An improved surface enhanced Raman spectroscopic method using a paper-based grape skin-gold nanoparticles/graphene oxide substrate for detection of rhodamine 6G in water and food

Organic toxins are persistent chemicals of global concern capable of accumulating in environment and food. Surface enhanced Raman spectroscopy (SERS) is a promising technique that facilitates onsite detection of organic toxins. However, the fabrication of a SERS substrate is complicated and difficult to provide flexibility, fastness and cost-effectiveness. This study aims to develop a paper-based SERS method using grape skin-gold nanoparticles/graphene oxide (GE-AuNPs/GO) as SERS substrate and evaluate its efficiency with rhodamine 6G (Rh6G) as a model organic toxin and a real water and food contaminant. GE-AuNPs synthesized by green method using grape skin waste extract and GE-AuNPs/GO showed a surface plasmon resonance at 536 and 539 nm, particle size 18.6 and 19.5 nm, and zeta potential -44.6 and -59.7 mV, respectively. Paper-based SERS substrates were prepared by coating a hydrophobic thin-film of 30% polydimethylsiloxane solution in hexane on Whatman no. 1 filter paper, followed by drop-casting GE-AuNPs or GE-AuNPs/GO and drying. The SERS signals of Rh6G showed an enhancement factor of 5.8 × 10⁴ for GE-AuNPs and 1.92 × 10⁹ for GE-AuNPs/GO, implying that a combination of electromagnetic surface plasmon, charge transfer and molecular resonances may be responsible for a higher enhancement of signal by the latter. A low detection limit of 7.33 × 10^-11 M in the linear range of 10^-11-10^-5 M was obtained for GE-AuNPs/GO, while the relative standard deviation of repeatability and reproducibility was 9.6 and 12.6%, respectively. Paper-based GE-AuNPs/GO SERS substrate was highly stable as <20% loss in efficiency was shown over a 60-day storage period. Application to real samples showed a high recovery of Rh6G from tap water (93.9-100.8%) as well as food samples such as red chilli powder (91.0-95.4%), red glutinous rice ball (96.6-98.3%) and tomato ketchup (98.9-102.3%) after QuEChERS extraction. Collectively, the developed paper-based GE-AuNPs/GO can be a potential substrate for sensitive onsite detection of rhodamine 6G by SERS method.

A sustainable and green chlorophyll/TiO2:W composite supported on recycled plastic bottle caps for the complete removal of Rhodamine B contaminant from drinking water

This investigation reports the photocatalytic performance of the tungsten doped titania (TiO₂:W or TW) with and without coating of chlorophyll (Chl) for the removal of the RhB dye from the drinking water. These particles were also supported on recycled plastic bottle caps (Bcap) to form other photocatalytic composites (TW/Bcap and TW + Chl/Bcap). The SEM images demonstrated that the TW particles without Chl had irregular shapes and sizes of 0.8-12 μm. The TW particles coated by the Chl presented shapes of quasi-rounded grains and smaller particle sizes of 0.8-1.8 μm. The photocatalytyic experiments showed that the photocatalyst powders containing Chl removed completely the RhB dye from the water after 2h under UV-VIS light, while the photocatalyst without Chl removed a maximum of 95% of the RhB. Interestingly, the TW/Bcap and TW + Chl/Bcap composites removed 94-100% of the RhB after 2h. Those ones removed such dye by photocatalysis and by physical adsorption at the same time (as confirmed by the absorbance and FTIR measurements), therefore, the removal of RhB was still very high. Scavenger experiments were also achieved and found that the •OH radicals are the main oxidizing species generated by the photocatalysts with and without Chl. The •O₂^- radicals and holes (h⁺) were the secondary oxidizing species. The presence of the chlorophyll on the photocatalyst increased in general the light absorption and the photocurrent. Overall, our work demonstrated that making composites with recycled plastic bottle caps is a feasible alternative to remove dyes from contaminated drinking water with high efficiency and low cost.

carba-Nucleopeptides (cNPs): A Biopharmaceutical Modality Formed through Aqueous Rhodamine B Photoredox Catalysis

Exchanging the ribose backbone of an oligonucleotide for a peptide can enhance its physiologic stability and nucleic acid binding affinity. Ordinarily, the eneamino nitrogen atom of a nucleobase is fused to the side chain of a polypeptide through a new C-N bond. The discovery of C-C linked nucleobases in the human transcriptome reveals new opportunities for engineering nucleopeptides that replace the traditional C-N bond with a non-classical C-C bond, liberating a captive nitrogen atom and promoting new hydrogen bonding and π-stacking interactions. We report the first late-stage synthesis of C-C linked carba-nucleopeptides (cNPs) using aqueous Rhodamine B photoredox catalysis. We prepare brand-new cNPs in batch, in parallel, and in flow using three long-wavelength photochemical setups. We detail the mechanism of our reaction by experimental and computational studies and highlight the essential role of diisopropylethylamine as a bifurcated two-electron reductant.

A novel and controllable SERS system for crystal violet and Rhodamine B detection based on copper nanonoodle substrates

Copper nanostructures have attracted more and more attention due to low preparation cost, similar thermal conductivity and optical characteristics to silver nanostructures. A novel macroscopic dendritic copper nanonoodles with the length of 3-50 mm prepared by solid-state ionics method at 10 μA direct current electric field (DCEF) using fast ionic conductor RbCu₄Cl₃I₂ films was reported. The surface-enhanced Raman scattering (SERS) performance of prepared copper nanonoodles was detected by crystal violet (CV) and rhodamine B (RB) aqueous solution as analyte molecules. The results present that the copper nanonoodles assembled by short-range order copper nanowires and the diameters of nanowires changed from 20 nm to 80 nm, many regularly arranged nanoparticles with the diameter from 5 to 10 nm existed on the prepared copper nanonoodles, which lead to the nanonoodles have high surface roughness. The copper nanonoodles contain only Cu element, no O element and the fractal dimension of copper nanonoodles is 1.355 because of macroscopic dendritic structures. The prepared copper nanonoodles composed of pure Cu have high surface roughness and the free electrons on the rough copper nanonoodles resonate with the atomic nuclei inside the copper nanonoodles to form a locally enhanced electromagnetic field under the excitation of incident light, so the limiting concentrations for CV and RB detected by the prepared copper nanonoodles are as low as 1 × 10^-11 mol/L and 1 × 10^-12 mol/L, respectively. The centimeter-scale copper nanonoodles with low limiting concentration of analyte molecules can be used to detect harmful food additives.

Ultrasensitive Electrochemical Detection and Plasmon-Enhanced Photocatalytic Degradation of Rhodamine B Based on Dual-Functional, 3D, Hierarchical Ag/ZnO Nanoflowers

The sensitive detection and degradation of synthetic dyes are pivotal to maintain safety owing to the adverse side effects they impart on living beings. In this work, we developed a sensitive electrochemical sensor for the nanomolar-level detection of rhodamine B (RhB) using a dual-functional, silver-decorated zinc oxide (Ag/ZnO) composite-modified, screen-printed carbon electrode. The plasmon-enhanced photocatalytic degradation of organic pollutant RhB was also performed using this nanocomposite prepared by embedding different weight percentages (1, 3, and 5 wt%) of Ag nanoparticles on the surface of a three-dimensional (3D), hierarchical ZnO nanostructure based on the photoreduction approach. The structure and morphology of an Ag/ZnO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental mapping, ultraviolet-visible (UV-vis) spectroscopy, and X-ray diffraction (XRD). The electrochemical sensor exhibited a very high sensitivity of 151.44 µAµM^-1cm^-2 and low detection limit of 0.8 nM towards RhB detection. The selectivity, stability, repeatability, reproducibility, and practical feasibility were also analyzed to prove their reliability. Furthermore, the photocatalysis results revealed that 3 wt% of the Ag/ZnO hybrid nanostructure acquired immense photostability, reusability, and 90.5% degradation efficiency under visible light. Additionally, the pseudo-first-order rate constant of Ag-3/ZnO is 2.186 min^-1 suggested promising activity in visible light photocatalysis.

Quantifying H2O2 by ratiometric fluorescence sensor platform of N-GQDs/rhodamine B in the presence of thioglycolic acid under the catalysis of Fe3

In the presence of thioglycolic acid (TGA) and under the catalysis of Fe³⁺, a simple, rapid, sensitive, selective and effective ratiometric fluorescence sensor platform based on the mixed physically blue nitrogen-doped graphene quantum dots (N-GQDs) as probe signals and orange rhodamine B as internal standard signals has been constructed for analysis of H₂O₂ in human serum. TGA is the key factor for fluorescence response toward H₂O₂ by N-GQDs and the mechanism is H₂O₂ reacts speedily with TGA under the catalysis of Fe³⁺, and produces intermediate of superoxide anions (O₂^-), which accepts electrons from N-GQDs, and generates graphene oxide, causing the fluorescence quench of N-GQDs. Compared with N-GQDs probe, the sensitivity of the ratiometric fluorescence sensor platform of N-GQDs/rhodamine B for analysis of H₂O₂ has been improved by nearly 5-folds. Under the optimum conditions, F_λ=580nm/F_λ=440nm has a good linear relationship with the concentration of H₂O₂ and the detection limit of H₂O₂ is 0.46 μmol/L with 3.5% RSD. The established sensor platform has been successfully used for probing H₂O₂ in human serum with satisfactory results. The superior performance of the probe lies in its high selectivity and can be directly employed in detecting H₂O₂ in serum samples without any sample pretreatment procedures.

Adsorption for rhodamine b dye and biological activity of nano-porous chitosan from shrimp shells

The present work aims to evaluate the removal capacity of Rhodamine B dye (RhB) using nano-porous chitosan (NC) from shrimp shells. NC was characterized by XRD, SEM-EDS, N2 porosimetry, zeta potential (ZP), FTIR, DLS, and zero charge point (pHZCP). Compound central rotational design (CCRD) was used to determine the ideal condition and antimicrobial activity was evaluated against different strains. NC showed characteristic of semi-crystalline material with negative charge surface (around - 21.13 mV), and SBET = 1.12 m2 g-1, Vp = 0.0064 cm3 g-1, Dp = 32.09 nm and pHZCP ≈ 7.98. Kinetic adsorption showed the pseudo first-order model had the best fit, with adsorption capacity (q1) between 3.78 and 64.43 mg g-1 and pseudo first-order kinetic constant (k1) between 0.066 and 0.052 min-1. Sips model best described the equilibrium data, with a maximum adsorption capacity of 505.131 mg g-1. Antimicrobial activity was observed at 0.25 mg mL-1 for different strains. Therefore, NC has potential application in the removal of the dye, combining sustainable development associated with nanotechnology.

Optimized flow cytometry protocol for dihydrorhodamine 123-based detection of reactive oxygen species in leukocyte subpopulations in whole blood

Reactive oxygen species (ROS) and the ability of immune cells to mount an oxidative burst represent an important defense during microbial invasion, but is also recognized for playing a significant role in the progression of inflammatory disorders and disease. Although neutrophils produce the strongest ROS-response, other leukocytes and their cell subsets could play a significant role. Isolation of specific cells for determining their ROS-response can affect their functionality and is laborious or hard to replicate in different settings. We have therefore established a whole blood assay, that only requires 100 μL heparinized blood and utilizes the dihydrorhodamine (DHR) 123 ROS-probe combined with cell surface antibody staining for the specific detection of ROS in several subsets of cells simultaneously using flow cytometry. Although the flow markers chosen are interchangeable with other direct conjugated and cell specific antibodies depending on the research question, we focused on neutrophils (SSC^highCD16^brightHLA-DR^neg/low), eosinophils (SSC^highCD16^lowHLA-DR^low/negCD193^positiveCD125^positive) and monocyte subsets (SSC^intermediateHLA-DR^highCD14^low-positiveCD16^{negative-positive}). As a RBC-lysis reagent we compared BD FACS Lysis Solution to the in-house prepared ammonium-chloride‑potassium based ACK Lysis Buffer, that does not fix or permeabilize the immune cells. We find that ACK-lysis of stimulated and stained samples results in superior surface staining, decreased loss of cell subsets, and enhanced resolution of the DHR-signal. Compared to the other cells analyzed in healthy blood donors, neutrophils responded with the highest ROS-response to all tested stimuli (fMLP (low stimuli), E. coli, and PMA (high stimuli)), where eosinophils and the three monocyte subsets also showed an extensive ROS-response when stimulated with E. coli or PMA. Our assay provides the possibility for researchers to examine the ROS-response of specific cell subsets in specific patient groups ex vivo and could also allow the analysis of pharmacological intervention studies targeting ROS, which ultimately can advance the field of immunological research.

Analyses on intracellular Fe3+ with a rhodamine probe: "turn-on" response, specific recognition and bioimaging

To overcome the existing difficulty in distinguishing ferric from ferrous ions, a rhodamine-containing probe was designed to combine with Fe³⁺ based on an opening-closing transformation of the spirolactam ring in the rhodamine moiety. Through a specific and stoichiometric fluorescence response towards Fe³⁺ by 1 : 1 binding accompanied by an obvious color change in the recognition process of Fe³⁺, a "naked-eye" detection method of Fe³⁺ in an aqueous environment is possible. Theoretical calculations gave a possible recognition mechanism of the probe-Fe³⁺ system. Further cytotoxicity and bioimaging in living L929 cells suggested the probe's future applications as a real-time analytical method for intracellular Fe³⁺ in clinical diagnosis. Besides, bioimaging applications enable the dynamic labelling and tracking of Fe³⁺ in biological systems.

A novel heptamethine cyanine photosensitizer for FRET-amplified photodynamic therapy and two-photon imaging in A-549 cells

In this study, a new cyanine-based photosensitizer Cy-N-Rh was developed for photodynamic therapy. Based on fluorescence resonance energy transfer (FRET) mechanism, utilizing the absorption of the donor rhodamine (Rh), the acceptor heptamethine cyanine unit (Cy) was indirectly excited to produce singlet oxygen (¹O₂). The efficiency of energy transfer from the donor Rh to the acceptor Cy was 78.5%. Meanwhile, the singlet oxygen yield of Cy-N-Rh (Φ_Δ = 12.00%) was much higher than that of the acceptor Cy (Φ_Δ = 4.35%) without FRET. Moreover, the dual cation gave Cy-N-Rh with excellent mitochondria-targeting ability with Pearson's correlation coefficients of 0.90 and 0.91, respectively. In the MTT test, Cy-N-Rh had low dark cytotoxicity with cell survival rate above 90% and high photo cytotoxicity with cell survival rate below 40%. The cell apoptosis assay also demonstrated the role of the photosensitizer Cy-N-R visually. More importantly, Cy-N-Rh fulfilled two-photon excitation fluorescence imaging under the 800 nm femtosecond laser. All results indicate that this design strategy provides a new method for the development of higher-level cyanine photosensitizers.

A ratiometric fluorescence probe for imaging endoplasmic reticulum (ER) hypochlorous acid in living cells undergoing excited state intramolecular proton transfer

Hypochlorous acid (HOCl), one of the most important ROS in living organisms, appears to serve an important role in the immune system in vivo. Endoplasmic reticulum (ER), the largest organelle in cells, manages many biological processes connected to vital activities. To better obtain insight into the relationship of ER stress and HOCl level, a ratiometric fluorescent probe RHE, based on rhodamine combined with HBT and ER-targeting group, was designed and synthesized for HOCl detection in the ER. Probe RHE shows a large stokes shift about 155 nm, which is derived to ESIPT principle. In addition, probe RHE exhibited excellent properties such as fast response (<80 s), high sensitivity with a low detection limit (40 nM), high selectivity and anti-interference. Moreover, probe RHE displayed an excellent ER-targeting ability and had been successfully applied for detection of exogenous and endogenous HOCl in HepG2 cells.

Effects of Two Natural Bisbenzylisoquinolines, Curine and Guattegaumerine, Extracted from Isolona hexaloba on Rhodamine Efflux by Abcb1b from Rat Glycocholic-Acid-Resistant Hepatocarcinoma Cells

To develop new therapeutic molecules, it is essential to understand the biological effects and targets of clinically relevant compounds. In this article, we describe the extraction and characterization of two alkaloids from the roots of Isolona hexaloba—curine and guattegaumerine. The effect of these alkaloids on the multidrug efflux pump ABCB1 (MDR1/P-Glycoprotein) and their antiproliferative properties were studied. Compared to verapamil, a widely used inhibitor of P-gp, curine and guattegaumerine were found to be weak inhibitors of MDR1/P-Glycoprotein. The highest inhibition of efflux produced by verapamil disappeared in the presence of curine or guattegaumerine as competitors, and the most pronounced effect was achieved with curine. Altogether, this work has provided new insights into the biological effects of these alkaloids on the rat Mdr1b P-gp efflux mechanism and would be beneficial in the design of potent P-gp inhibitors.

Robust and sustainable Mg1-xCexNiyFe2-yO4 magnetic nanophotocatalysts with improved photocatalytic performance towards photodegradation of crystal violet and rhodamine B pollutants

This study aims at manufacturing Ce³⁺/Ni²⁺ ions doped Mg nanoferrites by the sol-gel method for the photocatalytic degradation of rhodamine B and crystal violet pollutants under visible natural sunlight. The particle size of synthesized nanoferrites was calculated through XRD, Hall-William plots, and TEM analysis, which perfectly agree with each other. FTIR study investigated the existence of stretching vibrations in M - O (metal-oxygen) complexes at the tetrahedral (A-site) and octahedral sites (B-site). The Raman spectra of synthesized nanophotocatalysts show the presence of four vibrational modes (E_g + 2T_2g + A_1g), providing suitable information of occupancy of Mg²⁺, Ce³⁺, Ni^2+, and Fe³⁺ ions at the interstitial sites of undoped and Ce³⁺/Ni²⁺ doped MgFe₂O₄ crystal structure. The synthesized MGF3 nanophotocatalyst performs well with degradation of 97.674% crystal violet (CV) and 90.05% rhodamine B (RhB) under natural sunlight in 60 min. The experimental results showed that doped MgFe₂O₄ nanoferrites have a high tendency to photodegrade the RhB and CV dyes in an aqueous form. The pseudo-first-order equation reflects the best photocatalytic process kinetics and studied the feasibility of RhB and CV dyes adsorption on the doped and undoped MgFe₂O₄ nanoferrites. The results show good support for adsorption by the spontaneous photodegradation process. The excellent photocatalytic activity of synthesized nanoferrites under natural sunlight verifies them as a potential candidate for the photodegradation of organic dyes. Finally, the antibacterial activity of magnetic nanoferrites was examined against S. aureus and E. Coli. The studies demonstrated that synthesized magnetic nanoferrites were more effective against S. aureus.

Designing Z-scheme AgIO4 nanorod embedded with Bi2S3 nanoflakes for expeditious visible light photodegradation of congo red and rhodamine B

The present study describes the enhanced photodegradation of organic pollutant dyes, congo red (CR) and rhodamine B (RhB) dyes under visible light irradiation. AgIO₄ nanorods decorated on Bi₂S₃ nanoflakes in various proportions were synthesized via sono-chemical route wherein the deposition of varying amounts of AgIO₄ on Bi₂S₃ plays a pivotal role in improving the photodegradation ability. The characterization of the as-synthesized nanohybrids was assessed by XRD, UV-vis DRS, PL, EIS, ESR, FT-IR, XPS, HR-TEM, FE-SEM, N₂ adsorption and desorption techniques. The effect of initial CR and RhB dye concentration, reaction pH and usage of nanohybrid concentration were investigated where 30%-AgIO₄/Bi₂S₃ exhibited excellent visible light photodegradation of 95.58% for CR and 96.11% for RhB dyes at 140 min and 100 min respectively. The superoxide (•O^2-) and hydroxyl radicals (•OH) played predominant role in the photodegradation of CR and RhB which is experimentally confirmed by radical trapping experiments. Also, the photocatalysts exhibited good photo stability and excellent reusability. The TOC analysis confirmed the complete mineralization of CR and RhB dyes by the nanohybrid and the formation of possible intermediate and degradation pathway was delineated based on GC/MS analysis. The outstanding photodegradation performance were ascribed to the Z-scheme charge transfer path, which effectively promotes the separation and transfer of e^-/h⁺ pairs, resulting in a strong redox activity of the accumulated charge to decompose organic dyes during the degradation reaction. The study suggested that the nanohybrid can be utilized for the removal of organic pollutants from the contaminated water bodies.

Study on treatment of acid red G with bio-carbon compound immobilized white rot fungi

Corn straw biochar was used as a carrier to immobilize white rot fungi and the removal performance of immobilized pellets for acid red G (ARG) dye was studied. The results showed that the removal rate of ARG could reach 96.17% under the best preparation conditions of immobilized pellets (3% sodium alginate concentration, 0.7% corn straw biochar, 5% white rot fungus mycelium suspension, 4% CaCl₂, and 36 h immobilization time). The orthogonal test results showed that the best combination was the immobilized pellets dosage of 200/100 mL, pH of 4.5, rotation speed of 150 r/min, and initial concentration of 20 mg/L dye at 30 °C. The degradation pathway of ARG by immobilized microspheres was studied by ultraviolet-visible spectrometer, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectrometry. The results showed that ARG was degraded into aniline and 5-(acetamino)-4-hydroxy-3-amino-2,7-naphthalene disulfonic acid. Aniline was further deaminated to form benzene, and benzene was ring opened to form other organic compounds; 5-(acetylamino)-4-hydroxy-3-amino-2,7-naphthalene disulfonic acid was dehydroxylated to form 5-(acetylamino)-3-amino-2,7-naphthalene disulfonic acid. This study shows that the prepared biochar immobilized pellets can be used as an efficient water treatment material to remove ARG dye from wastewater.

Self-assembling of 3D layered flower architecture of BiOI modified MgCr2O4 nanosphere for wider spectrum visible-light photocatalytic degradation of rhodamine B and malachite green: Mechanism, pathway, reactive sites and toxicity prediction

In this study, 3D BiOI nanoparticle (BOI NPs) modified MgCr₂O₄ nanoparticle (MCO NPs) was fabricated by simple sonochemical and coprecipitation method for the enhanced photocatalytic activity. The morphological structure of the MgCr₂O₄-BiOI nanocomposite (MCO-BOI NCs) was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), electron impedance spectroscopy (EIS) and photo luminescence (PL). The lower in the PL intensity and small arc in EIS for NCs shows the effective charge separation and lower in rate of recombination of charge carriers in NCs than the pure MCO and BOI NPs. The degradation efficiency of Rhodamine B (RhB) and malachite green (MG) by MCO-BOI NCs was found to be 99.5% and 98.2% receptivity. In addition, the photocatalytic degradation of RhB and MG was studied under various environmental parameters (different pH, varying the concentration of NCs and dyes) and response surface (RSM) plot was performed. The complete mineralization of RhB and MG by MCO-BOI NCs was determined by TOC. In addition, the photocatalytic degradation pathway was elucidated based on GC-MS results and Fukui function. In addition, the toxicity of intermediate formed during the degradation of RhB and MG was predicted by ECOSAR. The present work highlights the application of MCO-BOI NCs in environmental remediation for toxic pollutant removal.

Monitoring of glutathione using ratiometric fluorescent sensor based on MnO2 nanosheets simultaneously tuning the fluorescence of Rhodamine 6G and thiamine hydrochloride

L-glutathione (GSH) which has reducibility and integrated detoxification plays an important role in maintaining normal immune system function. Its abnormal levels are relevant to some clinical diseases. In this work, a facile ratiometric fluorescence sensor for GSH was designed based on MnO₂ nanosheets, Thiamine hydrochloride (VB₁) and Rhodamine 6G (R6G). VB₁ could be oxidized into fluorescent ox-VB₁ due to the strong oxidizing property of MnO₂, and MnO₂ nanosheets simultaneously could quench the fluorescence of R6G based on the inner filter effect (IFE). MnO₂ could react with GSH to form Mn²⁺, which caused its losing oxidizing property and quenching capacity. According to this principle, the concentration of ox-VB₁ diminished, resulting in its fluorescence intensity decreasing at 455 nm and the fluorescence of R6G recovering at 560 nm. Under optimal conditions, the VB₁-MnO₂-R6G detection system showed a wide linear range towards GSH in the range of 1.0-300.0 µmolL^-1 with a low detection limit reaching 0.52 µmolL^-1. Furthermore, the method was also applied in the determination of GSH in human serum.

Nangibotide attenuates osteoarthritis by inhibiting osteoblast apoptosis and TGF-β activity in subchondral bone

Osteoarthritis (OA) is a chronic joint disorder that causes cartilage degradation and subchondral bone abnormalities. Nangibotide, also known as LR12, is a dodecapeptide with considerable anti-inflammatory properties, but its significance in OA is uncertain. The aim of the study was to determine whether nangibotide could attenuate the progression of OA, and elucidate the underlying mechanism. In vitro experiments showed that nangibotide strongly inhibited TNF-α-induced osteogenic reduction, significantly enhanced osteoblast proliferation and prevented apoptosis in MC3T3-E1 cells. Male C57BL/6 J mice aged 2 months were randomly allocated to three groups: sham, ACLT, and ACLT with nangibotide therapy. Nangibotide suppressed ACLT-induced cartilage degradation and MMP-13 expression. MicroCT analysis revealed that nangibotide attenuated in vivo subchondral bone loss induced by ACLT. Histomorphometry results showed that nangibotide attenuated ACLT-induced osteoblast inhibition; TUNEL assays and immunohistochemical staining of cleaved-caspase3 further confirmed the in vivo anti-apoptotic effect of nangibotide on osteoblasts. Furthermore, we found that nangibotide exerted protective effects by suppressing TGF-β signaling mediated by Smad2/3 to restore coupled bone remodeling in the subchondral bone. In conclusion, the findings suggest that nangibotide might exert a protective effect on the bone-cartilage unit and maybe an alternative treatment option for OA.

An N-nitrosation reaction-based fluorescent probe for detecting nitric oxide in living cells and inflammatory zebrafish

Nitric oxide (NO), an essential biological messenger molecule, participates in various physiological and pathological processes. The sensitive and specific detection of NO is of great significance for understanding the biological function of NO. Here, we synthesized a fluorescent probe (Rho-NO) for highly selective detection of NO both in vitro and in vivo. The high selectivity of Rho-NO is attributed to the fact that NO is easily replaced by electron donor amino group to form N-nitrosation products, causing rhodamine spiro ring open and fluorescence emit. Rho-NO showed a good linear response to NO (0-100 µM) with a low detection limit (0.06 µM). Importantly, it exhibited excellent specificity for NO detection in human serum and was also applied for imaging NO in living cells and inflammatory model of zebrafish. This work proves the potential of Rho-NO in pathological research and disease diagnosis.

Ultrasensitive SERS detection of Rhodamine 6G using a silver enriched MOF-derived CuFe2O4 microcubes substrate

Recently, spinel ferrites have attracted great attention as a SERS-active substrate for the detection of organic contaminants. In this paper, we report the synthesis of silver enriched MOF-derived CuFe₂O₄ (Ag-CFO) composite using a simple MOF template process. The as-synthesized Ag-CFO exhibits an excellent sensitivity towards the detection of Rhodamine 6G dye at the lowest concentration of 10^-14 M. Using noble metal nanoparticles in conjunction with CuFe₂O₄ provides an excellent SERS performance based on the synergistic effect resulting from uniform Ag distribution on the cubic morphology leading to the high electromagnetic effect and chemical mechanism of CuFe₂O₄. Ag-CFO microcubes also demonstrated remarkable recyclability, reproducibility, and chemical stability. Moreover, the substrate showed good sensitivity when it was examined in tap and river water for practical applications. The results confirm that Ag-CFO microcubes substrate has great potential as a reusable material for the rapid detection of environmental pollutants.

Heterogeneous compositions of oxygen-containing functional groups on biochars and their different roles in rhodamine B degradation

The reactivity of pyrogenic carbon has attracted a great deal of research attentions recently. The oxygen-containing structures are rich on the surface of biochars, and involved in accepting and donating electrons during the interactions between biochar and organic contaminants. In this work, the species and content of oxygen-containing functional groups on biochar surface were regulated through chemical modification, and batch sorption/degradation experiments were carried out for rhodamine B (RhB). Based on the comparison of surface functional groups, biochars produced below 200 °C mediated RhB degradation through phenol hydroxyl group, while semiquinone and carboxylic acid groups were the main reaction active sites for biochars produced at higher than 500 °C. Considering that various biochar properties play roles in mediating organics degradation, the strategies in manipulating biochar properties should be carefully considered.

Synergistic Generation of Radicals by Formic Acid/H2O2/g-C3N4 Nanosheets for Ultra-efficient Oxidative Photodegradation of Rhodamine B

Water pollution is a global challenge endangering people's health. In this work, an ultra-efficient photodegradation system of Rhodamine B (RhB) has been established using a graphitic carbon nitride nanosheet (CNNS) as the semiconductor photocatalyst, from which energy is harvested on both the conduction band and valence band by formic acid and hydrogen peroxide, respectively. The optimized FA/H₂O₂/CNNS system increases the apparent photodegradation rate of RhB by 25 folds, from 0.0198 to 0.4975 min^-1. Through a comprehensive investigation with reactive oxygen species scavengers, electron paramagnetic resonance, high-performance liquid chromatography-mass spectrometry, etc., an oxidative mechanism for RhB photodegradation has been proposed, which combines enhanced charge carrier migration and synergistic generation of multiple radicals. Comparable performance improvements have also been observed for similar systems with different semiconductors, suggesting that such a catalytic system could afford a general approach to enhance semiconductor-catalyzed photodegradation.

Comparison of rhodamine 6G, rhodamine B and rhodamine 101 spirolactam based fluorescent probes: A case of pH detection

Ring-opening reaction of rhodamine spirolactam has been widely applied to construct fluorescent probes. The fluorescence properties of the probe were finely tuned for specific purpose through changing the rhodamine fluorophore. However, the influence on response range and kinetic parameters of the probe during the change has been seldom discussed. Herein, we took pH detection as an example and constructed spirolactam based probes (RLH A-C) with Rhodamine 6G, Rhodamine B and Rhodamine 101. The pK_a values and observed rate constant k_obs of RLH A-C were determined and found to negatively correlated with the calculated Gibbs free energy differences ΔG_C-O and ΔG_TS respectively. The potential applications of RLH A-C in imaging acidic microenvironment were also investigated in cells. We expect the comparison of rhodamine fluorophores will facilitate the quantitative optimization of rhodamine spirolactam based fluorescent probes.

Synthesis, characterization, and application of MOF@clay composite as a visible light-driven photocatalyst for Rhodamine B degradation

Metal Organic Frameworks (MOFs) with natural clay materials is a relatively new research avenue that appears to reduce high production costs and address the instability issues of pure MOFs. A novel MOF and natural clay composites of MOF@Sp_n (n = 1-4) were fabricated by the in situ precipitation of stable MOF, Zr₆O₄(OH)₄ (ABDC)₆ (where ABDC = 2-aminobenzene-1,4-dicarboxylic acid), over natural sepiolite (Sp) clay and used as a photocatalysts for elimination of organic dyes in aqueous media. The formation of MOF@Sp_n due to its strong electrostatic interactions between the positively charged MOF and the negatively charged sepiolite. Optimizing the Sp content in the composite strongly influenced the dispersibility, crystallinity of MOFs, resulting in progressively functional hybrid materials with an excellent optoelectronic properties. The composites lessened the shortcomings of the individual components and made them suitable as a visible light-active, highly efficient, standalone photocatalyst material that can degrade RhB.

Chemically modified sugarcane bagasse-based biocomposites for efficient removal of acid red 1 dye: Kinetics, isotherms, thermodynamics, and desorption studies

Novel eco-friendly and economically favourable chemically modified biosorbents and biosomposites from sugarcane bagasse (SB) has been investigated for the first time for efficient removal of Acid red 1 dye from wastewater. As fabricated biosorbents and biocomposites were characterized analytically. Batch adsorption experiments has been performed to optimize operating parameters and the determined optimum conditions are; pH: 2, dose: 0.05 g, contact time: between 60 and 75 min, initial dye concentration: 400 mg L^-1, and temperature: 30 °C, at which maximum Acid red 1 dye removal capacities were found (within range of 143.4-205.1 mg g^-1) by as-designed SB-derived chemically modified biosorbents and biocomposites. This high adsorption capacity was accompanied due to its large specific surface area (30.19 m² g^-1) and excessive functional active binding sites. In terms of the nature of adsorption process, kinetic and isothermal studies demonstrated that experimental data shows greater fitness with pseudo 2nd order and Langmuir model. Thermodynamics analysis revealed that the adsorption process is spontaneous, feasible, and exothermic in nature. Adsorption selective studies signifies that lower concentration of co-existing metallic ions were not interfered during the removal of Acid red 1 dye, which confirms that under optimized adsorption conditions the biosorbents and biocomposites exhibited greater affinity for dye molecules. The excessive quantity (82%) of loaded dye molecules within the adsorbents were extracted within the NaOH eluting media which predicts that as designed biocomposites could have capability of reusability. Hence, it is anticipated that this type of novel SB-derived biocomposites could be considered as greener potential candidate material for commercial scale dye removal applications from industrial wastewater.