Jan-Georg Rosenboom

Cyclic Polymer Grafts That Lubricate and Protect Damaged Cartilage

Tissue-reactive graft copolymers were designed to protect the cartilage against enzymatic degradation and restore its lubrication properties during the early stages of osteoarthritis (OA). The copolymers feature a poly(glutamic acid) (PGA) backbone bearing hydroxybenzaldehyde (HBA) functions and cyclic poly(2-methyl-2-oxazoline) (PMOXA) side chains. PGA-PMOXA-HBA species chemisorb on the degraded tissue via Schiff bases and expose the biopassive and lubricious PMOXA cyclic grafts at the interface. The smaller hydrodynamic radius by cyclic PMOXA side chains coupled to the intrinsic absence of chain ends generate denser and more lubricious films on cartilage when compared to those produced by copolymers bearing linear PMOXA. Topology effects demonstrate how the introduction of cyclic polymers within tissue-reactive copolymers substantially improve their tribological and biopassive properties, suggesting a plethora of possible applications for cyclic macromolecules in biomaterials formulations.

Design and characterization of ultrastable, biopassive and lubricious cyclic poly(2-alkyl-2-oxazoline) brushes

Bilayer polymer brushes presenting surface-bound poly(glycidyl methacrylate) (PGMA) films and interfacial cyclic poly(2-alkyl-2-oxazoline) (PAOXA) brushes show excellent biopassivity and lubrication, while displaying long-term stability in chemically harsh aqueous environments. Due to their lower radii of gyration (Rg), cyclic poly(2-methyl-2-oxazoline)s (PMOXAs) and poly(2-ethyl-2-oxazoline)s (PEOXAs) react at high temperatures with PGMA grafts producing ∼50% denser brushes compared to linear analogues featuring comparable molar masses. This generates significantly more hydrated brush interfaces, which quantitatively prevent unspecific surface contamination by biomolecules after several hours of exposure. In addition, the more compact and denser character of cyclic brushes imparts excellent lubricating properties to the bilayered coatings, with the more hydrophilic cyclic PMOXA interfaces reaching a coefficient of friction (μ) of 0.05 against a silica AFM probe in aqueous medium. In addition to their unique physicochemical properties, cyclic PMOXA and PEOXA brushes grafted on PGMA layers demonstrate extremely robust films, which could withstand one month incubation in phosphate buffered saline (PBS) solution, tap water or water from Lake Zurich.

Bottle-grade polyethylene furanoate from ring-opening polymerisation of cyclic oligomers

Polyethylene furanoate (PEF) represents a promising renewable resource-based bioplastic as replacement for fossil-based polyethylene terephthalate (PET) with improved material properties. However, the synthesis of PEF through conventional polycondensation remains challenging, since the time-intensive reaction leads to degradation and undesired discolouration of the product. Here we show the successful rapid synthesis of bottle-grade PEF via ring-opening polymerisation (ROP) from cyclic PEF oligomers within minutes, thereby avoiding degradation and discolouration. The melting point of such mixture of cyclic oligomers lies around 370u2009°C, well above the degradation temperature of PEF (~329u2009°C). This challenge can be overcome, exploiting the self-plasticising effect of the forming polymer itself (which melts around 220u2009°C) by initiation in the presence of a high boiling, yet removable, and inert liquid plasticiser. This concept yields polymer grades required for bottle applications (Mnu2009>u200930u2009kgu2009mol−1, conversion >xa095%, colour-free products), and can be extended to other diffusion-limited polymer systems.The synthesis of polyethylene furanoate, a promising renewable resource-based bioplastic, still has challenges. Here the authors show that bottle-grade polyethylene furanoate can be obtained within minutes from ring-opening polymerisation of its cyclic oligomers, thereby avoiding degradation and discolouration.

Robust and Biocompatible Functionalization of ZnS Nanoparticles by Catechol-Bearing Poly(2-Methyl-2-Oxazoline)s

Zinc sulfide (ZnS) nanoparticles (NPs) are particularly interesting materials for their electronic and luminescent properties. Unfortunately, their robust and stable functionalization and stabilization, especially in aqueous media, has represented a challenging and not yet completely accomplished task. In this work, we report the synthesis of colloidally stable, photoluminescent and biocompatible core-polymer shell ZnS and ZnS:Tb NPs by employing a water-in-oil miniemulsion (ME) process combined with surface functionalization via catechol-bearing poly-2-methyl-2-oxazoline (PMOXA) of various molar masses. The strong binding of catechol anchors to the metal cations of the ZnS surface, coupled with the high stability of PMOXA against chemical degradation, enable the formation of suspensions presenting excellent colloidal stability. This feature, combined with the assessed photoluminescence and biocompatibility, make these hybrid NPs suitable for optical bioimaging.