Controlling integrin-based adhesion to a degradable electrospun fibre scaffold via SI-ATRP

Synthetic strategies to enhance the long-term stability of polymer brush coatings

High-density, end-anchored macromolecules that form so-called polymer brushes are popular components of bio-inspired surface coatings. In a bio-memetic approach, they have been utilized to reduce friction, repel contamination and control...

Supramolecular Additive-Initiated Controlled Atom Transfer Radical Polymerization of Zwitterionic Polymers on Ureido-pyrimidinone-Based Biomaterial Surfaces

Surface-initiated controlled radical polymerization is a popular technique for the modification of biomaterials with, for example, antifouling polymers. Here, we report on the functionalization of a supramolecular biomaterial with zwitterionic poly(sulfobetaine methacrylate) via atom transfer radical polymerization from a macroinitiator additive, which is embedded in the hard phase of the ureido-pyrimidinone-based material. Poly(sulfobetaine methacrylate) was successfully polymerized from these surfaces, and the polymerized sulfobetaine content, with corresponding antifouling properties, depended on both the macroinitiator additive concentration and polymerization time. Furthermore, the polymerization from the macroinitiator additive was successfully translated to functional electrospun scaffolds, showing the potential for this functionalization strategy in supramolecular material systems.

Combining Biologically Active β-Lactams Integrin Agonists with Poly(l-lactic acid) Nanofibers: Enhancement of Human Mesenchymal Stem Cell Adhesion

Regulating stem cell adhesion and growth onto functionalized biomaterial scaffolds is an important issue in the field of tissue engineering and regenerative medicine. In this study, new electrospun scaffolds of poly(l-lactic acid) (PLLA), as bioresorbable polymer, and β-lactam compounds agonists of selected integrins, as functional components with cell adhesive properties, are designed. The new β-lactam-PLLA scaffolds contribute significantly in guiding protein translation involved in human bone marrow mesenchymal stem cells (hBM-MSC) adhesion and integrin gene expression. Scanning electron microscopy, confocal laser scanning microscopy, and Western Blot analyses reveal that GM18-PLLA shows the best results, promoting cell adhesion by significantly driving changes in focal adhesion proteins distribution (β₁ integrin and vinculin) and activation (pFAK), with a notable increase of GM18-targets subunits integrin gene expression, α₄ and β₁. These novel functionalized submicrometric fibrous scaffolds demonstrate, for the first time, the powerful combination of selective β-lactams agonists of integrins with biomimetic scaffolds, suggesting a designed rule that could be suitably applied to tissue repair and regeneration.

Zwitterionic PMCP-Modified Polycaprolactone Surface for Tissue Engineering: Antifouling, Cell Adhesion Promotion, and Osteogenic Differentiation Properties

Biodegradable polycaprolactone (PCL) has been widely applied as a scaffold material in tissue engineering. However, the PCL surface is hydrophobic and adsorbs nonspecific proteins. Some traditional antifouling modifications using hydrophilic moieties have been successful but inhibit cell adhesion, which is not ideal for tissue engineering. The PCL surface is modified with bioinspired zwitterionic poly[2-(methacryloyloxy)ethyl choline phosphate] (PMCP) via surface-initiated atom transfer radical polymerization to improve cell adhesion through the unique interaction between choline phosphate (CP, on PMCP) and phosphate choline (PC, on cell membranes). The hydrophilicity of the PCL surface is significantly enhanced after surface modification. The PCL-PMCP surface reduces nonspecific protein adsorption (e.g., up to 91.7% for bovine serum albumin) due to the zwitterionic property of PMCP. The adhesion and proliferation of bone marrow mesenchymal stem cells on the modified surface is remarkably improved, and osteogenic differentiation signs are detected, even without adding any osteogenesis-inducing supplements. Moreover, the PCL-PMCP films are more stable at the early stage of degradation. Therefore, the PMCP-functionalized PCL surface promotes cell adhesion and osteogenic differentiation, with an antifouling background, and exhibits great potential in tissue engineering.

Cells may feel a hard substrate even on a grafted layer of soft hydrogel

Introducing or grafting molecules onto biomaterial surfaces to regulate cell destination via biophysical cues is one of the important steps for biomaterial design in tissue engineering. Understanding how cells feel the substrate makes it easier to learn the mechanism behind cell-material interaction. In this study, on a glass substrate, we constructed poly-phenoxyethyl methacrylate (PHEMA) brushes having different lengths via a surface-induced atom transfer radical polymerization (SI-ATRP) method. FTIR-ATR and XPS tests of the formed polymer brushes indicate that these brushes have characteristic chemical structures of PHEMA; the polymer brush length revealed by the AFM tests increases linearly with reaction time. Cell lines of BMSCs, ATDC5, and human chondrocytes (HC) were cultured on these substrates to evaluate proliferation, adhesion, and differentiation. Our results demonstrated that the cells cultured on the substrates with short PHEMA brushes developed a spread morphology and organized actin fibers as compared to the cells cultured on those with long brushes. Different cell lines showed different responses depending on the PHEMA brush length. Cells cultured on long PHEMA brushes displayed a more rounded shape, higher gene expression of FAK and integrin, and lower gene expression of NCAM and N-cadherin as compared to those, especially ATDC5 cells, cultured on short PHEMA brushes. On PHEMA brushes with a long length, the cell lines express higher cartilage-specific genes including Sox9 and Col2 and GAG in ECM. The results suggest that polymer brushes having different lengths may interfere with the behavior of the cells cultured on them.

Optimisation of grafting of low fouling polymers from three-dimensional scaffolds via surface-initiated Cu(0) mediated polymerisation

Well-controlled low fouling polymers brushes were grafted from the surface of biodegradable electrospun fibres for advanced tissue engineering applications.

A self-defensive bilayer hydrogel coating with bacteria triggered switching from cell adhesion to antibacterial adhesion

(1) A self-defensive bacterial infection responsive bilayer hydrogel coating was designed; (2) the bilayer coating could promote cell adhesion and proliferation; and (3) the surface showed bacterial infection sensitive switching from a cell adhesion surface to an antibacterial adhesion surface by detaching the upper layer.