Cisplatin Nanoliposomes for Cancer Therapy: AFM and Fluorescence Imaging of Cisplatin Encapsulation, Stability, Cellular Uptake, and Toxicity

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Abstract
Cisplatin is the most effective cytotoxic agent against many cancers. Its usage, however, is limited due to inefficient uptake by the target cells. A liposomal formulation of cisplatin is reported to partly overcome this limitation. Physicochemical characteristics of the liposome-cisplatin preparation, including its size, stability, encapsulation efficiency, and cytoplasmic internalization efficiency, play a significant role in an effective usage of liposomal formulations. We have used atomic force microscopy (AFM) to determine physicochemical characteristics of cisplatin-encapsulated liposomes, AFM and fluorescence microscopy to examine their cytoplasmic internalization, and Live/Dead assay to examine their cell toxicity. Nonencapsulated cisplatin is globular and 10−50 nm in size. AFM force-dissection and stiffness measurements show that cisplatin-encapsulated liposomes are significantly stiffer (∼100%) and more stable than liposomes without encapsulated cisplatin. Cisplatin-encapsulated liposomes of ∼250 nm diameter (nanoliposomes) are most efficiently internalized and induce cell toxicity in a time-dependent manner. Liposomes without cisplatin of similar dimensions, although internalized in the cell cytoplasm, do not induce cell toxicity.