for various fields, such as drug delivery, [1,2] biosensing, [3] detoxification, [4] and environmental remediation. [5] These miniaturized machines can convert local fuel or external energy (e.g., magnetic, ultrasound, or light) to driving force and obtain selfpropulsion in dynamic surroundings. [6] Due to the increasing demands and rigorous requirements of biomedical community, the composition of microrobots has been evolving from rigid and inorganic materials to functional and endogenous cells. [7] Incorporating natural cells with synthetic micromachines creates an elegant platform with synergistic properties of cell biofunctionalities and effective propulsion. The cargo-loading capability of cells is employed by cell-based microrobots to actively deliver drugs, [2,[8][9][10][11] such as red blood cell (RBC)based micromotors loaded with doxorubicin (DOX) and photosensitizer, [10,11] and neutrophil-based microrobots carrying paclitaxel (PTX). [2] However, the utilized chemotherapeutic agents in the robotic system are not specific to cancerous cells and occur drug leakage during transport, inducing unavoidable toxicity to normal regions along with limited therapeutic efficacy and undesired side effects. [12] Such compromised biosafety and antitumor index hinder the practical A unique robotic medical platform is designed by utilizing cell robots as the active "Trojan horse" of oncolytic adenovirus (OA), capable of tumor-selective binding and killing. The OA-loaded cell robots are fabricated by entirely modifying OA-infected 293T cells with cyclic arginine-glycine-aspartic acid tripeptide (cRGD) to specifically bind with bladder cancer cells, followed by asymmetric immobilization of Fe 3 O 4 nanoparticles (NPs) on the cell surface. OA can replicate in host cells and induce cytolysis to release the virus progeny to the surrounding tumor sites for sustainable infection and oncolysis. The asymmetric coating of magnetic NPs bestows the cell robots with effective movement in various media and wireless manipulation with directional migration in a microfluidic device and bladder mold under magnetic control, further enabling steerable movement and prolonged retention of cell robots in the mouse bladder. The biorecognition of cRGD and robust, controllable propulsion of cell robots work synergistically to greatly enhance their tissue penetration and anticancer efficacy in the 3D cancer spheroid and orthotopic mouse bladder tumor model. Overall, this study integrates cell-based microrobots with virotherapy to generate an attractive robotic system with tumor specificity, expanding the operation scope of cell robots in biomedical community.

BackgroundNanosized bacterial outer membrane vesicles (OMVs) secreted by Gram-negative bacteria have emerged as a novel antitumor nanomedicine reagent due to their immunostimulatory properties. The encapsulated bacterial composition in OMVs can be edited via manipulating bioengineering technology on paternal bacteria, allowing us to design an ingenious antitumor platform by loading the Polybia–mastoparan I (MPI) fusion peptide into OMVs.MethodsOMVs containing the MPI fusion peptide were obtained from bioengineered Escherichia coli transformed with recombinant plasmid. The antitumor efficacy of bioengineered OMVs in vitro was verified by performing cell viability and wound-healing and apoptosis assays using MB49 and UMUC3 cells, respectively. Subcutaneous MB49 tumor-bearing mice were involved to investigate the tumor inhibition ability of bioengineered OMVs. Moreover, the activated immune response in tumor and the biosafety were also evaluated in detail.ResultsThe resulting OMVs had the successful encapsulation of MPI fusion peptides and were subjected to physical characterization for morphology, size, and zeta potential. Cell viabilities of bladder cancer cells including MB49 and UMUC3 rather than a non-carcinomatous cell line (bEnd.3) were decreased when incubated with bioengineered OMVs. In addition, bioengineered OMVs restrained migration and induced apoptosis of bladder cancer cells. With intratumor injection of bioengineered OMVs, growths of subcutaneous MB49 tumors were significantly restricted. The inherent immunostimulation of OMVs was demonstrated to trigger maturation of dendritic cells (DCs), recruitment of macrophages, and infiltration of cytotoxic T lymphocytes (CTLs), resulting in the increased secretion of pro-inflammatory cytokines (IL-6, TNF-α, and IFN-γ). Meanwhile, several lines of evidence also indicated that bioengineered OMVs had satisfactory biosafety.ConclusionBioengineered OMVs fabricated in the present study were characterized by strong bladder cancer suppression and great biocompatibility, providing a new avenue for clinical bladder cancer therapy.