Micro-Raman imaging of the bone development in chick embryos exposed to 1.0 ppm sublethal doses of platinum group metals

Abstract

<p>Platinum group metals (PGMs) including platinum (Pt), rhodium (Rh), and palladium (Pd) occur naturally and anthropogenically. They are found at pollutant levels in the environment and bioaccumulate in plant and animal tissues. Our previous studies showed that chick embryos exposed to PGMs concentrations of 5.0 ppm (LD50) and higher presented skeletal deformities. The goal of this study was to determine the toxic effects of sublethal doses of PGMs on developing chick embryo tibiotarsi using micro-Raman spectroscopy. Chick embryos (ten per treatment) were injected with 1.0 mL aqueous salt solutions of 1 ppm Pd(II), Pt(IV), Rh(lIl) and a PGM mixture on the 7th and 14th day of incubation. Controls groups of no injection and saline solution injections were also included. The chick embryos were sacrificed on the 20th day. Tibiotarsi were harvested, cross-sectioned, fixed and embedded in paraffin. Hyperspectral Raman data were collected across tibiotarsi and analyzed using in-house written codes within MatLab v. 7.11.0. Raman maps were created using the baseline-corrected intensity of the Vl(PO₄^3-) stretching of hydroxyapatite (Ca₁₀(PO₄)₆-0H₂). All treatments showed abnormal changes in the phosphate content of periosteum. Significant changes in the average mineralization age of tibiotarsi (integrated area ratio OfVl(CO/VV1(POllwere found in the Pt, Pd, and PGM treatments when compared to control (one-way ANOVA, p~O.OOl). The average mineralization age was: 0.0548±0.0342, 0.0593±0.0446, 0.0892±0.0779, 0.0725±0.0543, 0.1005±0.0661 and 0.1042±0.0707 for the Pd, Pt, Rh, PGM mixture, no injection and saline solution samples, respectively. Raman imaging revealed anomalous calcium inclusions within the bone marrow for the PGM mixture treatment. These highly calcified regions inhibit the transport of nutrients and waste through the cartilage matrix and cause blockages of the vasculature system during the pre-hatching phase. Overall, micro-Raman data showed that the calcium metabolism is negatively impacted by the exposure to 1.0 ppm of PGMs.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 8, 2011</p>