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Interactions between Homopolypeptides and Lightly Cross-Linked Microgels
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 1, 522-528 p.Article in journal (Refereed) Published
Abstract [en]

The relative importance of electrostatic and nonelectrostatic interactions in peptide-microgel systems was evaluated by micromanipulator-assisted light microscopy, confocal microscopy, and circular dichroism. For this purpose, the interaction of various homopolypeptides with lightly cross-linked polyelectrolyte gel particles ( approximately 70 mum in diameter) was studied with focus on peptide-induced microgel deswelling and its relation to peptide distribution within the microgel particles. Negatively charged poly-l-glutamic acid (pGlu) and poly-l-aspartic acid (pAsp), as well as uncharged poly-l-proline (pPro) and poly-l-threonine (pThr), were found to not bind to negatively charged poly(acrylic acid) microgels under the conditions investigated, but were instead depleted from the microgel particles. Positively charged poly-l-arginine (pArg), poly-l-histidine (pHis), and poly-l-lysine (pLys), on the other hand, interacted strongly with the oppositely charged microgel particles and caused significant deswelling of these. In parallel, cationic acrylamidopropyltriethylammoniumchloride (APTAC) microgels bound negatively charged polypeptides to a much higher extent than positively charged and uncharged ones. These findings suggest that electrostatic interactions dominate peptide binding and resulting microgel deswelling in these systems. Nevertheless, although the amount of cationic peptide bound to the anionic microgel particles was similar for cationic pLys, pArg, and pHis, peptide-induced gel deswelling differed significantly, as did the change in peptide conformation after microgel binding and the peptide distribution within the microgels. These effects, as well as pH dependent binding and release of titrable pHis, are discussed in terms of the effects of the charge density of, and structural differences between, the cationic homopolypeptides on the interaction with the oppositely charged microgel particles.

Place, publisher, year, edition, pages
2009. Vol. 25, no 1, 522-528 p.
National Category
Pharmaceutical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-87656DOI: 10.1021/la8029984ISI: 000262176600086PubMedID: 19061315OAI: oai:DiVA.org:uu-87656DiVA: diva2:132985
Available from: 2009-01-07 Created: 2009-01-07 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Interaction Between Microgels and Oppositely Charged Peptides
Open this publication in new window or tab >>Interaction Between Microgels and Oppositely Charged Peptides
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lightly cross-linked polyelectrolyte microgels are materials with interesting properties for a range of applications. For instance, the volume of these particles can be drastically changed in response to pH, ionic strength, temperature, or the concentration of specific ions and metabolites. In addition, microgel particles can bind substantial amounts of oppositely charged substances, such as proteins and peptides, and release them upon changes in the external environment. Consequently, microgels have potential in catalysis, photonics, biomaterials, and not at least, as protective and stimuli-sensitive carriers for protein and peptide drugs.

In this thesis, the interaction between anionic microgels and cationic peptides was investigated by monitoring microgel deswelling and reswelling in response to peptide binding and release using micromanipulator-assisted light microscopy. In addition, peptide distribution in microgels was analyzed with confocal laser scanning microscopy and peptide uptake determined with solution depletion measurements. The aim of the thesis was to clarify how parameters such as peptide size, charge density, pH, ionic strength and hydrophobicity influences the peptide binding to, distribution in and release from, polyelectrolyte microgels.

Results obtained in this thesis show that electrostatic attraction is a prerequisite for interaction to occur although non-electrostatic contributions are responsible the finer details of the interactions. The size and charge density of the interacting peptides play a major role, as large and highly charged peptides are restricted to enter and interact with the microgel core, thus displaying a surface-confined distribution. The peptide-microgel interaction strength is highly reflected in the probability of peptides to be detached from the gel network. For instance, reducing the electrostatic interactions by adding salt induces significant peptide release of sufficiently small and moderately charged peptides, whereas longer and more highly charged peptides is retained in the microgel network due to the strong interaction, insufficient salt screening, and gel network pore size restriction. Decreasing the charge density of microgel network and/or peptides increases the probability for peptide detachment tremendously.

To summarize, interactions occurring in oppositely charged microgel-peptide systems can be tuned by varying parameters such as charge density and peptide size and through this, the peptide uptake, distribution and release can be controlled to alter the performance of microgels in peptide drug delivery.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 113
Keyword
antimicrobial peptides, binding, cationic peptides, confocal microscopy, deswelling, distribution, electrostatic, homopolypeptides, microgels, peptides, release, swelling
National Category
Pharmaceutical Sciences
Research subject
Pharmaceutical Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-109203 (URN)978-91-554-7635-9 (ISBN)
Public defence
2009-11-27, B21, BMC, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-11-06 Created: 2009-10-12 Last updated: 2009-11-06

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