Directing hMSCs fate through geometrical cues and mimetics peptides

The native microenvironment of mesenchymal stem cells (hMSCs)—the extracellular matrix (ECM), is a complex and heterogenous environment structured at different scales. The present study aims at mimicking the hierarchical microorganization of proteins or growth factors within the ECM using the photolithography technique. Polyethylene terephthalate substrates were used as a model material to geometrically defined regions of RGD + BMP‐2 or RDG + OGP mimetic peptides. These ECM‐derived ligands are under research for regulation of mesenchymal stem cells osteogenic differentiation in a synergic manner. The hMSCs osteogenic differentiation was significantly affected by the spatial distribution of dually grafted peptides on surfaces, and hMSCs cells reacted differently according to the shape and size of peptide micropatterns. Our study demonstrates the presence of a strong interplay between peptide geometric cues and stem cell differentiation toward the osteoblastic lineage. These tethered surfaces provide valuable tools to investigate stem cell fate mechanisms regulated by multiple ECM cues, thereby contributing to the design of new biomaterials and improving hMSCs differentiation cues

ATR-FTIR spectrum of E.coli A) and D.proteolyticus B) before and after treatment with BA.

<p>ATR-FTIR spectrum of E.coli A) and D.proteolyticus B) before and after treatment with BA.</p

Retention experiment at A) OxPPy-PBA and B) OxPPy-ClO₄ film electrodes.

<p>Both films prepared using 1 mM of the dopant. All films were prepared from an acetonitrile water solution (1:4) containing 75 mM of Py and 1 mM of the dopant (PBA or ClO₄^-).</p

The effects of BA treatment on bacterial adhesion to the functionalised surfaces.

<p><i>D</i>.<i>proteolyticus</i> and <i>E</i>.<i>coli</i> were pre-treated with BA (100 mgr/ml, 5min), collected by centrifugation, re-suspended in PBS and then exposed to the polymer surfaces. Untreated bacterial cells under the same conditions (7.5 ml of 5 × 10⁷ cfu/ml, 30 min) were used as a control test. The numbers of bacteria were determined by fluorescent dye staining and imaging. Error bars indicate standard deviations. All films were prepared from an acetonitrile water solution (1:4) containing 75 mM of Py and 1 mM of the dopant (PBA or DBS).</p

Physicochemical properties of polypyrrole-doped polymer.

<p>All films were prepared from an acetonitrile water solution (1:4) containing 75 mM of Py and 1 mM of the dopant (PBA or DBS).</p

SEM images of different PPy films: A) PPy film on carbon electrode using PBA 1 mM as dopant; B) OxPPy film on carbon electrode using PBA 1 mM as dopant; C) PPy film on Au using PBA 1 mM as dopant; D) PPy film on Au using DBS 1 mM as dopant.

<p>All films were prepared from an acetonitrile water solution (1:4) containing 75 mM of Py and 1 mM of the dopant (PBA or DBS or ClO₄^-).</p

The effects of different doping of PPy on bacterial adhesion to the surface.

<p>DBS and PBA doped PPy films were exposed by different bacterial suspension (7.5 ml of 5 × 10⁷ cfu/ml, 30 min). The numbers of bacteria were determined by fluorescent dye staining and imaging. Error bars indicate standard deviations. All films were prepared from an acetonitrile water solution (1:4) containing 75 mM of Py and 1 mM of the dopant (PBA or DBS).</p

Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine.

Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties