分子ロボット開発に最適な機械的特性を持つリポソームの機械的物性評価

抄録

In this report, we evaluated the mechanical properties of cell-sized liposomes by the micropipette aspiration method for the development of liposomal molecular robots. These properties were evaluated with a standard linear solid model. The liposomes were aspirated by micropipettes prepared in several conditions on combination of coating agent and loading medium (Condition 1, Non-coated + Water; Condition 2, BSA-coated + Water; Condition 3, BSA-coated + HEPES NaOH buffer). While BSA-coated micropipettes could hold liposomes stably, the liposomes aspirated by the noncoated micropipettes were easily raptured. The mechanical properties of the aspirated liposomes were E₀ = 78.6 Pa and E_∞ = 16.4 Pa, μ = 997.5 Pa･s (condition 2) and E₀ = 191.8 Pa，E_∞ = 86.9 Pa，μ = 3824.3 Pa･s (condition 3). The difference in viscosity might be caused by osmotic pressure between the internal fluid of the liposome and that of the micropipette or the degradation of the lipids composing the liposomes. Additionally, the elastic moduli of the liposomes measured in conditions 2 and 3 were smaller than that of the mammal cells. The differences in the elastic modulus were probably due to the cell organelles such as the nucleus and the cytoskeletons. We confirmed the differences between the time-course changes of measured aspiration length and the fitting curves derived from a viscoelastic model. Therefore, in the future, we will try to present a new model that recruits more viscosity elements.