Effect of mercury column on the microdynamics of the piezo-driven pipettes

Controllable Fabrication of Small-Size Holding Pipets for the Nondestructive Manipulation of Suspended Living Single Cells

The capture and manipulation of single cells are an important premise and basis for intracellular delivery, which provides abundant molecular and omics information for biomedical development. However, for intracellular delivery of cargos into/from small-size suspended living single cells, the capture methods are limited by the lack of small-size holding pipets, poor cell activity, and the low spatial accuracy of intracellular delivery. To solve these problems, a method for the controllable fabrication of small-size holding pipets was proposed. A simple, homemade microforge instrument including an imaging device was built to cut and melt the glass capillary tip by controlling the heat production of a nichrome wire. The controllable fabrication of small-size holding pipets was realized by observing the fabrication process in real time. Combined with an electroosmotic drive system and a micromanipulation system with high spatial resolution, the holding pipet achieved the active capture, movement, and sampling of suspended living single cells. Moreover, solid-phase microextraction was performed on captured single pheochromocytoma cells, and the extracted dopamine was successfully detected using an electrochemical method. The homemade microforge instrument overcame the limitations of traditional microforges, resulting in holding pipets that were sufficiently small for small-size suspended single living cells (5-30 μm). This proactive capture method overcame the shortcomings of existing methods to achieve the multiangle, high-precision manipulation of single cells, thereby allowing the intracellular delivery of small-size single cells in suspension with high spatiotemporal resolution.

Recent advances in critical nodes of embryo engineering technology

The normal development and maturation of oocytes and sperm, the formation of fertilized ova, the implantation of early embryos, and the growth and development of foetuses are the biological basis of mammalian reproduction. Therefore, research on oocytes has always occupied a very important position in the life sciences and reproductive medicine fields. Various embryo engineering technologies for oocytes, early embryo formation and subsequent developmental stages and different target sites, such as gene editing, intracytoplasmic sperm injection (ICSI), preimplantation genetic diagnosis (PGD), and somatic cell nuclear transfer (SCNT) technologies, have all been established and widely used in industrialization. However, as research continues to deepen and target species become more advanced, embryo engineering technology has also been developing in a more complex and sophisticated direction. At the same time, the success rate also shows a declining trend, resulting in an extension of the research and development cycle and rising costs. By studying the existing embryo engineering technology process, we discovered three critical nodes that have the greatest impact on the development of oocytes and early embryos, namely, oocyte micromanipulation, oocyte electrical activation/reconstructed embryo electrofusion, and the in vitro culture of early embryos. This article mainly demonstrates the efforts made by researchers in the relevant technologies of these three critical nodes from an engineering perspective, analyses the shortcomings of the current technology, and proposes a plan and prospects for the development of embryo engineering technology in the future.

Evaluation of the effect of piezo-intracytoplasmic sperm injection on the laboratory, clinical, and neonatal outcomes

PURPOSE

Limited research has been published on the effect of piezo-assisted intracytoplasmic sperm injection (P-ICSI). We evaluated the effect of P-ICSI on the laboratory, clinical, and neonatal outcomes.

METHODS

This retrospective study was based on the data collected between April 2011 and October 2016. Total 1348 mature oocytes from 145 patients were analyzed. Laboratory, clinical, and neonatal outcomes of those given conventional intracytoplasmic sperm injection (C-ICSI) and those administered P-ICSI were examined.

RESULTS

P-ICSI showed significantly more favorable results, with a survival rate of 97.0% (C-ICSI: 94.1%, P < .010) and a fertilization rate of 83.5% (C-ICSI: 70.6%, P < .001). There were no differences in the blastocyst development rate, implantation rate, miscarriage rate, live birth rate, gestational age, birth weight, proportion of male neonates, cesarean section rate, and congenital abnormalities between the two patient groups.

CONCLUSIONS

Our comparison of P-ICSI with C-ICSI showed that P-ICSI significantly improved the survival and fertilization.

An Adaptive Control Method for Ros-Drill Cellular Microinjector with Low-Resolution Encoder

A novel control methodology which uses a low-resolution encoder is presented for a cellular microinjection technology called the Ros-Drill (rotationally oscillating drill). It is developed primarily for ICSI (intracytoplasmic sperm injection) operations, with the objective of generating a desired oscillatory motion at the tip of a micro glass pipette. It is an inexpensive setup, which creates high-frequency (higher than 500 Hz) and small-amplitude (around 0.2 deg) rotational oscillations at the tip of an injection pipette. These rotational oscillations enable the pipette to drill into cell membranes with minimum biological damage. Such a motion control procedure presents no particular difficulty when it uses sufficiently precise motion sensors. However, size, costs, and accessibility of technology to the hardware components severely constrain the sensory capabilities. Consequently, the control mission and the trajectory tracking are adversely affected. This paper presents two contributions: (a) a dedicated novel adaptive feedback control method to achieve a satisfactory trajectory tracking capability. We demonstrate via experiments that the tracking of the harmonic rotational motion is achieved with desirable fidelity; (b) some important analytical features and related observations associated with the controlled harmonic motion which is created by the low-resolution feedback control structure.

Dynamic response of micropipettes during piezo-assisted intracytoplasmic sperm injection

In the intracytoplasmic sperm injection (ICSI) process, a piezoelectric actuator is commonly used to assist the piercing of cell membrane. The longitudinal pulses that are performed by the piezo actuator, however, cause undesired lateral vibrations at the drawn tip of the injection micropipette. This mechanism is not well understood, despite its critical role in piezo-assisted cellular microinjection. We provide an analytical model to characterize the micropipette tip vibrations under assumed base excitation arising from the piezoelectric pulses. The resulting dynamic response is determined by using the Duhamel integral method. This study quantifies the effect of fluid damping, embedded mercury, and the apparent cell membrane elasticity. We found that, in practice, a small mercury droplet filled in pipette essentially creates higher shear forces at the membrane-pipette interface. The increased shear due to underdamped eigenmodes is conceived to assist the piercing of the cell membrane.

Dynamics of flagellar force generated by a hyperactivated spermatozoon

The flagellar force generated by a hyperactivated monkey spermatozoon was evaluated using the resistive force theory applied to the activated (nonhyperactivated) and hyperactivated flagellar waves that were obtained using high-speed video microscopy and digital image processing in order to clarify the mechanism of sperm penetration through the zona pellucida. No difference in the maximum propulsive force, which was parallel to the longitudinal sperm head axis, was found between the activated and hyperactivated spermatozoa. The maximum transverse force (45 pN), which was perpendicular to the longitudinal sperm head axis, of the hyperactivated spermatozoon was ∼2.5 times its propulsive force. As the beat frequency of the flagellar beating remarkably decreased during the hyperactivation, the slowly oscillating transverse force (5 Hz) by the hyperactivated spermatozoon seems to be most effective for sperm penetration through the zona pellucida.

Geometric Characterization of Cell Membrane of Mouse Oocytes for ICSI

Intracytoplasmic sperm injection (ICSI) is a broadly utilized assisted reproductive technology. A number of technologies for this procedure have evolved lately, such as the most commonly utilized piezo-assisted ICSI technique (P-ICSI). An important problem with this technique, however, is that it requires a small amount of mercury to stabilize the tip of the penetration micropipette. A completely different and mercury-free injection technology, called the rotationally oscillating drill (Ros-Drill©) (RD-ICSI), was recently developed. It uses microprocessor-controlled rotational oscillations of a spiked micropipette after the pipette deforms the membrane to a certain tension level. Inappropriate selection of this initiation instant typically results in cell damage, which ultimately leads to unsuccessful ICSI. During earlier manual clinical tests of Ros-Drill, the technicians’ expertise determined this instant in an ad hoc fashion. In this paper, we introduce a computer-vision-based tool to mechanize this process with the objective of maintaining the repeatability and introducing potential automation. Computer images are used for monitoring the membrane deformations and curvature variations as the basis for decision making. The main contribution of this paper is in the specifics of the computer logic to perform the monitoring. These new tools are expected to provide a practicable means for automating the Ros-Drill-assisted ICSI operation.

Visual Feedback Automation for ICSI With Rotationally Oscillating Drill (Ros-Drill©)

Intracytoplasmic sperm injection has attracted research interest from both biological and engineering groups. The technology is constantly evolving to perform this procedure with precision and speed. One such development is the contribution of this paper. We focus on a relatively recent procedure called Ros-Drill© (rotationally oscillating drill), of which the early versions have already been effectively utilized for the mice. Here, we present a procedure to automate a critical part of the operation: initiation of the rotational oscillation. Visual feedback is used to track the pipette tip. Predetermined species-specific penetration depth is successfully utilized to initiate the rotational oscillation command. Penetration-depth-based decisions concur with our earlier curvature-based approach.

Rotationally oscillating drill (Ros-Drill) for mouse ICSI without using mercury

Intracytoplasmic sperm injection (ICSI) is an important assisted reproductive technology (ART). Due to deployment difficulties and low efficiency of the earlier (conventional) version of ICSI, especially in the mouse, a piezo-assisted ICSI technique had evolved as a popular ART methodology in recent years. An important and remaining problem with this technique, however, is that it requires small amounts of mercury to stabilize the pipette tip when piezoelectric force pulses are applied. To eliminate this problem we developed and tested a completely different and mercury-free technology, called the "Ros-Drill" (rotationally oscillating drill). The technique uses microprocessor-controlled rotational oscillations on a spiked micropipette without mercury or piezo. Preliminary experimental results show that this new microinjection technology gives high survival rate (>70% of the injected oocytes) and fertilization rate (>80% of the survived oocytes), and blastocyst formation rates in early trials (approximately 50% of the survived oocytes). Blastocysts created by Ros-Drill ICSI were transferred into the uteruses of pseudopregnant surrogate mothers and healthy pups were born and weaned. The Ros-Drill ICSI technique is automated and therefore; it requires a very short preliminary training for the specialists, as evidenced in many successful biological trials. These advantages of Ros-Drill ICSI over conventional and piezo-assisted ICSI are clearly demonstrated and it appears to have resolved an important problem in reproductive biology.

New technology for cellular piercing: rotationally oscillating μ-injector, description and validation tests

ICSI (intracytoplasmic sperm injection) procedure is one of the most commonly used cellular-injection processes. In ICSI a drawn glass pipette is pushed against the biological cell and a series of force impulses are exerted on it axially to achieve the piercing through the zona and the membrane in sequence for the ensuing injection. In most advanced applications a piezo actuator creates this impulsive forcing. This procedure presently requires a very small mercury column inside the glass pipette which is found to be helpful especially for minimizing the transverse oscillations. Despite the toxic mercury, the procedure is commonly utilized in many laboratories. Earlier investigations point out that considerable lateral tip oscillations of the injection pipette remain as the piezo-electric pulses are introduced. Such oscillations damage the cell membrane and impart adverse effects on the success rate of the injection. In this study, we introduce a novel microinjection procedure, which will remedy the shortfalls of the present technology. The highlight of this procedure is the introduction of rotational oscillations to the pipette during the drilling. These oscillations of small amplitudes (few degrees) and high enough frequencies (100 Hz and higher) are shown to create very effective piercing. The so-called Ros-Drill is a mercury-free and minimally invasive device of which the prototypes are designed and built including the relevant peripheral control hardware and software. Preliminary experimental results are presented on mouse oocytes and they are very encouraging. In the early trials on mouse oocytes, several blastocyst stage developments are reported using new drilling device. We also explain in this text the implementation protocols developed for the new technology.

New optical sensor for monitoring the micropipette motion

A novel noncontact sensor is developed to monitor the displacements of a drawn glass pipette tip. These pipettes are commonly used in various cellular-injection applications, from in vitro fertilization to cloning. The physics of the underlying cellular-piercing process, however, is quite complex and presently not fully understood primarily due to the absence of appropriate motion sensors. A high-sensitivity noncontact sensor is needed to study this delicate microdynamics. We report here on an optical microdevice, which is developed for this objective. In the core of the sensing, properly positioned four photodiodes receive the light, which emanates from the target micropipette. Appropriate electronics and sensitivity-enhancement techniques are also utilized. The experimental results are presented from a preliminary test study on a prototype setup. These results are very encouraging in that we can already report submicrometer-level motion-detection capability.