Potency switch between CHK1 and MK2: discovery of imidazo[1,2-a]pyrazine- and imidazo[1,2-c]pyrimidine-based kinase inhibitors.

Chemistry has been developed to access both imidazo[1,2-a]pyrazines and imidazo[1,2-c]pyrimidines. Small structural modifications in both series led to a switch of potency between two kinases involved in mediating cell cycle checkpoint control, CHK1 and MK2.

Prediction of the thermal phase diagram of amorphous solid dispersions by Flory-Huggins theory.

Miscibility of drug and polymer is one of the key parameters in amorphous formulation design. The purpose of this work is to provide a theoretical approach to evaluate miscibility between drug and polymer in amorphous solid dispersions. The model system is indomethacin and polyvinylpyrrolidone-vinyl acetate copolymer. The Flory-Huggins (F-H) interaction parameter, χ, of drug and polymer was estimated at different temperatures by two methods: melting point depression of drug in various polymer ratios at the melting temperature, and Hildebrand and Scott solubility parameter calculation at 25°C. The simplified first-order relation between the F-H interaction parameter and temperature was established. This allows the construction of a temperature-composition phase diagram of a two-component amorphous system. The spinodal curve was generated and provides an insight into the thermodynamic stability of an amorphous solid dispersion at various temperatures. The predicted stability of the model system was compared with the experimental data. The merits and deficiency of the proposed approach were fully discussed.

Solubility of hydrophobic compounds in water-cosolvent mixtures: relation of solubility with water-cosolvent interactions.

The solubility of organic compounds in mixtures of water and an organic cosolvent can be reasonably estimated from the solubility values in the neat solvents and the composition of the solvent mixture, by means of the log-linear solubilization model. However, deviations from the model are frequently observed in different degree. Such deviations, which tend to become more pronounced with decreasing polarity of the cosolvent, are to a good extent the result the nonideal mixing of water and cosolvent, due to the interactions between the two solvent components. We present a model that incorporates the effect of water-cosolvent interactions into the log-linear model. The effect of nonideality of mixing takes the form of a pseudoquadratic expression on the cosolvent concentration, obtainable from vapor pressure data of the solute-free water-cosolvent mixture.

Interactions between bovine serum albumin and alginate: an evaluation of alginate as protein carrier.

The intermolecular interactions between the model protein, bovine serum albumin (BSA) and a biocompatible polysaccharide, sodium alginate, have been investigated. Both the native BSA and the heat pre-denatured BSA were utilized to study, in parallel, the effect of protein conformational change during the protein-alginate complex formation. In this work, a comparison was performed between the native BSA and the heat-denatured BSA incubated sodium alginate mixtures by using zeta potential analyzer, dynamic light scattering (DLS) and turbidimetric analysis of the systems in combination with protein conformational tools, Fourier transform infrared spectroscopy (FT-IR) and size exclusion chromatography (SE-HPLC). The experimental results demonstrate that the intermolecular chain associations were formed between alginate chains and protein molecules in either the native form or the heat pre-denatured form, mainly driven by the electrostatic interactions between the oppositely charged amino acids and the anionic polysaccharide macromolecules. However, the majority of BSA was recovered from the dissociation of protein-alginate complexes and maintained its secondary structure and conformational property. Therefore, alginate is promising as a bioactive compound carrier.

Preparation of calcium alginate microgel beads in an electrodispersion reactor using an internal source of calcium carbonate nanoparticles.

An electrodispersion reactor has been used to prepare calcium alginate (Ca-alginate) microgel beads in this study. In the electrodispersion reactor, pulsed electric fields are utilized to atomize aqueous mixtures of sodium alginate and CaCO3 nanoparticles (dispersed phase) from a nozzle into an immiscible, insulating second liquid (continuous phase) containing a soluble organic acid. This technique combines the features of the electrohydrodynamic force driven emulsion processes and externally triggered gelations in microreactors (the droplets) ultimately to yield soft gel beads. The average particle size of the Ca-alginate gels generated by this method changed from 412 +/- 90 to 10 +/- 3 microm as the applied peak voltage was increased. A diagram depicting structural information for the Ca-alginate was constructed as a function of the concentrations of sodium alginate and CaCO3 nanoparticles. From this diagram, a critical concentration of sodium alginate required for sol-gel transformation was observed. The characteristic highly porous structure of Ca-alginate particles made by this technique appears suitable for microencapsulation applications. Finally, time scale analysis was performed for the electrodispersion processes that include reactions in the microreactor droplets to provide guidelines for the future employment of this technique. This electrodispersion reactor can be used potentially in the formation of many reaction-based microencapsulation systems.