Timothy J. Keenan

Silver Nanoparticle Coated Bioactive Glasses – Composites with Dex/CMC Hydrogels: Characterization, Solubility, and In Vitro Biological Studies

Silver (Ag) coated bioactive glass particles (Ag-BG) were formulated and compared to uncoated controls (BG) in relation to glass characterization, solubility and microbiology. X-ray diffraction (XRD) confirmed a crystalline AgNP surface coating while ion release studies determined low Ag release (<2 mg/L). Cell culture studies presented increased cell viability (127 and 102%) with lower liquid extract (50 and 100 ml/ml) concentrations. Antibacterial testing of Ag-BG in E. coli, S. epidermidis and S. aureus significantly reduced bacterial cell viability by 60-90%. Composites of Ag-BG/CMC-Dex Hydrogels were formulated and characterized. Agar diffusion testing was conducted where Ag-BG/hydrogel composites produced the largest inhibition zones of 7 mm (E. coli), 5 mm (S. aureus) and 4 mm (S. epidermidis).

Investigating the effect of TiO2 on the structure and biocompatibility of bioactive glass

Titanium (Ti4+ ) containing materials have been widely used in medical applications due to its associated bioactivity in vivo. This study investigates the replacement of Si4+ with Ti4+ within the system SiO2 -Na2 O-CaO-P2 O5 to determine its influence on glass structure. This strategy was conducted in order to control the glass solubility to further improve the cellular response. Ti4+ incorporation was found to have little influence on the glass transition temperature (Tg  = 520 ± 8°C) and magic angle spinning-nuclear magnetic resonance (MAS-NMR) shifts (-80 ppm) up to additions of 18 wt %. However, at 30 wt % the Tg increased to 600°C and MAS-NMR spectra shifted to -88 ppm. There was also an associated reduction in glass solubility as a function of Ti4+ incorporation as determined by inductively coupled plasma optical emission spectroscopy where Si4+ (1649-44 mg/L) and Na+ (892-36 mg/L) levels greatly reduced while Ca2+ (3-5 mg/L) and PO43- (2-7 mg/L) levels remained relatively unchanged. MC3T3 osteoblasts were used for cell culture testing and it was determined that the Ti4+ glasses increased cell viability and also facilitated greater osteoblast adhesion and proliferation to the glass surface compared to the control glass.

Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics

The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces.

Synthesis, characterization, and in vitro cytocompatibility of Ga-bioactive glass/polymer hydrogel composites:

A bioactive glass series (0.42SiO2-0.10Na2O-0.08CaO-(0.40–x)ZnO-(x)Ga2O3) was incorporated in carboxymethyl cellulose–dextran hydrogels at three different loadings (0.05, 0.10, and 0.25 m2), and the resulting composites were characterized using scanning electron microscopy, physical swelling characteristics, and inductively coupled plasma optical emission spectroscopy. In vitro cytocompatibility was also evaluated for composite extracts in contact with L-929 mouse fibroblasts and MC3T3-E1 human osteoblasts. Scanning electron microscopy confirmed that glass particles were distributed throughout the hydrogels, and swelling studies showed that glass presence can increase the amount of fluid that can be absorbed by the hydrogels after seven days of immersion in phosphate-buffered saline by up to 180%. Several trends were observed in the inductively coupled plasma optical emission spectroscopy data, with the most important being the release of Ga3+ from both Ga-containing glasses at all three loadings, with a maximum of 4.7 mg/L released after 30 days of incubation in phosphate-buffered saline. Cell viability analysis suggested that most composite extracts did not decrease neither fibroblast nor osteoblast viability. These results indicate that it is possible to embed bioactive glass particles into carboxymethyl cellulose–dextran hydrogels, and upon submersion in aqueous media, release ions from the glass particles that may elicit therapeutic effects.

Structural characterization and anti-cancerous potential of gallium bioactive glass/hydrogel composites

A bioactive glass series (0.42SiO2-0.10Na2O-0.08CaO-(0.40-X)ZnO-(X)Ga2O3) was incorporated into carboxymethyl cellulose (CMC)/dextran (Dex) hydrogels in three different amounts (0.05, 0.10, and 0.25m(2)), and the resulting composites were characterized using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and (13)C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS-NMR). Composite extracts were also evaluated in vitro against MG-63 osteosarcoma cells. TEM confirmed glass distribution throughout the composites, although some particle agglomeration was observed. DSC revealed that glass composition and content did have small effects on both Tg and Tm. MAS-NMR revealed that both CMC and Dex were successfully functionalized, that cross-linking occurred, and that glass addition did slightly alter bonding environments. Cell viability analysis suggested that extracts of the glass and composites with the largest Ga-content significantly decreased MG-63 osteosarcoma viability after 30days. This study successfully characterized this composite series, and demonstrated their potential for anti-cancerous applications.

Characterization of Y 2 O 3 and CeO 2 doped SiO 2 -SrO-Na 2 O glasses

Abstract The structural effects of yttrium (Y) and cerium (Ce) are investigated when substituted for sodium (Na) in a 0.52SiO2–0.24SrO–(0.24−x)Na2O–xMO (where x = 0.08; MO = Y2O3 and CeO2) glass series. Network connectivity (NC) was calculated assuming both Y and Ce can act as a network modifier (NC = 2.2) or as a network former (NC up to 2.9). Thermal analysis showed an increase in glass transition temperature (Tg) with increasing Y and Ce content, Y causing the greater increase from the control (Con) at 493∘C to 8 mol% Y (HY) at 660∘C. Vickers hardness (HV) was not significantly different between glasses. 29Si Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) did not show peak shift with addition of Y, however Ce produced peak broadening and a negative shift in ppm. The addition of 4 mol% Ce in the YCe and LCe glasses shifted the peak from Con at −81.3 ppm to −82.8 ppm and −82.7 ppm respectively; while the HCe glass produced a much broader peak and a shift to −84.8 ppm. High resolution X-ray Photoelectron Spectroscopy for the O 1s spectral line showed the ratio of bridging (BO) to non-bridging oxygens (NBO), BO:NBO,was altered,where Con had a ratio of 0.7, HY decreased to 0.4 and HCe to 0.5.

Fill Volume as an Indicator of Surface Heterogeneity in Glass Vials for Parenteral Packaging

The chemical durability of glass vials for parenteral packaging is typically assessed by completely filling the vial with a medium of interest. This testing approach can mask the heterogeneous dissolution behavior of vials produced by conversion of glass tubing. In this study, the corrosion behavior of vials provided by four suppliers was evaluated as a function of fill volume. Vials were filled with incrementally increasing volumes of water for injection (WFI) up to near-maximum capacity and then autoclaved. The pH and levels of extracted ions were measured. The pH of autoclaved WFI generally increased for low fill volumes relative to pure WFI, presumably because of extraction of alkali from the heel region. The pH was found to generally decrease with increasing fill volume as the concentration of extractables was diluted. Analysis of dissolution profiles supports the altered surface chemistry of the heel region relative to the body. The results of this study demonstrate the potential limitations of conventional hydrolytic resistance tests and the susceptibility of the heel region to aqueous corrosion.

Investigating the Effect of Glass Ion Release on the Cytocompatibility, Antibacterial Eflcacy and Antioxidant Activity of Y2O3 / CeO2 doped SiO2-SrO-Na2O glasses

Abstract The effect on ion release and cytocompatibility of Yttrium (Y) and Cerium (Ce) are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-Na2OMOglass series (where MO= Y2O3 or CeO2). Glass leaching was evaluated through pH measurements and Inductive Coupled Plasma-Optical Emission Spectrometry (ICP-OES) analysiswhere the extract pH increased during incubation (11.2 - 12.5). Ion release of Silicon (Si), Na and Strontium (Sr) from the Con glass was at higher than that of glasses containing Y or Ce, and reached a limit after 1 day. Ion release from Y and Ce containing glasses reached a maximum of 1800 μg/mL, 1800 μg/mL, and 10 μg/mL for Si, Na, and Sr, respectively. Release of Y and Cewas below the ICP- OES detection limit <0.1 μg/mL. Cell viability of both L929 fibroblasts and MC3T3 osteoblasts decreased for Con, LY, and LCe extracts; HY extracts did not significantly decrease cell viability while YCe and HCe saw concentrationdependent viability decrease (20%, 33% extract concentrations). Bacterial studies saw Con and LCe eliminating >75% of bacteria at a 9% extract concentration. Antioxidant capacity (mechanism for neuroprotection) was evaluated using the ABTS assay. All glasses had inherent radical oxygen species (ROS) scavenging capability with Con reaching 9.5 mMTE.

Ga-containing bioactive glass/Dextran-CMC hydrogel composites: Ion release and cell viability

This study aims to investigate the solubility of composites comprised of a degradable polymeric hydrogel and particles of a Ga-containing glass series, and relate this solubility information to the viability of MC-3T3 osteoblasts. Composites released a maximum of 4.7 mg/L of Ga after 30 days, and these extracts did not inhibit osteoblast viability.

Dextran-based hydrogels for in-situ delivery of gallium-containing bioactive glasses

The overall goal of this project is to synthesize a degradable polymer hydrogel, which has the ability to act as a scaffold upon which therapeutic materials, particularly, Ga-containing bioactive glasses, can be seeded, while also allowing the ionic dissolution products of the glasses to interact with host tissues and fluids within the local environment.