The effective monitoring, identification, and quantification of pathogenic bacteria is essential for addressing serious public health issues. In this study, we present a universal and facile one-step strategy for sensitive and selective detection of pathogenic bacteria using a dual-molecular affinity-based Förster (fluorescence) resonance energy transfer (FRET) platform based on the recognition of bacterial cell walls by antibiotic and aptamer molecules, respectively. As a proof of concept, Vancomycin (Van) and a nucleic acid aptamer were employed in a model dual-recognition scheme for detecting Staphylococcus aureus (Staph. aureus). Within 30 min, by using Van-functionalized gold nanoclusters and aptamer-modified gold nanoparticles as the energy donor and acceptor, respectively, the FRET signal shows a linear variation with the concentration of Staph. aureus in the range from 20 to 108 cfu/mL with a detection limit of 10 cfu/mL. Other nontarget bacteria showed negative results, demonstrating the good specificity of the approach. When employed to assay Staph. aureus in real samples, the dual-recognition FRET strategy showed recoveries from 99.00% to the 109.75% with relative standard derivations (RSDs) less than 4%. This establishes a universal detection platform for sensitive, specific, and simple pathogenic bacteria detection, which could have great impact in the fields of food/public safety monitoring and infectious disease diagnosis.

Food poisoning and infectious diseases caused by pathogenic bacteria such as Staphylococcus aureus (SA) are serious public health concerns. A method of specific, sensitive, and rapid detection of such bacteria is essential and important. This study presents a strategy that combines aptamer and antibiotic-based dual recognition units with magnetic enrichment and fluorescent detection to achieve specific and sensitive quantification of SA in authentic specimens and in the presence of much higher concentrations of other bacteria. Aptamer-coated magnetic beads (Apt-MB) were employed for specific capture of SA. Vancomycin-stabilized fluorescent gold nanoclusters (AuNCs@Van) were prepared by a simple one-step process and used for sensitive quantification of SA in the range of 32–108 cfu/mL with the detection limit of 16 cfu/mL via a fluorescence intensity measurement. And using this strategy, about 70 cfu/mL of SA in complex samples (containing 3 × 108 cfu/mL of other different contaminated bacteria) could be successfully detected. In comparison to prior studies, the developed strategy here not only simplifies the preparation procedure of the fluorescent probes (AuNCs@Van) to a great extent but also could sensitively quantify SA in the presence of much higher concentrations of other bacteria directly with good accuracy. Moreover, the aptamer and antibiotic used in this strategy are much less expensive and widely available compared to common-used antibodies, making it cost-effective. This general aptamer- and antibiotic-based dual recognition strategy, combined with magnetic enrichment and fluorescent detection of trace bacteria, shows great potential application in monitoring bacterial food contamination and infectious diseases.

•A new strategy of multicolor QD-based fluorescence immunoassay arrays was developed.•The strategy could achieve visual and high-throughput analysis of multiple antibiotics.•The strategy could provide rapid and specific assay for residues of three antibiotics.•The strategy provided low detection limit of 5 fg/mL for analysis of target antibiotic.Antibiotic residues, which are among the most common contaminants in animal-based food products such as milk, have become a significant public health concern. Here, we combine a multicolor quantum dot (QD)-based immunofluorescence assay and an array analysis method to achieve simultaneous, sensitive and visual detection of streptomycin (SM), tetracycline (TC), and penicillin G (PC-G) in milk. Antibodies (Abs) for SM, TC and PC-G were conjugated to QDs with different emission wavelengths (QD520 nm, QD565 nm and QD610 nm) to serve as detection probes (QD-Ab). Then a direct competitive fluorescent immunoassay was performed in antigen-coated microtiter plate wells for simultaneous qualitative and quantitative detection of SM, TC, and PC-G residues, based on fluorescence of the QD-Ab probes. The linear ranges for SM, TC and PC-G were 0.01–25 ng/mL, 0.01–25 ng/mL and 0.01–10 ng/mL, respectively, with detection limit of 5 pg/mL for each of them. Based on fluorescence of the QD-Ab probes, residues of the three antibiotics were determined visually and simultaneously. Compared with a commercial enzyme-linked immunosorbent assay kit, our method could achieve simultaneous analysis of multiple target antibiotics in multiple samples in a single run (high-throughput analysis) and improved accuracy and sensitivity for analysis of residues of the three antibiotics in authentic milk samples. This new analytical tool can play an important role in ameliorating the negative impact of the residual antibiotics on human health and the ecosystem.

A novel nanohybrid of hyaluronic acid (HA)-decorated graphene oxide (GO) was fabricated as a targeted and pH-responsive drug delivery system for controlling the release of anticancer drug doxorubicin (DOX) for tumor therapy. For the preparation, DOX was first loaded onto GO nanocarriers via π–π stacking and hydrogen-bonding interactions, and then it was decorated with HA to produce HA–GO–DOX nanohybrids via H-bonding interactions. In this strategy, HA served as both a targeting moiety and a hydrophilic group, making the as-prepared nanohybrids targeting, stable, and disperse. A high loading efficiency (42.9%) of DOX on the nanohybrids was also obtained. Cumulative DOX release from HA–GO–DOX was faster in pH 5.3 phosphate-buffered saline solution than that in pH 7.4, providing the basis for pH-response DOX release in the slightly acidic environment of tumor cells, while the much-slower DOX release from HA–GO–DOX than DOX showed the sustained drug-release capability of the nanohybrids. Fluorescent images of cellular uptake and cell viability analysis studies illustrated that these HA–GO–DOX nanohybrids significantly enhanced DOX accumulation in HA-targeted HepG2 cancer cells compared to HA-nontargeted RBMEC cells and subsequently induced selective cytotoxicity to HepG2 cells. In vivo antitumor efficiency of HA–GO–DOX nanohybrids showed obviously enhanced tumor inhibition rate for H22 hepatic cancer cell-bearing mice compared with free DOX and the GO–DOX formulation. These studies suggest that the HA–GO–DOX nanohybrids have potential clinical applications for anticancer drug delivery.Keywords: cancer; drug delivery; graphene oxide; hyaluronic acid; nanocarrier; targeted

In this study, magnetic-encoded fluorescent (CdTe/Fe3O4)@SiO2 multifunctional nanospheres were constructed by adjusting the initial concentration of Fe3O4 in a fabrication process based on reverse microemulsion. The resultant multifunctional nanospheres were characterized by transmission electron microscopy, X-ray diffraction measurements, fluorescence spectrophotometry, and vibrating sample magnetometry. They showed good fluorescence properties, gradient magnetic susceptibility (weak, moderate, and strong), and easy biofunctionalization for biomolecules, such as immunoglobulin G (IgG), protein, and antibody. Then the capture efficiency of the (CdTe/Fe3O4)@SiO2 nanospheres were investigated by using the fluorophore-labeled IgG-conjugated nanospheres as a model. Further studies demonstrated the ability of these (CdTe/Fe3O4)@SiO2 multifunctional nanospheres to accomplish sequentially magnetic separation, capture, and fluorescent detection for each corresponding antigen of CA125, AFP, and CEA with a detection limit of 20 KU/L, 10 ng/mL, and 5 ng/mL, respectively, from a mixed sample under a certain external magnetic field within a few minutes. The strategy of combining magnetic-encoding-based separation and fluorescence-based detection proposed in this study shows great potential to achieve easy, rapid, economical, and near-simultaneous multicomponent separation and analysis for a variety of targets such as drugs, biomarkers, pathogens, and so on.

•A novel FITC–HA–AuNPs FRET nanoprobe was facilely synthesized in one-step.•Fluorescence recovery of nanoprobes is based on the degradation of HAase to HA.•A low detection limit (0.63 U mL−1) for HAase was obtained by the nanoprobes.•The nanoprobes could determine HAase in human urine specimen with good accuracy.•The nanoprobe-based strategy has potential for diagnosis of HAase-related diseases.Gold nanoparticles (AuNPs) have been widely used to develop fluorescence resonance energy transfer (FRET) sensors to detect biological substances, environmental pollutants, and disease markers due to their superior quenching capacity to fluorescence signals. In this study, we report the one-step facile synthesis of fluorescein isothiocyanate-labeled hyaluronic acid (FITC–HA) functionalized fluorescent AuNPs based FRET nanoprobes (FITC–HA–AuNPs) via chemical reduction of HAuCl4 by using FITC–HA as both a reducing and stabilizing agent. Then the FITC–HA–AuNPs FRET nanoprobes were used to detect hyaluronidase (HAase), a new type of disease marker, based on the specific enzymatic degradation of HAase to HA. Compared with similar work, the FITC–HA–AuNPs nanoprobes were much easier to prepare and the detection sensitivity was also high for HAase to reach a detection limit of 0.63 U mL−1. More importantly, they also allowed for rapid HAase detection (within 3 h) even in complex biological specimens (urine specimens from patients with bladder cancer) with satisfactory accuracy (recovery efficiency in the range of 92.8–106.9% with RSD≤4.85%). Our studies suggested that such a novel design of FITC–HA–AuNPs FRET nanoprobes developed for sensitive, rapid and accurate detection of HAase had exciting potentials for clinical diagnosis of HAase-related diseases, such as bladder cancer.

•A graphene oxide based FRET sensor for MMP-2 was developed by covalent conjugation.•The sensor has better stability to resist the interference from external environment.•A low detection limit for MMP-2 (2.5 ng/mL) was obtained by the sensor.•The sensor was used to determine MMP-2 in real serum sample rapidly (within 3 h) with good accuracy (RSD≤7.03%).Graphene oxide (GO) has been widely used to develop fluorescence resonance energy transfer (FRET) biosensors for tumor markers (e.g., matrix metalloproteinases, MMPs) due to its superior fluorescence quenching capacity and unique adsorption characteristics for biomolecules. In this study, fluorescein isothiocyanate-labeled peptide (Pep-FITC) was assembled onto the GO surface through covalent binding to construct a GO-Pep-FITC FRET sensor for sensitive, rapid, and accurate detection of MMP-2 in complex serum samples. Compared to similar GO-based FRET sensors fabricated through physical adsorption, the as prepared ones via covalent binding are significantly more stable under physiological conditions, enabling their detection of MMP-2 with high sensitivity (detection limit: 2.5 ng/mL). More importantly, it allows for rapid MMP-2 detection (within 3 h) even in complex biological samples with satisfactory accuracy and the relative standard deviation ≤7.03%. Our studies further suggest that such a platform developed here for sensitive, rapid, and accurate detection of biomarkers holds great promise for clinical diagnosis of protease-related diseases.

Here, we report the one-step synthesis of N-acetylglucosamine-functionalized gold nanoparticle (NAG–AuNP), which then served as a facile, economic, highly sensitive and selective sensor for the detection of lectin from wheat germ, based on colorimetric and resonance light scattering signals.

•LA significantly inhibited LPS/d-GalN-induced serum transaminase activities.•LA prevented LPS/d-GalN-induced histopathological changes.•LA reduced ROS and TBARS levels, and increased CAT and GPx activities.•LA reduced iNOS, COX-2, TNF-α, NF-κB, IL-1β and IL-6 expressions.•LA reduced caspase 3, 8, 9 expressions and Bax/Bcl-2 ratio.This study investigated the protective effect of α-lipoic acid (LA) on lipopolysaccharide (LPS)/d-galactosamine (d-GalN)-induced fulminant hepatic failure in mice. First, we found that LA markedly reduced LPS/d-GalN-induced increases in serum ALT and AST activities, which were supplemented with histopathological examination, suggested that LA has a protective effect on this model of hepatic damage. Livers challenged with LPS/d-GalN exhibited extensive areas of vacuolization with the disappearance of nuclei and the loss of hepatic architecture. On the contrary, these pathological alterations were ameliorated by LA treatment. Next, we found that ROS and TBARS levels were increased in LPS/d-GalN treated liver homogenates, which were attenuated by LA administration. Consistently, decreases in hepatic CAT and GPx activities were observed in LPS/d-GalN group and were significantly restored by LA administration. Moreover, pretreatment with LA markedly reduced LPS/d-GalN-induced iNOS, COX-2, TNF-α, NF-κB, IL-1β and IL-6 expressions. Furthermore, our data showed that TUNEL-positive cells increased in LPS/d-GalN-treated mice liver which was counteracted by LA administration. LPS/d-GalN induced apoptosis of hepatocytes, as estimated by caspase 3, caspase 8 and caspase 9 activations. Also, the increasing of Bax and the decreasing of Bcl-2 expressions also supported LPS/d-GalN induced apoptosis. Interestingly, LA marked relieved these apoptotic features. Taking together, our results indicated that LA plays an important role on LPS/d-GalN-induced fulminant hepatic failure through its antioxidant, anti-inflammatory and anti-apoptotic activities.

ObjectiveTo compare the nature of the metabolites formed from the phase I metabolism (hydroxylation and oxidation) and phase II metabolism (glutathionyl conjugation) of PCBs that have different chlorine substitution patterns. To discuss the structure-activity relationships and metabolic mechanisms of PCBs.Methods4-Cl-biphenyl (PCB3), 4,4'-Cl-biphenyl (PCB15), 3,4,3',4'-Cl-biphenyl (PCB77) were used for in vitro metabolic study. LC/MS and UV-Vis studies were performed for metabolites identification.ResultsThe cytochrome P-450 catalyzed hydroxylation rate decreased as the number of chlorine substitutions increased. In this reaction, PCB3 was fully metabolized, approximately half of the PCB15 was metabolized and PCB77 was not metabolized at all. The oxidation rate of PCB15-HQ was higher than that of PCB3-HQ under various oxidation conditions. The LC/MS and UV-Vis data suggest that in the conjugation reaction of PCB15-Q and GSH, the Michael addition reaction occurs preferentially over the displacement reaction.ConclusionThe metabolic profiles of polychlorinated biphenyls (PCBs) are dramatically affected by chlorine substitution patterns. It is suggested that the metabolic profiles of PCBs are related to their chlorine substitution patterns, which may have implications for the toxicity of PCB exposure.

•A simple strategy fluorescent sensor for sensitive and specific detection of Fe3+ was developed.•This strategy for Fe3+ showed comparable sensitivity and wide assay range.•This strategy could be applied for the assay of Fe3+ in real sample satisfactorily.•The cheap and available antibiotics were employed to synthesis of fluorescent sensor effectively.In this paper, the cheap, easily obtained small antibiotic molecule of vancomycin was employed as reducer/stabilizer for facile one-pot synthesis of water exhibited a bluish fluorescence emission at 410 nm within a short synthesis time about 50 min. Based on the strong fluorescence quenching due to electron transfer mechanism by the introduction of ferric ions(Fe3+), the Van-AuNCs were interestingly designed for sensitive and selective detecting Fe3+ with a limit of 1.4 μmol L−1 in the linear range of 2–100 μmol L−1 within 20 min. The Van-AuNCs based method was successfully applied to determine Fe3+ in tap water, lake water, river water and sea water samples with the quantitative spike recoveries from 97.50–111.14% with low relative standard deviations ranging from 0.49–1.87%, indicating the potential application of this Van-AuNCs based fluorescent sensor for environmental sample analysis.