Collaboration between Professor Liang Fang Zhang and Professor Joseph Wang, University of California, San Diego: new cell hybrid micromotor

In recent years, more and more attention has been paid to micromotors which can transform energy into power and then move At present, micromotors have been used in drug delivery, surgical navigation, biosensor, toxin removal and other fields Among them, the micro motor based on magnesium can drive itself in gastrointestinal fluid, transport drugs and release drugs, rapid biodegradation and other properties, which has unique advantages in vivo application At present, it has been used in gastrointestinal drug delivery, antigen delivery and so on Different from the early fully synthesized micromotors, recently some researches began to integrate cell components and synthetic materials to form hybrid motors with biological functions: One is to use the inherent movement characteristics of cells (such as sperm, bacteria, cardiomyocytes, etc.) to deliver the drugs carried by artificial materials The other is to combine the materials from cells (such as cell membrane) with the synthetic motor, and use the movement ability of the synthetic motor to deliver the drugs Considering the unique advantages of cell carriers in drug delivery, integrating the whole cell with the synthesized micro motor with good biocompatibility and biodegradability will produce hybrid motor system that can be used in vivo Based on this, recently, Professor Liang Fang Zhang of the University of California, San Diego, and Professor Joseph Wang cooperated to develop a m Φ mg hybrid motor based on macrophage (m Φ) and magnesium (mg) micromotor, which has the motion characteristics of Mg motor and the function of removing bacterial toxins by M Φ The related research results were published on adv mater., entitled "a macrophase – magnesiumhybrid robot: fabric and characterization" (DOI: 10.1002 / ADMA 201901828) This hybrid motor consists of Mg motor and m Φ (Figure 1) Firstly, Mg micro particles were synthesized, and then a layer of asymmetric TiO 2 and poly-L-lysine (PLL) was coated on the surface of Mg micro particles in turn Because a part of Mg was not covered and exposed to the outside, it can react with the acid and release gas to make the motor move Then, the motors and macrophages were incubated in a 4 ℃ medium for 1 h, and the hybrid motors were formed by the interaction of M Φ and the motors The morphology and element distribution of M Φ - Mg hybrid motor were analyzed by SEM and EDX, and its movement performance was verified in the simulated gastric juice The results showed that its movement time could reach several minutes, and the average speed was 127.3 μ M / s Through the imaging of hybrid motors with different sizes after incubation in simulated gastric juice for different times (Figure 2), the author found that after 3 minutes, the motor basically stopped moving, and the motor part became transparent, because mg was consumed by reaction, making the middle cavity The motion of hybrid motor is analyzed theoretically The results show that the speed of hybrid motor increases with the size of Mg motor When the size of M Φ is much larger than that of Mg motor, m Φ will engulf mg motor, so it can't move When the size of M Φ is much smaller than mg particle, the motion performance of hybrid motor is equal to that of Mg motor The theoretical calculation is also verified by experiments The results show that the speed of hybrid motor of 20-25 μ m is faster than that of hybrid motor of 10-15 μ m, and the speed of hybrid motor is smaller than that of Mg motor (photo source: adv mater.) in order to further detect the influence of the size of Mg motor on the performance of hybrid motor, the author uses PS particles with different sizes labeled by FITC to simulate mg motor and incubate with m Φ The results show that PS smaller than 5 μ m will be engulfed by M Φ, while PS larger than 10 μ m will adhere to m Φ to form hybrid motor (Figure 3) Therefore, in order to form hybrid motor, the ideal particle size of Mg motor should be greater than 5 μ M (photo source: adv mater.) next, the author verified the biological activity of M Φ on hybrid motor by calophyll and Alexa fluor594 labeled LPS Fluorescence imaging showed that m Φ adhered to Mg motor, which did not affect the activity of M Φ, and the performance of M Φ combined with LPS was not significantly affected (Figure 4) Through the observation of different time, the author found that these adhered m Φ could maintain its biological activity in gastric juice for up to 4 hours These results show that the formation of hybrid motor does not affect the survival of M Φ and the functional protein on its surface Finally, the ability of the hybrid motor to remove LPS secreted by E.coli was studied by in vitro binding and neutralization experiments The authors found that in the acid medium, with the extension of time, the hybrid motor can remove more toxins, and can remove ~ 66.82% of the toxins within 5 minutes, 13% higher than m Φ (Figure 5) This is because the hybrid motor can move in the solution, increasing the chance of contact between M Φ and LPS (photo source: adv mater.) as a conceptual research, a new cell hybrid micromotor was developed in this paper The experiments were carried out with m Φ and Mg motors as cell and motor models respectively The experimental results show that the electrostatic interaction between them will not affect the cell activity and biological function Due to the motor's performance, the hybrid motor has a better ability to remove bacterial toxins in acid condition than m Φ In addition, the hybrid system can be composed of other cells and motors to achieve other special functions.