In vitro ovarian follicle culture is a new frontier in assisted reproductive technology with tremendous potential, especially for fertility preservation. Folliculogenesis within the ovary is a complex process requiring interaction between somatic cell components and the oocyte. Conventional two-dimensional culture on tissue culture substrata impedes spherical growth and preservation of the spatial arrangements between oocyte and surrounding granulosa cells. Granulosa cell attachment and migration can leave the oocyte naked and unable to complete the maturation process. Recognition of the importance of spatial arrangements between cells has spurred research in to three-dimensional culture system. Such systems may be vital when dealing with human primordial follicles that may require as long as three months in culture. In the present work we review pertinent aspects of in vitro follicle maturation, with an emphasis on tissue-engineering solutions for maintaining the follicular unit during the culture interval. We focus primarily on presenting the various 3-dimensional culture systems that have been applied for in vitro maturation of follicle:oocyte complexes. We also try to present an overview of outcomes with various biomaterials and animal models and also the limitations of the existing systems.

/pdf/three-dimensional-in-vitro-follicle-growth-overview-of-32koa7uh4t.pdf

Three-dimensional in vitro follicle growth: overview of culture models, biomaterials, design parameters and future directions

Wet anisotropic etching based silicon micromachining is an important technique to fabricate freestanding (e.g. cantilever) and fixed (e.g. cavity) structures on different orientation silicon wafers for various applications in microelectromechanical systems (MEMS). {111} planes are the slowest etch rate plane in all kinds of anisotropic etchants and therefore, a prolonged etching always leads to the appearance of {111} facets at the sidewalls of the fabricated structures. In wet anisotropic etching, undercutting occurs at the extruded corners and the curved edges of the mask patterns on the wafer surface. The rate of undercutting depends upon the type of etchant and the shape of mask edges and corners. Furthermore, the undercutting takes place at the straight edges if they do not contain {111} planes. {100} and {110} silicon wafers are most widely used in MEMS as well as microelectronics fabrication. This paper reviews the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching. Fabrication methods are classified mainly into two major categories: corner compensation method and two-steps etching technique. In corner compensation method, extra mask pattern is added at the corner. Due to extra geometry, etching is delayed at the convex corner and hence the technique relies on time delayed etching. The shape and size of the compensating design strongly depends on the type of etchant, etching depth and the orientation of wafer surface. In this paper, various kinds of compensating designs published so far are discussed. Two-step etching method is employed for the fabrication of perfect convex corners. Since the perfectly sharp convex corner is formed by the intersection of {111} planes, each step of etching defines one of the facets of convex corners. In this method, two different ways are employed to perform the etching process and therefore can be subdivided into two parts. In one case, lithography step is performed after the first step of etching, while in the second case, all lithography steps are carried out before the etching process, but local oxidation of silicon (LOCOS) process is done after the first step of etching. The pros and cons of all techniques are discussed.

/pdf/a-comprehensive-review-on-convex-and-concave-corners-in-5f1mlgjztz.pdf

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

We present a method to discriminate normal oocytes in an optoelectrofluidic platform based on the optically induced positive dielectrophoresis (DEP) for in vitro fertilization. By combining the gravity with a pulling-up DEP force that is induced by dynamic image projected from a liquid crystal display, the discrimination performance could be enhanced due to the reduction in friction force acting on the oocytes that are relatively large and heavy cells being affected by the gravity field. The voltage condition of 10 V bias at 1 MHz was applied for moving normal oocytes. The increased difference of moving velocity between normal and starved abnormal oocytes allows us to discriminate the normal ones spontaneously under the moving image pattern. This approach can be useful to develop an automatic and interactive selection tool of fertilizable oocytes.

/pdf/enhanced-discrimination-of-normal-oocytes-using-optically-21cxz952fs.pdf

Enhanced discrimination of normal oocytes using optically induced pulling-up dielectrophoretic force

Single cells as experimentation units in lab-on-a-chip devices

Microfluidics technology has emerged as an enabling technology for different fields of medicine and life sciences. One such field is male infertility where microfluidic technologies are enabling optimization of sperm sample preparation and analysis. In this chapter we review how microfluidic technology has been used for sperm quantification, sperm quality analysis, and sperm manipulation and isolation with subsequent use of the purified sperm population for treatment of male infertility. As we discuss demonstrations of microfluidic sperm sorting/manipulation/analysis, we highlight systems that have demonstrated feasibility towards clinical adoption or have reached commercialization in the male infertility market. We then review microfluidic-based systems that facilitate non-invasive identification and sorting of viable sperm for in vitro fertilization. Finally, we explore commercialization challenges associated with microfluidic sperm sorting systems and provide suggestions and future directions to best overcome them.

Microfluidic—based sperm sorting & analysis for treatment of male infertility

In vitro fertilising (IVF) probably belongs to the most exciting subjects of research, not only for human assisted reproduction but also for veterinary medicine. Among the various steps of gamete manipulation, the determination of the cell to be fertilised is perhaps the most critical. Up to now, the choice of the oocyte is made using subjective criteria. It is generally the results of a visual estimation of the morphological properties of the cell. In this paper, we describe our first studies concerning the fabrication of a micro-machined lab-on-chip devoted to the analysis of the cells to be fertilised. The overall idea is to end with a system able to capture the cell on the lab-on-chip surface, to transport it to different analysis stages, and to establish an objective catalogue of the oocyte characteristics. The first issue that must be addressed is capturing, transportating and trapping a single cell at different locations on the chip surface. In this article, we present some of the silicon microsystems used for the capture and the transportation of a single oocyte. We also present a lab-on-chip concept, which exploits the microfluidic technology in order to accurately trap the cell at the desired position.

Microsystems and microfluidic device for single oocyte transportation and trapping: Toward the automation of in vitro fertilising

Compensation techniques for producing well defined corner in KOH-etched (1 0 0) silicon have widely been proposed. However, the case of apertures connected with V-grooves has apparently not yet been published. In this paper, we present a compensation technique used in order to produce well defined square apertures connected with V-grooves. A full description of the KOH etching process, simulation methods as well as experimental confirmations are presented here. The technique is very easy to use and is convenient for any size of apertures and V-grooves. The structure obtained with this technique are of interest in many micro-machining domains, especially in the field of micro-fluidics and micro-biology.

Compensation structures for V-grooves connected to square apertures in KOH-etched (1 0 0) silicon: theory, simulation and experimentation

Compensation techniques for producing well-defined bent V-grooves in KOH etched (1 0 0) silicon have been widely proposed. However, many of the methods presented in the literature suffer from two drawbacks: the etching depth is supposed to be equal to the V-groove depth and the V-groove must be wide enough for the compensation structures to fit in the pattern. A few solutions have been proposed in order to get round these disadvantages, but they are generally complicated to implement. In this paper, we propose a very simple compensation technique to obtain well-defined structures with any arbitrary etching depth and/or V-groove width. The only condition for the compensation is that the V-groove must be long enough.

Zouaoui Sadani

Papers

Microsystems and microfluidic device for single oocyte transportation and trapping: Toward the automation of in vitro fertilising

Compensation structures for V-grooves connected to square apertures in KOH-etched (1 0 0) silicon: theory, simulation and experimentation

A very simple compensation technique for bent V-grooves in KOH etched (100) silicon when thin structures or deep etching are required