Microwave-assisted and methanol/acetic acid-free method for rapid staining of proteins in SDS-PAGE gels.

We describe a microwave-assisted, methanol and acetic acid-free, inexpensive method for rapid staining of SDS-PAGE proteins. Only citric acid, benzoic acid, and Coomassie brilliant blue G-250 (CBG) were used. Microwave irradiation reduced the detection duration, and proteins in a clear background were visualized within 30 min of destaining, after 2 min of fixing and 12 min of staining. By using this protocol, comparable band intensities were obtained to the conventional methanol/acetic acid method.

Smartphone-based dual inverse signal MOFs fluorescence sensing for intelligent on-site visual detection of malachite green.

The development of intelligent, sensitive, and visual methods for the rapid detection of veterinary drug residues is essential to ensure food quality and safety. Here, a smartphone-based dual inverse signal MOFs fluorescence sensing system was proposed for intelligent in-site visual detection of malachite green (MG). A UiO-66-NH2@RhB-dual-emission fluorescent probe was successfully synthesized in one step using a simple one-pot method. The inner filter effect (IFE) quenches the red fluorescence, while hydrogen bonding interaction enhances the blue fluorescence, enabling highly sensitive, accurate, and visual detection of MG dual inverse signals through fluorescence analysis. The probe showed great linearity over a wide range of 0.1-100 µmol/L, with a limit of detection (LOD) of 20 nmol/L. By integrating smartphone photography and RGB (red, green, and blue) analysis, accurate quantitative analysis of MG in water and actual fish samples can be achieved within 5 min. This developed platform holds great promise for the on-site detection of MG in practical applications, with the advantages of simplicity, cost-effectiveness, and rapidity. Consequently, it may open up a new pathway for on-site evaluation of food safety and environmental health.

Microalgae derived honeycomb structured mesoporous diatom biosilica for adsorption of malachite green: Process optimization and modeling.

The present study investigated the removal of malachite green dye from aquifers by means of microalgae-derived mesoporous diatom biosilica. The various process variables (dye concentration, pH, and adsorbent dose) influencing the removal of the dye were optimized and their interactive effects on the removal efficiency were explored by response surface methodology. The pH of the solution (pH = 5.26) was found to be the most dominating among other tested variables. The Langmuir isotherm (R2 = 0.995) best fitted the equilibrium adsorption data with an adsorption capacity of 40.7 mg/g at 323 K and pseudo-second-order model (R2 = 0.983) best elucidated the rate of dye removal (10.6 mg/g). The underlying mechanism of adsorption was investigated by Weber-Morris and Boyd models and results revealed that the film diffusion governed the overall adsorption process. The theoretical investigations on the dye structure using DFT-based chemical reactivity descriptors indicated that malachite green cations are electrophilic, reactive and possess the ability to accept electrons, and are strongly adsorbed on the surface of diatom biosilica. Also, the Fukui function analysis proposed the favorable adsorption sites available on the adsorbent surface.

Highly efficient degradation of basic dyes using gold-coated nature-based supermagnetic iron oxide nanoparticles as eco-friendly nanocatalysts.

Nowadays, organic dyes are prevalent components in wastewater discharges due to their extensive use in various industries, posing a significant threat to public health across different organisms. As a result, wastewater treatment has become an indispensable requirement. In this study, we synthesized supermagnetic iron oxide (Fe3O4 NPs) and gold-iron oxide bimetallic nanoparticles (Au@Fe3O4 BNPs) using an eco-friendly method that involved natural compounds extracted from brown Egyptian propolis. We employed UV-visible spectroscopy, FTIR, XRD, VSM, SEM, HRTEM, EDX, Zeta potential and XPS techniques to examine the optical characteristics, chemical structure, crystalline structure, magnetic properties, morphology, size, and chemical composition of these biosynthesized nanoparticles. Furthermore, these nanoparticles were used as nanocatalysts for the removal of cationic dyes. The photocatalytic results indicated high efficiency in the removal of methylene blue (MB), crystal violet (CV), and malachite green (MG) dyes from aqueous solutions using Fe3O4 NPs and Au@Fe3O4 BNPs. The removal rates of MB, CV, and MG were about 95.2% in 70 min, 99.4% in 50 min, and 96.2% in 60 min for Fe3O4 NPs, and 97.1% in 50 min, 99.1% in 30 min, and 98.1% in 50 min for Au@Fe3O4 BNPs, respectively. The study also assessed the potential anti-radical properties of the extract, Fe3O4 NPs, and Au@Fe3O4 BNPs using the DPPH assay, and the results demonstrated their antioxidant activity. Finally, these Fe3O4 NPs and Au@Fe3O4 BNPs have the potential to serve as efficient antioxidants and photocatalysts for removing basic dyes from water.

Super capacity of ligand-engineered biochar for sorption of malachite green dye: key role of functional moieties and mesoporous structure.

This study synthesized a new thiomalic acid-modified rice husk biochar (TMA-BC) as a versatile and eco-friendly sorbent. After undergoing chemical treatments, the mercerized rice husk biochar (NaOH-BC) and TMA-BC samples showed higher BET surface area values of 277.1 m2/g and 305.8 m2/g, respectively, compared to the pristine biochar (BC) sample, which had a surface area of 234.2 m2/g. In batch adsorption experiments, it was found that the highest removal efficiency for malachite green (MG) was achieved with TMA-BC, reaching 96.4%, while NaOH-BC and BC exhibited removal efficiencies of 38.6% and 27.9%, respectively, at pH 8. The engineered TMA-BC exhibited a super adsorption capacity of 104.17 mg/g for MG dye at pH 8.0 and 25 °C with a dosage of 2 g/L. The SEM, TEM, XPS, and FTIR spectroscopy analyses were performed to examine mesoporous features and successful TMA-BC carboxylic and thiol functional groups grafting on biochar. Electrostatic forces, such as π - π interactions, hydrogen bonding, and pore intrusion, were identified as key factors in the sorption of MG dye. As compared to single-solution adsorption experiments, the binary solution experiments performed at optimized dosages of undesired ions, such as humic acid, sodium dodecyl sulfate surfactant, NaCl, and NaSCN, reflected an increase in MG dye removal of 2.8%, 8.7%, 5.4%, and 12.7%, respectively, which was attributed to unique mesoporous features and grafted functional groups of TMA-BC. Furthermore, the TMA-BC showed promising reusability up to three cycles. Our study indicates that mediocre biochar modified with TMA can provide an eco-friendly and cost-effective alternative to commercially accessible adsorbents.

Decolorization and detoxication of malachite green by engineered Saccharomyces cerevisiae expressing novel thermostable laccase from Trametes trogii.

Malachite Green (MG) is a widely used industrial dye that is hazardous to health. Herein, the decolourisation and detoxification of MG were achieved using the engineered Saccharomyces cerevisiae expressing novel thermostable laccase lcc1 from Trametes trogii. The engineered strain RCL produced a high laccase activity of 121.83 U L-1. Lcc1 was stable at temperatures ranging from 20 ℃ to 60 ℃ and showed a high tolerance to organic solvents. Moreover, Lcc1 could decolorize different kinds of dyes (azo, anthraquinone and triphenylmethane), among which, the decolorization ability of MG is the highest, reaching 95.10 %, and the decolorization rate of other triphenylmethane dyes also over 50 %. The RCL decolorized about 95 % of 50 mg L-1 of MG dye in 10 h at 30 ℃. The MG degradation products were analyzed. The industrial application potential of the RCL was evaluated by treating industrial wastewater and the decolourisation rates were over 90 %.

Comparative study using indocyanine green and patent blue dye for sentinel lymph node biopsy in patients with early-stage cervical cancer.

BACKGROUND: Lymphatic involvement is the most important prognostic factor in early-stage cervical cancer. Sentinel lymph node biopsy is a viable alternative to systematic lymphadenectomy and may identify metastases more precisely. OBJECTIVE: To compare two tracers (indocyanine green and patent blue) to detect sentinel nodes. METHODS: A single-center, retrospective study of women treated due to early-stage cervical cancer (International Federation of Gynecology and Obstetrics 2009 IA1 with lymphovascular invasion, IA2, and IB1). Location and tracer of all detected sentinel nodes had been documented for a prospective, multicenter trial (SENTIX trial). All sentinel nodes were sent to frozen section and final analysis through ultrastaging using a standard protocol. RESULTS: Overall, 103 patients were included. Bilateral detection rate for indocyanine green (93.2%) was significantly higher than for blue dye (77.7%; p=0.004). Their combined use significantly increased the bilateral detection to 99.0% (p=0.031). While 97.4% of all sentinel nodes were located below the common iliac vessels, no para-aortic nodes were labeled. Simultaneous bilateral detection with both tracers was found in 71.8% of the cases, of which the sentinel nodes were identical in 91.9%. Nine positive nodes were detected among seven patients (6.8%), all marked with indocyanine green while patent blue labeled six. Frozen section failed to detect one of three macrometastases and three of four micrometastases (sensitivity 43%; negative prediction value 96%). CONCLUSION: Anatomical distribution and topographic localization of the sentinel nodes obtained with these tracers were not different. Indocyanine green provided a significantly higher bilateral detection rate and had superior sensitivity to detect positive nodes compared with patent blue. Combining indocyanine green and blue dye increased the bilateral detection rate significantly.

Tecoma stans floral extract-mediated synthesis of MgFe2O4/ZnO nanoparticles for adsorption and photocatalytic degradation of coomassie brilliant blue dye.

Toxic organic dyes-containing wastewater treatment by adsorption and photocatalytic techniques is widely applied, but adsorbents and photocatalysts are often synthesized through chemical methods, leading to secondary pollution by released chemicals. Here, we report a benign method using Tecoma stans floral extract to produce MgFe2O4/ZnO (MGFOZ) nanoparticles for adsorption and photocatalytic degradation of coomassie brilliant blue (CBB) dye. Green MGFOZ owned a surface area of 9.65 m2/g and an average grain size of 54 nm. This bio-based nanomaterial showed higher removal percentage and better recyclability (up to five cycles) than green MgFe2O4 and ZnO nanoparticles. CBB adsorption by MGFOZ was examined by kinetic and isotherm models with better fittings of Bangham and Langmuir or Temkin. RSM-based optimization was conducted to reach an actual adsorption capacity of 147.68 mg/g. Moreover, MGFOZ/visible light system showed a degradation efficiency of 89% CBB dye after 120 min. CBB adsorption can be controlled by both physisorption and chemisorption while •O2- and •OH radicals are responsible for photo-degradation of CBB dye. This study suggested that MGFOZ can be a promising adsorbent and catalyst for removal of organic dyes in water.

Crosslinked chitosan-montmorillonite composite and its magnetized counterpart for the removal of basic fuchsin from wastewater: Parametric optimization using Box-Behnken design.

Treating wastewater polluted with organic dyestuffs is still a challenge. In that vein, facile synthesis of a structurally simple composite of chitosan with montmorillonite (CS-MMT) using glutaraldehyde as a crosslinker and the magnetized analogue (MAG@CS-MMT) was proposed as versatile adsorbents for the cationic dye, basic Fuchsin (FUS). Statistical modeling of the adsorption process was mediated using Box-Behnken (BB) design and by varying the composite dose, pH, [FUS], and contact time. Characterization of both composites showed an enhancement of surface features upon magnetization, substantiating a better FUS removal of the MAG@CS-MMT (%R = 98.43 %) compared to CS-MMT (%R = 68.02 %). The surface area analysis demonstrates that MAG@CS-MMT possesses a higher surface area, measuring 41.54 m2/g, and the surface analysis of the magnetized nanocomposite, conducted using FT-IR and Raman spectroscopies, proved the presence of FeO peaks. In the same context, adsorption of FUS onto MAG@CS-MMT fitted-well to the Langmuir isotherm model and the maximum adsorption capacities (qm) were 53.11 mg/g for CS-MMT and 88.34 mg/g for MAG@CS-MMT. Kinetics investigation shows that experimental data fitted well to the pseudo-second order (PSO) model. Regeneration study reveals that MAG@CS-MMT can be recovered effectively for repeated use with a high adsorption efficiency for FUS.

Kinetic and adsorption isotherm studies of Malachite Green dye onto surfactant-tailored alginate hydrogel beads: An influence of surfactant hydrophobicity.

This study details the synthesis and characterization of surfactant-modified sodium alginate hydrogel beads crosslinked with Ba2+ ions through ionotropic gelation. Cationic surfactants such as, dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and butanediyl-α,ω-bis-(dimethyldodecylammonium bromide) (GEM), were employed in the modification process. The surfactant-modified ALG-DTAB, ALG-DDAB, and ALG-GEM beads were investigated for the removal of cationic dye Malachite Green (MG) to elucidate the impact of hydrophobicity of amphiphiles on the adsorption process. The characterizations were carried out using Rheometry, Field Emission Scanning Electron Microscopy (FESEM), Infrared Spectroscopy (IR), and Energy Dispersive X-ray Spectroscopy (EDX). Under optimized conditions, ALG-GEM and ALG-DDAB demonstrated highest maximum adsorption capacity (Qmax > 700 mgg-1). The adsorption data fitted well to pseudo-second order kinetic and Langmuir adsorption models, suggesting the involvement of chemisorption phenomena with notable contributions from pore diffusion. The effects of pH, initial dye concentration, adsorbent dose, temperature, and competing ions on the removal of MG were investigated. Interestingly, ALG-GEM beads exhibited an increase in adsorption capacity with rising pH and a subsequent decrease with increasing temperature, showcasing optimal adsorption at pH 7.0 and 25 °C. The study proposes that ALG beads modified with cationic surfactants with higher hydrophobicity could offer a promising avenue in wastewater treatment processes.

Symmetry-breaking malachite green as a near-infrared light-activated fluorogenic photosensitizer for RNA proximity labeling.

Cellular RNA is asymmetrically distributed in cells and the regulation of RNA localization is crucial for proper cellular functions. However, limited chemical tools are available to capture dynamic RNA localization in complex biological systems with high spatiotemporal resolution. Here, we developed a new method for RNA proximity labeling activated by near-infrared (NIR) light, which holds the potential for deep penetration. Our method, termed FAP-seq, utilizes a genetically encoded fluorogen activating protein (FAP) that selectively binds to a set of substrates known as malachite green (MG). FAP binding restricts the rotation of MG and rapidly activates its fluorescence in a wash-free manner. By introducing a monoiodo modification to MG, we created a photosensitizer (MG-HI) with the highest singlet oxygen generation ability among various MG derivatives, enabling both protein and RNA proximity labeling in live cells. New insights are provided in the transcriptome analysis with FAP-seq, while a deeper understanding of the symmetry-breaking structural arrangement of FAP-MG-HI was obtained through molecular dynamics simulations. Overall, our wash-free and NIR light-inducible RNA proximity labeling method (FAP-seq) offers a powerful and versatile approach for investigating complex mechanisms underlying RNA-related biological processes.

Biodegradation of malachite green by Pleurotus eryngii: a study on decolorization, mechanism, toxicity, and enzyme.

The purpose of this study was to investigate the biodegradation of malachite green (MG) by Pleurotus eryngii via decolorization. This study also explored the possible mechanisms and toxicity. The results indicated that this fungus exhibited strong decolorizing potential. MG degradation based on UPLC-TOF-Triple-MS analysis revealed the formation of intermediates such as 4-(dimethylamino)benzophenone, 4-(methylamino)benzophenone, and 4-(dimethylamino)phenol. Furthermore, a significant reduction in the toxicity of the degradation products was observed using the zebrafish animal model. A newly discovered dye-decolorizing peroxidase (DyP-PE) from P. eryngii was amplified, cloned, and expressed. The purified 56.4 kDa DyP-PE strongly decolorized MG, suggesting potentially application in the bioremediation of MG pollution. Thus, the DyP-PE derived from P. eryngii may contribute to the degradation of MG.

Interfacial interactions of polyethylene terephthalate microplastics and malachite green, tetracycline in aqueous environments.

Polyethylene terephthalate microplastics (PET-MPs) are one of pivotal nondegradable emerging pollutant. Here the variation of the surface physicochemical characteristics of PET-MPs with UV irradiation aging and the adsorption behaviors of PET-MPs in malachite green (MG), tetracycline (TC) solution and the effect of coexisting Cu(II) were comparatively investigated. The yellowing, weakened hydrophobicity, and increased surface negative charge, crystallinity degree and oxygen-containing functional groups were manifested specifically by the aged PET-MPs. Different from the single system, the hydrophobic interaction and metal ion bridging complexation dominated the adsorption of MG and TC, respectively, in the binary solution. While in the ternary solution, cationic ion competition of Cu(II) with MG decreased its capture, and the formation of PET-Cu(II)-TC ternary complexes promoted TC adsorption. Moreover, PET-MPs could serve as an efficient vector for MG and TC in MG/TC/Cu(II) ternary system, indicating PET-MPs tend to carry more varieties in the complex environment, that may increase the environmental risk of PET-MPs.

Single-Dose Radial Extracorporeal Shock Wave Therapy Modulates Inflammation During Meniscal Tear Healing in the Avascular Zone.

BACKGROUND: Extracorporeal shock wave therapy (ESWT) promotes tissue healing by modulating inflammation, which has implications for meniscal tear healing in the avascular zone. PURPOSE: To evaluate the effects of a single dose of radial ESWT on the healing process and inflammation of the meniscus and knee joints after meniscal tears in the avascular zone. STUDY DESIGN: Controlled laboratory study. METHODS: Avascular tears were induced in the medial meniscus (MM) of 72 Sprague-Dawley rats. One week postoperatively, the rats received a single session of radial ESWT with a Power+ handpiece (ESWT group; n = 36) or with a fake handpiece (sham-ESWT group; n = 36). The rats were then euthanized at 2, 4, or 8 weeks postoperatively. The MMs were harvested for analysis of healing (hematoxylin-eosin, safranin O-Fast Green, and collagen type 2 staining) and inflammation (interleukin [IL]-1ß and IL-6 staining). Lateral menisci and synovia were obtained to evaluate knee joint inflammation (enzyme-linked immunosorbent assay of IL-1ß and IL-6). Cartilage degeneration was assessed in the femurs and tibial plateaus using safranin O-Fast Green staining. RESULTS: The ESWT group showed significantly better meniscal healing scores than the sham-ESWT group at 4 (P = .0066) and 8 (P = .0050) weeks postoperatively. The IL-1ß level was significantly higher in the sham-ESWT group than in the ESWT group at 2 (MM: P = .0009; knee joint: P = .0160) and 8 (MM: P = .0399; knee joint: P = .0001) weeks. The IL-6 level was significantly lower in the sham-ESWT group than in the ESWT group at 2 (knee joint: P = .0184) and 4 (knee joint: P = .0247) weeks but higher at 8 weeks (MM: P = .0169; knee joint: P = .0038). The sham group had significantly higher osteoarthritis scores than the ESWT group at 4 (tibial plateau: P = .0157) and 8 (femur: P = .0048; tibial plateau: P = .0359) weeks. CONCLUSION: A single dose of radial ESWT promoted meniscal tear healing in the avascular zone, modulated inflammatory factors in the menisci and knee joints in rats, and alleviated cartilage degeneration. CLINICAL RELEVANCE: Radial ESWT can be considered a potential option for improving meniscal tear healing in the avascular zone because of its ability to modulate inflammation.

Evaluating the persistence of malachite green residues in tilapia and pacu fish.

Although banned in food-producing animals, residues of malachite green (MG) and its primary metabolite, leucomalachite green (LMG), have been found in fish due to illegal use in aquaculture and the release of industrial wastewater, which represent a serious risk to food and environmental securities. This study aimed to investigate the residue depletion profile of MG and LMG in edible tissues of Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) cultured simultaneously under the same environmental conditions to support control measures in case of abuse. An analytical method involving QuEChERS sample preparation and liquid chromatography coupled to tandem mass spectrometry was developed, validated, and applied to quantify MG and LMG residues in fish fillets from two depletion experiments after treatment by immersion bath (MG at 0.10 mg L-1 for 60 min). During the experiment, the average water temperature was 30 ºC, while the pH was 6.9. The method is selective, precise (CV = 0.4 - 22%) and accurate (recovery 92 - 114%). The limits of detection and quantification are 0.15 and 0.5 ng g-1, respectively. In both species, the sum of MG and LMG residues were quantified up to the 32nd day post-exposure, and the concentrations were significantly higher in the pacu fillets (up to 3284 ng g-1) than in Nile tilapia (up to 432 ng g-1). The sums of MG and LMG residues were below 2 ng g-1 at 44 days and 342 days for Nile tilapia and pacu, respectively - the Minimum Required Performance Limit (MRPL) for analytical methods intended to monitor forbidden substances in food according to old European Commission guidelines. The persistence of MG residues in pacu may be attributed to its higher lipid content, which favors the accumulation of the non-polar metabolite LMG. These results provide insights into the concern about human, animal, and environmental health risks resulting from unauthorized use or aquatic contamination by industrial wastewater containing MG residues.

Visualization and development of colorimetric loop-mediated isothermal amplification for the rapid detection and diagnosis of paramphistome infection: colorimetric PAR-LAMP.

Colorimetric detection can be applied to differentiate between positive and negative conditions. It can be coupled with loop-mediated isothermal amplification to diagnose rumen fluke or paramphistome infection, also called colorimetric PAR-LAMP. This study conducted LAMP using three candidate indicator dyes, namely malachite green (MLG), methyl green (MTG), and neutral red (NTR), and the results were observed by the naked eye. The dye concentration was optimized to obtain the most pronounced positive-negative result discrimination. Subsequently, we conducted target sensitivity tests using the DNA of Fischoederius elongatus at different concentrations. To validate the detection accuracy, the result was confirmed by gel electrophoresis. The sensitivity test presented the lowest detectable DNA concentration or limit of detection (LOD), with 1 pg for MLG, 0.5 ng for MTG, and 50 pg for NTR. Different LODs revealed inhibition of LAMP reaction and reduced efficiency of result presentation for colorimetric-based detection, particularly NTR and MTG. For MLG-LAMP, we observed no cross-reaction of non-target DNA and improved reaction with the DNA of Fischoederius cobboldi and Calicophoron sp., with multi-detection. In addition, naked eye observation and agarose gel electrophoresis (AGE) evaluation of the MLG-LAMP results showed a moderate and strong agreement with LAMP-AGE and microscopic examinations. Based on our results, colorimetric PAR-LAMP is a rapid, comfortable, and point-of-care procedure for the diagnosis of paramphistome infection.

pH-dependent and whole-cell catalytic decolorization of dyes using recombinant dye-decolorizing peroxidase from Rhodococcus jostii.

Dyes in wastewater have adverse effects on the environment and human health. Dye-decolorizing peroxidase (DyP) is a promising biocatalyst to dyes degradation, but the decolorization rates varied greatly which influencing factors and mechanisms remain to be fully disclosed. To explore an effective decolorizing approach, we have studied a DyP from Rhodococcus jostii (RhDyPB) which was overexpressed in Escherichia coli to decolorize four kinds of dyes, Reactive blue 19, Eosin Y, Indigo carmine, and Malachite green. We found the decolorization rates of the dyes by purified RhDyPB were all pH-dependent and the highest one was 94.4% of Malachite green at pH 6.0. ESI-MS analysis of intermediates in the decolorization process of Reactive blue 19 proved the degradation was due to peroxidase catalysis. Molecular docking predicated the interaction of RhDyPB with dyes, and a radical transfer reaction. In addition, we performed decolorization of dyes with whole E. coli cell with and without expressing RhDyPB. It was found that decolorization of dyes by E. coli cell was due to both cell absorption and degradation, and RhDyPB expression improved the degradation rates towards Reactive blue 19, Indigo carmine and Malachite green. The effective decolorization of Malachite green and the successful application of whole DyP-overexpressed cells in dye decolorization is conducive to the bioremediation of dye-containing wastewaters by DyPs.

The Feulgen reaction: from pink-magenta to rainbow fluorescent at the Maffo Vialli's School of Histochemistry.

For over a century, Palazzo Botta (Palace Botta) has housed the University of Pavia's Biomedical Institutes. Illustrious scientists have conducted research and taught at this Palace, making significant contributions to the advancement of natural, biological, and medical science. Among them, Camillo Golgi received the Nobel Prize for discovering the so-called "black reaction." Following Golgi, the Palace continued to be a hub for the development of methodologies and reactions aimed at detecting and quantifying biological components. Maffo Vialli (in the Golgi stream) was the first to establish a Histochemistry Research Group, which began in the naturalistic field and later expanded to the biomedical area. Among the many histochemical studies initiated in the Palace, the Feulgen reaction undoubtedly played a significant role. This reaction, developed R. Feulgen and H. Rossenbeck in 1924, had significant international implications: numerous researchers then contributed to define its fine chemical details, which remained the subject of study for years, resulting in a massive international scientific literature. The Pavia School of Histochemistry also contributed to the evolution and application of this method, which has become a true benchmark in quantitative histochemistry. Giovanni Prenna and the CNR Centre for Histochemistry made significant contributions, as they were already focused on fluorescence cytochemistry. The Pavia researchers made significant contributions to the development of methodology and, in particular, instrumentation; the evolution of the latter resulted in the emergence of flow cytometry and an ever-increasing family of fluorescent probes, which somewhat overshadowed the Feulgen reaction for DNA quantification. The advent of monoclonal antibodies then contributed to the final explosion of flow cytometry in clinical application, almost making young neophytes forget that its roots date back to Feulgen.

Background-Free and Reversible Upconversion Hydrogel Sensing Platform for Visual Monitoring of Sulfite.

Excessive sulfite usage in food and pharmaceutical production causes respiratory and neurological diseases, underscoring the need for a sensitive and rapid quantification strategy. The portable sensing platform based on a luminescent hydrogel sensor is a powerful tool for the on-site, real-time detection of sulfite ions. However, the lack of recyclability in almost all reaction-based hydrogel sensors increases the application cost. This study constructed a reversible and upconversion nanoprobe combining upconversion nanoparticles (UCNPs) and pararosaniline (PAR) for sulfite detection. The upconversion nanoprobe was further encapsulated in a three-dimensional polyacrylamide hydrogel matrix to create a background-free, reversible hydrogel sensor. The near-infrared excitation of UCNPs avoids the autofluorescence in the hydrogel and real samples. Meanwhile, PAR serves as a specific recognition unit for sulfite ions. After the addition of sulfites, a specific reaction occurs between PAR and sulfites, leading to the recovery of characteristic emission at 540 nm, achieving sensitive detection of sulfite ions. Importantly, this specific reaction is reversible under thermal treatment, allowing the hydrogel sensor to return to its initial state and thus enabling reversible detection of sulfite ions. Furthermore, a portable sensing platform is developed to realize point-of-care, real-time quantitative detection of sulfite ions. The proposed upconversion reversible hydrogel sensor provides a new sensing strategy for the detection of hazardous substances in food and offers new insights into the preparation of reversible, highly sensitive hydrogel sensors.

Cobalt oxyhydroxide nanosheet-modulated ratiometric fluorescence platform for the selective detection of malachite green in fish.

A ratiometric fluorescence platform was developed based on the cobalt oxyhydroxide (CoOOH) nanosheet-modulated fluorescence response of blue emissive copper nanoclusters (Cu NCs) and yellow emissive o-phenylenediamine (OPD). CoOOH nanosheets showed dual function of strong absorption and oxidation ability, which can effectively quench the blue fluorescence of Cu NCs, with an excitation and emission peak maximum at 390 and 450 nm, respectively , and transfer the OPD into yellow fluorescence products, with an excitation and emission peak maximum at 390 and 560 nm, respectively. Upon introducing butyrylcholinesterase (BChE) and its substrates, CoOOH nanosheets were decomposed into Co2+, and malachite green (MG) showed strong inhibition ability to this  process. This resulted in the obvious difference on the ratio of blue and yellow fluorescence recorded on the system in the presence and absence of MG, which was utilized for the quantitative detection of MG, with a limit of detection of 0.140 µM and a coefficient of variation of 3.5%. The fluorescence ratiometric assay showed excellent detection performances in practical sample analysis.