Attachment of Therapeutic and Imaging Agents to Flagellated Magneto-Aerotactic Bacteria Cells for Tumor Treatment and Targeting Purposes

Despite the significant progress in technology and in the biological understanding of cancer, there are still multiple challenges that slow down the development and implementation of certain treatment options in clinical trials. The researchers in the fields of drug delivery and tissue engineering are facing major problems. Some of these include the lack of a conventional and selective drug delivery and release system, the physiological barriers that the bloodborne antitumor agents encounter before reaching cancer cells in a solid tumor and sequestration of the drugs by the immune system that makes only a few percent of the total administered dose reaching the intended target site. Hence, there is a necessity for a frequent dosing to achieve the desired therapeutic effect, which can cause adverse side effects or sometimes even treatment failure. Furthermore, medical imaging is essential in cancer diagnosis and treatment. However, current medical imaging methods have limited use due to the structural complexity of the tumor and the limited penetration depth of the previously available contrast agents into tumor tissues. With recent developments, obtaining a high-resolution and detailed image of a tumor has been facilitated. The attachment of therapeutic and imaging nanosize agents to the magneto-aerotactic microorganisms known as BN-1 magnetotactic bacteria (MTB) for tumor targeting purposes has been studied during the accomplishment of this master's project. MTB microbiorobots appear to be ideal self-propelling and navigable targeting agents. They are capable of traveling against the Tumor Interstitial Fluid Pressure (TIFP) to target deep regions in solid tumors. MTB complexes were formulated by attaching to MTB (i) SN38 anticancer drug encapsulated liposomes (MTB-LP-SN38) and (ii) 200 nm fluidMAG-ARA superparamagnetic iron oxide magnetic nanoparticles (MTB-MNP). As the magnetic nanoparticles act as magnetic resonance imaging (MRI) contrast agents, MTB-MNP complexes facilitate monitoring the tumor structure and hypoxic zones while acting as feedback control in the MTB navigation operations. On one hand, the MTB-LP was developed by direct covalent conjugation of functionalized liposomes to amine (–NH2) groups that are naturally present on the surface of MTB bacteria, via carbodiimide-mediated coupling. On the other hand, the MTB-MNP was prepared via a two-step procedure. First, the magnetic nanoparticles were functionalized with the BN-1 antibody (AB) against the MTB protein surface using carbodiimide chemistry, then the MNP-AB were attached to the MTB. The LP, LP-SN38 and MTB-LP-SN38 samples were analyzed with liquid chromatography/mass spectroscopy (LC/MS), UV-Spectroscopy, dynamic light scattering (DLS) and zeta potential (ZP). In addition, the attachment efficiency, alignment in the magnetic field and average swimming velocity of the MTB-MNP samples submitted to an external magnetic field were investigated. Subsequently, results showed that MTB bacteria cells are capable of carrying sufficient therapeutic and imaging agents without altering their natural swimming capability.