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Abstract: In order to determine the contribution of intranasal (i.n.) administration to the uptake of large molecular weight (MW) substances into central nervous system (CNS), concentration in brain of the centrally acting polypeptide cobrotoxin (NT-I) versus time profiles were studied using dual-probe microdialysis in awake free-moving rats. NT-I, radiolabeled with sodium 125I-Iodide (125I-NT-I), was administered at the dose of 105μg/kg intravenously and intranasally in the same set of rat (n =15). The 125I-NT-Inasal preparations were formulated with borneol/menthol eutectic mixture (+BMEM) as an absorption enhancer and without (−BMEM). After application, the dialysates sampled simultaneously from olfactory bulb and cerebellar nuclei were measured in a gamma-counter for radioactivity. The real concentrations of NT-I were recalculated by in vivo recoveries of microdialysis probes. The results showed that the area under the curve (AUC) value in cerebellar nuclei (2283.51±34.54minng/ml) following i.n. administration (+BMEM) was significantly larger than those (AUColfactory =1141.92±26.42minng/ml; AUCcerebellar =1364.62±19.35minng/ml) after intravenous (i.v.) bolus, respectively. A prolonged time values to peak concentrations after i.n. application (+BMEM) were observed compared with those following i.v. administration. Also, following i.n. application (+BMEM) the measured time value to peak concentration in cerebellar nuclei (85min) was statistically longer than that in olfactory bulb (75min), which could be plausibly an indication for NT-I delivery into brain via nose–brain pathway in the presence of absorption enhancer. i.n. administration (−BMEM) had little or no ability of NT-I delivering into brain. In conclusion, i.n. administration (+BMEM) significantly enhanced brain transport of NT-I with uneven distribution in discrete regions of brain compared with i.v. administration. Additionally, multi-probe microdialysis technique should be considerably valuable in brain delivery studies. [Copyright &y& Elsevier]

Objectives: To develop a two-dimensional liquid chromatography method to determine the content of vitamin D 3 in cod liver oil preparations., Methods: The samples were prepared by saponification and extraction, and the content of vitamin D 3 was determined by two-dimensional liquid chromatography with dual-pump-single-valve switching dual detectors. The chromatographic column, capture device, and detection wavelength were optimized; the linearity, system suitability, recovery rate, repeatability and sample stability of the method were investigated, and further validated in actual sample determination., Results: A column switching two-dimensional chromatography method was developed. In the first dimensional chromatography, an Agilent PoroShell SB-C8 (50 mm×4.6 mm, 2.7 μm) column was used, and acetonitrile-water was used as mobile phase and gradiently eluted at a flow rate of 1.0 mL/min, the detection wavelength was 264 nm. An Agilent Zorbax SB-C18 (150 mm×3.0 mm,1.8 μm) column was used in the second dimensional chromatography, and acetonitrile was used as mobile phase at a flow rate of 0.42 mL/min, the detection wavelength was 264 nm. In determining content of Vitamin D 3 , there was a good linear relationship in the concentration range and the system suitability, recovery rate, repeatability and sample stability all met the verification requirements., Conclusions: The developed two-dimensional liquid chromatography method in the study is accurate, reproducible and simple, it can simultaneously separate pre-vitamin D 3 , trans-vitamin D 3 , vitamin D 3 , and tachysterol3, the baseline separation was achieved, indicating that it is worth promoting for application.

Objective: To establish a method for determination of 7-ethyl-10-hydroxycamptothecin (SN-38) in microdialysates from rat brain., Methods: The concentrations of SN-38 were measured by LC-MS/MS method with Agilent Eclipse Plus C18 (2.1 mm ×100 mm, 1.8 μm) reversed phase column using acetonitrile-0.1% methanoic acid as mobile phase with gradient elution at a flow rate of 0.3 ml/min and temperature at 35 degree. Multiple reaction monitoring using the precursor to product ion combinations of m/z 393.1→349.1 was performed to detect SN-38 in microdialysates from rat brain., Results: Blank microdialysate had non-interference. The method was linear over the concentration range of 0.1015-1015 ng/ml (r=0.9995); and the lower limit of quantification (LOQ) was 0.1015 ng/ml. The recovery of assay for SN-38 ranged from 97.54%-100.60%. The intra- and inter-day precision and stability were both well. The concentrations of SN-38 in brain microdialysates presented pharmacokinetics process and achieved the peak after 220 min., Conclusion: The fully validated LC-MS/MS analytical method has high specificity and sensibility, which can be used effectively to analyze SN-38 in microdialysates from rat brain.

In vivo sampling of interstitial fluid using microdialysis (MD) fibers has become a standard and accepted procedure. The resulting small volume samples, often with low concentrations of the analyte of interest, present a particular challenge to analytical methods. Rapid developments of analytical techniques with high sensitivity accelerate their combination with MD. On-line MD-based analytical systems are receiving increasing attention because they can provide near real-time data prior to the off-line system. The purpose of this review is to provide information for on-line MD-analytical systems. Special emphasis has been given to the main progression on methodologies of each method during recent years. The advantages, limitations, and adaptivity are also discussed. These methods include on-line MD-liquid chromatography, on-line MD-capillary electrophoresis, on-line MD-mass spectrometry, and on-line MD-biosensor.