Micro-hole array sprayer combined with an organic membrane to assist LIBS (MASOM-LIBS): A novel highly sensitive detection method for dissolved trace heavy metals in water.

The development of highly sensitive and rapid detection technology for heavy metal elements in water is of great significance to the monitoring of water environmental pollution, sewage discharge control and other application fields. As an alternative detection method with great potential in the above fields, LIBS technology still has some problems that need to be solved. To improve the sensitivity and efficiency of LIBS detection of trace metals in water, a new method Micro-hole Array Sprayer combined with an Organic Membrane to assist LIBS (MASOM-LIBS) was proposed in this study. In this method, water samples were transformed into a large number of micrometer droplets by a micro-hole array injection device and were sprayed onto a rotating polypropylene organic film. After natural drying, LIBS analysis was performed. The test results of the mixed solution show that plasma with lower electron density and higher electron temperature can be obtained after full drying, the signal intensity will be stronger, and the stability can be reduced to less than 1%. The experimental results of Cu, Cd, Mn, Pb, Cr and Sr as target elements show that the LODs of the MASOM-LIBS method for most elements is less than 0.1 mg/L when the detection time is less than 3 min, which has certain advantages over similar LIBS methods. If the detection time is increased appropriately, the LODs of this method is even expected to be reduced to less than 0.01 mg/L. These results indicate that MASOM-LIBS is a feasible method to improve the sensitivity and speed of the detection of trace heavy elements in liquid samples and can facilitate the wide application of LIBS in water quality monitoring. In view of the short detection time, high sensitivity and low LODs of MASOM-LIBS, this method is expected to be developed into a water trace heavy metal detection technology with fully automatic, real-time, highly sensitive and multi-element detection technology in the future.

Multiplexed target detection using DNA-binding dye chemistry in droplet digital PCR.

Two years ago, we described the first droplet digital PCR (ddPCR) system aimed at empowering all researchers with a tool that removes the substantial uncertainties associated with using the analogue standard, quantitative real-time PCR (qPCR). This system enabled TaqMan hydrolysis probe-based assays for the absolute quantification of nucleic acids. Due to significant advancements in droplet chemistry and buoyed by the multiple benefits associated with dye-based target detection, we have created a "second generation" ddPCR system compatible with both TaqMan-probe and DNA-binding dye detection chemistries. Herein, we describe the operating characteristics of DNA-binding dye based ddPCR and offer a side-by-side comparison to TaqMan probe detection. By partitioning each sample prior to thermal cycling, we demonstrate that it is now possible to use a DNA-binding dye for the quantification of multiple target species from a single reaction. The increased resolution associated with partitioning also made it possible to visualize and account for signals arising from nonspecific amplification products. We expect that the ability to combine the precision of ddPCR with both DNA-binding dye and TaqMan probe detection chemistries will further enable the research community to answer complex and diverse genetic questions.

DSPP effects on in vivo bone mineralization.

Dentin sialophosphoprotein has been implicated in the mineralization process based on the defective dentin formation in Dspp null mice (Dspp-/-). Dspp is expressed at low levels in bone and Dspp-/- femurs assessed by quantitative micro-computed tomography (micro-CT) and Fourier transform infrared spectroscopic imaging (FTIRI) exhibit some mineral and matrix property differences from wildtype femurs in both developing and mature mice. Compared to wildtype, Dspp-/- mice initially (5 weeks) and at 7 months had significantly higher trabecular bone volume fractions and lower trabecular separation, while at 9 months, bone volume fraction and trabecular number were lower. Cortical bone mineral density, area, and moments of inertia in Dspp-/- were reduced at 9 months. By FTIRI, Dspp-/- animals initially (5 months) contained more stoichiometric bone apatite with higher crystallinity (crystal size/perfection) and lower carbonate substitution. This difference progressively reversed with age (significantly decreased crystallinity and increased acid phosphate content in Dspp-/- cortical bone by 9 months of age). Mineral density as determined in 3D micro-CT and mineral-to-matrix ratios as determined by 2D FTIRI in individual cortical and trabecular bones were correlated (r(2)=0.6, p<0.04). From the matrix analysis, the collagen maturity of both cortical and trabecular bones was greater in Dspp-/- than controls at 5 weeks; by 9 months this difference in cross-linking pattern did not exist. Variations in mineral and matrix properties observed at different ages are attributable, in part, to the ability of the Dspp gene products to regulate both initial mineralization and remodeling, implying an effect of Dspp on bone turnover.

DMP1 depletion decreases bone mineralization in vivo: an FTIR imaging analysis.

UNLABELLED: The role of DMP1 in mineralization was analyzed by comparing bone mineral and matrix properties in dmp1-null female mice to heterozygous and wildtype controls by FTIR imaging spectroscopy. The observed decreased mineral content in dmp1 null mice indicates a key role for dmp1 in bone mineralization. Indirect effects of DMP1 on other systems also determine the KO phenotype. INTRODUCTION: Dentin matrix protein 1 (DMP1), an acidic phosphorylated extracellular matrix protein, is highly expressed in mineralized tissues. In vitro, DMP1 peptides can promote or inhibit mineralization depending on the extent of phosphorylation, the peptide size, and concentration. To clarify the biological function of DMP1 protein on in vivo mineralization, this study analyzed bone properties of dmp1 knockout (KO) mice compared with heterozygous (HET) and wildtype (WT) controls. MATERIALS AND METHODS: Tibias from dmp1 KO and age-, sex-, and background-matched HET and WT mice at 4 and 16 weeks (N(total) = 60) were examined by Fourier transform infrared imaging (FTIRI), histology (n = 6 per genotype and age; N = 36), and geometry by muCT (n = 4 per genotype and age; N = 24). Serum ionic calcium and phosphate concentrations were also determined. RESULTS: The mineral-to-matrix ratios (spectroscopic parameter of relative mineral content) were significantly lower in dmp1 KO mice tibias compared with WT and HET at 4 and 16 weeks. The mineral crystallinity (crystal size/perfection) was significantly increased in dmp1 KO and HET mice relative to WT. Collagen cross-link ratios (a spectroscopic parameter related to the relative amounts of nonreducible/reducible collagen cross-links) in dmp1 KO were not significantly different from WT and HET. Based on muCT, cortical bone cross-sectional areas at 16 but not 4 weeks were significantly reduced in the KO compared with controls. Maximum, minimum, and polar cross-sectional moments of inertia were significantly lower in dmp1 KO than in HET at 16 weeks but not at 4 weeks. Histological analysis and muCT 3-D images suggested that dmp1 KO mice had osteomalacia. Dmp1 KO mice had significantly lower ionic calcium and phosphate concentrations relative to WT, whereas in the HET, values for phosphate were equivalent, and calcium values were decreased relative to WT values. CONCLUSIONS: The findings of decreased mineral-to-matrix ratio and increased crystal size in bones of dmp1 KO mice suggest that DMP1 has multiple roles (both direct and indirect) in the regulation of postnatal mineralization. We suggest that direct effects on mineral formation, crystal growth, and indirect effects on regulation of Ca x P concentrations and matrix turnover all contribute to the dominant phenotype in the dmp1 KO mouse.