Headaches and Magnesium: Mechanisms, Bioavailability, Therapeutic Efficacy and Potential Advantage of Magnesium Pidolate.

Magnesium deficiency may occur for several reasons, such as inadequate intake or increased gastrointestinal or renal loss. A large body of literature suggests a relationship between magnesium deficiency and mild and moderate tension-type headaches and migraines. A number of double-blind randomized placebo-controlled trials have shown that magnesium is efficacious in relieving headaches and have led to the recommendation of oral magnesium for headache relief in several national and international guidelines. Among several magnesium salts available to treat magnesium deficiency, magnesium pidolate may have high bioavailability and good penetration at the intracellular level. Here, we discuss the cellular and molecular effects of magnesium deficiency in the brain and the clinical evidence supporting the use of magnesium for the treatment of headaches and migraines.

Safety Assessment of PCA (2-Pyrrolidone-5-Carboxylic Acid) and Its Salts as Used in Cosmetics.

The Cosmetic Ingredient Review Expert Panel (Panel) reassessed the safety of 2-pyrrolidone-5-carboxylic acid (PCA) and sodium PCA; the Panel added 3 previously unreviewed salts (calcium, magnesium, and potassium) of PCA to this safety assessment. 2-Pyrrolidone-5-carboxylic acid and its salts are reported to function in cosmetics as skin conditioning agents-humectants. The Panel reviewed the data from the 1999 report of PCA and sodium PCA, as well as additional data included in this report, to determine the safety of these ingredients. The Panel concluded that PCA and its salts are safe in cosmetics in the present practices of use and concentration; additionally, these ingredients should not be used in cosmetic products in which N-nitroso compounds can be formed.

Development, validation and implementation of radio-HPLC methods for the P2X7-receptor-targeted [11C]GSK1482160 radiopharmaceutical.

A radio-analytical RP-HPLC method was developed and validated to support production of the P2X7-receptor-targeted [11C]GSK1482160 radiopharmaceutical. Method validation included characterization of retention times, peak shapes, linearity, accuracy, precision, selectivity, limits of detection and quantitation (UV signal), radiochemical stability, as well as analytical method range and robustness. The validated radio-HPLC method is suitable for the definition of [11C]GSK1482160 radiochemical identity, radiochemical purity, as well as molar activity, and is being employed in support of human studies with [11C]GSK1482160.

Pharmacokinetics of pidotimod in broiler chickens by UHPLC-MS/MS after oral and intravenous administration.

Pidotimod is widely used in children as an immune promoter but it has not been fully evaluated in animals. The pharmacokinetics of pidotimod and its oral bioavailability have not been described in broiler chickens. We developed a simple and sensitive UHPLC-MS/MS assay for rapid determination of pidotimod levels in chicken blood. Recoveries were nearly 100% and the coefficients of accuracy and precision were minimal. Healthy broiler chickens were given 10 mg/kg pidotimod either orally or intravenously. The oral pidotimod was rapidly absorbed (time to reach maximum concentration, 1.25 h) and rapidly eliminated (the mean residence time was 3.2 h). A noncompartmental analysis of the intravenous route indicated a mean plasma clearance of 2.2 L (h kg)-1 with an estimated mean volume of distribution at steady state of 12.69 L/kg. The bioavailability of pidotimod after oral dosing was 27%.

Characterization of 11C-GSK1482160 for Targeting the P2X7 Receptor as a Biomarker for Neuroinflammation.

The purinergic receptor subtype 7 (P2X7R) represents a novel molecular target for imaging neuroinflammation via PET. GSK1482160, a potent P2X7R antagonist, has high receptor affinity, high blood-brain barrier penetration, and the ability to be radiolabeled with 11C. We report the initial physical and biologic characterization of this novel ligand. Methods:11C-GSK1482160 was synthesized according to published methods. Cell density studies were performed on human embryonic kidney cell lines expressing human P2X7R (HEK293-hP2X7R) and underwent Western blotting, an immunofluorescence assay, and radioimmunohistochemistry analysis using P2X7R polyclonal antibodies. Receptor density and binding potential were determined by saturation and association-disassociation kinetics, respectively. Peak immune response to lipopolysaccharide treatment in mice was determined in time course studies and analyzed via Iba1 and P2X7R Western blotting and Iba1 immunohistochemistry. Whole-animal biodistribution studies were performed on saline- or lipopolysaccharide-treated mice at 15, 30, and 60 min after radiotracer administration. Dynamic in vivo PET/CT was performed on the mice at 72 h after administration of saline, lipopolysaccharide, or lipopolysaccharide + blocking, and 2-compartment, 5-parameter tracer kinetic modeling of brain regions was performed. Results: P2X7R changed linearly with concentrations or cell numbers. For high-specific-activity 11C-GSK1482160, receptor density and Kd were 1.15 ± 0.12 nM and 3.03 ± 0.10 pmol/mg, respectively, in HEK293-hP2X7R membranes. Association constant kon, dissociation constant koff, and binding potential (kon/koff) in HEK293-hP2X7R cells were 0.2312 ± 0.01542 min-1⋅nM-1, 0.2547 ± 0.0155 min-1, and 1.0277 ± 0.207, respectively. Whole-brain Iba1 expression in lipopolysaccharide-treated mice peaked by 72 h on immunohistochemistry, and Western blot analysis of P2X7R for saline- and lipopolysaccharide-treated brain sections showed a respective 1.8- and 1.7-fold increase in signal enhancement at 72 h. Biodistribution of 11C-GSK1482160 in saline- and lipopolysaccharide-treated mice at 72 h was statistically significant across all tissues studied. In vivo dynamic 11C-GSK1482160 PET/CT of mice at 72 h after administration of saline, lipopolysaccharide, or lipopolysaccharide + blocking showed a 3.2-fold increase and 97% blocking by 30 min. The total distribution volumes for multiple cortical regions and the hippocampus showed statistically significant increases and were blocked by an excess of authentic standard GSK1482160. Conclusion: The current study provides compelling data that support the suitability of 11C-GSK1482160 as a radioligand targeting P2X7R, a biomarker of neuroinflammation.

Advantage of population pharmacokinetic method for evaluating the bioequivalence and accuracy of parameter estimation of pidotimod.

OBJECTIVE: This study was aimed at exploring the accuracy of population pharmacokinetic method in evaluating the bioequivalence of pidotimod with sparse data profiles and whether this method is suitable for bioequivalence evaluation in special populations such as children with fewer samplings. Methods In this single-dose, two-period crossover study, 20 healthy male Chinese volunteers were randomized 1 : 1 to receive either the test or reference formulation, with a 1-week washout before receiving the alternative formulation. Noncompartmental and population compartmental pharmacokinetic analyses were conducted. Simulated data were analyzed to graphically evaluate the model and the pharmacokinetic characteristics of the two pidotimod formulations. Various sparse sampling scenarios were generated from the real bioequivalence clinical trial data and evaluated by population pharmacokinetic method. RESULTS: The 90% confidence intervals (CIs) for AUC0-12h, AUC0-∞, and Cmax were 97.3 - 118.7%, 96.9 - 118.7%, and 95.1 - 109.8%, respectively, within the 80 - 125% range for bioequivalence using noncompartmental analysis. The population compartmental pharmacokinetics of pidotimod were described using a one-compartment model with first-order absorption and lag time. In the comparison of estimations in different dataset, the estimation of random three- and< fixed four-point sampling strategies can provide results similar to those obtained through rich sampling. The nonlinear mixed-effects model requires fewer data points. Moreover, compared with the noncompartmental analysis method, the pharmacokinetic parameters can be more accurately estimated using nonlinear mixed-effects model. CONCLUSIONS: The population pharmacokinetic modeling method was used to assess the bioequivalence of two pidotimod formulations with relatively few sampling points and further validated the bioequivalence of the two formulations. This method may provide useful information for regulating bioequivalence evaluation in special populations.

A robust LC-MS/MS method for the determination of pidotimod in different biological matrixes and its application to in vivo and in vitro pharmacokinetic studies.

Pidotimod, (R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, was frequently used to treat children with recurrent respiratory infections. Preclinical pharmacokinetics of pidotimod was still rarely reported to date. Herein, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine pidotimod in rat plasma, tissue homogenate and Caco-2 cells. In this process, phenacetin was chosen as the internal standard due to its similarity in chromatographic and mass spectrographic characteristics with pidotimod. The plasma calibration curves were established within the concentration range of 0.01-10.00µg/mL, and similar linear curves were built using tissue homogenate and Caco-2 cells. The calibration curves for all biological samples showed good linearity (r>0.99) over the concentration ranges tested. The intra- and inter-day precision (RSD, %) values were below 15% and accuracy (RE, %) was ranged from -15% to 15% at all quality control levels. For plasma, tissue homogenate and Caco-2 cells, no obvious matrix effect was found, and the average recoveries were all above 75%. Thus, the method demonstrated excellent accuracy, precision and robustness for high throughput applications, and was then successfully applied to the studies of absorption in rat plasma, distribution in rat tissues and intracellular uptake characteristics in Caco-2 cells for pidotimod.

Distribution in Rats Internal Organs of Intraperitoneally Given 125I-Labeled Heptapeptide [2-8]-Leucopyrokinin ([2-8]-LPK), a Truncated Analog of Insect Neuropeptide Leucopyrokinin.

BACKGROUND: It was previously found that synthetic, insect-derived octapeptide leucopyrokinin (LPK) applied directly into the lateral brain ventricle induced a significant antinociceptive effect in rats. Its synthetic truncated analog heptapeptide [2-8]-leucopyrokinin displayed a stronger antinociceptive effect in comparison to native LPK. Moreover it was previously found a high accumulation of these both 125I-labeled peptides in adrenals, as well as in hypothalamus and in hippocampus of rats brain. OBJECTIVES: The aim of the present study was to assess the distribution of 125I-labeled [2-8]-leucopyrokinin in rats' internal organs an in several parts of the brain after peripheral - intraperitoneal (i.p.) administration. MATERIAL AND METHODS: The study was performed on male Wistar rats. A synthetic [2-8]-leucopyrokinin ([2-8]-LPK) was iodinated with Na125I. On the day of experiment a solution of 125I-[2-8]-LPK was i.p. injected and the next after 1 and 24 h animals were sacrificed by decapitation. Radioactivity levels in samples of parts of the brain and of internal organs were determined by counter Gamma Auto Count. RESULTS: A uniform, low accumulation 125I-[2-8]-LPK was found in evaluated samples of the brain and in internal organs. CONCLUSIONS: The results of the present study indicate a weak penetration into the brain and internal organs of intraperitoneally applied 125I-[2-8]-LPK in rats and correspond with previously determined weak biological effects of i.p. injected LPK and [2-8]-LPK.

Selective CB2 receptor agonists. Part 2: Structure-activity relationship studies and optimization of proline-based compounds.

Through a ligand-based pharmacophore model (S)-proline based compounds were identified as potent cannabinoid receptor 2 (CB2) agonists with high selectivity over the cannabinoid receptor 1 (CB1). Structure-activity relationship investigations for this compound class lead to oxo-proline compounds 21 and 22 which combine an impressive CB1 selectivity profile with good pharmacokinetic properties. In a streptozotocin induced diabetic neuropathy model, 22 demonstrated a dose-dependent reversal of mechanical hyperalgesia.

Intracerebroventricular administration of chicken glucagon-like peptide-2 potently suppresses food intake in chicks.

Glucagon-related peptides, such as glucagon-like peptide (GLP)-1, GLP-2 and oxyntomodulin (OXM), are processed from an identical precursor proglucagon. In mammals, all of these peptides are suggested to be involved in the central regulation of food intake. We previously showed that intracerebroventricular administration of chicken OXM and GLP-1 significantly suppressed food intake in chicks. Here, we show that central administration of chicken GLP-2 potently suppresses food intake in chicks. Male 8-day-old chicks (Gallus gallus domesticus) were used in all experiments. Intracerebroventricular administration of chicken GLP-2 significantly suppressed food intake in chicks. Plasma glucose concentration was significantly decreased by chicken GLP-2, whereas plasma nonesterified fatty acid concentration was significantly increased. Intracerebroventricular administration of chicken GLP-2 did not affect plasma corticosterone concentration. In addition, the anorexigenic effect of GLP-2 was not reversed by the corticotropin-releasing factor (CRF) receptor antagonist α-helical CRF, suggesting that CRF is not a downstream mediator of the anorexigenic pathway of GLP-2 in chicks. Intracerebroventricular administration of an equimolar amount of GLP-1 and GLP-2, but not OXM, significantly suppressed food intake in both broiler and layer chicks. All our findings suggest that GLP-2 functions as a potent anorexigenic peptide in the brain, as well as GLP-1, in chicks.

Bioequivalence evaluation of two formulations of pidotimod using a limited sampling strategy.

The aim of this study was to develop a limited sampling strategy (LSS) to assess the bioequivalence of two formulations of pidotimod. A randomized, two-way, cross-over study was conducted in healthy Chinese volunteers to compare two formulations of pidotimod. A limited sampling model was established using regression models to estimate the pharmacokinetic parameters and assess the bioequivalence of pidotimod. The model was internally validated by the Jack-knife method and graphical methods. The traditional non-compartmental method was also used to analyze the data and compared with LSS method. The results indicate that following oral administration of a single 800 mg dose, the plasma AUC(0-12 h) and C(max) of pidotimod can be predicted accurately using only two to four plasma samples. The bioequivalence assessment based on the LSS models provided results very similar to that obtained using all the observed concentration-time data points and indicate that the two pidotimod formulations were bioequivalent. A LSS method for assessing the bioequivalence of pidotimod formulations was established and proved to be applicable and accurate. This LSS method could be considered appropriate for a pidotimod bioequivalence study, providing an inexpensive cost of sampling acquisition and analysis. And the methodology presented here may also be applicable to bioequivalence evaluation of other medications.

Quantitative determination of pidotimod in human plasma by liquid chromatography tandem mass spectrometry: application to a bioequivalence study.

A highly sensitive and simple LC-MS/MS method after one-step protein precipitation was developed and validated for determination of pidotimod (CAS 121808-62-6) in human plasma using dextrophan (CAS 125-73-5) as internal standard (IS). Pidotimod and IS were separated on a YMC-ODS-AQ C18 column using 0.5% formic acid and methanol as a mobile phase at a flow rate of 0.3 mL/min. Detection was performed on positive ion mode of the transitions at 245.0→134.0 for pidotimod and 258.1→157.0 for IS by selected reaction monitoring (SRM). The assay exhibited a linear range of 0.05-10.0 µg/mL. The lower limit of quantification were 0.05 µg/mL. Validation results indicated that the accuracy as determined from quality control samples was in the range of - 4.00-6.48%. Intra-day and inter-day precision was ≤ 8.35% and ≤ 8.00%, respectively. The developed method was successfully applied to a bioequivalence study in 20 healthy Chinese volunteers following a single oral dose of 800 mg pidotimod. The simple, inexpensive protein precipitation and high-throughput method makes it a suitable and valuable tool in the investigation of the clinical pharmacokinetics and bioequivalence.

Water-in-oil-in-water double emulsions: an excellent delivery system for improving the oral bioavailability of pidotimod in rats.

The aims of this study were to prepare fine pidotimod-containing water-in-oil-in-water (W/O/W) double emulsions and to investigate the possibility of those emulsions as a delivery system for promoting the oral bioavailability of pidotimod. A modified two-step emulsification procedure was applied to prepare the double emulsions using medium-chain triglyceride as the oil phase, Tween 80 as the hydrophilic emulsifier, and Span 80 alone or in combination with different amount of phospholipids as the lipophilic emulsifiers. A fine W/O/W emulsion, with the encapsulation efficiency of 82 ± 3.4%, mean oil-droplet diameter of 3.93 ± 0.25 µm, and viscosity of 36.4 ± 0.93 mPa · s at 25 °C and 300 s(-1), was stable for 1 month at 4 °C. In addition, the oral bioavailability of pidotimod in rats, after intragastric administration of W/O/W double emulsions, was significantly higher than that of pidotimod control solution. Moreover, the maximum uptake time was significantly prolonged, suggesting an extra absorption pathway for W/O/W emulsions: a lymphatic circulation pathway. Those results demonstrated that W/O/W emulsions could become a potential formulation for improving the oral bioavailability of poorly absorbable drugs and suggested an important technology platform for the oral administration of peptide and peptidomimetic drugs.

Transport via SLC5A8 (SMCT1) is obligatory for 2-oxothiazolidine-4-carboxylate to enhance glutathione production in retinal pigment epithelial cells.

PURPOSE: To evaluate the role of SLC5A8 in the transport of 2-oxothiazolidine-4-carboxylate (OTC) and to determine whether OTC augments glutathione production in RPE cells, thereby providing protection against oxidative stress. METHODS: SLC5A8-mediated transport of OTC was monitored in Xenopus laevis oocytes by electrophysiological means. Saturation kinetics, Na(+)-activation kinetics, and inhibition by ibuprofen were analyzed by monitoring OTC-induced currents as a measure of transport activity. Oxidative stress was induced in ARPE-19 cells and primary RPE cells isolated from wild type and Slc5a8(-/-) mouse retinas using H(2)O(2), and the effects of OTC on cell death and intracellular glutathione concentration were examined. RESULTS: Heterologous expression of human SLC5A8 in X. laevis oocytes induced Na(+)-dependent inward currents in the presence of OTC under voltage-clamp conditions. The transport of OTC via SLC5A8 was saturable, with a K(t) of 104 ± 3 µM. The Na(+)-activation kinetics was sigmoidal with a Hill coefficient of 1.9 ± 0.1, suggesting involvement of two Na(+) in the activation process. Ibuprofen, a blocker of SLC5A8, inhibited SLC5A8-mediated OTC transport; the concentration necessary for half-maximal inhibition was 17 ± 1 µM. OTC increased glutathione levels and protected ARPE-19 and primary RPE cells isolated from wild type mouse retinas from H(2)O(2)-induced cell death. These effects were abolished in primary RPE isolated from Slc5a8(-/-) mouse retinas. CONCLUSIONS: OTC is a transportable substrate for SLC5A8. OTC augments glutathione production in RPE cells, thereby protecting them from oxidative damage. Transport via SLC5A8 is obligatory for this process.

Self-double-emulsifying drug delivery system (SDEDDS): a new way for oral delivery of drugs with high solubility and low permeability.

Water-in-oil-in-water (w/o/w) double emulsions are potential for enhancing oral bioavailability of drugs with high solubility and low permeability, but their industrial application is limited due to the instability. Herein, we developed a novel formulation, self-double-emulsifying drug delivery systems (SDEDDS) by formulating mixtures of hydrophilic surfactants and water-in-oil (w/o) emulsions, which were easier to be stable through formulations optimization. SDEDDS can spontaneously emulsify to water-in-oil-in-water (w/o/w) double emulsions in the mixed aqueous gastrointestinal environment, with drugs encapsulated in the internal water phase of the double emulsions. We employed SDEDDS to improve the oral absorption of pidotimod, a peptide-like drug with high solubility and low permeability. The optimized pidotimod-SDEDDS were found to be stable up to 6 months under 25°C. Plasma concentration-time profiles from pharmacokinetic studies in rats dosed with SDEDDS showed 2.56-fold (p<0.05) increased absorption of pidotimod, compared to the pidotimod solution. Histopathologic studies confirmed that SDEDDS exerted absorption promoting effect without serious local damages. These studies demonstrate that SDEDDS may be a promising strategy for peroral delivery of peptide and peptidomimetic drugs.

In vitro degradation and antitumor activity of oxime bond-linked daunorubicin-GnRH-III bioconjugates and DNA-binding properties of daunorubicin-amino acid metabolites.

Bioconjugates with receptor-mediated tumor-targeting functions and carrying cytotoxic agents should enable the specific delivery of chemotherapeutics to malignant tissues, thus increasing their local efficacy while limiting the peripheral toxicity. In the present study, gonadotropin-releasing hormone III (GnRH-III; Glp-His-Trp-Ser-His-Asp-Trp-Lys-Pro-Gly-NH(2)) was employed as a targeting moiety to which daunorubicin was attached via oxime bond, either directly or by insertion of a GFLG or YRRL tetrapeptide spacer. The in vitro antitumor activity of the bioconjugates was determined on MCF-7 human breast and HT-29 human colon cancer cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Their degradation/stability (1) in human serum, (2) in the presence of cathepsin B and (3) in rat liver lysosomal homogenate was analyzed by liquid chromatography in combination with mass spectrometry. The results show that (1) all synthesized bioconjugates have in vitro antitumor effect, (2) they are stable in human serum at least for 24 h, except for the compound containing an YRRL spacer and (3) they are hydrolyzed by cathepsin B and in the lysosomal homogenate. To investigate the relationship between the in vitro antitumor activity and the structure of the bioconjugates, the smallest metabolites produced in the lysosomal homogenate were synthesized and their binding to DNA was assessed by fluorescence spectroscopy. Our data indicate that the incorporation of a peptide spacer in the structure of oxime bond-linked daunorubicin-GnRH-III bioconjugates is not required for their antitumor activity. Moreover, the antitumor activity is influenced by the structure of the metabolites (daunorubicin-amino acid derivatives) and their DNA-binding properties.

Substituted 4-carboxymethylpyroglutamic acid diamides as potent and selective inhibitors of fibroblast activation protein.

Fibroblast activation protein (FAP) belongs to the prolyl peptidase family. FAP inhibition is expected to become a new antitumor target. Most known FAP inhibitors often resemble the dipeptide cleavage products, with a boroproline at the P1 site; however, these inhibitors also inhibit DPP-IV, DPP-II, DPP8, and DPP9. Potent and selective FAP inhibitor is needed in evaluating that FAP as a therapeutic target. Therefore, it is important to develop selective FAP inhibitors for the use of target validation. To achieve this, optimization of the nonselective DPP-IV inhibitor 8 led to the discovery of a new class of substituted 4-carboxymethylpyroglutamic acid diamides as FAP inhibitors. SAR studies resulted in a number of FAP inhibitors having IC(50) of <100 nM with excellent selectivity over DPP-IV, DPP-II, DPP8, and DPP9 (IC(50) > 100 µM). Compounds 18a, 18b, and 19 are the only known potent and selective FAP inhibitors, which prompts us to further study the physiological role of FAP.

Negligible effect of oral garlic oil on the oral absorption of pyridoxine in metadoxine in rats.

Metadoxine [an ion-pair between pyridoxine and pyrrolidone carboxylate (PCA)] plus garlic oil treatment synergistically reduces alcoholic steatosis compared to each agent alone. We evaluated the effect of garlic oil on the pharmacokinetics of pyridoxine. After the oral administration of metadoxine, the total area under the plasma concentration-time curve from time zero to time infinity (AUC) and the peak plasma concentration (C(max)) of pyridoxine were significantly greater (by 40.6%) and higher (by 63.9%), respectively, than after oral administration of pyridoxine plus PCA. Oral metadoxine plus garlic oil also gave larger AUC (31.8%) and higher C(max) (64.9%) than pyridoxine plus PCA. However, garlic oil did not change the AUC or C(max) of pyridoxine in metadoxine. Thus, garlic oil does not enhance the metadoxine activity by affecting the absorption of pyridoxine.

High-performance liquid chromatography-tandem mass spectrometry for the determination of pidotimod in human plasma and its application to a pharmacokinetic study.

A selective, rapid and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the first time to determine pidotimod in human plasma and applied to a pharmacokinetic study. Diphenhydramine was used as the internal standard (I.S.). Sample pretreatment involved in one-step protein precipitation (PPT) with methanol of 0.1 mL plasma. The analysis was carried out on an Ultimate XB-C(8) column with mobile phase of methanol-water containing 0.5% formic acid (65:35, v/v). The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. Each plasma sample was chromatographed within 4.5 min. The linear calibration curves were obtained in the concentration range of 0.05-20.00 microg/mL (r(2) > or = 0.99) with the lower limit of quantification (LLOQ) of 0.0500 microg/mL. The intra- and inter-day precision (relative standard deviation, R.S.D.) values were below 15% and accuracy (relative error, R.E.) was from -5.1% to 3.9% at all quality control (QC) levels. The method was applicable to clinical pharmacokinetic study of pidotimod in healthy volunteers after oral administration.

Preparation and brain delivery property of biodegradable polymersomes conjugated with OX26.

A novel drug carrier for brain delivery, poly(ethyleneglycol)-poly(epsilon-caprolactone) (PEG-PCL) polymersomes conjugated with mouse-anti-rat monoclonal antibody OX26 (OX26-PO), was developed and its brain delivery property was evaluated. The diblock copolymers of methoxy-PEG-PCL and Maleimide-PEG-PCL were synthesized and applied to prepare polymersomes (PO) which were verified by direct cryogenic temperature transmission electron micrograph (Cryo-TEM) imaging. The TEM examination and dynamic light scattering results showed that OX26-PO had a round and vesicle-like shape with a mean diameter around 100 nm. Coupling of OX26 with PO was confirmed by immuno-gold labeling of OX26 visualized under the TEM and X-ray photoelectron spectroscopy test. The surface OX26 densities were obtained from enzyme-linked immunosorbant assay. The result of brain delivery in rats proved that the increase of surface OX26 density of OX26-PO decreased blood AUC. The optimized OX26 number conjugated per polymersome was 34, which can acquire the greatest blood-brain barrier (BBB) permeability surface area product and percentage of injected dose per gram brain (%ID/g brain). Furthermore, NC-1900, as a model peptide, was encapsulated into OX26(34)-PO and improved the scopolamine-induced learning and memory impairments in a water maze task via i.v. administration. These results indicated that OX26(34)-PO is a promising carrier for peptide brain delivery.