Marked Color Change Research Articles

Colorimetric sensing based on silver nanoparticle-functionalized copper porphyrin nanozyme for glyphosate

Glyphosate, a widely used herbicide due to the broad-spectrum and high-efficiency properties, has the potential to accumulate in the human body via agricultural food and water sources throughout the food chain. Its safety for both human health and aquatic ecosystems remains a topic of significant debate. In this study, the presence of glyphosate could be directly detected through a notable colorimetric change in an aqueous solution. For this purpose, a silver nanoparticle-functionalized copper porphyrin metal-organic framework (AgNPs/Cu-TCPP) nanozyme was conveniently prepared for colorimetric sensing of glyphosate. The as-synthesized nanozyme that modified AgNPs with Cu-TCPP metal-organic framework as the precursor, has excellent peroxidase mimetic activity and specific recognition performance of glyphosate. The nanozyme demonstrated the ability to catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) using H2O2, resulting in a marked change in color. When glyphosate was added, which bonded with Cu2+, led to the occupation of the surface-active sites of the nanozyme, thereby making its catalytic performance ineffective. The concentration of glyphosate exhibited a linear range spanning from 2 to 400 μmol L−1, and the limit of detection was 0.67 μmol L−1 (S/N = 3). The colorimetric sensing approach employing AgNPs/Cu-TCPP nanozyme exhibits remarkable selectivity and reproducibility, enabling the detection of real samples with recovery rates of 98.3%–103.5%, indicating its potential applicability in safeguarding water and food quality.

Effect of carbamide peroxide on biomechanical properties of vacuum-formed retainers: A split-mouth randomized controlled trial

ObjectiveTo investigate the effect of tooth whitening on biomechanical properties of vacuum-formed retainers (VFRs). MethodsUsing a split-mouth, randomised controlled trial design, thirty participants were randomly allocated to receive whitening on either the upper or the lower arch, using 10 % carbamide peroxide for two weeks. Biomechanical properties such as hardness, tensile strength, and surface roughness were assessed two weeks after whitening was completed. ResultsTensile strength of the whitening arch (mean ± SD: 40.93 ± 3.96 MPa) was significantly lower than that of the control (47.40 ± 5.03 MPa) (difference 6.47 MPa, 95 % CI 4.51 – 8.42, p < 0.001). Hardness and internal roughness of the whitening arch (VHN = 14.63 ± 2.29 N/mm2 and Ra = 1.33 ± 0.35 µm, respectively) were significantly greater than those of the control (12.22 ± 1.86 N/mm2 and 0.96 ± 0.29 µm, respectively) (differences 2.41 N/mm2, 95 % CI 1.56 – 3.25, p < 0.001 and 0.37 µm, 95 % CI 0.23 – 0.51, p < 0.001, respectively). The whitening arch showed greater tooth colour change (ΔE = 6.00 ± 3.32) than the control (ΔE = 2.50 ± 1.70) (difference = 3.50, 95 % CI 2.43 – 4.56, p < 0.001). ConclusionsBased on this short-term study, marked tooth colour change was achieved by whitening with VFRs as the whitening trays, but this changed the VFRs’ biomechanical properties, including a decrease in tensile strength and an increase in hardness and internal roughness. Clinical significanceThe application of carbamide peroxide in VFRs may compromise their mechanical properties.

Tailoring the optical and mechanical properties of cellulose nanocrystal film by sugar alcohols and its pH/humidity-responsive behavior

Cellulose nanocrystals (CNC) have gained widespread attention in intelligent food packaging because of their iridescent optical properties. Here, we report a CNC composite film employing CNC, sugar alcohols (e.g., maltol, erythritol, mannitol, sorbitol, and xylitol) and natural pigment anthocyanins, which has a special iridescent color that can be used as a pH and humidity sensor. The effects of five sugar alcohols with different addition ratios on the structural, optical, and mechanical properties of the CNC films were investigated. The results demonstrated that the addition of sugar alcohol made composite films exhibiting a red-shift of λmax, a more uniform color in visual observation, and a larger pitch. Among them, the CNC-mannitol composite film with a ratio of 10:1 exhibited the best mechanical properties, possessing a tensile stress strength of 57 MPa and toughness of 137 J/m3. Subsequently, anthocyanins were incorporated to this composite film, which showed a marked color change along with the pH from 2 to 12 and exhibited a reversible color change from red to transparent upon a relative humidity change from 35 % to 85 %. Overall, such multi-environment-responsive iridescent films with excellent mechanical properties have a great potential for use in intelligent food packaging applications.

Rapid and reversible humidity-dependent colour change by water film formation in a scaled springtail.

Colour is often not a static trait but can change over time either through biotic or abiotic factors. Humidity-dependent colour change can occur through either morphological change (e.g. to feather barbules in birds) or by the replacement of air by water causing a shift in refractive index, as seen in arthropod multi-layer cuticles or scales. The scaled springtail Lepidocyrtus cyaneus has scales that produce colour largely via thin film interference from their lamina. We observed a marked colour change from golden to violet/purple coloration in humid conditions. Light microscopy, micro-spectrophotometry, contact angle goniometry and optical modelling indicate that the formation of a thin film of water on top of the hydrophilic scales increases their laminar thin film thickness, causing a shift towards violet/purple colour. Evaporation of the water film causes the metallic golden colour to return. This constitutes a remarkably rapid colour change (in the order of seconds), only limited by the speed of water film condensation and evaporation, that may serve as inspiration for new dynamically coloured materials and sensors.

Effect of the alcoholic strength of unaged wine distillates on the final composition of Brandy de Jerez aged in Sherry Casks®

Brandy is a spirit obtained from distilled wine that has an alcohol content equal to or greater than 36 % ABV (Alcohol by Volume). It undergoes an ageing process in oak wood casks with a capacity of up to 1000 L for a minimum of six months. During this process, a series of physicochemical and sensory changes take place that confer the initial wine distillate with a series of improvements to its sensory profile. Such changes are mainly determined by the intrinsic characteristics of the wood and by those associated with the manufacturing process of the casks. The previous use of the casks, ageing time and the alcoholic strength of the wine distillate are also important factors, among others. The casks, which will have previously contained some type of Sherry wine (such as Fino, Amontillado, Oloroso and Pedro Ximénez), are known as Sherry Casks® and they must be used in the production of Brandy de Jerez. During the ageing of Brandy de Jerez, Sherry Casks® contribute to the final brandy via the compounds that are both inherent to the wood they are made of and from the wine that they initially contained and that were retained in the wood pores. The alcohol content of the wine distillate to be aged significantly affects not only the quality of the brandy, but also the financial cost of the process. This study aimed to determine the influence on brandy of the alcoholic strength of wine distillates aged in static ageing systems using Sherry Casks®. Specifically, we assessed the physicochemical composition and sensory profile of Brandy de Jerez made from wine distillates with three different alcoholic strengths (40 %, 55 % and 68 % ABV) and aged for 24 months. The Brandy de Jerez with lower alcoholic strengths (40 % - 55 % ABV) were found to contain a higher concentration of polyphenolic compounds deriving from the wood as well as from the constituents of the cask-seasoning Sherry wine. The brandies with higher alcoholic strengths exhibited a marked colour change, while the 40 % and 55 % ABV brandies were perceived to have the best sensory characteristics.

Gelatin/poly(vinyl alcohol)-based dual functional composite films integrated with metal-organic frameworks and anthocyanin for active and intelligent food packaging

Innovative active and pH-colorimetric composite films were fabricated from gelatin/poly(vinyl alcohol) (Gel/PVA) integrated with copper-based metal-organic frameworks (Cu-MOFs) and red cabbage anthocyanin (RCA). The incorporation of Cu-MOFs improved the tensile strength, water resistance, and UV shielding properties of the developed composite films. The addition of anthocyanins and 3 wt% Cu-MOFs endowed the polymer matrix with excellent antioxidant (100 % against ABTS and DPPH radicals) and antibacterial (against Gram-positive and Gram-negative foodborne pathogenic bacteria) functions. The fabricated composite films exhibited significant color change at alkaline conditions of pH 7–12 and a marked color change upon exposure to ammonia. The designed indicator films used for shrimp freshness tracking and a visual color change from pink (for fresh shrimp) to green (for spoiled shrimp) was observed during storage at 28 °C for 24 h. The potential applications of the engineered composite films were studied by shrimp packaging, and the quality parameters of packaged samples were monitored during storage. The synergistic effects of adding anthocyanins and MOF nanostructures works for better product freshness preservation and responds well to shrimp spoilage level, introducing novel active and intelligent packaging options for practical smart packaging applications.

Benzotiazole‐Based Colorimetric Chemosensor for the Effective Detection of Hazardous Cyanide Ions

AbstractA new hydrazone based on 5‐nitrofurfural and 2‐hydrazinobenzothiazole (L) was introduced as a colorimetric chemosensor for rapid, selective, and sensitive detection of CN− ions in aqueous media. The chemosensor L was characterized using spectral methods such as FT‐IR, 1H, 13C NMR, UV‐Vis, and mass spectrometry. The interaction of L with the CN− ion provides a marked color change from yellow to blue‐green or blue, depending on the concentration of cyanide ions. The change in colour as well as in absorption maxima make it possible to detect CN− ions with the naked eye. The detection limit of the chemosensor L is 0.26 μM, which is below the WHO limit for cyanide ions in drinking water. Other competing anions (F−, Cl−, Br−, I−, SCN−, ClO3−, ClO4−, SO32−, H2PO4−, HSO4−, and NO3−) showed little effect on the detection of cyanide ions. Quantum chemical calculations confirm the recognition mechanism, which is based on the formation of a molecular complex of the −NH‐hydrazine fragment of the chemosensor L with cyanide ion. The chemosensor L applied on the paper and polymeric test strips can be used in experiments to detect cyanide ions in samples of drinking and river water.

Classification for Papaya Fruit Maturity Level With Convolutional Neural Network

Papaya California (Carica papaya L) is one of the agricultural commodities in the tropics and has a very big opportunity to develop in Indonesia as an agribusiness venture with quite promising prospects. So the quality of papaya fruit is determined by the level of maturity of the fruit, the hardness of the fruit, and its appearance. Papaya fruit undergoes a marked change in color during the ripening process, which indicates chemical changes in the fruit. The change in papaya color from green to yellow is due to the loss of chlorophyll. The papaya fruit is initially green during storage, then turns slightly yellow. The longer the storage color, the changes to mature the yellow. The process of classifying papaya fruit's ripeness level is usually done manually by business actors, that is, by simply looking at the color of the papaya with the normal eye. Based on the problems that exist in classifying the ripeness level of papaya fruit, in this research, we create a system that can be used to classify papaya fruit skin color using a digital image processing approach. The method used to classify the maturity level of papaya fruit is the Convolutional Neural Network (CNN) Architecture to classify the texture and color of the fruit. This study uses eight transfer learning architectures with 216 simulations with parameter constraints such as optimizer, learning rate, batch size, number of layers, epoch, and dense and can classify the ripeness level of the papaya fruit with a fairly high accuracy of 97%. Farmers use the results of the research in classifying papaya fruit to be harvested by differentiating the maturity level of the fruit more accurately and maintaining the quality of the papaya fruit.

Classification for Papaya Fruit Maturity Level with Convolutional Neural Network

Papaya California (Carica papaya L) is one of the agricultural commodities in the tropics and has a very big opportunity to develop in Indonesia as an agribusiness venture with quite promising prospects. So the quality of papaya fruit is determined by the level of maturity of the fruit, the hardness of the fruit, and its appearance. Papaya fruit undergoes a marked change in color during the ripening process, which indicates chemical changes in the fruit. The change in papaya color from green to yellow is due to the loss of chlorophyll. During storage, the papaya fruit is initially green, then turns slightly yellow. The longer the storage color, the changes to mature the yellow. The process of classifying papaya fruit's ripeness level is usually done manually by business actors, that is, by simply looking at the color of the papaya with the normal eye. Based on the problems that exist in classifying the ripeness level of papaya fruit, in this research, we create a system that can be used to classify papaya fruit skin color using a digital image processing approach. The method used to classify the maturity level of papaya fruit is the Convolutional Neural Network (CNN) Architecture to classify the texture and color of the fruit. This study uses eight transfer learning architectures with 216 simulations with parameter constraints such as optimizer, learning rate, batch size, number of layers, epoch, and dense and can classify the ripeness level of the papaya fruit with a fairly high accuracy of 97%. Farmers use the results of the research in classifying papaya fruit to be harvested by differentiating the maturity level of the fruit more accurately and maintaining the quality of the papaya fruit.

Color Stability of Nanoparticles-Modified Dental Resin-Based Composites

To evaluate the effect of beverages (coffee, tea, Cola-Cola, and mineral water) on the color stability of resin-based composite (RBC) materials modified with different nanoparticles (NPs). The specimens (70/beverage) were fabricated from light-cured RBCs and divided according to NPs into four groups: one control, unmodified (N0); and three experimental—ZrO2 (Zr), TiO2 (Ti), and SiO2 (Si) groups. Each experimental group was further subdivided into two subgroups according to NP concentrations: 3 wt.% and 7 wt.% (n = 10). A spectrophotometer was used to assess the color change (∆E) before and after six months of immersion. Data were analyzed and compared using one-way-ANOVA followed by Bonferroni’s post-hoc test (α = 0.05) and subsequently ∆E value conversion to National Bureau of Standards (NBS) units. The modified light-cured RBCs with ZrO2, TiO2, and SiO2 demonstrated smaller color changes after immersion in the beverages than the unmodified group (p &lt; 0.001). Zr groups showed the lowest ΔE, followed by Ti and Si groups; a 3% concentration resulted in a lower mean ΔE than the 7% concentration. NBS findings showed that coffee and tea produced marked unacceptable color changes (NBS units were &gt;3), and Coca-Cola resulted in noticeable color changes (NBS units between 1.5 and 3), while water produced slight color changes (NBS ≤ 1). Modification of RBCs with both concentrations of ZrO2, as well as 3% of TiO2 and SiO2, may improve its color stability. Based on NBS results, RBCs immersed in mineral water and Coca-Cola showed clinically acceptable color changes, while those immersed in coffee and tea were clinically unacceptable.

Synthesis and investigation of bis(phenyl)fluorene and carbazole appended dipodal Schiff base for fluorescence sensing towards Sn(II) ion and its regioselective polymerization

One-pot condensation reaction between 9,9-Bis(4-aminophenyl)fluorene and 9-Ethyl-9H-carbazole-3-carbaldehyde afforded a chemosensor ((N,N′)-4,4′-(9H-fluorene-9,9-diyl)bis(N-((9-ethyl-9H-carbazol-2-yl)methylene)aniline, SB) having Schiff base skeleton. The further step was the synthesis of the polymer (P-SB) via oxidative polycondesation reaction of SB. FT-IR, 1H NMR and 13C NMR instruments were used to characterize the functional groups on the monomer and polymer. Thermal stability and electrochemical features of SB and P-SB were characterized by thermogravimetric analysis-differential thermal analyses (TG-DTA) and cyclic voltammetry (CV), respectively. The glass transition and surface image of P-SB were determined from DSC and SEM measurements, respectively. UV–vis and photoluminescence spectroscopy (PL) allowed to determine the optical properties of SB and P-SB. The obtained polymer, which had the weight average molecular weight of 8400 Da identified by gel permeation chromatography (GPC), exhibited fluorescence property. The synthesized turn-on fluorogenic chemosensor SB showed high selectivity and sensitivity towards Sn2+ among the cations of Ag+, K+, Hg2+, Mn2+, Cd2+, Sn2+, Ca2+, Pb2+, Zn2+, Co2+, Ni2+, Cu2+, Fe3+, Al3+, Cr3+ and Cr6+. The fluorescence turn-on recognition process for the detection of Sn2+ was related to the restriction of CN isomerization, followed by inhibiting intramolecular charge transfer (ICT), with consequent chelation-enhanced fluorescence (CHEF) mechanism. The stoichiometry ratio of the analyte-sensor adduct in the solution was found to be 1:1 by Job's plot method concomitant with a dramatic increase in fluorescent signal at 471 nm and a marked color change from colorless to turquoise blue upon addition of Sn2+ ions. Limit of detection value for the formation of SB-Sn2+ chelation was calculated as 3.37 nM. No change in PL intensity of SB-Sn2+ chelation was observed in the company of other metal ions. Reversibility of the chemosensor in its binding towards Sn2+ was demonstrated in the presence of chelating agent EDTA. The synthesized SB could effectively detect Sn2+ ion as a fluorescent sensor.

Hydrogen-bond induced enhanced emission ratiometric fluorescent handy needle for visualization assay of amoxicillin by smartphone sensing platform.

Amoxicillin (AMO) is one of the most commonly used antibiotics, and its abuse in animal husbandry or clinical therapy can pose unpredictable hazards to humans. Therefore, it is crucial to develop a real-time and rapid method to accurately determine AMO content. Here, we designed a fluorescent nanoprobe for qualitative and quantitative AMO determination by using as-synthesized green safe materials of nontoxic red carbon dots (RCDs) and blue carbon dots (BCDs). In the presence of AMO, a reaction promoting hydrogen bonding occurred immediately, resulting in an instant increase in the intensity of the blue fluorescence of BCDs, accompanied by a marked color change from red to blue. For practical application, we designed a nontoxic sensing fluorescent handy needle to directly and quantitatively detect AMO in real samples. This portable and easy-to-use device was demonstrated on a smartphone platform based on 3D printing technology, which offers the advantages of simple production, excellent visualization, fast response, and instant quantitative detection. The device requires an extremely short detection time and has a sensitive detection limit of 2.39nM. The method presented here enables real-time assessment for food safety, as well as on-site detection under field conditions to track various trace substances for timely health checks.

Effect of Different Denture Cleansers on Color Stability of Acrylic Resin Teeth – An In Vitro Study

Introduction: The durability of denture teeth to colour change is critical in selecting denture teeth, especially in terms of aesthetic demands and patient expectations. It is critical that the artificial teeth color remains constant over time when exposed to various cleaning solutions. The objective of the study is to assess the influence of three different commercially available denture cleansers on the color of acrylic resin teeth using the digital photography method and the Commission Internationale de l’Eclairage (CIE) L*a*b* standard. Methodology: Sixty acrylic maxillary central incisor teeth were divided to three groups of 20 samples each. The samples were left immersed in three different denture cleansers (DENSIVE, SECURE and CLINSODENT) for one month, simulating one month of usage by the patient. Digital photography was used to obtain baseline and final color readouts of the teeth on the basis of CIE L*a*b* standard, using image analysis software (Adobe Photoshop Inc System) and the color alteration (ΔE) of the samples was computed. Results: Maximum color change was found in teeth treated with DENSIVE denture cleanser, followed by CLINSODENT and SECURE, respectively. And this was found to be statistically significant (p-value ≥ 0.05). Conclusion: It is possible to deduce that the color stability of acrylic resin teeth is influenced by the use of denture cleansing solutions, and a marked color change was noted with the digital photography method.

Surface roughness and color changes of dental PEEK related to staining beverages and cleaning methods

Considering that the microstructure, texture and surface characteristics are relevant factors that could affect the appearance and resistance of a material, the study aims to evaluate in vitro, the surface roughness development and color changes related to staining beverages and cleaning methods after simulated periods of clinical use. The discoloration processes of PEEK materials are caused by intrinsic or extrinsic factors and still require elucidation. Three types of unmodified or modified PEEK CAD/CAD materials were selected for investigation: Finoframe, Juvora medical and BioHPP-a reinforced material. Four different staining media were involved: hot coffee, black tea, cold juice, and distilled water as control. For staining thermal cycling was performed between a hot coffee/tea bath (55 °C) and a bath filled with distilled water (37 °C), respective between a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). For cleaning, a chemical method and mechanical brushing were selected. Simulated periods of clinical use were taken into consideration. Roughness measurements (Ra and Rz) were done after each period. Color changes (ΔE*) were calculated based on the CIE L*a*b* color system. Statistical analyses were performed, paired t-Test for comparisons between the means and Spearman correlations to assess relationships between roughness and color changes. After staining beverages, a significant decreased in Ra values for all three materials that were immersed in juice and, for B and F in tea, were measured. Perceivable changes have been identified for J in coffee and for B in tea. After brushing, Ra significant decreased for J, in all immersion environments and no perceivable color changes were reported. The chemical cleaning caused a significant decrease in surface roughness values for B and F, in all immersion environments and color changes were perceivable for J in juice. Surface characteristics were affected by staining, mechanical and chemical cleaning; during the study, no marked color changes of PEEK were detected.

Bis-BODIPY-based fluoride and cyanide sensor mediated by unconventional deprotonation of C−H proton

A novel bis-BODIPY-based colorimetric and fluorescent sensor (BODIPY-NN) for F− and CN− recognition with high selectivity and high sensitivity is reported. The designed sensor, BODIPY-NN, was synthesized by a one-step click reaction of azido-BODIPY with N,N′-dipropargylbenzene-1,2-diamine. The BODIPY-NN sensor displays a marked color change from pink to colorless and a remarkable turn-off fluorescence behavior exclusively toward F− and CN− ions. Analysis of 1H, 13C, 19F, 11B NMR and mass spectra, together with theoretical calculations, provides insight into the mechanism of anion binding to BODIPY-NN. The sensing mechanism was found to be unconventional deprotonation at pseudo-benzylic carbons attached to BODIPY cores in the presence of F− and CN− ions, to form the less highly conjugated BODIPY moieties, thereby displaying fluorescence quenching. Addition of water in the BODIPY-NN + F− system regenerates the sensor with restoration of its spectroscopic properties. In contrast, the CN− ions permanently disrupt the BODIPY moieties by nucleophilic displacement at the central boron atoms, which is irreversible upon addition of water. The detection limits for F− and CN− in THF are 83 and 72 nM, respectively. In particular, BODIPY-NN embedded in cetyltrimethylammonium micelles can be used as colorimetric detection of CN− ions in aqueous media.

Effect of Artificial Freeze/Thaw and Thermal Shock Ageing, Combined or Not with Salt Crystallisation on the Colour of Zamora Building Stones (Spain)

After subjecting Zamora building stones to accelerated ageing tests, colour changes were studied, namely: (a) freezing/thawing and thermal shock (gelifraction and thermoclasty), and (b) combination of freezing/thawing plus thermal shock and salt crystallisation (sulphates or phosphates) (gelifraction, thermoclasty and haloclasty). Zamora building stones are silicified conglomerates (silcretes) from the Cretaceous that show marked colour changes due to the remobilisation of iron oxyhydroxides. In this work, four varieties were: white stone; ochreous stone; white and red stone; and purple stone Their micromorphological characterization (skeleton, weathering plasma and porosity/cutan) is formed of grains and fragments of quartz and quartzite as well as by accesory minerals muscovite and feldspar (more or less altered), and some opaque. Quartz, feldspar and illite/mica were part of the skeleton; kaolinite, iron oxyhydroxides, and CT opal were part of the weathering plasma or cutans; their porosity were 11.7–8.7%. Their chromatic data have been statistically analysed (MANOVA-Biplot). They showed higher variations in ΔE*, ΔL*, Δa* and Δb*on combined freezing/thawing plus thermal shock and sulphates crystallisation leading to rapid alteration of the building stones. Chromatic differences between the other two artificial ageing tests were less evident and were not detected in all samples. The global effect of ageing on the Zamora building stones darkened them and reduced their yellowing. The ochreous stone suffered the least variation and the purple stone the most. This study of the colour by statistical analyse may be of interest for the evaluation and monitoring of stone decay, which is an inexpensive, simple, easy and non-destructive technique.

Smart films of carbohydrate-based/sunflower wax/purple Chinese cabbage anthocyanins: A biomarker of chicken freshness

Innovative pH-colorimetric sensor film was fabricated from agar and methylcellulose matrix (AM) with various concentrations of sunflower wax (SFW) (6%, 9%, 12%, and 15% w/w) combined with purple Chinese cabbage (CPC) anthocyanins for tracking chicken breast freshness. A bio-composition film AM/CPC with (hydrophobic) SFW exhibited significant color variations in acidic pH level of (2–6) and a slight shift in alkaline pH levels ranging from (7–12), as well as marked color change due to ammonia vapor. Microstructure analyses revealed that SFW was fixed effectively into the AM-CPC matrices. The incorporation of varying SFW concentrations enhanced the mechanical, thermal, antioxidant activity, reduced anthocyanin release and physical properties (mainly water vapor permeability), with the best performance at AM/CPC/9% SFW. Interestingly, SFW films demonstrated perfect defense opposing UV–vis and visible light. Finally, it was proved that the efficiency of the pH-colorimetric film as an indicator for evaluating the freshness of chicken breast.

Surface Characteristics and Color Stability of Dental PEEK Related to Water Saturation and Thermal Cycling.

(1) Background: The study was undertaken to evaluate the surface characteristics, microhardness, and color stability of PEEK materials related to water saturation and in vitro aging. (2) Methods: Custom specimens of unmodified and modified PEEK CAD/CAM materials were investigated: BioHPP, a ceramic reinforced PEEK, and Finoframe PEEK and Juvora medical PEEK, 100% PEEK materials. Forty-eight plates were sectioned in rectangular slices. The specimens were immersed in distilled water at 37 °C for a period of 28 days, and then subjected to aging by thermal cycling (10,000 cycles). Surface roughness was measured with a contact profilometer; nanosurface topographic characterization was made by Atomic Force Microscopy; Vickers hardness measurements were performed with a micro-hardness tester; color changes were calculated. All registrations were made before immersion in water and then subsequently once a week for 4 weeks, and after thermocycling. (3) Results: The studied reinforced and unfilled PEEK materials reached water saturation after the first week of immersion, without significant differences between them. The most affected from this point of view was the reinforced PEEK material. Thermocycling induces a significant increase inmicroroughness, without significant differences between the studied materials. In relation to the nanosurface topography and roughness, the reinforced PEEK material was the least modified by aging. The color changes after 4 weeks of water immersion and one year of simulated in vitro aging ranged from extremely slight to slight, for all materials. (4) Conclusions: Water absorption was associated with a decrease in microhardness. Surface characteristics are affected by water immersion and thermocycling. Perceivable or marked color changes of the materials were not detected during the study.

Ratiometric fluorimetric and colorimetric probe for sensing and imaging pH changes in living cells.

Cell, enzyme, and tissue activity in living organisms are closely related to intracellular pH. Detecting the changes of intracellular pH is important to understanding the physiological and pathological changes in the process of crucial cell metabolism. A pH probe (HTBI) based on hemicyanine was synthesized. The probe solution displayed a marked colour change from yellow to amaranth with the pH increase from neutral to basic; simultaneously, the emission spectra showed a significant red shift. The probe exhibited a ratiometric fluorescence emission (F586nm /F542nm ) characteristic of pKa 8.82. As expected, HTBI exhibited high sensitivity and selectivity for pH, fine photostability, reversibility, and low cytotoxicity. Therefore, it would be a very useful tool for measuring the intracellular pH changes.

Novel near-infrared spectroscopic probe for visualizing hydrogen sulfide in lysosomes

Considering the scarcity of hydrogen sulfide (H2S) probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelengths fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the relationship between the physiology and pathology of H2S at subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe SHCy-H2S for the specific detection of H2S in lysosome over other biological thiols was designed and synthesized. The xanthene-benzothiozolium fluorophore was chosen to provide fluorescence emission maxima over 735 nm, and 2,4-dinitrophenyl group was chosen as fluorescence quenching group and specific H2S response site. Impressively, SHCy-H2S exhibited high selectivity, fast response and detection limit as low as 0.116 μM for H2S, marked obvious color changes in naked-eye and fluorescence. Specially, SHCy-H2S was capable of specifically imaging endogenous lysosomal hydrogen sulfide, providing a potential tool for exploring the function of H2S at subcellular level.