Zinc-Doped Bioactive Glass/Polycaprolactone Hybrid Scaffolds Manufactured by Direct and Indirect 3D Printing Methods for Bone Regeneration

A novel organic-inorganic hybrid, based on SiO2-CaO-ZnO bioactive glass (BG) and polycaprolactone (PCL), associating the highly bioactive and versatile bioactive glass with clinically established PCL was examined. The BG-PCL hybrid is obtained by acid-catalyzed silica sol-gel process inside PCL solution either by direct or indirect printing. Apatite-formation tests in simulated body fluid (SBF) confirm the ion release along with the hybrid's bone-like apatite forming. Kinetics differ significantly between directly and indirectly printed scaffolds, the former requiring longer periods to degrade, while the latter demonstrates faster calcium phosphate (CaP) formation. Remarkably, Zn diffusion and accumulation are observed at the surface within the newly formed active CaP layer. Zn release is found to be dependent on printing method and immersion medium. Investigation of BG at the atomic scale reveals the ambivalent role of Zn, capable of acting both as a network modifier and as a network former linking the BG silicate network. In addition, hMSCs viability assay proves no cytotoxicity of the Zn hybrid. LIVE/DEAD staining demonstrated excellent cell viability and proliferation for over seven weeks. Overall, this hybrid material either non-doped or doped with a metal trace element is a promising candidate to be translated to clinical applications for bone regeneration.

Bioactive glass-based organic/inorganic hybrids: an analysis of the current trends in polymer design and selection

Bioactive glass-based organic/inorganic hybrids are a family of materials holding great promise in the biomedical field. Developed from bioactive glasses following recent advances in sol-gel and polymer chemistry, they can overcome many limitations of traditional composites typically used in bone repair and orthopedics. Thanks to their unique molecular structure, hybrids are often characterized by synergistic properties that go beyond a mere combination of their two components; it is possible to synthesize materials with a wide variety of mechanical and biological properties. The polymeric component, in particular, can be tailored to prepare tough, load-bearing materials, or rubber-like elastomers. It can also be a key factor in the determination of a wide range of interesting biological properties. In addition, polymers can also be used within hybrids as carriers for therapeutic ions (although this is normally the role of silica). This review offers a brief look into the history of hybrids, from the discovery of bioactive glasses to the latest developments, with a particular emphasis on polymer design and chemistry. First the benefits and limitations of hybrids will be discussed and compared with those of alternative approaches (for instance, nanocomposites). Then, key advances in the field will be presented focusing on the polymeric component: its chemistry, its physicochemical and biological advantages, its drawbacks, and selected applications. Comprehensive tables summarizing all the polymers used to date to fabricate sol-gel hybrids for biomedical applications are also provided, to offer a handbook of all the available candidates for hybrid synthesis. In addition to the current trends, open challenges and possible avenues of future development are proposed.

Osteogenic Effect of Fisetin Doping in Bioactive Glass/Poly(caprolactone) Hybrid Scaffolds

Treating large bone defects or fragile patients may require enhancing the bone regeneration rate to overcome a weak contribution from the body. This work investigates the osteogenic potential of nutrient fisetin, a flavonoid found in fruits and vegetables, as a doping agent inside the structure of a SiO₂-CaO bioactive glass-poly(caprolactone) (BG-PCL) hybrid scaffold. Embedded in the full mass of the BG-PCL hybrid during one-pot synthesis, we demonstrate fisetin to be delivered sustainably; the release follows a first-order kinetics with active fisetin concentration being delivered for more than 1 month (36 days). The biological effect of BG-PCL-fisetin-doped scaffolds (BG-PCL-Fis) has been highlighted by in vitro and in vivo studies. A positive impact is demonstrated on the adhesion and the differentiation of rat primary osteoblasts, without an adverse cytotoxic effect. Implantation in critical-size mouse calvaria defects shows bone remodeling characteristics and remarkable enhancement of bone regeneration for fisetin-doped scaffolds, with the regenerated bone volume being twofold that of nondoped scaffolds and fourfold that of a commercial trabecular bovine bone substitute. Such highly bioactive materials could stand as competitive alternative strategies involving biomaterials loaded with growth factors, the use of the latter being the subject of growing concerns.

Tailored therapeutic release from polycaprolactone-silica hybrids for the treatment of osteomyelitis: antibiotic rifampicin and osteogenic silicates

The treatment of osteomyelitis, a destructive inflammatory process caused by bacterial infections to bone tissue, is one of the most critical challenges of orthopedics and bone regenerative medicine. The standard treatment consists of intense antibiotic therapies combined with tissue surgical debridement and the application of a bone defect filler material. Unfortunately, commercially available candidates, such as gentamicin-impregnated polymethylmethacrylate cements, possess very poor pharmacokinetics (i.e., 24 hours burst release) and little to no regenerative potential. Fostered by the intrinsic limitations associated with conventional treatments, alternative osteostimulative biomaterials with local drug delivery have recently started to emerge. In this study, we propose the use of a polycaprolactone-silica sol-gel hybrid material as carrier for the delivery of rifampicin, an RNA-polymerase blocker often used to treat bone infections, and of osteostimulative silicate ions. The release of therapeutic agents from the material is dual, offering two separate and simultaneous effects, and decoupled, meaning that the kinetics of rifampicin and silicate releases are independent from each other. A series of hybrid formulations with increasing amounts of rifampicin was prepared. The antibiotic loading efficacy, as well as the release profiles of rifampicin and silicates were measured. The characterization of cell viability and differentiation of rat primary osteoblasts and antibacterial performance were also performed. Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli were selected due to their high occurrence in bone infections. Results confirmed that rifampicin can be successfully loaded within the hybrids without significant degradation and that it is possible to tailor the antibiotic release according to need. Once in a physiological environment, the rapid release of silicates was associated with optimal cell proliferation and the overexpression of osteoblastic differentiation. Simultaneously, rifampicin is delivered over the course of several weeks with significant inhibition of all tested strains. In particular, the materials caused a growth reduction of 7-10 orders of magnitude in Staphylococcus aureus, the major strain responsible for osteomyelitis worldwide. Our data strongly suggest that PCL/silica hybrids are a very promising candidate to develop bone fillers with superior biological performance compared to currently available options. Thanks to their unique synthesis route and their dual tailored release they can promote bone regeneration while reducing the risk of infection for several weeks upon implantation.

[Swertiamarin alleviates diabetic peripheral neuropathy in rats by suppressing NOXS/ ROS/NLRP3 signal pathway]

OBJECTIVE

To observe the therapeutic effect of swertiamarin on diabetic peripheral neuropathy (DPN) in rats and explore the molecular mechanism in light of the NOXS/ROS/NLRP3 signal pathway.

OBJECTIVE

Thirty-two SD rats were randomly divided into control group, DPN model group (treated with saline), swertiamarin (5 mg/kg) treatment group and NOXS inhibitor (10 mL/kg DPI) treatment group. Rat models of DPN were established in the latter 3 groups by intraperitoneal injections of STZ, and the treatments were administered on days 1, 7 and 14 after modeling. Tactile hypersensitivity of the rats was evaluated 30 min after the treatment. The expressions of NOXS, ROS, NLRP3 and inflammatory factors in the spinal cord tissue were detected using ELISA, and the protein expressions of NOXS, ROS, and NLRP3 were also detected with Western blotting.

OBJECTIVE

Compared with those in the control group, the rats in DPN group showed significant hyperalgesia (P < 0.001), increased expressions of TNF-α (P < 0.001) and IL-6 (P < 0.001), decreased expressions of TGF-β (P < 0.001), and increased expressions of NOXS/ROS/NLRP3 signal pathway (P < 0.001). Compared with those in DPN model group, the rats with swertiamarin treatment showed improved hyperalgesia (P < 0.001), decreased expressions of TNF-α (P=0.03) and IL-6 (P=0.002), increased expressions of TGF-β (P=0.04), and decreased expressions of NOXS (P < 0.001), ROS (P < 0.001) and NLRP3 (P=0.002). Treatment with swertiamarin and the NOXS inhibitor produced similar effects on the expressions of the inflammatory factors in the rat models (P>0.05).

OBJECTIVE

DPN effectively relieves hyperalgesia in rat models of DPN by restoring the balance in the expressions of the inflammatory factors by suppressing NOXs/ROS/NLRP3 signaling pathway.

Watchers do not follow the eye movements of Walkers

Eye movements are a functional signature of how the visual system effectively decodes and adapts to the environment. However, scientific knowledge in eye movements mostly arises from studies conducted in laboratories, with well-controlled stimuli presented in constrained unnatural settings. Only a few studies have attempted to directly compare and assess whether eye movement data acquired in the real world generalize with those in laboratory settings, with same visual inputs. However, none of these studies controlled for both the auditory signals typical of real-world settings and the top-down task effects across conditions, leaving this question unresolved. To minimize this inherent gap across conditions, we compared the eye movements recorded from observers during ecological spatial navigation in the wild (the Walkers) with those recorded in laboratory (the Watchers) on the same visual and auditory inputs, with both groups performing the very same active cognitive task. We derived robust data-driven statistical saliency and motion maps. The Walkers and Watchers differed in terms of eye movement characteristics: fixation number and duration, saccade amplitude. The Watchers relied significantly more on saliency and motion than the Walkers. Interestingly, both groups exhibited similar fixation patterns towards social agents and objects. Altogether, our data show that eye movements patterns obtained in laboratory do not fully generalize to real world, even when task and auditory information is controlled. These observations invite to caution when generalizing the eye movements obtained in laboratory with those of ecological spatial navigation.

Optimized Bioactive Glass: the Quest for the Bony Graft

Technological advances have provided surgeons with a wide range of biomaterials. Yet improvements are still to be made, especially for large bone defect treatment. Biomaterial scaffolds represent a promising alternative to autologous bone grafts but in spite of the numerous studies carried out on this subject, no biomaterial scaffold is yet completely satisfying. Bioactive glass (BAG) presents many qualifying characteristics but they are brittle and their combination with a plastic polymer appears essential to overcome this drawback. Recent advances have allowed the synthesis of organic-inorganic hybrid scaffolds combining the osteogenic properties of BAG and the plastic characteristics of polymers. Such biomaterials can now be obtained at room temperature allowing organic doping of the glass/polymer network for a homogeneous delivery of the doping agent. Despite these new avenues, further studies are required to highlight the biological properties of these materials and particularly their behavior once implanted in vivo. This review focuses on BAG with a particular interest in their combination with polymers to form organic-inorganic hybrids for the design of innovative graft strategies.

Polycaprolactone / bioactive glass hybrid scaffolds for bone regeneration

Bioactive glasses (BG) bond to bone and stimulate bone regeneration, but they are brittle. Inorganicorganic hybrids appear as promising bone substitutes since they associate the bone mineral forming ability of BG with the toughness of polymers. Hybrids comprised of polycaprolactone (PCL) and SiO2-CaO BG were produced by sol-gel chemistry and processed into porous scaffolds with controlled pore and interconnection sizes. The obtained scaffolds are highly flexible, meaning that PCL effectively introduces toughness. Apatite formation is observed within 24 hours of immersion in simulated body fluid (SBF) and is not limited to the surface as the entire hybrid progressively changes into bone-like minerals. The degradation rate is suitable for bone regeneration with a 13.2% weight loss after 8 weeks of immersion. Primary osteoblasts cultured in scaffolds demonstrate that the samples are not cytotoxic and provide good cell adhesion. The in vivo study confirms the bioactivity, biocompatibility and suitable degradation rate of the hybrid. A physiological bone made of trabeculae and bone marrow regenerates. The structure and kinetic of bone regeneration was similar to the implanted commercial standard based on bovine bone, demonstrating that this new synthetic PCL-BG hybrid could perform as well as animal-derived bone substitutes.

Efficacy of fulvestrant in the treatment of postmenopausal women with endocrine-resistant advanced breast cancer in routine clinical practice

INTRODUCTION

This study aimed to describe the efficacy of fulvestrant 500 mg in postmenopausal women with estrogen receptor (ER)-positive advanced/metastatic breast cancer who had disease progression after receiving anti-estrogen therapy in clinical practice, getting real-world data.

MATERIALS AND METHODS

Multicenter, retrospective, observational study conducted in Spain. Postmenopausal women with locally advanced/metastatic ER-positive breast cancer who received treatment with fulvestrant 500 mg after progression with a previous anti-estrogen therapy were eligible. The primary endpoint was progression-free survival (PFS); secondary endpoints were overall survival (OS), clinical benefit rate (CBR), duration of clinical benefit (DoCB), and safety profile.

RESULTS

A total of 263 women were evaluated (median age, 65.8 years). At a median follow-up of 21.5 months, median PFS and OS were 10.6 and 43.2 months, respectively. PFS according to 1st, 2nd, 3rd, and ≥ 4th lines were 11.5, 10.6, 9.9, and 8.5 months, respectively (p = 0.0245). PFS in patients with visceral involvement was 10 months vs 10.6 months in patients without visceral involvement (p = 0.6604), 9.6 months in patients with high Ki67 vs 10 months in patients with low Ki67 (p = 0.7224), and 10.2 months in HER2+ patients vs 10.3 months in HER2- patients (p = 0.6809). The CBR was 56.5% and the DoCB was 18.4 months. The most frequently adverse events were injection site pain (10.3%) and musculoskeletal disorders (7.6%).

CONCLUSIONS

Fulvestrant 500 mg administered in clinical practice was shown to be effective (PFS, 10.6 months; CBR, 56.5%) and well tolerated, in accordance with previous trials.

Abstract OT3-02-07: A phase II study to compare fulvestrant (F) 500mg plus placebo versus (vs) F 500mg plus palbociclib (P) as first line treatment for postmenopausal women with hormone receptor (HR)-positive advanced breast cancer (BC) sensitive to endocrine therapy (ET). “The FLIPPER study” (GEICAM/2014-12)

Background: Delaying/overcoming resistance to ET in HR-positive HER2-negative BC patients (pts) is a major need to futhrt improve safe and efficacious treatment options. F is a selective estrogen receptor (ER) downregulator currently indicated for the treatment of HR-positive metastatic BC in postmenopausal women with disease progression following anti-estrogen therapy. In FIRST trial F 500mg improved median time to progression (TTP) over anastrozole (23.4 vs 13.1 months, respectively) in untreated metastatic BC. P is a selective reversible inhibitor of cyclin-dependent kinase 4/6. FDA granted its accelerated approval based on progression-free survival (PFS) in combination with letrozole for postmenopausal women with ER-positive and HER2-negative advanced BC as initial ET (PALOMA-1). In another study, after progression to ET, P in combination with F resulted in longer PFS than F alone (PALOMA-3).

The high median TTP achieved with F alone (FIRST) coupled with the significant benefit of adding P to F (PALOMA-3) suggest that F 500mg in combination with P in the first-line setting may significantly improve long-term disease control.

Trial Design:This is an international, randomized, double-blind, multicentre phase II study comparing F 500mg in combination with P vs F 500mg plus placebo as first line therapy in postmenopausal women with HR-positive, HER2-negative metastatic BC who have received ≥5 years of adjuvant ET for early disease and remained disease free for &gt;12 months following its completion or have “de novo” metastatic disease. HR and HER2 status will be based on central testing on the most recent tumour biopsy. Patients will be randomized 1:1. The primary objective is to compare the efficacy of both treatment arms in terms of PFS at 1 year according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 by investigator assessment. As secondary efficacy objectives,PFS, Objective Response Rate (ORR), Clinical Benefit Rate (CBR), Overall Survival (OS), and 1-year and 2-year survival probabilities, have been considered. Other secondary objectives include the comparison of safety, tolerability and health-related quality of life between the treatment arms. As exploratory objectives, the identification of promising biomarkers related with response to study therapy and primary/acquired drug resistance. Pts will be stratified by the site of disease (visceral vs non-visceral) and disease presentation at study entry (recurrent disease vs metastatic “de novo”). With a sample size of 190 pts, the analysis would have 80% power to detect a difference between both treatment arms, assuming PFS proportions of 0.545 and 0.695, respectively. This study is sponsored by GEICAM and Cancer Trials Ireland (formerly ICORG) is also participating. Recruitment started in February 2016 with 14 pts included. Analysis of the primary endpoint is planned for Q1 2018. ClinicalTrials.gov identifier:NCT02690480.

Citation Format: Moreno F, Martínez-Jañez N, Garau I, Guerra JA, Alarcón J, Bermejo B, Gonzalez-Cortijo L, Bueno C, Lao J, Bezares S, Rosell L, Blanch A, Caballero R, Carrasco E, Rojo F, Martín M, O'Connor M, Hernando A, Albanell J. A phase II study to compare fulvestrant (F) 500mg plus placebo versus (vs) F 500mg plus palbociclib (P) as first line treatment for postmenopausal women with hormone receptor (HR)-positive advanced breast cancer (BC) sensitive to endocrine therapy (ET). “The FLIPPER study” (GEICAM/2014-12) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT3-02-07.

Bioactive glass–gelatin hybrids: building scaffolds with enhanced calcium incorporation and controlled porosity for bone regeneration

Thanks to their active promotion of bone formation, bioactive glasses (BG) offer unique properties for bone regeneration, but their brittleness prevents them from being used in a wide range of applications.

Cobalt-releasing 1393 bioactive glass-derived scaffolds for bone tissue engineering applications

Loading biomaterials with angiogenic therapeutics has emerged as a promising approach for developing superior biomaterials for engineering bone constructs. In this context, cobalt-releasing materials are of interest as Co is a known angiogenic agent. In this study, we report on cobalt-releasing three-dimensional (3D) scaffolds based on a silicate bioactive glass. Novel melt-derived "1393" glass (53 wt % SiO2, 6 wt % Na2O, 12 wt % K2O, 5 wt % MgO, 20 wt % CaO, and 4 wt % P2O5) with CoO substituted for CaO was fabricated and was used to produce a 3D porous scaffold by the foam replica technique. Glass structural and thermal properties as well as scaffold macrostructure, compressive strength, acellular bioactivity, and Co release in simulated body fluid (SBF) were investigated. In particular, detailed insights into the physicochemical reactions occurring at the scaffold-fluid interface were derived from advanced micro-particle-induced X-ray emission/Rutherford backscattering spectrometry analysis. CoO is shown to act in a concentration-dependent manner as both a network former and a network modifier. At a concentration of 5 wt % CoO, the glass transition point (Tg) of the glass was reduced because of the replacement of stronger Si-O bonds with Co-O bonds in the glass network. Compressive strengths of >2 MPa were measured for Co-containing 1393-derived scaffolds, which are comparable to values of human spongy bone. SBF studies showed that all glass scaffolds form a calcium phosphate (CaP) layer, and for 1393-1Co and 1393-5Co, CaP layers with incorporated traces of Co were observed. The highest Co concentrations of ∼12 ppm were released in SBF after reaction for 21 days, which are known to be within therapeutic ranges reported for Co(2+) ions.

Bioactive glass nanoparticles obtained through sol-gel chemistry

Different sol-gel strategies based on the Stöber method are proposed enabling preparation of nanoparticles of SiO2-CaO bioactive glass with different size, narrow size distribution and good dispersion capability. Eu(3+)-doped glass nanoparticles with luminescent properties can also be obtained.

Posterior approach for accessory-suprascapular nerve transfer: an electrophysiological outcomes study

The aim of this study was to retrospectively investigate the electrophysiological results obtained after employing the posterior approach for spinal accessory nerve-suprascapular nerve (SAN-SSN) transfer, and to compare this with the traditional anterior approach. SAN-SSN transfer was performed in 74 patients with brachial plexus injury. The posterior approach was used in 35 patients and the anterior approach was used in 39 patients. Electrophysiological examination was conducted and analyzed postoperatively. There was no significant difference between approaches in the time it took for the infraspinatus to show low-incidence motor unit action potentials (MUAPs) and an incomplete interference pattern. In addition, the final ratio of patients that showed regeneration potential of the infraspinatus was not significantly different between the approaches. Furthermore, latency and wave amplitude showed a linear regression with post-operative time in the posterior approach group. In the posterior approach group, the final abduction of the shoulder was positively correlated with the amplitude. The posterior approach for SAN-SSN is an effective potential alternative technique that may be appropriate for some clinical situations.

Outcome of nerve transfers for traumatic complete brachial plexus avulsion: results of 28 patients by DASH and NRS questionnaires

The objective of this study was to evaluate outcomes of patients who suffered complete brachial plexus avulsion before and after nerve transfers by assessing upper extremity function and pain using the DASH and NRS questionnaires. Patients who underwent nerve transfers improved their DASH and NRS scores compared with before surgery. Although individually there was no correlation with improved scores, the triple combination of rehabilitation exercises, electrical stimulation therapy and neurotrophic drugs postoperatively correlated positively with improved functional outcomes. This study suggested a positive effect of the passage of time and nerve transfers in total brachial plexus avulsions from patients' self assessments.

P5-14-22: Prospective Observational Study To Describe the Clinicopathological and Biological Characteristics and the Management of Metastatic Breast Cancer Patients Who Experienced Complete or Partial Remission or Disease Stabilization during at Least 3 Years

Background

Trastuzumab has shown an improvement in survival outcomes among patients with HER2+ metastatic breast cancer (MBC). Identification of pathological, clinical factors and tumor genetic profile that may predict long-term remission has become a key-issue. We aimed to describe the clinicopathological and biological characteristics of MBC patients who experienced complete response (CR), partial response (PR), or stable disease (SD) during at least 3 years and their management in routine clinical practice.

Methods: Multicenter, observational, cross-sectional study. Data were collected from women with HER2+ MBC treated with a trastuzumab-based regimen who maintained a partial or complete remission or disease stabilization beyond 3 years. The interim results from the first 65 patients evaluated are presented.

Results: Median age: 59 (52-70) years. Metastatic disease was diagnosed after a median of 23.5 (1.6−48.8) months since primary tumor diagnosis. The predominant tumor type was ductal carcinoma (89.2%) and 47% showed histological grade III. Mean tumor size: 3.6±2.2cm (anatomical pathology), 5.1±2.8cm (imaging studies). Hormonal status: Progesterone receptor positive 46% and estrogen receptor positive 43%. Most common metastatic sites: lung (23%), liver (17%) and bone (14%). Overexpression of HER2 was assessed by IHC in 97% of patients, of whom 94% were HER2+ (3+) and 17% had FISH+ HER2 status. Tumor was positive for p53 and Ki67 in 23% and 41.5%, respectively. Surgery was performed on 83% of patients, of which 73% underwent radical mastectomy; 96% had their axillary nodes removed. Surgery of metastases was performed on 7.8%. First line chemotherapy was received by 91% with the most frequent schemes being paclitaxel (24%), vinorelbine (15%) and paclitaxel/carboplatine (14%). First line hormonal therapy and radiotherapy was used in 45% and 12%, respectively. All patients received first line trastuzumab, administered on a weekly schedule in 51%. Trastuzumab was used in combination in most of patients (89.2%) with a median number of cycles of 18 (7.0−41.5) and during a median of 53.3±25 months. 66% of patients achieved a CR, 21% PR and 13% had SD. Median time since trastuzumab was initiated to CR, PR or SD was 5 (4-7) months. Median duration of CR, PR or SD was 56 (44.5−78.0) months. Trastuzumab was maintained beyond CR, PR or SD in 99% during a median of 46.5 (35-67) months. 75% of patients continue on treatment with trastuzumab. Only 2 patients discontinued trastuzumab due to toxicity. At the time of the analysis, 19% had progressed, 57% were alive and free of disease and among patients on treatment (93%), 54% were on trastuzumab. Cardiac toxicity was the most common toxicity (36%) among those suffering at least one (22%).

Conclusions: The preliminary findings support that trastuzumab provides a substantial long-term survival benefit with a manageable safety profile in HER2+ MBC patients. This study adds to the evidence that there may be benefit in continuing trastuzumab after achieving remission or disease stabilization. Final results will be presented in the forthcoming congress.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-14-22.

Effects of strontium-doped bioactive glass on the differentiation of cultured osteogenic cells

There is accumulating evidence that strontium-containing biomaterials have positive effects on bone tissue repair. We investigated the in vitro effect of a new Sr-doped bioactive glass manufactured by the sol-gel method on osteoblast viability and differentiation. Osteoblasts isolated from foetal mouse calvaria were cultured in the presence of bioactive glass particles; particles were undoped (B75) or Sr-doped with 1 wt.% (B75-Sr1) and 5 wt.% (B75-Sr5). Morphological analysis was carried out by contrast-phase microscopy and scanning electron microscopy (SEM). Cell viability was evaluated by the MTS assay at 24 h, 48 h and 72 h. At 24 h, day 6 and day 12, osteoblast differentiation was evaluated by assaying alkaline phosphatase (ALP) activity, osteocalcin (OC) secretion and gene expression of various bone markers, using Real-Time-PCR. Alizarin Red staining and ALP histoenzymatic localisation were performed on day 12. Microscopic observations and MTS showed an absence of cytotoxicity in the three investigated bioactive glasses. B75-Sr5 particles in cell cultures, in comparison with those of B75 and B75-Sr1, resulted in a significant up-regulation of Runx2, Osterix, Dlx5, collagen I, ALP, bone sialoprotein (BSP) and OC mRNA levels on day 12, which was associated with an increase of ALP activity on day 6 and OC secretion on day 12. In conclusion, osteoblast differentiation of foetal mouse calvarial cells was enhanced in the presence of bioactive glass particles containing 5 wt.% strontium. Thus, B75-Sr5 may represent a promising bone-grafting material for bone regeneration procedures.

Imaging physicochemical reactions occurring at the pore surface in binary bioactive glass foams by micro ion beam analysis

In this work, the physicochemical reactions occurring at the surface of bioactive sol-gel derived 3D glass scaffolds via a complete PIXE characterization were studied. 3D glass foams in the SiO(2)-CaO system were prepared by sol-gel route. Samples of glass scaffolds were soaked in biological fluids for periods up to 2 days. The surface changes were characterized using particle induced X-ray emission (PIXE) associated to Rutherford backscattering spectroscopy (RBS), which are efficient methods to perform quantitative chemical maps. Elemental maps of major and trace elements at the glass/biological fluids interface were obtained at the micrometer scale for every interaction time. Results revealed interconnected macropores and physicochemical reactions occurring at the surface of pores. The micro-PIXE-RBS characterization of the pores/biological fluids interface shows the glass dissolution and the rapid formation of a Ca rich layer with the presence of phosphorus that came from biological fluids. After 2 days, a calcium phosphate-rich layer containing magnesium is formed at the surface of the glass scaffolds. We demonstrate that quantities of phosphorus provided only by the biological medium have a significant impact on the development and the formation of the phosphocalcic layer.