Fluorescent Dye Rhodamine Research Articles

Agarose-based microwell array chip for high-throughput screening of functional microorganisms

Natural bacterial communities provide a rich source of biocatalysts, however, high-throughput screening for the functional bacteria remains a major challenge. Here, we present an agarose-based microwells array chip for functionally screening and isolating novel microorganisms with merits of high-throughput, high specificity and sensitivity. In this approach, the bacterial cells were loaded with single cell per a microwell mode and were incubated in the arrayed agarose microwells. The growths of single cells were then monitored in real time and the enzyme reaction activities were assessed at the individual microwell resolution. To validate the reliability of the method, we subsequently applied it to screen lipase-producing bacteria from the pond water based on lipase hydrolysis of the substrate in the presence of a fluorescent dye (rhodamine B), which emitted yellow-orange fluorescent halos upon UV-light irradiation. A total amount of more than 310,000 isolates from pond water could be screened at a time in only 13 h with reduced consumption of reagents. As a result, 12 microcolonies were identified out with the desired phenotype, in which two new species were discovered based on 16S rRNA sequencing. We expect the developed method to be potentially useful to high-throughput analysis, microbiology and synthetic biology.

Femtosecond stimulated Raman line shapes: Dependence on resonance conditions of pump and probe pulses

Resonance enhancement has been increasingly employed in the emergent femtosecond stimulated Raman spectroscopy (FSRS) to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint efforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. During spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Raman pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodamine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by different resonance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence (HL) pathways. Meanwhile, on-resonance conditions of the Raman pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.

Enhanced fluorescence for in situ temperature mapping of photothermally heated aluminum nanoparticles enabled by a plasmonic grating substrate

In situ dynamic temperature mapping of photothermally heated aluminum nanoparticles (Al NPs) embedded in a fluoropolymer (THV) is achieved using fluorescent dye (rhodamine 6G). A plasmonic grating substrate enhances the dye fluorescence intensity by a factor of seven over a glass substrate, to enable image capture rates of 500 frames per second. Further, the fluorescence intensity is linearly related to temperature and reversible. Photothermal heating of embedded Al NPs using a 2380 W cm−2 incident flux produced an Al NP heating rate of 1.2 × 104 °C s−1. Localized Al NP motion was also observed and attributed to thermal expansion and melting of the polymer. Multiphysics simulation provided agreement with experimental observations, bolstering confidence in the technique. The plasmonic grating platforms were shown to significantly improve both fluorescence intensity and the photothermal heating of Al compared to glass substrates, opening a new path for fast and high-resolution in situ temperature mapping.

Phosphatidylserine decarboxylase governs plasma membrane fluidity and impacts drug susceptibilities of Candida albicans cells

Plasma membrane (PM) lipid composition imbalances affect drug susceptibilities of the human pathogen Candida albicans. The PM fundamental structure is made up of phospholipid bilayer where phosphatidylethanolamine (PE) contributes as second major phospholipid moieties, which is asymmetrically distributed between the two leaflets of the bilayer. PSD1 and PSD2 genes encode phosphatidylserine decarboxylase which converts phosphatidylserine (PS) into PE in C. albicans cells. Genetic manipulation of PSD1 and PSD2 genes is known to impact virulence, cell wall thickness and mitochondrial function in C. albicans. In the present study, we have examined the impact of PSD1 and PSD2 deletion on physiochemical properties of PM. Our fluorescence recovery after photobleaching (FRAP) experiments point that the PM of psd1Δ/Δ psd2Δ/Δ mutant strain displays increased membrane fluidity and reduced PM dipole potential. Further, the result of PSD1 and PSD2 deletion on the thermotropic phase behavior monitored by differential scanning calorimetry (DSC) showed that in comparison to WT, the apparent phase transition temperature is reduced by ~3 °C in the mutant strain. The functional consequence of altered physical state of PM of psd1Δ/Δ psd2Δ/Δ mutant strain was evident from observed high diffusion of fluorescent dye rhodamine 6G and radiolabelled fluconazole (FLC). The higher diffusion of FLC resulted in an increased drug accumulation in psd1Δ/Δ psd2Δ/Δ mutant cells, which was manifested in an increased susceptibility to azoles. To the best of our knowledge, these results constitute the first report on the effect of the levels of phospholipid biosynthesis enzyme on physiochemical properties of membranes and drug susceptibilities of Candida cells.

The effect of nonlocal dielectric response on the surface-enhanced Raman and fluorescence spectra of molecular systems

We present a theoretical study on the influence of the nonlocal dielectric response on surface-enhanced resonant Raman scattering (SERRS) and fluorescence (SEF) spectra of a model molecule confined in the center of a Ag nanoparticle (NP) dimer. In the simulations, the nonlocal dielectric response caused by the electron–hole pair generation in Ag NPs was computed with the d-parameter theory, and the scattering spectra of a model molecule representing the commonly used fluorescent dye rhodamine 6G (R6G) were obtained by density-matrix calculations. The influence of the separation between Ag NP dimers on the damping rate and scattering spectra with and without the nonlocal response were systematically analyzed. The results show that the nonlocal dielectric response is very sensitive to the gap distance of the NP dimers, and it undergoes much faster decay with the increase of the separation than the radiative and energy transfer rates. The Raman and fluorescence peaks as simulated with the nonlocal dielectric response are relative weaker than that without the nonlocal effect for smaller NP separations because the extra decay rates of the nonlocal effect could reduce both the population of the excited state and the interband coherence between the ground and excited states. Our result also indicates that the nonlocal effect is more prominent on the SEF process than the SERRS process.

Synthesis and characterization of well-defined poly(2-deoxy-2-methacrylamido-d-glucose) and its biopotential block copolymers via RAFT and ROP polymerization

Well-defined homopolymers of 2-deoxy-2-methacrylamido-d-glucose (MAG) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using 4-cyanopentanoic acid-4-dithiobenzoate as chain transfer agent (CTA) and 2,2′-azobisisobutyronitrile (AIBN) as initiator. The effect of polymerization conditions such as molar ratio of RAFT agent to initiator and monomer to RAFT agent on conversion and molecular mass characteristics of prepared polymers was estimated. Kinetics of the polymerization under various reaction conditions was studied as a function of time and conversion using in situ1H NMR spectroscopy. The living character of polymerization was demonstrated by carriyng out the further chain extension experiments using isolated PMAG-CTA as a macroRAFT agent. For that, the PMAG with higher molecular weight, as well as block copolymer with acrylic acid were synthesized and characterized using 1H NMR and SEC analysis. A novel amphiphilic copolymer representing a hybrid of glycopolymer and polypeptide fragments was synthesized using RAFT and ring-opening polymerization (ROP). In this case, dithiobenzoate end-group of PMAG was transformed via simultaneous reduction and in situ thiol capping reaction by cysteamine hydrochloride into amino functionality suitable for polymerization of N-carboxyanhydrides (NCA). Two block copolymers of MAG with poly-l-phenylalanine (PPhe) differed with hydrophobic block length were synthesized, characterized and used for preparation of particles via copolymer self-assembly. The hydrodynamic diameter, morphology and cytotoxicity of polymer particles based on PMAG-b-PPhe were evaluated using DLS, TEM and MTT-assay, respectively. Moreover, the encapsulation of model compound (fluorescent dye rhodamine 6G) inside PMAG-b-PPhe micelles, as well as its release, were also tested.

Microvascular permeability of skeletal muscle after eccentric contraction-induced muscle injury: in vivo imaging using two-photon laser scanning microscopy.

Via modulation of endothelial integrity and vascular permeability in response to damage, skeletal muscle microvessels play a crucial permissive role in tissue leukocyte invasion. However, direct visual evidence of altered microvascular permeability of skeletal muscle has not been technically feasible, impairing mechanistic understanding of these responses. Two-photon laser scanning microscopy (TPLSM) allows three-dimensional in vivo imaging of skeletal muscle microcirculation. We hypothesized that the regulation of microvascular permeability in vivo is temporally related to acute inflammatory and regenerative processes following muscle injury. To test our hypothesis, tibialis anterior muscles of anesthetized male Wistar rats were subjected to eccentric contractions (ECCs) via electrical stimulation. The skeletal muscle microcirculation was imaged by an intravenously infused fluorescent dye (rhodamine B isothiocyanate-dextran) to assess microvascular permeability via TPLSM 1, 3, and 7 days after ECC. Immunohistochemistry on serial muscle sections was performed to determine the proportion of VEGF-A-positive muscle fibers in the damaged muscle. Compared with control rats, the volumetrically determined interstitial leakage of fluorescent dye (5.1 ± 1.4, 5.3 ± 1.2 vs. 0.51 ± 0.14 μm3 × 106; P < 0.05, days 1 and 3, respectively, vs. control) and percentage of VEGF-A-positive fibers in the damaged muscle (10 ± 0.4%, 22 ± 1.1% vs. 0%; days 1 and 3, respectively, vs. control) were significantly higher on days 1 and 3 after ECC. The interstitial leakage volume returned to control by day 7. These results suggest that microvascular hyperpermeability assessed by in vivo TPLSM imaging is associated with ECC-induced muscle damage and increased VEGF expression. NEW & NOTEWORTHY This investigation employed a novel in vivo imaging technique for skeletal muscle microcirculation using two-photon laser scanning microscopy that enabled microvascular permeability to be assessed by four-dimensional image analysis. By combining in vivo imaging and histological analysis, we found the temporal profile of microvascular hyperpermeability to be related to that of eccentric contraction-induced skeletal muscle injury and pronounced novel myocyte VEGF expression.

Skeletal Muscle Microvascular Permeability After Eccentric Contraction-Induced Muscle Injury

Within injured skeletal muscle the capillary bed plays a crucial role in leukocyte invasion through modulations of the endothelial integrity, associated with increased permeability. However, direct observation of altered microvascular permeability and compromised capillary integrity has not been technically feasible. Two-photon laser scanning microscopy (TPLSM) allows three-dimensional in vivo imaging which, given the depth of penetration and high resolution of TPLSM, will facilitate measurement of microvascular leakage. PURPOSE: We hypothesized that the regulation of capillary permeability in vivo, as assessed by real-time TPLSM, is temporally related to acute inflammatory and regenerative processes following muscle injury. METHODS: Tibialis anterior muscles of anesthetized male Wistar rats (n=57) were subjected to eccentric contractions (ECC) via electrical stimulation. The skeletal muscle microcirculation was imaged by an intravenously infused fluorescent dye (rhodamine b isothiocyanate dextran, molecular weight 70,000 Daltons) to assess microvascular permeability via TPLSM 1, 3 and 7 days after ECC. Immunohistochemistry on serial muscle sections was performed to determine the percentage of VEGF-A positive muscle fibers in the damaged muscle. RESULTS: Compared with non-ECC control, the volumetrically-determined interstitial leakage of fluorescent dye had increased significantly on days 1 and 3 post-ECC (5.1±1.4, 5.3±1.2 vs. 0.51±0.14 μm3x106, P<0.05 respectively days 1 and 3 vs. control). However, by post-ECC day 7 interstitial leakage had returned to control values. Damaged muscle fibers were evident on days 1 and 3 (% damaged muscle fiber: 11.7±4.7, 48.4±12.4% vs. 0% P<0.05 respectively days 1 and 3 vs. control). Percentage of VEGF-A positive muscle fiber in damaged muscle fiber was significantly higher on days 1 and 3 compared to control (24.9±9.8, 39.3±16.7 vs. 0%, P<0.05 respectively days 1 and 3 vs. control). Regenerated skeletal muscle fibers were found only at 7 days post- ECC. CONCLUSION:In vivo TPLSM imaging represents a powerful investigative technique for skeletal muscle microcirculatory research. Microvascular hyperpermeability is associated with ECC-induced muscle damage and increased VEGF expression.

In situ temperature monitoring in single-molecule FRET experiments.

Thermodynamic properties of single molecules including enthalpic and entropic contributions are often determined from experiments by a direct control and precise measurement of the local temperature. However, common temperature monitoring techniques using, for example, ultrafine temperature probes can lead to uncertainties as the probe cannot be placed in the vicinity of the molecule of interest. Here, we devised an approach to measure the local temperature in freely diffusing confocal single-molecule Förster Resonance Energy Transfer (smFRET) experiments in situ by directly adding the temperature-sensitive fluorescent dye Rhodamine B, whose fluorescence lifetime serves as a probe of the local temperature in the confocal volume. We demonstrate that the temperature and FRET efficiencies of static and dynamic molecules can be extracted within one measurement simultaneously, without the need of a reference chamber. We anticipate this technique to be particularly useful in the physicochemical analyses of temperature-dependent biomolecular processes from single-molecule measurements.

Functional Characterization of ABCC Proteins from Trypanosoma cruzi and Their Involvement with Thiol Transport

Chagas disease is a neglected disease caused by the protozoan Trypanosoma cruzi and affects 8 million people worldwide. The main chemotherapy is based on benznidazole. The efficacy in the treatment depends on factors such as the parasite strain, which may present different sensitivity to treatment. In this context, the expression of ABC transporters has been related to chemotherapy failure. ABC transporters share a well-conserved ABC domain, responsible for ATP binding and hydrolysis, whose the energy released is coupled to transport of molecules through membranes. The most known ABC transporters are ABCB1 and ABCC1, involved in the multidrug resistance phenotype in cancer, given their participation in cellular detoxification. In T. cruzi, 27 ABC genes were identified in the genome. Nonetheless, only four ABC genes were characterized: ABCA3, involved in vesicular trafficking; ABCG1, overexpressed in strains naturally resistant to benznidazole, and P-glycoprotein 1 and 2, whose participation in drug resistance is controversial. Considering P-glycoprotein genes are related to ABCC subfamily in T. cruzi according to the demonstration using BLASTP alignment, we evaluated both ABCB1-like and ABCC-like activities in epimastigote and trypomastigote forms of the Y strain. The transport activities were evaluated by the efflux of the fluorescent dyes Rhodamine 123 and Carboxyfluorescein in a flow cytometer. Results indicated that there was no ABCB1-like activity in both T. cruzi forms. Conversely, results demonstrated ABCC-like activity in both epimastigote and trypomastigote forms of T. cruzi. This activity was inhibited by ABCC transport modulators (probenecid, indomethacin, and MK-571), by ATP-depleting agents (sodium azide and iodoacetic acid) and by the thiol-depleting agent N-ethylmaleimide. Additionally, the presence of ABCC-like activity was supported by direct inhibition of the thiol-conjugated compound efflux with indomethacin, characteristic of ABCC subfamily members. Taken together, the results provide the first description of native ABCC-like activity in T. cruzi epimastigote and trypomastigote forms, indicating that the study of the biological role for that thiol transporter is crucial to reveal new molecular mechanisms for therapeutic approaches in the Chagas disease.

Water absorption through salivary gland type I acini in the blacklegged tick, Ixodes scapularis.

Tick salivary glands play critical roles in maintaining water balance for survival, as they eliminate excess water and ions during blood feeding on hosts. In the long duration of fasting in the off-host period, ticks secrete hygroscopic saliva into the mouth cavity to uptake atmospheric water vapor. Type I acini of tick salivary glands are speculated to be involved in secretion of hygroscopic saliva based on ultrastructure studies. However, we recently proposed that type I acini play a role in resorption of water/ions from the primary saliva produced by other salivary acini (i.e., types II and III) during the tick blood feeding phase. In this study, we tested the function of type I acini in unfed female Ixodes scapularis. The route of ingested water was tracked after forced feeding of water with fluorescent dye rhodamine123. We found that type-I acini of the salivary glands, but not type II and III, are responsible for water uptake. In addition, the ingestion of water through the midgut was also observed. Injection or feeding of ouabain, a Na/K-ATPase inhibitor, suppressed water absorption in type I acini. When I. scapularis was offered a droplet of water, ticks rarely imbibed water directly (5%), while some approached the water droplet to use the high humidity formed in the vicinity of the droplet (23%). We conclude that during both on- and off-host stages, type I acini in salivary glands of female Ixodes scapularis absorb water and ions.

Fabrication of fluorescent dyes supported on porous boron nitride nanosheets and their excellent photoluminescence properties

Fluorescent dyes rhodamine B (RhB) was successfully introduced into the porous boron nitride nanosheets to obtain an effective and rare-earth free light composite conversion materials. X-ray powder diffractions, photoluminescence spectra, etc., were used to investigate the optical performance and thermal stability of these organic-dye-impregnated phosphor composites. The experimental results evidently showed that, compared with the optical properties of RhB in aqueous solution, the composite phosphors possessed more excellent optical performance and higher thermal stability due to their structural defects, surface hydroxyl groups and nanosize pore channel. In addition, the phosphor composites exhibited greatly improved service life and had a broad visible emission wavelengths of 540–680 nm under the 363 nm light excitation. We believe that the reported work should open the way toward the practical application of organic-dye-impregnated phosphor composites in the field of illumination light source.

Novel drug delivery system based on NiCu nanoparticles for targeting various cells

In the past two decades, several novel nanoparticles (NPs) were shown to have great potential to be used as drug delivering systems. This is especially true for superparamagnetic nanoparticles (MNPs), which exhibit their magnetic properties only when there is an influence of external magnetic fields. These have received much attention in the last couple of years due to a relatively simple chemical structure, ease of preparation, possible preparation in various shapes and very small sizes, as well due to their favorable properties in biomedical applications (e.g., biocompatibility). Controlled drug delivery systems have several advantages compared to traditional pharmaceutical formulations. For example, these can enable drug transportation to the desired site of action in the body, through which, its influence on healthy tissues, as well as unwanted effects, can be minimized. Such form of delivery is most important in case of drugs with a very narrow therapeutic index or if the drug itself is a toxic compound as is the case in many antitumor drugs. In this study, we prepared a novel controlled drug delivery formulation using the sol–gel procedure, composed of Ni67.5Cu32.5 MNPs in a silica matrix. As the model drug, we used the fluorescent dye rhodamine 6G (RHO6G) to ease the evaluation of the delivery performance to various human cells (human fibroblast cell line, HeLa cells, and Caco-2 cells). The drug release performance was assessed also using in vitro drug release studies. The combination of different physico-chemical and morphological methods with biocompatibility studies served as a general evaluation of the novel formulations safety and efficiency. Graphical abstract

Enhancing the colloidal stability and surface functionality of molybdenum disulfide (MoS2) nanosheets with hyperbranched polyglycerol for photothermal therapy

Molybdenum disulfide (MoS2) nanosheets are gaining increasing attention due to their attractive properties and myriads of potential applications. However, challenges in the enhancement of their colloidal stability and surface functionality still remain and significantly restrict their practical applications. Herein, we present a viable approach to functionalize MoS2 nanosheets with multihydroxy hyperbranched polyglycerol (HPG) shell by surface-initiated ring-opening polymerization technique. The grafting of HPG from the surface of MoS2 nanosheet yielded MoS2-g-HPG nanohybrid with excellent water dispersibility, good biocompatibility, and greatly enhanced colloidal stability against pH change, ionic strength variation and long-term storage. The MoS2-g-HPG also exhibited excellent light-to-heat conversion capability for in vitro photothermal therapy application. Meanwhile, the MoS2-g-HPG showed favorable surface functionality owing to its numerous surface hydroxyl groups, as demonstrated by the conjugation of functional molecules such as fluorescent dye rhodamine B. As such, this paper opens up new opportunities to empower MoS2 nanosheets and other two-dimensional inorganic nanosheets with desired properties for various applications.

Dual-Emitting Dye@MOF Composite as a Self-Calibrating Sensor for 2,4,6-Trinitrophenol.

An anionic metal-organic framework (MOF) {(NH2Me2)[Zn3(μ3-OH)(tpt)(TZB)3](DMF)12}n (1, tpt = 2,4,6-tri(4-pyridyl)-1,3,5-triazine, H2TZB = 4-(1H-tetrazol-5-yl)benzoic acid and DMF = N,N-dimethylformamide), with both nanosized cages and partitions, has been solvothermally synthesized, which can serve as a crystalline vessel to encapsulate the fluorescent dye rhodamine 6G (Rh6G) via a "bottle around ship" approach. As a result, the obtained dye@MOF composite system features a blue emission of the ligand at 373 nm and a red emission of Rh6G at 570 nm when dispersed in solution, which could be used for decoding the trace amount of 2,4,6-trinitrophenol (TNP) by referring the peak-height ratio of each emission, even in coexistence with other potentially competitive nitroaromatic analytes. Furthermore, the observed fluorescence responses of the composite toward TNP are highly stable and reversible after recycling experiments. To the best of our knowledge, this is the first example of an MOF-implicated self-calibrated sensor for TNP detection.

The design, synthesis and bioimaging of main group elements substituted near-infrared fluorescent rhodamine dyes and probes

Near Infrared (NIR) fluorescence imaging is significant in bioimaging with many favorable characteristics, including high signal/noise ratio, deep penetration and low photo-toxicity. The main group elements substituted rhodamine dyes have attracted large attention not only due to the NIR characteristics, but also many inherited outstanding merits of rhodamine dyes. Among the developed rhodamine dyes, the dyes whose bridging oxygen are substituted by silicon have attracted most interests and been widely used in the fluorescence bioimaging. The development of NIR main group elements substituted rhodamine dyes has enriched the species and quantity of the fluorescent probes and enlarged their application. Herein we reviewed the design, development and application of main group substituted rhodamine in recent years.

Choline taurinate: a new biocompatible amino-functionalized ionic liquid as basic catalyst and extraction solvent

Abstract A new biocompatible amino-functionalized ionic liquid composed solely of biomaterials was synthesized from taurine and choline hydroxide, and its physical properties (density, viscosity, miscibility and thermal stability) were also determined. The classic base-promoted three-component cyclic condensation of aromatic aldehydes, malononitrile and dimedone was chosen as the test reaction to demonstrate the catalytic activity of choline taurinate ([Ch][Tau]). The catalyst could be recovered and reused several times with no significant loss of activity. As a basic ionic liquid, [Ch][Tau] can extract acidic compounds from immiscible solvents through acid-base interaction. The extraction process of fluorescent dye Rhodamine B was monitored using ultraviolet-visible (UV-Vis) spectroscopy, by which the percentage extraction rate was determined as 95%.

On-demand fabrication of surface-enhanced Raman scattering arrays by pen writing, and their application to the determination of melamine in milk

An on-demand, disposable and portable surface-enhanced Raman scattering (SERS) array has been prepared by modifying the surface of cellulose paper and patterning it with silver nanoparticles (AgNPs) via pen-writing technique. The paper is initially modified with hexadecenyl succinic anhydride to generate a hydrophobic top layer that is capable of concentrating melamine (and other hydrophobic analytes) by preventing the mainly aqueous sample from spreading on the paper. The AgNPs are subsequently written onto the hydrophobic paper with a high degree of control to form large-scale SERS sensing arrays. The resulting arrays demonstrate outstanding Raman scattering enhancement as demonstrated for the fluorescent dye Rhodamine 6G which can be detected by SERS with an 80 pM limit of detection (LOD) without interference by fluorescence. The reproducibility in the preparation of spots has a relative standard deviation of <15% (for n = 128 spectra). The arrays were applied to the determination of the illicit milk additive melamine. The plot of SERS intensity at Δν = 681 cm−1 versus the logarithm of melamine concentration is linear in the concentration range from 0.3 to 20 mg·L−1, and the LOD is 0.27 mg·L−1. In our perception, the disposable arrays presented here integrate the advantages of easy production and reliable reproducibility, and therefore are an ideal choice for use in SERS detection.

Polylactic Acid Sealed Polyelectrolyte Multilayer Microchambers for Entrapment of Salts and Small Hydrophilic Molecules Precipitates.

Efficient depot systems for entrapment and storage of small water-soluble molecules are of high demand for wide variety of applications ranging from implant based drug delivery in medicine and catalysis in chemical processes to anticorrosive systems in industry where surface-mediated active component delivery is required on a time and site specific manner. This work reports the fabrication of individually sealed hollow-structured polyelectrolyte multilayer (PEM) microchamber arrays based on layer-by-layer self-assembly as scaffolds and microcontact printing. These PEM chambers are composed out of biocompatible polyelectrolytes and sealed by a monolayer of hydrophobic biocompatible and biodegradable polylactic acid (PLA). Coating the chambers with hydrophobic PLA allows for entrapment of a microair-bubble in each chamber that seals and hence drastically reduces the PEM permeability. PLA@PEM microchambers are proven to enable prolonged subaqueous storage of small hydrophilic salts and molecules such as crystalline NaCl, doxicycline, and fluorescent dye rhodamine B. The presented microchambers are able to entrap air bubbles and demonstrate a novel strategy for entrapment, storage, and protection of micropackaged water-soluble substances in precipitated form. These chambers allow triggered release as demonstrated by ultrasound responsiveness of the chambers. Low-frequency ultrasound exposure is utilized for microchamber opening and payload release.

CH3 NH3 PbBr3 Perovskite Nanocrystals as Efficient Light-Harvesting Antenna for Fluorescence Resonance Energy Transfer.

Hybrid perovskites have created enormous research interest as a low-cost material for high-performance photovoltaic devices, light-emitting diodes, photodetectors, memory devices and sensors. Perovskite materials in nanocrystal form that display intense luminescence due to the quantum confinement effect were found to be particularly suitable for most of these applications. However, the potential use of perovskite nanocrystals as a light-harvesting antenna for possible applications in artificial photosynthesis systems is not yet explored. In the present work, we study the light-harvesting antenna properties of luminescent methylammonium lead bromide (CH3 NH3 PbBr3 )-based perovskite nanocrystals using fluorescent dyes (rhodamine B, rhodamine 101, and nile red) as energy acceptors. Our studies revealed that CH3 NH3 PbBr3 nanocrystals are an excellent light-harvesting antenna, and efficient fluorescence resonance energy transfer occurs from the nanocrystals to fluorescent dyes. Further, the energy transfer efficiency is found to be highly dependent on the number of anchoring groups and binding ability of the dyes to the surface of the nanocrystals. These observations may have significant implications for perovskite-based light-harvesting devices and their possible use in artificial photosynthesis systems.