Macromolecular Bioscience

Front Cover: The cover features research highlights, such as hydrolytic degradation behavior of poly(rac-lactide)-b-poly(propylene glycol)-b-poly(rac-lactide) dimethacrylate networks (Wischke et al.), poly(trimethylene carbonate)-based porous scaffolds with gyroid pore networks (Grijpma et al), and electrospun fibers based on bis(Upy-U)poly(epsilon-caprolactone) containing Upy-U S-peptides (Dankers et al.) presented in this issue of Macromolecular Bioscience, Advanced Functional Polymers for Medicine. Further details can be found on pages 1637, 1662, and 1706. Fotos by courtesy of P. Y. W. Dankers and D. W. Grijpma.

Back Cover: Chitosan nanoparticles with and without hyaluronic acid coating escape endolysosomal compartments during their acidification. The mechanism and kinetics of internalization of the nanoparticles were evaluated in a phagocytic in vitro model (macrophages) and in a non-phagocytic control (fibroblasts). Further details can be found in the article by N. M. Zaki, A. Nasti, and N. Tirelli* on page 1747.

In recent years, many amino acids derived biodegradable polymers have been intensely developed from natural amino acids. These polymers offer many advantageous features when used as carriers for drug delivery and in tissue engineering. This manuscript focuses on the recent advancements mainly in the area of synthesis and biomedical applications for these polymers.

The properties of a set of polymer networks from triblock precursors can be tailored depending on the precursor chain length and weight ratios of the poly(rac-lactide) and poly(propylene glycol) blocks. Wet-stage E moduli (37 °C) in the kPa range and a controlled hydrolytic degradation (pH = 7, 37 °C) with, e.g., linear mass loss and decrease in E modulus are observed.

The synthesis and use of photocrosslinkable lactone-based macromers for biomedical applications is reviewed. Photocrosslinkability has enabled various manufacturing methods to construct predesigned bioactive tissue-engineering scaffold architectures with high precision. Surface-erodible photocrosslinked polymers have been found to be potential materials for controlled-release applications.

From a recall of the criteria that have to be fulfilled when bringing a polymeric therapeutic system up to clinical and commercial levels of development, this article discusses the case of functional polymers tailor-made according to a strategy based on using metabolites as monomers or building blocks that can be eliminated from the body after in situ degradation: the so-called artificial biopolymers.

Resins based on poly(trimethylene carbonate) macromers of different molecular weights are formulated for application in stereolithography. It is shown that resins based on PTMC macromers with molecular weights below 20 150 g · mol⁻¹ can successfully be processed by stereolithography into designed solid and porous 3D structures using propylene carbonate as a non-reactive diluent.

Load-bearing soft tissues have limited capacity for self-repair, which leads to a chronic progression of damage that ultimately results in excessive joint pain and limited mobility. Here, the photo-encapsulation of viable cells in a biodegradable elastomer plus hydrogel composite scaffold is investigated as a possible replacement for such prosthetics.

It is shown that biodegradable fibrous scaffolds based on a novel functionalized polymer (pHMGCL) that is more hydrophilic than PCL possesses excellent properties in terms of degradation kinetics, processability via electrospinning, chondrocytes adhesion and differentiation. The results establish a basis for further implementation of this material in the field of cartilage tissue engineering.

Frontispiece: Size scale and crystallinity of fibre mesh can drastically affect the MSC behaviour. Solvent permittivity represents a powerful tool to design morphology (i.e., fibre size) and molecular folding (i.e., crystallinity) of micro/nanotextured PCL electrospun scaffolds. Further details can be found in the article by V. Guarino,* V. Cirillo, P. Taddei, M. A. Alvarez-Perez, and L. Ambrosio on page 1694.

The effect of solvent permittivity on the fibre morphology of poly(ε-caprolactone) electrospun membranes for tissue engineering applications is examined. Results indicate that the coupling of polymer and solvent components can drastically affect the final morphological appearance of electrospun fibres in terms of fibre size scale and bead formation.

The influence of processing parameters on the anchoring and bioactivity of ureidopyrimidinone-modified peptides incorporated in UPy-functionalized poly(ε-caprolactone) films is evaluated. Extraction experiments and a RNase S assay show a solvent dependency of the release of bioactives, and the bioactivity of the films. The importance of processing for the incorporation of UPy-U peptides is shown.

A “self-oscillating” gel that swells and deswells periodically under constant conditions without external switching is described. Autonomous mass-transport systems can be realized by utilizing the peristaltic motion of the self-oscillating gel. The influences of physical interactions between the self-oscillating gel and the loaded cargo on the transporting ability are studied.

Thermoresponsive polymers have a large number of potential uses in medicine. In this paper, the possible applications of these materials for delivery and release of cytotoxic agents for cancer therapy are explored. The state of the art for these materials is reviewed and emerging trends for the future are outlined.

Frontispiece: The synthesis and properties of photocleavable dendritic core/shell architectures based on hyperbranched polyglycerol with star-like oligoamine shells is described. The constructs bind DNA multivalently through electrostatic interaction. The release of DNA is triggered by 350 nm UV irradiation by photolytic change of the core/shell structure. Further details can be found in the article by W. Fischer, M. A. Quadir, A. Barnard, D. K. Smith, and R. Haag* on page 1736.

The synthesis and physicochemical investigation of multivalent and photolabile dendritic core/shell architectures based on hyperbranched polyglycerol with a star-like oligoamine shell is described. The structures are designed to bind DNA efficiently by electrostatic and multivalent interactions. The release of the DNA occurs by reducing the multivalent charge interaction by photolytic cleavage.

The endocytosis of chitosan nanoparticles (green) with and without hyaluronic acid-coating is studied in murine macrophages. Both coated and uncoated nanoparticles evade endolysosomal compartments (red), but the hyaluronic acid coating controls stability in media, cellular interactions and uptake kinetics.

The VEGF-blocking peptide WHLPFKC can potentially be used to inhibit angiogenesis in the treatment of cancer and maculopathy and in cartilage regeneration. The peptide is integrated in a poly(ε-lysine) dendron to improve its stability and to enhance its bioactivity thus leading to endothelial cell apoptosis and to regression of capillary-like structures in vitro.