Cellulose nanofibrils were produced from P. radiata kraft pulp fibers. The nanofibrillation was facilitated by applying 2,2,6,6-tetramethylpiperidinyl-1-oxyl-mediated oxidation as pretreatment. The oxidized nanofibrils were cross-linked with polyethyleneimine and poly N-isopropylacrylamide-co-allylamine-co-methylenebisacrylamide particles and were frozen to form cryo-structured gels. Samples of the gels were critical-point dried, and the corresponding structures were assessed with scanning electron microscopy. It appears that the aldehyde groups in the oxidized nanofibrils are suitable reaction sites for cross-linking. The cryo-structured materials were spongy, elastic, and thus capable of regaining their shape after a given pressure was released, indicating a successful cross-linking. These novel types of gels are considered potential candidates in biomedical and biotechnological applications.
Bromate, which is a potential carcinogen, should be removed from drinking water to levels of less than 10 microg/L. A chitosan-based molecularly imprinted polymer (MIP) and a sol-gel ion-exchange double hydrous oxide (Fe(2)O(3) x Al(2)O(3) x xH(2)O) adsorbent (inorganic adsorbent) were prepared for this purpose. The sorption behavior of each adsorbent including sorption kinetics, isotherms, effect of pH and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had better selectivity for bromate, even in the presence of high concentrations of nitrate, as compared to the inorganic adsorbent. It was found that pH does not affect the adsorption of bromate when using the inorganic adsorbent. Additionally, both adsorbents were immobilized in a polymeric cryogel inside plastic carriers to make them more practical for using in larger scale. Regeneration of the cryogels either containing MIP or inorganic adsorbents were carried out by 0.1 M NaOH and 0.1 M NaCl, respectively. It was found that the regenerated MIP and inorganic adsorbents could be used at least three and five times, respectively, without any loss in their sorption capacity.
Composite
cryogels containing boronic acid ligands are synthesized
for effective separation and isolation of bacteria. The large and
interconnected pores in cryogels enable fast binding and release of
microbial cells. To control bacterial binding, an alkyne-tagged boronic
acid ligand is conjugated to azide-functionalized cryogel
via
the Cu(I)-catalyzed azide–alkyne cycloaddition
reaction. The boronic acid-functionalized cryogel binds Gram-positive
and Gram-negative bacteria through reversible boronate ester bonds,
which can be controlled by pH and simple monosaccharides. To increase
the capacity of affinity separation, a new approach is used to couple
the alkyne-tagged phenylboronic acid to cryogel
via
an intermediate polymer layer that provides multiple immobilization
sites. The morphology and chemical composition of the composite cryogel
are characterized systematically. The capability of the composite
cryogel for the separation of Gram-positive and Gram-negative bacteria
is investigated. The binding capacities of the composite cryogel for
Escherichia coli
and
Staphylococcus
epidermidis
are 2.15 × 10
9
and 3.36
× 10
9
cfu/g, respectively. The bacterial binding of
the composite cryogel can be controlled by adjusting pH. The results
suggest that the composite cryogel may be used as affinity medium
for rapid separation and isolation of bacteria from complex samples.
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