Bacteria-Templated and Dual Enzyme-Powered Microcapsule Motors To Promote Thrombus Penetration and Thrombolytic Efficacy.

Antithrombotic therapy is confronted with short half-lives of thrombolytic agents and high bleeding risks. Challenges remain in the development of drug delivery systems for thorough destruction of thrombi and timely restoration of blood flow while minimizing side effects. Herein, polydopamine capsule-like micromotors with urokinase (uPA) loadings and Arg-Gly-Asp (RGD) grafts (r-u@PCM) were constructed using rod-shaped bacteria as the template, and one single opening was created on each capsule through bacterial ghost (BG) formation. Glucose oxidase and catalase were encapsulated in the large cavity of microcapsules, and their successive oxidation of glucose produced O2 bubbles, which ejected out through the single opening to propel the motion of r-u@PCM. In vitro targeting testing of r-u@PCM shows significant higher accumulations on the activated platelets than those without RGD grafts (u@PCM, 7 folds) or without enzyme loadings (r-u@PC, 11 folds). Compared with the major distribution of r-u@PC on the clot surface, r-u@PCM efficiently penetrates into clots with dense fibrin networks, and near-infrared (NIR) irradiation (r-u@PCM/NIR) promotes thrombus infiltration through increasing uPA release and thermolysis of the networks. Pharmacokinetic study shows that the loading of uPA in r-u@PCM extends the terminal half-life from 24 min to 5.5 h and the bioavailability increased 13 times. In a hindlimb venous thrombosis model, r-u@PCM/NIR treatment promotes uPA accumulations in thrombi and disrupts all the thrombi after 8 h with a full recovery of blood flows. Effective thrombolysis is also achieved even after reducing the uPA dose 5 times. Thus, this is the first attempt to fabricate rod-shaped microcapsule motors through a biologically derived method, including bacterial templating and BG formation-induced opening generation. r-u@PCM/NIR treatment promotes thrombolysis through the photothermal effect, self-propelled infiltration into thrombi, and accelerated local release of uPA, providing a prerequisite for reducing uPA dose and bleeding side effects.

Bacteria-propelled microtubular motors for efficient penetration and targeting delivery of thrombolytic agents.

Effective thrombolysis is critical to rapidly rebuild blood flow for thrombosis patients. Drug delivery systems have been developed to address inadequate pharmacokinetics of thrombolytic agents, but challenges still remain in the timely removal of blood clots regarding the dense fibrin networks. Herein, rod-shaped tubular micromotors were developed to achieve efficient penetration and thorough destruction of thrombi. By using electrospun fiber fragments as the template, urokinase (uPA)-loaded polydopamine (PDA) microtubes with surface decorated fucoidan (FuPDAuPA) were prepared at the aspect ratio of around 2. One E. coli Nissle 1917 (EcN) was assembled into one microtube to construct a FuPDAuPA@EcN hybrid micromotor through PDA adhesion and L-aspartate induction. The pharmacokinetic analysis indicates that the encapsulation of uPA into micromotors extends the half-life from 0.4 to 5.6 h and increases the bioavailability over 10 times. EcN-propelled motion elevates adsorption capacities of FuPDAuPA@EcN for more than four times compared with that of FuPDAuPA. The fucoidan-mediated targeting causes 2-fold higher thrombolysis capacity in vitro and over 10-fold higher uPA accumulation in thrombi in vivo. In the treatment of venous thrombi at mouse hindlimbs, intravenous administration of FuPDAuPA@EcN completely removed blood clots with almost full recovery of blood flows and apparently alleviated tail bleeding. It should be noted that FuPDAuPA@EcN treatment at a reduced uPA dose caused no significant difference in the blood flow rate compared with those of FuPDAuPA. The synergistic action of fucoidan-induced targeting and EcN-driven motion provides a prerequisite for promoting thrombolytic efficacy and reducing uPA dose and bleeding side effect. STATEMENT OF SIGNIFICANCE: The standard treatment to thrombosis patient is intravenous infusion of thrombolytic agents, but the associated bleeding complications and impairment of normal haemostasis greatly offset the therapeutic benefits. Drug delivery systems have been developed to address the limitations of inadequate pharmacokinetics of thrombolytic agents, but challenges still exist in less efficient penetration into dense networks for thorough destruction of thrombi. Up to now only few attempts have been made to construct nano-/micromotors for combating thrombosis and there is no single case that antithrombosis is assisted by bacteria or cells-propelled motors. Herein, bacteria-propelled microtubes were developed to carry urokinase for efficient penetration into blood clots and effective thrombolysis. The synergistic action of bacteria-driven motion and specific ligand-induced targeting holds a promising treatment strategy for life-threatening cardiovascular diseases such as thrombosis and atherosclerosis.

Doxorubicin-conjugated Escherichia coli Nissle 1917 swimmers to achieve tumor targeting and responsive drug release.

The use of bacteria as drug carriers meets several challenges, such as biocompatibility, motility deterioration after drug loading and lack of in vivo verification. Escherichia coli Nissle 1917 (EcN) is one of the best studied probiotic strains, and doxorubicin (DOX) is conjugated onto EcN in the current study via acid-labile linkers of cis-aconitic anhydride (EcN-ca-Dox), realizing the bacteria-directed accumulation and acid-responsive release of anticancer drugs in tumors. The drug conjugation has maintained the bacterial motion profiles of over 9µm/s and cell viability of over 70%. After 3h and 3days of intravenous injection of EcN-ca-Dox, DOX accumulations in tumors are determined as 12.9% and 6.4% of the injected doses per gram of tissue, respectively, which are much higher than the commonly used nanocarriers. Compared with free DOX and DOX-conjugated EcN via stable linkers of succinic anhydride, the EcN-ca-Dox treatment improves the antitumor efficacy with respect to the tumor growth inhibition, prolongation of animal survivals, and apoptosis induction of tumor cells. In addition, EcN has been cleaned off from tumors and other tissues after antimicrobial treatment. Thus, the acid-labile EcN conjugates provide a safe and concise strategy to enhance the temporal and spatial controllability of anticancer drugs.