Roberta Danesin

Electrospun scaffolds of self-assembling peptides with poly(ethylene oxide) for bone tissue engineering

Structural, mechanical and biochemical properties have to be considered when searching for suitable extracellular matrix substitutes. Fibrous structures of synthetic or natural polymers have received increasing interest as three-dimensional scaffolds for tissue engineering applications as they can be easily produced by electrospinning with different topographical features by changing the process parameters. On the other hand, the nanobiotechnology approach suggests mimicking molecular architectures in nature through self-assembly. In particular, self-assembling peptide-based biomaterials have been successfully used as scaffolds for cell growth. In order to amalgamate these two strategies nanofibrous electrospun scaffolds of hybrid polymer were designed and obtained by mixing poly(ethylene oxide) and self-assembling peptides in aqueous solution. The results of in vitro osteoblast adhesion and proliferation assays on the electrospun scaffolds obtained using different self-assembling peptide sequences are discussed.

Self-assembling peptide-enriched electrospun polycaprolactone scaffolds promote the h-osteoblast adhesion and modulate differentiation-associated gene expression

Electrospun polycaprolactone (PCL) is able to support the adhesion and growth of h-osteoblasts and to delay their degradation rate to a greater extent with respect to other polyesters. The drawbacks linked to its employment in regenerative medicine arise from its hydrophobic nature and the lack of biochemical signals linked to it. This work reports on the attempt to add five different self-assembling (SA) peptides to PCL solutions before electrospinning. The hybrid scaffolds obtained had regular fibers (SEM analysis) whose diameters were similar to those of the extracellular matrix, more stable hydrophilic (contact angle measurement) surfaces, and an amorphous phase constrained by peptides (DSC analysis). They appeared to have a notable capacity to promote the h-osteoblast adhesion and differentiation process by increasing the gene expression of alkaline phosphatase, bone sialoprotein, and osteopontin. Adding an Arg-Gly-Asp (RGD) motif to a self-assembling sequence was found to enhance cell adhesion, while the same motif condensed with a scrambled sequence did not, indicating that there is a cooperative effect between RGD and 3D architecture created by the self-assembling peptides. The study demonstrates that self-assembling peptide scaffolds are still able to promote beneficial effects on h-osteoblasts even after they have been included in electrospun polycaprolactone. The possibility of linking biochemical messages to self-assembling peptides could lead the way to a 3D decoration of fibrous scaffolds.

Chemoselective Surface Immobilization of Proteins through a Cleavable Peptide

Surface immobilization of biomolecules is a fundamental step in several experimental techniques such as surface plasmon resonance analysis and microarrays. Oxime ligation allows reaching chemoselective protein immobilization with the retention of native-like conformation by proteins. Beside the need for chemoselective ligation of molecules to surface/particle, equally important is the controlled release of the immobilized molecules, even after a specific binding event. For this purpose, we have designed and assessed in an SPR experiment a peptide linker able to (i) anchor a given protein (enzymes, receptors, or antibodies) to a surface in a precise orientation and (ii) release the immobilized protein after selective enzymatic cleavage. These results open up the possibility to anchor to a surface a protein probe leaving bioactive sites free for interaction with substrates, ligands, antigens, or drugs and successively remove the probe-ligand complex by enzymatic cleavage. This peptide linker can be considered both an improvement of SPR analysis for macromolecular interaction and a novel strategy for drug delivery and biomaterial developments.

Osteogenic properties of a short BMP-2 chimera peptide.

Bone morphogenetic proteins (BMPs) play a key role in bone and cartilage formation. For these properties, BMPs are employed in the field of tissue engineering to induce bone regeneration in damaged tissues. To overcome drawbacks due to the use of entire proteins, synthetic peptides derived from their parent BMPs have come out as promising molecules for biomaterial design.

Wet-priming extracorporeal membrane oxygenation device maintains sterility for up to 35 days of follow-up.

In emergency cases, rapid extracorporeal membrane oxygenation (ECMO) device initialization is able to drastically reduce the incidence of patient morbidity and/or mortality. Pre-assembled and ready-to-use ECMO circuits might save up to 30-60 critical minutes in patient management. Six ECMO circuits (Oxygenator D905 EOS with REVOLUTION™ pump and Sorin PTS) were assembled in the operating room in standard conditions and then placed at 37°C for 35 days in order to evaluate possible contamination and ingrowth of micro-organisms. Every 7 days after ECMO circuit assembly and wet-priming, samples of priming fluid were analyzed to verify the presence/absence of possible common contaminants (Enterobacteriaceae, Staphylococcus aureus and fungi). Moreover, two supplementary circuits, used as positive controls, were deliberately inoculated with a known concentration of a Escherichia coli strain and prime samplings carried out at different time-points to determine bacterial growth rate. Sterility was maintained in the ECMO circuits for up to 35 days.

Facile and selective covalent grafting of an RGD-peptide to electrospun scaffolds improves HUVEC adhesion

The development of a biomimetic surface able to promote endothelialization is fundamental in the search for blood vessel substitutes that prevent the formation of thrombi or hyperplasia. This study aims at investigating the effect of functionalization of poly‐ε‐caprolactone or poly(L‐lactic acid‐co‐ɛ‐caprolactone) electrospun scaffolds with a photoreactive adhesive peptide. The designed peptide sequence contains four Gly‐Arg‐Gly‐Asp‐Ser‐Pro motifs per chain and a p‐azido‐Phe residue at each terminus. Different peptide densities on the scaffold surface were obtained by simply modifying the peptide concentration used in pretreatment of the scaffold before UV irradiation.

Study of the structure and the molecular mobility of a new biological matrix (collagen/peptides)

The thermal analyses have showed a slight decreasing of the denaturation temperature for all the treated collagens. These results suggest a slight destabilization of treatments on the collagen triple helix. The dielectric results highlight the probable crosslinking effect of irradiation between the collagen and the peptides with a chain dynamics similar to the pure collagen one. Indeed, it is known that irradiation can cause a crosslink effect. These preliminary analyses are quite promising for the conception of a new type of biological matrix. In order to optimize the properties of this new material, analyses will be made with less harmful ultraviolet irradiation.