In vitro bioactivity and degradation of polycaprolactone composites containing silicate fillers

Fabrication and Characterization of a Bioscaffold Using Hydroxyapatite and Unsaturated Polyester Resin

Outstanding biodegradability and biocompatibility are attributes associated with particular polyester substances that make this group useful in specific biomedical fields. To assess the potential as a biomaterial, a novel composite consisting of hydroxyapatite (HAp) and unsaturated polyester resin (UPR) was developed in this work. Using a hand-lay-up technique, various percentages (50, 40, 30, 20, and 10%) of HAp were reinforced into the UPR matrix to fabricate composite materials out of glass sheets. Prior to processing of the composite samples, hydroxyapatite was chemically synthesized in a wet chemical manner. Using a universal testing machine (UTM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA), the fabricated samples were characterized. The crystallographic parameters of synthesized hydroxyapatite (HAp) were also estimated through a range of formulas. The optimal amount for hydroxyapatite was 40% according to the findings of the tensile strength (TS), tensile modulus (TM), percentage of elongation at break (EB), bending strength (BS), and bending modulus (BM). Improvements in TS, TM, BS, and BM for the ideal combination were 39.39, 9.21, 912.05, and 259.96%, in each case, over the controlled one. Thermogravimetric analysis (TGA) has been implemented to determine the degradation temperature of the fabricated composites up to 600 °C.

Preliminary Characterization of a Polycaprolactone-SurgihoneyRO Electrospun Mesh for Skin Tissue Engineering

Skin is a hierarchical and multi-cellular organ exposed to the external environment with a key protective and regulatory role. Wounds caused by disease and trauma can lead to a loss of function, which can be debilitating and even cause death. Accelerating the natural skin healing process and minimizing the risk of infection is a clinical challenge. Electrospinning is a key technology in the development of wound dressings and skin substitutes as it enables extracellular matrix-mimicking fibrous structures and delivery of bioactive materials. Honey is a promising biomaterial for use in skin tissue engineering applications and has antimicrobial properties and potential tissue regenerative properties. This preliminary study investigates a solution electrospun composite nanofibrous mesh based on polycaprolactone and a medical grade honey, SurgihoneyRO. The processing conditions were optimized and assessed by scanning electron microscopy to fabricate meshes with uniform fiber diameters and minimal presence of beads. The chemistry of the composite meshes was examined using Fourier transform infrared spectroscopy and X-ray photon spectroscopy showing incorporation of honey into the polymer matrix. Meshes incorporating honey had lower mechanical properties due to lower polymer content but were more hydrophilic, resulting in an increase in swelling and an accelerated degradation profile. The biocompatibility of the meshes was assessed using human dermal fibroblasts and adipose-derived stem cells, which showed comparable or higher cell metabolic activity and viability for SurgihoneyRO-containing meshes compared to polycaprolactone only meshes. The meshes showed no antibacterial properties in a disk diffusion test due to a lack of hydrogen peroxide production and release. The developed polycaprolactone-honey nanofibrous meshes have potential for use in skin applications.

A Highly Ordered, Nanostructured Fluorinated CaP-Coated Melt Electrowritten Scaffold for Periodontal Tissue Regeneration

Periodontitis is a chronic inflammatory, bacteria-triggered disorder affecting nearly half of American adults. Although some level of tissue regeneration is realized, its low success in complex cases demands superior strategies to amplify regenerative capacity. Herein, highly ordered scaffolds are engineered via Melt ElectroWriting (MEW), and the effects of strand spacing, as well as the presence of a nanostructured fluorinated calcium phosphate (F/CaP) coating on the adhesion/proliferation, and osteogenic differentiation of human-derived periodontal ligament stem cells, are investigated. Upon initial cell-scaffold interaction screening aimed at defining the most suitable design, MEW poly(ε-caprolactone) scaffolds with 500 µm strand spacing are chosen. Following an alkali treatment, scaffolds are immersed in a pre-established solution to allow for coating formation. The presence of a nanostructured F/CaP coating leads to a marked upregulation of osteogenic genes and attenuated bacterial growth. In vivo findings confirm that the F/CaP-coated scaffolds are biocompatible and lead to periodontal regeneration when implanted in a rat mandibular periodontal fenestration defect model. In aggregate, it is considered that this work can contribute to the development of personalized scaffolds capable of enabling tissue-specific differentiation of progenitor cells, and thus guide simultaneous and coordinated regeneration of soft and hard periodontal tissues, while providing antimicrobial protection.

The effect of Allium cepa extract on the chitosan/PLGA scaffolds bioactivity

Allium cepa extracts (AC) allow the fabrication of a biomaterial that, together with chitosan and PLGA, could be osteoconductive and promote a better and faster regeneration of bone tissue, with biocompatibility and biomineralization properties. In this work, scaffolds were developed by the thermally induced phase separation (TIPS) technique. An in vitro bioactivity analysis was performed using simulated body fluid (SBF). Scanning electron microscopy (SEM), energy dispersion spectroscopy, and infrared spectroscopy were used for the scaffolds characterization. The results showed a structure with a pore size distribution between 50 and 100 μm, which allowed the uniform formation of biological apatite crystals on the surface of the scaffolds. The chitosan/policaprolactone/Allium cepa scaffold (ChPAC) showed the most promising results with a ratio of P/Ca between 1.6 and 1.7, a value very close to that of hydroxyapatite.

A comparative analysis of solvent cast 3D printed carbonyl iron powder reinforced polycaprolactone polymeric stents for intravascular applications

In the present research, the effectiveness of developed methodology based on solvent cast 3D printing technique was investigated by printing the different geometries of the stents. The carbonyl iron powder (CIP) reinforced polycaprolactone (CIPC) was used to print three pre-existing stent designs such as ABBOTT BVS1.1, PALMAZ-SCHATZ, and ART18Z. The physicochemical behavior was analyzed by X-ray diffraction and scanning electron microscopy. The radial compression test, three-point bending test and stent deployment test were carried out to analyze the mechanical behavior. The degradation behavior of the stents was investigated in static as well as dynamic environment. To investigate the hemocompatible and cytocompatible behaviors of the stents, platelet adhesion test, hemolysis test, protein adsorption, in vitro cell viability test, and live/dead cell viability assay were performed. The results revealed that stents had the adequate mechanical properties to perform the necessary functions in the human coronary. The degradation studies showed slower degradation rate in the dynamic environment in comparison to static environment. in vitro biological analysis indicated that the stents represented excellent resistance to thrombosis, hemocompatible functions as well as cytocompatible nature. The results concluded that PALMAZ-SCHATZ stent represented better mechanical properties, cell viability, blood compatibility, and degradation behavior.

Drug-eluting PCL/graphene oxide nanocomposite scaffolds for enhanced osteogenic differentiation of mesenchymal stem cells

Recently, drug-eluting nanofibrous scaffolds have attracted a great attention to enhance the cell differentiation through biomimicking the extracellular matrix (ECM) in regenerative medicine. In this study, electrospun nanocomposite polycaprolactone (PCL)-based scaffolds containing synthesized graphene oxide (GO) nanosheets and osteogenic drugs, i.e. dexamethasone and simvastatin were fabricated. The physicochemical and surface properties of the scaffolds were investigated through FTIR, wettability, pH, and drug release studies. The cell viability, differentiation, and biomineralization were studied on mesenchymal stem cells (MSCs) by Alamar Blue, alkaline phosphatase (ALP) activity, and Alizarin Red-S staining, respectively. Uniformly distributed GO (thickness < 1 nm) in PCL nanofibers was observed by electron microscopy. It was revealed that the addition of GO and the drugs improved the hydrophilicity, cell viability, and osteogenic differentiation, in addition to pH changes, in comparison with PCL scaffolds. Despite the notable reduction in the cell viability, significant differentiation was revealed by ALP assay on PCL/GO-Dex scaffolds. Noteworthy, a twofold increase in the osteogenic differentiation was observed in comparison with the cells cultured in osteogenic differentiation medium, while a significant biomineralization was observed. The results of this study indicate the synergistic effect of GO and dexamethasone on improving osteogenic differentiation of drug-eluting nanocomposite scaffolds in bone tissue engineering applications.

Effect of extrapallial protein of Mytilus californianus on the process of in vitro biomineralization of chitosan scaffolds

Biomineralization is the process by which diverse organisms have the capacity to create heterogeneous accumulations, derived from organic and inorganic compounds that induce the process of mineral formation. An example of this can be seen an extrapallial protein (EP) of Mytilus californianus, which is responsible for carrying out the biomineralization process. In order to determine their ability to perform the biomineralization process, EP protein was absorbed and mixed in chitosan scaffolds which were tested in simulated physiological fluid. The materials were analyzed by FTIR spectroscopy, field emission scanning electron microscopy-energy-dispersive electron X-ray spectroscopy andX-ray diffraction. Results confirmed that the EP protein stimulates the rapid growth of biological apatite on the chitosan scaffolds. The mixing method favored more the apatite growth as well as the formation of second nucleation sites than the immersion method.

Cytokine Regulation from Human Peripheral Blood Leukocytes Cultured In Vitro with Silver Doped Bioactive Glasses Microparticles

Bioactive glasses (BG) applications include tissue engineering for bone regeneration, coating for implants, and scaffolds for wound healing. BG can be conjugated to ions like silver, which might add some antimicrobial properties to this biomaterial. The immunomodulatory activity of ion-doped bioactive glasses particles was not investigated before. The aim of this work was to evaluate the cytotoxic and immunomodulatory effect of BG and silver-doped bioactive glass (BGAg) in human peripheral blood cells. BG and BGAg samples belonging to the system 58SiO₂•(36-x)CaO·6P₂O₅·xAg₂O, where x = 0 and 1 mol%, respectively, were synthesized via sol–gel method and characterized. Cytotoxicity, modulation of cytokine production (TNF-α, IL-1β, IL-6, IL-4, and IL-10), and oxidative stress response were investigated in human polymorphonuclear cells (PMNs) and peripheral blood mononuclear cells (PBMCs) cultures. Cell viability in the presence of BG or BGAg was concentration-dependent. In addition, BGAg presented higher PBMCs toxicity (LC50 = 0.005%) when compared to BG (LC50 = 0.106%). Interestingly, interleukin4 was produced by PBMCs in response to BG and BGAg in absence of phytohemagglutinin (PHA) and did not modulate PHA-induced cytokine levels. Subtoxic concentrations (0.031% for BG and 0.0008% for BGAg) did not change other cytokines in PBMCs nor reactive oxygen species (ROS) production by PMN. However, BG and BGAg particles decreased zymosan-induced ROS levels in PMN. Although ion incorporation increased BG cytotoxicity, the bioactive glass particles demonstrated a in vitro anti-inflammatory potencial. Future studies are needed to clarify the scavenger potential of the BG/BGAg particles/scaffolds as well as elucidate the effect of the anti-inflammatory potential in modulating tissue growth in vivo.

In vitro osteogenic differentiation of stem cells with different sources on composite scaffold containing natural bioceramic and polycaprolactone

Stem cells can be obtained from a variety of sources. To compare the effect of cell source on the osteogenic differentiation potential, buccal fat pad-derived mesenchymal stem cells (BFP-MSCs), bone marrow-derived MSCs (BM-MSCs) and unrestricted somatic stem cells (USSCs) with different accessibility in time and region, were cultured on bioceramic (Bio-Oss^®) coated electrospun polycaprolactone (PCL) scaffold (PCL-Bio). After scaffold characterization, stem cells proliferation and osteogenic differentiation were investigated by MTT and Alizarin red staining, alkaline phosphatase activity, calcium content and gene expression assays. Proliferation rate of the stem cells was not significantly different with each other, only USSCs showed significantly lower proliferation rate while cultured on PCL-Bio; although, PCL-Bio showed better proliferation support in comparison with tissue culture plate and PCL. Mineralization of the BM-MSCs was significantly higher than others, while BFP-MSCs were close to it. Highest ALP activity was detected in BFP-MSCs cultured on PCL-Bio. USSCs demonstrated higher gene expression level in three genes, although differences were not huge compared to others. According to the results and due to the availability, facilitated preparation procedure and less patients suffering, BFP-MSCs have a better choice than BM-MSCs and USSCs for use in bone tissue engineering.

Bioactive scaffolds for osteochondral regeneration

Treatment for osteochondral defects remains a great challenge. Although several clinical strategies have been developed for management of osteochondral defects, the reconstruction of both cartilage and subchondral bone has proved to be difficult due to their different physiological structures and functions. Considering the restriction of cartilage to self-healing and the different biological properties in osteochondral tissue, new therapy strategies are essential to be developed. This review will focus on the latest developments of bioactive scaffolds, which facilitate the osteogenic and chondrogenic differentiation for the regeneration of bone and cartilage. Besides, the topic will also review the basic anatomy, strategies and challenges for osteochondral reconstruction, the selection of cells, biochemical factors and bioactive materials, as well as the design and preparation of bioactive scaffolds. Specifically, we summarize the most recent developments of single-type bioactive scaffolds for simultaneously regenerating cartilage and subchondral bone. Moreover, the future outlook of bioactive scaffolds in osteochondral tissue engineering will be discussed. This review offers a comprehensive summary of the most recent trend in osteochondral defect reconstruction, paving the way for the bioactive scaffolds in clinical therapy.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This review summaries the latest developments of single-type bioactive scaffolds for regeneration of osteochondral defects. We also highlight a new possible translational direction for cartilage formation by harnessing bioactive ions and propose novel paradigms for subchondral bone regeneration in application of bioceramic scaffolds.

Preparation and in vitro evaluation of polycaprolactone/PEG/bioactive glass nanopowders nanocomposite membranes for GTR/GBR applications

In the present study, nanocomposite membranes are investigated using poly-ε-caprolactone (PCL), polyethylene glycol (PEG) and bioactive glass nanopowders (BGs) synthesized via solvent casting method with different reinforcement rates of BGs consisting of 3, 5 and 7 wt% for regenerating the periodontal tissue in vitro. These prepared membranes were evaluated by a vast range of essential tests; including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Transmition-electron microscopy (TEM), tensile testing before and after soaking in PBS solution, degradation and contact angle assessments as well as cell culture assays. In spite of the fact that the percentage of Cu incorporated into BGs was trivial, this negligible amount exerted major cytotoxic impact upon cells during in vitro cell tests. According to the results, the blended-membrane contained 7 wt% copper-free BGs indicated optimum characteristics including satisfactory mechanical and biodegradation features, more wettable surface, higher proliferation rates of adipose-derived stem cells (ADSCs), superior ALP activity and brilliant bone mineralization capacity which was confirmed by Alizarin red assay. As a consequence, it can be used as a desirable candidate for guided tissue/bone regeneration (GTR/GBR) to accelerate bone tissue healing.

Magnesium oxide nanoparticle-loaded polycaprolactone composite electrospun fiber scaffolds for bone-soft tissue engineering applications: in-vitro and in-vivo evaluation

The objective of the present investigation was to assess the potential of magnesium oxide nanoparticle (MgO NP)-loaded electrospun polycaprolactone (PCL) polymer composites as a bone-soft tissue engineering scaffold. MgO NPs were synthesized using a hydroxide precipitation sol-gel method and characterized using field emission gun-scanning electron microscopy/energy-dispersive x-ray spectroscopy (FEG-SEM/EDS), field emission gun-transmission electron microscopy (FEG-TEM), and x-ray diffraction (XRD) analysis. PCL and MgO-PCL nanocomposite fibers were fabricated using electrospinning with trifluoroethanol as solvent at 19 kV applied voltage and 1.9 ml h^-1 flow rate as optimized process parameters, and were characterized by FEG-TEM, FEG-SEM/EDS, XRD, and differential scanning calorimetry analyses. Characterization studies of as-synthesized nanoparticles revealed diffraction peaks indexed to various crystalline planes peculiar to MgO particles with hexagonal and cubical shape, and 40-60 nm size range. Significant improvement in mechanical properties (tensile strength and elastic modulus) of nanocomposites was observed as compared to neat polymer specimens (fourfold and threefold, respectively), due to uniform dispersion of nanofillers along the polymer fiber length. There was a remarkable bioactivity shown by nanocomposite scaffolds in immersion test, as indicated by formation of surface hydroxyapatite layer by the third day of incubation. MgO-loaded electrospun PCL mats showed enhanced in-vitro biological performance with osteoblast-like MG-63 cells in terms of adhesion, proliferation, and marked differentiation marker activity owing to greater surface roughness, nanotopography, and hydrophilicity facilitating higher protein adsorption. In-vivo subcutaneous implantation study in Sprague Dawley rats revealed initial moderate inflammatory tissue response near implant site at the second week timepoint that subsided later (eighth week) with no adverse effect on vital organ functionalities as seen in histopathological analysis supported by serum biochemical and hematological parameters which did not deviate significantly from normal physiological range, indicating good biocompatibility in-vivo. Thus, MgO-PCL nanocomposite electrospun fibers have potential as an efficient scaffold material for bone-soft tissue engineering applications.

Fast-degrading PLA/ORMOGLASS fibrous composite scaffold leads to a calcium-rich angiogenic environment

The success of scaffold implantation in acellular tissue engineering approaches relies on the ability of the material to interact properly with the biological environment. This behavior mainly depends on the design of the graft surface and, more precisely, on its capacity to biodegrade in a well-defined manner (nature of ions released, surface-to-volume ratio, dissolution profile of this release, rate of material resorption, and preservation of mechanical properties). The assessment of the biological behavior of temporary templates is therefore very important in tissue engineering, especially for composites, which usually exhibit complicated degradation behavior. Here, blended polylactic acid (PLA) calcium phosphate ORMOGLASS (organically modified glass) nanofibrous mats have been incubated up to 4 weeks in physiological simulated conditions, and their morphological, topographical, and chemical changes have been investigated. The results showed that a significant loss of inorganic phase occurred at the beginning of the immersion and the ORMOGLASS maintained a stable composition afterward throughout the degradation period. As a whole, the nanostructured scaffolds underwent fast and heterogeneous degradation. This study reveals that an angiogenic calcium-rich environment can be achieved through fast-degrading ORMOGLASS/PLA blended fibers, which seems to be an excellent alternative for guided bone regeneration.

Synthesis, properties and applications of biodegradable polymers derived from diols and dicarboxylic acids: from polyesters to poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.

Porous silicon confers bioactivity to polycaprolactone composites in vitro

Silicon is an essential element for healthy bone development and supplementation with its bioavailable form (silicic acid) leads to enhancement of osteogenesis both in vivo and in vitro. Porous silicon (pSi) is a novel material with emerging applications in opto-electronics and drug delivery which dissolves to yield silicic acid as the sole degradation product, allowing the specific importance of soluble silicates for biomaterials to be investigated in isolation without the elution of other ionic species. Using polycaprolactone as a bioresorbable carrier for porous silicon microparticles, we found that composites containing pSi yielded more than twice the amount of bioavailable silicic acid than composites containing the same mass of 45S5 Bioglass. When incubated in a simulated body fluid, the addition of pSi to polycaprolactone significantly increased the deposition of calcium phosphate. Interestingly, the apatites formed had a Ca:P ratio directly proportional to the silicic acid concentration, indicating that silicon-substituted hydroxyapatites were being spontaneously formed as a first order reaction. Primary human osteoblasts cultured on the surface of the composite exhibited peak alkaline phosphatase activity at day 14, with a proportional relationship between pSi content and both osteoblast proliferation and collagen production over 4 weeks. Culturing the composite with J744A.1 murine macrophages demonstrated that porous silicon does not elicit an immune response and may even inhibit it. Porous silicon may therefore be an important next generation biomaterial with unique properties for applications in orthopaedic tissue engineering.

Osteochondral tissue engineering with biphasic scaffold: current strategies and techniques

The management of osteoarthritis (OA) remains challenging and controversial. Although several clinical options exist for the treatment of OA, regeneration of the damaged articular cartilage has proved difficult due to the limited healing capacity. With the advancements in tissue engineering and cell-based technologies over the past decade, new therapeutic options for patients with osteochondral lesions potentially exist. This review will focus on the feasibility of tissue-engineered biphasic scaffolds, which can mimic the native osteochondral complex, for osteochondral repair and highlight the recent development of these techniques toward tissue regeneration. Moreover, basic anatomy, strategy for osteochondral repair, the design and fabrication methods of scaffolds, as well as the choice of cells, growth factor, and materials will be discussed. Specifically, we focus on the latest preclinical animal studies using large animals and clinical trials with high clinical relevance. In turn, this will facilitate an understanding of the latest trends in osteochondral repair and contribute to the future application of such clinical therapies in patients with OA.

Tissue growth into three-dimensional composite scaffolds with controlled micro-features and nanotopographical surfaces

Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were also used to reveal the effect of particle size on the cell behavior. Observation of tissue growth and enzyme activity on two-dimensional (2D) films and three-dimensional (3D) scaffolds showed effects of nanoparticle inclusion and of surface curvature on the cellular adhesion, proliferation, and kinetics of preosteoblastic cells (MC3T3-E1) tissue growth into the pore channels. It was found that the presence of nanoparticles in the substrate impaired cellular adhesion and proliferation in 3D structures. Evaluation of alkaline phosphate activity showed that the presence of the hard particles affects differentiation of the cells on 2D films. Notwithstanding, the effect of particles on cell differentiation was not as strong as that seen by the curvature of the substrate. We observed different effects of nanofeatures on 2D structures with those of 3D scaffolds, which influence the cell proliferation and differentiation for non-load-bearing applications in bone regenerative medicine.

Microstructure and chemistry affects apatite nucleation on calcium phosphate bone graft substitutes

The bioactivity of calcium phosphate bone grafts of varying chemistry and strut-porosity was compared by determining the rate of formation of hydroxycarbonate apatite crystals on the material surface after being soaked in simulated body fluid for up to 30 days. Three groups of silicate-substituted hydroxyapatite material were tested, with each group comprising a different quantity of strut-porosity (23, 32, and 46 % volume). A commercially available porous β-tricalcium phosphate bone graft substitute was tested for comparison. Results indicate that strut-porosity of a material affects the potential for formation of a precursor to bone-like apatite and further confirms previous findings that β-tricalcium phosphate is less bioactive than hydroxyapatite.

Hot melt poly-ε-caprolactone/poloxamine implantable matrices for sustained delivery of ciprofloxacin

It has been suggested that prevention and treatment of osteomyelitis could be achieved through local drug delivery using implantable devices, which provide therapeutic levels at the infection site with minimum side-effects. Physical blends of polycaprolactone (PCL) and poloxamine (Tetronic®) were prepared by applying a solvent-free hot melting approach to obtain cytocompatible implants with a tunable bioerosion rate, ciprofloxacin release profile and osteoconductive features. Differential scanning calorimetry and X-ray analysis indicate that the hydrophilic poloxamine varieties T908, T1107, and T1307 are miscible with PCL, while the hydrophobic block copolymer T1301 is immiscible. Incorporation of the block copolymer at weight ratios ranging from 25 to 75 wt.% led to matrices with viscoelastic parameters in the range of those of fresh cortical bone. Once immersed in buffer the matrices underwent a similar weight loss in the first week to the content of poloxamine, followed by a slower erosion rate due to PCL. The initial rapid erosion and the increase in porosity partially explain the observed burst of ciprofloxacin release, which is more intense in the PCL:T1301 formulation due to drug/T1301 repulsion due to polarity. The matrices sustained ciprofloxacin release for several months (<50% released after 3 months) and showed in vitro efficacy against Staphylococcus aureus, eradicating the bacteria in less than 48 h. PCL:poloxamine was cytocompatible with osteoblasts and the matrices prepared with low proportions of T908 were also compatible with mesenchymal stem cell differentiation to osteoblasts. The influence of the nature and proportion of temperature-responsive poloxamine on the performance of PCL implantable systems was determined.

Electrospun nanofiber-based regeneration of cartilage enhanced by mesenchymal stem cells

Application of biomaterials in combination with stem cells is a novel tissue engineering approach to regenerate cartilage. The objective of this study was to investigate the potential of poly(vinyl alcohol)/polycaprolactone (PVA/PCL) nanofiber scaffolds seeded with rabbit bone marrow-mesenchymal stem cell (BM-MSC) for cartilage tissue engineering in vitro and in vivo. We tested the biocompatibility and mechanical properties of nanofibrous scaffolds using scanning electron microscope, MTT assay, and tensile measurements. The capacity of MSC for chondrogenic differentiation on scaffolds was examined using reverse transcription-polymer chain reaction and immunostaining. For in vivo assessments, PVA/PCL nanofiber scaffolds with or without MSC were implanted into rabbit full-thickness cartilage defects. To evaluate cartilage regeneration, semi-quantitative grading and histological analysis were performed. Our results showed that PVA/PCL scaffolds supported the proliferation and chondrogenic differentiation of MSC in vitro. Moreover, the animals treated with cell-seeded PVA/PCL scaffolds showed improved healing of defects compared with untreated control and those which received cell-free scaffolds. Our findings suggest that PVA/PCL scaffolds incorporated with MSC can serve as a suitable graft for articular cartilage reconstruction.

Effect of long-term in vitro testing on the properties of bioactive glass-polysulfone composites

The combination of bioactive ceramics and polymers can allow the preparation of composites with tailorable mechanical properties and bioactive behavior. In these composites, bioactive ceramics can act as a source of both reinforcement and bioactivity, while the polymer matrix can add toughness and processability to the material. On the other hand, the effect of using a highly dimensional unstable phase as a reinforcing agent on the long-term properties of the composite is a major concern regarding the lifetime of possible applications. In this work, a bioactive glass-polysulfone particulate composite was prepared by hot-pressing at 215 degrees C a mixture of polysulfone and different concentrations of bioactive glass particles (Bioglass 45S5, particle size range: 125-106 microm) to yield composites having 20 and 40 vol % of bioactive glass particles. The obtained composites were exposed to a simulated body fluid at 37 degrees C for different periods of time ranging from 1 h to 60 days. After the test, the mechanical properties of the composites were investigated by a four-point bending test, while DMS (dynamic mechanical spectroscopy) was used to identify the effect of water on the structure and behavior of the composite. The interface between glass particles and the polymer was also investigated by SEM/EDX and diffuse reflection infrared spectroscopy. The results showed that a decay in the mechanical properties of the composites within the first 20 h of test can occur. Otherwise, after this initial decay, no more pronounced reduction in properties could be noted. The analyses of the fracture surface of composites tested in vitro indicated the hydration of the surface of the particles. Therefore, it was concluded that water migration through the interface of the composite causes surface dissolution of glass particles and formation of voids, which were responsible for the observed decay in mechanical properties. Composites with modified interfaces revealed less damaged fracture surfaces than composites with untreated interfaces.

Rayleigh theory of ultrasound scattering applied to liquid-filled contrast nanoparticles

We present a novel modified theory based upon Rayleigh scattering of ultrasound from composite nanoparticles with a liquid core and solid shell. We derive closed form solutions to the scattering cross-section and have applied this model to an ultrasound contrast agent consisting of a liquid-filled core (perfluorooctyl bromide, PFOB) encapsulated by a polymer shell (poly-caprolactone, PCL). Sensitivity analysis was performed to predict the dependence of the scattering cross-section upon material and dimensional parameters. A rapid increase in the scattering cross-section was achieved by increasing the compressibility of the core, validating the incorporation of high compressibility PFOB; the compressibility of the shell had little impact on the overall scattering cross-section although a more compressible shell is desirable. Changes in the density of the shell and the core result in predicted local minima in the scattering cross-section, approximately corresponding to the PFOB-PCL contrast agent considered; hence, incorporation of a lower shell density could potentially significantly improve the scattering cross-section. A 50% reduction in shell thickness relative to external radius increased the predicted scattering cross-section by 50%. Although it has often been considered that the shell has a negative effect on the echogeneity due to its low compressibility, we have shown that it can potentially play an important role in the echogeneity of the contrast agent. The challenge for the future is to identify suitable shell and core materials that meet the predicted characteristics in order to achieve optimal echogenity.

In vitro and in vivo evaluation of the effects of demineralized bone matrix or calcium sulfate addition to polycaprolactone-bioglass composites

The objective of this study was to improve the efficacy of polycaprolactone/bioglass (PCL/BG) bone substitute using demineralized bone matrix (DBM) or calcium sulfate (CS) as a third component. Composite discs involving either DBM or CS were prepared by compression moulding. Bioactivity of discs was evaluated by energy dispersive X-ray spectroscopy (ESCA) and scanning electron microscopy (SEM) following simulated body fluid incubation. The closest Calcium/Phosphate ratio to that of hydroxyl carbonate apatite crystals was observed for PCL/ BG/DBM group (1.53) after 15 day incubation. Addition of fillers increased microhardness and compressive modulus of discs. However, after 4 and 6-week PBS incubations, PCL/BG/DBM discs showed significant decrease in modulus (from 266.23 to 54.04 and 33.45 MPa, respectively) in parallel with its highest water uptakes (36.3 and 34.7%). Discs preserved their integrity with only considerable weight loss (7.5-14.5%) in PCL/BG/DBM group. In vitro cytotoxicity tests showed that all discs were biocompatible.