Hierarchical structure in polymer‐based drug delivery systems as probed by calorimetric measurements

Thermoporosimetry (TPM), a differential scanning calorimetry technique that relies on the shift of transition temperatures caused by the confinement of liquids, was applied to elucidate the complex morphology of drug‐loaded polymeric microcapsules prepared by the emulsion solvent evaporation method. For the very first time, TPM has been applied simultaneously with two liquids as structural probes. It was found that Miglyol, which dissolves the selected drug (Ibuprofen), is confined inside vesicles having a mean radius of 26.3 nm, whereas water, which is the continuous phase, is trapped inside a swollen polymeric network of Eudragit with an average mesh radius of 1.7 nm. A proposed hierarchical structure is given, which predicts that Eudragit microcapsules are formed from a collection of inert oil vesicles partitioned by polymeric Eudragit membranes swollen by water. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1939–1945, 2010     

Possible use of DFT approaches for the determination of double exchange interactions

DFT calculations are performed on a model mixed-valence system presenting a double exchange phenomenon. Due to the intrinsic multireference character of the lowest Ms components of the spin states, it is shown that the interactions involved in the double-exchange model cannot be simply extracted from the DFT energies as it is sometimes done. It is, however, possible to extract from different DFT single determinant energies the interactions of a generalized Hubbard Hamiltonian, from which, in a second step, the double-exchange spectrum may be evaluated. The problems generated by the charge and spin polarization are discussed in both symmetric and non symmetric geometries, and the sensitivity of the results to the choice of the density functional is illustrated.     

A Cox Process Involved in the Bose–Einstein Condensation

The point process corresponding to the configurations of bosons in standard conditions is a Cox process driven by the square norm of a centered Gaussian process. This point process is infinitely divisible. We point out the fact that this property is preserved by the Bose–Einstein condensation phenomenon and show that the obtained point process after such a condensation occured, is still a Cox process but driven by the square norm of a shifted Gaussian process, the shift depending on the density of the particles. This law provides an illustration of a “super”- Isomorphism Theorem existing above the usual Isomorphism Theorem of Dynkin available for Gaussian processes. Submitted: February 8, 2008. Accepted: March 5, 2008.     

Bacteria encapsulation in colloidal inorganic matrices: Is it a general method?

Zirconium oxyhydroxide nanoparticles prepared by an aqueous route were evaluated for Escherichia coli bacteria encapsulation. A low viability rate was measured 24 hours after immobilization that could be attributed to nanoparticle cytotoxicity. Moreover, the presence of glycerol, a long-term cell-preserving molecule, hindered gel formation, probably due to its adsorption on the nanoparticle surface. A comparison with boehmite and ferrihydrite gels previously synthesized following a similar aqueous colloidal route suggests that the generalization of this method will rely on a careful control of the nanoparticle surface reactivity and may require surface chemical modification.     

Evaluation of Vanadium(IV) as a Non-radioactive Surrogate for Technetium(IV) by Comparison of Stability Constants for Polyamino Polycarboxylate Ligand Complexation

The stability constants for the Tc(IV) and V(IV) complexation with the polyamino polycarboxylate ligands IDA, NTA, HEDTA and DTPA were determined using liquid–liquid extraction techniques. These stability constants were then used to evaluate the validity of using V(IV) as a chemical analogue for Tc(IV). Results suggest that Tc(IV), as TcOOH⁺, will form β _1?11 complexes with the selected ligands, while V(IV), as VO²⁺, will form β ₁₀₁ complexes. The values for these determined stability constants are (in log₁₀ unit) 10.9 ± 0.1, 11.4 ± 0.1, 14.9 ± 0.1, and 20.1 ± 0.1 for Tc(IV) in 0.5 mol·L^?1 NaCl at 25 °C, for IDA, NTA, HEDTA and DTPA, respectively, they are 9.3 ± 0.1, 11.6 ± 0.2, 15.8 ± 0.1, and 20.8 ± 0.1 for V(IV) in 0.5 mol·L^?1 NaCl at 25 °C, for the same suite of ligands. The incorporation of a hydroxide into the metal ligand complexes formed by Tc(IV) is proposed as the largest factor differentiating the apparent stability constants of Tc(IV) and V(IV). This work shows that V(IV) is a poor analog for Tc(IV); however, despite the differences in complexation mechanism between V(IV) and Tc(IV), V(IV) still appears to have some use for predicting Tc(IV) complexation behavior.     

Self-induced "electroclick" immobilization of a copper complex onto self-assembled monolayers on a gold electrode

We report the self-induced "electroclick" immobilization of the [Cu(II)(6-ethynyl-TMPA)(H(2)O)](2+) complex, by its simple electro-reduction, onto a mixed azidoundodecane-/decane-thiol modified gold electrode. The redox response of the grafted [Cu(II/I)(TMPA)] at the modified electrode is fully reversible indicating no Cu coordination change and a fast electron transfer.     

Epoxy-functionalized large-pore SBA-15 and KIT-6 as affinity chromatography supports

Mesoporous silica supports are proposed as an alternative to polymeric stationary phases for fast affinity chromatography due to their better mechanical strength compared to polymers. Ideal supports should combine high surface area and large pore size to allow a high loading capacity of large molecules, such as proteins, and favor their accessibility. Increasing the pore size of large-surface area micelle-templated silicas (SBA-15, KIT-6) has been achieved by swelling the micelles by the addition of organic molecules and increasing synthesis time and temperature. The pore size of hexagonal silica mesostructured SBA-15 has been increased up to 35 nm. These materials could find therefore application as affinity chromatography for immunoextraction.