Translational and rotational manipulation of filamentous cells using optically driven microrobots.

Optical cell manipulation has become increasingly valuable in cell-based assays. In this paper, we demonstrate the translational and rotational manipulation of filamentous cells using multiple cooperative microrobots automatically driven by holographic optical tweezers. The photodamage of the cells due to direct irradiation of the laser beam can be effectively avoided. The proposed method will enable fruitful biomedical applications where precise cell manipulation and less photodamage are required.

Magnetic Soft Catheter Robot System for Minimally Invasive Treatments of Articular Cartilage Defects.

Articular cartilage defects are among the most common orthopedic diseases, which seriously affect patients' health and daily activities, without prompt treatment. The repair biocarrier-based treatment has shown great promise. Total joint injection and open surgery are two main methods to deliver functional repair biocarriers into the knee joint. However, the exhibited drawbacks of these methods hinder their utility. The repair effect of total joint injection is unstable due to the low targeting rate of the repair biocarriers, whereas open surgery causes serious trauma to patients, thereby prolonging the postoperative healing time. In this study, we develop a magnetic soft catheter robot (MSCR) system to perform precise in situ repair of articular cartilage defects with minimal incision. The MSCR processes a size of millimeters, allowing it to enter the joint cavity through a tiny skin incision to reduce postoperative trauma. Meanwhile, a hybrid control strategy combining neural network and visual servo is applied to sequentially complete the coarse and fine positioning of the MSCR on the cartilage defect sites. After reaching the target, the photosensitive hydrogel is injected and anchored into the defect sites through the MSCR, ultimately completing the in situ cartilage repair. The in vitro and ex vivo experiments were conducted on a 3D printed human femur model and an isolated porcine femur, respectively, to demonstrate the potential of our system for the articular cartilage repair.

Applying combined optical tweezers and fluorescence microscopy technologies to manipulate cell adhesions for cell-to-cell interaction study.

Cell-to-cell interactions are important for the regulation of various cell activities, such as proliferation, differentiation, and apoptosis. This paper presents an approach to studying cell-to-cell interactions at a single-cell level through manipulating cell adhesions with optical tweezers. Experiments are performed on leukemia cancer cells and stromal cells to demonstrate the feasibility of this method. After the adhesion properties of leukemia cells on stromal cells are characterized, fluorescence intensity is used as a label to study the Wnt signaling pathway of leukemia cells. The activities of the Wnt signaling pathway of K562 cells on M210B4 and HS5 cells are examined based on fluorescence analysis. The reliability of the fluorescence imaging is confirmed through comparison with traditional flow cytometry analysis. The proposed approach will offer new avenues to investigate otherwise inaccessible mechanisms in cell-to-cell interactions.

Manipulating cell adhesions with optical tweezers for study of cell-to-cell interactions.

This paper presents an approach to manipulating cell adhesions using optical tweezers for cell-to-cell interactions at single cell level. A case study of investigating the adhesions between leukemia cells and bone marrow stromal cells is reported. First, the trapping force imposed on the cell is calibrated and the viability of leukemia cells after optical trapping is tested and verified. This is for demonstrating the feasibility of the proposed optical manipulation method. Second, properties of adhesions of leukemia cells K562 on stromal cells M210B4 from mouse and HS5 from human are characterized. Based on characterization results, we classify adhesions into three categories namely tightly adherent, loosely adherent or free suspending. Finally, the adhesion abilities of K562 on M210B4 and HS5 are changed by adding heparin into culture medium, which demonstrates the specificity of the adhesion. The important contribution of this paper lies in development of a dexterous cell manipulation method to characterize cell adhesion properties, which helps create a new opportunity to investigate cell-to-cell interactions at single cell level.

Automated transportation of single cells using robot-tweezer manipulation system.

Manipulation of biological cells becomes increasingly important in biomedical engineering to address challenge issues in cell-cell interaction, drug discovery, and tissue engineering. Significant demand for both accuracy and productivity in cell manipulation highlights the need for automated cell transportation with integrated robotics and micro/nano manipulation technologies. Optical tweezers, which use highly focused low-power laser beams to trap and manipulate particles at micro/nanoscale, have emerged as an essential tool for manipulating single cells. In this article, we propose to use a robot-tweezer manipulation system to solve the problem of automatic transportation of biological cells, where optical tweezers function as special robot end effectors. Dynamics equation of the cell in optical tweezers is analyzed. A closed-loop controller is designed for transporting and positioning cells. Experiments are performed on live cells to demonstrate the effectiveness of the proposed approach in effective cell positioning.