Encapsulation Of Pyrene Research Articles

Pyrene doped silica nanoparticles: Synthesis, oxygen sensing, and singlet oxygen generation

Dye-doped silica nanoparticles have garnered attention from researchers owing to their beneficial properties, such as signal amplification, surface modification, and biocompatibility. In this study, pyrene-doped silica nanoparticles (PSNPs) were prepared using the reverse microemulsion approach. Pyrenebutyric acid conjugated with aminopropyltriethoxysilane was synthesized to obtain durable PSNPs with low dye leaching via the covalent encapsulation of pyrene inside a silica matrix. The PSNPs were spherical, with a diameter of 72 nm. The PSNPs exhibited excimer fluorescence upon photoexcitation. To demonstrate the applicability of the synthesized PSNPs in biological applications, including photodynamic therapy (PDT) and oxygen sensing, the influence of oxygen on the fluorescence spectrum was investigated. The excimer fluorescence intensity was quenched by oxygen, along with a decrease in fluorescence lifetime. Ratiometric fluorescence sensing and fluorescence lifetime sensing of oxygen concentration were demonstrated. The biomolecular quenching rate constant was evaluated using the Stern–Volmer plot of the fluorescence lifetime. Moreover, utilizing a chemical trap of singlet oxygen molecules, it was demonstrated that singlet oxygen was generated by the photosensitization of PSNP. The PSNPs synthesized in this study are potentially capable of oxygen sensing, PDT, and bioimaging for various biological applications.

Tailored Water-Soluble Covalent Organic Cages for Encapsulation of Pyrene and Information Encryption.

Forming pyridine salts to construct covalent organic cages is an effective strategy for constructing covalent cage compounds. Covalent organic cages based on pyridine salt structures are prone to form water-soluble supramolecular compounds. Herein, we designed and synthesized a triangular prism-shaped hexagonal cage with a larger cavity and relatively flexible conformation. The supramolecular cage structure was also applied to the encapsulation of pyrene and information encryption.

The host–guest inclusion driven by host-stabilized charge transfer for construction of sequentially red-shifted mechanochromic system

Developing more extensive methods to understand the underlying structure-property relationship of mechanochromic luminescent molecules is demanding but remains challenging. Herein, the effect of host-guest interaction on the mechanochromic properties of organic molecules is illustrated. A series of pyridinium-functionalized triphenylamine derivatives show bathochromic-shifted emission upon mechanical stimulation. These derivatives bind to cucurbit[8]uril to form homoternary host-guest inclusion complexes through host-stabilized intermolecular charge transfer interactions. Remarkably, the homoternary complexes exhibit longer emission than that of free guests in the solid state (even longer than ground guests), and a further bathochromic-shifted emission is observed upon grinding. Additionally, a heteroternary complex constructed through the encapsulation of pyrene (donor) and pyridinium (acceptor) guest pair in cucurbit[8]uril also displays the mechanochromic luminescent property. This work not only discloses the effect of host-guest inclusion on the mechanochromic property of organic molecules, but also provides a principle and a facile way to design the sequentially red-shifted mechanochromic materials.

Sustained release of hydrophobic dye [pyrene] from self-aggregated nonionic amphiphilic micelles: Effect of pH and temperature

The C 18 unsaturated dendritic amphiphiles of different generations were examined as an encapsulating agent for hydrophobes. The DLS studies demonstrated the nano-aggregation and encapsulation of pyrene within the hydrophobic cores & pyrene excimer formation, and its sustained pH-dependent release was observed by UV–Vis spectroscopy. The sustained release of pyrene from the core of micelles was studied to estimate the temperature and pH susceptibility of the ester linker. The non-ionic ester-linked amphiphiles of all three generations showed a significant encapsulation of dye at pH 7.0. The results of sustained release of hydrophobic dye at 37 ○ C in 24 h to 48 h of treatment with a solution of pH 6.2, 7.4 and 8.2 are remarkable.

Reversible crosslinking terpolymer shell-based mesoporous silica nanoparticles as on-off nanocarriers for pyrene-releasing application

Abstract Mesoporous silica nanoparticles (MSNs) were successfully endowed with on-off transport ability and stimuli-responsive property through surface modification. The MSNs with large specific surface areas were synthesized using optimized Stober method, and then successively modified by amino- and 2-bromoisobutyrate-functionalization. Finally, MSNs grafted with reversible crosslinking terpolymer (MSNs-g-PDMV) were achieved through surface-initiated atom transfer radical polymerization. The resultant MSNs-g-PDMV and their intermediates were confirmed by TEM, SEM, XPS, FTIR, and so on. Pyrene was chosen to evaluate their drug loading and controlled release properties. Owning to crosslinkage and decrosslinkage of coumarin unit in PDMV under different ultraviolet (UV) irradiations, the polymeric chains substantially acted as on-off gate of MSNs to control the transport channel in mesoporous silica shell. The pyrene encapsulation percentage (31.6%) of MSNs-g-PDMV under the irradiation at 365 nm was only half of that under dark condition (60.3%). Cumulative release efficiency under the irradiation at 365 nm was obviously lower than that at 254 nm at the same temperature. In addition, thermal-responsive property of PDMV offered polymeric MSNs temperature sensitivity. Compared with pyrene-releasing experiment at 25 °C, a moderate drop in release efficiency occurred at 45 °C regardless of 254 nm or 365 nm UV irradiation.

Investigations of benzo[a]pyrene encapsulation and Fenton degradation by starch nanoparticles

Starch nanoparticles were produced by dialysis method from octenyl succinic anhydre (OSA) and 1,4-butane sultone (BS). The properties of the self-assembled nanoparticles were characterized by NMR spectroscopy (DOSY), fluorescence spectroscopy and dynamic light scattering (DLS). In order to investigate the formation of hydrophobic microdomains, the Nile Red dye was used as a fluorescent probe to evaluate the critical aggregation concentration (CAC) of modified starch in aqueous solution. The results show that the entrapment of the molecular guest was effective and only restricted by the solubility limit of the starch. Then, the modified starch was applied to solubilize benzo[a]pyrene (BaP) in view of degradation by Fenton process. Finally, it has been shown that 95% of BaP was degraded when it was encapsulated in OSA-BS-starch nanoparticles.

Clickable polyurethanes based on s‐triazine ring containing aromatic diisocyanate bearing pendent alkyne group: Synthesis and postmodification

ABSTRACTA new s‐triazine ring containing aromatic diisocyanate bearing a pendent alkyne group, namely, 2,4‐bis(4‐isocyanatophenoxy)−6‐(prop‐2‐yn‐1‐yloxy)−1,3,5‐triazine was synthesized and reacted with various diols viz., 1,10‐decanediol, tetraethylene glycol and polyethylene glycols in the presence of dibutyltin dilaurate as the catalyst to obtain a series of linear polyurethanes. The selected polyurethanes possessing pendent alkyne groups were postmodified with chemically diverse azides viz., 1‐(azidomethyl)benzene, 1‐(azidomethyl)pyrene, and methoxy end‐caped poly(ethylene glycol) azide via copper‐catalysed azide‐alkyne Huisgen 1,3‐dipolar cycloaddition. FTIR and 1H NMR spectra indicated quantitative click reaction. UV–vis and fluorescence spectroscopic analysis confirmed complete incorporation of pyrenyl groups indicating the formation of fluorescence active polyurethane by postmodification with 1‐(azidomethyl)pyrene. TG analysis of polyurethanes indicated two stage weight loss and their thermal stability, as judged by T10 values, was governed by weight percent of urethane linkages. The water contact angle measurements revealed improved wettability with increased content of PEG either in the backbone of polyurethanes or as grafted chains. DLS and TEM studies confirmed that certain polyurethanes possessing PEG segments displayed self‐assembly in aqueous solution, which was further supported by pyrene encapsulation studies using UV–vis spectroscopy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1008–1020

Preparation of calcium carbonate microparticles containing organic fluorescent molecules from vaterite

The encapsulation of fluorescent organic molecules into crystalline calcium carbonate was examined using calcium carbonate microcapsule, whose crystalline phase is vaterite as a metastable phase of calcium carbonate. A calcium carbonate microcapsule with impregnated pyrene that is a water insoluble fluorescent molecule was soaked into suitable aqueous solutions to promote the phase transition of vaterite toward calcite as the stable phase of calcium carbonate. When 0.2M calcium chloride solution was used, the largest amount of pyrene (approximately 0.06wt%) was encapsulated into the calcite particle. Pyrene thus included was not eliminated even after thorough washing with THF. The calcite particle thus prepared produced the excimer emission of pyrene by UV irradiation. Rhodamine B was also introduced into calcium carbonate by the immersion of the microcapsule into the aqueous solutions of Rhodamine B. The fluorescence of rhodamine B was observed from the calcium carbonate particles by visible light irradiation. Acetaminophen, a common drug poorly soluble in water, was also included in the calcium carbonate particle by the same procedures as the pyrene encapsulation. As acetaminophen thus encapsulated was released by the dissolution of the calcium carbonate particle in acidic solution, the particle is expected to be applied for a dissolution-triggered drug delivery.

Pyrene-Loaded Polypyrrole Microvessels

The encapsulation of guest molecules within polymeric hollow nano- or microscale structures is a rapidly developing field of interdisciplinary research due to a variety of applications ranging from drug delivery and sensor fabrication to nanoscale synthesis and bioinspired mineralization. We report on the encapsulation of pyrene within three-dimensional polypyrrole microvessels synthesized by precipitation polymerization of pyrrole onto toluene droplets that contain pyrene. Steady state and time-resolved fluorescence measurements show that the optical response and dynamics of encapsulated pyrene is significantly different from that in the free solution, likely due to interactions with oligomeric species generated during the polymerization process that partition into the organic core of the microvessel. Our results indicate that the encapsulation process can have a significant influence on the local environment of encapsulated species, an issue that is critical from the perspective of potential synthetic or medical applications.

Efficient Complexation of Pyrrole‐Bridged Dizinc(II) Bisporphyrin with Fluorescent Probe Pyrene: Synthesis, Structure, and Photoinduced Singlet–Singlet Energy Transfer

A diethylpyrrole-bridged dizinc(II) bisporphyrin (Zn(2)DEP) is reported that encapsulates fluorescent probe pyrene molecules through strong π-π interactions, which can relay information about the chemical environment in the interior of the host-guest supramolecular assembly. X-ray structures of both Zn(2)DEP and the encapsulated pyrene complex are reported, which provides a rare opportunity to investigate the structural changes upon guest binding. A comparative structural analysis demonstrated the exceptional ability of this bisporphyrin platform to open its binding pocket for pyrene encapsulation by a vertical displacement of more than 2.45 Å, although both Zn(2)DEP and the pyrene complex have nearly parallel porphyrin ring orientations. The (1)H NMR spectrum of the encapsulated pyrene complex in solution shows the upfield shifts of the pyrene protons due to a strong ring current effect, which demonstrates the retention of the solid-state structure in solution. To further assess the extent to which pyrene guests remain encapsulated in solution, a known fluorescence quencher, dimethylaniline, was added to the host-guest assembly, which shows no exciplex formation for days in nonpolar solvents. Thus, the assembly also retained the structural integrity in solution for a long time. The association constant (K(asso)) for such a complexation process in solution was observed to be 1.78×10(5) M(-2) for 1:2 binding. Steady-state fluorescence and lifetime studies indicate significant photoinduced singlet-singlet energy transformation from the excited state of pyrene to zinc bisporphyrin.

Interfacial Regions Governing Internal Cavities of Dendrimers. Studies of Poly(alkyl aryl ether) Dendrimers Constituted with Linkers of Varying Alkyl Chain Length

This report deals with a study of the properties of internal cavities of dendritic macromolecules that are capable of encapsulating and mediating photoreactions of guest molecules. The internal cavity structures of dendrimers are determined by the interfacial regions between the aqueous exterior and hydrocarbon like interior constituted by the linkers that connect symmetrically sited branch points constituting the dendrimer and head groups that cap the dendrimers. Phloroglucinol-based poly(alkyl aryl ether) dendrimers constituted with a homologous series of alkyl linkers were undertaken for the current study. Twelve dendrimers within first, second, and third generations, having ethyl, n-propyl, n-butyl, and n-pentyl groups as the linkers and hydroxyl groups at peripheries in each generation, were synthesized. Encapsulation of pyrene and coumarins by aqueous basic solutions of dendrimers were monitored by UV-vis and fluorescence spectroscopies, which showed that a lower generation dendrimer with an optimal alkyl linker presented better encapsulation abilities than a higher generation dendrimer. Norrish type I photoreaction of dibenzyl ketone was carried out within the above series of dendrimers to probe their abilities to hold guests and reactive intermediate radical pairs within themselves. The extent of cage effect from the series of third generation dendrimers was observed to be higher with dendrimers having an n-pentyl group as the linker.

Chitosan-coated alginate-polyvinyl alcohol beads for encapsulation of silicone oil containing pyrene: a novel method for biodegradation of polycyclic aromatic hydrocarbons

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are potential hazards in the environment owing to their toxic, carcinogenic and recalcitrant nature. Biodegradation of these compounds, although effective compared with other treatment techniques, is problematic owing to its low aqueous solubility and negligible bioavailability. The present study reports a novel method for biodegradation of PAHs using an encapsulated form of the pollutant in chitosan-coated alginate–polyvinyl alcohol (PVA) beads. RESULTS: A suitable combination of 3% (w/v) PVA, 100 g L−1 non-ionic surfactant Brij 30 and 0.3 silicone oil fraction in the formulation was found to be optimal in the preparation of stable emulsion. The emulsion obtained was admixed with alginate (3% w/v) to prepare suitably sized microspheres by an emulsion gelation technique, which were later coated with chitosan to yield a maximum pyrene encapsulation efficiency of 90.7%. Pyrene in silicone oil at concentration as high as 2 g L−1, when delivered through the chitosan coated alginate–PVA beads, was completely degraded by Mycobacterium frederiksbergense within 10 days without any significant lag phase. CONCLUSION: Using chitosan-coated alginate–PVA beads sustained release of pyrene and subsequent biodegradation by M. frederiksbergense were achieved. Using the present system, complete degradation of pyrene was attained even at its very high initial concentration and within a short time period. Further advantage offered by this system seems to be negligible toxic effect of pyrene and solvents on the degrading microorganisms since these were in an encapsulated form and were not in direct contact with the organism. Copyright © 2010 Society of Chemical Industry

Photo‐Polymerization of Amphiphilic N,O‐diacylated Serine‐Based Monomers in their Micellar States for an Encapsulation

AbstractThe photo‐polymerization of amphiphilic monomers, two isomers of N,O‐diacylated serine (AM and EM), has been studied. Self‐assembling properties of the monomers were characterized in aqueous media by NMR and fluorescence techniques. These data show that both can form micellar structures by forming hydrophobic cores from both of the polymerizable and alkyl groups. Photo‐polymerizations of AM and EM were performed in their micellar and solution states. In the micellar states, polymerizations proceeded rapidly and reached almost complete conversion within 1 h, while those in DMSO solutions did not. Comparing the polymers obtained, we concluded that EM was more useful for further applications mainly because of the solubility of the resulting polymer. Based on DLS data, the resulting EM‐polymer micelle had a diameter of ca. 20 nm, about ten times larger than the original micelle. Furthermore, preliminary experiments indicated that the micellar state polymerization of EM afforded an encapsulation of pyrene in a stable hydrophobic domain.magnified image

Preparation of Liquid-Core Nanocapsules from Poly[(ethylene oxide)-co-glycidol] with Multiple Hydrophobic Linoleates at an Oil−Water Interface and Its Encapsulation of Pyrene

A convenient approach is provided to prepare liquid-core nanocapsules by cross-linking an amphiphilic copolymer at an oil-water interface. The hydrophilic copolymer poly[(ethylene oxide)-co-glycidol] was prepared by anionic polymerization of ethylene oxide and ethoxyethyl glycidyl ether first, then the hydroxyl groups on the backbone were recovered after hydrolysis and partly modified by hydrophobic conjugated linoleic acid. The copolymer with multiple linoleate pendants was absorbed at an oil-water interface and then cross-linked to form stable nanocapsules. The mean diameter of the nanocapsule was below 350 nm, and the size distribution was relatively narrow (<0.2) at low concentrations of oil in acetone (<10 mg/mL). The particle size could be tuned easily by variation of the emulsification conditions. The nanocapsule was stable in water for at least 5 months, and the shell maintained its integrity after removal of the oily core by solvent. Pyrene was encapsulated in these nanocapsules, and a loading efficiency as high as 94% was measured by UV spectroscopy.

Preparation of dye-loaded SiO 2 nanoparticles

A room temperature method for the encapsulation of pyrene in SiO 2 nanoparticles is described. The relation between alkoxysilane surfactant chain length, reactant molar ratios and the uptake of dye, sample morphology, photophysical properties, and the ability of the silicate matrix to protect the encapsulated dye was examined. The synthesis can easily be adapted for the encapsulation of other hydrophobic and thermolabile substances, and used in the development of nanostructured optically active coatings, films and monoliths.

Polycaprolactone‐b‐Poly(ethylene oxide) Biocompatible Micelles as Drug Delivery Nanocarriers: Dynamic Light Scattering and Fluorescence Experiments

AbstractSummary: Dynamic light scattering (DLS) and fluorescence experiments were carried out to study PCL44‐b‐PEO114 biocompatible micelles used as nanocarriers in drug delivery. Micelles prepared by a simple procedure (THF removal under nitrogen flow) exhibited a narrow size distribution with an average diameter of 100 nm. For micelles containing a hydrophobic model compound (pyrene) within the PCL core, a smaller average micellar size of 80 nm was observed, with a simultaneous broadening in the size distribution profile. In parallel to DLS results, fluorescence experiments showed evidence of pyrene encapsulation, and that the onset of the micellization process occurs at approximately 10/90 (v/v) THF/water mixtures in the case of PCL44‐b‐PEO114 polymer.

Self-assembled methanofullerene vesicles and their encapsulation of pyrene

Fullerene vesicles were fabricated from a neutral methanofullerene derivative with hydrophobic–hydrophobic–hydrophilic structure (TDC 60). For the first time, a water-insoluble organic molecule of pyrene was encapsulated into the vesicles and resulted in novel organic core-shell suprastructure and the photophysical properties were researched systemically.

Encapsulation of pyrene within self-assembled peptide amphiphile nanofibers

Certain peptide amphiphiles (PAs) in aqueous media are known to form high-aspect-ratio cylindrical nanofibers with hydrophobic cores. Using cholesterol or palmitic acid as the hydrophobe and the biological adhesion epitope RGDS as the hydrophilic segment, we studied the encapsulation of pyrene, a small hydrophobic molecule, within the cores of the self-assembling PA nanofibers. Circular dichroism (CD), transmission electron microscopy (TEM) and fluorescence were used to characterize formation of the supramolecular structures. Pyrene excimer formation observed by fluorescence demonstrated the encapsulation and aggregation of pyrene within the hydrophobic cores. In addition, peptide amphiphiles covalently functionalized with pyrene linked to the hydrophobic portion of the molecule exhibited excimer formation upon self-assembly into nanofibers. Interestingly excimer formation was not observed in similar molecules that formed spherical aggregates rather than cylindrical nanofibers.

Synthesis and characterization of amphiphilic poly(ethylene glycol) graft copolymers and their potential application as drug carriers

Amphiphilic graft copolymers comprising monomeric units of stearyl methacrylate, methyl acrylate, acrylic acid and poly(ethylene glycol) acrylate were synthesized and their properties in aqueous systems characterized. The structures of these copolymers were analysed by Fourier transform infra-red and nuclear magnetic resonance spectroscopies while their molecular weights were estimated by static light scattering. The study of critical micelle concentrations and micellar sizes indicated that the formation of micelles is primarily determined by the hydrophobic/hydrophilic properties of these copolymers. Encapsulation of pyrene (as a drug model) into the micelles was found to be dependent on their stearyl methacrylate content. These copolymers also exhibited a sustained release pattern for pyrene in aqueous solutions and might indicate their future applications as potential drug delivery systems.