properties of CeO2-NPs, such as size, agglomeration status in liquid, and surface charge, play important roles in the ultimate interactions of the NP with target cells. Recently, CeO2-NPs have been synthesized through several bio-directed methods applying natural and organic matrices as stabilizing agents in order to prepare biocompatible CeO2-NPs, thereby solving the challenges regarding safety, and providing the appropriate situation for their effective use in biomedicine. This review discusses the different green strategies for CeO2-NPs synthesis, their advantages and challenges that are to be overcome. In addition, this review focuses on recent progress in the potential application of CeO2-NPs in biological and medical fields. Exploiting biocompatible CeO2-NPs may improve outcomes profoundly with the promise of effective neurodegenerative therapy and multiple applications in nanobiotechnology.

Nanoceria-Mediated Drug Delivery for Targeted Photodynamic Therapy on Drug-Resistant Breast Cancer

Photodynamic therapy (PDT) has shown great potential for overcoming drug-resistant cancers. Here, we report a multifunctional drug delivery system based on chlorin e6 (Ce6)/folic acid (FA)-loaded branched polyethylenimine-PEGylation ceria nanoparticles (PPCNPs-Ce6/FA), which was developed for targeted PDT to overcome drug-resistant breast cancers. Nanocarrier delivery and FA targeting significantly promoted the cellular uptake of photosensitizers (PSs), followed by their accumulation in lysosomes. PPCNPs-Ce6/FA generated reactive oxygen species (ROS) after near-infrared irradiation (NIR, 660 nm), leading to reduced P-glycoprotein (P-gp) expression, lysosomal membrane permeabilization (LMP), and excellent phototoxicity toward resistant MCF-7/ADR cells, even at ultralow doses. Moreover, we identified NIR-triggered lysosomal-PDT using the higher dose of PPCNPs-Ce6/FA, which stimulated cell death by plasma membrane blebbing, cell swelling, and energy depletion, indicating an oncosis-like cell death pathway, despite the occurrence of apoptotic or autophagic mechanisms at lower drug doses. In vivo studies showed prolonged blood circulation times, low toxicity in mice, and high tumor accumulation of PPCNPs-Ce6/FA. In addition, using NIR-triggered PDT, PPCNPs-Ce6/FA displayed excellent potency for tumor regression in the MCF-7/ADR xenograft murine model. This study suggested that multifunctional PPCNPs-Ce6/FA nanocomposites are a versatile and effective drug delivery system that may potentially be exploited for phototherapy to overcome drug-resistant cancers, and the mechanisms of cell death induced by PDT should be considered in the design of clinical protocols.

Tailoring Enzyme-Like Activities of Gold Nanoclusters by Polymeric Tertiary Amines for Protecting Neurons Against Oxidative Stress

The cytotoxicity of nanozymes has drawn much attention recently because their peroxidase-like activity can decompose hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) under acidic conditions. Although catalytic activities of nanozymes are highly associated with their surface properties, little is known about the mechanism underlying the surface coating-mediated enzyme-like activities. Herein, it is reported for the first time that amine-terminated PAMAM dendrimer-entrapped gold nanoclusters (AuNCs-NH2 ) unexpectedly lose their peroxidase-like activity while still retaining their catalase-like activity in physiological conditions. Surprisingly, the methylated form of AuNCs-NH2 (i.e., MAuNCs-N(+) R3 , where R = H or CH3 ) results in a dramatic recovery of the intrinsic peroxidase-like activity while blocking most primary and tertiary amines (1°- and 3°-amines) of dendrimers to form quaternary ammonium ions (4°-amines). However, the hidden peroxidase-like activity is also found in hydroxyl-terminated dendrimer-encapsulated AuNCs (AuNCs-OH, inside backbone with 3°-amines), indicating that 3°-amines are dominant in mediating the peroxidase-like activity. The possible mechanism is further confirmed that the enrichment of polymeric 3°-amines on the surface of dendrimer-encapsulated AuNCs provides sufficient suppression of the critical mediator •OH for the peroxidase-like activity. Finally, it is demonstrated that AuNCs-NH2 with diminished cytotoxicity have great potential for use in primary neuronal protection against oxidative damage.

Self-assembled porous ceria nanostructures with excellent water solubility and antioxidant properties

Porous nanoceria with excellent water-solubility and antioxidation are successfully synthesized by one-pot hydrothermal approach.

Smart Mesoporous Nanomaterials for Antitumor Therapy

The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is reached. It is possible to incorporate different targeting ligands to the outermost surface of MSNs to selectively drive the drugs to the tumour tissues. To prevent the premature release of the cargo entrapped in the mesopores, it is feasible to cap the pore entrances using stimuli-responsive nanogates. Therefore, upon exposure to internal (pH, enzymes, glutathione, etc.) or external (temperature, light, magnetic field, etc.) stimuli, the pore opening takes place and the release of the entrapped cargo occurs. These smart MSNs are capable of selectively reaching and accumulating at the target tissue and releasing the entrapped drug in a specific and controlled fashion, constituting a promising alternative to conventional chemotherapy, which is typically associated with undesired side effects. In this review, we overview the recent advances reported by the scientific community in developing MSNs for antitumor therapy. We highlight the possibility to design multifunctional nanosystems using different therapeutic approaches aimed at increasing the efficacy of the antitumor treatment.

PEGylated ceria nanoparticles used for radioprotection on human liver cells under γ-ray irradiation

Ceria nanoparticles (CNPs) have recently been shown to protect cells and animals from radiation-induced damage. However, most of the CNPs used in previous studies were either naked or weakly protected by surfactants, which inevitably encounter many obstacles in biological applications. Here, alendronate was used as an ideal anchor to graft polyethylene glycol (PEG) onto CNPs, leading to enhanced stability, reduced cytotoxicity, and improved biological properties. Further investigation assessed the protective ability of the nanoparticles against radiation-induced effects for human normal liver cells (L-02), indicating that the PEGylated CNPs (CNPs-AL-PEG) were more efficient than naked CNPs. We determined that enhanced Ce(3+)/Ce(4+) ratios improved intracellular dispersion and that the ameliorated intracellular distribution of CNPs-AL-PEG contributes to the elevated expression of SOD2, which leads to increased protection of normal cells against ROS and reduces the oxidatively generated DNA damage. These studies hold tremendous promise for radioprotection and biological applications.

Near-Infrared Light Manipulated Chemoselective Reductions Enabled by an Upconversional Supersandwich Nanostructure

Core-satellite is one of the most powerful superstructures since it leads to enhanced or completely new properties through compatible combination of each component. Here we create a novel ceria-based core-shell-satellite supersandwich structure with near-infrared (NIR) light manipulated catalytic activity by integrating the upconversion luminescent and catalytic functionality of CeO2 nanoparticles. Specifically, lanthanide-doped octahedral CeO2 nanoparticles (o-CeO2) are coated with silica layer (o-CeO2@SiO2) to enhance their luminescence intensity. The pH-dependent catalytic active cubic CeO2 nanoparticles (c-CeO2) are then assembled on the surface of o-CeO2@SiO2 to form the supersandwich structure (o-CeO2@SiO2@c-CeO2) following a classic chemical reaction. The upconversion quantum yield of o-CeO2 in this nanostructure can be nearly doubled. Furthermore, under NIR light irradiation, the o-CeO2@SiO2@c-CeO2 supersandwich structure based composite catalyst displays superior catalytic activity in selective reduction of aromatic nitro compounds to corresponding azo compounds, and the composite photocatalyst can be easily recycled for several times without significant loss of catalytic activity. This strategy may serve as a universal method for the construction of multifunctional nanostructures and shed light on the green chemistry for chemical synthesis.

Mesoporous-Silica-Functionalized Nanoparticles for Drug Delivery

The ever-growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.

Enzyme responsive drug delivery system based on mesoporous silica nanoparticles for tumor therapy in vivo

To reduce the toxic side effects of traditional chemotherapeutics in vivo, we designed and constructed a biocompatible, matrix metalloproteinases (MMPs) responsive drug delivery system based on mesoporous silica nanoparticles (MSNs). MMPs substrate peptide containing PLGLAR (sensitive to MMPs) was immobilized onto the surfaces of amino-functionalized MSNs via an amidation reaction, serving as MMPs sensitive intermediate linker. Bovine serum albumin was then covalently coupled to linker as end-cap for sealing the mesopores of MSNs. Lactobionic acid was further conjugated to the system as targeting motif. Doxorubicin hydrochloride was used as the model anticancer drug in this study. A series of characterizations revealed that the system was successfully constructed. The peptide-functionalized MSNs system demonstrated relatively high sensitivity to MMPs for triggering drug delivery, which was potentially important for tumor therapy since the tumor's microenvironment overexpressed MMPs in nature. The in vivo experiments proved that the system could efficiently inhibit the tumor growth with minimal side effects. This study provides an approach for the development of the next generation of nanotherapeutics toward efficient cancer treatment.

Synthesis of a mixed valence state Ce-MOF as an oxidase mimetic for the colorimetric detection of biothiols

We demonstrate a facile and rapid in situ partial oxidation synthetic strategy for the fabrication of a mixed valence state Ce-MOF (MVCM) which exhibits intrinsic oxidase-like activity. Furthermore, on the basis of the excellent catalytic activity of the MCVM, a colorimetric approach for the high-throughput detection of biothiols in serum samples was established.

Enzyme responsive mesoporous silica nanoparticles for targeted tumor therapy in vitro and in vivo

This study reports a biocompatible controlled drug release system based on mesoporous silica nanoparticles (MSNs) for tumor microenvironment responsive drug delivery. It was fabricated by grafting phenylboronic acid conjugated human serum albumin (PBA-HSA) onto the surfaces of MSNs as a sealing agent, via an intermediate linker of a functional polypeptide, which was composed of two functional units: the polycation cell penetrating peptide (CPP) polyarginine, and matrix metalloproteinase 2 (MMP-2) substrate peptide. A series of characterizations confirmed that the system had been successfully constructed. In vitro tests proved that the anticancer drug loading system could efficiently induce cell apoptosis in vitro. More importantly, the in vivo tumor experiments confirmed that the anticancer loading system could efficiently inhibit tumor growth with minimal side effects.

Mesoporous silica nanoparticles grafted with a light-responsive protein shell for highly cytotoxic antitumoral therapy

A novel phototriggered drug delivery nanocarrier, which exhibits very high tumor cytotoxicity against human tumoral cells, is presented.

Advances in mesoporous silica nanoparticles for targeted stimuli-responsive drug delivery

INTRODUCTION

Mesoporous silica nanoparticles (MSNPs) are one of the most promising inorganic drug delivery systems (DDSs). The design and development of tumour-targeted MSNPs with stimuli-responsive drug release capability aim at enhancing the efficiency and minimising the side effects of anti-tumour drugs for cancer therapy.

AREAS COVERED

This review provides an overview of the scientific advances in MSNPs for tumour-targeted stimuli-responsive drug delivery. The key factors that govern the passive accumulation of MSNPs within solid tumours such as size, shape and surface functionalisation are roughly described. The different active targeting strategies for the specific retention and uptake of MSNPs by tumour cells are also outlined. The approaches developed so far for the synthesis of smart MSNPs capable of releasing the trapped drugs in response to internal or external stimuli and their applications are reviewed. Critical considerations in the use of MSNPs for the treatment of cancer treatment are discussed. The future prospects and key factors concerning the clinical application of MSNPs are considered throughout the manuscript.

EXPERT OPINION

MSNPs are promising nanocarriers to efficiently transport and site-specifically deliver highly toxic drugs, such as chemotherapeutic agents for cancer treatment. However, there are certain issues that should be overcome to improve the suitability of MSNPs for clinical applications. Increasing the penetration capability of MSNPs within tumour tissues, providing them of appropriate colloidal stability in physiological fluids and ensuring that their active targeting capability and stimuli-responsive performance are preserved in complex biological media are of foremost significance. Few in vivo evaluation tests of MSNPs have been reported and much research effort into this field is mandatory to be able to move from bench to bedside.

Cytochrome c end-capped mesoporous silica nanoparticles as redox-responsive drug delivery vehicles for liver tumor-targeted triplex therapy in vitro and in vivo

To develop carriers for efficient anti-cancer drug delivery with reduced side effects, a biocompatible and redox-responsive nanocontainer based on mesoporous silica nanoparticles (MSNs) for tumor-targeted triplex therapy was reported in this study. The nanocontainer was fabricated by immobilizing cytochrome c (CytC) onto the MSNs as sealing agent via intermediate linkers of disulfide bonds for redox-responsive intracellular drug delivery. AS1411 aptamer was further tailored onto MSNs for cell/tumor targeting. The successful construction of redox- responsive MSNs was confirmed by BET/BJH analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermogravimetric analysis (TGA), respectively. Detailed investigations demonstrated that anticancer drug of doxorubicin (DOX) loaded nanocontainer could be triggered by reductant (e.g. glutathione) within cellular microenvironment and release DOX to induce tumor cell apoptosis in vitro. More importantly, the nanocontainer displayed great potential for tumor targeting and achieved triplex therapy effects on the tumor inhibition in vivo through the loading DOX, gatekeeper of CytC and AS1411 aptamer, which were reflected by the change of tumor size, TUNEL staining and HE staining assays.

Redox-responsive nanocarrier based on heparin end-capped mesoporous silica nanoparticles for targeted tumor therapy in vitro and in vivo

This study reports a smart controlled drug release system based on mesoporous silica nanoparticles (MSNs) for targeted drug delivery. The system was fabricated by employing heparin as an end-capping agent to seal the mesopores of MSNs via disulfide bonds as intermediate linkers for intracellular glutathione triggered drug release. Lactobionic acid molecules were then coupled to heparin end-capped MSNs that serve as targeting motifs for facilitating the uptake of doxorubicin (DOX) loaded MSNs by HepG2 cells and tumors, respectively. Detailed investigations demonstrated that the fabricated drug delivery systems could deliver DOX to cancer cells to induce cell apoptosis in vitro and tumor tissue for the inhibition of tumor growth in vivo with minimal side effects. The study affords a promising nanocarrier for redox-responsive cargo delivery with high curative efficiency for cancer therapy.

Catalytically active nanomaterials: a promising candidate for artificial enzymes

Natural enzymes, exquisite biocatalysts mediating every biological process in living organisms, are able to accelerate the rate of chemical reactions up to 10(19) times for specific substrates and reactions. However, the practical application of enzymes is often hampered by their intrinsic drawbacks, such as low operational stability, sensitivity of catalytic activity to environmental conditions, and high costs in preparation and purification. Therefore, the discovery and development of artificial enzymes is highly desired. Recently, the merging of nanotechnology with biology has ignited extensive research efforts for designing functional nanomaterials that exhibit various properties intrinsic to enzymes. As a promising candidate for artificial enzymes, catalytically active nanomaterials (nanozymes) show several advantages over natural enzymes, such as controlled synthesis in low cost, tunability in catalytic activities, as well as high stability against stringent conditions. In this Account, we focus on our recent progress in exploring and constructing such nanoparticulate artificial enzymes, including graphene oxide, graphene-hemin nanocomposites, carbon nanotubes, carbon nanodots, mesoporous silica-encapsulated gold nanoparticles, gold nanoclusters, and nanoceria. According to their structural characteristics, these enzyme mimics are categorized into three classes: carbon-, metal-, and metal-oxide-based nanomaterials. We aim to highlight the important role of catalytic nanomaterials in the fields of biomimetics. First, we provide a practical introduction to the identification of these nanozymes, the source of the enzyme-like activities, and the enhancement of activities via rational design and engineering. Then we briefly describe new or enhanced applications of certain nanozymes in biomedical diagnosis, environmental monitoring, and therapeutics. For instance, we have successfully used these biomimetic catalysts as colorimetric probes for the detection of cancer cells, nucleic acids, proteins, metal ions, and other small molecules. In addition, we also introduce three exciting advances in the use of efficient modulators on artificial enzyme systems to improve the catalytic performance of existing nanozymes. For example, we report that graphene oxide could serve as a modulator to greatly improve the catalytic activity of lysozyme-stabilized gold nanoclusters at neutral pH, which will have great potential for applications in biological systems. We show that, through the incorporation of modulator into artificial enzymes, we can offer a facile but highly effective way to improve their overall catalytic performance or realize the catalytic reactions that were not possible in the past. We expect that nanozymes with unique properties and functions will attract increasing research interest and lead to new opportunities in various fields of research.