Anion-Specific Adsorption of Carboxymethyl Cellulose on Cellulose

Integration of fiber modification step with a modern pulp mill is a resource efficient way to produce functional fibers. Motivated by the need to integrate polymer adsorption with the current pulping system, anion-specific effects in carboxymethylcellulose (CMC) adsorption have been studied. The QCM-D adsorption experiments revealed that CMC adsorption to the cellulose model surface is prone to anion-specific effects. A correlation was observed between the adsorbed CMC and the degree of hydration of the co-ions present in the magnesium salts. The presence of a chaotropic co-ion such as nitrate increased the adsorption of CMC on cellulose compared to the presence of the kosmotropic sulfate co-ion. However, anion-specificity was not significant in the case of salts containing zinc cations. The hydration of anions determines the distribution of the ions at the interface. Chaotropic ions, such as nitrates, are likely to be distributed near the chaotropic cellulose surface, causing changes in the ordering of water molecules and resulting in greater entropy gain once released from the surface, thus increasing CMC adsorption

Scanning electron micrographs of PLGA implant cross-sections.

<p>SEM images showing surface and cross-sections of PLGA implants exposed to PBS buffer for 0, 7 and 28 days. <b>A.</b> Surface of Li⁺- or Na⁺-containing (Ctrl) implants, day 0 and <b>B.</b> cross-section of Li⁺-containing and <b>E.</b> Ctrl implant not exposed to buffer, day 0. <b>C.</b> Cross-sections of Li⁺-containing and <b>F.</b> Ctrl implant after submersion (day 7) or <b>D.</b> Li⁺-containing and <b>G.</b> Ctrl implant day 28 in PBS buffer. Design and surface of plug-shaped PLGA implant, see insert <b>A</b>. Implant dimensions; d_head = 3.5 mm, d_shank = 1.8–2.0 mm, l_tot = 3.2 mm, h = 1.0 mm. Pores and air bubbles created during sample preparation for microscopy analysis appeared as black circles in images and were mainly found between the implant and embedding material. The hatched line defines the shape of the plug.</p

<i>In vitro</i> Li⁺ release profile in PBS.

<p>Percentage (%) release of Li₂CO₃ from PLGA implants (error bars represent the standard deviations, n = 3).</p

Total bone area around PLGA implants.

<p>Histomorphometry. <b>A.</b> Total bone area (BA) (%) after 7 and 28 days. The diagram shows mean values and standard deviations. An independent samples T-test was used to compare day 28 vs. 7 for Li⁺ and Ctrl respectively (n = 6–7, * p<0.05, ** p<0.01, ***p<0.001). <b>B.</b> Examination areas (A and B) of histological samples.</p

KEGG pathways with genes downregulated in Li⁺ day 28 vs. 7.

<p>Count indicates the total number of genes from the input list that belong to the corresponding term; only significantly expressed genes (no specific FC limit) were included in the gene list.</p

Validation of the microarray data by qPCR.

<p>Relative gene expression fold change (FC) quantified by qPCR in Li+ or Ctrl peri-implant bone, 28 day vs. 7, postoperatively compared with Affymetrix FC (-  =  undetectable expression). Unpaired Student's t-test or Mann-Whitney test was used for statistical significance analyses (* p<0.05, ** p<0.01, ***p<0.001).</p

TOF-SIMS ion imaging stage scans of PLGA implants.

<p>Images show the Li⁺ intensity (the sum of intensities for the isotopes ⁶Li and ⁷Li) of <b>A.</b> Li⁺-containing PLGA implant and <b>B.</b> Ctrl implant without Li⁺, at day 0.</p

Inflammation associated genes downregulated in Li⁺ day 28 vs. 7.

<p>Data derived from the annotation cluster #6 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102597#pone.0102597.s005" target="_blank">Table S5</a>.</p

Immunostaning of β-catenin, FOSL1 and ASPN in decalcified bone- implant sections, 7 and 28 days postoperatively.

<p><b>A.</b> Li⁺-implant section at 7 days, strong β-catenin immunoreactivity in periosteum, endosteum and within bone marrow cavities in old cortical bone (arrows) was observed. <b>B.</b> Li⁺-implant section at 7 days, β-catenin-positive bone-lining cells (black arrows) within bone marrow cavities. Mono- and multinucleated β-catenin-positive cells facing the implant interface were observed, but also less positive multinucleated cells were observed (white arrows). <b>C.</b> A similar distribution of β-catenin immunoreactivity was observed 28 days post-surgery in a Ctrl-implant section, with cells migrating into PLGA remnants (black arrows). Occasionally, multinucleated cells with less intense β-catenin staining were found at the bone-implant interface (white arrows). <b>D.</b> Li⁺-implant section at 7 days, FOSL1-immunostaining in periosteum, bone depressions and within bone marrow cavities in old cortical bone (arrows). <b>E.</b> FOSL1-positive bone-lining cells within bone marrow cavities at 7 days in a Li⁺-implant section (black arrows). Mono- and multinucleated cells positive for FOSL1 migrated into, or were seen in close vicinity of PLGA remnants (black arrows). Some multinucleated cells less positive for FOSL1 were occasionally observed facing the bone-implant interface (white arrows). <b>F.</b> Ctrl-implant at 28 days, both mono- and multinucleated FOSL1-positive cells were detected at the bone-implant interface (black arrows). <b>G.</b> Li⁺-implant section at 7 days, ASPN immunoreactivity in periosteum, bone depressions and bone marrow cavities (arrows) of the cortical bone. <b>H.</b> Li⁺-implant section at 7 days, ASPN-positive osteoblast seams within bone marrow cavities and mesenchymal-like and multinucleated cells located at the PLGA-bone interface (black arrows). Occasional multinucleated cells that displayed lower immunoreactivity were observed at the interface (white arrows). <b>I.</b> A similar distribution of ASPN immunoreactivity was detected 28 days post-implantation in a Ctrl-implant section, showing ASPN-positive cells actively migrating into the polymeric remnants (black arrows). All sections (A-I) were counterstained with hematoxylin, control sections with isotype staining were used (data not shown). B  =  bone; P = denotes the location of the (removed) PLGA implant, *  =  indicates the PLGA remnants, BM  =  bone marrow. No qualitative or quantitative histological differences were detected between Li⁺ and Ctrl.</p

Differentially regulated genes.

<p>For complete lists, refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102597#pone.0102597.s001" target="_blank">Tables S1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102597#pone.0102597.s004" target="_blank">S4</a>.</p