Sharma V K, Hayes D G, Urban V S, O'Neill H, Tyagi M, Mamontov E
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India; Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.
Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531, USA.
J Colloid Interface Sci. 2021 May 15;590:94-102. doi: 10.1016/j.jcis.2021.01.032. Epub 2021 Jan 16.
Bicontinuous microemulsions (BμEs) are a promising biomembrane mimetic system for investigating the behavior of antimicrobial peptides (AMPs) and their delivery to open wounds to combat antibiotic-resistant microorganisms. The properties of the BμE host are in turn affected by the guest AMP and can deviate from those of the unperturbed BμEs, especially at higher AMP concentrations. Here we report the effect of an archetypal AMP, melittin, over a wide range of concentrations, on the nanoscopic dynamics of BμEs formed by water/sodium dodecyl sulfate (SDS)/1-pentanol/dodecane, investigated using quasi-elastic neutron scattering (QENS). Two distinct motions are observed, namely, (i) the lateral motion of the surfactant on the surface of the oil channels and (ii) the internal motion of the surfactants. It is found that melittin restricts both the lateral and the internal motion, thereby acting as a stiffening agent. The lateral motion is more strongly affected, at low concentration of melittin. The lateral diffusion coefficient decreased sharply, approaching a constant value at higher melittin concentration. These results are in sharp contrast with the recent dynamic light scattering and neutron spin echo results which showed that at the length and time scales longer than those probed in the current work, melittin enhanced the long-range collective and local undulation motions of BμEs. Considered together, our results indicate that incorporation of melittin modulates the dynamics differently depending on the spatial and temporal regimes, in which the dynamics are being probed. The addition of melittin at low concentrations increased the magnitude of the zeta potential, but further increase of the melittin concentration decreased it. This suggests that addition of melittin at low concentrations led to increase in the surfactant concentration, but did not affect the negative charge per surfactant molecule, while further addition of melittin led to ion pairing of melittin with the oppositely charged surfactant. This study therefore demonstrates how the addition of melittin hinders the lateral motion of surfactants as a result of the strong association between melittin and SDS, suggesting that the release of AMPs from BμE-based delivery vehicles may be hindered.
双连续微乳液（BμEs）是一种很有前景的生物膜模拟系统，可用于研究抗菌肽（AMPs）的行为及其向开放性伤口的递送，以对抗抗生素耐药微生物。BμE主体的性质又会受到客体AMP的影响，并且可能偏离未受扰动的BμEs的性质，尤其是在较高的AMP浓度下。在此，我们报道了一种典型的AMP——蜂毒肽，在很宽的浓度范围内，对由水/十二烷基硫酸钠（SDS）/1-戊醇/十二烷形成的BμEs的纳米级动力学的影响，该影响通过准弹性中子散射（QENS）进行研究。观察到两种不同的运动，即：（i）表面活性剂在油通道表面的横向运动和（ii）表面活性剂的内部运动。发现蜂毒肽会限制横向运动和内部运动，从而起到硬化剂的作用。在低浓度的蜂毒肽下，横向运动受到的影响更大。横向扩散系数急剧下降，在较高的蜂毒肽浓度下接近恒定值。这些结果与最近的动态光散射和中子自旋回波结果形成鲜明对比，后者表明在比当前工作所探测的更长的长度和时间尺度上，蜂毒肽增强了BμEs的长程集体和局部波动运动。综合来看，我们的结果表明，蜂毒肽的掺入根据所探测动力学的空间和时间范围不同地调节动力学。低浓度添加蜂毒肽会增加ζ电位的大小，但蜂毒肽浓度的进一步增加会使其降低。这表明低浓度添加蜂毒肽会导致表面活性剂浓度增加，但不影响每个表面活性剂分子的负电荷，而进一步添加蜂毒肽会导致蜂毒肽与带相反电荷的表面活性剂发生离子配对。因此，这项研究证明了蜂毒肽的添加如何由于蜂毒肽与SDS之间的强缔合而阻碍表面活性剂的横向运动，这表明基于BμE的递送载体中AMP的释放可能会受到阻碍。
