Magnetotactic bacteria for cancer therapy

Abstract

Magnetotactic bacteria (MTB) are aquatic microorganisms that are able to biomineralize membrane-enclosed magnetic nanoparticles called magnetosomes. Inside the MTB, magnetosomes are arranged in a chain that allows MTB to align and navigate along the Earth's magnetic field. When isolated from the MTB, magnetosomes display a number of potential applications for targeted cancer therapies, such as magnetic hyperthermia, localized drug delivery, or tumor monitoring. The characteristics and properties of magnetosomes for these applications exceed in several aspects those of synthetic magnetic nanoparticles. Likewise, the whole MTB can also be considered as promising agents for cancer treatment, taking advantage of their self-propulsion capability provided by their flagella and the guidance capabilities ensured by their magnetosome chain. Indeed, MTB are envisaged as nanobiots that can be guided and manipulated by external magnetic fields and are naturally attracted toward hypoxic areas, such as the tumor regions, while retaining the therapeutic and imaging capacities of the isolated magnetosomes. Moreover, unlike most of the bacteria currently tested in clinical trials for cancer therapy, MTB are not pathogenic but could be engineered to deliver and/or express specific cytotoxic molecules. In this article, we will review the progress and perspectives of this emerging research field and will discuss the main challenges to overcome before the use of MTB can be successfully applied in the clinic.

Magnetospirillum magneticum as a Living Iron Chelator Induces TfR1 Upregulation and Decreases Cell Viability in Cancer Cells

“…These challenges might be overcome by implementing bacteria as direct competitors for nutrients at the tumor site. Several approaches have been investigated in the past to deliver magnetotactic bacteria to solid tumors [ 44 ]. For example, intravenously introduced AMB-1 have been shown to colonize 293T tumor xenografts 3–6 days after injection [ 41 ] without external magnetic guidance and act as a local T2-weighted contrast imaging agent.…”

“…Further application could include the use of tumor-targeting organisms both as a monotherapy and as a combination therapy with established antineoplastic drugs to obtain optimal clinical outcomes. Although MTB are considered as non-pathogenic, unlike most of the bacteria currently tested for cancer therapy, they have been rarely studied in vivo until now and more studies are required to advance the knowledge about their adaptability to different environments and conditions in vivo [ 44 ]. However, the unique characteristics of magnetotactic bacteria could also be exploited to engineer iron-scavenging strains of surrogate commensal and attenuated bacteria that have already been established as anticancer agents [ 3 , 7 ].…”

Magnetotactic Bacteria and Magnetosomes: Basic Properties and Applications

“…At the same time, other possible biomedical applications of MTB include magnetically guided drug delivery, alternate magnetic field (AMF) hyperthermia, magnetic resonance imaging (MRI) or magnetic particle imaging (MPI) and modification of MTB membrane with drugs or superparamagnetic iron oxide-based nanoparticles (SPIONs). Reprinted from [181], J. Appl. Phys., Vol.…”

Iron Oxide Nanorings and Nanotubes for Magnetic Hyperthermia: The Problem of Intraparticle Interactions

“…Since it was proposed by Gilchrist et al in 1957 [ 5 ], the technique has progressively advanced and nowadays there are already a few clinical trials being carried out in different hospitals around the world [ 3 , 6 ]. In addition, in the last years, different strategies have been devised to improve the theranostic efficiency of these nano-agents such as combining magnetic hyperthermia and photothermia in magneto-plasmonic nanostructures or using magneto-mechanical actuation for further disrupting the cancer cells [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Despite a large number of advancements in the field, there are still several issues that warrant further studies such as improving the delivery efficiency of the MNPs to the tumor or optimizing the heating efficiency (i.e., the specific absorption rate, SAR) of the MNPs.…”