Electrochemistry as an interfacial probe for realising physicochemical insights into the dynamics of bio-convection of human sperm cells

随着高效体外受精(IVF)方案的社会重要性不断提高，这项研究试图为试管受精实验室开发新的、有效的和复杂的工具，以探测射精样本的全球和统计受精可能性。精子是人类所有细胞中最小的，通常有一个椭圆形的头部(长千分之四毫米，宽千分之二到千分之三毫米，最大厚千分之一毫米)，有尾巴(鞭毛)，长度为千分之五点五毫米，通常相当于一根高加索人发丝的直径。它们的形状与它们的生物功能相关这些细胞(生物颗粒)(通过对流和扩散)从女性的入口点(在子宫颈)移动到最终目的地，即卵子(雌性配子)。这一过程是艰难的，因为宫颈粘液的存在，尤其是宫颈粘液的存在，是精子运动不良(流体力学)的障碍。令人惊讶的是，在正常生育的男性中，每次射精的4000万个精子细胞中高达90%可能是由于生理上的异常，表现出细胞的一个或多个区域存在缺陷，包括头部大小、形状和尾巴缺陷；合并精子的出现并不少见。这些畸形对个体精子细胞游过女性生殖道的能力有影响。然而，控制男性亚生育能力的不仅仅是单个精子细胞的物理大小和形状；受精需要细胞不仅在物理上活跃，而且能够对当地环境的化学刺激做出反应。精子细胞对化学刺激的反应在男科学中是一个相对较新的研究领域，而且由于精子膜带有电荷，因此导致它们存放的介质呈现局部结构(双电层或离子气氛)，这一点变得复杂起来。这些细胞的后一种特性使它们能够在与精子细胞相当(或更小)的带电界面上被检测到，因为细胞与界面的相互作用将使电流(电荷流)通过界面。这种电流很小，但可以用复杂的麦克风进行监测，就像在无线电或电视转播的足球比赛中清楚地听到踢足球(一个大颗粒与同等大小的表面相互作用)的声音一样。电流的大小及其随时间的衰减提供了有关生物颗粒大小和形状的信息，并可用于确定单个精子细胞的运动性。此外，在带电界面上的氧化还原转换(即，或者，光诱导合成(光解)能够在靠近界面的可控距离处产生能够以化学方式刺激精子细胞的限定数量的物质。这使得能够确定射精样本中单个精子细胞的物理化学效应，从而可能导致对样本受精能力的推断。

With the currently increasing social importance of efficient in vitro fertilisation (IVF) protocols, this research seeks to develop new, effective, and sophisticated tools for the IVF laboratory that probe the global and statistical fertilising potential probability of an ejaculate sample. Spermatozoa are amongst the smallest of all cells in humans and generally possess an oval head (four thousandths of a millimetre long, two-to-three thousandths of a millimetre wide, whilst being maximally one-and-a-half thousandths of a millimetre thick), with a tail (flagellum) which, at fifty-five thousandths of a millimetre long is typically equivalent to the diameter of individual Caucasian hair strands. Their shape is correlated with their biological function - these cells ( biological particles ) move (via convection and diffusion) from a point of entry in the female (at the cervical os) to an ultimate destination, the ovum (female gamete). This journey is arduous, since the presence of, amongst other things, cervical mucus, serves as a barrier to sperm which have poor motion (hydrodynamics). Surprisingly, in normal fertile males, up to 90% of the 40 million sperm cells per ejaculate may by physically abnormal, exhibiting defects in one or several regions of the cell including head size and shape and tail defects; the occurrence of conjoined sperm is not uncommon. These deformations have implications regarding the ability of individual sperm cells to swim through the female genital tract. Yet it is not merely the physical size and shape of individual sperm cells which controls male sub-fertility; fertilisation requires cells which are not only active physically, but also able to respond to a chemical stimulus of its local environment. How sperm cells respond to chemical stimulus is an relatively new research area in andrology, and is complicated by the fact that sperm membranes have a charge and therefore cause the medium in which they are deposited to take on a local structure (an electrical double layer or ionic atmosphere ). This latter property of these cells enables their detection at electrified interfaces of comparable (or smaller) size to the sperm cells, since the interaction of cell with interface will enable electrical current (charge flow) through the interface. This current is tiny, but can be monitored using sophisticated microphones in an analagous way that a kick of a football (a large particle interacting with a comparably-sized surface) is clearly heard on radio- or TV-broadcasted football matches. The size of this electrical current and its decay in time provides information regarding the biological particle size and shape, and can allow for the determination of the individual sperm cell motility. Moreover, redox transformation at electrified interfaces (viz. electrolysis), or, alternatively, light-induced synthesis (photolysis) is able to generate, at controlled distances close to the interface, defined quantities of substances which are able to stimulate chemically sperm cells. This allows for the determination of the physico-chemical effects on individual sperm cells within an ejaculate sample, and thus may lead to inferences regarding the fertilising capability of the sample.