Stimulated Release of Size-Selected Cargos in Succession from Mesoporous Silica Nanoparticles

Engineering a nanolab for the determination of lysosomal nitric oxide by the rational design of a pH-activatable fluorescent probe

A pH-activatable fluorescent probe, Rhod-H-NO, was designed and synthesized for the determination of lysosomal NO in living cells and in vivo.

Nitric oxide (NO) is often involved in many different physiological processes including the regulation of lysosomal functions. However, it remains a great challenge to explore the variations of NO levels in lysosomes, limiting the understanding behind its biological functions in cellular signaling pathways and various diseases. Herein, a pH-activatable fluorescent probe, Rhod-H-NO, was designed and synthesized for the determination of lysosomal NO, in which the activation response model is beneficial towards getting accurate biological information. To ensure that Rhod-H-NO can accumulate effectively and exist stably in lysosomes without interference and degradation from other active species, Rhod-H-NO was engineered into the nanopores of mesoporous silica nanoparticles (MSNs) with β-cyclodextrin (β-CD) as the gatekeeper to obtain a nanolab. The nanolab was successfully applied to detect lysosomal NO in living cells and in vivo with high time and spatial resolution. This nanolab could serve as an excellent molecular tool to exploit and elucidate the function of NO at sub-cellular levels.

Voltage/pH-Driven Mechanized Silica Nanoparticles for the Multimodal Controlled Release of Drugs

The major challenges of current drug delivery systems for combination chemotherapy focus on how to efficiently transport drugs to target sites and release multiple drugs in a programmed manner. Herein, we report a novel multidrug delivery system, MSNPs 1, based on mechanized silica nanoparticles, which were constructed through functionalization of mesoporous silica nanoparticles with the acid-cleavable intermediate linkages and the monoferrocene functionalized β-cyclodextrin (Fc-β-CD) as supramolecular nanovalves. MSNPs 1 achieved zero premature release in the physiological pH solution and realized two different release modalities. In modality 1, MSNPs 1 released the encapsulated drugs gemcitabine (GEM) and doxorubicin (DOX) in sequence when they were successively applied to voltage and acid stimuli. The release time and dosage of GEM were precisely controlled via external voltage. The subsequent acid-triggered release of DOX was attributed to breakage of the intermediate linkages containing ketal groups. Modality 2 is the concurrent release of these two drugs directly upon acid exposure. Furthermore, the cell viability experiments demonstrated that MSNPs 1 had an improved cytotoxicity to MCF7 cells in comparison with single DOX- or GEM-loaded mechanized silica nanoparticles. We envisage that MSNPs 1 will play an important role in research and development for a new generation of controlled-release drug delivery system.

Dual stimuli-responsive multi-drug delivery system for the individually controlled release of anti-cancer drugs

A dual stimuli-responsive multi-drug delivery system was developed for "cancer cocktail therapy". Upon UV irradiation, microcapsules could rapidly release the small-molecule drugs, and thereafter the macromolecular drugs would be released in the presence of MMP in the tumor cells. This system will find great potential as a novel chemotherapeutic combination for cancer treatment.

A redox-responsive mesoporous silica nanoparticle capped with amphiphilic peptides by self-assembly for cancer targeting drug delivery

A redox-responsive mesoporous silica nanoparticle (RRMSN) was developed as a drug nanocarrier by noncovalent functionalization of MSNs with amphiphilic peptides containing the RGD ligand. The alkyl chain stearic acid (C18) with a thiol terminal group was anchored on the surface of MSNs via a disulfide bond, and the amphiphilic peptide (AP) C18-DSDSDSDSRGDS was coated by self-assembly through hydrophobic interactions between the octadecyl groups of MSNs and alkyl chains of AP, which played the role of a gatekeeper collectively. In vitro drug release profiles demonstrated that the anticancer drug (DOX) could be entrapped with nearly no leakage in the absence of dithiothreitol (DTT) or glutathione (GSH). With the addition of DTT or GSH, the entrapped drug released quickly due to the cleavage of the disulfide bond. It was found that after the internalization of MSNs by cancer cells via the receptor-mediated endocytosis, the surface amphiphilic peptides and alkyl chain of RRMSN/DOX were removed to induce rapid drug release intracellularly after the cleavage of the disulfide bond, triggered by GSH secreted in cancer cells. This novel intelligent RRMSN/DOX drug delivery system using self-assembly of amphiphilic peptides around the MSNs provides a facile, but effective strategy for the design and development of smart drug delivery for cancer therapy.

Mono-benzimidazole functionalized β-cyclodextrins as supramolecular nanovalves for pH-triggered release of p-coumaric acid

The self-complexation of mono-benzimidazole functionalized β-cyclodextrins was investigated. The unique molecular structure employed as supramolecular nanovalves were installed on the external surface of mesoporous silica to assemble mechanized silica nanoparticles, which showed pH-triggered release property.

Multifunctional polymer-capped mesoporous silica nanoparticles for pH-responsive targeted drug delivery

A highly stable modular platform, based on the sequential covalent attachment of different functionalities to the surface of core-shell mesoporous silica nanoparticles (MSNs) for targeted drug delivery is presented. A reversible pH-responsive cap system based on covalently attached poly(2-vinylpyridine) (PVP) was developed as drug release mechanism. Our platform offers (i) tuneable interactions and release kinetics with the cargo drug in the mesopores based on chemically orthogonal core-shell design, (ii) an extremely robust and reversible closure and release mechanism based on endosomal acidification of the covalently attached PVP polymer block, (iii) high colloidal stability due to a covalently coupled PEG shell, and (iv) the ability to covalently attach a wide variety of dyes, targeting ligands and other functionalities at the outer periphery of the PEG shell. The functionality of the system was demonstrated in several cell studies, showing pH-triggered release in the endosome, light-triggered endosomal escape with an on-board photosensitizer, and efficient folic acid-based cell targeting.

Combination drug release of smart cyclodextrin-gated mesoporous silica nanovehicles

An integrated γ-cyclodextrin-gated mesoporous silica delivery system via dual dynamic covalent bonds was constructed with dual drug loading for simultaneous and cascade release in targeted combination drug therapy.

Oxime ligation on the surface of mesoporous silica nanoparticles

A versatile surface-functionalization strategy applicable to mesoporous silica nanoparticles, which could potentially serve as drug delivery vehicles, is described that makes use of alkoxyamine tethers on the surface of the nanoparticles. A wide variety of carbonyl compounds can be attached readily to these tethers under the mild conditions of oxime ether formation, simply by incubating the chemically modified mesoporous silica nanoparticles with aldehydes or ketones in water.

Dendrimerlike mesoporous silica nanoparticles as pH-responsive nanocontainers for targeted drug delivery and bioimaging

In this work, we employed dendrimerlike mesoporous silica nanoparticles with hierarchical pores (HPSNs) to fabricate drug delivery system bioimaging and targeted tumor therapy in vivo. N,N-phenylenebis(salicylideneimine)dicarboxylic acid (Salphdc) was used both as the gatekeeper of HPSNs via pH-responsive coordination bonds between -COOH of Salphdc and In(3+) ions and as a fluorescence imaging agent. Folic acid was then conjugated to Salphdc as the targeting unit. The results revealed that the system could deliver model drug DOX to the tumor site with high efficiency and then cause cell apoptosis and tumor growth inhibition. Moreover, the conjugated Salphdc was proved to be a promising fluorescence probe for tracing distribution of the system in vivo. The study affords a potential nanoconainer for cancer therapy and biological imaging.

Bioinspired nanovalves with selective permeability and pH sensitivity

Biological systems with controlled permeability and release functionality, which are among the successful examples of living beings to survive in evolution, have attracted intensive investigation and have been mimicked due to their broad spectrum of applications. We present in this work, for the first time, an example of nuclear pore complexes (NPCs)-inspired controlled release system that exhibits on-demand release of angstrom-sized molecules. We do so in a cost-effective way by stabilizing porous cobalt basic carbonates as nanovalves and realizing pH-sensitive release of entrapped subnano cargo. The proof-of-concept work also consists of the establishment of two mathematical models to explain the selective permeability of the nanovalves. Finally, gram-sized (or larger) quantities of the bio-inspired controlled release system can be synthesized through a scaling-up strategy, which opens up opportunities for controlled release of functional molecules in wider practical applications.

Light-responsive peptide [2]rotaxanes as gatekeepers of mechanised nanocontainers

Novel mechanized silica nanoparticles incorporating a peptide-based molecular shuttle as a photo-responsive interlocked gatekeeper of nanocontainers are described including the uptake and delivery studies of a model cargo.

Sugar and pH dual-responsive snap-top nanocarriers based on mesoporous silica-coated Fe3O4 magnetic nanoparticles for cargo delivery

Sugar and pH operated snap-top nanocarriers, consisting of a superparamagnetic Fe₃O₄ core and a mesoporous silica shell and surface-functionalized covalently with β-CDs, were constructed.

Molecular and supramolecular switches on mesoporous silica nanoparticles

This review summarizes the recent advances of molecular and supramolecular switches installed on mesoporous silica nanoparticles.

The dual-stimulated release of size-selected cargos from cyclodextrin-covered mesoporous silica nanoparticles

A drug delivery system of dual-stimulated release of size-selected cargos from β-cyclodextrin-covered mesoporous silica nanoparticles was prepared.

From self-sorted coordination libraries to networking nanoswitches for catalysis

This feature article sketches our long way from the development of dynamic heteroleptic coordination motifs to the self-sorting of multi-component libraries and finally the design of a new family of triangular nanomechanical switches, which are useful for ON–OFF control of catalysis and in bidirectional communication.

Redox-responsive degradable honeycomb manganese oxide nanostructures as effective nanocarriers for intracellular glutathione-triggered drug release

Redox-responsive degradable honeycomb manganese oxide (hMnO₂) nanostructures consisting of some lamellar MnO₂ platelets were established as a new class of drug carriers for efficient intracellular GSH-triggered drug release.

Towards the Development of Smart 3D "gated scaffolds" for on-command delivery

A new approach towards the design of "gated scaffolds" based on the combination of capped mesoporous silica nanoparticles (MSNs) with porous biomaterials is reported. Using this approach, a 3D gelatin-based scaffold able to selectively deliver cargo in the presence of an APase enzyme is prepared and tested. This new design opens up the possibility of developing new smart biomaterials with advanced drug-delivery features.

Integration of nanoassembly functions for an effective delivery cascade for cancer drugs

A "cluster-bomb"-like lipid-dendrimer nanoassembly synergizes the functions of its components and thereby efficiently accomplishes the drug delivery cascade for high efficacy in treating cancer. The nanoassembly successfully circulates in the blood and accumulates in the tumor. Once in the tumor, it releases small dendrimers that act like "bomblets", enabling tumor penetration, cell internalization, and drug release.

Pillar[6]arene-valved mesoporous silica nanovehicles for multiresponsive controlled release

The synthesis and host-guest chemistry of pillararene (PA) derivatives are a hot research topic, and the applications of PAs in relevant research fields are essential to explore. Carboxylate-substituted pillar[6]arene (CPA[6])-valved mesoporous silica nanoparticles (MSNs) functionalized with dimethylbenzimidazolium (DMBI) and bipyridinium (BP) stalks were constructed, respectively, for multiresponsive controlled release. CPA[6] encircled the DMBI or BP stalks to develop supramolecular nanovalves for encapsulation of cargo within the MSN pores. The release of cargo was triggered by acidic pH or competitive binding for the dethreading of CPA[6] and the opening of the nanovalves; moreover, coordination chemistry is the first strategy to activate CPA nanovalves by metal chelating with the carboxylate groups of CPA for cargo release. The controlled release of the CPA[6]-valved MSN delivery systems can meet diverse requirements and has promising biological applications in targeted drug therapy.

Mesoporous Silica Nanoparticles Coated by Layer-by-Layer Self-assembly Using Cucurbit[7]uril for in Vitro and in Vivo Anticancer Drug Release

Mesoporous silica nanoparticles (MSNs) are promising solid supports for controlled anticancer drug delivery. Herein, we report biocompatible layer-by-layer (LbL) coated MSNs (LbL-MSNs) that are designed and crafted to release encapsulated anticancer drugs, e.g., doxorubicin hydrochloride (DOX), by changing the pH or by adding competitive agents. The LbL coating process comprises bis-aminated poly(glycerol methacrylate)s (BA-PGOHMAs) and cucurbit[7]uril (CB[7]), where CB[7] serves as a molecular bridge holding two different bis-aminated polymeric layers together by means of host-guest interactions. This integrated nanosystem is tuned to respond under specific acidic conditions or by adding adamantaneamine hydrochloride (AH), attributed to the competitive binding of hydronium ions or AH to CB[7] with BA-PGOHMAs. These LbL-MSN hybrids possess excellent biostability, negligible premature drug leakage at pH 7.4, and exceptional stimuli-responsive drug release performance. The pore sizes of the MSNs and bis-aminated compounds (different carbon numbers) of BA-PGOHMAs have been optimized to provide effective integrated nanosystems for the loading and release of DOX. Significantly, the operating pH for the controlled release of DOX matches the acidifying endosomal compartments of HeLa cancer cells, suggesting that these hybrid nanosystems are good candidates for autonomous anticancer drug nanocarriers actuated by intracellular pH changes without any invasive external stimuli. The successful cellular uptake and release of cargo, e.g., propidium iodide (PI), in human breast cancer cell line MDA-231 from PI-loaded LbL-MSNs have been confirmed by confocal laser scanning microscopy (CLSM), while the cytotoxicities of DOX-loaded LbL-MSNs have been quantified by the Cell Counting Kit-8 (CCK-8) viability assay against HeLa cell lines and fibroblast L929 cell lines. The uptake of DOX-loaded LbL-MSNs by macrophages can be efficiently reduced by adding biocompatible hydrophilic poly(ethylene glycol) or CB[7] without destroying the capping. In vivo tumor-growth inhibition experiments with BALB/c nude mice demonstrated a highly efficient tumor-growth inhibition rate of DOX-loaded LbL-MSNs, suggesting that the novel type of LbL-MSN materials hold great potentials in anticancer drug delivery.

Nanoparticles with Precise Ratiometric Co-Loading and Co-Delivery of Gemcitabine Monophosphate and Cisplatin for Treatment of Bladder Cancer

Combination chemotherapy is a common practice in clinical management of malignancy. Synergistic therapeutic outcome is only achieved when tumor cells are exposed to cells in an optimal ratio. However, due to diverse physicochemical properties of drugs, no free drug cocktails or nanomaterials are capable of co-loading and co-delivering drugs at an optimal ratio. Herein, we develop a novel nano-platform with precise ratiometric co-loading and co-delivery of two hydrophilic drugs for synergistic anti-tumor effects. Based on previous work, we utilize a solvent displacement method to ratiometrically load dioleoyl phosphatidic acid (DOPA)-gemcitabine monophosphate and DOPA coated cisplatin-precipitate nanocores into the same PLGA NP. These cores are designed to have similar hydrophobic surface properties. GMP and cisplatin are engineered into PLGA NP at an optimal synergistic ratio (5:1, mol:mol) with over 70% encapsulation efficiency and were ratiometrically taken up by tumor cells in vitro and in vivo. These PLGA NP exhibit synergistic anti-cancer effects in a stroma-rich bladder tumor model. A single injection of dual drugs in PLGA NP can significantly inhibit tumor growth. This nanomaterial-system solves problems related to ratiometric co-loading and co-delivery of different hydrophilic moieties and provides possibilities for co-loading hydrophilic drugs with hydrophobic drugs for combination therapy.

Synergetic gating of metal-latching ligands and metal-chelating proteins for mesoporous silica nanovehicles to enhance delivery efficiency

Stimuli-responsive drug delivery systems are highly desirable for improved therapeutic efficacy and minimized adverse effects of drugs. Mesoporous silica nanoparticles (MSNs) functionalized with pentadentate ligands, N-(3-trimethoxysilylpropyl)ethylenediamine triacetate (TSP-DATA), in the presence of metal ions with and without myoglobin (Mb)-containing surface-accessible histidine residues, were constructed for pH-triggered controlled release. The DATA ligands immobilized on the MSN pore outlets could encapsulate cargo within the pores by metal latching across pore openings, and release efficiency increased with the increase of surface density of the DATA ligands. The release efficiencies for the metal-chelating protein nanogates, through multiple-site binding of Mb with the metal-chelating ligands, were higher than those for the metal-latching ligand nanogates but were almost independent of surface density of the ligands investigated. Both the metal-latching ligands and the metal-chelating proteins played a synergetic role in gating MSNs for high-loading drug delivery and stimuli-responsive controlled release. The constructed Mb-Cu(2+)-gated MSN delivery system has promising applications in targeted drug therapy of tumors.

Towards chemical communication between gated nanoparticles

The design of comparatively simple and modularly configurable artificial systems able to communicate through the exchange of chemical messengers is, to the best of our knowledge, an unexplored field. As a proof-of-concept, we present here a family of nanoparticles that have been designed to communicate with one another in a hierarchical manner. The concept involves the use of capped mesoporous silica supports in which the messenger delivered by a first type of gated nanoparticle is used to open a second type of nanoparticle, which delivers another messenger that opens a third group of gated nanoobjects. We believe that the conceptual idea that nanodevices can be designed to communicate with one another may result in novel applications and will boost further advances towards cooperative systems with complex behavior as a result of the communication between simple abiotic individual components.

Integrated graphene/nanoparticle hybrids for biological and electronic applications

The development of novel graphene/nanoparticle hybrid materials is currently the subject of tremendous research interest. The intrinsic exceptional assets of both graphene (including graphene oxide and reduced graphene oxide) and nanoparticles render their hybrid materials synergic properties that can be useful in various applications. In this feature review, we highlight recent developments in graphene/nanoparticle hybrids and their promising potential in electronic and biological applications. First, the latest advances in synthetic methods for the preparation of the graphene/nanoparticle hybrids are introduced, with the emphasis on approaches to (1) decorate nanoparticles onto two-dimensional graphene and (2) wrap nanoparticles with graphene sheets. The pros and cons of large-scale synthesis are also discussed. Then, the state-of-the-art of graphene/nanoparticle hybrids in electronic and biological applications is reviewed. For electronic applications, we focus on the advantages of using these hybrids in transparent conducting films, as well as energy harvesting and storage. Biological applications, electrochemical biosensing, bioimaging, and drug delivery using the hybrids are showcased. Finally, the future research prospects and challenges in this rapidly developing area are discussed.

Organotin(IV)-loaded mesoporous silica as a biocompatible strategy in cancer treatment

The strong therapeutic potential of an organotin(IV) compound loaded in nanostructured silica (SBA-15pSn) is demonstrated: B16 melanoma tumor growth in syngeneic C57BL/6 mice is almost completely abolished. In contrast to apoptosis as the basic mechanism of the anticancer action of numerous chemotherapeutics, the important advantage of this SBA-15pSn mesoporous material is the induction of cell differentiation, an effect unknown for metal-based drugs and nanomaterials alone. This non-aggressive mode of drug action is highly efficient against cancer cells but is in the concentration range used nontoxic for normal tissue. JNK (Jun-amino-terminal kinase)-independent apoptosis accompanied by the development of the melanocyte-like nonproliferative phenotype of survived cells indicates the extraordinary potential of SBA-15pSn to suppress tumor growth without undesirable compensatory proliferation of malignant cells in response to neighboring cell death.

Photo-redox activated drug delivery systems operating under two photon excitation in the near-IR

We report the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes inter-molecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. We describe the operation of the "snap-top" release mechanism by both one- and two-photon activation. This system presents a proof of concept of a near-IR photoredox-induced nanoparticle delivery system that may lead to a new type of photodynamic drug release therapy.

Enzyme-responsive supramolecular nanovalves crafted by mesoporous silica nanoparticles and choline-sulfonatocalix[4]arene [2]pseudorotaxanes for controlled cargo release

Mesoporous silica nanoparticles (MSNs) have been surface-functionalized with choline moieties encircled by sulfonatocalix[4]arenes. Two enzyme cleavable sites are incorporated in the stalks for specific enzymes to regulate the release of loaded cargos from MSNs. These gated materials show a clear enzymatic response and proven orthogonality.

Facile preparation of ultra-large pore mesoporous silica nanoparticles and their application to the encapsulation of large guest molecules

Pore-enlarged mesoporous silica nanoparticles (MSNs) were prepared directly from as-prepared MSNs through a new, simple method using divalent Ca or Mg salts as both efficient silica etching reagents and as ion exchangers in methanolic solution under mild conditions. The resultant MSNs became almost template-free simultaneously during this etching process. The pore-enlarged MSNs, referred to as Ca-MSN or Mg-MSN, maintained their original hexagonal pore symmetry and particle sizes, but several ultra-large mesopores were generated inside and outside the MSNs together with regular mesopores having expanded pore dimension of around 4-5 nm. The average pore diameters for ultra-large pores were 47.5 nm for Ca-MSN and 52.4 nm for Mg-MSN. The generation of ultra-large pores can be regarded as the collapse of several mesopores into an ultra-large pore. Both Ca-MSN and Mg-MSN were good sorbents for positively charged porphyrin molecules. Additionally, these ultra-large pore MSNs exhibited better adsorption ability than calcined MSN for large proteins and antibodies, such as bovine serum albumin (BSA) and immunoglobulin G (IgG).

A light-responsive release platform by controlling the wetting behavior of hydrophobic surface

Controlled release system based on mesoporous silica (MS) nanomaterials has drawn great attention over the past decades due to its potential biomedical applications. Herein, a light-responsive release system based on MS nanoparticles was achieved by adjusting the wetting of the MS surface. At the starting stage, the surface of MS modified with optimal ratio of spiropyran to fluorinated silane (MS-FSP) was protected from being wetted by water, successfully inhibiting the release of model cargo molecules, fluorescein disodium (FD). Upon irradiation with 365 nm UV light, the conformational conversion of spiropyran from a "closed" state to an "open" state caused the surface to be wetted, leading to the release of FD from the pores. The further in vitro studies demonstrated the system loaded with anticancer drug camptothecin (CPT) could be effectively controlled to release the drug by UV light stimuli to enhance cytotoxicity for EA.hy926 cells and HeLa cells. This wettability-determined smart release platform could be triggered by remote stimuli, which might hold promise in the applications of drug delivery and cancer therapy.

Polyhedral oligomeric silsesquioxane-F68 hybrid vesicles for folate receptor targeted anti-cancer drug delivery

Polyhedral Oligomeric Silsesquioxane (POSS)-F68 hybrid vesicles with an average diameter of 700 nm are produced using a stable solution of heterofunctional POSS having 3-aminopropyl and vinyl groups and pluronic F68 in ethanol-water mixture. Thermogram and zeta potential values evidence the spontaneous self-assembly of POSS into bilayers through H-bonding interaction between the aminopropyl groups, and the effective stabilization of the POSS-bilayers by amphiphilic F68 during solvent-evaporation to form the vesicles. The vesicles are noncytotoxic and dispersible in aqueous solvents through steric stabilization provided by the hydrophilic F68. A highly facile coinclusion method has been used for making doxorubicin and folic acid loaded vesicles. Doxorubicin loaded in the vesicles exhibits a controlled release profile in phosphate buffered saline. Confocal microscopic and flow cytometric studies on the endocytosis of the vesicles by HeLa and HOS cells prove that a noncovalent entrapment of excess folic acid in the vesicles through H-bonding is sufficient to enhance the uptake significantly. POSS-F68 vesicles in combination with folic acid and a chemotherapeutic can have potential for targeted intracellular anti-cancer drug delivery.

Mechanized silica nanoparticles based on reversible bistable [2]pseudorotaxanes as supramolecular nanovalves for multistage pH-controlled release

Mechanized silica nanoparticles installed with the reversible bistable [2]pseudorotaxanes achieve multistage pH-controlled release of cargoes.