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Quantitative Aspects of Nanodelivery Across the Blood-Brain Barrier: Exemplified with the Opioid Peptide DAMGO
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of nanocarriers is an intriguing approach in the development of efficacious treatment for brain disorders. The aim of the conducted research was to evaluate and quantify the impact of a liposomal nanocarrier formulation on the brain drug delivery. A novel approach for investigating the blood-brain barrier transport of liposomal DAMGO is presented, including in vivo microdialysis in rat, a high quality LC-MS/MS bioanalytical method and pharmacokinetic model analysis of the data. Factors limiting the brain distribution of the free peptide DAMGO were also investigated. Microdialysis, in combination with plasma sampling, made it possible to separate the released drug from the encapsulated and to quantify the active substance in both blood and brain interstitial fluid over time.

The opioid peptide DAMGO entered the brain to a limited extent, with a clearance out of the brain 13 times higher than the clearance into the brain. The brain to blood ratio of unbound drug was not affected when the efflux transporter inhibitors cyclosporine A and elacridar were co-administered with DAMGO. Nor was the transport affected in the in vitro Caco-2 assay using the same inhibitors. This indicates that DAMGO is not transported by P-glycoprotein (Pgp) or breast cancer resistant protein (Bcrp). The blood-brain barrier transport was significantly increased for DAMGO when formulated in liposomes, resulting in 2-3 fold higher brain to blood ratio of unbound DAMGO. The increased brain delivery was seen both for glutathione tagged PEGylated liposomes, as well as for PEGyalted liposomes without specific brain targeting. The improvement in brain delivery was observed only when DAMGO was encapsulated into the liposomes, thus excluding any effect of the liposomes themselves on the integrity of the blood-brain barrier. Modeling of the data provided additional mechanistic understanding of the brain uptake, showing that endocytosis or transcytosis of intact liposomes across the endothelial cell membranes were unlikely. A model describing fusion of the liposomes with the luminal membrane described the experimental data the best.

In conclusion, the studies presented in this thesis all contribute to an increased understanding of how to evaluate and improve brain delivery of CNS active drugs and contribute with important insights to the nanocarrier field.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 208
Keyword [en]
blood-brain barrier, liposomes, nanocarriers, brain delivery, pharmacokinetics, modeling and simulation, microdialysis, opioid peptide, DAMGO, LC-MS/MS
National Category
Pharmaceutical Sciences
Research subject
Pharmaceutical Science
Identifiers
URN: urn:nbn:se:uu:diva-267599ISBN: 978-91-554-9428-5 (print)OAI: oai:DiVA.org:uu-267599DiVA: diva2:873747
Public defence
2016-01-15, B42, Biomedicinskt centrum (BMC), Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-12-21 Created: 2015-11-24 Last updated: 2016-01-13
List of papers
1. Quantitative analysis of the opioid peptide DAMGO in rat plasma and microdialysis samples using liquid chromatography-tandem mass spectrometry
Open this publication in new window or tab >>Quantitative analysis of the opioid peptide DAMGO in rat plasma and microdialysis samples using liquid chromatography-tandem mass spectrometry
2012 (English)In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 900, 11-17 p.Article in journal (Refereed) Published
Abstract [en]

A liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) method for the quantification of the opioid peptide DAMGO in rat plasma, as well as DAMGO and the microdialysis recovery calibrator [13C2,15N]-DAMGO in microdialysis samples, is described. The microdialysis samples consisted of 15 μL Ringer solution containing 0.5% bovine serum albumin. Pretreatment of the samples involved protein precipitation with acetonitrile followed by dilution with 0.01% formic acid. The lower limits of quantification were 0.52 ng/mL and 0.24 ng/mL for DAMGO and [13C2,15N]-DAMGO respectively and the response was linear up to 5000 fold higher concentrations. The plasma samples (50 μL) were precipitated with acetonitrile containing the isotope labeled analog [13C2,15N]-DAMGO as internal standard. The method was linear in the range of 11–110,000 ng/mL. The separations were conducted on a HyPurity C18 column, 50 × 4.6 mm, 3 μm particle size, with a mobile phase consisting of acetonitrile, water and formic acid to the proportions of 17.5:82.5:0.01. Low energy collision dissociation tandem mass spectrometric (CID-MS/MS) analysis was carried out in the positive ion mode using multiple reaction monitoring (MRM) of the following mass transitions: m/z 514.2 → 453.2 for DAMGO and m/z 517.2 → 456.2 for [13C2,15N]-DAMGO. The intra-day precision and accuracy did not exceed 5.2% and 93–104% for both compounds and sample types described. The inter-day precision an accuracy were <6.8% and 95–105% respectively. The method described is simple, reproducible and suitable for the analysis of small sample volumes at low concentrations.

Keyword
Opioid peptide, DAMGO, LC-MS/MS, Microdialysis
National Category
Pharmaceutical Sciences
Research subject
Pharmacokinetics and Drug Therapy
Identifiers
urn:nbn:se:uu:diva-181430 (URN)10.1016/j.jchromb.2012.05.014 (DOI)000306881000002 ()
Available from: 2012-09-27 Created: 2012-09-24 Last updated: 2017-12-07Bibliographically approved
2. Enhanced Brain Delivery of the Opioid Peptide DAMGO in Glutathione PEGylated Liposomes: A Microdialysis Study
Open this publication in new window or tab >>Enhanced Brain Delivery of the Opioid Peptide DAMGO in Glutathione PEGylated Liposomes: A Microdialysis Study
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2013 (English)In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 10, no 5, 1533-1541 p.Article in journal (Refereed) Published
Abstract [en]

Glutathione PEGylated (GSH-PEG) liposomes were evaluated for their ability to enhance and prolong blood-to-brain drug delivery of the opioid peptide DAMGO (H-Tyr-d-Ala-Gly-MePhe-Gly-ol). An intravenous loading dose of DAMGO followed by a 2 h constant rate infusion was administered to rats, and after a washout period of 1 h, GSH-PEG liposomal DAMGO was administered using a similar dosing regimen. DAMGO and GSH-PEG liposomal DAMGO were also administered as a 10 min infusion to compare the disposition of the two formulations. Microdialysis made it possible to determine free DAMGO in brain and plasma, while the GSH-PEG liposomal encapsulated DAMGO was measured with regular plasma sampling. The antinociceptive effect of DAMGO was determined with the tail-flick method. All samples were analyzed using liquid chromatography–tandem mass spectrometry. The short infusion of DAMGO resulted in a fast decline of the peptide concentration in plasma with a half-life of 9.2 ± 2.1 min. Encapsulation in GSH-PEG liposomes prolonged the half-life to 6.9 ± 2.3 h. Free DAMGO entered the brain to a limited extent with a steady state ratio between unbound drug concentrations in brain interstitial fluid and in blood (Kp,uu) of 0.09 ± 0.04. GSH-PEG liposomes significantly increased the brain exposure of DAMGO to a Kp,uu of 0.21 ± 0.17 (p < 0.05). By monitoring the released, active substance in both blood and brain interstitial fluid over time, we were able to demonstrate that GSH-PEG liposomes offer a promising platform for enhancing and prolonging the delivery of drugs to the brain.

Keyword
drug delivery, nanocarrier, liposomes, blood-brain barrier, microdialysis, pharmacokinetics, antinociception, opioid peptide
National Category
Pharmaceutical Sciences
Research subject
Pharmacokinetics and Drug Therapy
Identifiers
urn:nbn:se:uu:diva-191593 (URN)10.1021/mp300272a (DOI)000318669600007 ()22934681 (PubMedID)
Available from: 2013-01-10 Created: 2013-01-10 Last updated: 2017-12-06Bibliographically approved
3. In vivo Functional Evaluation of Increased Brain Delivery of the Opioid Peptide DAMGO by Glutathione-PEGylated Liposomes
Open this publication in new window or tab >>In vivo Functional Evaluation of Increased Brain Delivery of the Opioid Peptide DAMGO by Glutathione-PEGylated Liposomes
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2016 (English)In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 33, no 1, 177-185 p.Article in journal (Refereed) Published
Abstract [en]

Purpose:

The purpose of this study was to evaluate formulation factors causing improvement in brain delivery of a small peptide after encapsulation into a targeted nanocarrier in vivo.

Methods:

The evaluation was performed in rats using microdialysis, which enabled continuous sampling of the released drug in both the brain (striatum) and blood. Uptake in brain could thereby be studied in terms of therapeutically active, released drug.

Results:

We found that encapsulation of the peptide DAMGO in fast-releasing polyethylene glycol (PEG)ylated liposomes, either with or without the specific brain targeting ligand glutathione (GSH), doubled the uptake of DAMGO into the rat brain. The increased brain delivery was observed only when the drug was encapsulated into the liposomes, thus excluding any effects of the liposomes themselves on the blood-brain barrier integrity as a possible mechanism. The addition of a GSH coating on the liposomes did not result in an additional increase in DAMGO concentrations in the brain, in contrast to earlier studies on GSH coating. This may be caused by differences in the characteristics of the encapsulated compounds and the composition of the liposome formulations. 

Conclusions:

We were able to show that encapsulation into PEGylated liposomes of a peptide with limited brain delivery could double the drug uptake into the brain without using a specific brain targeting ligand.  

Keyword
Brain delivery, liposomes, blood-brain barrier, microdialysis, opioid peptide
National Category
Pharmaceutical Sciences
Research subject
Pharmacokinetics and Drug Therapy
Identifiers
urn:nbn:se:uu:diva-267583 (URN)10.1007/s11095-015-1774-3 (DOI)000367343000014 ()26275529 (PubMedID)
Funder
Swedish Research Council, 521-2011-4339
Available from: 2015-11-24 Created: 2015-11-24 Last updated: 2017-12-01Bibliographically approved
4. Exploring Factors Causing Low Brain penetration of the Opioid Peptide DAMGO through Experimental Methods and Modeling
Open this publication in new window or tab >>Exploring Factors Causing Low Brain penetration of the Opioid Peptide DAMGO through Experimental Methods and Modeling
2016 (English)In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 13, no 4, 1258-1266 p.Article in journal (Refereed) Published
Abstract [en]

To advance the development of peptide analogues for improved treatment of pain, we need to learn more about the blood brain barrier transport of these substances. A low penetration into the brain, with an unbound brain to blood ratio, K-p,K-uu, of 0.08, is an important reason for the lack of effect of the enkephalin analogue DAMGO (H-Tyr-D-Ala-Gly-MePhe-Gly-ol) according to earlier findings. The aim of this study was to investigate the role of efflux transporters, metabolism in the brain, and/or elimination through interstitial fluid bulk flow for the brain exposure of DAMGO. The in vivo brain distribution of DAMGO was evaluated using microdialysis in the rat. Data were analyzed with population modeling which resulted in a clearance into the brain of 1.1 and an efflux clearance 14 mu L/min/g_brain. The efflux clearance was thus much higher than the bulk flow known from the literature. Coadministration with the efflux transporter inhibitors cyclosporin A and elacridar in vivo did not affect K-p,K-uu. The permeability of DAMGO in the Caco-2 assay was very low, of the same size as mannitol. The efflux ratio was <2 and not influenced by cyclosporin A or elacridar. These results indicate that the well-known efflux transporters Pgp and Bcrp are not responsible for the higher efflux of DAMGO, which opens up for an important role of other transporters at the BBB.

Keyword
CNS, blood-brain barrier, microdialysis, permeability, Pgp, population modeling, NONMEM, elacridar, cyclosporine A, efflux, pharmacokinetics
National Category
Pharmaceutical Sciences
Research subject
Pharmacokinetics and Drug Therapy
Identifiers
urn:nbn:se:uu:diva-267592 (URN)10.1021/acs.molpharmaceut.5b00835 (DOI)000373550600007 ()26898546 (PubMedID)
Funder
Swedish Research Council
Available from: 2015-11-24 Created: 2015-11-24 Last updated: 2017-12-01Bibliographically approved
5. Pharmacokinetic Considerations of Nanodelivery to the Brain: Using Modeling and Simulations to Predict Outcome of Liposomal Formulations
Open this publication in new window or tab >>Pharmacokinetic Considerations of Nanodelivery to the Brain: Using Modeling and Simulations to Predict Outcome of Liposomal Formulations
2016 (English)In: European Journal of Pharmaceutical Sciences, ISSN 0928-0987, E-ISSN 1879-0720, Vol. 92, 173-182 p.Article in journal (Refereed) Published
Abstract [en]

The use of nanocarriers is an intriguing solution to increase the brain delivery of novel therapeutics. The aim of this paper was to use pharmacokinetic analysis and simulations to identify key factors that determine the effective drug concentration-time profile at the target site in the brain. Model building and simulations were based on experimental data obtained from the administration of the opioid peptide DAMGO in glutathione tagged PEGylated liposomes to rats. Different pharmacokinetic models were investigated to explore the mechanisms of increased brain delivery. Concentration time profiles for a set of formulations with varying compound and carrier characteristics were simulated. By controlling the release rate from the liposome, the time profile and the extent of brain delivery can be regulated. The modeling did not support a mechanism of the liposomes passing the brain endothelial cell membrane in an intact form through endocytosis or transcytosis. The most likely process was found to be fusion of the liposome with the endothelial luminal membrane. The simulations revealed that low permeable compounds, independent on efflux, will gain the most from a nanocarrier formulation. The present model based approach is useful to explore and predict possibilities and limitations of carrier-based systems to the brain.

Keyword
Liposomes, Nanocarriers, Brain delivery, Pharmacokinetics, Active transport, Blood-brain barrier, Permeability, Release rate, Modeling and simulations
National Category
Pharmaceutical Sciences
Research subject
Pharmacokinetics and Drug Therapy
Identifiers
urn:nbn:se:uu:diva-267596 (URN)10.1016/j.ejps.2016.07.003 (DOI)000381833900019 ()27393342 (PubMedID)
Available from: 2015-11-24 Created: 2015-11-24 Last updated: 2017-12-01Bibliographically approved

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