Nucleated red blood cells as a biomarker for mortality in neonates following cardiac surgery.

INTRODUCTION: Nucleated red blood cells (NRBCs) are immature red cells that under normal conditions are not present in the peripheral circulation. Several studies have suggested an association between elevated NRBC and poor outcome in critically ill adults and neonates. We sought to determine if elevations in NRBC value following cardiac surgery and following clinical events during the hospital stay can be used as a biomarker to monitor for mortality risk in neonates post-cardiac surgery. MATERIALS AND METHODS: We constructed a retrospective study of 264 neonates who underwent cardiac surgery at Children's Hospital, New Orleans between 2011 and 2020. Variables included mortality and NRBC value were recorded following cardiac surgery and following peri-operative clinical events. The study was approved by LSU Health IRB. Sensitivity, specificity, receiver operating characteristic (ROC) curves with area under the curve (AUC) and logistic regression analysis were performed. RESULTS: Thirty-six patients (13.6%) died, of which 32 had an NRBC value ≥10/100 white blood cell (WBC) during hospitalisation. Multi-variable analysis found extracorporeal membrane oxygenation use (OR 10, 95% CI 2.9-33, p=<0.001), NRBC ≥10/100 WBC (OR 16.1, CI 4.1-62.5, p ≤ 0.001) and peak NRBC in the 14-day period post-cardiac surgery (continuous variable, OR 1.05, 95% CI 1.0-1.09, p = 0.03), to be independently associated with mortality. Using a cut-off NRBC value of 10/100 WBC, there was an 88.9% sensitivity and a 90.8% specificity, with ROC curve showing an AUC of 0.9 and 0.914 for peak NRBC value in 14 days post-surgery and entire hospitalisation, respectively. CONCLUSIONS: NRBC ≥10/100 WBC post-cardiac surgery is strongly associated with mortality. Additionally, NRBC trend appears to show promise as an accurate biomarker for mortality.

Polysaccharide-based liquid storage and transport media for non-refrigerated preservation of bacterial pathogens.

The preservation of biological samples for an extended time period of days to weeks after initial collection is important for the identification, screening, and characterization of bacterial pathogens. Traditionally, preservation relies on cold-chain infrastructure; however, in many situations this is impractical or not possible. Thus, our goal was to develop alternative bacterial sample preservation and transport media that are effective without refrigeration or external instrumentation. The viability, nucleic acid stability, and protein stability of Bacillus anthracis Sterne 34F2, Francisella novicida U112, Staphylococcus aureus ATCC 43300, and Yersinia pestis KIM D27 (pgm-) was assessed for up to 28 days. Xanthan gum (XG) prepared in PBS with L-cysteine maintained more viable F. novicida U112 cells at elevated temperature (40°C) compared to commercial reagents and buffers. Viability was maintained for all four bacteria in XG with 0.9 mM L-cysteine across a temperature range of 22-40°C. Interestingly, increasing the concentration to 9 mM L-cysteine resulted in the rapid death of S. aureus. This could be advantageous when collecting samples in the built environment where there is the potential for Staphylococcus collection and stabilization rather than other organisms of interest. F. novicida and S. aureus DNA were stable for up to 45 days upon storage at 22°C or 40°C, and direct analysis by real-time qPCR, without DNA extraction, was possible in the XG formulations. XG was not compatible with proteomic analysis via LC-MS/MS due to the high amount of residual Xanthomonas campestris proteins present in XG. Our results demonstrate that polysaccharide-based formulations, specifically XG with L-cysteine, maintain bacterial viability and nucleic acid integrity for an array of both Gram-negative and Gram-positive bacteria across ambient and elevated temperatures.

Magnetic iron oxide and manganese-doped iron oxide nanoparticles for the collection of alpha-emitting radionuclides from aqueous solutions.

Magnetic nanoparticles are well known to possess chemically active surfaces and large surface areas that can be employed to extract a range of ions from aqueous solutions. Additionally, their superparamagnetic properties provide a convenient means for bulk collection of the material from solution after the targeted ions have been adsorbed. Herein, two nanoscale amphoteric metal oxides, each possessing useful magnetic attributes, were evaluated for their ability to collect trace levels of a chemically diverse range of alpha emitting radioactive isotopes (polonium (Po), radium (Ra), uranium (U), and americium (Am)) from a wide range of aqueous solutions. The nanomaterials include commercially available magnetite (Fe3O4) and magnetite modified to incorporate manganese (Mn) into the crystal structure. The chemical stability of these nanomaterials was evaluated in Hanford Site, WA ground water between the natural pH (~8) and pH 1. Whereas the magnetite was observed to have good stability over the pH range, the Mn-doped material was observed to leach Mn at low pH. The materials were evaluated in parallel to characterize their uptake performance of the alpha-emitting radionuclide spikes from ground water across a range of pH (from ~8 down to 2). In addition, radiotracer uptake experiments were performed on Columbia River water, seawater, and human urine at their natural pH and at pH 2. Despite the observed leaching of Mn from the Mn-doped nanomaterial in the lower pH range, it exhibited generally superior analyte extraction performance compared to the magnetite, and analyte uptake was observed across a broader pH range. We show that the uptake behavior of the various radiotracers on these two materials at different pH levels can generally be explained by the amphoteric nature of the nanoparticle surfaces. Finally, the rate of sorption of the radiotracers on the two materials in unacidified ground water was evaluated. The uptake curves generally indicate that equilibrium is obtained within a few minutes, which is attributed to the high surface areas of the nanomaterials and the high level of dispersion in the liquids. Overall, the results indicate that these nanomaterials may have the potential to be employed for a range of applications to extract radionuclides from aqueous solutions.

Manganese doping of magnetic iron oxide nanoparticles: tailoring surface reactivity for a regenerable heavy metal sorbent.

A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load ~1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.

Investigation of magnetic nanoparticles for the rapid extraction and assay of alpha-emitting radionuclides from urine: demonstration of a novel radiobioassay method.

In the event of an accidental or intentional release of radionuclides into a populated area, massive numbers of people may require radiobioassay screening as triage for dose-reduction therapy or identification for longer-term follow-up. If the event released significant levels of beta- or alpha-emitting radionuclides, in vivo assays would be ineffective. Therefore, highly efficient and rapid analytical methods for radionuclide detection from submitted spot urine samples (≤50 mL) would be required. At present, the quantitative determination of alpha-emitting radionuclides from urine samples is highly labor intensive and requires significant time to prepare and analyze samples. Sorbent materials that provide effective collection and enable rapid assay could significantly streamline the radioanalytical process. The authors have demonstrated the use of magnetic nanoparticles as a novel method of extracting media for four alpha-emitting radionuclides of concern (polonium, radium, uranium and americium) from chemically-unmodified and pH-2 human urine. Herein, the initial experimental sorption results are presented along with a novel method that uses magnetic nanoparticles to extract radionuclides from unmodified human urine and then collect the magnetic field-induced particles for subsequent alpha-counting-source preparation. Additionally, a versatile human dose model is constructed that determines the detector count times required to estimate dose at specific protective-action thresholds. The model provides a means to assess a method's detection capabilities and uses fundamental health physics parameters and actual experimental data as core variables. The modeling shows that, with effective sorbent materials, rapid screening for alpha-emitters is possible with a 50-mL urine sample collected within 1 wk of exposure/intake.

Thiol-ene induced diphosphonic acid functionalization of superparamagnetic iron oxide nanoparticles.

Multifunctional organic molecules represent an interesting challenge for nanoparticle functionalization due to the potential for undesirable interactions between the substrate material and the variable functionalities, making it difficult to control the final orientation of the ligand. In the present study, UV-induced thiol-ene click chemistry has been utilized as a means of directed functionalization of bifunctional ligands on an iron oxide nanoparticle surface. Allyl diphosphonic acid ligand was covalently deposited on the surface of thiol-presenting iron oxide nanoparticles via the formation of a UV-induced thioether. This method of thiol-ene click chemistry offers a set of reaction conditions capable of controlling the ligand deposition and circumventing the natural affinity exhibited by the phosphonic acid moiety for the iron oxide surface. These claims are supported via a multimodal characterization platform which includes thermogravimetric analysis, X-ray photoelectron spectroscopy, and metal contact analysis and are consistent with a properly oriented, highly active ligand on the nanoparticle surface. These experiments suggest thiol-ene click chemistry as both a practical and generally applicable strategy for the directed deposition of multifunctional ligands on metal oxide nanoparticle surfaces.