A light-responsive reversible molecule-gated system using thymine-modified mesoporous silica nanoparticles

In this paper, a reversible light-responsive molecule-gated system based on mesoporous silica nanoparticles (MSN) functionalized with thymine derivatives is designed and demonstrated. The closing/opening protocol and release of the entrapped guest molecules is related by a photodimerization-cleavage cycle of thymine upon different irradiation. In the system, thymine derivatives with hydrophilicity and biocompatibility were grafted on the pore outlets of MSN. The irradiation with 365 nm wavelength UV light to thymine-functionalized MSN led to the formation of cyclobutane dimer in the pore outlet, subsequently resulting in blockage of pores and strongly inhibiting the diffusion of guest molecules from pores. With 240 nm wavelength UV light irradiation, the photocleavage of cyclobutane dimer opened the pore and allowed the release of the entrapped guest molecules. As a proof-of-the-concept, Ru(bipy)(3)(2+) was selected as the guest molecule. Then the light-responsive loading and release of Ru(bipy)(3)(2+) were investigated. The results indicated that the system had an excellent loading amount (53 μmol g(-1) MSN) and controlled release behavior (82% release after irradiation for 24 h), and the light-responsive loading and release procedure exhibited a good reversibility. Besides, the light-responsive system loaded with Ru(bipy)(3)(2+) molecule could also be used as a light-switchable oxygen sensor.     

Visible‐Light‐Triggered Drug Release from TiO2 Nanotube Arrays: A Controllable Antibacterial Platform

In this work, we use a double‐layered stack of TiO₂ nanotubes (TiNTs) to construct a visible‐light‐triggered drug delivery system. The key for visible light drug release is a hydrophobic cap on the nanotubes containing Au nanoparticles (AuNPs). The AuNPs allow for a photocatalytic scission of the hydrophobic chain under visible light. To demonstrate this principle, we loaded ampicillin (AMP) into the lower part of the TiO₂ nanotube stack, triggered visible‐light‐induced release, and carried out antibacterial studies. The release from the platform becomes most controllable if the drug is silane‐grafted in the hydrophilic bottom layer for drug storage. Thus, visible light photocatalysis can also determine the release kinetics of the active drug from the nanotube wall.     

Preparation of Highly Loaded PAA/PAH Layer-by-layer Films by Combining Acid Transformation and Templating Methods

Enhancing the molecular loading capability of layer-by-layer(LbL)method holds high importance in environmental and biomedical application.Here,we reported a strategy to prepare highly loaded poly(acrylic acid)(PAA)/poly(allylamine hydrochloride)(PAH)LbL films by combining the particulate templating strategy and acid treatment film transformation and realized tlae efficient loading of hydrophilic small molecules.The loaded molecules can be released in a pH-controlled manner.A slow release speed was observed in the acidic solutions with pH value of 3.Abrupt releases were observed at higher pH values(5 or 7).     

Matrix isolation spectroscopic and theoretical study of water adsorption and hydrolysis on molecular tantalum and niobium oxides

The reactions of molecular tantalum and niobium monoxides and dioxides with water were investigated by matrix isolation infrared spectroscopy. In solid neon, the metal monoxide and dioxide molecules reacted with water to form the MO(H(2)O) and MO(2)(H(2)O) (M = Ta, Nb) complexes spontaneously on annealing. The MO(H(2)O) complexes photochemically rearranged to the more stable HMO(OH) isomers via one hydrogen atom transfer from water to the metal center under visible light excitation. In contrast, the MO(2)(H(2)O) complexes isomerized to the more stable MO(OH)(2) molecules via a hydrogen atom transfer from water to one of the oxygen atoms of metal dioxide upon visible light irradiation. The aforementioned species were identified by isotopic-substituted experiments as well as density functional calculations.     

A visible light responsive azobenzene‐functionalized polymer: Synthesis,self‐assembly,and photoresponsive properties

A novel visible light responsive random copolymer consisting of hydrophobic azobenzene‐containing acrylate units and hydrophilic acrylic acid units has been prepared. The azobenzene molecule bearing methoxy groups at all four ortho positions is readily synthesized by one‐step conversion of diazotization. The as‐prepared polymer can self‐assemble into nanoparticles in water due to its amphiphilic nature. The tetra‐o‐methoxy‐substituted azobenzene‐functionalized polymer can exhibit the trans‐to‐cis photoswitching under the irradiation with green light of 520 nm and the cis‐to‐trans photoswitching under the irradiation with blue light of 420 nm in both solution and aggregate state. The morphologies of the self‐assembled nanoparticles are revealed by TEM and DLS. The controlled release of loaded molecules from the nanoparticles can be realized by adjusting pH value since the copolymer possesses pH responsive acrylic acid groups. The fluorescence of loaded Nile Red in the nanoparticles can be tuned upon the visible light irradiation. The reversible photoswitching of the azobenzene‐functionalized polymer under visible light may endow the polymer with wide applications without using ultraviolet light at all. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2768–2775     

Visible-light-triggered release of nitric oxide from N-pyramidal nitrosamines

Although many organic/inorganic compounds that release nitric oxide (NO) upon photoirradiation (phototriggered caged-NOs) have been reported, their photoabsorption wavelengths mostly lie in the UV region, because X-NO bonds (X=heteroatom and metal) generally have rather strong π-bond character. Thus, it is intrinsically difficult to generate organic compounds that release NO under visible light irradiation. Herein, the structures and properties of N-pyramidal nitrosamine derivatives of 7-azabicyclo[2.2.1]heptanes that release NO under visible light irradiation are described. Bathochromic shifts of the absorptions of these nitrosamines, attributed to HOMO (n)-LUMO (π*) transitions associated with the nonplanar structure of the N-NO moiety, enable the molecules to absorb visible light, which results in N-NO bond cleavage. Thus, these compounds are innate organic caged-NOs that are uncaged by visible light.     

Visible light-induced electron transfer from di-mu-oxo-bridged dinuclear Mn complexes to Cr centers in silica nanopores

The compound (bpy) 2Mn (III)(mu-O) 2Mn (IV)(bpy) 2, a structural model relevant for the photosynthetic water oxidation complex, was coupled to single Cr (VI) charge-transfer chromophores in the channels of the nanoporous oxide AlMCM-41. Mn K-edge EXAFS spectroscopy confirmed that the di-mu-oxo dinuclear Mn core of the complex is unaffected when loaded into the nanoscale pores. Observation of the 16-line EPR signal characteristic of Mn (III)(mu-O) 2Mn (IV) demonstrates that the majority of the loaded complexes retained their nascent oxidation state in the presence or absence of Cr (VI) centers. The FT-Raman spectrum upon visible light excitation of the Cr (VI)-O (II) --> Cr (V)-O (I) ligand-to-metal charge transfer reveals electron transfer from Mn (III)(mu-O) 2Mn (IV) (Mn-O stretch at 700 cm (-1)) to Cr (VI), resulting in the formation of Cr (V) and Mn (IV)(mu-O) 2Mn (IV) (Mn-O stretch at 645 cm (-1)). All initial and final states are directly observed by FT-Raman or EPR spectroscopy, and the assignments are corroborated by X-ray absorption spectroscopy measurements. The endoergic charge separation products (Delta E o = -0.6 V) remain after several minutes, which points to spatial separation of Cr (V) and Mn (IV)(mu-O) 2Mn (IV) as a consequence of hole (O (I)) hopping as a major contributing mechanism. This is the first observation of visible light-induced oxidation of a potential water oxidation complex by a metal charge-transfer pump in a nanoporous environment. These findings will allow for the assembly and photochemical characterization of well-defined transition metal molecular units, with the ultimate goal of performing endothermic, multielectron transformations that are coupled to visible light electron pumps in nanostructured scaffolds.     

Polymer Nanoparticles for Controlled Release Stimulated by Visible Light and pH

Polymer nanoparticles are prepared by self‐assembly of visible light and pH sensitive perylene‐functionalized copolymers which are synthesized by quaternization between 1‐(bromomethyl)perylene and the dimethylaminoethyl units of poly(dimethylaminoethyl methacrylate) (PDMAEMA). The perylene‐containing polymethacrylate segments afford the system visible light responsiveness and the unquaternized PDMAEMA segments afford the system pH responsiveness. The self‐assembled nanoparticles exhibit a unique dual stimuli response. They can be photocleaved under visible light irradiation, shrunken to smaller nanoparticles at high pH, and swollen at low pH. The structural change endows the nanoparticle with great potential as a sensitive nanocarrier for controlled release of Nile Red and lysozyme under this stimulation. The visible light responsiveness and synergistic effect on the release of loaded molecules with the dual stimulation may obviate the need for harsh conditions such as UV light or extreme pH stimulation, rendering the system more applicable under mild conditions.

     

Photo‐Modulated Therapeutic Protein Release from a Hydrogel Depot Using Visible Light

The use of biomacromolecular therapeutics has revolutionized disease treatment, but frequent injections are required owing to their short half‐life in vivo. Thus there is a need for a drug delivery system that acts as a reservoir and releases the drug remotely “on demand”. Here we demonstrate a simple light‐triggered local drug delivery system through photo‐thermal interactions of polymer‐coated gold nanoparticles (AuNPs) inside an agarose hydrogel as therapeutic depot. Localized temperature increase induced by the visible light exposure caused reversible softening of the hydrogel matrix to release the pre‐loaded therapeutics. The release profile can be adjusted by AuNPs and agarose concentrations, light intensity and exposure time. Importantly, the biological activity of the released bevacizumab was highly retained. In this study we demonstrate the potential application of this facile AuNPs/hydrogel system for ocular therapeutics delivery through its versatility to release multiple biologics, compatibility to ocular cells and spatiotemporal control using visible light.     

表面活性剂胶束实现疏水分子在聚合物微凝胶层层组装膜中的高效负载

基于层层组装技术制备了聚烯丙基胺-葡聚糖微凝胶(记作PAH-D)/透明质酸钠(HA)膜, 将包覆有芘分子的十二烷基硫酸钠(SDS)表面活性剂胶束基于静电作用力负载到PAH-D/HA微凝胶膜中, 实现了疏水分子芘在微凝胶膜中的高效负载. 紫外-可见吸收光谱和荧光光谱证实了SDS胶束包覆的芘分子被稳定地负载在PAH-D微凝胶膜中. 透过光谱表明负载有芘分子的(PAH-D/HA)*10微凝胶膜在可见光区仍保持良好光学透过性. 芘在膜中的负载量可以通过改变PAH-D/HA微凝胶膜的沉积周期数和SDS胶束中包覆芘分子的浓度而实现调控. 具有光致变色性质的螺吡喃分子同样可以借助SDS胶束负载到PAH-D/HA微凝胶膜中, 制备具有光致变色性质的层层组装膜. 本工作为疏水有机分子在层层组装聚合物膜中的高效负载提供了一种简便、易行的方法.     

Photocatalysis Enables Visible‐Light Uncaging of Bioactive Molecules in Live Cells

The photo‐manipulation of bioactive molecules provides unique advantages due to the high temporal and spatial precision of light. The first visible‐light uncaging reaction by photocatalytic deboronative hydroxylation in live cells is now demonstrated. Using Fluorescein and Rhodamine derivatives as photocatalysts and ascorbates as reductants, transient hydrogen peroxides were generated from molecular oxygen to uncage phenol, alcohol, and amine functional groups on bioactive molecules in bacteria and mammalian cells, including neurons. This effective visible‐light uncaging reaction enabled the light‐inducible protein expression, the photo‐manipulation of membrane potentials, and the subcellular‐specific photo‐release of small molecules.     

Manganese carbonyls bearing tripodal polypyridine ligands as photoactive carbon monoxide-releasing molecules

The recently discovered cytoprotective action of CO has raised interest in exogenous CO-releasing materials (CORMs) such as metal carbonyls (CO complexes of transition metals). To achieve control on CO delivery with metal carbonyls, we synthesized and characterized three Mn(I) carbonyls, namely, [Mn(tpa)(CO)(3)]ClO(4) [1, where tpa = tris(2-pyridyl)amine], [Mn(dpa)(CO)(3)]Br [2, where dpa = N,N-bis(2-pyridylmethyl)amine], and [Mn(pqa)(CO)(3)]ClO(4) [3, where pqa = (2-pyridylmethyl)(2-quinolylmethyl)amine], by crystallography and various spectroscopic techniques. All three carbonyls are sensitive to light and release CO when illuminated with low-power UV (5-10 mW) and visible (λ > 350 nm, ~100 mW) light. The sensitivity of 1-3 to light has been assessed with respect to the number of pyridine groups in their ligand frames. When a pyridine ring is replaced with quinoline, extended conjugation in the ligand frame increases the absorptivity and makes the resulting carbonyl 3 more sensitive to visible light. These photosensitive CORMs (photoCORMs) have been employed to deliver CO to myoglobin under the control of light. The superior stability of 3 in aqueous media makes it a photoCORM suitable for inducing vasorelaxation in mouse aortic muscle rings.     

Conjugated Polymer Nanoparticles with Appended Photo‐Responsive Units for Controlled Drug Delivery,Release, and Imaging

Carriers that can afford tunable physical and structural changes are envisioned to address critical issues in controlled drug delivery applications. Herein, photo‐responsive conjugated polymer nanoparticles (CPNs) functionalized with donor–acceptor Stenhouse adduct (DASA) and folic acid units for controlled drug delivery and imaging are reported. Upon visible‐light (λ=550 nm) irradiation, CPNs simultaneously undergo structure, color, and polarity changes that release encapsulated drugs into the cells. The backbone of CPNs favors FRET to DASA units boosting their fluorescence. Notably, drug‐loaded CPNs exhibit excellent biocompatibility in the dark, indicating perfect control of the light trigger over drug release. Delivery of both hydrophilic and hydrophobic drugs with good loading efficiency was demonstrated. This strategy enables remotely controlled drug delivery with visible‐light irradiation, which sets an example for designing delivery vehicles for non‐invasive therapeutics.     

Controlled Release of Fragrant Molecules with Visible Light

Controlled release of odorous molecules is the key to digital scent technology which will add another dimension to electronics. Photorelease is a cold mechanism that promises better temporal and spatial control than thermal release. Herein we report a novel material composed of an acid‐sensitive polymer carrying a fragrant aldehyde and a reversible metastable‐state photoacid. It releases the fragrant molecule under visible light, and stops releasing it after the light is turned off. A metastable‐state photoacid with a fast reverse‐reaction rate was developed to quickly stop the release after irradiation. Both the carrier polymer and the photoacid can be reused after all the fragrant molecules have been released. The material combines the advantages of visible‐light activity, fast on/off rate, easy preparation, and recyclability, and thus is promising for digital scent technology.     

Conjugated Polymer Nanoparticles with Appended Photo‐Responsive Units for Controlled Drug Delivery,Release, and Imaging

Carriers that can afford tunable physical and structural changes are envisioned to address critical issues in controlled drug delivery applications. Herein, photo‐responsive conjugated polymer nanoparticles (CPNs) functionalized with donor–acceptor Stenhouse adduct (DASA) and folic acid units for controlled drug delivery and imaging are reported. Upon visible‐light (λ=550 nm) irradiation, CPNs simultaneously undergo structure, color, and polarity changes that release encapsulated drugs into the cells. The backbone of CPNs favors FRET to DASA units boosting their fluorescence. Notably, drug‐loaded CPNs exhibit excellent biocompatibility in the dark, indicating perfect control of the light trigger over drug release. Delivery of both hydrophilic and hydrophobic drugs with good loading efficiency was demonstrated. This strategy enables remotely controlled drug delivery with visible‐light irradiation, which sets an example for designing delivery vehicles for non‐invasive therapeutics.     

Individually Addressable Patterned Multilayer Microchambers for Site‐Specific Release‐On‐Demand

Patterned arrays of light‐responsive microchambers are suggested as candidates for site‐specific release of chemicals in small and precisely defined quantities on demand. A composite film is made of poly(allylammonium)‐poly(styrene sulfonate) multilayers and gold nanoparticles incorporated between subsequent stacks of polyelectrolytes. The film shaped as microchambers is loaded with colloid particles or oil‐soluble molecules. The microchambers are sealed onto a glass slide precoated with an adhesive poly(diallyldimethylammonium)‐poly(styrene sulfonate) multilayer film. A focused laser beam is used for remote addressing the individual microchambers and site‐specific release of the loaded cargo.     

A Facile One‐Pot Synthesis of Layered Protonated Titanate Nanosheets Loaded with Silver Nanoparticles with Enhanced Visible‐Light Photocatalytic Performance

Layered protonated titanate nanosheets (LPTNs) loaded with silver nanoparticles are prepared by a simple one‐pot hydrothermal route in silver‐ammonia solution. The as‐synthesized Ag‐loaded LPTNs possess large specific surface area. The Ag nanoparticles are highly dispersed on the surface of the LPTNs. They have negligible effects on the crystal structure, crystallinity, and surface area of the LPTNs but result in considerable enhancement of visible‐light absorption and in a red‐shift of the band gap for the LPTNs. The Ag‐loaded LPTNs show enhanced photocatalytic activity for both liquid‐ and gas‐phase reactions under visible‐light irradiation. Moreover, the photocatalytic activity first increases gradually with increasing Ag loading content, and then decreases after maximizing at an optimal Ag content. At the Ag loading content of 2.87 mol % and 1.57 mol %, the Ag‐loaded LPTNs exhibit the highest visible‐light photocatalytic activity for degradation of rhodamine B in water and mineralization of benzene in air, respectively. An alternative possible mechanism for the enhancement of the visible‐light photocatalytic activity is also proposed.     

Novel in situ N-doped (BiO)2CO3 hierarchical microspheres self-assembled by nanosheets as efficient and durable visible light driven photocatalyst

Novel N-doped (BiO)(2)CO(3) hierarchical microspheres (N-BOC) were fabricated by a facile one-pot template free method on the basis of hydrothermal treatment of bismuth citrate and urea in water for the first time. The N-BOC sample was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, N(2) adsorption-desorption isotherms, and Fourier transform-infrared spectroscopy. The N-BOC was constructed by the self-assembly of single-crystalline nanosheets. The aggregation of nanosheets led to the formation of hierarchical framework with mesopores, which is favorable for efficient transport of reaction molecules and harvesting of photoenergy. Due to the in situ doped nitrogen substituting for oxygen in the lattice of (BiO)(2)CO(3), the band gap of N-BOC was reduced from 3.4 to 2.5 eV, making N-BOC visible light active. The N-BOC exhibited not only excellent visible light photocatalytic activity, but also high photochemical stability and durability during repeated and long-term photocatalytic removal of NO in air due to the special hierarchical structure. This work demonstrates that the facile fabrication method for N-BOC combined with the associated outstanding visible light photocatalytic performance could provide new insights into the morphology-controlled fabrication of nanostructured photocatalytic materials for environmental pollution control.     

Photon gated transport at the glass nanopore electrode

The interior surface of the glass nanopore electrode was modified with spiropyran moieties to impart photochemical control of molecular transport through the pore orifice (15-90 nm radius). In low ionic strength acetonitrile solutions, diffusion of a positively charged species (Fe(bpy)(3)(2+)) is electrostatically blocked with approximately 100% efficiency by UV light-induced conversion of the neutral surface-bound spiropyran to its protonated merocyanine form (MEH+). Transport through the pore orifice is restored by either irradiation of the electrode with visible light to convert MEH+ back to spiropyran or addition of a sufficient quantity of supporting electrolyte to screen the electrostatic field associated with MEH+. The transport of neutral redox species through spiropyran-modified glass nanopores is not affected by light, allowing photoselective transport of redox molecules to the electrode surface based on charge discrimination. The glass nanopore electrode can also be employed as a photochemical trap, by UV light conversion of surface-bound spiropyran to MEH+, preventing Fe(bpy)(3)(2+) initially in the pore from diffusing through the orifice.     

Sensitization of ruthenium nitrosyls to visible light via direct coordination of the dye resorufin: trackable NO donors for light-triggered NO delivery to cellular targets

Three nitrosyl-dye conjugates, namely, [(Me 2bpb)Ru(NO)(Resf)] ( 1-Resf), [(Me 2bQb)Ru(NO)(Resf)] ( 2-Resf), and [((OMe) 2bQb)Ru(NO)(Resf)] ( 3-Resf) have been synthesized via direct replacement of the chloride ligand of the parent {Ru-NO} (6) nitrosyls of the type [(R 2byb)Ru(NO)(L)] with the anionic tricyclic dye resorufin (Resf). The structures of 1-Resf- 3-Resf have been determined by X-ray crystallography. The dye is coordinated to the ruthenium centers of these conjugates via the phenolato-O atom and is trans to NO. Systematic red shift of the d pi(Ru) --> pi*(NO) transition of the parent nitrosyls [(R 2byb)Ru(NO)(L)] due to changes in R and y in the equatorial tetradentate ligand R 2byb (2-) results in its eventual merge with the intense absorption band of the dye around 500 nm in 3-Resf. Unlike the UV-sensitive parent [(R 2byb)Ru(NO)(L)] nitrosyls, these dye-sensitized nitrosyls rapidly release NO when exposed to visible light (lambda >/= 465 nm). Comparison of the photochemical parameters reveals that direct coordination of the light-harvesting chromophore to the ruthenium center in the present nitrosyls results in a significantly greater extent of sensitization to visible light compared to nitrosyls with appended chromophore (linked via alkyl chains). 1-Resf has been employed as a "trackable" NO donor to promote NO-induced apoptosis in MDA-MB-231 human breast cancer cells under the control of light. The results of this work demonstrate that (a) the d pi(Ru) --> pi*(NO) transition (photoband) of {Ru-NO} (6) nitrosyls can be tuned into visible range via careful alteration of the ligand frame(s) and (b) such nitrosyls can be significantly sensitized to visible light by directly ligating a light-harvesting chromophore to the ruthenium center. The potential of these photosensitive nitrosyl-dye conjugates as (i) biological tools to study the effects of NO in cellular environments and (ii) "trackable" NO donors in photodynamic therapy of malignancies (such as skin cancer) has been discussed.