Search results for "bioengineering"

Effect of Core-Crosslinking on Protein Corona Formation on Polymeric Micelles.

2021

Most nanomaterials acquire a protein corona upon contact with biological fluids. The magnitude of this effect is strongly dependent both on surface and structure of the nanoparticle. To define the contribution of the internal nanoparticle structure, protein corona formation of block copolymer micelles with poly(N-2-hydroxypropylmethacrylamide) (pHPMA) as hydrophilic shell, which are crosslinked-or not-in the hydrophobic core is comparatively analyzed. Both types of micelles are incubated with human blood plasma and separated by asymmetrical flow field-flow fractionation (AF4). Their size is determined by dynamic light scattering and proteins within the micellar fraction are characterized by…

Heparin-Based Nanocapsules as Potential Drug Delivery Systems

2015

Herein, the synthesis and characterization of heparin-based nanocapsules (NCs) as potential drug delivery systems is described. For the synthesis of the heparin-based NCs, the versatile method of miniemulsion polymerization at the droplets interface was achieved resulting in narrowly distributed NCs with 180 nm in diameter. Scanning and transmission electron microscopy images showed clearly NC morphology. A highly negative charge density for the heparin-based NCs was determined by measuring the electro-kinetic potential. Measuring the activated clotting time demonstrated the biological intactness of the polymeric shell. The ability of heparin-based NCs to bind to antithrombin (AT III) was i…

Tetrazine- and trans -cyclooctene-functionalised polypept(o)ides for fast bioorthogonal tetrazine ligation

2020

The inverse electron demand Diets-Alder (IEDDA) reaction-initiated ligation between 1,2,4,5-tetra-zines (Tz) and trans-cyclooctenes (TCO) is one of the fastest bioorthogonal reactions known today and is therefore increasingly used for in vivo click chemistry. Described herein is the synthesis of Tz- and TCO-functionalised polypeptides, polypeptoids and polypeptide-block-polypeptoids (polypept(o) ides) by ring-opening polymerisation of the corresponding N-carboxyanhydrides using Tz- or TCO-functional amine initiators. Despite the reactivity of tetrazines, polymers with low dispersity and high end group integrity can be obtained as observed by gel permeation chromatography (GPC), nuclear magn…

From Polymers to Functional Biomaterials.

2017

Rheology of Sodium Hyaluronate Saline Solutions for Ophthalmic Use

2007

The aim of this work was to investigate the rheological properties of different saline solutions of sodium hyaluronate (NaHA) with special interest for medical applications. The experimental results were compared with literature data for commercial ophthalmic viscosurgical devices (OVDs) used in cataract surgery. We offer some tools to tailor the rheological behavior of OVDs for different purposes. We have investigated to which extent surgical requirements can be fulfilled by adjusting either the molecular weight of NaHA or its concentration, parameters that are in some respects equivalent but not in others. Furthermore, we demonstrate that moduli and complex viscosities of NaHA saline solu…

Tuning the upper critical solution temperature behavior of poly(methyl methacrylate) in aqueous ethanol by modification of an activated ester comonom…

2012

A statistical copolymer of methyl methacrylate (MMA) and pentafluorophenyl methacrylate (PFPMA, 6 mol%) exhibits upper critical solution temperature (UCST) behavior in aqueous ethanol solutions tunable by post-polymerization modification with different amines. The phase transition behavior of the obtained copolymers in aqueous ethanol was evaluated in detail. As expected, all copolymers reveal an upper critical solution temperature with 55 vol% or higher ethanol content. Furthermore, the solubility in aqueous ethanol of the copolymer can be increased by the introduction of hydrophilic moieties. When hydrophobic substituents are introduced a decrease in solubility was observed with low conte…

Water-soluble and redox-responsive hyperbranched polyether copolymers based on ferrocenyl glycidyl ether

2015

Water-soluble copolymers of ferrocenyl glycidyl ether (fcGE) and glycidol were prepared via anionic ring-opening multibranching polymerization (ROMBP). The resulting hyperbranched materials with molecular weights (Mn) of 3500 to 12 300 g mol−1 and relatively narrow molecular weight distributions (Mw/Mn = 1.40–1.69) exhibit both temperature- as well as redox-responsive behavior, which was studied via turbidity measurements. The cloud point temperatures (Tc) were adjusted between 45 and 60 °C through variation of the fcGE comonomer content. Additionally, these Tcs can be increased by the addition of an oxidizing agent. The extent of oxidation of the materials was quantified by Mosbauer spectr…

Towards bio-based tapered block copolymers: the behaviour of myrcene in the statistical anionic copolymerisation

2019

To explore the potential of myrcene (Myr) as a bio-based monoterpene comonomer for styrenic copolymers and to establish its general applicability for the carbanionic copolymerisation, several statistical copolymerisations of myrcene and common monomers like isoprene (I), styrene (S) and 4-methylstyrene (4MS) were carried out in cyclohexane and monitored by in situ1H NMR spectroscopy. Real-time NMR kinetic studies permitted the determination of the reactivity ratios and the composition profile for each monomer combination. While the copolymerisation of Myr/I yielded a gradient copolymer and reactivity ratios of moderate disparity (rMyr = 4.4; rI = 0.23), the statistical copolymerisation of M…

Overcoming the PEG-addiction: well-defined alternatives to PEG from structure-property relationships to better defined therapeutics

2011

Synthetic methods in polymer chemistry have evolved tremendously during the last decade. Nowadays more and more attention is devoted to the application of those tools in the development of the next generation of nanomedicines. Nevertheless, poly(ethylene glycol) (PEG) remains the most frequently used polymer for biomedical applications. In this review, we try to summarize recent efforts and developments in controlled polymerisation techniques that may allow alternatives to PEG based systems and can be used to improve the properties of future polymer therapeutics.

Vinyl ferrocenyl glycidyl ether: an unprotected orthogonal ferrocene monomer for anionic and radical polymerization

2015

The first orthogonal ferrocene monomer, vinyl ferrocenyl glycidyl ether (VfcGE), for both anionic and radical polymerization – without the need of a protection group – is presented. Anionic ring-opening copolymerization of VfcGE and ethylene oxide (EO) generates stimuli-responsive, multifunctional poly[(vinyl ferrocenyl glycidyl ether)-co-(ethylene oxide)] (P[VfcGE-co-EO]) copolymers (molecular weights of ca. 7500 g mol−1 and low molecular weight dispersities (Đ ≤ 1.14)). The amount of the equimolar ferrocenyl and vinyl groups are controlled by the comonomer ratio up to 15.4 mol% VfcGE. The pendant vinyl groups of P[VfcGE-co-EO] were post-modified with 3-mercaptopropionic acid via thiol–ene…