Molecular rotors with long alkyl chains as fluorescent viscosity sensors for hydrocarbon and silicone oil fluids

A red-emitting mitochondria targetable fluorescent probe for detecting viscosity in HeLa, zebrafish, and mice

Viscosity, an essential parameter of the cellular microenvironment, has the ability to indicate the condition of living cells. It is closely linked to numerous diseases like Alzheimer's disease, diabetes, and cardiovascular disorders. Therefore, it is necessary to design tools to effectively monitor viscosity changes, which could provide promising avenues for therapeutic interventions in these diseases. Herein, we report a novel mitochondria-targeting fluorescent probe GX-VS which was suitable for the detection of viscosity changes in vivo and in vitro. The probe GX-VS had many advantages such as long emission wavelength (650 nm), large Stokes shift (105 nm), significant fluorescence enhancement (59-fold), high sensitivity, good biocompatibility and so on. Biological experiments showed that the probe could target mitochondria and detect viscosity alterations in HeLa cells. Moreover, it has been successfully utilized to monitor viscosity changes induced by lipopolysaccharides (LPS) in inflammatory zebrafishes and living mice, which further underscored the capacity of GX-VS to explore fluctuations in viscosity within living organisms.

A mitochondria-targeted dual-response sensor for monitoring viscosity and peroxynitrite in living cells with distinct fluorescence signals

Viscosity and peroxynitrite (ONOO-) are two significant indicators to affect and evaluate the mitochondrial functional status, which are nearly relational with pathophysiological process in many diseases. Developing suitable analytical methods for monitoring mitochondrial viscosity changes and ONOO- is thus of great importance. In this research, a new mitochondria-targeted sensor DCVP-NO2 for the dual determination of viscosity and ONOO- was exploited based on the coumarin skeleton. DCVP-NO2 displayed a red fluorescence "turn-on" response toward viscosity along with about 30-fold intensity increase. Meanwhile, it could be used as ratiometric probe for detection of ONOO- with excellent sensitivity and extraordinary selectivity for ONOO- over other chemical and biological species. Moreover, thanks to its good photostability, low cytotoxicity and ideal mitochondrion-targeting capability, DCVP-NO2 was successfully utilized for fluorescence imaging of viscosity variations and ONOO- in mitochondria of living cells through different channels. In addition, the results of cell imaging revealed that ONOO- would lead to the increase of viscosity. Taken together, this work provides a potential molecular tool for researching biological functions and interactions of viscosity and ONOO- in mitochondria.

Triphenylamine-Modified Cinnamaldehyde Derivate as a Molecular Sensor for Viscosity Detection in Liquids

Liquid safety is considered a serious public health problem; a convenient and effective viscosity determination method has been regarded as one of the powerful means to detect liquid safety. Herein, one kind of triphenylamine-modified cinnamaldehyde-based fluorescent sensor (3-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylaldehyde (DPABA)) has been developed for sensing viscosity fluctuations in a liquid system, where a cinnamaldehyde derivative was extracted from one kind of natural plant cinnamon and acted as an acceptor, which has been combined with a triphenylamine derivate via the Suzuki coupling reaction within one facile step. Twisted intramolecular charge transfer (TICT) was observed, and the rotation could be restricted in the high-viscosity microenvironment; thus, the fluorescent signal was released at 548 nm. Featured with a larger Stokes shift (223.8 nm in water, 145.0 nm in glycerol), high adaptability, sensitivity, selectivity, and good photostability, the capability of high signal-to-noise ratio sensing was achieved. Importantly, this sensor DPABA has achieved noninvasively identifying thickening efficiency investigation, and viscosity fluctuations during the liquid deterioration program have been screened as well. We believed that this unique strategy can accelerate intelligent molecular platforms toward liquid quality and safety inspection.

Activatable molecular rotor based on bithiophene quinolinium toward viscosity detection in liquids

The development of non-invasive and effective viscosity inspection methods during the liquid deterioration process is urgently needed since viscosity is one of the most important physical parameters of liquids. Methods featuring rapid detection, high sensitivity, cheap equipment, and fast result output are greatly desired. In this study, a viscosity-sensitive molecular rotor (BTPEQ) with a large Stokes shift (187 nm), and long emission wavelength (648 nm) has been developed. The rotor is comprised of a bithiophene donor and quinolinium acceptor, and displays a typical twisted intramolecular-charge transfer (TICT) feature, with good photostability, selectivity, and universality in various commercial liquids. With the aid of BTPEQ, the thickening effects of liquid thickeners can be determined. More importantly, BTPEQ was explored to visualize the viscosity variations in liquids at different metamorphic stages, and it was found that the viscosity level in microenvironments is highly dependent on the liquid food metamorphic period. It is worth noting that this approach can facilitate the continued perfection of fluorescent analytical methods for food quality and safety inspection.

Thioflavin-modified molecularly imprinted hydrogel for fluorescent-based non-enzymatic glucose detection in wound exudate

The concentration of glucose in the body's fluids is an important parameter that can indicate pathological conditions such as the progress of infected wounds. Several wearables and implantable detection approaches have been developed with high selectivity and sensitivity for glucose. However, all of them have drawbacks such as low stability, limited selectivity, and often require complex technology. In this work, we present a fluorescent-based cost-efficient imprinted hydrogel (MIH_GSH) capable of detecting glucose within 30 ​min. The imprinting approach allows us to improve the selectivity for glucose, overcoming the low specificity and limited binding efficiency at neutral pH of boronic acid-based detection mechanisms. The binding affinity determined for glucose-MIH_GSH was indeed 6-fold higher than the one determined for the non-imprinted hydrogel with a calculated imprinting factor of 1.7. The limit of detection of MIH_GSH for glucose in artificial wound exudate was calculated as 0.48 ​mM at pH 7.4 proving the suitability of the proposed approach to diagnose chronic wounds (ca. 1 ​mM). MIH_GSH was compared with a commercial colorimetric assay for the quantification of glucose in wound exudate specimens collected from hospitalized patients. The results obtained with the two methods were statistically similar confirming the robustness of our approach. Importantly, whereas with the colorimetric assay sample preparation was required to limit the interference of the sample background, the fluorescent signal of MIH_GSH was not affected even when used to measure glucose directly in bloody samples. The sensing mechanism here proposed can pave the way for the development of cost-efficient and wearable point-of-care tools capable of monitoring the glucose level in wound exudate enabling the quick assessment of chronic injuries.

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Highly sensitive and selective non-enzymatic approach to detect glucose in wound exudate.

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The fluorescent-based method ensured the detection of glucose in complex biological samples.

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The imprinting approach allowed overcoming the drawback of boronic acid-based methods.

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The cost-efficient approach is suitable for the development of point-of-care devices.

Effects of ms-aryl substitution on the structure and spectral properties of new CH(Ar)-bis(BODIPY) luminophores

In this article, we present synthesis, spectral characteristics, and results of DFT calculations of new CH(R)-bis(BODIPY) 1-3. They are characterized by the conformational mobility and sensitivity of fluorescence to polarity, proton-, electron donor ability and viscosity of the solvation environment. It is shown that fluorescence intensity of 1-3 increases in the homologous series of alcohols (ethanol, 1-propanol, 1-butanol, 1-octanol, 1-decanol) mainly due to decrease of medium acidic properties. The viscosity of the medium effects on the 1-3 fluorescence in a lesser degree. Compared to 1 and 2, the 3 is the most sensitive towards viscosity both in low-viscosity homologous alcohols and in high-viscosity ethanol-glycerol mixtures. In this regard, the sensitivity of fluorescence of CH(MeOPh)-bis(BODIPY) (compound 3) to the viscosity was studied in binary mixtures of polar DMF and low-polarity toluene with castor and vaseline oils, as well as to the macroviscosity of the solvate environment in mixtures of toluene with polystyrene. Prospects of the practical application of CH(R)-bis(BODIPY)s are proposed for the analysis of polarity, proton-donor properties and viscosity of the medium.

Environment-sensitive emission of anionic hydrogen-bonded urea-derivative-acetate-ion complexes and their aggregation-induced emission enhancement

Anions often quench fluorescence (FL). However, strong ionic hydrogen bonding between fluorescent dyes and anion molecules has the potential to control the electronic state of FL dyes, creating new functions via non-covalent interactions. Here, we propose an approach, utilising ionic hydrogen bonding between urea groups and anions, to control the electronic states of fluorophores and develop an aggregation-induced emission enhancement (AIEE) system. The AIEE ionic hydrogen-bonded complex (IHBC) formed between 1,8-diphenylnaphthalene (p-2Urea), with aryl urea groups at the para-positions on the peri-phenyl rings, and acetate ions exhibits high environmental sensitivities in solution phases, and the FL quantum yield (QY) in ion-pair assemblies of the IHBC and tetrabutylammonium cations is more than five times higher than that of the IHBC in solution. Our versatile and simple approach for the design of AIEE dye facilitates the future development of environment-sensitive probes and solid-state emitting materials.

Visual detection of viscosity through activatable molecular rotor with aggregation-induced emission

Food safety has become one of the urgent affairs in the global public health studies, and irregular viscosity is closely associated with the food spoilage extent. In this study, one kind of activatable molecular rotor (TPA-PBZ) based on triphenylamine derivates has been synthesized via the Schiff base condensation reaction. This rotor is comprised by donor-accepter conjugated structure, with aggregation induced-emission feature and a large Stokes shift of 160 nm in water. The rotation of aromatic rings in TPA-PBZ is restricted in high-viscosity microenvironment, with the gradually increasing fluorescence emission signal at 568 nm. Significantly, this rotor TPA-PBZ has successfully been applied not only in the determination of thickening effects of food gum, but also in the detection of viscosity enhancement during the liquid food spoilage process. This molecular rotor can be utilized as an intelligent monitor platform for food quality and safety inspection in viscosity-related conditions.

Nanomaterial-Based Drilling Fluids for Exploitation of Unconventional Reservoirs: A Review

The world’s energy demand is steadily increasing where it has now become difficult for conventional hydrocarbon reservoir to meet levels of demand. Therefore, oil and gas companies are seeking novel ways to exploit and unlock the potential of unconventional resources. These resources include tight gas reservoirs, tight sandstone oil, oil and gas shales reservoirs, and high pressure high temperature (HPHT) wells. Drilling of HPHT wells and shale reservoirs has become more widespread in the global petroleum and natural gas industry. There is a current need to extend robust techniques beyond costly drilling and completion jobs, with the potential for exponential expansion. Drilling fluids and their additives are being customized in order to cater for HPHT well drilling issues. Certain conventional additives, e.g., filtrate loss additives, viscosifier additives, shale inhibitor, and shale stabilizer additives are not suitable in the HPHT environment, where they are consequently inappropriate for shale drilling. A better understanding of the selection of drilling fluids and additives for hydrocarbon water-sensitive reservoirs within HPHT environments can be achieved by identifying the challenges in conventional drilling fluids technology and their replacement with eco-friendly, cheaper, and multi-functional valuable products. In this regard, several laboratory-scale literatures have reported that nanomaterial has improved the properties of drilling fluids in the HPHT environment. This review critically evaluates nanomaterial utilization for improvement of rheological properties, filtrate loss, viscosity, and clay- and shale-inhibition at increasing temperature and pressures during the exploitation of hydrocarbons. The performance and potential of nanomaterials, which influence the nature of drilling fluid and its multi-benefits, is rarely reviewed in technical literature of water-based drilling fluid systems. Moreover, this review presented case studies of two HPHT fields and one HPHT basin, and compared their drilling fluid program for optimum selection of drilling fluid in HPHT environment.