Swelling behavior of calcium ion-crosslinked sodium alginate in an in vitro hemostatic tamponade model.

Various types of hemostatic agents are used to manage bleeding in surgery. Many such agents are animal products, which carry the risk of secondary infection. The aim of this study is to develop a novel hemostatic agent from a non-animal source that quickly stops bleeding, is easy to use, and has no risk of infection. In this study, we synthesized calcium ion-crosslinked sodium alginate (Alg-Na/Ca) by partial substitution of Ca ions for Na ions in sodium alginate. We prepared 12 kinds of Alg-Na/Ca powders with different Ca mass ratios, molecular weights, M/G ratios and particle size distributions and measured their swelling ratio and the burst pressure generated. We found that Alg-Na/Ca began to swell immediately after contact with saline, especially Alg-Na/Ca at Ca mass ratios of 74.1-77.0 % showed a high swelling ratio after 2 min and a high burst pressure, over 200 % and 500 mmHg respectively. Also, there is a correlation between the swelling ratio after 2 min and the burst pressure. Our results suggest that, by optimizing the composition conditions, Alg-Na/Ca may be an effective hemostatic agent that could act as a tamponade by absorbing and swelling at a bleeding site to quickly achieve primary hemostasis.

Kinetic study of thermally stimulated dissociation of inclusion complex of 1-methylcyclopropene with alpha-cyclodextrin by thermal analysis.

The thermally stimulated dissociation of the inclusion complex of 1-methylcyclopropene (1-MCP) with alpha-cyclodextrin (alpha-CD) in solid state was studied by means of thermogravimetry (TG) and differential scanning calorimetry (DSC). The mass loss of 1-MCP/alpha-CD inclusion complex occurs in four separated phases with the thermal dissociation of the inclusion complex and release of 1-MCP taking place in the second phase between 90 and 230 degrees C. The kinetic parameters of the dissociation reaction (the apparent activation energy of dissociation, E(D), the reaction order of thermal dissociation, n, and the pre-exponential factor, k0) were evaluated. The dissociation reaction was satisfactorily described by the unimolecular decay law, where the reaction order, n = 1. The effect of the molar ratio of 1-MCP to alpha-CD (inclusion ratio) in the inclusion complex on the temperature dependence of the dissociation reaction was also studied. The E(D) decreased with increasing inclusion ratio indicating higher complex stability at lower inclusion ratios. The extrapolation of the E(D) of the inclusion complexes with different inclusion ratios to 1 mol 1-MCP/mol alpha-CD yielded the "true" E(D) of 20.9 +/- 2.8 and 18.1 +/- 0.2 kJ/mol for TG and DSC, respectively. The "true" ln k(0TG) and the "true" ln k(0DSC) were also determined by extrapolation, yielding values of +4.5 +/- 1.0 and -0.3 +/- 0.3, respectively.

Kinetics of molecular encapsulation of 1-methylcyclopropene into alpha-cyclodextrin.

1-methylcyclopropene (1-MCP), an ethylene inhibiting regulator, is commercially available in the form of an inclusion complex with alpha-cyclodextrin (alpha-CD). In this study, molecular encapsulation of gaseous 1-MCP into aqueous alpha-CD was investigated in a closed, agitated vessel with a flat gas-liquid interface. Molecular encapsulation of gaseous 1-MCP by alpha-CD is a simultaneous two-step reaction which involves the aqueous dissolution of gaseous 1-MCP and the encapsulation of the dissolved molecules by alpha-CD. The kinetics and mechanism of molecular encapsulation were analyzed based on the depletion rate of 1-MCP in the headspace of the vessel. The encapsulation rates could be explained quantitatively by the gas absorption theory with a pseudo-first-order reaction between 1-MCP and alpha-CD. The negative value of the calculated apparent activation energy of encapsulation (-24.4 kJ/mol) implied the significant effect of exothermic aqueous dissolution of 1-MCP. An encapsulation temperature of 15 degrees C was optimal; at this temperature, the highest 1-MCP yield and best inclusion ratio of inclusion complex were obtained. Changes in the X-ray diffraction pattern suggested that the crystal lattice structure of alpha-CD was altered upon inclusion of 1-MCP.