Light-Operated Mechanized Nanoparticles

Mesoporous silica nanoparticles for bioadsorption, enzyme immobilisation, and delivery carriers

Mesoporous silica nanoparticles (MSNs) provide a non-invasive and biocompatible delivery platform for a broad range of applications in therapeutics, pharmaceuticals and diagnosis. The creation of smart, stimuli-responsive systems that respond to subtle changes in the local cellular environment are likely to yield long term solutions to many of the current drug/gene/DNA/RNA delivery problems. In addition, MSNs have proven to be promising supports for enzyme immobilisation, enabling the enzymes to retain their activity, affording them greater potential for wide applications in biocatalysis and energy. This review provides a comprehensive summary of the advances made in the last decade and a future outlook on possible applications of MSNs as nanocontainers for storage and delivery of biomolecules. We discuss some of the important factors affecting the adsorption and release of biomolecules in MSNs and review of the cytotoxicity aspects of such nanomaterials. The review also highlights some promising work on enzyme immobilisation using mesoporous silica nanoparticles.

Aspect ratio determines the quantity of mesoporous silica nanoparticle uptake by a small GTPase-dependent macropinocytosis mechanism

Although the aspect ratio (AR) of engineered nanomaterials (ENMs) is one of the key physicochemical parameters that could determine biological outcome, not much is understood about how AR contributes to shaping biological outcome. By using a mesoporous silica nanoparticle (MSNP) library that has been constructed to cover a range of different lengths, we could demonstrate that the AR of rod-shaped particles determines the rate and abundance of MSNP uptake by a macropinocytosis process in HeLa and A549 cancer cell lines. MSNPs with an AR of 2.1-2.5 were taken up in larger quantities compared to shorter or longer length rods by a process that is sensitive to amiloride, cytochalasin D, azide, and 4 °C inhibition. The rods with intermediary AR also induced the maximal number of filopodia, actin polymerization, and activation of small GTP-binding proteins (e.g., Rac1, CDC42) that involve assembly of the actin cytoskeleton and filopodia formation. When assessing the role of AR in the delivery of paclitaxel or camptothecin, the rods with AR 2.1-2.5 were clearly more efficient for drug delivery and generation of cytotoxic killing in HeLa cells. All considered, our data suggest an active sensoring mechanism by which HeLa and A549 cells are capable of detecting AR differences in MSNP to the extent that accelerated macropinocytosis can be used to achieve more efficient drug delivery.

The design, synthesis and photochemical study of a biomimetic cyclodextrin model of photoactive yellow protein (PYP)

The design, synthesis and study of the photophysical and photochemical properties of the first biomimetic cyclodextrin (CD) model of photoactive yellow protein (PYP) are described. This model bears a deprotonated trans-p-coumaric acid chromophore, covalently linked via a cysteine moiety to a permethylated 6-monoamino β-CD. NMR and UV/Visible spectroscopy studies showed the formation of strong self-inclusion complexes in water at basic pH. Steady-state photolysis demonstrated that, unlike the free chromophore in solution, excitation of the model molecule leads to the formation of a photoproduct identified as the cis isomer by NMR spectroscopy. These observations provide evidence that the restricted CD cavity offers a promising framework for the design of biomimetic models of the PYP hydrophobic pocket.

Chloride anion triggered motion in a bis-imidazolium rotaxane

We report the first bis-imidazolium-containing rotaxane, synthesised via anion templated self-assembly. Its co-conformation is controlled by a chloride anion recognition mechanism, thus demonstrating the viability of this protocol as a stimulus for shuttling molecular motion.

Enzyme-responsive intracellular controlled release using nanometric silica mesoporous supports capped with "saccharides"

The synthesis of new capped silica mesoporous nanoparticles for on-command delivery applications is described. The gate-like functional hybrid systems consisted of nanoscopic MCM-41-based materials functionalized on the pore outlets with different "saccharide" derivatives and a dye contained in the mesopores. A series of hydrolyzed starch products as saccharides were selected. The mesoporous silica nanoparticles S1, S2, and S3 containing the grafted starch derivatives Glucidex 47, Gludicex 39, and Glucidex 29 were synthesized. Additionally, for comparative purposes solid S4 containing lactose was prepared. Delivery studies in pure water in the presence of pancreatin or β-d-galactosidase were carried out for S1-S3 and S4, respectively. S1, S2, and especially S3 showed very low release in the absence of enzyme, but displayed cargo delivery in the presence of the corresponding enzyme. Moreover, nanoparticles of S1 were used to study the controlled release of the dye in intracellular media. Cell viability assays using HeLa and LLC-PK1 cells indicated that S1 nanoparticles were devoid of unspecific cell toxicity. The endocytosis process for S1 nanoparticle internalization in HeLa cells was confirmed, and the anchored starch was degraded by the lysosomal enzymes. Furthermore, a new mesoporous silica nanoparticle functionalized with Glucidex 47 and loaded with a cytotoxic, S1-DOX, was developed. The cell viability with S1-DOX decreased due to the internalization of the nanoparticle, enzyme-dependent opening of the saccharide molecular gate and the consequent release of the cytotoxic agent. As far as the authors know, this is the first example of enzyme-induced in-cell delivery using capped silica mesoporous nanoparticles.

Fluorescent pH-sensing organic/inorganic hybrid mesoporous silica nanoparticles with tunable redox-responsive release capability

We report on the fabrication of fluorescent pH-sensing organic/inorganic hybrid mesoporous silica nanoparticles (MSN) capable of tunable redox-responsive release of embedded guest molecules. The reversible addition-fragmentation chain transfer (RAFT) copolymerization of N-(acryloxy)succinimide (NAS), oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA), and 1,8-naphthalimide-based pH-sensing monomer (NaphMA) at the surface of MSN led to fluorescent organic/inorganic hybrid MSN. The obtained hybrid MSN exhibits excellent water dispersibility and acts as sensitive fluorescent pH probes in the range pH 4-8 due to the presence of NaphMA moieties. After loading with rhodamine B (RhB) as a model drug molecule, P(NAS-co-OEGMA-co- NaphMA) brushes at the surface of hybrid MSN were cross-linked with cystamine to block nanopore entrances for the effective retention of guest molecules. Taking advantage of disulfide-containing cross-linkers, the release rate of RhB can be easily adjusted by adding varying concentrations of dithiothreitol (DTT), which can cleave the disulfide linkage to open blocked nanopores. The increase of DTT concentration from 0 to 20 mM led to 20-30 times enhancement of RhB release rate. The reported multifunctional hybrid MSN augurs well for applications in controlled-release nanocarriers, cell and tissue imaging, and clinical diagnosis.

One-pot preparation of ferrocene-functionalized polymer brushes on gold substrates by combined surface-initiated atom transfer radical polymerization and "click chemistry"

A gold substrate with surface-grafted ferrocene functional polymer brushes, or Au-g-PFTMA surface [PFTMA = poly(5-ferrocene-triazolyl methacrylate)], was prepared by a combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and "click chemistry" in one pot, in the presence of 2-azidoethyl methacrylate (AzEMA), ethynyl ferrocene, CuBr catalyst, CuBr(2) deactivator, and pentamethyldiethylenetriamine ligand. Thus, SI-ATRP of AzEMA from the Au substrate (the "grafting from" process) and click chemistry of the ethynyl ferrocene to the azide functional group of AzEMA (the "grafting to" process) proceeded simultaneously to produce the functional PFTMA brushes on the Au surface. Kinetic studies suggest that the reaction involving simultaneous SI-ATRP and click chemistry is still consistent with a controlled/"living" process. The composition and physical properties of the modified gold surface were analyzed by X-ray photoelectron spectroscopy, water contact angle measurement, and cyclic voltammetry. The redox-responsive properties of the ferrocene-functionalized polymer brushes on the Au-g-PFTMA surface were demonstrated in the reversible loading-unloading step of the β-cyclodextrin polymer via host-guest interaction.

Mesoporous silica nanoparticles for intracellular controlled drug delivery

The application of nanotechnology in the field of drug delivery has attracted much attention in the latest decades. Recent breakthroughs on the morphology control and surface functionalization of inorganic-based delivery vehicles, such as mesoporous silica nanoparticles (MSNs), have brought new possibilities to this burgeoning area of research. The ability to functionalize the surface of mesoporous-silica-based nanocarriers with stimuli-responsive groups, nanoparticles, polymers, and proteins that work as caps and gatekeepers for controlled release of various cargos is just one of the exciting results reported in the literature that highlights MSNs as a promising platform for various biotechnological and biomedical applications. This review focuses on the most recent progresses in the application of MSNs for intracellular drug delivery. The latest research on the pathways of entry into live mammalian and plant cells together with intracellular trafficking are described. One of the main areas of interest in this field is the development of site-specific drug delivery vehicles; the contribution of MSNs toward this topic is also summarized. In addition, the current research progress on the biocompatibility of this material in vitro and in vivo is discussed. Finally, the latest breakthroughs for intracellular controlled drug release using stimuli-responsive mesoporous-silica-based systems are described.

Light-responsive nanogated ensemble based on polymer grafted mesoporous silica hybrid nanoparticles

Mesoporous silica nanoparticles grafted with light-responsive polymer on the outer surface were developed as novel nanogated ensembles, which allow encapsulation and release of drug and biological molecules under light irradiation.

Photoresponsive host-guest systems based on a new azobenzene-containing cryptand

A new azobenzene-bridged cryptand was synthesized; it can be well controlled between cis and trans isomers by irradiation with different wavelengths or by being heated. It was found that this cryptand exhibits an ON-OFF binding ability with 2,7-diazapyrenium (DAP) derivatives. It binds DAP derivatives as the cis isomer only, as demonstrated by various methods. The fluorescence property of DAP derivatives endows these host-guest systems with detectable fluorescent output signals, which makes monitoring these photoresponsive systems convenient.

Biocompatibility, biodistribution, and drug-delivery efficiency of mesoporous silica nanoparticles for cancer therapy in animals

Mesoporous silica nanoparticles (MSNs) are a promising material for drug delivery. In this Full Paper, MSNs are first shown to be well tolerated, as demonstrated by serological, hematological, and histopathological examinations of blood samples and mouse tissues after MSN injection. Biodistribution studies using human cancer xenografts are carried out with in vivo imaging and fluorescent microscopy imaging, as well as with inductively coupled plasma mass spectroscopy. The results show that MSNs preferentially accumulate in tumors. Finally, the drug-delivery capability of MSNs is demonstrated by following tumor growth in mice treated with camptothecin-loaded MSNs. These results indicate that MSNs are biocompatible, preferentially accumulate in tumors, and effectively deliver drugs to the tumors and suppress tumor growth.

Light-sensitive intelligent drug delivery systems of coumarin-modified mesoporous bioactive glass

Functionalized mesoporous bioactive glasses (MBG) with photoactive coumarin demonstrates photo-responsive dimerization resulting in reversible gate operation. Coumarin-modified MBG was used as a drug delivery carrier to investigate drug storage/release characteristics using phenanthrene as a model drug. Irradiation with UV light (>310 nm) induced photo-dimerization of the coumarin-modified MBG, which led to the pores' closing with cyclobutane dimers and trapping of the guest phenanthrene in the mesopores. However, irradiating the dimerized-coumarin-modified MBG with shorter wavelength UV light (approximately 250 nm) regenerates the coumarin monomer derivative by the photo-cleavage of cyclobutane dimers, such that trapped guest molecules are released from the mesopores. The structural, morphological, textural and optical properties are well characterized by X-ray diffraction, transmission electron microscopy, N(2) adsorption/desorption, and UV-visible spectroscopy. The results reveal that the MBG exhibits the typical ordered characteristics of the hexagonal mesostructure. The system demonstrates great potential in light-sensitive intelligent drug delivery systems and disease therapy fields.

Current directions in core-shell nanoparticle design

Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems.

Smart nanocontainers and nanoreactors

We highlight recent advances in the synthesis of nanocarriers and nanoreactors from synthetic and biological building blocks with emphasis on the stimulus-responsive regulation of their function.

PM-IRRAS assessment of the compression-mediated orientation of the nanocavity of a monoacylated beta-cyclodextrin in monolayers at the air-water interface

The structural orientation adopted along the compression-decompression isotherm by a monoacylated beta-cyclodextrin (C16-betaCD) at the air-water interface was assessed by polarization-modulation infrared reflection-adsorption spectroscopy (PM-IRRAS). The adoption of different orientations of the cyclic oligosaccharide unit, relative to the interfacial plane, was interpreted analyzing the PM-IRRAS band intensity ratios of specific vibrations corresponding to the cyclodextrin moiety as a function of the surface pressure for successive compression/decompression cycles. The spectroscopic analysis revealed that the cyclic oligosaccharide modifies its position under compression from one in which the plane of the cavity of the monoacylated beta-cyclodextrin lies almost parallel to the interface to another in which the plane of the cavity is perpendicular to the interface. Through the PM-IRRAS analysis, it was also possible to evidence the establishment of an intermolecular hydrogen bonding network that may play an important role in the dynamic properties of the monolayer packing. The hydrogen bonding network becomes more important with the increases of surface pressure, up to a molecular packing limit, and it imparts the surface properties of the film for future compression-decompression cycles.

Double-layer mediated electromechanical response of amyloid fibrils in liquid environment

Harnessing electrical bias-induced mechanical motion on the nanometer and molecular scale is a critical step toward understanding the fundamental mechanisms of redox processes and implementation of molecular electromechanical machines. Probing these phenomena in biomolecular systems requires electromechanical measurements be performed in liquid environments. Here we demonstrate the use of band excitation piezoresponse force microscopy for probing electromechanical coupling in amyloid fibrils. The approaches for separating the elastic and electromechanical contributions based on functional fits and multivariate statistical analysis are presented. We demonstrate that in the bulk of the fibril the electromechanical response is dominated by double-layer effects (consistent with shear piezoelectricity of biomolecules), while a number of electromechanically active hot spots possibly related to structural defects are observed.

pH-responsive nanogated ensemble based on gold-capped mesoporous silica through an acid-labile acetal linker

A new pH-responsive hybrid nanogated ensemble has been developed by using acetal group linked gold nanoparticle capped mesoporous silica. The hydrolysis of acetal linker at acidic environment makes the gold nanoparticles work as a gatekeeper to control the release of guest molecules from mesoporous silica under different pH's.