Comparative ecotoxicity assessment of magnetosomes and magnetite nanoparticles

Investigation of pharmacokinetics and immunogenicity of magnetosomes

Magnetosomes are iron oxide or iron sulphide nano-sized particles surrounded by a lipid bilayer synthesised by a group of bacteria known as magnetotactic bacteria (MTB). Magnetosomes have become a promising candidate for biomedical applications and could be potentially used as a drug-carrier. However, pharmacokinetics and immunogenicity of the magnetosomes have not been understood yet which preclude its clinical applications. Herein, we investigated the pharmacokinetics of magnetosomes including Absorption, Distribution, Metabolism, and Elimination (ADME) along with its immunogenicity in vitro and in vivo. The magnetosomes were conjugated with fluorescein isothiocyanate (Mag-FITC) and their conjugation was confirmed through fluorescence microscopy and its absorption in HeLa cell lines was evaluated using flow cytometry analysis. The results revealed a maximum cell uptake of 97% at 200 µg/mL concentration. Further, the biodistribution of Mag-FITC was investigated in vivo by a bioimaging system using BALB/c mice as a subject at different time intervals. The Mag-FITC neither induced death nor physical distress and the same was eliminated post 36 h of injection with meagre intensities left behind. The metabolism and elimination analysis were assessed to detect the iron overload which revealed that magnetosomes were entirely metabolised within 48-h interval. Furthermore, the histopathology and serum analysis reveal no histological damage with the absence of any abnormal biochemical parameters. The results support our study that magnetosomes were completely removed from the blood circulation within 48-h time interval. Moreover, the immunogenicity analysis has shown that magnetosomes do not induce any inflammation as indicated by reduced peaks of immune markers such as IL 1β, IL 2, IL 6, IL8, IFN γ, and TNF α estimated through Indirect ELISA. The normal behaviour of animals with the absence of acute or chronic toxicities in any organs declares that magnetosomes are safe to be injected. This shows that magnetosomes are benign for biological systems enrouting towards beneficial biomedical applications. Therefore, this study will advance the understanding and application of magnetosomes for clinical purposes.

Biosynthesis of magnetosome-nanobody complex in Magnetospirillum gryphiswaldense MSR-1 and a magnetosome-nanobody-based enzyme-linked immunosorbent assay for the detection of tetrabromobisphenol A in water

In this study, two mutant strains, TBC and TBC+, able to biosynthesize a novel functional magnetosome-nanobody (Nb), were derived from the magnetotactic bacteria Magnetospirillum gryphiswaldense MSR-1. The magnetosome-Nbs biosynthesized by TBC+ containing multi-copies of the Nb gene had a higher binding ability to an environmental pollutant, tetrabromobisphenol A (TBBPA), than those biosynthesized by TBC containing only one copy of the Nb gene. The magnetosome-Nbs from TBC+ can effectively bind to TBBPA in solutions with high capacity without being affected by a broad range of NaCl and methanol concentrations as well as pH. Therefore, a magnetosome-Nb-based enzyme-linked immunosorbent assay (ELISA) was developed and optimized for the detection of TBBPA, yielding a half-maximum signal inhibition concentration of 0.23 ng/mL and a limit of detection of 0.025 ng/mL. The assay was used to detect TBBPA in spiked river water samples, giving average recoveries between 90 and 120% and coefficients of variation of 2.5-6.3%. The magnetosome-Nb complex could be reused 4 times in ELISA without affecting the performance of the assay. Our results demonstrate the potential of magnetosome-Nbs produced by TBC+ as cost-effective and environment-friendly reagents for immunoassays to detect small molecules in environmental waters.

Comparative Toxicity Assessment of Eco-Friendly Synthesized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) in Plants and Aquatic Model Organisms

This study aimed to evaluate the toxicity of superparamagnetic iron oxide nanoparticles (SPIONs) synthesized by biogenic (BS) and chemical (CH) routes. The nanoparticles were characterized by X-ray diffraction (XRD), X-ray spectroscopy (XPS), atomic force microscopy (AFM), vibrating-sample magnetometry (VSM-SQUID), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The toxicity of SPIONs was evaluated using Artemia salina as model aquatic organisms and Raphanus sativus and Lactuca sativa as model plants to evaluate their phytotoxicity. The results obtained from XRD, XPS, and AFM confirmed the formation of spherical nanoparticles of 41.9 ± 1.00 nm (BS route) and 19.8 ± 0.47 nm (CH route). VSM-SQUID demonstrated the superparamagnetic behavior of both nanoparticles, and FT-IR provided evidence of the differences in the surface of SPIONs, suggesting the presence of phenolic compounds on the surface of BS-SPIONs. For the assays with Artemia salina, the results demonstrated (i) nonsignificant differences of BS-SPIONs in mortality rates, and (ii) significant toxicity (p < 0.05) was observed for CH-SPIONs at 300 and 400 mg L−1. The Raphanus sativa plant assay tests showed (i) BS-SPIONs and CH-SPIONs improved the root elongation of seedlings. However, BS-SPIONs demonstrated significant activity on root seedling elongation (p < 0.05) in the range of 300 mg L−1 to 600 mg L−1. To the best of our knowledge, this is the first report to compare the toxicity of chemically and biogenically synthesized SPIONs. In conclusion, although BS-SPIONs and CH-SPIONs present similar structures, their characteristics of magnetic saturation and surface structure are nonidentical, providing differences in their biological activity.

Preparation and characterisation of magnetosomes based drug conjugates for cancer therapy

The authors report a novel, effective and enhanced method of conjugating anticancer drug, paclitaxel and gallic acid with magnetosomes. Here, anticancer drugs were functionalised with magnetosomes membrane by direct and indirect (via crosslinkers: glutaraldehyde and 3-aminopropyltriethoxysilane) adsorption methods. The prepared magnetosome-drug conjugates were characterised by Fourier transform infrared, zeta potential, field-emission scanning electron microscope and thermogravimetric analysis/differential scanning calorimetry. The drug-loading efficiency and capacity were found to be 87.874% for paclitaxel (MP) and 71.3% for gallic acid (MG), respectively as calculated by ultraviolet spectroscopy and high-performance liquid chromatography. The drug release demonstrated by the diffusion method in phosphate buffer (PBS), showing a prolonged drug release for MP and MG, respectively. The cytotoxicity effect of the MP and MG displayed cytotoxicity of 69.71%, 55.194% against HeLa and MCF-7 cell lines, respectively. The reactive oxygen species, acridine orange and ethidium bromide and 4, 6-diamidino-2-phenylindole staining of the drug conjugates revealed the apoptotic effect of MP and MG. Further, the regulation of tumour suppressor protein, p53 was determined by western blotting which showed an upregulation of p53. Comparatively, the magnetosome-drug conjugates prepared by direct adsorption achieved the best effects on the drug-loading efficiency and the increased percentage of cancer cell mortality and the upregulation of P53. The proposed research ascertains that magnetosomes could be used as effective nanocarriers in cancer therapy.

Biological materials formed by Acidithiobacillus ferrooxidans and their potential applications

A variety of biological materials including schwertmannite, jarosite, iron-sulfur cluster (ISC) and magnetosomes can be produced by Acidithiobacillus ferrooxidans (A. ferrooxidans). Their possible formation mechanisms involved in iron transformation, iron transport, and electron transfer were proposed. The schwertmannite formation usually occurs under the pH of 2.0-3.51, and a lower or higher pH will promote jarosite to be produced. Available Fe2+ in the environment and the carrier proteins that can transport Fe2+ to the intracellular membranes of A. ferrooxidans play a critical role in the synthesis of magnetosomes and ISC. The potential applications of these biological materials were reviewed, including removal of heavy metal by schwertmannite, detoxification of toxic species by jarosite, the transference of electron and ripening the iron sulfur protein by ISC, and biomedical application of magnetosomes. Additionally, some perspectives for the molecular mechanisms of synthesis and regulation of these biomaterials were briefly described.

Magnetosome mediated oral Insulin delivery and its possible use in diabetes management

Our study investigates the effect of magnetosome mediated oral Insulin delivery on diabetic induced rat models. The study involves the development of Magnetosome-Insulin (MI) conjugates by direct and indirect (by means of PEG) coupling method and further characterized by microscopic and spectroscopic analysis. The in vivo oral delivery of magnetosome-Insulin conjugate against streptozotocin-induced rat models and its efficiency was investigated. The impact of MI showed a remarkable change in the reduction of FBG levels up to 65% than the standard (Insulin). Similarly, the serum parameters: triglycerides (43.81%), AST&ALT (39.4 and 57.2%), total cholesterol (43.8%) showed significant changes compared to the diabetic control. The histological results of MI treated rats were found similar to control rats. Thus, these significantly notable results on diabetic rats depicts that magnetosomes can be employed as a potential approach and a very promising alternative for the parenteral route of Insulin delivery.

Biomimetic Magnetoliposomes as Oxaliplatin Nanocarriers: In Vitro Study for Potential Application in Colon Cancer

Current chemotherapy for colorectal cancer (CRC) includes the use of oxaliplatin (Oxa), a first-line cytotoxic drug which, in combination with irinotecan/5-fluorouracil or biologic agents, increases the survival rate of patients. However, the administration of this drug induces side effects that limit its application in patients, making it necessary to develop new tools for targeted chemotherapy. MamC-mediated biomimetic magnetic nanoparticles coupled with Oxa (Oxa-BMNPs) have been previously demonstrated to efficiently reduce the IC₅₀ compared to that of soluble Oxa. However, their strong interaction with the macrophages revealed toxicity and possibility of aggregation. In this scenario, a further improvement of this nanoassembly was necessary. In the present study, Oxa-BMNPs nanoassemblies were enveloped in phosphatidylcholine unilamellar liposomes (both pegylated and non-pegylated). Our results demonstrate that the addition of both a lipid cover and further pegylation improves the biocompatibility and cellular uptake of the Oxa-BMNPs nanoassemblies without significantly reducing their cytotoxic activity in colon cancer cells. In particular, with the pegylated magnetoliposome nanoformulation (a) hemolysis was reduced from 5% to 2%, being now hematocompatibles, (b) red blood cell agglutination was reduced, (c) toxicity in white blood cells was eliminated. This study represents a truly stepforward in this area as describes the production of one of the very few existing nanoformulations that could be used for a local chemotherapy to treat CRC.

A Protein Corona Adsorbed to a Bacterial Magnetosome Affects Its Cellular Uptake

Purpose

It is well known that when exposed to human blood plasma, nanoparticles are predominantly coated by a layer of proteins, forming a corona that will mediate the subsequent cell interactions. Magnetosomes are protein-rich membrane nanoparticles which are synthesized by magnetic bacteria; these have gained a lot of attention owing to their unique magnetic and biochemical characteristics. Nevertheless, whether bacterial magnetosomes have a corona after interacting with the plasma, and how such a corona affects nanoparticle–cell interactions is yet to be elucidated. The aim of this study was to characterize corona formation around a bacterial magnetosome and to assess the functional consequences.

Methods

Magnetosomes were isolated from the magnetotactic bacteria, M. gryphiswaldense (MSR-1). Size, morphology, and zeta potential were measured by transmission electron microscopy and dynamic light scattering. A quantitative characterization of plasma corona proteins was performed using LC-MS/MS. Protein absorption was further examined by circular dichroism and the effect of the corona on cellular uptake was investigated by microscopy and spectroscopy.

Results

Various serum proteins were found to be selectively adsorbed on the surface of the bacterial magnetosomes following plasma exposure, forming a corona. Compared to the pristine magnetosomes, the acquired corona promoted efficient cellular uptake by human vascular endothelial cells. Using a protein-interaction prediction method, we identified cell surface receptors that could potentially associate with abundant corona components. Of these, one abundant corona protein, ApoE, may be responsible for internalization of the magnetosome-corona complex through LDL receptor-mediated internalization.

Conclusion

Our findings provide clues as to the physiological response to magnetosomes and also reveal the corona composition of this membrane-coated nanomaterial after exposure to blood plasma.