Fluorescence Assay Research Articles

Novel Mechanisms of Strigolactone-Induced DWARF14 Degradation in Arabidopsis thaliana.

In angiosperms, the strigolactone (SL) receptor is the α/β hydrolase DWARF14 (D14) that, upon SL binding, undergoes conformational changes, triggers SL-dependent responses and hydrolyses SLs. SL signalling involves the formation of a complex between SL-bound D14, the E3-ubiquitin ligase SCFMAX2 and the transcriptional corepressors SMXL6/7/8, which become ubiquitinated and degraded by the proteasome. SL also destabilises the D14 receptor. The current model proposes that D14 degradation occurs after SMXLs ubiquitination via SCFMAX2 and proteasomal degradation. Using fluorescence and luminescence assays on transgenic lines expressing D14 fused to GREEN FLUORESCENT PROTEIN or LUCIFERASE, we showed that SL-induced D14 degradation may also occur independently of SCFMAX2 and/or SMXL6/7/8 through a proteasome-independent mechanism. Furthermore, SLs hydrolysis was not essential for triggering either D14 or SMXL7 degradation. The activity of mutant D14 proteins predicted to be non-functional for SL signalling was also examined, and their capability to bind SLs in vitro was studied using Differential Scanning Fluorimetry. Finally, we found that under certain conditions, the efficiency of D14 degradation was not aligned with that of SMXL7 degradation. These findings suggest a more complex regulatory mechanism governing D14 degradation than previously anticipated and provide novel insights into the dynamics of SL signalling in Arabidopsis.

Genetic Evidence of SpGH9A3 in Leaf Morphology Variation of Spathiphyllum 'Mojo'.

Leaves play a crucial role as ornamental organs in Spathiphyllum, exhibiting distinct differences across various Spathiphyllum varieties. Leaf development is intricately linked to processes of cell proliferation and expansion, with cell morphology often regulated by plant cell walls, primarily composed of cellulose. Alterations in cellulose content can impact cell morphology, subsequently influencing the overall shape of plant organs. Although cellulases have been shown to affect cellulose levels in plant cells, genetic evidence linking them to the regulation of leaf shape remains limited. This study took the leaves of Spathiphyllum 'Mojo' and its somatic variants as the research objects. We screened four cellulase gene family members from the transcriptome and then measured the leaf cellulose content, cellulase activity, and expression levels of cellulase-related genes. Correlation analysis pinpointed the gene SpGH9A3 as closely associated with leaf shape variations in the mutant. Green fluorescent fusion protein assays revealed that the SpGH9A3 protein was localized to the cell membrane. Notably, the expression of the SpGH9A3 gene in mutant leaves peaked during the early spread stage, resulting in smaller overall leaf size and reduced cellulose content upon overexpression in Arabidopsis.

Discovery of Inhibitors Targeting Protein-Protein Interaction between Bacterial RNA Polymerase and NusG as Novel Antimicrobials.

Bacterial RNA polymerase (RNAP), the core enzyme responsible for bacterial transcription, requires the NusG factor for efficient transcription elongation and termination. As the primary binding site for NusG, the RNAP clamp-helix (CH) domain represents a potential protein-protein interaction (PPI) target for novel antimicrobial agent design and discovery. In this study, we designed a pharmacophore model based on the essential amino acids of the CH for binding to NusG, such as R270, R278, and R281 (Escherichia coli numbering), and identified a hit compound with mild antimicrobial activity. Subsequent rational design and synthesis of this hit compound led to improved antimicrobial activity against Streptococcus pneumoniae, with the minimum inhibitory concentration (MIC) reduced from 128 to 1 μg/mL. Additional characterization of the antimicrobial activity, inhibitory activity against RNAP-NusG interaction, and cell-based transcription and fluorescent assays of the optimized compounds demonstrated their potential for further lead optimization.

Reversal of P-glycoprotein Mediated Multidrug Resistance in MCF-7/R Cancer Cells by Esculetin Derivatives: Experimental and MD Simulation Studies

Coumarins of natural origin have been explored as potential inhibitors of P-glycoprotein (P-gp). Esculetin which belongs to the class of coumarin has been derivatized with known hydrazine pharmacophores viz; benzoyl hydrazine (BH), isonicotinyl hydrazine (INH), and hydrazino benzoic acid. The homology modeling approach was used to predict the three-dimensional structure of human P-gp. An <i>in-silico</i> study has been performed for the structural insight into the molecular mechanism of P-gp inhibition of the esculetin derivatives by molecular docking (MD) and simulation studies. The cell cytotoxic activities of the synthesized compounds were evaluated using in-vitro studies. The sublines resistant doxorubicin (MCF-7/R) were generated and the activities of P-gp proteins were estimated using fluorescent dye accumulation assays. The E-BH showed promising P-gp inhibitory activity and cell cytotoxicity against MCF7 and MCF7/R (resistant) breast cancer cell lines. In line with experimental observations, the E-BH (Esculetin benzoyl hydrazine) has yielded the lowest energy stable complex with P-gp and is stabilized by intermolecular hydrogen bonding and more hydrophobic interactions during 100 ns of simulation. This suggested that the activity of P-gp is probably controlled by hydrophobic interactions. Performed experimental and computational studies has helped to elucidate the mechanism of P-gp inhibition by E-BH. Thus, amongst the three derivatives; E-BH exhibits greater efficacy in blocking the efflux mechanism.

Development of RPA-Cas12a assay for rapid and sensitive detection of Pneumocystis jirovecii

Pneumocystis jirovecii is a prevalent opportunistic fungal pathogen that can lead to life-threatening Pneumocystis pneumonia in immunocompromised individuals. Given that timely and accurate diagnosis is essential for initiating prompt treatment and enhancing patient outcomes, it is vital to develop a rapid, simple, and sensitive method for P. jirovecii detection. Herein, we exploited a novel detection method for P. jirovecii by combining recombinase polymerase amplification (RPA) of nucleic acids isothermal amplification and the trans cleavage activity of Cas12a. The factors influencing the efficiency of RPA and Cas12a-mediated trans cleavage reaction, such as RPA primer, crRNA, the ratio of crRNA to Cas12a and ssDNA reporter concentration, were optimized. Our RPA-Cas12a-based fluorescent assay can be completed within 30–40 min, comprising a 25–30 min RPA reaction and a 5–10 min trans cleavage reaction. It can achieve a lower detection threshold of 0.5 copies/µL of target DNA with high specificity. Moreover, our RPA-Cas12a-based fluorescent method was examined using 30 artificial samples and demonstrated high accuracy with a diagnostic accuracy of 93.33%. In conclusion, a novel, rapid, sensitive, and cost-effective RPA-Cas12a-based detection method was developed and demonstrates significant potential for on-site detection of P. jirovecii in resource-limited settings.

In vitro antiplasmodial and anticancer analyses of endophytic fungal extracts isolated from selected Nigerian medicinal plants

Ethnomedicinal plants are thought to have better prospects of harboring endophytes that produce natural products with pharmacological activities. This study aimed to investigate the antiplasmodial and anticancer properties of secondary metabolites of endophytic fungi from three medicinal plants. The endophytic fungi included Lasiodiplodia theobromae isolated from Cola acuminata, Curvularia lunata Bv4 isolated from Bambusa vulgaris, and Curvularia lunata Eg7 isolated from Elaeis guineensis. The identification of the fungi was based on the internal transcribed spacer (ITS-rDNA) sequence. The fungi were subjected to solid-state fermentation and the secondary metabolites were extracted with ethyl acetate. In vitro antiplasmodial screening of extracts was performed using the SYBR green I-based fluorescence assay on the chloroquine-resistant Plasmodium falciparum strain DD2. The cytotoxicity of the extracts on human red blood cells and Jurkat (leukemia) cells was assessed using the tetrazolium-based colorimetric MTT assay. Gas chromatography-mass spectrometry (GC–MS) analysis was used to identify the constituents of the fungal extracts. The extract of L. theobromae showed the best antiplasmodial activity against chloroquine-resistant P. falciparum (IC50 = 5.4 µg/mL) and was not harmful to erythrocytes (CC50 > 100 µg/mL). All three fungal extracts showed a weak cytotoxic effect against Jukart cell lines (CC50 > 100 µg/mL). GC–MS analysis of the three endophytic fungal extracts revealed the presence of forty major bioactive compounds, including: oxalic acid, isobutyl nonyl ester, 2,4-di-tert-butylphenol, and hexadecanoic acid, among others. The endophytic fungi from the medicinal plants in this study were promising sources of bioactive compounds that could be further evaluated as novel drugs for the treatment of malaria caused by P. falciparum-resistant strains.

Assessment In vitro and In silico of the Activity of Thiadiazines as NorA Efflux Pump Inhibitors.

Antimicrobials fight microorganisms, preventing and treating infectious diseases. However, antimicrobial resistance (AMR) is a growing concern due to the inappropriate and excessive use of these drugs. Several mechanisms can lead to resistance, including efflux pumps such as the NorA pump in Staphylococcus aureus, which reduces the effectiveness of fluoroquinolones. Thiadiazines are heterocyclic compounds whose chemical structure resembles that of cephalosporins. Therefore, these compounds and their derivatives have been studied for their potential in combating increased bacterial resistance. To analyze this hypothesis, direct activity assays, antibiotic action-modifying activity, fluorescence assays to evaluate the retention of ethidium bromide inside bacteria, and molecular docking were carried out. These experiments involved serial dilutions in microplates against Staphylococcus aureus strain 1199B under the influence of six thiadiazine derivatives (IJ10, IJ11, IJ21, IJ22, IJ23, and IJ25). The tests revealed that, despite not showing effective direct activity, some thiadiazine derivatives (IJ11, IJ21, and IJ22) inhibited the function of the bromide pump both in microdilution tests and in fluorescence and docking assays. Particularly, the IJ11 compound stood out for its activity similar to efflux inhibitors, as well as its inhibition of the norfloxacin pump of this bacterium. Among the results of this study, it deserves to be highlighted for anchoring future experiments, as it represents the first investigation of this group of thiadiazine derivatives against the NorA pump.

Concentration effect of zinc ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment revealed by Raman spectroscopy

Accumulation of Zn2+ ions in protein aggregates has been suggested to be a key factor in Alzheimer’s disease etiology. However, the specific influence of Zn2+ ions on the formation of amyloid fibrils or amorphous aggregates is still much debated. Herein, we conducted a combined study of Raman spectroscopy, UV–vis absorption spectroscopy and ThT fluorescence assay on the concentration effects of Zn2+ ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment. The addition of Zn2+ ions showed a negligible effect on unfolding of the protein tertiary structures and nucleation pathways on amyloid fibrillation. In contrast, a distinct concentration-dependence was observed for the influence of Zn2+ ions on the transformation of lysozyme secondary structures. At low concentration, the metal ions do not affect the populations of major secondary structures in the final state after incubation, while they at high concentration exhibit a promotion effect on the transformation from α-helix to β-sheet-like structures. These findings provide insights into the multifaceted impact of Zn2+ ions on protein aggregation, shedding light on potential therapeutic strategies for neurodegenerative diseases.

Antibody-Based Array for Tacrolimus Immunosuppressant Monitoring with Planar Plastic Waveguides Activated with an Aminodextran-Lipase Conjugate.

Cyclic olefin copolymers (COC; e.g., Zeonor, Topas, Arton, etc.) are materials with outstanding properties for developing point-of-care systems; however, the lack of functional groups in their native form makes their application challenging. This work evaluates different strategies to functionalize commercially available Zeonor substrates, including oxygen plasma treatment, photochemical grafting, and direct surface amination using an amino dextran-lipase conjugate (ADLC). The modified surfaces were characterized by contact angle measurements, Fourier transform infrared-attenuated total reflection analysis, and fluorescence assays based on evanescent wave excitation. The bioaffinity activation through the ADLC approach results in a fast, simple, and reproducible approach that can be used further to conjugate carboxylated small molecules (e.g., haptens). The usefulness of this approach has been demonstrated by the development of a heterogeneous fluorescence immunoassay to detect tacrolimus (FK506) immunosuppressant drug using an array biosensor platform based on evanescence wave laser excitation and Zeonor-ADLC substrates. Surface modification with ADLC-bearing FK506 provides a 3D layer that efficiently leads to a remarkably low limit of detection (0.02 ng/mL) and IC50 (0.9 ng/mL) together with a wide dynamic range (0.07-11.3 ng/mL).

Small Molecule Induces Time-Dependent Inhibition of Stat3 Dimerization and DNA-Binding Activity and Regresses Human Breast Tumor Xenografts.

Aberrantly-active signal transducer and activator of transcription (Stat)3 has a causal role in many human cancers and represents a validated anticancer drug target, though it has posed significant challenge to drug development. A new small molecule, JKB887, was identified through library screening and is predicted to interact with Lys591, Arg609 and Pro63 in the phospho-tyrosine (pTyr)-binding pocket of the Stat3 SH2 domain. JKB887 inhibited Stat3 DNA-binding activity in vitro in a time-dependent manner, with IC50 of 2.2-4.5 μM at 30-60-min incubation. It directly disrupted both the Stat3 binding to the cognate, high-affinity pTyr (pY) peptide, GpYLPQTV-NH2 in fluorescent polarization assay with IC50 of 3.5-5.5 μM at 60-90-min incubation, and to the IL-6 receptor/gp130 or Src in treated malignant cells. Treatment with JKB887 selectively blocked constitutive Stat3 phosphorylation, nuclear translocation and transcriptional activity, and Stat3-regulated gene expression, and decreased viable cell numbers, cell growth, colony formation, migration, and survival in human or mouse tumor cells. By contrast, JKB887 had minimal effects on Stat1, pErk1/2MAPK, pShc, pJAK2, or pSrc induction, or on cells that do not harbor aberrantly-active Stat3. Additionally, JKB887 inhibited growth of human breast cancer xenografts in mice. JKB887 is a Stat3-selective inhibitor with demonstrable antitumor effects against Stat3-dependent human cancers.

Quantifying the viability of lactic acid bacteria using ratiometric fluorescence assays

Quantifying the viability of lactic acid bacteria (LAB) has become an important task in evaluating the quality, function and storage condition of LAB products. Propidium iodide (PI), as a DNA-binding dye that penetrates only dead bacteria, has been widely used for LAB viability assessments. However, high fluorescence background from live LAB was frequently occurred during PI-based staining, which led to the low sensitivity in probing minor amounts of dead LAB in a dead/live mixture. Here, we found that PI could be adsorbed nonspecifically in LAB periplasm, which contributed to the high fluorescence background of live LAB. CaCl2 was used to reduce this nonspecific adsorption and increase the fluorescence ratio of dead to live LAB. Combined with SYTO 9 (a membrane permeable dye) for double-staining, a ratiometric fluorescent method that could probe dead LAB at a ratio as low as 0.2 % was established. Using Lacticaseibacillus casei as a LAB model, an allometric correlation between the ratiometric fluorescence and theoretical ratio of live to dead LAB was acquired, with a correlation coefficient R2 of 0.993. The as-developed method was successfully applied to the viability assessment of LAB stored in different environments. We believe it would have practical applications in LAB food industry for quality management and control.

The role of SEMG1 overexpression in OSCC tumorigenesis and its relation with metabolic molecules.

This study aimed to investigate the expression and biological significance of Semenogelin 1 (SEMG1), a member of the cancer-testis antigen family, in oral squamous cell carcinoma (OSCC). Further, we explored its potential association with metabolism-related molecules. SEMG1 expression levels in OSCC were determined through immunohistochemistry, flow cytometry, and Western blot analyses. To decipher the biological implications of SEMG1 in OSCC, the CAL27 OSCC cell line was either stably overexpressed with SEMG1 or subjected to SEMG1-shRNA knockdown. The relationship between clinicopathological parameters and SEMG1 expression in OSCC patients was also assessed. SEMG1 was found to be overexpressed in OSCC, though its expression was not influenced by the pathological grade. The fluorescent dihydroethidium assay indicated that SEMG1 augmented reactive oxygen species production. The mitochondrial membrane potential assay suggested a significant upregulation of mitochondrial membrane potential by SEMG1. Cell cycle assessments highlighted that SEMG1 overexpression led to a notable rise in cells entering the S-phase. Additionally, a strong correlation between SEMG1 expression and both ENO1 and PKM2 expression in OSCC was observed. The findings underscore the elevated expression of SEMG1 in OSCC and its contributory role in the tumorigenesis of OSCC patients.

Fluorescence immunochromatographic detection of antibodies to the p72 protein of African swine fever virus

The African swine fever virus (ASFV), a highly contagious pathogen responsible for African swine fever (ASF), causes significant economic losses in the global pork industry. Due to its large and complex structure, ASFV remains refractory to commercial vaccine development, necessitating the creation of rapid, sensitive, and specific diagnostic tools for disease control. In this study, quantum dots were conjugated to ASFV p72 protein to establish a fluorescent immunochromatographic assay for detecting ASFV-specific antibodies. The assay test strips contained four adjacent pads arranged sequentially: a sample-application pad, a pad containing mobile antigen-probe conjugate, a nitrocellulose readout pad featuring a test line containing immobilised staphylococcal protein A and a control line containing immobilised monoclonal antibodies against the ASFV p72 protein, and an absorbent pad driving the directional flow of liquid via capillary action. The resulting fluorescence immunochromatographic assay demonstrated highly sensitive and specific ASFV antibody detection in under 15 min. Specificity testing showed no cross-reactivity with serum antibodies against other viruses and sensitivity surpassing that of commercial ASFV antibody colloidal gold immunochromatographic test strips. This novel approach offers rapid detection, excellent specificity, and high sensitivity, and supports the future development of fluorescent immunochromatographic test strips for ASFV antibody detection.

A Cationic Zn-Phthalocyanine Turns Alzheimer's Amyloid β Aggregates into Non-Toxic Oligomers and Inhibits Neurotoxicity in Culture.

Amyloid β peptide (Aβ) aggregation and deposition are considered the main causes of Alzheimer's disease. In a previous study, we demonstrated that anionic Zn-phthalocyanine (ZnPc) can interact with the Aβ peptide and inhibit the fibril-formation process. However, due to the inability of anionic ZnPc to cross the intact blood-brain barrier, we decided to explore the interaction of cationic methylated Zn-phthalocyanine (cZnPc) with the peptide. Using a ThT fluorescence assay, we observed that cZnPc dose-dependently and time-dependently inhibited Aβ1-42 fibril levels under in vitro fibril-formation conditions. Electron microscopy revealed that it caused Aβ1-42 peptides to form small aggregates. Western blotting and dot immunoblot oligomer experiments demonstrated that cZnPc increased rather than decreased the levels of oligomers from the very early stages of incubation. A binding assay confirmed that cZnPc could bind with the peptide. Docking simulations indicated that the oligomer species of Aβ1-42 had a higher ability to interact with cZnPc. ANS fluorescence assay results indicated that cZnPc did not affect the hydrophobicity of the peptide. However, cZnPc significantly increased intrinsic tyrosine fluorescence of the peptide after 8 h of incubation in fibril-formation conditions. Importantly, cell culture experiments demonstrated that cZnPc did not exhibit any toxicity up to a concentration of 10 µM. Instead, it protected a neuronal cell line from Aβ1-42-induced toxicity. Thus, our results suggest that cZnPc can affect the aggregation process of Aβ1-42, rendering it non-toxic, which could be crucial for the therapy of Alzheimer's disease.

Synthesis and mechanistic study of Aβ42 C-terminus domain derived tetrapeptides that inhibit Alzheimer’s Aβ-aggregation-induced neurotoxicity

Amyloid plaque formation in the brain is mainly responsible for the onset of Alzheimer’s disease (AD). Structure-based peptides have gained importance in recent years, and rational design of the peptide sequences for the prevention of Aβ-aggregation and related toxicity is imperative. In this study, we investigate the structural modification of tetrapeptides derived from the hydrophobic C-terminal region of Aβ42 “VVIA-NH2” and its retro-sequence “AIVV-NH2.” A preliminary screening of synthesized peptides through an MTT cell viability assay followed by a ThT fluorescence assay revealed a peptide 13 (Ala-Ile-Aib-Val-NH2) that showed protection against Aβ-aggregation and associated neurotoxicity. The presence of the α-helix inducer “Aib” in peptide 13 manifested the conformational transition from cross-β-sheets to α-helical content in Aβ42. The absence of fibrils in electron microscopic analysis suggested the inhibitory potential of peptide 13. The HRMS, DLS, and ANS studies further confirmed the inhibitory activity of 13, and no cytotoxicity was observed. The structure-based peptide described herein is a promising amyloid-β inhibitor and provides a new lead for the development of AD therapeutics.

ShRNA-Targeting Caspase-3 Inhibits Cell Detachment Induced by Pemphigus Vulgaris Autoantibodies in HaCaT Cells.

Pemphigus is an autoimmune disease that affects the skin and mucous membranes, induced by the deposition of pemphigus IgG, which mainly targets desmogleins 1 and 3 (Dsg1 and 3). This autoantibody causes steric interference between Dsg1 and 3 and the loss of cell adhesion, producing acantholysis. This molecule and its cellular effects are clinically reflected as intraepidermal blistering. Pemphigus vulgaris-IgG (PV-IgG) binding involves p38MAPK-signaling-dependent caspase-3 activation. The present work assessed the in vitro effect of PV-IgG on the adherence of HaCaT cells dependent on caspase-3. PV-IgG induced cell detachment and apoptotic changes, as demonstrated by annexin fluorescent assays. The effect of caspase-3 induced by PV-IgG was suppressed in cells pre-treated with caspase-3-shRNA, and normal IgG (N-IgG) as a control had no relevant effects on the aforementioned parameters. The results demonstrated that shRNA reduces caspase-3 expression, as measured via qRT-PCR and via Western blot and immunofluorescence, and increases cell adhesion. In conclusion, shRNA prevented in vitro cell detachment and the late effects of apoptosis induced by PV-IgG on HaCaT cells, furthering our understanding of the molecular role of caspase-3 cell adhesion dependence in pemphigus disease.

Activation of CB2 Receptors by (-)-Cannabichromene but Not (+)-Cannabichromene.

Introduction: Cannabichromene (CBC) is a minor constituent of cannabis that is a selective cannabinoid CB2 receptor agonist and activator of TRPA1. To date, it has not been shown whether (-)-CBC, (+)-CBC, or both can mediate these effects. In this study, we investigate the activity of the CBC enantiomers at CB1, CB2, and Transient receptor potential ankyrin 1 (TRPA1) receptors in vitro. Materials and Methods: CBC enantiomers were purified from synthetic CBC by chiral chromatography, and their optical activity was confirmed by spectroscopy. Human CB1 and CB2 receptor activity was measured using a fluorescent assay of membrane potential in stably transfected AtT20 cells. TRPA1 activation was measured using a fluorescent assay of intracellular calcium in stably transfected HEK293 cells. Results: The (-)-CBC activated CB2 with an EC50 of 1.5 µM, to a maximum of 60% of (-)CP55940. (+)-CBC did not activate CB2 at concentrations up to 30 µM. Only 30 µM (-)-CBC produced detectable activation of CB1, (+)-CBC was inactive. Both (-)-CBC and (+)-CBC activated TRPA1; at 30 µM (-)-CBC produced an activation 50% of that of the reference agonist cinnamaldehyde (300 µM), 30 µM (+)-CBC activated TRPA1 to 38% of the cinnamaldehyde maximum. Discussion: It is unclear whether (-)-CBC is the sole or even the predominant enantiomer of CBC enzymatically synthesized in cannabis. This study shows that (-)-CBC is the active isomer at CB2 receptors, while both isomers activate TRPA1. The results suggest that medicinal preparations of CBC that target cannabinoid receptors would be most effective when (-)-CBC is the dominant isomer.

Isolation of porcine circovirus 3 using primary porcine bone marrow-derived cells

Porcine circovirus 3 (PCV3) was first reported in the United States in 2016; this virus is considered to be involved in diverse pathologies, such as multisystem inflammation, porcine dermatitis and nephropathy syndrome, and reproductive disorders. However, successful isolation of PCV3 using cultured cells has been rare. In this study, we aimed to isolate PCV3 using primary porcine bone marrow-derived cells. Mononuclear cells were isolated from the femur bones of clinically healthy pigs. These primary cells were cultured for 6–10 days post-seeding and infected with PCV3-containing tissue homogenates. The cells were cultured for up to 37 days, and the culture medium was changed every 3–4 days. The growth curve of PCV3 in porcine bone marrow cells revealed a decline in growth during the first 10 days post-infection, followed by an increase leading to > 1010 genomic copies/mL of the cell culture supernatant; moreover, the virus was capable of passaging. The indirect fluorescent antibody assay for PCV3 infection revealed the presence of PCV3 capsid protein in the cytoplasm and nuclei of infected cells. Bone marrow cells were passaged for more than 20 generations (over 5 months), and PCV3 persistently infected the cells. PCV3-infected bone marrow cells expressed mesenchymal markers. These results reflect that primary porcine bone marrow-derived mesenchymal cells are permissive to PCV3 and continuously replicate a high copy number of the PCV3 genome. These findings regarding the high replication rate of PCV3 in bone marrow-derived mesenchymal cells could enhance our understanding of PCV3 pathogenicity.

Three-Dimensional Visualization of Breast Cancer Pathology Evolution in Clinical Patient Tissues with NIR-II Imaging.

Breast cancer (BC) is the most common tumor worldwide and requires crucial molecular typing for treatment and prognosis assessment. Currently, approaches like pathological staining, immunohistochemistry (IHC), and immunofluorescence (IF) face limitations due to the low signal-to-background ratio (SBR) and high tumor heterogeneity, resulting in a high misdiagnosis rate. Fluorescent assay in the second near-infrared region (NIR-II, 1000-1700 nm) exhibits ultrahigh SBR owing to diminished scattering and tissue autofluorescence. Here, we present a NIR-II strategy for accurate BC molecular typing and three-dimensional (3D) visualization based on the atomically precise fluorescent Au24Pr1 clusters. Single-atom Pr doping results in 3.9-fold fluorescence enhancement and long-term photostability. The Au24Pr1 clusters possess high fluorescence centered at ∼1100 nm and the SBR on pathological section diagnosis was 4 times higher than that of NIR-I imaging. This enables high spatial resolution 3D visualization of biopsy specimens, which can surmount tissue heterogeneity for clinical diagnosis of BC.

Novel aptamer fluorescence assays for malachite green and leucomalachite green detection

Simple fluorescence aptasensors were established for malachite green (MG) and leucomalachite green (LMG) detection using G-quadruplex dyes thioflavin T (ThT) and thiazole orange (TO), respectively. ThT and TO, initially non-fluorescent in aqueous solution, exhibited fluorescence upon binding to target-specific aptamers, resulting in the stabilization of G-quadruplex structures. The specific binding between G-quadruplex and MG could induce conformational changes, which caused a pronounced quenching of fluorescence emitted by the intercalator, providing a possibility for detection. The developed assays demonstrated a good linear relationship in the range of 0–1000 μg L-1 for MG and 0–250 μg L-1 for LMG, with low limits of detection of 5.4 × 10-3 μg L-1 and 0.1 μg L-1 respectively. More importantly, satisfactory detection results in water and fish samples were obtained. Noteworthy was that the uncomplicated fluorescent aptasensors operated effectively without the need for any modifications. The experimental process was facile and realized in homogeneous solution, which exhibited quick responsiveness after simple mixing.