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Inorganic nanoparticles can be embeddedwithin gels by selectivelypreloading them with suitable molecular precursors followed by reductionor another suitable reaction. Here, we exploit the selective sorptionproperties of cross-linked β-cyclodextrin/poly(ethylene glycol)hydrogels, in analogy with polyurethane foams, to preconcentrate metalsalts (HAuCl4and K2[Co(SCN)4]) andsubsequently generate gel-embedded metal nanoparticles (10–50nm). The nanoparticles are shown to be immobilized within the gelnetwork as a consequence of their large dimensions in comparison tothe gel network pore size. We suggest this is a useful approach forthe generalized synthesis of hybrid soft–hard nanomaterials. [ABSTRACT FROM AUTHOR]

In this work, we present evidence on the suitability of spin probes to report on the thermal treatment of bovine serum albumin (BSA), in the temperature range 293-343 K, and indirectly monitor the release of sodium dodecyl sulfate (SDS) from its complex with BSA using a covalent gel with β-cyclodextrin (β-CD) in the network. The spin probes used, 5- and 7-doxyl-stearic acids (5-DSA, 7-DSA) or 4-(N,N'-dimethyl-N-hexadecyl)ammonium-2,2',6,6'-tetramethylpiperidine-1-oxyl iodide (CAT16), present similar, fatty acid-like structural features. Their continuous wave electron paramagnetic resonance (CW-EPR) spectra, however, reflect different dynamics when complexed with BSA: a restricted motion for 5-DSA, almost nonsensitive to the heating/cooling cycle, and a faster temperature-dependent dynamic motion for CAT16. Molecular docking allows us to rationalize these results by revealing the different binding modes of 5-DSA and CAT16. The EPR data on the temperature effect on BSA are supported by circular dichroism results projecting recovery, upon cooling, of the initial binding ability of BSA for samples heated to 323 K. The interactions occurring in BSA/SDS/β-CD systems are investigated by CW-EPR and FT-ESEEM spectroscopies. It is found that the covalent gel containing β-CD can efficiently remove SDS from the BSA/SDS complex. The gel is not permeable to BSA but it can encapsulate SDS, thus yielding the free protein in solution and allowing recovery of the native protein conformation. Collectively, the accrued knowledge supports potential applications in protein purification biotechnological processes.

The interactions of bovine serum albumin (BSA) with ionic surfactants (sodium dodecyl sulfate, SDS, and cetyltrimethylammonium bromide, CTAB) and β-cyclodextrin (β-CD) have been investigated by electron paramagnetic resonance (EPR) and circular dichroism measurements. The spin probe selected to report on the interaction of albumin with surfactants and/or β-CD was 4-N,N-dimethyl hexadecyl ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (CAT16), on account of (a) its balance between electrostatic and hydrophobic character and (b) the ability of BSA to form complexes with various organic molecules. The distribution of the spin probe among different environments in solutions containing only BSA was confirmed by the existence of two components in the EPR spectra: one revealing a restricted mobility of the spin probe, attributed to the protein-spin probe complex, and another one showing free movement, attributed to the spin probe in solution. The presence of surfactants and/or β-CD alters the distribution of CAT16 between various compartments in each system. Formation of protein aggregates as a result of thermal denaturation was evidenced by the appearance of an immobilized component in the EPR spectrum. This component is not present in the EPR spectra of CAT16 in protein/surfactant or protein/cyclodextrin solutions. Circular dichroism spectra of BSA provided information about changes in the secondary structure of the protein induced by the presence of surfactants and/or cyclodextrin in solution. The results demonstrate that β-CD hinders the interaction between the employed surfactants and the protein. The cationic surfactant (CTAB) induces changes in protein conformation at a lower concentration compared to the anionic surfactant (SDS).

The effect of solvent used during the synthesis and postsynthesis treatment on textural properties of organized mesoporous aluminas was investigated and related to the behavior of spin probes studied by electron spin resonance (ESR) spectroscopy. It was found that the structure of surfactant aggregates serving in the as-synthesized precipitates as templates could be easily modified by treatment with different solvents. This treatment induces corresponding variations in surface areas, mesopore volumes, and mesopore diameters of the final products. The ESR spectrum of 5-doxyl stearic acid spin probe properly reflects the changes in template structure based on changes of the solvent used and represents an early indicator of the corresponding textural modifications of the mesoporous alumina.