Methyl methacrylate used in bone cements has drawbacks of toxicity, high exotherm, and considerable shrinkage. A new resin, based on silorane/oxirane chemistry, has been shown to have little toxicity, low exotherm, and low shrinkage. We hypothesized that silorane-based resins may also be useful as components of bone cements as well as other bone applications and began testing on bone cell function in vitro and in vivo. MLO-A5, late osteoblast cells, were exposed to polymerized silorane (SilMix) resin (and a standard polymerized bisGMA/TEGDMA methacrylate (BT) resin and compared to culture wells without resins as control. A significant cytotoxic effect was observed with the BT resin resulting in no cell growth, whereas in contrast, SilMix resin had no toxic effects on MLO-A5 cell proliferation, differentiation, nor mineralization. The cells cultured with SilMix produced increasing amounts of alkaline phosphatase (1.8-fold) compared to control cultures. Compared to control cultures, an actual enhancement of mineralization was observed in the silorane resin-containing cultures at days 10 and 11 as determined by von Kossa (1.8–2.0 fold increase) and Alizarin red staining (1.8-fold increase). A normal bone calcium/phosphate atomic ratio was observed by elemental analysis along with normal collagen formation. When used in vivo to stabilize osteotomies, no inflammatory response was observed, and the bone continued to heal. In conclusion, the silorane resin, SilMix, was shown to not only be non cytototoxic, but actually supported bone cell function. Therefore, this resin has significant potential for the development of a nontoxic bone cement or bone stabilizer.

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Carbon‐based nanoparticles have promising applications in nanomedicine, electronics and drug delivery. However, lung toxicity studies in rodents continue to reflect tissue effects. Our in vivo studies with single wall carbon nanotubes (SWCNT) administered intratracheally in pulmonary surfactant (50 mg in 50 microliters i.t.) produced a rapid pulmonary eosinophilia and airway mucin upregulation within minutes. Nanotube clusters produced pulmonary tissue granulomas within 1 week, at which time mucin‐laden macrophages, some with nanoparticle fibers, traveled to the mesothelial space and the draining lymph nodes. The responses of the SWCNT‐treated rat airway and mesothelium was of interest given the known response of human mesothelium to fibers such as asbestos. Toxicity of SWCNT on Met‐5A human mesothelial cells was investigated in vitro. Viability was evaluated in the presence and absence of surfactant with increasing doses of SWCNT. Cell toxicity, evaluated by WST‐1 assay showed TC50 of 63 μg/mL without and 70 μg/mL with 20% surfactant in the culture medium, a nonsignificant difference. Transmission electron microscopy on mesothelial cells treated with SWCNT showed intracellular nanotube clusters indenting the nuclear membrane with projecting fibers. These data suggested that the SWCNT‐induced rapid eosinophilia might be triggered by such damage, through cellular release of endogenous signals. Our early efforts with nuclear protein HMGB1 in tissue suggests that the SWCNT are responsible for a "DAMP‐type" trigger of eosinophilia in vivo in the rat model. TEM efforts with pleural fluid and nodes continue to trace the path of the SWCNT in the pulmonary‐ mesothelial interface.

An initial effect of carbon nanoparticle (CN) lung exposure is the cellular release of damage‐associated molecular pattern recognition molecules (DAMPs). One of the earliest is the high mobility group box 1 (HMGB1) protein, which, extracellularly, exerts its actions as a ligand for pattern recognition receptor (PRR) target cell activation. This work studies HMGB1's role in damage recognition and activation of cellular processes. CN (0.025 mg, endotoxin free in 0.050 mL Survanta) was intratracheally instilled into rat airways (n=45). At necropsy 0.5hr to 4 wks later, bronchoalveolar lavage fluid (BAL), lungs and sera were measured (ELISA, cytology) for HMGB1 and 3 cytokines. BALs were also used to activate PRRs in RAW Blue cells, stably transfected lung macrophages expressing the SEAP gene inducible by NF‐kB and AP‐1. HMGB1‐containing BALs induced significant expression of SEAP in the RAW blue cells, highest at 24 hr, which was compared to purified HMGB1 dose‐dependent activation. Histopathology described Inflammation of lung parenchyma and translocation of CN from airways to the mesothelial lining. IL‐10 and IL‐6 in lung related in timing to HMGB1‐receptor complexes (p=0.04). The results show that sterile CN exposure releases lung cell HMGB1, and BAL from this exposure activates raw blue cells at times when HMGB1 is elevated, with related receptors and cytokines.Sponsor: Saint Luke's Hospital Foundation