Investigation of the degradation behaviour of poly(ethylene glycol-co-d,l-lactide) copolymer

The aim was to investigate the degradation behaviour of poly(ethylene glycol-co-d,l-lactide) (PEG-d,l-PLA) multiblock copolymer, in bulk and as microspheres, in aqueous medium. The degradation behaviour of PLA homopolymers in bulk and microspheres was evaluated as comparison.Microsphere preparation was performed by the double emulsion solvent evaporation method. Physical-chemical characterization of the raw polymers and the microspheres was performed by nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry (MDSC). Polymer molecular weight, before and after incubation in aqueous environment, was evaluated by GPC; water uptake and mass loss were determined gravimetrically.The presence of PEG segments inside PLA chains gave a characteristic spongy structure to the microspheres. A significant increase in polymer T_g values was found for the microsphere formulations compared to polymer in bulk. After 63 days of incubation in the aqueous environment, the PEG-d,l-PLA microspheres achieved an average M_w reduction of 47% compared to 20% for PLA microspheres. The corresponding M_w decrease of the polymers in bulk was significantly higher: 72% and 41% for PEG-d,l-PLA and PLA, respectively.The data show how the degradation behaviour of polymer in bulk in an aqueous environment is significantly different from the behaviour of the corresponding microspheres. These results highlight the importance of performing a thorough physical-chemical characterization on microsphere formulations.     

p-Laplacian problems with nonlinearities interacting with the spectrum

The aim of this paper is investigating the existence and the multiplicity of weak solutions of the quasilinear elliptic problem $$\left\{\begin{array}{ll}-\Delta_p u\ =\ g(x, u) \quad {\rm in} \quad \Omega,\\ u=0 \qquad \qquad \qquad {\rm on}\quad \partial\Omega,\end{array}\right.$$ where ${1 < p < + \infty, \Delta_p u = {\rm div}(|\nabla {u}|^{p-2}\nabla {u})}$ , Ω is an open bounded domain of ${\mathbb{R}^N (N \geq 3)}$ with smooth boundary ?Ω and the nonlinearity g behaves as u ^p?1 at infinity. The main tools of the proof are some abstract critical point theorems in Bartolo et al. (Nonlinear Anal. 7: 981–1012, 1983), but extended to Banach spaces, and two sequences of quasi–eigenvalues for the p–Laplacian operator as in Candela and Palmieri (Calc. Var. 34: 495–530, 2009), Li and Zhou (J. Lond. Math. Soc. 65: 123–138, 2002).     

A chromatographic study on the exceptional enantioselectivity of cellulose tris(4-methylbenzoate) towards C5-chiral 4,5-dihydro-(1H)-pyrazole derivatives

A set of ten C5-chiral 4,5-dihydro-(1H)-pyrazole derivatives was synthesized and analyzed by high-performance liquid chromatography (HPLC) on the polysaccharide-based Chiralcel OJ-H chiral stationary phase (CSP). The enantioseparations were carried out using pure ethanol as eluent. Different structural elements of the investigated compounds were recognized for obtaining a very high enantioselectivity. In order to clarify some aspects of the chiral discrimination process, the thermodynamic parameters associated to the enantiorecognition and the enantiomer elution order were established.     

Permeability and micromechanical properties of silk ionomer microcapsules

We studied the pH-responsive behavior of layer-by-layer (LbL) microcapsules fabricated from silk fibroin chemically modified with different poly amino acid side chains: cationic (silk-poly l-lysine, SF-PL) or anionic (silk-poly-l-glutamic acid, SF-PG). We observed that stable ultrathin shell microcapsules can be assembled with a dramatic increase in swelling, thickness, and microroughness at extremely acidic (pH < 2.5) and basic (pH > 11.0) conditions without noticeable disintegration. These changes are accompanied by dramatic changes in shell permeability with a 2 orders of magnitude increase in the diffusion coefficient. Moreover, the silk ionomer shells undergo remarkable softening with a drop in Young's modulus by more than 1 order of magnitude due to the swelling, stretching, and increase in material porosity. The ability to control permeability and mechanical properties over a wide range for the silk-based microcapsules, with distinguishing stability under harsh environmental conditions, provides an important system for controlled loading and release and applications in bioengineering.     

Epoxidation of olefins with a silica-supported peracid in supercritical carbon dioxide under flow conditions

Anhydrous 2-percarboxyethyl-functionalized silica (2b), a recyclable supported peracid, is a suitable reagent to perform the epoxidation of alkenes 1 in supercritical carbon dioxide at 250 bar and 40 °C under flow conditions. This procedure simplifies the isolation of the reaction products and uses only carbon dioxide as a solvent under mild conditions. The solid reagent 2b can be easily recycled by a reaction with 30% hydrogen peroxide in an acid medium.     

The Coordination of Ni(II) and Cu(II) Ions to the Polyhistidyl Motif of Hpn Protein: Is It as Strong as We Think?

Hpn, one of Helicobacter pylori's nickel-accessory proteins, is an amazingly peculiar protein: Almost half of its sequence consists of polyhistidyl (poly-His) residues. Herein, we try to understand the origin of this naturally occurring sequence, thereby shedding some light on the bioinorganic chemistry of Hpn's numerous poly-His repeats. By using potentiometric, mass spectrometric, and various spectroscopic techniques, we studied the Ni(II) - and Cu(II) complexes of the wild-type Ac-THHHHYHGG-NH(2) fragment of Hpn and of its six analogues, in which consecutive residues (His or Tyr) were replaced by Ala (Ala-substitution or Ala-scan approaches), thereby resulting in Ac-TAHHHYHGG-NH(2) , Ac-THAHHYHGG-NH(2) , Ac-THHAHYHGG-NH(2) , Ac-THHHAYHGG-NH(2) , Ac-THHHHAHGG-NH(2) , and Ac-THHHHYAGG-NH(2) peptides. We found that the His4 residue is critical for both Ni(II) - and Cu(II) -ion binding and the effectiveness of binding varies even if the substituted amino acid does not take part in the direct binding interactions.     

On the inter-instrument and the inter-laboratory transferability of a tandem mass spectral reference library. 3. Focus on ion trap and upfront CID

Mass spectral libraries represent versatile tools for the identification of small bioorganic molecules. Libraries based on electron impact spectra are rated robust and transferable. Tandem mass spectral libraries are often considered to work properly only on the instrument that has been used to build the library. An exception from that rule is the 'Wiley Registry of Tandem Mass Spectral Data, MSforID'. In various studies with data sets from different kinds of tandem mass spectrometric instruments, the outstanding sensitivity and robustness of this tandem mass spectral library search approach was demonstrated. The instrumental platforms tested, however, mainly included various tandem-in-space instruments. Herein, the results of a multicenter study with a focus on upfront and tandem-in-time fragmentation are presented. Five laboratories participated and provided fragment ion mass spectra from the following types of mass spectrometers: time-of-flight (TOF), quadrupole-hexapole-TOF, linear ion trap (LIT), 3-D ion trap and LIT-Orbitrap. A total number of 1231 fragment ion mass spectra were collected from 20 test compounds (amiloride, buphenin, cinchocaine, cyclizine, desipramine, dihydroergotamine, dyxirazine, dosulepin, ergotamine, ethambutol, etofylline, mefruside, metoclopramide, phenazone, phentermine, phenytoin, sulfamethoxazole, sulfamoxole, sulthiame and tetracycline) on seven electrospray ionization instruments using 18 different instrumental configurations for fragmentation. For 1222 spectra (99.3%), the correct compound was retrieved as the best matching compound. Classified matches (matches with 'relative average match probability' >40.0) were obtained for 1207 spectra (98.1%). This high percentage of correct identifications clearly supports the hypothesis that the tandem mass spectral library approach tested is a robust and universal identification tool.     

Role of Calixarene in Chemotherapy Delivery Strategies

Since cancer is a multifactorial disease with a high mortality rate, the study of new therapeutic strategies is one of the main objectives in modern research. Numerous chemotherapeutic agents, although widely used, have the disadvantage of being not very soluble in water or selective towards cancerous cells, with consequent side effects. Therefore, in recent years, a greater interest has emerged in innovative drug delivery systems (DDSs) such as calixarene, a third-generation supramolecular compound. Calixarene and its water-soluble derivatives show good biocompatibility and have low cytotoxicity. Thanks to their chemical–physical characteristics, calixarenes can be easily functionalized, and by itself can encapsulate host molecules forming nanostructures capable of releasing drugs in a controlled way. The encapsulation of anticancer drugs in a calixarene derivate improves their bioavailability and efficacy. Thus, the use of calixarenes as carriers of anticancer drugs could reduce their side effects and increase their affinity towards the target. This review summarizes the numerous research advances regarding the development of calixarene nanoparticles capable of encapsulating various anticancer drugs.