Powder X-ray diffraction observations of ice crystals formed from disaccharide solutions

Abstract

SummaryPowder X-ray diffraction (PXRD) measurements on rapid freezing samples of disaccharide (trehalose, sucrose, and maltose) solutions indicated that the crystalline phases in the sample were both hexagonal and cubic ice. The cubic ice existed at a higher ratio in the higher disaccharide concentration samples. The temperature ramping experiments revealed that the cubic ice was stable below 233 K, which was obviously higher than the temperature expected for a pure water system. The diffraction peak width of the hexagonal ice crystal was independent in the disaccharide concentrations. This indicated that the crystallite size of the hexagonal ice was more than several hundreds of nanometer, which coincided with the ice particle size previously observed in the freeze-fractured replica samples. The comparison of the present PXRD data with the replica observations by transmission electron microscope in an earlier study allows us to conclude that the cubic ice was formed at the grain boundary between the hexagonal ice and the coexisted non-crystalline disaccharide phase. (160 words)

Freezing Properties of Disaccharide Solutions: Inhibition of Hexagonal Ice Crystal Growth and Formation of Cubic Ice

“…By using the freeze-fracture replica technique and a field-emission gun type transmission electron microscope (FEG-TEM), they investigated the nano-scale size molecular conditions in the disaccharide solutions . To determine the materials observed in the replica images, they carried out the x-ray diffraction experiments on the similarly prepared disaccharide solution samples (Uchida & Takeya, 2010). They identified each phase observed in the TEM images, and they revealed the frozen state of both disaccharide molecules and water molecules.…”

“…However, the replica cannot determine the substances observed in TEM image. Thus they carried out the powder x-ray diffraction (PXRD) measurements for samples prepared under similar conditions (Uchida & Takeya, 2010). They focused primarily on trehalose, which has been considered as one of the cryoprotective agents that reduces the freezing rate of ice (Sei & Gonda, 2004 To compare the properties observed in the various trehalose solutions, they conducted similar investigations using sucrose (of the highest quality; Sigma-Aldrich Japan, Inc.) and maltose (research grade, Hayashibara Biochemical Laboratories, Inc.).…”

“…These results support the assumption that the object P was related to trehalose molecules. To determine each phase observed in the replica image, Uchida & Takeya (2010) carried out the PXRD method for the sample prepared similarity with the replica experiments. These frozen samples were finely powdered in a nitrogen atmosphere at a temperature below 100 K. The fine-powdered samples were top-loaded on a specimen holder made of Cu and mounted onto the powder x-ray diffractometer (Rigaku, type Ultima III).…”

“…The edge of the flat surface area in the sample (c) has a slightly larger contrast than that in sample (b). To determine the material of each phase observed in Figure 5, and to investigate the stability of ice Ic, the temperature ramping PXRD measurements were carried out every 10 K from 93 K to 273 K for the frozen samples of 47wt% trehalose concentration solution quenched in liquid nitrogen (Uchida & Takeya, 2010). The initial profile of the 47 wt% trehalose solution at 93K (the farthest side profile of Figure 6a) was similar to those in Figure 4, which was closed up in the 2θ range from 22 o to 27 o .…”

Physical Characterization of <i>meso</i>-Erythritol as a Crystalline Bulking Agent for Freeze-Dried Formulations

“…Figures 2, 3 show diffraction patterns of frozen mesoerythritol solutions simultaneously obtained by a XRD-DSC system and a temperature-controlled XRD system. The XRD-DSC analysis showed, in addition to the large peaks of the hexagonal ice crystals, appearance and slow growth of new diffraction peaks at 15°, 19°, 20°, 26.5°, 28°, and 30° during holding the frozen solution at −40°C [23][24][25] (Fig. 2).…”