Conductive coatings studied on inflated lung in the frozen-hydrated and freeze-dried states.

Evaporative coatings of platinum-carbon and gold on freeze-fractured mouse lung, preserved in frozen-hydrated and freeze-dried states, are studied in secondary emission mode by low temperature scanning electron microscopy. Unfixed, inflated frozen lung is freeze-etched in high vacuum, metal coated and observed frozen-hydrated and freeze-dried, to demonstrate sample shrinkage and coating deformation upon drying the sample. Buckling and cracking of the coatings occur as a result of freeze-drying. Correlative TEM thin film analysis of the coatings is used to estimate film thickness and reticularity. Freeze-drying biological samples is a common SEM preparative technique which causes morphological artifacts due to both freezing and drying. Frozen-hydrated low temperature-SEM investigation can selectively study these artifacts morphologically to distinguish between freezing and drying artifacts.