Fluorescent-based micellar incorporated hydrogel materials for selective determination of long-chain aldehydes.

A highly sensitive micelle-induced sensory has been developed for detection of long-chain aldehydes as potential biomarkers of respiratory cancers. The micelle-like sensor was fabricated through the partial self-assembly of CTAB and S2 surfactants, containing a fluorescent hydrazine-functionalized dye (Naph-NH2). In principle, long-chain aldehydes with amphiphilic character act as the induced-fit surfactants to form well-entrapped micellar particles, as well as react with Naph-NH2 to form hydrazone derivatives resulting in fluorescent enhancement. The limit of detection (LOD) of micellar Naph-NH2/CTAB/S2 platform was calculated to be ∼  64.09-80.98 µM for detection of long-chain aldehydes, which showed fluorescent imaging in lung cancer cells (A549). This micellar sensory probe demonstrated practical applicability for long-chain aldehyde sensing in human blood samples with an accepted percent recovery of ~ 94.02-102.4%. Beyond Naph-NH2/CTAB/S2 sensor, the milcellar hybrid sensor was successfully developed by incorporating a micelle-like platform with supramolecular gel regarding to carboxylate-based gelators (Gel1), which showed a tenfold improvement in sensitivity. Expectedly, the determination of long-chain aldehydes through these sensing platforms holds significant promise for point-of-care cancer diagnosis and therapy.

A fluorescence-based sweat test sensor in a proof-of-concept clinical study for COVID-19 screening diagnosis.

During the corona virus disease 2019 (COVID-19) pandemic period, rapid screening of covid-19 patients has been of great interest by developing a fluorescent sensor for complexation with nonanal, which is a marker for Covid-19 detection in sweat. Solid phase micro-extraction gas chromatography-mass spectrometry (SPME GC-MS) was initially used to quantify nonanal in armpit sweat samples based on an external calibration curve. A sample containing a nonanal content above the threshold of 1.04 µL is expected to be COVID-19 positive with a sensitivity and specificity of 87% and 89%, respectively, validated by comparison with RT-PCR results. For more practical applications, helicene dye-encapsulated ethyl cellulose, namely EC@dyeNH, was applied to screen 140 sweat samples collected from the foreheads of volunteers. The mixed sensor and sweat solution droplets were then visualized and imaged under blacklight. The COVID-19 positive droplets exhibited yellow fluorescence emission, the brightness of which could be measured by using ImageJ in the grey scale. With the optimum color intensity of >73 for positive results, the screening performance was observed with a sensitivity and specificity of 96% and 93%, respectively. The overall test time of this method is approximately less than 15 min. This alternative method offers a promising practical screening approach for the diagnosis of COVID-19 in sweat.

Dual Naked-Eye Optical Sensor Based on Imidazolium Cation and Napthalamide for Specific Detection of Fluoride.

A novel naked eye fluorescence sensor (ANI) based on naphthalimide and imidazolium moieties for fluoride detection has been designed and synthesized by multiple step synthesis. The fluorescence response of ANI sensor was significantly quenched in the presence of fluoride ion upon the interaction between an acidic amide proton and acidic C2 proton (-C(2)H-) of imidazolium compound. The binding behavior of ANI and F- ion was extensively explored by using NMR titration. Comparison of binding ability of ANI and AN sensors addressed the dominant electrostatic and hydrogen bonding interaction with F- ion. Consequently, ANI sensor highlights a strong binding with F- ions with a high selectivity over AN. Interestingly, ANI demonstrated a naked-eye response with colorimetric and fluorometric assay.

Supramolecular self-assembled polymeric nanospheres based on hydrazino naphthalimide functionalised pillar[5]arene for long chain aldehyde detection.

A novel fluorescent sensor HNP5A is constructed consisting of bis-hydrazine naphthalimide decorated pillar[5]arene. Interestingly, this sensor possessed the potential for sensitive and selective detection of long-chain aldehydes, particularly nonanal (C9), and subsequently formed supramolecular pseudorotaxane polymeric nanoparticles inducing a strong fluorescence enhancement. In addition, this as-produced HNP5A⊂C9 exhibited an unexpected reduction of Ag+ to produce AgNPs in an aqueous system and the resulting AgNPs-HNP5A⊂C9 demonstrated a significant fluorescence enhancement under metal-enhanced fluorescence (MEF) behaviour.

Helicene-Hydrazide Encapsulated Ethyl Cellulose as a Potential Fluorescence Sensor for Highly Specific Detection of Nonanal in Aqueous Solutions and a Proof-of-Concept Clinical Study in Lung Fluid.

Over the past years, lung cancer has been one of the vital cancer-related mortalities worldwide and has inevitably exhibited the highest death rate with the subsequent need for facile and convenient diagnosis approaches to identify the severity of cancer. Previous research has reported long-chain aldehyde compounds such as hexanal, heptanal, octanal, and nonanal as potential biomarkers of lung cancer. Herein, the helicene dye-encapsulated ethyl cellulose (EC@dye-NH) nanosensors have been applied for the potentially sensitive and specific detection of long-chain aldehydes in aqueous media. The sensors contain the intrinsic hydrazide group of dye-NH, which is capable of reacting an aldehyde group via imine formation and the EC backbone. This offers the synergistic forces of hydrophobic interactions with alkyl long-chain aldehydes, which could induce self-assembly encapsulation of EC@dye-NH nanosensors and strong fluorescence responses. The addition of long-chain aldehyde would induce the complete micellar-like nanoparticle formation within 15 min in acetate buffer pH 5.0. The limit of detection (LOD) values of EC@dye-NH nanosensors toward heptanal, octanal, and nonanal were 40, 100, and 10 µM, respectively, without interference from the lung fluid matrices and short-chain aldehydes. For practical applicability, this sensing platform was developed for quantification of the long-chain aldehydes in lung fluid samples with 98-101% recoveries. This EC@dye-NH nanosensor was applied to quantify nonanal contents in lung fluid samples. The results of this method based on EC@dye-NH nanosensors were then validated using standard gas chromatography-mass spectrometry (GC-MS), which gave results consistent with the proposed method. With intracellular imaging application, the EC@dye-NH nanosensors demonstrated excellent intracellular uptake and strong green fluorescence emission upon introducing the nonanal into the lung cancer cells (A549). Thus, the developed nanosensing approach served as the potential fluorescent probes in medical and biological fields, especially for lung cancer disease diagnosis based on highly selective and sensitive detection of long-chain aldehydes.

A selective spectrofluorometric determination of micromolar level of cyanide in water using naphthoquinone imidazole boronic-based sensors and a surfactant cationic CTAB micellar system.

We developed a new spectrofluorometric method for qualitative and quantitative determination of cyanide in water using the incorporation of naphthoquinone imidazole boronic-based sensors (m-NQB and p-NQB) and a cationic surfactant, certyltrimethyl ammonium bromide (CTAB). This micellar system exhibited great selectivity for cyanide detection with an assistance of the cationic surface of micelle. The interaction of boronic acid of the sensor toward cyanide in CTAB micellar media gave a quantitative measure of cyanide concentration in the micromolar level. Under the optimal condition, fluorescence intensity at 460 nm of m-NQB and p-NQB provided two sets of linear ranges, 0.5-15 µM and 20-40 µM and the limit of cyanide detection of 1.4 µM. Hence, both sensors in CTAB aqueous micellar system offered a considerably promising cyanide detection with 1000-fold enhancement of the detection limit compared to those studied in DMSO: H(2)O. The proposed sensors could also be used to determine cyanide in water with good analytical characteristics.

A-D-A sensors based on naphthoimidazoledione and boronic acid as turn-on cyanide probes in water.

Three fluorescence sensors based on naphthoquinoneimidazole and boronic acid (A-D-A system) have been developed with high selectivity for cyanide in water. The fluorescence band at 460 nm was switched on upon substitution of cyanide on sensors in the CTAB micelle.

Colorimetric N-butyl-3,6-diamidecarbazole-based chemosensors for detection of fluoride and cyanide anions.

Colorimetric sensors from N-butyl-3,6-disubstituted carbazole derivatives containing nitroazobenzene (1) and nitrobenzene (2) were designed, synthesized and compared for their anion sensing ability. Computational simulations were undertaken to determine the optimum geometry of 1. Anion sensing studies revealed that selectivity in anion detection depended on the polarity of solvent, acidity of binding unit and basicity of the anion. The ability to sense via naked eye observations using the strong basic anions (F- and CN-) for both sensors arises from a deprotonation process at the binding sites attributed to the intramolecular charge transfer transition at the sensory unit. The discrimination of F- from CN- has been achieved by the optimization of solvent polarity. Sensor 1 offers a promising property over sensor 2 with a lower detection limit, a few of anion interference and higher stability.

Self-assembly of Gd3+/SDS/HEPES complex and curcumin entrapment for enhanced stability, fluorescence image in cellular system.

At present, strategies to disperse hydrophobic molecules in water without altering their chemical structures include conventional surfactant-based micellar and vesicular systems, encapsulation into water dispersible polymeric nanoparticles, and loading onto the surface of various metal nanoparticles. Here, we report a simple and low cost platform to incorporate hydrophobic molecules into a stable water dispersible nanostructure that can significantly increase the stability of the encapsulated materials. The platform is based on the incorporation of hydrophobic molecules into the self-assembled complex of gadolinium ion (Gd3+), sodium dodecyl sulfate (SDS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) called GdSH. After being incorporated, the two model hydrophobic dyes, curcumin and curcumin borondifluoride show approximately 50% and 30% improved stability, respectively. Investigation of the self-assembled 10-14 multilayered 60nm spheres with inter-layer distances of 4.25nm indicates coordination of SDS and HEPES with Gd3+. Incorporation of the hydrophobic molecules into the multilayered spheres results in reduction of the interlayer distance of the multilayer spheres to 4.17nm, suggesting enhanced packing of the hydrophobic chain of SDS and HEPES around the Gd3+. The incorporation of the two curcuminoids into the self-assembled complex also causes an increase in fluorescence quantum yield of the two dyes, thus suggesting spatial confinement of the packed dye molecules. The better cellular uptake of the nanoparticles is responsible for the expected enhancement in fluorescence image of the encapsulated materials.

Calix[4]arenes containing ferrocene amide as carboxylate anion receptors and sensors.

Calix[4]arene derivatives containing amide ferrocene units at the wide rim and ethyl ester groups at the narrow rim, L1-L3, were synthesized and their anion binding and sensing properties were investigated. It was found from (1)H NMR titrations that L1-L3 were able to bind selectively with carboxylate anions. Moreover, cyclic voltammetry and square wave voltammetry showed that L1-L3 were able to act as electrochemical sensors for carboxylate anions. [structure: see text]

Unpinning of spiral waves by electrical forcing in excitable chemical media.

We present experimental observations on the electrically forced release of spiral waves pinned to unexcitable circular obstacles in the Belosov-Zhabotinsky reaction. When the applied electric current density reaches the necessary current density J(unpin), the spiral tip is detached and subsequently drifts away from the obstacle. J(unpin) is found to increase with the obstacle diameter d. The growth rate ΔJ(unpin)/Δd is much higher for obstacles larger than the free spiral core compared to that for smaller obstacles. The experimental findings are confirmed by numerical simulations using the Oregonator model. The results imply that it is more difficult to release spiral waves pinned to larger obstacles, especially when the obstacle size exceeds that of the free spiral core.

Naked-eye and colorimetric detection of arsenic(III) using difluoroboron-curcumin in aqueous and resin bead support systems.

This work presents a new colorimetric method that is simple, rapid and cost effective for the determination of arsenic(III) in water samples. The method is based on changes in the absorbance of difluoroboron-curcumin (BF2-curcumin), prepared by the reaction of borontrifluoride diethyletherate ((C2H5)2OBF3) and curcumin. The BF2-curcumin was dissolved in 60% ethanol, which yielded an orange solution with the maximum absorbance at 509 nm. Upon the addition of arsenic(III), the color of the BF2-curcumin solution changed from orange to blue and the absorbance was measured by UV-visible spectrometry at 632 nm. The BF2-curcumin was applicable in both solution and coated resin. Under the optimal conditions, the detection limits achieved by means of UV-visible spectrometry, naked-eye detection with BF2-curcumin solution and naked-eye detection with BF2-curcumin-coated resin were found to be 0.26, 25 and 30 µM, respectively.

Highly effective discrimination of catecholamine derivatives via FRET-on/off processes induced by the intermolecular assembly with two fluorescence sensors.

We proudly presented the novel sensor system based on intermolecular assembled complexes of two fluorescence sensors and a suitable catecholamine acting as a guest linker by the reaction between boronic acid and aldehyde moieties of the sensors with the diol and amine units of catecholamines, respectively. The FRET-on/off induced by the assembly could discriminate structural similarity of catecholamines.

Self-assembled coordination nanoparticles from nucleotides and lanthanide ions with doped-boronic acid-fluorescein for detection of cyanide in the presence of Cu2+ in water.

The sensor molecule, F-oBOH, containing boronic acid-linked hydrazide and fluorescein moieties was synthesized. For anion sensing applications, F-oBOH was studied in aqueous media. Unfortunately, F-oBOH was found to be hydrolyzed in water. Therefore, a new strategy was developed to prevent the hydrolysis of F-oBOH by applying self-assembly coordination nanoparticles network (F-oBOH-AMP/Gd(3+) CNPs). Interestingly, the nanoparticles network displayed the enhancement of fluorescent signal after adding Cu(2+) following by CN(-). The network, therefore, possessed a high selectivity for detection of CN(-) compared to other competitive anions in the presence of Cu(2+). Cyanide ion could promote the Cu(2+) binding to F-oBOH incorporated in AMP/Gd(3+) CNPs to give the opened-ring form of spirolactam resulting in the fourfold of fluorescence enhancement compared to Cu(2+) complexation without CN(-). Additionally, the log K value of F-oBOH-AMP/Gd(3+) CNPs⊂Cu(2+) toward CN(-) was 3.97 and the detection limits obtained from naked-eye and spectrofluorometry detections were 20µM and 4.03µM, respectively. The proposed method was demonstrated to detect CN(-) in drinking water with high accuracy.

Calix[4]quinones derived from double calix[4]arenes: synthesis, complexation, and electrochemical properties toward alkali metal ions.

Bis(calix[4]diquinones) 1 and 2 and double calix[4]diquinone 3 have been synthesized from their corresponding double calix[4]arenes 4, 5, and 6, respectively. Compounds 4-6 have been prepared from one-pot and stepwise syntheses under high pressure. Complexation studies of ligands 1-3 with alkali metal ions such as Li+, Na+, K+, and Cs+ were carried out by 1H NMR titrations. Receptors 1 can selectively form 1:1 complexes with Na+. Ligand 2 prefers to form 1:1 complexes with K+ and Cs+. Receptor 3 retained the cone conformation of the calix[4]arene unit upon binding K+ but changed the conformation when complexing Li+ and Na+. Electrochemical studies using cyclic voltammetry and square wave voltammetry showed significant changing of voltammograms of 2 and 3 in the presence of alkali metal ions. Receptor 3 showed the electrochemically switched binding property toward Na+ and K+.

Anion recognition as a method for templating pseudorotaxane formation.

Two thread-shaped cations, pyridinium nicotinamide and imidazolium, as their chloride and hexafluorophosphate salts, were studied with regards to complexation with hydrogen-bond-donating acyclic and macrocyclic ligands. In the latter case, the cations form pseudorotaxanes templated by the chloride anion but not hexafluorophosphate. This formation is a function of the coupling of ion-pairing between the cation and chloride anion and subsequent recognition of the anion by the macrocyclic diamide, which provides the driving force for interpenetration. We propose that this anion template principle is a general method for the construction of pseudorotaxanes and could be applied to other cationic threads, anions, and macrocyclic species.