Sorption and regeneration performance of novel solid desiccant based on PVA-LiCl electrospun nanofibrous membrane

Electrospun PVA (polyvinyl alcohol)-LiCl composite membranes were prepared as novel solid desiccants. Experimental results show that nanofibrous membranes (NFMs) exhibit notable advantages in sorption capacity, sorption rate and low-temperature desorption rate, as compared with the solution-cast PVA-LiCl membranes (SCMs). The PVA NFM with 15 wt% LiCl can sorb 1.04 g g⁻¹ water at 25 °C and 90% relative humidity (RH), which is more than twice of the reported capacity of silica gel. Due to the nano-structure and small diffusion distance, the desiccant membranes have fast sorption and desorption rates. The desorption isobars show that about 90% of the sorbed moisture can be removed at temperatures between 40 °C and 60 °C, which makes it promising to utilize solar energy or exhaust heat for air dehumidification. The composite desiccant membranes can also be recycled without the degradation of sorption and desorption performance.     

一种具有快速响应特性的光导纤维铁传感器

将邻氨基苯甲酸共价偶联到聚乙烯醇基质上,制得一个基于荧光碰撞猝灭机理的测定Fe^3^+的光导纤维化学传感器。此传感器响应速度仅为90ms,且可逆性好。用它测定铝合金中的铁含量,取得满意的结果。     

A Zn2+-specific turn-on fluorescent probe for ratiometric sensing of pyrophosphate in both water and blood serum

A novel fluorescent sensor composed of a naphthalene functionalized tetraazamacrocycle ligand 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3-methyl naphthalene (1) and Zn(2+) has been designed and prepared, which can be utilized for selective and ratiometric sensing of pyrophosphate (PPi) over other phosphate-containing anions in aqueous solution at physiological pH. Notably, the water soluble 1 itself also exhibits a selective enhanced fluorescent response to Zn(2+), and the complex 1-Zn(2+) thus formed eventually fulfils the synergic Zn(2+) coordination-altered strategy with PPi. Furthermore, the ratiometric sensing of 1-Zn(2+) towards PPi performed well even in blood serum milieu. Finally, the sensor 1-Zn(2+) was successfully employed to monitor a real-time assay of inorganic pyrophosphatase (PPase) by means of ratiometric fluorescent measurements for the first time.     

Polydopamine- and polyDOPA-coated electrospun poly(vinyl alcohol) nanofibrous membranes for cationic dye removal

Mussel adhesive proteins including special functional groups, such as dopamine and 3,4-dihydroxy-l-phenylalanine (DOPA), exhibit strong adhesion and have thus been used in numerous applications. As a novel dye adsorbent for wastewater treatment, this study examineed poly(vinyl alcohol) (PVA) nanofibrous membranes (NFMs) fabricated via electrospinning and then coated with polydopamine (pDA) or polyDOPA through a simple dip coating process in dopamine or DOPA solution to examine. The surface morphology, chemical composition and hydrophilicty of PVA NFMs coated with pDA or polyDOPA were compared using scanning electron microscopy (SEM), UV photoelectron spectrometry (XPS) and contact angle analyzer, respectively. The thermal degradation temperatures of the PVA NFMs were increased significantly by about 100 °C due to the radical scavenging ability of pDA and pDOPA. Also, the differences in the adsorption performance toward a cationic dye, methylene blue (MB), for polydopamine- or polyDOPA-coated PVA NFMs were evaluated using a UV–Visible spectrophotometer. Finally, a recyclability test was conducted to confirm the applicability as a dye adsorbent.     

1-Naphthol as an excited state proton transfer fluorescent probe for sensing bound-water hydration of polyvinyl alcohol

When 1-naphthol incorporated polyvinyl alcohol (PVA) films are allowed to swell in water, there is a loss of fluorescence intensity of the neutral form with a concomitant increase of the anionic form fluorescence intensity. This fluorescence response due to the excited state prototropism (ESPT) of 1-naphthol is very sensitive to the initial stage of hydration of the PVA. Using an existing model of hydrogel swelling and DSC experiments, it was reasoned that 1-naphthol senses the bound-water component of PVA hydration. Thus, 1-naphthol is proposed as an ESPT fluorescent sensor for the specific sensing of bound-water hydration of PVA hydrogel.     

Recent Progress in Fabrication of Electrospun Nanofiber Membranes for Developing Physiological In Vitro Organ/Tissue Models

Nanofiber membranes (NFMs), which have an extracellular matrix-mimicking structure and unique physical properties, have garnered great attention as biomimetic materials for developing physiologically relevant in vitro organ/tissue models. Recent progress in NFM fabrication techniques immensely contributes to the development of NFM-based cell culture platforms for constructing physiological organ/tissue models. However, despite the significance of the NFM fabrication technique, an in-depth discussion of the fabrication technique and its future aspect is insufficient. This review provides an overview of the current state-of-the-art of NFM fabrication techniques from electrospinning techniques to postprocessing techniques for the fabrication of various types of NFM-based cell culture platforms. Moreover, the advantages of the NFM-based culture platforms in the construction of organ/tissue models are discussed especially for tissue barrier models, spheroids/organoids, and biomimetic organ/tissue constructs. Finally, the review concludes with perspectives on challenges and future directions for fabrication and utilization of NFMs.     

Kinetic modeling of novel solid desiccant based on PVA-LiCl electrospun nanofibrous membrane

A new polymer-based composite desiccant, Polyvinyl alcohol-LiCl nanofibrous membrane (PVA-LiCl NFM), has been prepared by the electrospinning technique. The newly-developed desiccant membrane not only has large moisture adsorption capacity, fast moisture adsorption rate and favorable stability, but also is featured by its low regeneration temperature. In this work, adsorption and desorption kinetic models are explored for PVA-LiCl NFMs, which include the pseudo-first and the pseudo-second order model based on the rate law and a diffusion model based on the Fick's law. The results indicate that the moisture adsorption and desorption kinetics of the PVA-LiCl NFMs follow the pseudo-second-order law very well. As the key parameters in the diffusion model, the equilibrium adsorption capacity and the diffusion coefficient are focused on, and they can be well determined by the Brunauer–Emmett–Teller (BET) model and the radial-basis-functions artificial neural network (RBFANN) model, respectively. Finally, the adsorption and desorption activation energy of the PVA-LiCl NFM with a 0.15 mass ratio of LiCl to PVA are recognized as 24.36 and 26.52 kJ/mol, respectively. The work is of great importance to the better application of the newly-developed desiccant material (PVA-LiCl NFM).     

A versatile water soluble fluorescent probe for ratiometric sensing of Hg2+ and bovine serum albumin

A novel tetraazamacrocycle fluorescent sensor (6-(1-(dimethylamino)-5-naphthalene sulfonyl)-3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene, 1) has been designed and prepared, which can be utilized for selective and ratiometric sensing of Hg(2+) and bovine serum albumin (BSA) with two different responsive modes in aqueous solution at physiological pH (50 mM Tris-HCl, pH 7.6). Above 0.5 ppb Hg(2+) can be discerned by coordination with 1 and the emission color changes enable 1 to be applied to a fast Hg(2+) test paper assay. Sensor 1 has also been demonstrated to be easily cell-penetrable and applicable for Hg(2+) imaging in living cells. Imaging of BSA in the gel using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) stained in the medium containing 1 verified that the binding of 1 and BSA was successful in the presence of nonprotein substances. The linear range of 1 towards BSA utilizing ratiometric fluorescent calibration via noncovalent interaction in solution is 0-100 μg mL(-1) with a detection limit of 1 μg mL(-1), and has been successfully employed to determine the albumin concentration in blood serum by means of ratiometric fluorescent measurements for the first time. Finally, sensor 1 behaves as a fluorescent molecular switch composed of triple logic gates upon chemical inputs of Hg(2+) and BSA, which potentially provides intelligent diagnostics for Hg(2+) contaminated serum on the nanoscale.     

Fiber optic sodium and potassium sensing by using a newly synthesized squaraine dye in PVC matrix

In recent years squarines received attention as fluorescent labels. Their very promising spectral properties such as long wavelength absorption and emission, high extinction coefficients and quantum yields could lead novel sensing technologies. In this work newly synthesized fluoroinophores named bis[4-N-(1-aza-4,7,10,13-tetraoxacyclopentadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-1 and 2 bis[4-N-(1-aza-4,7,10,13,16-pentaoxacyclooctadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-2 have been used for sodium and potassium sensing in plasticized PVC matrix. The squaraine derivatives exhibited fluorescence emission based optical responses to sodium and potassium with a detection limit of 1.10(-9) M. The sensor compositions exhibited wide response ranges between 10(-9) and 10(-5) M Na(+)or K(+), and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2-7.3. Throughout fiber optic based studies a relative signal change of 54-56% has been achieved. The azacrown dyes have the advantage that they can be excited with long wavelength light and, are, therefore, LED compatible. The cross sensitivity of azacrown-1 and -2 to Ba(2+), Ca(2+) and NH(4)(+)were also tested in separate solutions.     

A highly selective and sensitive in vivo fluorosensor for zinc(II) without cytotoxicity

A highly selective and sensitive fluorescent Zn(2+) sensor, 2,6-bis(2-hydroxy-benzoic acid hydrazide)-4-methylphenol (1), was designed and synthesized. In aqueous THF (4 : 6 v/v) ligand 1 induces a 2 : 1 complex formation with respect to Zn(2+) at physiological pH. This probe features visible light excitation(390 nm) and emission (490 nm) profiles, excellent selectivity responses for Zn(2+)over other competing biological metal ions with K(d) < 1 pM(2), LOD < 1 ng L(-1) and about 680 fold enhancement in fluorescent intensity upon Zn(2+) binding. It also exhibits cell permeability and intracellular Zn(2+) sensing in A375 human melanoma cancer cell.     

Synthesis and characterization of a sensitive and selective Fe3+ fluorescent sensor based on novel sulfonated calix[4]arene‐based host‐guest complex

A novel fluorescent sensor was prepared from sulfonated calix[4]arene (SC4A) by the host-guest complexation method using the fluorescent dye rhodamine B (RB) as a structure-directing agent. The crystal structure of the host-guest complex (RB@(SC4A)₃) was confirmed by X-ray diffraction studies while its performance and sensing mechanism for metal ion pollutants were characterized using fluorescence and nuclear magnetic resonance spectroscopies. The results showed that RB@(SC4A)₃ had a triangular branch structure resulting from host-guest mediation of the interactions between the three SC4A host molecules and the three terminal groups of the guest molecule RB. The host-guest complex exhibited sensitive and selective sensing towards Fe³⁺ ions via a fluorescence quenching mechanism. The results indicated that RB@(SC4A)₃ could be a promising sensitive and selective fluorescent sensor for metal ion pollutants monitoring. It also provided new insights into the synthesis of calixarene-based host-guest complex.     

Fluorescent Optosensor for Humidity Measurements in Air

A fiber‐optic sensor for relative‐humidity (RH) monitoring in environmental samples is described based on the adiabatic photoreaction that produces an intramolecular charge‐transfer excited state, which is the basis of the sensor response. The sensitive membranes are obtained immobilizing a highly fluorescent dye, 4‐[2‐(pyrazin‐2‐yl)‐1,3‐oxazol‐5‐yl]benzenamine (pzoxba; formerly called appzox), in hydroxypropylcellulose (HPC). The composition of the sensing films was optimized to a final ratio pzoxba/HPC of 1.8⋅10⁻⁵ mol g⁻¹ with a 100‐μm membrane thickness. The optode response spans from 1.68 to 100% RH, with a detection limit of 0.56% (Table 2). Typical response times (t₉₀) to 0 – 100% relative humidity are 1 – 2 min, the relative standard deviation for repeated measurements being 0.77 – 1.8%. The optode is insensitive to typical organic vapor interferents of commercial capacitive sensors (see Table 3) as well as to molecular oxygen, an important quencher of other luminescence‐based optical sensors. The proposed optode was successfully applied and validated for continuous monitoring of the relative humidity level in environmental samples.     

Different PES nanofibrous membrane parameters effect on the efficacy of immunoassay performance

The contribution of electrospun nanofibrous membranes (e.NFMs) in the biosensing platforms opens up a new prospect for the invention of faster and more sensitive analytical devices. In this paper, we utilized e.NFM of polyethersulfone (PES) as a solid substrate for the protein immobilization through two different approaches: physical and covalent. Scanning electron microscopy (SEM) and Fourier‐transform‐infrared (FTIR) tests were performed to study the effect of plasma treatment on protein immobilization efficacy. Moreover, taking advantage of ELISA technique, the influence of different parameters, namely, nanofibers diameter, membrane thickness, plasma treatment time, an incubation time of ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide/N‐hydroxysuccinimide (EDC/NHS), and their ratio on antibody immobilization efficacy through two mentioned approaches, was also assessed.     

A coumarin derivative covalently immobilized on sensing membrane as a fluorescent carrier for nitrofurazone

A coumarin derivative 4-methyl-8-methylacrylamide-2H, 5H-pyrano [3, 2-C] benzpyran 2, 5-dione (MMPBD) has been synthesized as a fluorescent carrier for preparing an optical chemical sensor. The carrier is immobilized on a quartz glass plate surface treated with a silanizing agent to prevent the leakage of the dye. This MMPBD sensor can be utilized for a nitrofurazone (NF) assay based on fluorescence quenching. The sensor shows good repeatability, a long lifetime and a fast response of less then 50 s. NF can be determined in the range between 1.0x10(-6)-1.0x10(-3 )mol L(-1) with a detection limit of 8.0x10(-7) mol L(-1 )at pH 7.0.     

Full-range optical pH sensor based on imaging techniques

A new colour-based disposable sensor array for a full pH range (0-14) is described. The pH sensing elements are a set of different pH indicators immobilized in plasticized polymeric membranes working by ion-exchange or co-extraction. The colour changes of the 11 elements of the optical array are obtained from a commercial scanner using the hue or H component of the hue, saturation, value (HSV) colour space, which provides a robust and precise parameter, as the analytical parameter. Three different approaches for pH prediction from the hue H of the array of sensing elements previously equilibrated with an unknown solution were studied: Linear model, Sigmoid competition model and Sigmoid surface model providing mean square errors (MSE) of 0.1115, 0.0751 and 0.2663, respectively, in the full-range studied (0-14). The performance of the optical disposable sensor was tested for pH measurement, validating the results against a potentiometric reference procedure. The proposed method is quick, inexpensive, selective and sensitive and produces results similar to other more complex optical approaches for broad pH sensing.     

Creation of Chitosan-Based Nanocapsule-in-Nanofiber Structures for Hydrophobic/Hydrophilic Drug Co-Delivery and Their Dressing Applications in Diabetic Wounds

Nanofiber meshes (NFMs) loaded with therapeutic agents are very often employed to treat hard-to-heal wounds such as diabetic wounds. However, most of the NFMs have limited capability to load multiple or hydrophilicity distinctive-therapeutic agents. The therapy strategy is therefore significantly hampered. To tackle the innate drawback associated with the drug loading versatility, a chitosan-based nanocapsule-in-nanofiber (NC-in-NF) structural NFM system is developed for simultaneous loading of hydrophobic and hydrophilic drugs. Oleic acid-modified chitosan is first converted into NCs by the developed mini-emulsion interfacial cross-linking procedure, followed by loading a hydrophobic anti-inflammatory agent Curcumin (Cur) into the NCs. Sequentially, the Cur-loaded NCs are successfully introduced into reductant-responsive maleoyl functional chitosan/polyvinyl alcohol NFMs containing a hydrophilic antibiotic Tetracycline hydrochloride. Having a co-loading capability for hydrophilicity distinctive agents, biocompatibility, and a controlled release property, the resulting NFMs have demonstrated the efficacy on promoting wound healing either in normal or diabetic rats.     

间苯二酚杯[4]芳烃为涂层的压电石英传感器测定液相多巴胺

研究了以间苯二酚杯[4]芳烃为敏感涂层的石英压电晶体（PQC）传感器,在中 性磷酸盐缓冲液体系中对神经传递质多巴胺和抗坏血酸的响应,发现间苯二酚杯 [4]芳烃对多能上能下胺有很好的响应选择性,这归因于间苯二酚杯[4]芳烃与多巴 胺分子结构相匹配,形成主客体超分子体系。以间苯二酚杯[4]芳烃为涂层的POC传 感器对液相中多巴胺具有响应快、重现性好、灵敏度高的特点,线性响应范围为3. 5-500 μg/g。     

A fluorescent probe for both pH and Zn2+ based on 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenol

A sensitive fluorescent probe 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenol (HBIZ) for pH and Zn2+ has been developed. Great changes have taken place in the UV-vis absorption and fluorescence spectra for HBIZ upon increasing pH of its aqueous solution, acting as a pH-induced emission "off-on-off" switch with large enhancement factors of ～290 and ～75 over the pH range of 1.00-5.40 and 5.20-10.40. A over 100-fold fluorescence enhancement was also observed after complexation of HBIZ to Zn2+ in N,N-dimethylformamide.     

Triazole-linked-thiophene conjugate of calix[4]arene: its selective recognition of Zn2+ and as biomimetic model in supporting the events of the metal detoxification and oxidative stress involving metallothionein

Supramolecular calix[4]arene conjugate (L) has been developed as a sensitive and selective sensor for Zn(2+) in HEPES buffer among the 12 metal ion by using fluorescence, absorption and ESI MS and also by visual fluorescent color. The structural, electronic, and emission properties of the calix[4]arene conjugates L and its zinc complex, [ZnL], have been demonstrated using ab initio density functional theory (DFT) combined with time-dependent density functional theory (TDDFT) calculations. The TDDFT calculations reveal the switch on fluorescence behavior of L is mainly due to the utilization of the lone pair of electrons on imine moiety by the Zn(2+). The resultant fluorescent complex, [ZnL], has been used as a secondary sensing chemo-ensemble for the detection of -SH containing molecules by removing Zn(2+) from [ZnL] and forming {Cys/DTT·Zn} adducts as equivalent to those present in metallothioneins. The displacement followed by the release of the coordinated zinc from its Cys/DTT complex by heavy metal ion (viz. Cd(2+) and Hg(2+)), as in the metal detoxification process or by ROS (such as H(2)O(2)) as in the oxidative stress, has been well demonstrated using the conjugate L through the fluorescence intensity retrieval wherein the fluorescence intensity is the same as that observed with [ZnL], which in turn mimics the zinc sensing element (MTF) in biology.     

9-(cycloheptatrienylidene)-fluorene derivative: remarkable ratiometric pH sensor and computing switch with NOR logic gate

2,7-Bis(4-dimethylaminophenyl)-9-(cycloheptatrienylidene)fluorene (1) was synthesized and characterized. 1 could be used as a fluorescent sensor either for pH or for pyridinium halide. Integrated with the ratiometric method and an NOR logic gate, a tunable two-input/multi-output system was presented on the basis of this single molecule. [structure: see text]