Nanoscale affinity chip interface for coupling inhibition SPR immunosensor screening with Nano-LC TOF MS.

The on-line nanoscale coupling of a surface plasmon resonance (SPR)-based inhibition biosensor immunoassay (iBIA) for the screening of low molecular weight molecules with nano-liquid-chromatography electrospray ionization time-of-flight mass spectrometry (nano-LC ESI TOF MS) for identification is described. The interface is based on a reusable recovery chip (RC) that contains a nanoscale biosorbent composed of a hydrogel layer modified with antibodies raised against the analyte featuring the unique possibility of performance characterization using the SPR biosensor. Various hydrogel chemistries were evaluated, and the standard Biacore CM5 chip showed the highest capture capacity in combination with affinity-purified polyclonal antibodies. The procedure has four stages: the samples are prepared (1) and screened using a screening chip (SC) in the iBIA (2). Suspected noncompliant samples as being noncompliant are reinjected over the RC, and the analyte is captured at subnanogram level (3). The captured analyte is released, and the eluate is analyzed with nano-LC ESI TOF MS via a loop-type interface (4). The coupling of the technologies proved effective for screening enrofloxacin, a model compound, in incurred chicken muscle samples followed by identity confirmation in suspected noncompliant samples. Ciprofloxacin, a known metabolite of enrofloxacin, was identified as well in incurred chicken samples. This demonstrates the potential of the technologies coupled by means of a RC for the rapid screening and identification of known as well as unknown compounds. Finally, we demonstrate the feasibility of combining the two biosensor chips (SC and RC) with a robust chip-based nano-LC chip TOF MS system, thus providing a robust alternative triple-chip system.

Spreeta-based biosensor assays for endocrine disruptors.

The construction and performance of an automated low-cost Spreeta-based prototype biosensor system for the detection of endocrine disrupting chemicals (EDCs) is described. The system consists primarily of a Spreeta miniature liquid sensor incorporated into an aluminum flow cell holder, dedicated to support a Biacore chip frame, in combination with a simple pressurized air-driven fluid system. During the optimization, a monoclonal antibody (MAb)-based immunoassay for the estrogenic compound bisphenol A (BPA) was used as a model. After the optimization two thyroxine transport protein inhibition assays for thyroid endocrine disruptors were implemented. The average noise of the system for 1 min of baseline was 1.1 microRIU (refractive index units) and it could be operated in the range of 18-22 degrees C with a minimum baseline drift (5-10 microRIU/100 min). Optimum signal to noise ratio (S/N R) was obtained using a flow cell height of 100 microm and a flow rate of 180 microl/min. The sensitivity of the Spreeta-based biosensor inhibition assays implemented (50% inhibition concentration (IC50) of 30.2 nM for BPA using MAb12 and 12.3 and 11.6 nM for thyroxine (T4) using thyroxine-binding globulin (TBG) and recombinant transthyretin (rTTR), respectively) was comparable to the sensitivity previously obtained using a Biacore 3000 (IC50 of 39.9 nM for BPA and 8.6 and 13.7 nM, respectively, for T4). The results indicate that the alternative prototype system can be used in combination with ready-to-use biosensor chip surfaces and it is potentially a useful tool for the bioeffect-related screening of EDCs.

Hippocampus and locus coeruleus activity on rats chronically treated with diazepam.

The neural mechanisms underlying benzodiazepine (BZD) dependence remain equivocal. The present studies tested the hypothesis that similar neural circuitry might be involved in the effects of chronic 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepine-2(1H)-one, diazepam (DZ, Roche), administration and withdrawal. The results of our study showed an increased hippocampal synaptic plasticity in slices from rats chronically treated with DZ (5 mg/kg/18 days), assessed as a decrease of the threshold in the stimulation rate for long-term potentiation (LTP) elicitation. Rats with the same schedule of DZ administration but without signs of withdrawal behaved similarly to vehicle-treated ones (VEH), in the threshold to induce LTP. Furthermore, the activity of locus coeruleus (LC) norepinephrine (NE) neurons in rats tested 24 h after the last DZ injection showed a significant increase. On the other hand, rats that after chronic DZ administration did not develop signs of withdrawal and exhibited a similar pattern of discharge on LC-NE nucleus compared with their controls. We conclude that chronic DZ administration enhances both hippocampal synaptic plasticity and activity of LC-NE neurons. This neural system could be the biological substrate underlying the behavioral alterations accompanying chronic DZ administration and withdrawal.