Liposomes homogeneous crystallization

Talsma et al. [1.34] described the freezing behavior of certain liposomes by DSC measurements. Besides the expected influences of freezing and rewarming speeds, and of the CPAs (mannitol and mannitol in Tris-buffer solutions) it was shown, that the heterogeneous and homogeneous crystallization in mannitol solutions exists and the nucleation of ice depends also on the liposome size In small liposomes (e. g. 0.14 pm) mannitol suppressed the heterogeneous crystallization more effectively than in large (0.87 pm) liposomes. If in certain substances no crystallization or eutectic mixtures can be found by DSC (cephalosporin, Williams [1.35]) with the used experimental conditions, one has to seek different conditions [1.32]. 

Talsma shows that peak 2 changes only from -39.8 °C to —40.4 °C (liposomes, liposomes concentration, buffer and cooling speed as in (I), but no mannitol) if the liposomes size is decreased from 0.87 pm to 0.14 pm. With small liposomes, the start of the homogeneous crystallization is delayed. This can also be deduced from the weakly performed crystallization (Fig. 3.19 (d), peak 3), if mannitol is only within the liposome. 

II) In the following table the temperatures during freezing at which the homogeneous crystallization of ice starts are listed. This is shown by the temperature of pure ice (—41.9 °C) start of homogeneous ice crystallization in different CPAs (lipoid as in Figure 3.19) at a concentration of 30-50 pmol/mL, lipoid size 0.3 pm 10 mM Tris buffer, pH 7.4 CPA and Tris buffer within or outside the liposomes [1.34, p. 68] ... 

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