Gold nanoparticle generation using in situ reduction on a photoresist polymer substrate

This report presents evidence that in-situ reduction of metal ions bound to a cross-linked polymer surface does not always result in nanoparticle formation solely at the interface, as is commonly assumed, but also as much as 40 nm deep within the polymer matrix. Tetrachloroaurate ions were bound using a variety of multi-functional amines to cured films of SU-8 -- a cross-linkable epoxide frequently used for micro- and nanofabrication -- and then treated using one of several reducing agents. The resulting gold-nanoparticle decorated films were examined by X-ray photoelectron spectroscopy and by plan-view and cross-sectional transmission electron microscopy. Reduction using sodium borohydride or sodium citrate generates bands of interspersed particles as much as 40 nm deep within the polymer, suggesting both the Au(III) complex and the reducing agent are capable of penetrating the surface and affecting reduction and formation of nanoparticles within the polymer matrix. It is shown that nanoparticle formation can be confined nearer to the polymer interface by using hydroquinone, a sterically bulkier and less flexible reducing agent, or by reacting the surface in aqueous media with high molecular-weight multifunctional amines, that presumably confine Au(III) nearer to the true interface. These finding have important implications for technologies that apply surface bound nanoparticles, including electroless metallization, catalysis, nano-structure synthesis, and surface enhanced spectroscopy

Associations between Maternal Psychosocial Stress, DNA Methylation, and Newborn Birthweight Identified by Investigating Methylation at Individual, Regional, and Genome Levels

Stress is known to affect health throughout life and into future generations, but the underlying molecular mechanisms are unknown. We tested the hypothesis that maternal psychosocial stress influences DNA methylation (DNAm), which in turn impacts newborn health outcomes. Specifically, we analyzed DNAm at individual, regional, and genome-wide levels in order to test for associations with maternal stress and newborn birthweight. Maternal venous blood and newborn cord blood were assayed for methylation at ~450,000 CpG sites (n = 24 and 22, respectively). Methylation was analyzed by examining CpG sites individually (epigenome-wide-association-study [EWAS]), as regional groups (variably methylated region [VMR] analysis in maternal blood only), and through epigenome-wide measures (genome-wide mean methylation [GMM], Horvath’s epigenetic clock, and mitotic age). These methylation measures were tested for association with three measures of maternal stress (maternal war trauma, chronic stress, and experience of sexual violence) and one health outcome (newborn birthweight). We observed that maternal experiences of war trauma, chronic stress, and sexual assault were each associated with decreased newborn birthweight (p-value \u3c 1.95x10-7 in all cases). Testing individual CpG sites using EWAS, we observed no associations between DNAm and any measure of maternal stress or newborn birthweight in either maternal or cord blood after Bonferroni multiple testing correction, although the top ranked CpG site in maternal blood that associated with maternal chronic stress and sexual violence before multiple testing correction is located near the SPON1 gene. Testing at a regional level, we found increased methylation of a VMR in maternal blood near SPON1 that was associated with chronic stress and sexual violence after Bonferroni multiple testing correction (p-value = 1.95x10-7 and 8.3x10-6, respectively). At the epigenomic level, cord blood GMM was associated with significantly higher levels of war trauma (p-value 0.025) and suggestively associated with sexual violence (p-value = 0.053). The other two epigenome-wide measures were not associated with maternal stress or newborn birthweight in either tissue type. Despite our small sample size, we identified associations even after conservative multiple testing correction. Specifically, we found associations between DNAm and the three measures of maternal stress across both tissues, specifically a VMR in maternal blood and GMM in cord blood were both associated with different measures of maternal stress. The association of cord blood GMM, but not maternal blood GMM, with maternal stress may suggest different responses to stress in mother and newborn. It is noteworthy that we only found associations when CpG sites were analyzed in aggregate, either as variably methylation regions (VMRs) or a broad summary measure of genome-wide mean methylation (GMM)

Controlling Formation Of Gold Nanoparticles Generated In Situ At A Polymeric Surface

This work shows that in situ reduction of metal ions bound at a polymer surface can form nanoparticles within the polymer matrix as well as at the interface, and the size and distribution of nanoparticles between the interface and subsurface depends upon the choice of reagents and reaction conditions. Tetrachloroaurate ions were bound to cross-linked SU-8 films that were functionalized using a variety of multi-functional amines, then reduced using one of several reagents. Reduction using sodium borohydride or sodium citrate generates bands of interspersed gold nanoparticles as much as 40 nm deep within the polymer, indicating that both the Au ions and the reducing agent can penetrate the surface enabling formation of nanoparticles within the polymer matrix. Nanoparticle formation can be confined nearer to the polymer interface by reducing with hydroquinone, or by processing the polymer film in aqueous media using high molecular-weight multifunctional amines that confine the gold ions at the interface. © 2013 Elsevier B.V

Illustration of the analyses performed.

<p>A) <b>S</b>tandard admixture mapping using a frequentist approach tested for association between genetic ancestry and BP. B) Standard association mapping using a frequentist approach tested for association between SNP and BP. Three progressive Bayesian joint admixture and genetic association analyses for BP were performed that prioritized regions of the genome with African ancestry when evaluating the strength of the association between a SNP and BP. C) Model 1 tested for association between SNP genotype and BP, D) Model 2 included discrimination measures, E) Model 3 tested for interaction effects between SNPs and discrimination measures that are associated with BP</p

SNP x unfair treatment interaction effects associated with BP.

<p>BP levels are shown on the y-axis and unfair treatment (No/Yes) on the x-axis. SNP genotype is colored blue, gray or red. A) Significant association between SBP and UT-Self is dependent on SNP rs11190458 genotype in the <i>PKD2L1</i> gene. B) Significant association between DBP and UT-Self is dependent on SNP rs11190458 genotype in the <i>PKD2L1</i> gene. Significant associations between SBP and UT-Other are dependent on SNP genotypes C) rs35283004 upstream of <i>HTR4/ADRB2</i> genes D) rs11042725 upstream of <i>SBF2/ADM</i> genes and E) rs547330 in the <i>ABI3BP</i> gene.</p

Comparison of the significant genes that we found to be associated with BP with other reported phenotypes.

<p>Comparison of the significant genes that we found to be associated with BP with other reported phenotypes.</p

Genetic Loci and Novel Discrimination Measures Associated with Blood Pressure Variation in African Americans Living in Tallahassee

<div><p>Sequencing of the human genome and decades of genetic association and linkage studies have dramatically improved our understanding of the etiology of many diseases. However, the multiple causes of complex diseases are still not well understood, in part because genetic and sociocultural risk factors are not typically investigated concurrently. Hypertension is a leading risk factor for cardiovascular disease and afflicts more African Americans than any other racially defined group in the US. Few genetic loci for hypertension have been replicated across populations, which may reflect population-specific differences in genetic variants and/or inattention to relevant sociocultural factors. Discrimination is a salient sociocultural risk factor for poor health and has been associated with hypertension. Here we use a biocultural approach to study blood pressure (BP) variation in African Americans living in Tallahassee, Florida by genotyping over 30,000 single nucleotide polymorphisms (SNPs) and capturing experiences of discrimination using novel measures of unfair treatment of self and others (n = 157). We perform a joint admixture and genetic association analysis for BP that prioritizes regions of the genome with African ancestry. We only report significant SNPs that were confirmed through our simulation analyses, which were performed to determine the false positive rate. We identify eight significant SNPs in five genes that were previously associated with cardiovascular diseases. When we include measures of unfair treatment and test for interactions between SNPs and unfair treatment, we identify a new class of genes involved in multiple phenotypes including psychosocial distress and mood disorders. Our results suggest that inclusion of culturally relevant stress measures, like unfair treatment in African Americans, may reveal new genes and biological pathways relevant to the etiology of hypertension, and may also improve our understanding of the complexity of gene-environment interactions that underlie complex diseases.</p></div

Significant SNPs associated with SBP from joint ancestry and association analyses.

<p>Significant SNPs associated with SBP from joint ancestry and association analyses.</p

Bayesian Manhattan plots for joint ancestry and association testing with BP.

<p>Each association is plotted based on its chromosomal position (x axis) and the posterior probability that a locus affects BP (y axis). The dashed line indicates the threshold for genome-wide significance (posterior probability ≥0.5). Model 1 results are shown for A) SBP and B) DBP. Model 2/UT-Self plot for C) SBP and D) DBP. Model 2/UT-Other plot for E) SBP and F) DBP. Model 3/UT-Self No/Yes plot for G) SBP and H) DBP. Model 3/UT-Other No/Yes plot for I) SBP and J) DBP.</p