Locomotion Guidance by Extracellular Matrix Is Adaptive and Can be Restored by a Transient Change in Ca2+ Level

Navigation of cell locomotion by gradients of soluble factors can be desensitized if the concentration of the chemo-attractant stays unchanged. It remains obscure if the guidance by immobilized extracellular matrix (ECM) as the substrate is also adaptive and if so, how can the desensitized ECM guidance be resensitized. When first interacting with a substrate containing micron-scale fibronectin (FBN) trails, highly motile fish keratocytes selectively adhere and migrate along the FBN paths. However, such guided motion become adaptive after about 10 min and the cells start to migrate out of the ECM trails. We found that a burst increase of intracellular calcium created by an uncaging technique immediately halts the undirected migration by disrupting the ECM-cytoskeleton coupling, as evidenced by the appearance of retrograde F-actin flow. When the motility later resumes, the activated integrin receptors render the cell selectively binding to the FBN path and reinitiates signaling events, including tyrosine phosphorylation of paxillin, that couple retrograde F-actin flow to the substrate. Thus, the calcium-resensitized cell can undergo a period of ECM-navigated movement, which later becomes desensitized. Our results also suggest that endogenous calcium transients as occur during spontaneous calcium oscillations may exert a cycling resensitization-desensitization control over cell's sensing of substrate guiding cues

In vitro and in vivo studies on biocompatibility of carbon fibres

In the present study we focused on the in vitro and in vivo evaluation of two types of carbon fibres (CFs): hydroxyapatite modified carbon fibres and porous carbon fibres. Porous CFs used as scaffold for tissues regeneration could simultaneously serve as a support for drug delivery or biologically active agents which would stimulate the tissue growth; while addition of nanohydroxyapatite to CFs precursor can modify their biological properties (such as bioactivity) without subsequent surface modifications, making the process cost and time effective. Presented results indicated that fibre modification with HAp promoted formation of apatite on the fibre surface during incubation in simulated body fluid. The materials biocompatibility was determined by culturing human osteoblast-like cells of the line MG 63 in contact with both types of CFs. Both tested materials gave good support to adhesion and growth of bone-derived cells. Materials were implanted into the skeletal rat muscle and a comparative analysis of tissue reaction to the presence of the two types of CFs was done. Activities of marker metabolic enzymes: cytochrome c oxidase (CCO) and acid phosphatase were examined to estimate the effect of implants on the metabolic state of surrounding tissues. Presented results evidence the biocompatibility of porous CFs and activity that stimulates the growth of connective tissues. In case of CFs modified with hydroxyapatite the time of inflammatory reaction was shorter than in case of traditional CFs

Interaction between acrylic substrates and RAD16-I peptide in its self-assembling

[EN] Self-assembling peptides (SAP) are widely used as scaffolds themselves, and recently as fillers of microporous scaffolds, where the former provides a cell-friendly nanoenvironment and the latter improves its mechanical properties. The characterization of the interaction between these short peptides and the scaffold material is crucial to assess the potential of such a combined system. In this work, the interaction between poly(ethyl acrylate) (PEA) and 90/10 ethyl acrylate-acrylic acid copolymer P(EAcoAAc) with the SAP RAD16-I has been followed using a bidimensional simplified model. By means of the techniques of choice (congo red staining, atomic force microscopy (AFM), and contact angle measurements) the interaction and self-assembly of the peptide has proven to be very sensitive to the wettability and electro-negativity of the polymeric substrate.The authors acknowledge funding through the European Commission FP7 project RECATABI (NMP3-SL-2009-229239), and from the Spanish Ministerio de Ciencia e Innovacion through projects MAT2011-28791-C03-02 and -03. This work was also supported by the Spanish Ministerio de Educacion through M. Arnal-Pastor FPU 2009-1870 grant. The authors acknowledge the assistance and advice of Electron Microscopy Service of the UPV.Arnal Pastor, MP.; González-Mora, D.; García-Torres, F.; Monleón Pradas, M.; Vallés Lluch, A. (2016). Interaction between acrylic substrates and RAD16-I peptide in its self-assembling. 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Mono-functional aminosilanes as primers for peptide functionalization.

When covalently attaching biomolecules to surfaces such as titanium, trifunctional silanes are commonly used as primers to produce surface amine groups. However, these primed surfaces are rarely uniform in structure due to networking of the silane. Mono-functional aminosilanes may result in more uniform structures, although their long-term stability and effect on osteoblast cell responses are possible issues for orthopedic applications. This study examines for the first time the optimization of peptide coupling to titanium using mono-functional aminosilane reaction chemistry. The resultant surface topography, chemistry, and thicknesses were characterized showing improved surface uniformity compared with trifunctional silanized surfaces. The stability of the coatings was examined over a period of 8 days in environments of varying pH, temperature, and humidity. In addition, human osteosarcoma (HOS) cell adhesion and spreading on the samples was examined; adhesion was minimal on silanized surfaces, but after functionalization with cysteine the cell density was greater than the titanium control and showed no overall detrimental effect on initial cell responses

Organic modification of titania sol-gels and surfaces

Titanium and its alloys are commonly used biomaterials for bone contacting applications, the self-passivating titanium oxide surface producing a favourable non-specific response. The surface of a biomaterial is the first point of contact when implanted and hence is an crucial factor in determining the overall bodily response. By altering surface chemistry it is possible to control cell behaviour and promote desired cell responses [1]. In this study a process to attach peptides to titania is investigated with the aim to improve cell adhesion. The reaction with both titania surfaces and nano-particulate (5 nm) titania sols were investigated. Titania surfaces with a variety of hydroxyl group concentrations were reacted with 3%v/v aminosilane through an anhydrous route. FTIR and XPS results indicate successful attachment of aminosilane on all surfaces. Titania sols were reacted with aminosilane in their aqueous solution and subsequently cysteine attached using a cross-linker (sulfo-SMCC). The functionalised particles were analyzed using FTIR, results indicate successful attachment of silane and cross-linking of cysteine, illustrating that this method can be used to produce peptide functionalised nano-particulate titani