In vitro perforation of human epithelial carcinoma cell with antibody-conjugated biodegradable microspheres illuminated by a single 80 femtosecond near-infrared laser pulse

Pulsed laser interaction with small metallic and dielectric particles has been receiving attention as a method of drug delivery to many cells. However, most of the particles are attended by many risks, which are mainly dependent upon particle size. Unlike other widely used particles, biodegradable particles have advantages of being broken down and eliminated by innate metabolic processes. In this paper, the perforation of cell membrane by a focused spot with transparent biodegradable microspheres excited by a single 800 nm, 80 fs laser pulse is demonstrated. A polylactic acid (PLA) sphere, a biodegradable polymer, was used. Fluorescein isothiocyanate (FITC)-dextran and short interfering RNA were delivered into many human epithelial carcinoma cells (A431 cells) by applying a single 80 fs laser pulse in the presence of antibody-conjugated PLA microspheres. The focused intensity was also simulated by the three-dimensional finite-difference time-domain method. Perforation by biodegradable spheres compared with other particles has the potential to be a much safer phototherapy and drug delivery method for patients. The present method can open a new avenue, which is considered an efficient adherent for the selective perforation of cells which express the specific antigen on the cell membrane

Type synthesis of 6-DOF mobile parallel link mechanisms based on screw theory

Mobile parallel mechanisms (MPMs), which are parallel mechanisms with moveable bases, have previously been proposed to resolve the limited workspace of conventional parallel mechanisms. However, most previous studies on the subject focused on the kinematic analysis of some specific MPMs and did not discuss a type synthesis method for MPMs. With this in mind, we propose a screw theory-based type synthesis method to find out possible 6-degrees-of-freedom (DOF) MPM structures. In our proposed method, the 6-DOF mobility is divided into 3-DOF planar motion and 3-DOF spatial motion, both of which are realized by the transmitted planar motions of the driving units. Separately, the type synthesis of the entire MPM is divided into that of the driving unit and connecting chain. To realize 3-DOF spatial motion, two methods, applying singularity configuration and adding an additional chain, are proposed as ways to restrict undesired motions for the synthesis of the connecting chain. The driving unit is synthesized via the same type-synthesis method as the connecting chain by considering the driving unit as a planar mechanism. The method used to integrate the driving unit and the connecting chain was constructed based on whether the end pair of the connecting chain should be connected with the driving unit directly or driven by it through an actuating mechanism. As a result, 284 possible types of MPM structure are suggested and four examples of MPMs with six DOFs were synthesized to verify the feasibility of the proposed method

Human-powered vehicle capable of movement in the longitudinal and lateral directions

Human-powered vehicles, especially conventional wheelchairs, are essential tools for people with lower body disability. But their movement in a lateral direction is limited or impossible, which burdens users who want to change directions, especially in a narrow space. Thus, a human-powered vehicle that can move in a lateral direction is required. To move in any direction, many motor-driven omnidirectional vehicles have been proposed, but humans cannot manually power their mechanisms. To solve this problem, we are developing a human-powered vehicle, that is, driven by hands of the rider, that can move in both the longitudinal and lateral directions. This paper proposes such a vehicle, which has a mechanism to move in the lateral direction like people can do while walking. We designed it so that riders can operate its mechanism by analyzing the space reachable by the rider’s palms where they can effectively exert power. We constructed a prototype and conducted experiments to confirm that the vehicle moves as expected with relatively low effort. In the experiments, we confirmed the validity of vehicle operation by comparing the moving time of the vehicle with and without the lateral translation function for different travel distances and passage widths. Our results showed that the proposed vehicle moves more quickly or requires shorter moving distance in comparison with a conventional wheelchair because of the lateral movement function. In addition, we found that the threshold for utility of the function is whether the passage width is larger than the vehicle diagonal length

Laser-based molecular delivery and its applications in plant science

Lasers enable modification of living and non-living matter with submicron precision in a contact-free manner which has raised the interest of researchers for decades. Accordingly, laser technologies have drawn interest across disciplines. They have been established as a valuable tool to permeabilize cellular membranes for molecular delivery in a process termed photoinjection. Laser-based molecular delivery was first reported in 1984, when normal kidney cells were successfully transfected with a frequency-multiplied Nd:YAG laser. Due to the rapid development of optical technologies, far more sophisticated laser platforms have become available. In particular, near infrared femtosecond (NIR fs) laser sources enable an increasing progress of laser-based molecular delivery procedures and opened up multiple variations and applications of this technique. This review is intended to provide a plant science audience with the physical principles as well as the application potentials of laser-based molecular delivery. The historical origins and technical development of laser-based molecular delivery are summarized and the principle physical processes involved in these approaches and their implications for practical use are introduced. Successful cases of laser-based molecular delivery in plant science will be reviewed in detail, and the specific hurdles that plant materials pose will be discussed. Finally, we will give an outlook on current limitations and possible future applications of laser-based molecular delivery in the field of plant science

Posture Operating Method by Foot Posture Change and Characteristics of Foot Motion

The lower limbs of the human body actually can perform the multiple-degree-of-freedom motion, just like the upper limbs. This suggests the possibility for the lower limbs to be used in the operation of multiple-degree-of-freedom devices, such as a robot arm. With that point in mind, the present paper focuses on the foot motion and examines its characteristics under the situation in which the posture of the object is manipulated by the posture change of the foot. First, we investigated how well the foot of the operator moved in accordance with the intention of the operator in order to clarify the motion characteristics of the foot experimentally by measuring the foot motion with a motion capture system under the assumption that the operator manipulates an object in virtual space. The results showed that there are differences between the intended and actual foot motions, especially when the tilt angle change was accompanied by a rotation angle change, which might be because of the joints whose axes of motion are nonparallel to the foot coordinate system, such as the talocalcaneal joint or Chopart joint. Next, an operating system considering the motion characteristics of the foot was proposed, and an experiment to verify its effectiveness was conducted. When the proposed conversion formula was used to calculate the intended foot motion based on the actual foot motion, the operability improved with respect to the required time and path-following accuracy while manipulating an object to the target posture and with respect to subjective operability

Mobile parallel manipulator consisting of two nonholonomic carts and their path planning

Mobile manipulators are widely used to transport and manipulate objects in industrial settings. In this paper, we propose a mobile manipulator that consists of a parallel mechanism and two two-wheel-drive carts. The planar motions of the carts are transmitted to a platform through three screw pairs of the parallel mechanism, allowing the pose of the platform to be controlled by only four motors. Kinematic analysis for such a two-cart mobile manipulator gives a Jacobian matrix, reveals the effects of nonholonomic constraints, and demonstrates that the yaw angle of the platform must be limited to avoid singular and failure configurations, and that the pitch angle is quite sensitive to uncertainties. Based on these analysis results, we present a custom path planning method for the carts. This method provides a non-optimal but easily realizable path planning algorithm with low computational cost, since the complex constraint conditions of this two-cart mobile manipulator have little influence on the proposed path generation process. The path planning process consists of four steps. We describe the motions of the carts in each step and establish a path tracking control system for the carts. Some simulations are conducted to show the motions of the carts, investigate the changes in the pose of the platform, and quantitatively evaluate the sensitivity of the platform’s pitch angle. Moreover, we construct an experimental prototype and conduct experiments to verify the validity and usefulness of the proposed mechanism and path planning method

The lane-switch mechanism for nucleosome repositioning by DNA translocase

Translocases such as DNA/RNA polymerases, replicative helicases, and exonucleases are involved in eukaryotic DNA transcription, replication, and repair. Since eukaryotic genomic DNA wraps around histone octamers and forms nucleosomes, translocases inevitably encounter nucleosomes. A previous study has shown that a nucleosome repositions downstream when a translocase collides with the nucleosome. However, the molecular mechanism of the downstream repositioning remains unclear. In this study, we identified the lane-switch mechanism for downstream repositioning with molecular dynamics simulations and validated it with restriction enzyme digestion assays and deep sequencing assays. In this mechanism, after a translocase unwraps nucleosomal DNA up to the site proximal to the dyad, the remaining wrapped DNA switches its binding lane to that vacated by the unwrapping, and the downstream DNA rewraps, completing downstream repositioning. This mechanism may have broad implications for transcription through nucleosomes, histone recycling, and nucleosome remodeling