Stacking complexation by nicotinamide: a useful way of enhancing drug solubility

Hydrotropic solubilization of poorly water-soluble drugs

The solubilizing ability of two aromatic hydrotropes, N,N-diethylnicotinamide (DENA) and N,N-dimethylbenzamide (DMBA), was investigated using a set of 13 poorly soluble, structurally diverse drugs. The number of aromatic rings in the solute molecule has a very strong effect on the solubility enhancement produced by either hydrotrope. However, although solubility enhancements in the order of 1000- to 10,000-fold were obtained with each of the hydrotropic agents, important differences were found between the two. DMBA is more hydrophobic and undergoes more extensive self-association than DENA, as determined by vapor osmometry. As a result, DMBA is generally a more powerful solubilizer of hydrophobic drugs. DENA, on the other hand, is more polar and its self-association is essentially limited to dimer formation. However, despite being less hydrophobic, DENA is an extremely powerful solubilizer of paclitaxel, a highly hydrophobic compound. Such a result is attributed to the higher hydrogen bonding ability of DENA over DMBA and the very high hydrogen bonding ability of paclitaxel. These observations in turn illustrate the strong interplay between specific and hydrophobic interactions on the observed solubilization by hydrotropic agents.

Overcoming the barriers in micellar drug delivery: loading efficiency, in vivo stability, and micelle-cell interaction

IMPORTANCE OF THE FIELD

Spontaneously constructed from block copolymers in aqueous media, the polymer micelle has been extensively studied as a potential carrier of poorly water-soluble drugs, but cellular uptake pathways and stability of micelles in blood have not yet been clearly understood. An in-depth insight into the physical and biological behaviors of polymer micelles is necessitated for designing next-generation micelles.

AREAS COVERED IN THIS REVIEW

This review suggests possible solutions to improve micellar drug loading capacity, scrutinizes the parameters influencing the micelle stability in blood, and also discusses the fate of micelles in cellular and in vivo environment, respectively. Direct and indirect evidences from the literatures mostly published after 90's were collected, analyzed and summarized.

WHAT THE READER WILL GAIN

A critical analysis of micelle's stability in vivo and micelle-cell interaction is provided to highlight the key issues to be addressed to affirm that micelle can properly work as a drug carrier in clinical settings.

TAKE HOME MESSAGE

With a clear understanding of its behaviors in biological environment, the polymer micelle is a promising nanocarrier for chemotherapy.

Ethyl-paraben and nicotinamide mixtures: apparent solubility, thermal behavior and X-ray structure of the 1:1 co-crystal

This work aims at investigating the nicotinamide (NA)-ethyl-paraben (EP) binary system both in solution and in the solid state. In particular, the apparent EP solubility in water was studied in the presence of different NA concentrations (between 0.28 and 1.64 M). It was found that the apparent EP solubility increase (nearly twofold) observed at the highest NA concentration tested can be ascribed to a change in the polarity of the solvent mixture, rather than to a direct effect of NA on EP. The effect of fusion and re-crystallization from water or ethanol solutions on EP and NA mixtures was investigated by means of differential scanning calorimetry, elemental analysis and X-ray diffraction both on powder and single crystal. It was discovered that EP and NA form a co-crystal having a 1:1 molar composition that can be easily crystallized from ethanol. Single crystal X-ray analysis of this species revealed that the NA and EP molecules form corrugated layers within which the two components are intimately associated by a dense network of hydrogen bonds. In the presence of an excess NA in solution, the EP-NA co-crystal has lower water solubility with respect to both the single co-crystal formers and precipitates in aqueous solutions at ambient temperature.