Smooth-rough asymmetric PLGA structure made of dip coating membrane and electrospun nanofibrous scaffolds meant to be used for guided tissue regeneration of periodontium

A surgical procedure for the repair of damaged periodontal tissue is Guided Tissue Regeneration (GTR), which involves the use of a barrier membrane to prevent soft tissue ingrowth and create a space for slow regeneration of periodontium and bone. GTR membrane should have pores able to facilitate the diffusion of fluids, oxygen, nutrients, and bioactive substances for cell growth, but also be impermeable to epithelial cells or gingival fibroblasts, which could overpopulate the defect space and inhibit infiltration and activity of bone-forming cells. In this paper, a bilayer PLGA membrane was realized by coupling the dip coating and electrospinning techniques. The rough layer of the double-sided structure was electrospun on the previously prepared smooth dip-coated membrane. A rotating drum collector at two rotating speeds was used to generate different fibers orientation. The bilayer membrane with different superimposed surfaces was successfully fabricated and characterized from a morphological, physicochemical, and the mechanical point of view. Performed analyses revealed that the membrane possesses suitable properties, especially from mechanical point of view, for its possible use as a scaffold for the GTR of periodontum. A high fiber alignment and improved mechanical properties with respect to available GTR membranes characterized the product resulting from this study

3D collagen cultures under well-defined dynamic strain: A novel strain device with a porous elastomeric support

The field of mechanobiology has grown tremendously in the past few decades, and it is now well accepted that dynamic stresses and strains can impact cell and tissue organization, cell-cell and cell-matrix communication, matrix remodeling, cell proliferation and apoptosis, cell migration, and many other cell behaviors in both physiological and pathophysiological situations. Natural reconstituted matrices like collagen and fibrin are often used for three-dimensional (3D) mechanobiology studies because they naturally form fibrous architectures and are rich in cell adhesion sites; however, they are physically weak and typically contain >99% water, making it difficult to apply dynamic stresses to them in a truly 3D context. Here we present a composite matrix and strain device that can support natural matrices within a macroporous elastic structure of polyurethane. We characterize this system both in terms of its mechanical behavior and its ability to support the growth and in vivo-like behaviors of primary human lung fibroblasts cultured in collagen. The porous polyurethane was created with highly interconnected pores in the hundreds of mm size scale, so that while it did not affect cell behavior in the collagen gel within the pores, it could control the overall elastic behavior of the entire tissue culture system. In this way, a well-defined dynamic strain could be imposed on the 3D collagen and cells within the collagen for several days (with elastic recoil driven by the polyurethane) without the typical matrix contraction by fibroblasts when cultured in 3D collagen gels. We show lung fibroblast-to-myofibroblast differentiation under 30%, 0.1 Hz dynamic strain to validate the model and demonstrate its usefulness for a wide range of tissue engineering applications. © 2008 Wiley Periodicals, Inc

Chitosan-hydroxyapatite composites made from sustainable sources: a morphology and antibacterial study

Chitosan (Cs) and hydroxyapatite (HA) 3D scaffolds/composites were prepared with a sustainable process, as HA was obtained using CaCO3 derived from cork, a natural material used as a template agent. The HA@Cs composites were prepared with HA in situ formation in a Cs solution, with a dissolution-precipitation mechanism. Different reaction times were considered, with time of 72 h leading to the best materials (sample CsHA_72). X-ray Diffraction (XRD) analysis confirmed HA formation. The analysis of Cs unit cell parameters showed that, for the unmodified Cs, the cell had larger dimensions and a higher degree of distortion than previously reported in literature; HA incorporation in the CsHA_72 composite led to a further increase in the cell dimensions. The morphology of the scaffolds was studied with Scanning Electron Microscopy (SEM) and a high level of porosity was observed; a statistical comparison was performed between the unmodified Cs and CsHA_72 to determine the pore size, structure, and distribution. This analysis, the first of this kind for this type of composites, showed smaller and more circular pores for the CsHA_72 composite (average diameter of 70 μm vs. 88 μm for unmodified Cs). The overall level of porosity, however, did not change (>77%); likewise, the Young modulus was not affected by HA incorporation (about 11 kPa). Antibacterial tests, performed on Escherichia coli and Staphylococcus aureus, showed that HA presence did not significantly reduce the antimicrobial properties; the composites were particularly effective towards S. aureus, as a >90% the bacterial population reduction was observed for an incubation time of 2 h. HA@Cs also showed excellent biocompatibility and good cell proliferation. The properties of these 3D scaffolds make them suitable for application as biomaterials.info:eu-repo/semantics/publishedVersio

Evaluation of in vivo response of three biphasic scaffolds for osteochondral tissue regeneration in a sheep model

Osteochondral defects are a common problem in both human medicine and veterinary practice although with important limits concerning the cartilaginous tissue regeneration. Interest in the subchondral bone has grown, as it is now considered a key element in the osteochondral defect healing. The aim of this work was to generate and to evaluate the architecture of three cell-free scaffolds made of collagen, magnesium/hydroxyapatite and collagen hydroxyapatite/wollastonite to be implanted in a sheep animal model. Scaffolds were designed in a bilayer configuration and a novel "Honey" configuration, where columns of hydroxyapatite were inserted within the collagen matrix. The use of different types of scaffolds allowed us to identify the best scaffold in terms of integration and tissue regeneration. The animals included were divided into four groups: three were treated using different types of scaffold while one was left untreated and represented the control group. Evaluations were made at 3 months through CT analysis. The novel "Honey" configuration of the scaffold with hydroxyapatite seems to allow for a better reparative process, although we are still far from obtaining a complete restoration of the defect at this time point of follow-up

A tissue engineered osteochondral composite for cartilage repair: an in vivo study

This work aimed to validate the efficacy of a tissue engineered osteochondral composite for the treatment of cartilage lesion produced in adult pigs. The osteochondral composite was manufactured by combining an osteo-compatible cylinder and a neocartilagineous tissue obtained by seeding swine articular chondrocytes into a collagen scaffold. Articular cartilage was harvested from the trochlea of six adult pigs and was enzymatically digested to isolate the chondrocytes [Deponti D.et al. 2005]. The cells were then expanded in monolayer culture in chondrogenic medium and seeded onto a collagen scaffold. The collagen scaffold was preintegrated in vitro, macroscopically and microscopically, to a an osteo-compatible cylinder. The seeded osteochondral scaffolds were left in standard culture condition for 3 weeks with the addition of growth factors. At the end of culture time the osteochondral scaffolds were surgically implanted in osteochondral lesion performed in the trochlea of the same pigs from which the cartilage was initially harvested. As control, some osteochondral lesions were treated with acellular scaffolds and others were left untreated. After 3 months, the repair tissue of the three experimental groups was macroscopically analyzed and processed for histological and biochemical analysis. The hystologic ICRS II scale showed a statistically significant difference between the three experimental groups only in the parameters regarding the cell morphology and the surface/superficial assessment: the lesion treated with the unseeded osteochondral scaffolds showed higher values in chondrocytes morphology and in the superficial layer recovery, with respect to the lesions treated with the seeded scaffolds or left untreated. The biochemical analysis showed a higher DNA content in the lesion repaired with cellular scaffold and a higher GAGs/DNA ratio in the lesions with a spontaneous repair. The result of this study demonstrate that an osteochondral scaffold was able to repair an osteochondral lesion in an in vivo model of adult pigs, showing a good integration with the surrounding tissue. The quality of the repair was higher when the scaffold was not seeded with chondrocytes, but filled with cells migrated from subchondral bone. This tissue engineered osteochondral composite could represent a valuable model for further in vivo studies on the repair of chondral/osteochondral lesion

Mechanical, pH and Thermal Stability of Mesoporous Hydroxyapatite

The stability of mesoporous hydroxyapatite (HAP) powder was studied following treatments of ultrasound, pH and heating. HAP was found to be mechanically stable up to (and including) 1 h continuous ultrasonic treatment in water. The HAP structure was also stable to pH, evidenced by practically identical XRD and FTIR spectra over the pH range 2–12. The surface area increased progressively with increasing acidity, reaching a maximum of 121.9 m 2 g −1 at pH 2, while alkaline conditions decreased the surface area to a minimum of 55.4 m 2 g −1 at pH 12. Heating in air had a significant influence on the structural and morphological properties of HAP, which underwent dehydroxylation to form oxyhydroxyapatite (OHAP) at temperatures ≥ 650 °C, and β-tricalcium phosphate (β-TCP) ≥750 °C. The surface area decreased at elevated temperatures due to agglomeration of HAP crystals by sintering, which was associated with an increased particle size