title: Considerations in binding diblock copolymers on hydrophilic alginate beads for providing an immunoprotective membrane.
abstract: Alginate-based microcapsules are being proposed for treatment of many types of diseases. A major obstacle however in the successes is that these capsules are having large lab-to-lab variations. To make the process more reproducible, we propose to cover the surface of alginate capsules with diblock polymers that can form polymer brushes. In the present study, we describe the stepwise considerations for successful application of diblock copolymer of polyethylene glycol (PEG) and poly-L-lysine (PLL) on the surface of alginate beads. Special procedures had to be designed as alginate beads are hydrophilic and most protocols are designed for hydrophobic biomaterials. The successful attachment of diblock copolymer and the presence of PEG blocks on the surface of the capsules were studied by fluorescence microscopy. Longer time periods, that is, 30-60 min, are required to achieve saturation of the surface. The block lengths influenced the strength of the capsules. Shorter PLL blocks resulted in less stable capsules. Adequate permeability of the capsules was achieved with poly(ethylene glycol)-block-poly(L-lysine hydrochloride) (PEG454-b-PLL100) diblock copolymers. The capsules were a barrier for immunoglobulin G. The PEG454-b-PLL100 capsules have similar mechanical properties as PLL capsules. Minor immune activation of nuclear factor κB in THP-1 monocytes was observed with both PLL and PEG454-b-PLL100 capsules prepared from purified alginate. Our results show that we can successfully apply block copolymers on the surface of hydrophilic alginate beads without interfering with the physicochemical properties.
authors.affiliation: Department of Polymer Chemistry, Zernike Institute for Advanced Materials, University of Groningen, 9747, AG Groningen, the Netherlands; Departments of Pathology and Laboratory Medicine, Section of Medical Biology, Division of Immunoendocrinology, University of Groningen, Hanzeplein 1, 9700, RB Groningen, The Netherlands.
authors.forename: Milica
authors.initials: M
authors.lastname: Spasojevic
authors.forename: Swapnil
authors.initials: S
authors.lastname: Bhujbal
authors.forename: Genaro
authors.initials: G
authors.lastname: Paredes
authors.forename: Bart J
authors.initials: BJ
authors.lastname: de Haan
authors.forename: Arend J
authors.initials: AJ
authors.lastname: Schouten
authors.forename: Paul
authors.initials: P
authors.lastname: de Vos
mesh_terms: D000464:Alginates / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism; D002214:Capsules; D002460:Cell Line; D004339:Drug Compounding; D020723:Glucuronic Acid / Q000737:chemistry / Q000276:immunology; D006603:Hexuronic Acids / Q000737:chemistry / Q000276:immunology; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007111:Immunity, Cellular; D009000:Monocytes / Q000276:immunology; D016328:NF-kappa B / Q000276:immunology; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000378:metabolism; D011107:Polylysine / Q000737:chemistry* / Q000276:immunology
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D002214:Capsules; D006603:Hexuronic Acids; D016328:NF-kappa B; D011107:Polylysine; D011092:Polyethylene Glycols; D020723:Glucuronic Acid
keywords: alginate; diblock copolymer; microencapsulation; physicochemical surface properties