Development of a PCL-silica nanoparticles composite membrane for Guided Bone Regeneration.

The pivotal step in Guided Bone Regeneration (GBR) therapy is the insertion of a membrane for support and barrier functions. Here, we studied the effect of the addition of silica nanoparticles (Si-NPs) in electrospun poly(ε-caprolactone) (PCL) membranes to improve the mechanical and osteoconductive properties of the membranes. To this end, Si-NPs were firstly synthesized and then suspended in PCL solutions containing a polar solvent (2,2,2-trifluroethanol) and water with the addition of an anionic surfactant. Nanocomposite membranes were fabricated from the solutions through an electrospinning technique. Morphology, structure and chemical composition, and tensile properties of the membranes were analyzed. Membrane stability was determined by visual examination of the membranes after immersion in phosphate buffered saline. The effect of the materials on osteoblastic differentiation was evaluated by in vitro culture of the membranes with MC3T3-E1 osteoblastic cells. The results indicated that Si-NPs were successfully incorporated in the interior of the PCL electrospun fibers during the electrospinning process. Tensile modulus was significantly increased for composition S50 and tensile strength significantly increased for compositions S25 and S50. Membranes containing Si-NPs have shown to be cytocompatible. The results obtained demonstrate that the Si-NPs were homogeneously incorporated in the electrospun fibers, resulting in an improvement of the tensile properties of the prepared materials.

Incorporation of simvastatin in PLLA membranes for guided bone regeneration: effect of thermal treatment on simvastatin release.

Electrospun membranes based on biodegradable polymers are promising materials to be used for guided bone regeneration (GBR) therapy. The incorporation of osteostimulatory compounds can improve the biofunctionality of those membranes, making them active players in bone regeneration. Simvastatin has been shown to promote osteogenic differentiation both in vitro and in vivo. However, in most of these systems, the drug was quickly released, not matching the pace of bone regeneration. The aim of this study was to develop poly(l-lactic acid) (PLLA) membranes containing simvastatin (SV) that have a prolonged drug release rate, compatible with GBR applications. To this end, SV was mixed with PLLA and electrospun. The membranes were subjected to a thermal treatment in order to increase the crystallinity of PLLA. Morphological, structural and chemical properties of the electrospun membranes were characterized. The effect of the thermal treatment on the release profile of SV was evaluated by near physiological release experiments at 37 °C. The osteostimulatory potential was determined by in vitro culture of the membranes with rat bone marrow stromal cells (rBMSCs). The results confirmed that the thermal treatment led to an increase in polymer crystallinity and a more sustained release of SV. In vitro assays demonstrate cellular proliferation over time for all the membranes and a significant increase in osteogenic differentiation for the membranes containing SV subjected to thermal treatment.

Incorporation of PLLA micro-fillers for mechanical reinforcement of calcium-phosphate cement.

Calcium phosphate cements (CPCs) are biocompatible, resorbable, injectable and osteoconductive. Those properties render such materials suitable for applications where bone repair and regeneration is required However, their brittle nature limits their application only to non-load-bearing applications. The incorporation of long polymeric fibers can improve the mechanical properties of CPCs, but aggregation is a major problem. Instead, short polymeric fillers can be easily dispersed in the cement matrix, but their reinforcing effect has not been studied yet. In this study, continuous poly-L-lactic acid fibers (PLLA) with a smooth or porous surface morphology were prepared by electrospinning. PLLA micro-fillers were developed, by means of an aminolysis process, and added to α-TCP or α-TCP/PLGA-based cements. Micro-filler distribution as well as the morphology, cohesiveness, setting times and mechanical properties were evaluated. PLLA micro-fillers were homogeneously dispersed throughout the cement while the handling properties were not significantly affected. A decrease in the initial setting times was observed when PLLA was added, while the mechanical properties were comparable to those of the α-TPC or α-TCP/PLGA compositions.

Top-Down Approach for the Preparation of Highly Porous PLLA Microcylinders.

A wide range of particles have been developed for different applications in drug-delivery, tissue engineering, or regenerative medicine. In contrast to traditional spherical particles, nonspherical (e.g., cylindrical) particles possess several structural and morphological advantages that make them attractive for specific applications. Here, we developed a top-down approach to process electrospun fibers into microsized cylinders (i.e., microcylinders) with high specific surface area and with or without surface porosity. To obtain these microcylinders, poly(l-lactic acid) (PLLA) solutions were subjected to electrospinning, followed by an aminolysis-based chemical scission procedure. The morphology, structure, and chemical composition of the microcylinders were then characterized. The specific surface area and surface porosity of the microcylinders were controlled by the volatility of the solvents, and their length was dependent on the duration of the aminolysis reaction. During aminolysis, the microcylinders became functionalized with amine groups, enabling potential further modifications by grafting with compounds containing desired chemical groups, for example, carboxyl, carbonyl, or hydroxyl functional groups. Additionally, the microcylinders showed in vitro biocompatible properties related to cell viability. These data demonstrate that PLLA microcylinders with high specific surface area, optional surface porosity, amine-based functional handles granting additional functionalization, and cytocompatible properties are candidate materials for future biomedical applications.

Synthesis and electrochemical study of a hybrid structure based on PDMS-TEOS and titania nanotubes for biomedical applications.

Metallic implants and devices are widely used in the orthopedic and orthodontic clinical areas. However, several problems regarding their adhesion with the living tissues and inflammatory responses due to the release of metallic ions to the medium have been reported. The modification of the metallic surfaces and the use of biocompatible protective coatings are two approaches to solve such issues. In this study, in order to improve the adhesion properties and to increase the corrosion resistance of metallic Ti substrates we have obtained a hybrid structure based on TiO2 nanotubular arrays and PDMS-TEOS films. TiO2 nanotubes have been prepared with two different diameters by means of electrochemical anodization. PDMS-TEOS films have been prepared by the sol-gel method. The morphological and the elemental analysis of the structures have been investigated by scanning electron microscopy and energy dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS) and polarization curves have been performed during immersion of the samples in Kokubo's simulated body fluid (SBF) at 37 °C to study the effect of structure layers and tube diameter on the protective properties. The obtained results show that the modification of the surface structure of TiO2 and the application of PDMS-TEOS film is a promising strategy for the development of implant materials.