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The alizarin red S assay is considered the gold standard for quantification of osteoblast mineralization and is thus widely used among scientists. However, there are several restrictions to this method, e.g., moderate sensitivity makes it difficult to uncover slight but significant effects of potentially clinically relevant substances. Therefore, an adaptation of the staining method is appropriate and might be obtained by increasing the mineralization ability of osteoblasts. In this study, cell culture experiments with human (SaOs-2) and murine (MC3T3-E1) osteoblasts were performed under the addition of increasing concentrations of calcium chloride (1, 2.5, 5, and 10 mM) or calcitonin (1, 2.5, 5, and 10 nM). After three or four weeks, the mineralization matrix was stained with alizarin red S and the concentration was quantified photometrically. Only calcium chloride was able to significantly increase mineralization, and therefore enhanced the sensitivity of the alizarin red S staining in a dose-dependent manner in both osteoblastic cell lines as well as independent of the cell culture well surface area. This cost- and time-efficient optimization enables a more sensitive analysis of potentially clinically relevant substances in future bone research.

An electrochemical sensor based on an electroactive nanocomposite was designed for the first time consisting of electrochemically reduced graphene oxide (ERGO), polyaniline (PANI), and poly(alizarin red S) (PARS) for ciprofloxacin (CIPF) detection. The ERGO/PANI/PARS-modified screen-printed carbon electrode (SPCE) was constructed through a three-step electrochemical protocol and characterized using FTIR, UV–visible spectroscopy, FESEM, CV, LSV, and EIS. The new electrochemical CIPF sensor demonstrated a low detection limit of 0.0021 μM, a broad linear range of 0.01 to 69.8 μM, a high sensitivity of 5.09 μA/μM/cm 2 , and reasonable selectivity and reproducibility. Moreover, the ERGO/PANI/PARS/SPCE was successfully utilized to determine CIPF in milk with good recoveries and relative standard deviation (< 5%), which were close to those with HPLC analysis. Graphical Abstract

In the present work, native chitosan (Ch) along with its chemically and physico-chemically modified versions, namely sulphate cross-linked chitosan (SCC) and sulphate cross-linked chitosan–bentonite composite (SCC-B), were employed as potential adsorbents for the removal of an anionic dye, Alizarin Red S (ARS) from aqueous solutions. All three adsorbents were extensively characterized using techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, Brunauer–Emmett–Teller analysis, thermogravimetric–differential thermal analysis, and pH point of zero charge. Various parameters were optimized, including pH of dye solution, contact time, adsorbent dose, initial adsorbate concentration and temperature of adsorption. Four adsorption isotherm models were studied and it was found that the Freundlich model was best-fit for all three systems. Maximum adsorption capacities towards adsorption of ARS were found to be 42.48, 109.12 and 131.58 mg g−1 for Ch, SCC and SCC-B, respectively. Kinetics of adsorption was examined by employing three well-known models in order to deduce the mechanism of adsorption. Thermodynamic studies show that the process is spontaneous and exothermic for all adsorbents employed. Furthermore, it was observed that for large sample volumes, the column adsorption method was more effective compared to the batch method.

In this work, the adsorption of Cr(VI) ions and the organic dye Alizarin Red S (ARS) was investigated using magnetite talc (Fe3O4@Talc) nanocomposite. Different characterization techniques such as scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), and thermogravimetric analysis (TGA) were used to demonstrate the physical and chemical properties of the fabricated Fe3O4@Talc nanocomposite. In addition, the adsorption isothermic, kinetic, and thermodynamic properties were illustrated. The results demonstrate that the investigated adsorption processes obeyed the Langmuir isotherm model for Cr(VI) and the Freundlich isotherm model for ARS dye, with a maximum adsorption capacity of 13.5 and 11.76 mg·g−1, respectively, controlled by pseudo second-order kinetics. Regeneration and reusability studies demonstrated that the prepared Fe3O4@Talc nanocomposite is a promising and stable adsorbent with considerable reusability potential.

Alizarin Red (AR) is one of the most colored hazardous industrial dyes. For effective removal of AR, a new sorbent of modified heterocyclic-magnetite chitosan nanocomposite labeled as AOC@MC was synthesized and characterized by FTIR, TGA, XRD, BET, TEM,SAED pattern and SEM-EDX. Effect of contact time, pH, adsorbent dosage, initial Alizarine Red concentration and temperature was investigated. The maximum AR removal was 98.9% and attained at optimum conditions which were pH = 3.0, contact time = 50 min., and adsorbent dosage = 0.03 g/L. The findings revealed that at pH 3 and 30 °C, the maximum adsorption capacity was approximately 162 mg/g. Within 50 min, equilibrium adsorption was attained. A pseudo-second-order equation might be used to fit the kinetic data that was acquired at the optimal pH level of 3. Langmuir adsorption isotherms could accurately represent the adsorption process. The antimicrobial properties of the functionalized sorbent AOC@MC and its heterocyclic base AOC were characterized by determining the zone of inhibition (ZOI) against Staphylococcus aureus and Klebsiella pneumonia as a model for Gram-positive and Gram-negative bacteria respectively. AOC@MC exhibits promising activity with clear zones of 20.1 ± 0.2 and 17.6 ± 0.4 mm for S. aureus and K. pneumonia respectively. Overall, the modified sorbent AOC@MC was efficient on AR dye removal and antibacterial activity compared to the corresponding heterocyclic compound AOC.

The extensive use of organic dyes reduces the quality of the water and adversely affects aquatic organisms. In recent years, researchers have become more interested in the adsorptive removal of dyes. Herein, biodegradable gelatin-based 3D hydrogels are cross-linked with epichlorohydrin, named as gelatin hydrogel under acidic conditions (GHA) and gelatin hydrogel under basic conditions (GHB). The synthesis of the desired hydrogels were confirmed using Fourier transformation infrared spectroscopy and scanning electron microscopy. They were used successfully for the adsorptive removal of dyes such as methylene blue (MB) and alizarin red S (ARS) from aqueous solutions and food samples. The optimization study shows that maximum adsorptive removal of MB and ARS were obtained at pH range of 4 to 9. The maximum adsorption capacities in the case of GHA for MB and ARS were 19.5 mgg −1 and 19.9 mgg −1 , respectively. Whereas, in the case of GHB, the maximum adsorption capacities for MB and ARS were 18.9 mgg −1 and 19.7 mgg −1 , respectively. The percent adsorption values in the range of 72 ± 2‒100 ± 2 shows that the developed methods can be successfully applied to water and food samples. Furthermore, both adsorbents follow the Freundlich adsorption isotherm and pseudosecond-order kinetics. Gelatin-3D hydrogels have significant adsorption capacity and are environmentally friendly, low-cost, and easy to synthesize. These qualities make them excellent platforms for the adsorptive removal of dyes from wastewater.

Synthetic organic dyes are widely used in various industrial sectors but are also among the most harmful water pollutants. In the last decade, significant efforts have been made to develop improved materials for the removal of dyes from water, in particular, on nanostructured adsorbent materials. Metal organic frameworks (MOFs) are an attractive class of hybrid nanostructured materials with an extremely wide range of applications including adsorption. In the present work, an iron-based Fe-BTC MOF, prepared according to a rapid, aqueous-based procedure, was used as an adsorbent for the removal of alizarin red S (ARS) and malachite green (MG) dyes from water. The synthesized material was characterized in detail, while the adsorption of the dyes was monitored by UV-Vis spectroscopy. An optimal adsorption pH of 4, likely due to the establishment of favorable interactions between dyes and Fe-BTC, was found. At this pH and at a temperature of 298 K, adsorption equilibrium was reached in less than 30 min following a pseudo-second order kinetics, with k″ of 4.29 × 10−3 and 3.98 × 10−2 g∙mg−1 min−1 for ARS and MG, respectively. The adsorption isotherm followed the Langmuir model with maximal adsorption capacities of 80 mg∙g−1 (ARS) and 177 mg∙g−1 (MG), and KL of 9.30·103 L∙mg−1 (ARS) and 51.56·103 L∙mg−1 (MG).

By combining boric acid-modified carbon dots ( p -CDs) and alizarin red (ARS), a double emission probe p -CDs@ARS with fluorescence at 410 nm and 600 nm is designed for the detection of glyphosate. When Cu 2+ is added, it binds with ARS to cause ARS release from p -CDs@ARS, which decreases the fluorescence at 600 nm. However, in the presence of glyphosate, glyphosate competes to the binding of Cu 2+ , releasing ARS to bind with p -CDs again. Therefore, the fluorescence of 600 nm recovers. Based on this, the fluorescence of 410 nm and 600 nm act as the reference and response signal, respectively, achieving the ratiometric fluorescence detection of glyphosate. The linear range of glyphosate detection is 0.5–50 µM with a limit of detection at 0.37 µM which is well below the maximum residue limit for glyphosate in food. When the probe is used to detect the glyphosate residue in Pearl River water and cucumber, the detection results are well consistent with those detected by HPLC. The established method based on p -CDs@ARS has the advantages that the assembly of ratiometric fluorescence probe is simple, and the detection speed is fast. Additionally, a typical INHIBIT logical system has been successfully constructed based on glyphosate, Cu 2+ , and the fluorescence signal of p -CDs@ARS. Graphical Abstract

Recent progress has been made in the application of novel zirconium-loaded amine-grafted walnut shells as multifunctional adsorbents for the remediation of Alizarin red (AR) and bacteria in aqueous solutions. The morphology and functional groups of ACWNS@Zr were studied using Brunauer–Emmett–Teller (BET) techniques, X-ray diffraction (XRD), pH point of zero charges (pHpzc), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. Adsorption and regeneration tests were carried out in batch and column mode. The ACWNS@Zr had a Langmuir maximum capacity of 415.5 ± 6.1 mg g −1 at 303 K. The spread plate technique was used to evaluate the adsorbent’s antimicrobial properties against Staphylococcus aureus and Escherichia coli . ACWNS@Zr exhibited inhibitory potential towards S. aureus and E. coli in the suspensions by 53.3% and 15.0%, respectively. Electrostatic interaction and complexation interaction could be the key mechanisms governing AR dye removal. Equilibrium isotherms fit Langmuir models better for both batch and column studies, while adsorption kinetics to pseudo-second-order and Thomas models for batch and column studies, respectively. Thermodynamic studies indicated that the adsorption process was endothermic and spontaneous. Furthermore, columns’ mass transfer capacity ( B ) increased as the concentration increased due to the enhanced driving force for AR adsorption onto ACWNS@Zr. Regeneration with NaOH solution of AR-loaded ACWNS@Zr was remarkable. Graphical abstract