We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ∼25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment.

We report controlled migrations of an intelligent and biocompatible “iMushbot” composed of Agaricus bisporus, mushroom microcapsules coated with magnetite nanoparticles. The otherwise randomly moving microbot could meticulously direct itself toward and away from the acid- and alkali-rich regions with the help of acid, acidic catalase, and alkali stimuli, emulating the chemotaxis of microorganisms. Although the catalytic decomposition of peroxide-fuel in alkali engendered the directed alkali taxis toward higher pH region, decomposition of peroxide fuel by the acidic catalase activity led to directed acid taxis toward the lower pH region. The presence of magnetite nanoparticles not only helped in improving the “activity” of the motor through the heterogeneous catalytic decomposition of the peroxide fuel but also provided a remote magnetic control on the chemotaxis. The mesoporous iMushbots having negative ζ-potential could easily be loaded with the cationic anticancer drugs, which were magnetically guided toward the cancerous cells to cause apoptosis. The iMushbots exhibited higher degree of drug retaining capacity inside alkaline pH and showed facile drug release preferentially in the lower pH environments. The experiments show the potential of the iMushbots in retaining and transporting drugs in alkaline medium such as human blood and releasing them in acidic medium such as the cancerous tissues for cell apoptosis.

We report a two-photon responsive drug delivery system (DDS) namely, p-hydroxyphenacyl-naphthalene-chlorambucil (pHP-Naph-Cbl) having two-photon absorption (TPA) cross-section of ≥ 20 GM in the phototherapeutic window (700 nm). Our DDS exhibited...

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Treatment of persistent biofilm infections has turned out to be a formidable challenge even with broad-spectrum antibiotic therapies. In this direction, intelligent micromachines may serve as active mechanical means to dislodge such deleterious bacterial communities. Herein, we have designed biocompatible micromotors from tea buds, namely, T-Budbots, which shows the capacity to be magnetically driven on a biofilm matrix and remove or fragment biofilms with precision, as a part of the proposed non-invasive "Kill-n-Clean" strategy. In a way, we present a bactericidal robotic platform decorated with magnetite nanoparticles aimed at clearing in vitro biofilms present on the surfaces. We have also shown that the smart porous T-Budbots can integrate antibiotic ciprofloxacin due to electrostatic interaction on their surface to increase their antibacterial efficacy against dreadful pathogenic bacterial communities of Pseudomonas aeruginosa and Staphylococcus aureus. It is noteworthy that the release of this drug can be controlled by tuning the surrounding pH of the T-Budbots. For example, while the acidic environment of the biofilm facilitates the release of antibiotics from the porous T-Budbots, the drug release was rather minimal at higher pH. The work represents a first step in the involvement of a plant-based microbot exhibiting magneto-robotic therapeutic properties, providing a non-invasive and safe approach to dismantle harmful biofilm infections.