Mobile microrobots offer great promise for minimally invasive targeted medical theranostic applications at hard-to-access regions inside the human body. The circulatory system represents the ideal route for navigation; however, blood flow impairs propulsion of microrobots especially for the ones with overall sizes less than 10 micrometers. Moreover, cell- and tissue-specific targeting is required for efficient recognition of disease sites and long-term preservation of microrobots under dynamic flow conditions. Here, we report cell-sized multifunctional surface microrollers with ~3.0 and ~7.8-micrometer diameters, inspired by leukocytes in the circulatory system, for targeted drug delivery into specific cells and controlled navigation inside blood flow. The leukocyte-inspired spherical microrollers are composed of magnetically responsive Janus microparticles functionalized with targeting antibodies against cancer cells (anti-HER2) and light-cleavable cancer drug molecules (doxorubicin). Magnetic propulsion and steering of the microrollers resulted in translational motion speeds up to 600 micrometers per second, around 76 body lengths per second. Targeting cancer cells among a heterogeneous cell population was demonstrated by active propulsion and steering of the microrollers over the cell monolayers. The multifunctional microrollers were propelled against physiologically relevant blood flow (up to 2.5 dynes per square centimeter) on planar and endothelialized microchannels. Furthermore, the microrollers generated sufficient upstream propulsion to locomote on inclined three-dimensional surfaces in physiologically relevant blood flow. The multifunctional microroller platform described here presents a bioinspired approach toward in vivo controlled propulsion, navigation, and targeted active cargo delivery in the circulatory system.

移动微型机器人为在人体内部难以接近的区域以最小侵入性为目标的医疗治疗方法提供了广阔的前景。循环系统代表了理想的航行路线；但是，血流会阻碍微型机器人的推进，尤其是对于整体尺寸小于10微米的微型机器人。此外，细胞和组织特异性靶向是有效识别疾病部位和在动态流动条件下长期保存微型机器人所必需的。在这里，我们报告了受循环系统中白细胞启发的直径约3.0微米和〜7.8微米的细胞大小的多功能表面微辊，用于将药物靶向递送至特定细胞并控制血流中的导航。受白细胞启发的球形微辊由磁响应的Janus微粒组成，该微粒具有针对癌细胞（抗HER2）和光可裂解的癌症药物分子（阿霉素）的靶向抗体功能。微型滚筒的磁性推进和操纵导致平移运动速度高达每秒600微米，大约每秒76体长。通过在细胞单层上微辊的主动推进和操纵，证明了在异质细胞群体中靶向癌细胞。多功能微辊在平面和内皮化微通道上被推进以抵抗生理相关的血流（每平方厘米高达2.5达因）。此外，微型滚筒产生了足够的上游推动力，可以在生理相关的血流中在倾斜的三维表面上运动。此处描述的多功能微辊平台为循环控制系统中的体内控制推进，导航和目标主动货物输送提供了一种生物启发的方法。