Transmission electron freeze drying

Tobacco primary cell wall and normal bacterial Acetobacter xylinum cellulose formation produced a 36.8 3A triple-stranded left-hand helical microfibril in freeze-dried Pt-C replicas and in negatively stained preparations for transmission electron microscopy (TEM). A. xylinum growth in the presence of 0.25 mM Tinopal disrupted cellulose microfibril formation and produced a... 

The reaction was so fast as to finish within 1 min, as shown by the transmission electron microscopy (TEM) images in Figure 3.3.2, for which each withdrawn sample on a copper grid was instantly quenched with liquid nitrogen and freeze-dried without melting. 

Particle-Size Determination Particle-size of the cleaned1 latexes were determined using transmission electron microscopy after freeze-drying the samples and counting the particles with a Quantimet image analyzer. The number average particle diameters ( n) of the homopolymer, the 85/15 VA/BA and 70/30 VA/BA latexes were found to be 0.Q57/ m, 0.062/<.m and 0.073 m, respectively. 

The stability and suitability of the formulations also needs to be determined, for example, whether the viscosity of the formulation is suitable for the administration route and is stable over time. The water content is a parameter that often has a direct influence on the stability of solid formulations and may influence the appearance of freeze-dried products immensely. Karl-Fisher titration, thermogravitometric analysis (TGA), or DSC is normally used to determine the water content. Various microscopic techniques, where both macroscopic and microscopic appearance of formulation can be determined, such as particle appearance by scanning electron microscopy (SEM) or transmission electron microscopy (TEM), are usually only needed for special formulation. There are several other methods, but which one to choose depends entirely on the formulation and the critical parameters (149,150). 

Transmission electron micrograph (TEM) images of log phase Lactobacillus paracasd NFBC 338 (a), spray dried at inlet and outlet temperatures of 180°C and 95-100°C respectively, (b), freeze dried cultures with dead (a) and live intact cell (b). Both cultures were dried in RSM (20% w/v). (Magnification X 60,000). 

Samples were further characterized by transmission electron microscopy using a JEOL JEMIOOB electron microscope. The platinum hydrosol was freeze-dried onto carbon-coated copper microscope grids in order to simulate the final product. Figure 1 shows a micrograph of a typical preparation. The characteristic diffraction pattern of platinum was observed both by electron diffraction and by powder X-ray diffraction. Figure 2 depicts a histogram of the platinum micro-crystal diameters. The mean diameter is 28 A, and the standard deviation is... 

FIGURE 12.26 Transmission electron micrograph of a cross section of acrylic fiber removed from a 55°C dimethylacetamide water spin bath and freeze-dried. Magnification, 20,000 x. 

Figure 17.6 Transmission electron microscopy photomicrographs showing ribbons of 60 nm width. In this case, the ribbons compose the structure of the fibres in a membrane prepared by freeze drying (the bars correspond to 500nm).

Figure 4.48. Transmission electron microscopy micrographs of freeze dried polystyrene latex (A) used as a control for the experiment shows three dimensional particles with no deformation, whereas an air dried film forming latex (B) shows flat regions that have no shadow. The same latex as in (B) after freeze drying is clearly three dimensional, based on the shadows present (C).

Figure 5.114. Transmission electron microscopy micrographs of several emulsion particle samples show a range of aggregation. An air dried droplet (A) resulted in agglomerated flat particles. More three dimensional particles would still be difficult to measure as they are touching (B). The emulsion particles (C) are well dispersed, and shadowing with chromium clearly shows that they are discrete spheres after freeze drying.

---