微透析技术探针回收率的影响因素研究进展

微透析技术是近年来发展起来的动态生物取样技术,具有"活体、微创、实时、高效"等特点,其与现代分析技术联用,实现了连续取样和动态测定,可进行微量的定性、定量分析。微透析探针回收率的准确校正,是测定生物体中待测组分确切浓度的关键步骤,可提高大分子、难溶性物质的回收率,使微透析的应用更为广泛。本文对微透析探针回收率的影响因素、校正方法以及近年来提高回收率所取得的进展做一综述。     

钩藤碱微透析探针回收率测定及影响因素研究

目的:考察体内外微透析探针回收率的稳定性和重现性,为进一步的体内微透析试验提供依据。方法:采用增量法和减量法考察浓度、流速对探针回收率的影响。结果:微透析探针回收率受流速影响较大,基本不受浓度影响,且体内回收率稳定性良好。结论:微透析技术可用于钩藤碱的体内药代动力学研究,反透析法可作为体内研究钩藤碱探针回收率的测定方法。     

微透析技术在药物-蛋白结合研究中的应用

目的 介绍微透析技术在药物-蛋白结合研究中的应用。方法 通过查阅近年来国内外相关文献,概述微透析技术的基本原理、特点、探针及影响探针相对回收率的主要因素,并重点介绍其在药物-蛋白结合研究中的应用。结果与结论 与平衡透析法、超滤法相比,微透析技术是一项新兴的在体或离体取样技术,在药物-蛋白结合研究中具有显著的优越性和广阔的应用前景。     

微透析技术在药物-蛋白结合研究中的应用

目的介绍微透析技术在药物-蛋白结合研究中的应用。方法通过查阅近年来国内外相关文献,概述微透析技术的基本原理、特点、探针及影响探针相对回收率的主要因素,并重点介绍其在药物-蛋白结合研究中的应用。结果与结论与平衡透析法、超滤法相比,微透析技术是一项新兴的在体或离体取样技术,在药物-蛋白结合研究中具有显著的优越性和广阔的应用前景。     

灌流液改性剂对环维黄杨星D微透析探针回收率的影响研究

目的考察灌流改性剂对环维黄杨星D微透析探针回收率的影响,验证使用改性灌流液条件下微透析探针体外相对回收率与相对损失率的一致性,为体内微透析研究提供实验依据。方法采用高效液相色谱法测定灌流液中环维黄杨星D含量,计算不同改性灌流液条件下微透析探针的体外相对回收率,优选合适的改性剂种类与用量,再分别采用增量法与减量法计算不同药物浓度水平下探针体外相对回收率与相对损失率,比较两者结果的一致性。结果常规灌流条件下,乙醇作为灌流液改性剂对环维黄杨星D相对回收率提高较多,优选灌流液配比为30%乙醇-林格氏液。在2.53~10.12μg·mL~(-1)内环维黄杨星D体外相对回收率和相对损失率具有高度的一致性。结论选择合适的灌流液改性剂可显著提高微透析探针相对回收率水平,对于同一根微透析探针环维黄杨星D体外相对回收率与外周液药物浓度无关,探针回收率可通过药物透过半透膜时的流失量来间接计算,结果较好地证明反透析法适合于环维黄杨星D微透析采样。     

头孢拉定微透析体外回收率及影响因素的研究

目的 测定头孢拉定微透析体外回收率及影响因素。方法 采用微透析浓度差法（减量法、增量法）和液质联用技术（LC-MS/MS）测定头孢拉定的体外回收率,并考察流速、浓度对回收率的影响,以探讨微透析技术用于头孢拉定体内药动学研究的可行性。结果 所建立的方法在要求范围内线性关系良好,方法灵敏可靠。增、减量法测得的回收率无显著性差异。相同条件下,探针体外回收率随流速增大而减小,不受探针周围药物浓度的影响。结论 微透析技术可用于头孢拉定药动学研究,减量法可用于头孢拉定微透析体内回收率和药动学参数的测定。     

内标法测定烟碱微透析回收率的可行性研究

研究利用内标法测定烟碱微透析回收率的可行性。通过测定磷酸可待因与烟碱在不同情况下的体外回收率(或释放率),考察它们之间的关系。考察探针周围烟碱浓度对两种物质的体外回收率(或释放率)及它们之间比值的影响。分别用内标法及反透析法测定烟碱大鼠体外血浆蛋白结合率。结果显示,磷酸可待因的释放率与烟碱的回收率之间的比例较稳定,磷酸可待因的释放率不因探针周围烟碱的浓度而改变。内标法及反透析法测得的血浆蛋白结合率相差不大。内标法可作为体内微透析研究中烟碱回收率的测定方法,磷酸可待因可作为该方法中的内标物。     

葛根素微透析线性探针相对回收率影响因素的研究

目的考察影响葛根素微透析相对回收率相关影响因素,探索提高微透探针相对回收率的方法。方法采用高效液相色谱法考察不同pH值（5.1、6.0、7.4、8.1）,不同浓度丙二醇（1%、5%、10%、20%、30%）,不同浓度羟丙基-β-环糊精（1%、5%、10%、20%）的灌注液对葛根素微透析线性探针相对回收率的影响。结果微透析灌注液pH值5.1,羟丙基-β-环糊精含量5%时,葛根素相对回收率提高至（90.07±1.24）%。灌流液中丙二醇会对微透析线性探针的传递率产生负影响,降低相对回收率,在以葛根素为模型药物的微透析实验灌流液中不建议添加。结论本实验方法灌流液中添加增溶剂羟丙基-β-环糊精,可使葛根素经过半透膜时流失量减少,显著提高葛根素微透析线性探针相对回收率。     

芒柄花素、芍药苷血液和脑在体微透析方法的建立

目的:建立芒柄花素、芍药苷血液和脑局部在体微透析方法。方法:采用增量法考察流速对芒柄花素和芍药苷回收率的影响,结合实际操作,确定流速和取样间隔;利用浓度差法(增量法和减量法)研究流速、浓度、温度对微透析探针体外回收率和损失率的影响,探讨反透析法用于探针体内回收率测定的可行性;将血液探针和脑探针分别植入大鼠颈静脉和脑纹状体,考察探针在10h内体内回收率的稳定性。结果:芒柄花素,芍药苷血液和脑探针体外回收率随着流速的增高而降低,综合考虑取样时间和取样体积,确定流速为1.5μL·min^-1,取样时间间隔为20min;在相同流速和温度下,探针增量法回收率RR与减量法损失率RL近似相等,且探针回收率与药物浓度无关,说明可用反透析法进行体内回收率的测定;在大鼠体内微透析回收率考察中,血液和脑探针10h回收率保持相对稳定,但不同探针相对回收率之间存在一定的差异性。结论:所建立的芒柄花素、芍药苷血液和脑微透析方法可用于大鼠体内和脑局部药动学研究,反透析法可作为同时研究芒柄花素,芍药苷探针体内回收率的测定方法。     

基于微透析技术的苦参碱凝胶经皮给药的药动学研究

目的 建立同步测定经皮给药制剂在皮肤、血液中药动学的方法,研究苦参碱凝胶在体内的药动学行为。方法 应用经体外和体内回收率校正建立的基于微透析探针的皮肤血液双位点同步微透析系统,通过在皮肤和颈静脉植入探针,在大鼠腹部脱毛部位给予苦参碱凝胶,连续收集探针中12 h的透析液,并采用LC-MS微量检测技术测定探针透析液中的药物浓度。结果 本研究成功构建了双位点同步微透析药动学评价系统,大鼠皮肤给予苦参碱凝胶后,皮肤中的药物浓度、AUC值、半衰期均显著高于血液中药物浓度。结论 本研究建立的微透析结合LC-MS的取样及检测技术为经皮给药制剂的药动学研究提供了新的技术平台。     

Use of osmotic agents in microdialysis studies to improve the recovery of macromolecules

The availability of microdialysis probes with higher molecular weight cutoff membranes has made it possible to measure larger molecular weight compounds like bioactive peptides and proteins. However, the higher molecular weight membrane cutoff allows for increased fluid loss from the probe, influencing both the physiology of the tissue compartment and analyte recovery. This study examined the ability of osmotic agents like bovine serum albumin (BSA) to offset the water loss from the microdialysis probe. In the presence of BSA, water loss from the microdialysis probe was minimized. Furthermore, addition of BSA to the perfusate produced significant increases in analyte recovery. Application of this technique to the measurement of bioactive macromolecules was examined using in vitro microdialysis of tumor necrosis factor (TNF) and interleukin-1 beta (IL-1B). The results of the present study suggest osmotic agents like BSA can prevent fluid loss from the microdialysis probe and improve analyte recovery.     

Evaluation of in vivo and in vitro recovery rate of anatoxin-a through the microdialysis probe

In vivo microdialysis is a versatile sampling technique commonly employed to observe changes in neurotransmitters levels that occur in response to different treatments, being these treatments administered through a microdialysis probe implanted into a specific brain region in living animals. In previous works we have used this technique to study the effects of the drug anatoxin-a, a nicotinic acetylcholine receptor agonist, on dopamine release in striatum. The aim of the present study was to assess the recovery of anatoxin-a through the microdialysis probe. This information allows knowing the exact amount of the drug crossing the microdialysis membrane, acting on extracellular tissue. High Performance Liquid Chromatography (HPLC) with Fluorescence Detection (FLD) has been used for the analysis of anatoxin-a. We observed that the recovery of anatoxin-a was about 0.5%. Under our experimental conditions, the results suggest that anatoxin-a can be used as an important tool in the study of neuronal nicotinic receptors by in vivo microdialysis technique and also show a reliable estimation of the anatoxin-a recovery through the microdialysis probe under both in vivo and in vitro conditions.     

Microdialysis Sampling for the Investigation of Dermal Drug Transport

Microdialysis perfusion in vivo has the potential to be a powerful sampling technique in dermal and transdermal drug delivery studies. Characterization of a commercially available microdialysis probe in vitro considering relevant physiological parameters is a vital first step in the evaluation of microdialysis as a dermal sampling technique. In previous microdialysis studies, analyte concentration and neutrality have been implicated in altering microdialysis recovery. The recovery of a model compound 5-fluorouracil (5-FU) was investigated at several pH values and donor concentrations. The relative recovery of 5-FU by the microdialysis probe was affected by pH but not by donor concentration. To confirm further that the changing concentration and pH profile presented by the flux of 5-FU was not significantly altering microdialysis recovery, an experiment comparing direct and microdialysis sampling of a Franz diffusion cell receptor compartment was performed. Although the 5-FU concentration (0-686 ng/ml) and pH (7.40-7.24) changed substantially, the recovery of 5-FU was not adversely affected. To demonstrate the feasibility of dermal microdialysis, the flux of a commercial preparation of 5-fluorouracil was monitored utilizing a microdialysis probe implanted in excised rat skin in vitro. The results from the dermally implanted probe demonstrate the potential of the technique while establishing the limitations of the current microdialysis system.     

Assessment of in vitro and in vivo recovery of gallamine using microdialysis

The application of microdialysis technique for the investigation of pharmacokinetics and pharmacodynamics of drugs requires careful assessment of probe performance to ensure validity of the data obtained using this technique. The aim of this study was to establish and validate the microdialysis technique for investigation of the pharmacokinetics and pharmacodynamics of the neuromuscular blocker, gallamine. In vitro recovery of gallamine from the microdialysis probe when different perfusion flow rates were employed was evaluated leading to selection of a flow rate of 2 microl/min with 15-min sampling intervals for the subsequent studies. In vitro recovery of gallamine from the microdialysis probe was independent of concentration, stable over an 8-h period and reproducible. Comparable in vitro recoveries were obtained by different established approaches including recovery estimation by gain, loss and the zero-net flux (ZNF) method. Recovery by loss was used to study the in vivo recovery of gallamine from rat muscle tissue. The in vivo recovery was stable over a 5.5-h sampling period. In vitro performance of the probe subsequent to the in vivo study remained stable supporting reusage of the probe. These data highlight the importance of a systematic examination of microdialysis probe validation.     

Microdialysis for pharmacokinetic analysis of drug transport to the brain

The intracerebral microdialysis technique represents an important tool for monitoring free drug concentrations in brain extracellular fluid (brain(EcF)) as a function of time. With knowledge of associated free plasma concentrations, it provides information on blood-brain barrier (BBB) drug transport. However, as the implantation of the microdialysis probe evokes tissue reactions, it should be established if the BBB characteristics are maintained under particular microdialysis experimental conditions. Several studies have been performed to evaluate the use of intracerebral microdialysis as a technique to measure drug transport across the BBB and to measure regional pharmacokinetics of drugs in the brain. Under carefully controlled conditions, the intracerebral microdialysis data did reflect passive BBB transport under normal conditions, as well as changes induced by hyperosmolar opening or by the presence of a tumor in the brain. Studies on active BBB transport by the mdr1a-encoded P-glycoprotein (Pgp) were performed, comparing mdr1a(-/-) with wild-type mice. Microdialysis surgery and experimental procedures did not affect Pgp functionality, but the latter did influence in vivo concentration recovery, which was in line with theoretical predictions. It is concluded that intracerebral microdialysis provides meaningful data on drug transport to the brain, only if appropriate methods are applied to determine in vivo concentration recovery.     

Blood microdialysis in pharmacokinetic and drug metabolism studies

Microdialysis is a sampling technique allowing measurement of endogenous and exogenous substances in the extracellular fluid surrounding the probe. In vivo microdialysis sampling offers several advantages over conventional methods of studying the pharmacokinetics and metabolism of xenobiotics, both in experimental animals and humans. In the first part of this review article various practical aspects related to blood microdialysis will be discussed, such as: probe design, surgical implantation techniques, methods to determine the in vivo relative recovery of the analyte of interest by the probe, special analytical considerations related to small volume microdialysate samples, and pharmacokinetic calculations based on microdialysis data. In the second part of this review a few selected applications of in vivo microdialysis sampling to investigate pharmacokinetic processes are briefly discussed: determination of in vivo plasma protein binding in small laboratory animals, distribution of drugs across the blood-brain barrier, the use of microdialysis sampling to study biliary excretion and enterohepatic cycling, blood microdialysis sampling in man and in the mouse, and in vivo drug metabolism studies.     

Application of Microdialysis in Pharmacokinetic Studies

The objective of this review is to survey the recent literature regarding the various applications of microdialysis in pharmacokinetics. Microdialysis is a relatively new technique for sampling tissue extracellular fluid that is gaining popularity in pharmacokinetic and pharmacodynamic studies, both in experimental animals and humans. The first part of this review discusses various aspects of the technique with regard to its use in pharmacokinetic studies, such as: quantitation of the microdialysis probe relative recovery, interfacing the sampling technique with analytical instrumentation, and consideration of repeated procedures using the microdialysis probe. The remainder of the review is devoted to a survey of the recent literature concerning pharmacokinetic studies that apply the microdialysis sampling technique. While the majority of the pharmacokinetic studies that have utilized microdialysis have been done in the central nervous system, a growing number of applications are being found in a variety of peripheral tissue types, e.g. skin, muscle, adipose, eye, lung, liver, and blood, and these are considered as well. Given the rising interest in this technique, and the ongoing attempts to adapt it to pharmacokinetic studies, it is clear that microdialysis sampling will have an important place in studying drug disposition and metabolism.     

The Design and Validation of a Novel Intravenous Microdialysis Probe: Application to Fluconazole Pharmacokinetics in the Freely-Moving Rat Model

Purpose. The purpose of this study was to design and validate a concentric, flexible intravenous microdialysis probe to determine drug concentrations in blood from the inferior vena cava of a freely-moving animal model. Methods. An intravenous microdialysis probe was constructed using fused-silica tubing and an acrylonitrile/sodium methallyl sulfonate copolymer hollow fiber. The probe was tested in vitro for the recovery of fluconazole and UK-54,373, a fluconazole analog used for probe calibration by retrodialysis. Subsequent in vivo validation was done in rats (n = 7) that had a microdialysis probe inserted into the inferior vena cava via the femoral vein, and the femoral artery was cannulated for simultaneous blood sampling. Comparisons of fluconazole pharmacokinetic parameters resulting from the two sampling methods were performed at 2 and 10 days after probe implantation. Results. There were no statistical differences between the microdialysis sampling and conventional blood sampling methods for the T_1/2, Cl, Vdss, and dose-normalized AUC by paired t-test (p > 0.05) for repeated dosing at day 2 and day 10 after probe placement. The probe recovery, as determined by retrodialysis, significantly decreased over the ten day period. This finding indicates the necessity for frequent recovery determinations during a long-term blood microdialysis experiment. Conclusions. These results show that microdialysis sampling in the inferior vena cava using this unique and robust probe design provides an accurate method of determining blood pharmacokinetics in the freely-moving rat for extended experimental periods. The probe design allows for a simple surgical placement into the inferior vena cava which results in a more stable animal preparation for long-term sampling and repeated-measures experimental designs.     

On mathematical models of microdialysis: geometry, steady-state models, recovery and probe radius

Commonly used methods for microdialysis recovery measurement are reviewed and the zero flow and no net flux methods are suggested as the most robust in practice. Six different mathematical models of microdialysis assumptions are investigated and compared for varying dialysis probe radius. One transmitter (dopamine), three metabolites (DOPAC, HVA and 5HIAA) and two drugs (caffeine and theophylline) were studied. Histology and functional response to a drug were measured. Deficiencies were demonstrated for several of the models, the one best explaining experimental data includes both passive diffusion and active tissue regulation in a cylindrical symmetric geometry. The recovery decreased with decreasing probe radius but smaller probes caused less tissue injury. It is concluded that a mathematical model of microdialysis must include diffusional and physiological processes in order to accurately account for experimentally observed phenomena. The experiments also demonstrated that, for small brain nuclei, the size of the nucleus may influence the recovery.