Bioactivity in silica/poly(γ-glutamic acid) sol–gel hybrids through calcium chelation

Bioactive glasses and inorganic/organic hybrids have great potential as biomedical implant materials. Sol–gel hybrids with interpenetrating networks of silica and biodegradable polymers can combine the bioactive properties of a glass with the toughness of a polymer. However, traditional calcium sources such as calcium nitrate and calcium chloride are unsuitable for hybrids. In this study calcium was incorporated by chelation to the polymer component. The calcium salt form of poly(γ-glutamic acid) (γCaPGA) was synthesized for use as both a calcium source and as the biodegradable toughening component of the hybrids. Hybrids of 40 wt.% γCaPGA were successfully formed and had fine scale integration of Ca and Si ions, according to secondary ion mass spectrometry imaging, indicating a homogeneous distribution of organic and inorganic components. 29Si magic angle spinning nuclear magnetic resonance data demonstrated that the network connectivity was unaltered with changing polymer molecular weight, as there was no perturbation to the overall Si speciation and silica network formation. Upon immersion in simulated body fluid a hydroxycarbonate apatite surface layer formed on the hybrids within 1 week. The polymer molecular weight (Mw 30–120 kDa) affected the mechanical properties of the resulting hybrids, but all hybrids had large strains to failure, >26%, and compressive strengths, in excess of 300 MPa. The large strain to failure values showed that γCaPGA hybrids exhibited non-brittle behaviour whilst also incorporating calcium. Thus calcium incorporation by chelation to the polymer component is justified as a novel approach in hybrids for biomedical materials

A unified in vitro evaluation for apatite-forming ability of bioactive glasses and their variants

The aim of this study was to propose and validate a new unified method for testing dissolution rates of bioactive glasses and their variants, and the formation of calcium phosphate layer formation on their surface, which is an indicator of bioactivity. At present, comparison in the literature is difficult as many groups use different testing protocols. An ISO standard covers the use of simulated body fluid on standard shape materials but it does not take into account that bioactive glasses can have very different specific surface areas, as for glass powders. Validation of the proposed modified test was through round robin testing and comparison to the ISO standard where appropriate. The proposed test uses fixed mass per solution volume ratio and agitated solution. The round robin study showed differences in hydroxyapatite nucleation on glasses of different composition and between glasses of the same composition but different particle size. The results were reproducible between research facilities. Researchers should use this method when testing new glasses, or their variants, to enable comparison between the literature in the future

High power targets for cyclotron production of 99mTc‡

Introduction Technetium-99m, supplied in the form of 99Mo/99mTc generators, is the most widely used radioisotope for nuclear medical imaging. The parent isotope 99Mo is currently produced in nuclear reactors. Recent disruptions in the 99Mo supply chain [1] prompted the development of methods for the direct accelerator-based production of 99mTc. Our approach involves the 100Mo(p,2n)99mTc reaction on isotopically enriched molybdenum using small medical cyclotrons (Ep ≤ 20 MeV), which is a viable method for the production of clinically useful quantities of 99mTc [2]. Multi-Curie production of 99mTc requires a 100Mo target capable of dissipating high beam intensities [3]. We have reported the fabrication of 100Mo targets of both small and large area tar-gets by electrophoretic deposition and subsequent sintering [4]. As part of our efforts to further enhance the performance of molybdenum targets at high beam currents, we have developed a novel target system (initially de-signed for the GE PETtrace cyclotron) based on a pressed and sintered 100Mo plate brazed onto a dispersion-strengthened copper backing. Materials and Methods In the first step, a molybdenum plate is produced similarly to the method described in [5] by compacting approximately 1.5 g of commercially available 100Mo powder using a cylindrical tool of 20 mm diameter. A pressure between 25 kN/cm2 and 250 kN/cm2 is applied by means of a hydraulic press. The pressed molybdenum plate is then sintered in a reducing atmosphere (Ar/2% H2) at 1,700 oC for five hours. The resulting 100Mo plates have about 90–95 % of the molybdenum bulk density. The 100Mo plate is furnace brazed at ~750 oC onto a backing manufactured from a disperse on strengthened copper composite (e.g. Glidcop AL-15) using a high temperature silver-copper brazing filler. This process yields a unique, mechanically and thermally robust target system for high beam power irradiation. Irradiations were performed on the GE PETtrace cyclotrons at LHRI and CPDC with 16.5 MeV protons and beam currents ≥ 100 µA. Targets were visually inspected after a 6 hour, 130 µA bombardment (2.73 kW/cm2, average) and were found fully intact. Up to 4.7 Ci of 99mTc have been produced to date. The saturated production yield remained constant between 2 hour and 6 hour irradiations. Results and Conclusion These results demonstrate that our brazed tar-get assembly can withstand high beam intensities for long irradiations without deterioration. Efforts are currently underway to determine maximum performance parameters

Combining Optimization and Randomization Approaches for the Design of Clinical Trials

t Intentional sampling methods are non-randomized procedures that select a group of individuals for a sample with the purpose of meeting specific prescribed criteria. In this paper we extend previous works related to intentional sampling, and address the problem of sequential allocation for clinical trials with few patients. Roughly speaking, patients are enrolled sequentially, according to the order in which they start the treatment at the clinic or hospital. The allocation problem consists in assigning each new patient to one, and only one, of the alternative treatment arms. The main requisite is that the profiles in the alternative arms remain similar with respect to some relevant patients’ attributes (age, gender, disease, symptom severity and others). We perform numerical experiments based on a real case study and discuss how to conveniently set up perturbation parameters, in order to yield a suitable balance between optimality – the similarity among the relative frequencies of patients in the several categories for both arms, and decoupling – the absence of a tendency to allocate each pair of patients consistently to the same arm

Gender differences and access to a sports dietitian influence dietary habits of collegiate athletes

BACKGROUND: Limited research exists on the effect of a sports dietitian (SD) on athletes’ dietary habits and nutrient periodization, which is the deliberate manipulation of macronutrient intake to match training goals. Further, the difference in dietary habits between men and women collegiate athletes has been understudied. A survey questionnaire examining dietary habits and practices was administered to athletes at two universities that employed a full time SD. Not all athletes used the SD as their primary source for nutritional guidance. The purposes were to examine the effect of a SD as a primary source of nutrition information, and the effect of gender on dietary habits in collegiate athletes. METHODS: Three hundred eighty-three women (n = 240) and men (n = 143) student-athletes (mean ± SD: age = 19.7 ± 1.4 years) from 10 collegiate sports took a 15-min survey consisting of questions on dietary habits and practices. Topics queried included eating habits, breakfast habits, hydration habits, nutritional supplementation use, pre-workout nutrition, post-workout nutrition, nutrition during team trips, and nutrient timing. Data were sorted by the athlete’s source of nutritional information (i.e., sport dietitian, other). Data analysis consisted of descriptive statistics and 2-way Pearson X(2) analyses (p ≤ 0.10). RESULTS: When a SD was indicated as the primary nutrition information source, athletes appeared to have a greater understanding of nutrient periodization (47.12 % vs. 32.85 %), were more likely to have school-provided boxed meals while on team trips (21.29 % vs. 6.77 %), and also less likely to consume fast food while on team trips (9.90 % vs. 19.55 %). Men athletes consumed fast food or restaurant meals more frequently, had higher weekly and more frequent alcohol intake during the competitive season. Women athletes were more likely to prepare meals, eat breakfast 7 days a week, and have school-provided boxed meals. CONCLUSIONS: Positive effects on dietary habits were observed when a SD was the primary nutrition information source. Practitioners should be aware of the gender differences in alcohol intake, fast food consumption, and knowledge of nutrient periodization. Collegiate athletes and athletic staff members could benefit from SD access to safeguard against dietary habits detrimental to performance

Tailoring the nanoporosity of sol-gel derived bioactive glass using trimethylethoxysilane

Sol-gel derived bioactive glasses are thought to have high potential as materials for bone regeneration and drug delivery devices. They bond to bone and have a controllable degradation rate. Their unique nanoporosity provides high surface area and exposes a high concentration of surface hydroxyl groups. Protein adsorption, degradation rate and cellular response are known to be affected by nanotopography, therefore it is important to be able to produce glasses with a range of pore sizes. In this study, the modal nanopore diameters of glasses with the bioactive composition 70 mol% SiO2 and 30 mol% CaO (70S30C) were successfully increased from 12 to 30 nm by adding specific amounts of trimethylethoxysilane (TMES) during the sol-gel process. The mechanism of the nanoporosity modification was studied with transmission electron microscopy (TEM), nitrogen sorption and Si-29 magic angle spinning (MAS) solid-state NMR spectroscopy. Solid-state NMR was used to investigate how the modification processes affected the atomic scale structure of the glass, such as Q structure and network connectivity, which was related to the changes in nanostructure using combinations of nitrogen sorption and TEM. The TMES was found to inhibit the fusion of the nanoparticle structural components of the glasses, causing an increase in pore size

Role of pH and temperature on silica network formation and calcium incorporation into sol–gel derived bioactive glasses

Bioactive glasses and inorganic/organic hybrids have great potential as implant materials. Bioactive glasses can bond to bone through the formation of a bone-like hydroxycarbonate apatite (HCA) layer and stimulate bone growth via their dissolution products. The brittle nature of these glasses can be combined with the toughness of a biodegradable polymer by forming a hybrid through the sol–gel process. However, for polymer incorporation, lower temperatures and milder pH conditions are required rather than the current method which uses pH 2 were mesoporous. This indicates a difference in gel formation about the isoelectric point of silicic acid, which was confirmed by 29Si solid state NMR. When immersed in simulated body fluid (SBF), the glasses stabilised at 600 °C were more porous, yet had a slower ion release rate than the gels dried at 40 °C. All gels and glasses formed an HCA layer in SBF; however, calcium was only incorporated into the silica network after stabilisation at 600 °C and thus a new way of incorporating calcium at low temperatures must still be found. This work is an important foundation for hybrid synthesis as raising the pH of the sol–gel process from pH < 1 to pH 5.5 was found to have no adverse effects on silica network formation and thus polymer can be incorporated into the sol–gel process at milder pH conditions without the concern of acid catalysed polymer degradation by chain scission