A universal piezo-driven ultrasonic cell microinjection system

Penetrating the ultra-tough yeast cell wall with finite element analysis model-aided design of microtools

Microinjecting yeast cells has been challenging for decades with no significant breakthrough due to the ultra-tough cell wall and low stiffness of the traditional injector tip at the micro-scale. Penetrating this protection wall is the key step for artificially bringing foreign substance into the yeast. In this paper, a yeast cell model was built by using finite element analysis (FEA) method to analyze the penetrating process. The key parameters of the yeast cell wall in the model (the Young's modulus, the shear modulus, and the Lame constant) were calibrated according to a general nanoindentation experiment. Then by employing the calibrated model, the injection parameters were optimized to minimize the cell damage (the maximum cell deformation at the critical stress of the cell wall). Key guidelines were suggested for penetrating the cell wall during microinjection.

A novel two-degrees of freedom (2-DOF) piezo-driven positioning platform with the working stroke being over 20 cm

Multi-degrees of freedom piezo-driven precision positioning platforms with large working strokes are demanded in many research fields. Although many multi-degrees of freedom piezo-driven positioning platforms have been proposed, few of them can achieve both large working stroke and high speed, which hinders their applications. In this study, a two-degrees of freedom piezo-driven positioning platform was proposed by stacking two identical stick-slip piezoelectric actuators. To simplify the practical implementation of a large working stroke, the actuator employed a special structure, in which the compliant mechanism and the slider were connected together as a mover and the guide rail was fixed as a stator. The working stroke of the actuator can be increased easily by increasing only the length of the guide rail without changing the output performances. By designing a lever-type compliant mechanism (LCM) on the side surface of the slider, a large loading space was obtained. Theoretical calculation and finite element analysis of the LCM were performed in detail. As the structures of these two stick-slip piezoelectric actuators are the same, only the output performances of the upper actuator (x direction) were tested as an example. Experimental results indicated that the upper actuator had a stable bi-direction motion with a working stroke being over 20 cm. The maximum speeds along the positive x and negative x directions reached 17.864 and 18.73 mm/s, and the resolutions were 100 and 230 nm, respectively. Furthermore, the vertical loading capacity was larger than 60 N.

Step consistency active control method for inertial piezoelectric actuator using embedded strain gauges

Inertial piezoelectric actuators (IPAs) are widely used in micro-nano manipulation, biomedicine, and other fields as the simple structure and excitation signal. However, the step consistency is difficult to guarantee in a large stroke range due to the limited machining accuracy of the mover and inherent roll back, which limits the practical application in these precision fields. Therefore, a step consistency active control method for IPAs is proposed based on bending hybrid motions, which uses embedded strain gauges as the force sensors to acquire the pressure between the mover and the actuator. The IPA is driven by horizontal bending motion, and the pressure can be dynamically adjusted by vertical bending motion to ensure the constant pressure and achieve a constant step. Experiments results show that the maximum standard deviation of the step is 0.41 µm under the active control of 350 V_p-p and 1 Hz driving voltage within 2 mm stroke range in 500 driving cycles, and the maximum standard deviation of the step is 1.14 µm under the non-active control with the same conditions, which show that the proposed method evidently improves the step consistency of IPA in a large stroke range.

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.

Zebrafish In Vivo Models of Cancer and Metastasis

Metastasis, the dispersal of cancer cells from a primary tumor to secondary sites within the body, is the leading cause of cancer-related death. Animal models have been an indispensable tool to investigate the complex interactions between the cancer cells and the tumor microenvironment during the metastatic cascade. The zebrafish (Danio rerio) has emerged as a powerful vertebrate model for studying metastatic events in vivo. The zebrafish has many attributes including ex-utero development, which facilitates embryonic manipulation, as well as optically transparent tissues, which enables in vivo imaging of fluorescently labeled cells in real time. Here, we summarize the techniques which have been used to study cancer biology and metastasis in the zebrafish model organism, including genetic manipulation and transgenesis, cell transplantation, live imaging, and high-throughput compound screening. Finally, we discuss studies using the zebrafish, which have complemented and benefited metastasis research.

A novel micro drill design based on Ros-DrillⒸ

This paper presents the development of a novel micro drill device for single living organisms. Currently, microinjection for mice and some other species is performed with the help of piezo-driven actuators with a very small amount of mercury column in the proximal end of the pipette in order to increase the success rate. However, the toxicity of mercury exhibits a risk factor both for the operator and the injected cells. Therefore, mercury-free devices have become a necessity. Here, a novel micro drill is developed based on the same principle of Ros-Drill^Ⓒ piercing approach; piercing via rotational movements. The new drill is driven by a brushless motor, and it incorporates the micropipette holder. Both the amplitude and the frequency of rotational oscillations can be adjusted in very wide ranges. The experiments reveal that the drill is suitable for different tasks such as microinjection and biopsy of different organisms. It presents good performance in terms of success rate, ease of usage, compactness and compatibility with different manipulation systems.

A Review of Automated Microinjection of Zebrafish Embryos

Cell microinjection is a technique of precise delivery of substances into cells and is widely used for studying cell transfection, signaling pathways, and organelle functions. Microinjection of the embryos of zebrafish, the third most important animal model, has become a very useful technique in bioscience. However, factors such as the small cell size, high cell deformation tendency, and transparent zebrafish embryo membrane make the microinjection process difficult. Furthermore, this process has strict, specific requirements, such as chorion softening, avoiding contacting the first polar body, and high-precision detection. Therefore, highly accurate control and detection platforms are critical for achieving the automated microinjection of zebrafish embryos. This article reviews the latest technologies and methods used in the automated microinjection of zebrafish embryos and provides a detailed description of the current developments and applications of robotic microinjection systems. The review covers key areas related to automated embryo injection, including cell searching and location, cell position and posture adjustment, microscopic visual servoing control, sensors, actuators, puncturing mechanisms, and microinjection.

Note: A novel piezoelectrically driven pipette using centrifugal force

This paper proposes a novel piezoelectrically driven pipette, which utilizes centrifugal force in swing motion of a vibrating tube as the driving force, to input and output liquid at first bending resonant frequency. Control circuit capable of frequency tracking is designed. Pulse volume changing with different driving voltage amplitude, driving frequency, tip size, and target reagents are studied in experiments. The output pulse volume of a prototype pipette driven by voltage of 560 V(pp) at 175.9 Hz is 43.2 μl with a variation of ±3.5%. Minimum water spots of 3 μl can be deposited in this manner. This pipette represents an alternative to standard liquid transfer techniques in chemical or biological experiments.

Zebrafish cancer and metastasis models for in vivo drug discovery

There is a great need for more efficient methods to discover new cancer therapeutics, as traditional drug development processes are slow and expensive. The use of zebrafish as a whole-organism screen is a time and cost-effective means of improving the efficiency and efficacy of drug development. This review features zebrafish genetic and cell transplantation models of cancer and metastasis, and current imaging and automation technologies that, together, will significantly advance the field of anti-cancer drug discovery.

Full in vitro fertilization laboratory mechanization: toward robotic assisted reproduction?

OBJECTIVE

To describe the current efforts made to standardize different steps of assisted reproductive technology processes by the introduction of new technologies for the nonsubjective sperm selection process, oocyte denudation by mechanical removal of cumulus cells, oocyte positioning, sperm motility screening, fertilization, embryo culture, media replacement by microfluidics, and monitoring of embryo development by time-lapse photography, embryo secretions, and/or O(2) consumption. These technologies could be integrated in a unique and fully automated device.

DESIGN

Pubmed database and research and development data from authors.

SETTING

University-affiliated private center.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASUREMENT(S)

None.

RESULT(S)

Several technologies would be useful for: 1) selection of sperm based on viability; 2) manipulation and removal of the cumulus cells' narrow channel regions combined with microfluidics; 3) advances in oocyte positioning precision through the use of joystick-controlled micromanipulators; 4) microfluidics allowing the gradual change of a culture medium, which might result in better embryo development as well as reduce the amount of embryo manipulation; 5) time-lapse, proteomic, and metabolic scoring of the developing embryo, allowing multiple and optimized selection of the embryos. The technologies described in this review have not yet reported reliable clinical proofs.

CONCLUSION(S)

We already have available some of the technologies described, but we envisage an integrated device, i.e., an IVF lab-on-a-chip, by which oocyte and sperm would be processed to achieve a perfect embryo ready to be delivered into the uterus. With such a device, sample preparation, chemical or biologic reactions, and data collection would be integrated.