[Fluoroimmunoassay and Magnetic Lateral Flow Immunoassay for the Detection of Ractopamine].

A fluoroimmunoassay based on quantum dots (QDs) and a lateral flow immunoassay system based on the magnetic beads (MB) were constructed to detect ractopamine (RAG) in urine samples. The monoclonal antibody (Ab1) against RAC was conjugated with QDs or MB as detector reagent, respectively. They apply a competitive format using an immobilized RAC conjugate and free RAC present in samples. That is to say, the concentration of RAC in the sample was negative related to the fluorescense intensity of QDs or the color density of MB. Results showed that the limit of detection (LOD) of fluorescence immunoassay method is 1 ng · mL⁻¹ and analysis time is 4 h, while the visual LOD was 10 ng · mL⁻¹ and analysis time was 15 min in magnetic lateral flow immunoassay system (MFLIS). Taken into consideration of the advantages and disadvantages of the two methods, it was suitable for the trace detection of RAC using fluoroimmunoassay while it was appropriate for point-of-care tesing of RAC by MFLIS.

[Fluorescent and Magnetic Relaxation Switch Immunosensor for the Detecting Foodborne Pathogen Salmonella enterica in Water Samples].

Fluoroimmunoassay based on quantum dots (QDs) and magnetic relaxation switch (MRS) immunoassay based on superparamagnetic nanoparticles (SMN) were constructed to detect Salmonella enterica (S. enterica) in water samples. In fluoroimmunoassay, magnetic beads was conjugated with S. enterica capture antibody (MB-Ab2) to enrich S. enterica from sample solution, then the QDs was conjugated with the S. enterica detection antibody (QDs-Ab1) to detect S. enterica based on sandwich immunoassay format. And the fluorescence intensity is positive related to the bacteria concentration of the sample. Results showed that the limit of detection (LOD) of this method was 102 cfu · mL⁻¹ and analysis time was 2 h. In MRS assay, magnetic nanoparticle-antibody conjugate (MN-Ab1) can switch their dispersed and aggregated state in the presence of the target. This state of change can modulate the spin-spin relaxation time (T2) of the neighboring water molecule. The change in T2(ΔT2) positively correlates with the amount of the target in the sample. Thus, AT can be used as a detection signal in MRS immunosensors. Results showed that LOD of MRS sensor for S. enterica was 10³ cfu · mL⁻¹ and analysis time was 0.5 h. Two methods were compared in terms of advantages and disadvantages in detecting S. enterica.

[The potential mechanism on signal transduction pathway in regulation of mRNA expression of high mobility group box-1 protein in septic rats].

OBJECTIVE: To investigate the potential role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in regulation of gene expression of high mobility group box-1 protein (HMGB1) in various tissues in rats with sepsis. METHODS: A sepsis model reproduced by cecal ligation and puncture (CLP), and 128 male Wistar rats were randomly divided into normal control group (n = 10), sham operation group (n = 10), CLP group (n = 60), AG490 treatment group (n = 24), and rapamycin (RPM) treatment group (n = 24). At serial time points animals in each group were sacrificed after CLP, then tissue samples were harvested to determine HMGB1 mRNA expression and STAT1/3 DNA binding activity. RESULTS: STAT1 activities increased rapidly in the liver, lungs and small intestine after CLP, peaking at 6 - 12 h, while it increased slowly, and still kept at mild level from 2 to 48 h in the kidneys. Compared with STAT1, lower STAT3 activities were detected only in the liver and lungs, with negative detection in the small intestine and kidneys. HMGB1 mRNA levels significantly increased in liver, lungs and small intestine at various time points after CLP respectively (P < 0.05 or P < 0.01), while they didn't change in the kidneys. Treatment with AG490 could markedly inhibit HMGB1 mRNA expression in the liver and small intestine at 24 and 48 h (P < 0.05 or P < 0.01), and in lungs at 2 h following CLP (P < 0.01). Similarly, treatment with RPM significantly decreased HMGB1 mRNA expression in the lungs at 2, 6, 24 and 48 h, in the liver at 6 and 24 h, and in the small intestine at 24 and 48 h (P < 0.05 or P < 0.01). In addition, STAT1 and STAT3 activities in the liver and lungs were significantly correlated with corresponding tissue HMGB1 mRNA expression. CONCLUSIONS: Peritoneal infection could extensively activate STAT1 and limitedly activate STAT3 in vital organs. Activation of JAK/STAT pathway might be involved in up-regulating the gene expression of HMGB1 and systemic inflammation secondary to severe septic challenge.

[Role of Janus kinase/signal transducer and activator of transcription pathway in mediating mRNA expression of high mobility group box1 protein in the liver in septic rats].

OBJECTIVE: To investigate the role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in mediating mRNA expression of high mobility group box 1 protein (HMGB1) in the liver in septic rats. METHODS: Using a sepsis model of cecal ligation and puncture (CLP), 98 male Wistar rats were randomly divided into normal control group (n=10), CLP group (n=40), AG490 treatment group (n=24), and Rapamycin (RPM) treatment group (n=24). At serial time points animals in each group were sacrificed, and blood as well as hepatic tissue samples were harvested to determine HMGB1 mRNA expression and serum aspartate aminotransferase (AST) as well as alanine aminotransferase (ALT) contents. RESULTS: Compared with normal controls, HMGB1 mRNA levels were significantly increased in the liver during 6-48 hours after CLP (P<0.01), and serum AST and ALT contents were significantly elevated at different time points respectively (P<0.05 or P<0.01). Treatment with AG490 and RPM could markedly inhibit HMGB1 mRNA expression in the liver at 24 hours, 48 hours, 6 hours and 24 hours after CLP, respectively. In addition, compared to CLP group, serum AST and ALT contents in both treatment groups could be markedly reduced at various intervals after CLP (P<0.05 or P<0.01). CONCLUSION: These data suggest that the activation of JAK/STAT pathway might be involved in mediating up-regulation of HMGB1 mRNA expression in the liver in CLP-induced sepsis. Treatment with inhibitors of JAK/STAT pathway could markedly down-regulate HMGB1 mRNA expression and attenuate acute liver injury associated with sepsis.