Conformational analysis of heparin binding peptides

Enhancement of peri-implant bone osteogenic activity induced by a peptidomimetic functionalization of titanium

Osteoblast cell adhesion to the extracellular matrix is established through two main pathways: one is mediated by the binding between integrin and a minimal adhesion sequence (RGD) on the extracellular protein, the other is based on the interactions between transmembrane proteoglycans and heparin-binding sequences found in many matrix proteins. The aim of this study is the evaluation in an in vivo endosseous implant model of the early osteogenic response of the peri-implant bone to a biomimetic titanium surface functionalized with the retro-inverso 2DHVP peptide, an analogue of Vitronectin heparin binding site. The experimental plan is based on a bilateral study design of Control and 2DHVP implants inserted respectively in the right and left femur distal metaphysis of adult male Wistar rats (n=16) weighing about 300grams and evaluated after 15days. Fluorochromic bone vital markers were given in a specific time frame, in order to monitor the dynamic of new bone deposition. The effect inducted by the peptidomimetic coating on the surrounding bone were qualitatively and quantitatively evaluated by means of static and dynamic histomorphometric analyses performed within three concentric and subsequent circular Regions of Interest (ROI) of equivalent thickness (220μm), ROI1 adjacent to the interface, ROI2, the middle, and ROI3 the farthest. The data indicated that these functionalized implants stimulated a higher bone apposition rate (p<0,01) and larger and rapid osteoblast activation in terms of mineralizing surface within ROI1 compared to the control (p<0,01). These higher osteoblast recruitment and activation leads to a greater bone-to-implant contact reached for DHVP samples (p<0,5). This represents an initial stimulus of the osteogenic activity that might results in a faster and better osteointegration process.

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides

Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion, growth, proliferation and differentiation. Recently, covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide (HVP) mapped on [351-359] sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays, and to promote osseointegration in in vivo studies. For the first time to our knowledge, in this study we investigated the resistance of adhesion sequences to proteolytic digestion: HVP was completely cleaved after 5 h. In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence. A retro-inverted peptide D-2HVP, composed of D amino acids, was completely stable in serum-containing medium. In addition, glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium. Interestingly, D-2HVP increased expression of IBSP, VTN and SPP1 genes as compared to HVP functionalized surfaces. Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces. Therefore, the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

Clinical outcomes for teeth treated with electrospun poly(ε-caprolactone) fiber meshes/mineral trioxide aggregate direct pulp capping

INTRODUCTION

Mineral trioxide aggregate (MTA) is a biocompatible material for direct pulp capping. This study was designed to compare the clinical outcomes of pulp-exposed teeth treated with either poly(ε-caprolactone) fiber mesh (PCL-FM) as a barrier for MTA (so-called PCL-FM/MTA) or MTA direct pulp capping.

METHODS

Sixty human vital teeth were evenly divided into 4 groups (n = 15 in each group). Teeth in groups 1 and 3 had pulp exposure <1 mm in diameter, whereas teeth in groups 2 and 4 had pulp exposure of 1-1.5 mm in diameter. Teeth in groups 1 and 2 were treated with PCL-FM/MTA direct pulp capping, and those in groups 3 and 4 were treated with MTA direct pulp capping.

RESULTS

Teeth treated with PCL-FM/MTA direct pulp capping needed a significantly shorter mean duration for dentin bridge formation than teeth treated with MTA direct pulp capping. Moreover, teeth with pulp exposure <1.0 mm in diameter needed a significantly shorter mean duration for dentin bridge formation than teeth with pulp exposure of 1-1.5 mm in diameter after either PCL-FM/MTA or MTA direct pulp capping treatment. In addition, teeth treated with PCL-FM/MTA direct pulp capping formed an approximately 3-fold thicker dentin bridge than teeth treated with MTA direct pulp capping 8 weeks or 3 months later. Furthermore, none of the teeth treated with PCL-FM/MTA direct pulp capping showed tooth discoloration after treatment for 3 months.

CONCLUSIONS

PCL-FM/MTA is a better combination material than MTA alone for direct pulp capping of human permanent teeth.

Strategies to manage permanent non-vital teeth with open apices: a clinical update

If dental pulp injury occurs prior to complete root formation and apical closure, normal root development is halted. This condition produces several complications. Firstly, the apical diameter of the canal is often larger than the coronal diameter, so debridement is difficult. Secondly, the lack of an apical stop makes the obturation in all dimensions virtually impossible. And finally, the thin walls of the root canal are prone to fracture, so that surgical treatment is generally not a viable option. There are a number protocols to manage non-vital open-apex teeth such as apexification, apical barrier technique (one-visit apexification), orthograde root filling using MTA, triple antibiotic paste, and tissue engineering concept. The aim of this paper is to review these treatment protocols.

Evaluation of Endothelial Cell Adhesion onto Different Protein/Gold Electrodes by EIS

To study cell attachment to biomaterials, several proteins such as fibronectin, collagen IV, heparin, immunoglobulin G, and albumin have been deposited onto polystyrene adsorbed on a self-assembled monolayer (silane or thiol) on glass or gold, respectively. The different steps of this multilayer assembly have been characterized by electrochemical impedance spectroscopy (EIS). These data are compared to those of adhesion rate, viability percentage, and cytoskeleton labeling for a better understanding of the cell adhesion process to each protein. All the proteins are endothelial cell adhering biomolecules but not with the same features. A linear relationship has been established between adhesion rate and resistance of the endothelial cell/protein interface for all negatively charged proteins.

Integral equation theory for hard spheres confined on a cylindrical surface: anisotropic packing entropically driven

The structure of two-dimensional (2D) hard-sphere fluids on a cylindrical surface is investigated by means of the Ornstein-Zernike integral equation with the Percus-Yevick and the hypernetted-chain approximation. The 2D cylindrical coordinate breaks the spherical symmetry. Hence, the pair-correlation function is reformulated as a two-variable function to account for the packing along and around the cylinder. Detailed pair-correlation function calculations based on the two integral equation theories are compared with Monte Carlo simulations. In general, the Percus-Yevick theory is more accurate than the hypernetted-chain theory, but exceptions are observed for smaller cylinders. Moreover, analysis of the angular-dependent contact values shows that particles are preferentially packed anisotropically. The origin of such an anisotropic packing is driven by the entropic effect because the energy of all the possible system configurations of a dense hard-sphere fluid is the same. In addition, the anisotropic packing observed in our model studies serves as a basis for linking the close packing with the morphology of an ordered structure for particles adsorbed onto a cylindrical nanotube.

Effect of synthetic peptides on osteoblast adhesion

The quality of the early cell/material interactions is responsible for the long-term functional properties of any implanted device. Accordingly, "next generation" dental/orthopedic biomaterials should be able to promote osteoblast adhesion thus improving the integration process between surgically placed implants and biological tissues. Recent studies have identified a wide range of biochemical signals that can be exploited to promote adhesion, migration, proliferation and differentiation of cells. The clinical use of natural factors to promote osteoblast adhesion is complicated because those are often insoluble and unstable macromolecules and, in addition, it is difficult to obtain them in high quantities, with good purity grade and at low cost. A valid alternative could be the use of short peptides carrying the minimum active sequence of the natural macromolecular factor. This paper describes the properties of two classes of peptides, promoting different adhesion mechanisms, to enhance rat bone marrow osteoblast adhesion both to polystyrene and to acellular bone matrix.