Department of Medical Genetics and Molecular Biochemistry, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, USA.
Int J Mol Sci. 2020 Nov 9;21(21):8388. doi: 10.3390/ijms21218388.
Archaeosomes have drawn increasing attention in recent years as novel nano-carriers for therapeutics. The main obstacle of using archaeosomes for therapeutics delivery has been the lack of an efficient method to trigger the release of entrapped content from the otherwise extremely stable structure. Our present study tackles this long-standing problem. We made hybrid archaeosomes composed of tetraether lipids, called the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon , and the synthetic diester lipid dipalmitoylphosphatidylcholine (DPPC). Differential polarized phase-modulation and steady-state fluorometry, confocal fluorescence microscopy, zeta potential (ZP) measurements, and biochemical assays were employed to characterize the physical properties and drug behaviors in PLFE/DPPC hybrid archaeosomes in the presence and absence of live cells. We found that PLFE lipids have an ordering effect on fluid DPPC liposomal membranes, which can slow down the release of entrapped drugs, while PLFE provides high negative charges on the outer surface of liposomes, which can increase vesicle stability against coalescence among liposomes or with cells. Furthermore, we found that the zeta potential in hybrid archaeosomes with 30 mol% PLFE and 70 mol% DPPC (designated as PLFE/DPPC(3:7) archaeosomes) undergoes an abrupt increase from -48 mV at 37 °C to -16 mV at 44 °C (termed the ZP transition), which we hypothesize results from DPPC domain melting and PLFE lipid 'flip-flop'. The anticancer drug doxorubicin (DXO) can be readily incorporated into PLFE/DPPC(3:7) archaeosomes. The rate constant of DXO release from PLFE/DPPC(3:7) archaeosomes into Tris buffer exhibited a sharp increase (~2.5 times), when the temperature was raised from 37 to 42 °C, which is believed to result from the liposomal structural changes associated with the ZP transition. This thermo-induced sharp increase in drug release was not affected by serum proteins as a similar temperature dependence of drug release kinetics was observed in human blood serum. A 15-min pre-incubation of PLFE/DPPC(3:7) archaeosomal DXO with MCF-7 breast cancer cells at 42 °C caused a significant increase in the amount of DXO entering into the nuclei and a considerable increase in the cell's cytotoxicity under the 37 °C growth temperature. Taken together, our data suggests that PLFE/DPPC(3:7) archaeosomes are stable yet potentially useful thermo-sensitive liposomes wherein the temperature range (from 37 to 42-44 °C) clinically used for mild hyperthermia treatment of tumors can be used to trigger drug release for medical interventions.
archaeosomes 作为治疗药物的新型纳米载体，近年来受到越来越多的关注。使用 archaeosomes 进行治疗药物传递的主要障碍一直是缺乏一种有效的方法来触发包封在结构极其稳定的 archaeosomes 中的内容物的释放。我们目前的研究解决了这个长期存在的问题。我们制备了由四醚脂质组成的杂交 archaeosomes，称为从嗜热嗜酸古菌中分离得到的极性脂质部分 E（PLFE），和合成的二酯脂质二棕榈酰磷脂酰胆碱（DPPC）。使用差分偏振调制和稳态荧光法、共聚焦荧光显微镜、Zeta 电位（ZP）测量和生化测定来表征 PLFE/DPPC 杂交 archaeosomes 的物理性质和药物行为，以及在有和没有活细胞的情况下。我们发现 PLFE 脂质对流体 DPPC 脂质体膜具有有序作用，这可以减缓包封药物的释放，而 PLFE 在脂质体的外表面提供高负电荷，这可以增加囊泡对脂质体或与细胞之间融合的稳定性。此外，我们发现具有 30mol%PLFE 和 70mol%DPPC 的杂交 archaeosomes 的 ZP（命名为 PLFE/DPPC（3:7） archaeosomes）的 ZP 从 37°C 时的-48mV 急剧增加到 44°C 时的-16mV（称为 ZP 转变），我们假设这是由于 DPPC 域熔化和 PLFE 脂质“翻转”。抗癌药物阿霉素（DXO）可以很容易地掺入 PLFE/DPPC（3:7） archaeosomes 中。当温度从 37°C 升高到 42°C 时，DXO 从 PLFE/DPPC（3:7） archaeosomes 释放到 Tris 缓冲液中的速率常数急剧增加（约 2.5 倍），这被认为是与 ZP 转变相关的脂质体结构变化的结果。这种热诱导的药物释放的急剧增加不受血清蛋白的影响，因为在人血清中观察到了类似的温度依赖性药物释放动力学。在 42°C 下，PLFE/DPPC（3:7） archaeosomalDXO 与 MCF-7 乳腺癌细胞孵育 15min 会导致进入细胞核的 DXO 量显著增加，并且在 37°C 生长温度下细胞的细胞毒性显著增加。总的来说，我们的数据表明，PLFE/DPPC（3:7） archaeosomes 是稳定的，但具有潜在的有用的温敏脂质体，其中临床用于肿瘤温和热疗的温度范围（37 至 42-44°C）可用于触发药物释放以进行医疗干预。
