Bacterial magnetic particles as a novel and efficient gene vaccine delivery system

Cancer Nanovaccines: Nanomaterials and Clinical Perspectives

Cancer nanovaccines represent a promising frontier in cancer immunotherapy, utilizing nanotechnology to augment traditional vaccine efficacy. This review comprehensively examines the current state-of-the-art in cancer nanovaccine development, elucidating innovative strategies and technologies employed in their design. It explores both preclinical and clinical advancements, emphasizing key studies demonstrating their potential to elicit robust anti-tumor immune responses. The study encompasses various facets, including integrating biomaterial-based nanocarriers for antigen delivery, adjuvant selection, and the impact of nanoscale properties on vaccine performance. Detailed insights into the complex interplay between the tumor microenvironment and nanovaccine responses are provided, highlighting challenges and opportunities in optimizing therapeutic outcomes. Additionally, the study presents a thorough analysis of ongoing clinical trials, presenting a snapshot of the current clinical landscape. By curating the latest scientific findings and clinical developments, this study aims to serve as a comprehensive resource for researchers and clinicians engaged in advancing cancer immunotherapy. Integrating nanotechnology into vaccine design holds immense promise for revolutionizing cancer treatment paradigms, and this review provides a timely update on the evolving landscape of cancer nanovaccines.

Magnetosomes as Potential Nanocarriers for Cancer Treatment

Magnetotactic bacteria (MTBs) and their organelles, magnetosomes, are intriguing options that might fulfill the criteria of using bacterial magnetosomes (BMs). The ferromagnetic crystals contained in BMs can condition the magnetotaxis of MTBs, which is common in water storage facilities. This review provides an overview of the feasibility of using MTBs and BMs as nanocarriers in cancer treatment. More evidence suggests that MTBs and BMs can be used as natural nanocarriers for conventional anticancer medicines, antibodies, vaccine DNA, and siRNA. In addition to improving the stability of chemotherapeutics, their usage as transporters opens the possibilities for the targeted delivery of single ligands or combinations of ligands to malignant tumors. Magnetosome magnetite crystals are different from chemically made magnetite nanoparticles (NPs) because they are strong single-magnetic domains that stay magnetized even at room temperature. They also have a narrow size range and a uniform crystal morphology. These chemical and physical properties are essential for their usage in biotechnology and nanomedicine. Bioremediation, cell separation, DNA or antigen regeneration, therapeutic agents, enzyme immobilization, magnetic hyperthermia, and contrast enhancement of magnetic resonance are just a few examples of the many uses for magnetite-producing MTB, magnetite magnetosomes, and magnetosome magnetite crystals. From 2004 to 2022, data mining of the Scopus and Web of Science databases showed that most research using magnetite from MTB was carried out for biological reasons, such as in magnetic hyperthermia and drug delivery.

Oncolytic virus delivery modulated immune responses toward cancer therapy: Challenges and perspectives

Oncolytic viruses (OVs) harness the hallmarks of tumor cells and cancer-related immune responses for the lysis of malignant cells, modulation of the tumor microenvironment, and exertion of vaccine-like activities. However, efficient clinical exploitation of these potent therapeutic modules requires their systematic administration, especially against metastatic and solid tumors. Therefore, developing methods for shielding a virus from the neutralizing environment of the bloodstream while departing toward tumor sites is a must. This paper reports the latest advancements in the employment of chemical and biological compounds aimed at safe and efficient delivery of OVs to target tissues or tumor deposits within the host.

Bacteria and cells as alternative nano-carriers for biomedical applications

INTRODUCTION

Nano-based systems have received a lot of attention owing to their particular properties and, hence, have been proposed for a wide variety of biomedical applications. These nanosystems could be potentially employed for diagnosis and therapy of different medical issues. Although these nanomaterials are designed for specific tasks, interactions, and transformations when administered to the human body affect their performance and behavior. In this regard, bacteria and other cells have been presented as alternative nanocarriers. These microorganisms can be genetically modified and customized for a more specific therapeutic action and, in combination with nanomaterials, can lead to bio-hybrids with a unique potential for biomedical purposes.

AREAS COVERED

Literature regarding bacteria and cells employed in combination with nanomaterials for biomedical applications is revised and discussed in this review. The potential as well as the limitations of these novel bio-hybrid systems are evaluated. Several examples are presented to show the performance of these alternative nanocarriers.

EXPERT OPINION

Bio-hybrid systems have shown their potential as alternative nanocarriers as they contribute to better performance than traditional nano-based systems. Nevertheless, their limitations must be studied, and advantages and drawbacks assessed before their application to medicine.

Why Does Not Nanotechnology Go Green? Bioprocess Simulation and Economics for Bacterial-Origin Magnetite Nanoparticles

Nanotechnological developments, including fabrication and use of magnetic nanomaterials, are growing at a fast pace. Magnetic nanoparticles are exciting tools for use in healthcare, biological sensors, and environmental remediation. Due to better control over final-product characteristics and cleaner production, biogenic nanomagnets are preferable over synthetic ones for technological use. In this sense, the technical requirements and economic factors for setting up industrial production of magnetotactic bacteria (MTB)-derived nanomagnets were studied in the present work. Magnetite fabrication costs in a single-stage fed-batch and a semicontinuous process were US$ 10,372 and US$ 11,169 per kilogram, respectively. Depending on the variations of the production process, the minimum selling price for biogenic nanomagnets ranged between US$ 21 and US$ 120 per gram. Because these prices are consistently below commercial values for synthetic nanoparticles, we suggest that microbial production is competitive and constitutes an attractive alternative for a greener manufacturing of magnetic nanoparticles nanotools with versatile applicability.

Magnetically Navigated Protein Transduction In Vivo using Iron Oxide-Nanogel Chaperone Hybrid

Systems for "protein transduction," intracellular delivery of functional proteins, are needed to address deliverability challenges of protein therapeutics. However, in vivo protein transduction remains challenging because of instability in serum, extracellular protease digestion and rapid excretion from the bloodstream. Here, a magnetically guided in vivo protein transduction using magnetic nanogel chaperone (MC) composed of iron oxide nanoparticles and a polysaccharide nanogel, a protein carrier inspired by "catch and release" mechanisms of molecular chaperones is demonstrated. The MC system enables efficient delivery of anti-cancer proteins, saporin and RNaseA, into cultured tumor lines and inhibits cell proliferation, mainly via apoptosis. Magnetic in vivo protein transduction via intravenous whole body administration is demonstrated in a fibrosarcoma model. By in vivo optical imaging, MC accumulated in tumor tissues under magnetic field three times more than without irradiation. With subcutaneous injection, saporin is delivered by MC to the cytoplasm in magnetically targeted tissues. In an oral cancer model, MC-delivered magnetically targeted saporin decreased tumor volume without significant body weight changes and no regrowth of tumor at 3 months after complete regression. Protein transduction with MC shows promise for cancer therapeutics and, potentially, for regenerative medicine and other biomedical applications.

Nonviral Locally Injected Magnetic Vectors for In Vivo Gene Delivery: A Review of Studies on Magnetofection

Magnetic nanoparticles have been widely used in nanobiomedicine for diagnostics and the treatment of diseases, and as carriers for various drugs. The unique magnetic properties of "magnetic" drugs allow their delivery in a targeted tumor or tissue upon application of a magnetic field. The approach of combining magnetic drug targeting and gene delivery is called magnetofection, and it is very promising. This method is simple and efficient for the delivery of genetic material to cells using magnetic nanoparticles controlled by an external magnetic field. However, magnetofection in vivo has been studied insufficiently both for local and systemic routes of magnetic vector injection, and the relevant data available in the literature are often merely descriptive and contradictory. In this review, we collected and systematized the data on the efficiency of the local injections of magnetic nanoparticles that carry genetic information upon application of external magnetic fields. We also investigated the efficiency of magnetofection in vivo, depending on the structure and coverage of magnetic vectors. The perspectives of the development of the method were also considered.

Designer nanocarriers for navigating the systemic delivery of oncolytic viruses

Nanotechnology is paving the way for new carrier systems designed to overcome the greatest challenges of oncolytic virotherapy; systemic administration and subsequent implications of immune responses and specific cell binding and entry. Systemic administration of oncolytic agents is vital for disseminated neoplasms, however transition of nanoparticles (NP) to virotherapy has yielded modest results. Their success relies on how they navigate the merry-go-round of often-contradictory phases of NP delivery: circulatory longevity, tissue permeation and cellular interaction, with many studies postulating design features optimal for each phase. This review discusses the optimal design of NPs for the transport of oncolytic viruses within these phases, to determine whether improved virotherapeutic efficacy lies in the pharmacokinetic/pharmacodynamics characteristics of the NP-oncolytic viruses complexes rather than manipulation of the virus and targeting ligands.

Improved methods for mass production of magnetosomes and applications: a review

Magnetotactic bacteria have the unique ability to synthesize magnetosomes (nano-sized magnetite or greigite crystals arranged in chain-like structures) in a variety of shapes and sizes. The chain alignment of magnetosomes enables magnetotactic bacteria to sense and orient themselves along geomagnetic fields. There is steadily increasing demand for magnetosomes in the areas of biotechnology, biomedicine, and environmental protection. Practical difficulties in cultivating magnetotactic bacteria and achieving consistent, high-yield magnetosome production under artificial environmental conditions have presented an obstacle to successful development of magnetosome applications in commercial areas. Here, we review information on magnetosome biosynthesis and strategies for enhancement of bacterial cell growth and magnetosome formation, and implications for improvement of magnetosome yield on a laboratory scale and mass-production (commercial or industrial) scale.

Bacterial magnetic particles-polyethylenimine vectors deliver target genes into multiple cell types with a high efficiency and low toxicity

Bacterial magnetic particles (BMPs) are biosynthesized magnetic nano-scale materials with excellent dispersibility and biomembrane enclosure properties. In this study, we demonstrate that BMPs augment the ability of polyethylenimine (PEI) to deliver target DNA into difficult-to-transfect primary porcine liver cells, with transfection efficiency reaching over 30%. Compared with standard lipofection and polyfection, BMP-PEI gene vectors significantly enhanced the transfection efficiencies for the primary porcine liver cells and C2C12 mouse myoblast cell lines. To better understand the mechanism of magnetofection using BMP-PEI/DNA vectors, transmission electron microscopy (TEM) images of transfected Cos-7, HeLa, and HEP-G2 cells were observed. We found that the BMP-PEI/DNA complexes were trafficked into the cytoplasm and nucleus by way of vesicular transport and endocytosis. Our study builds support for the versatile BMP-PEI vector transfection system, which might be exploited to transfect a wide range of cell types or even to reach specific targets in the treatment of disease. KEY POINTS: • We constructed a BMP-PEI gene delivery vector by combining BMPs and PEI. • The vector significantly enhanced transfection efficiencies in eukaryotic cell lines. • The transfection mechanism of this vector was explained in our study.

Magnetotactic Bacteria and Magnetosomes as Smart Drug Delivery Systems: A New Weapon on the Battlefield with Cancer?

An important direction of research in increasing the effectiveness of cancer therapies is the design of effective drug distribution systems in the body. The development of the new strategies is primarily aimed at improving the stability of the drug after administration and increasing the precision of drug delivery to the destination. Due to the characteristic features of cancer cells, distributing chemotherapeutics exactly to the microenvironment of the tumor while sparing the healthy tissues is an important issue here. One of the promising solutions that would meet the above requirements is the use of Magnetotactic bacteria (MTBs) and their organelles, called magnetosomes (BMs). MTBs are commonly found in water reservoirs, and BMs that contain ferromagnetic crystals condition the magnetotaxis of these microorganisms. The presented work is a review of the current state of knowledge on the potential use of MTBs and BMs as nanocarriers in the therapy of cancer. The growing amount of literature data indicates that MTBs and BMs may be used as natural nanocarriers for chemotherapeutics, such as classic anti-cancer drugs, antibodies, vaccine DNA, and siRNA. Their use as transporters increases the stability of chemotherapeutics and allows the transfer of individual ligands or their combinations precisely to cancerous tumors, which, in turn, enables the drugs to reach molecular targets more effectively.

Magnetosomes: biogenic iron nanoparticles produced by environmental bacteria

The scientific community's interest in magnetotactic bacteria has increased substantially in recent decades. These prokaryotes have the particularity of synthesizing nanomagnets, called magnetosomes. The majority of research is based on several scientific questions. Where do magnetotactic bacteria live, what are their characteristics, and why are they magnetic? What are the molecular phenomena of magnetosome biomineralization and what are the physical characteristics of magnetosomes? In addition to scientific curiosity to better understand these stunning organisms, there are biotechnological opportunities to consider. Magnetotactic bacteria, as well as magnetosomes, are used in medical applications, for example cancer treatment, or in environmental ones, for example bioremediation. In this mini-review, we investigated all the aspects mentioned above and summarized the currently available knowledge.

Work Patterns of MamXY Proteins during Magnetosome Formation in Magnetospirillum gryphiswaldense MSR-1

The bacterium Magnetospirillum gryphiswaldense MSR-1 forms nanosized membrane-enclosed organelles termed magnetosomes. The mamXY operon, part of the magnetosome island (MAI), includes the mamY, mamX, mamZ, and ftsZ-like genes, which initiate gene transcription via the same promoter. We used a combination of molecular biological techniques (targeting of cross-linking reagents) and high-resolution mass spectrometry to investigate the coordinated activity of the four MamXY proteins in magnetite biomineralization. The FtsZ-like protein was shown by confocal laser scanning microscopy to be dispersed in the cytoplasm in the early stage of cell growth and then gradually polymerized along the magnetosome chain. Interactions of various pairs of MamXY proteins were observed using a bacterial two-hybrid system. We constructed a recombinant FtsZ-like-overexpressing strain, examined its growth patterns, and extracted magnetosome membrane proteins using a modified SDS/boiling method with BS²G-d₀/d₄ reagent, which helped stabilize interactions among MamXY proteins. In liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, MamY expression was detected first and remained highest among the four proteins throughout all stages of cell growth. MamX and MamZ expression was detected subsequently. The four proteins displayed coordinated expression patterns during the magnetosome maturation process. Unique peptides discovered in the MamXY protein sequences appeared to constitute "hidden" interaction sites involved in the formation of MamXY complex that helped control magnetosome shape and size.IMPORTANCE mamXY operon genes play an essential role in magnetite biomineralization, participate in redox reactions, and control magnetosome shape and size. However, mechanisms whereby the four MamXY proteins function together in iron oxidoreduction and transport are poorly understood. We used a combination of targeted cross-linking techniques and high-resolution mass spectrometry to elucidate the coordinated activity patterns of the MamXY proteins during magnetite biomineralization. Our findings indicate that the FtsZ-like protein undergoes polymerization and then recruits MamY, MamX, and MamZ in turn, and that these interactions depend on unique peptides present in the protein sequences. A hypothetical model of the functionalities of these proteins is proposed that accounts for the findings and provides a basis for further studies of coordination among magnetosome island (MAI) gene clusters during the process of magnetosome formation.

Nanoparticles: Properties and Applications in Cancer Immunotherapy

BACKGROUND

Tumours are no longer regarded as isolated masses of aberrantly proliferating epithelial cells. Rather, their properties depend on complex interactions between epithelial cancer cells and the surrounding stromal compartment within the tumour microenvironment. In particular, leukocyte infiltration plays a role in controlling tumour development and is now considered one of the hallmarks of cancer. Thus, in the last few years, immunotherapy has become a promising strategy to fight cancer, as its goal is to reprogram or activate antitumour immunity to kill tumour cells, without damaging the normal cells and provide long-lasting results where other therapies fail. However, the immune-related adverse events due to the low specificity in tumour cell targeting, strongly limit immunotherapy efficacy. In this regard, nanomedicine offers a platform for the delivery of different immunotherapeutic agents specifically to the tumour site, thus increasing efficacy and reducing toxicity. Indeed, playing with different material types, several nanoparticles can be formulated with different shape, charge, size and surface chemical modifications making them the most promising platform for biomedical applications.

AIM

In this review, we will summarize the different types of cancer immunotherapy currently in clinical trials or already approved for cancer treatment. Then, we will focus on the most recent promising strategies to deliver immunotherapies directly to the tumour site using nanoparticles.

CONCLUSION

Nanomedicine seems to be a promising approach to improve the efficacy of cancer immunotherapy. However, additional investigations are needed to minimize the variables in the production processes in order to make nanoparticles suitable for clinical use.

Bacterial magnetosomes-based nanocarriers for co-delivery of cancer therapeutics in vitro

In recent times, co-delivery of therapeutics has emerged as a promising strategy for treating dreadful diseases such as cancer.

MATERIALS AND METHODS

In this study, we developed a novel nanocarrier based on bacterial magnetosomes (BMs) that co-loaded with siRNA and doxorubicin (DOX) using polyethyleneimine (PEI) as a cross-linker (BMs/DP/siRNA). The delivery efficiency of siRNA as well as the pH-responsive release of DOX, and synergistic efficacy of these therapeutics in vitro were systematically investigated.

RESULTS

The structure of DOX-PEI (DP) conjugates that synthesized via hydrazone bond formation was confirmed by 1H nuclear magnetic resonance (NMR). The in vitro release experiments showed that the DP conjugate (DOX-loading efficiency - 5.77%±0.08%) exhibited the long-term release behavior. Furthermore, the optimal BMs/DP/siRNA particle size of 107.2 nm and the zeta potential value of 31.1±1.0 mV facilitated enhanced cellular internalization efficiency. Moreover, the agarose gel electrophoresis showed that the co-delivery system could protect siRNA from degradation in serum and RNase A. In addition, the cytotoxicity assay showed that BMs/DP/siRNA could achieve an excellent synergistic effect compared to that of siRNA delivery alone. The acridine orange (AO)/ethidium bromide (EB) double staining assay also showed that BMs/DP/siRNA complex could induce cells in a stage of late apoptosis and nanocomplex located in the proximity of the nucleus.

CONCLUSION

The combination of gene and chemotherapeutic drug using BMs is highly efficient, and the BMs/DP/siRNA would be a promising therapeutic strategy for the future therapeutics.

An enhanced anti-tumor effect of apoptin-cecropin B on human hepatoma cells by using bacterial magnetic particle gene delivery system

The gene therapy of cancer, due to the limit of its efficiency and safety, has not been widely used in clinical. Recently, bacterial magnetic particles (BMPs), which are membrane-bound nanocrystals found in magnetotactic bacteria, have been exploited as a new gene delivery system. However, its application on gene therapy remains to be explored. In our previous study, we found that a combination of cecropin B (ABPs) and apoptin (VP3) could serve as an effective gene therapeutic agent. Thus, in this study, we used BMPs to deliver the co-expression plasmid of these two gene, namely pVAX1-VA, and evaluated its therapeutic effect on human hepatocellular carcinoma (HepG2). Our results showed that BMPs significantly improved the efficiency of gene transfection (almost 3-fold than Lipofectamine 2000 at 48 h, P < .001), which led to stronger apoptosis (in a peak almost 2-fold than Lipofectamine 2000-pVAX1-VA, P < .01) and growth inhibition of HepG2 cells. More importantly, compared with Lipofectamine 2000-pVAX1-VA group, BMP-pVAX1-VA strikingly inhibited tumor growth (0.60 ± 0.09 g vs. 0.88 ± 0.11 g, P < .05) in nude mouse tumor models and increased the tumor-infiltrating lymphocytes considerably without apparent cytotoxicity. These findings suggest that BMPs could be an attractive gene delivery system for gene therapy and provide a potential available treatment for human hepatocellular carcinoma and maybe some other kinds of tumors.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

Flow cytometry as a rapid analytical tool to determine physiological responses to changing O2 and iron concentration by Magnetospirillum gryphiswaldense strain MSR-1

Magnetotactic bacteria (MTB) are a diverse group of bacteria that synthesise magnetosomes, magnetic membrane-bound nanoparticles that have a variety of diagnostic, clinical and biotechnological applications. We present the development of rapid methods using flow cytometry to characterize several aspects of the physiology of the commonly-used MTB Magnetospirillum gryphiswaldense MSR-1. Flow cytometry is an optical technique that rapidly measures characteristics of individual bacteria within a culture, thereby allowing determination of population heterogeneity and also permitting direct analysis of bacteria. Scatter measurements were used to measure and compare bacterial size, shape and morphology. Membrane permeability and polarization were measured using the dyes propidium iodide and bis-(1,3-dibutylbarbituric acid) trimethine oxonol to determine the viability and ‘health’ of bacteria. Dyes were also used to determine changes in concentration of intracellular free iron and polyhydroxylakanoate (PHA), a bacterial energy storage polymer. These tools were then used to characterize the responses of MTB to different O₂ concentrations and iron-sufficient or iron-limited growth. Rapid analysis of MTB physiology will allow development of bioprocesses for the production of magnetosomes, and will increase understanding of this fascinating and useful group of bacteria.

Bacterial magnetic particles improve testes-mediated transgene efficiency in mice

Nano-scaled materials have been proved to be ideal DNA carriers for transgene. Bacterial magnetic particles (BMPs) help to reduce the toxicity of polyethylenimine (PEI), an efficient gene-transferring agent, and assist tissue transgene ex vivo. Here, the effectiveness of the BMP-PEI complex-conjugated foreign DNAs (BPDs) in promoting testes-mediated gene transfer (TMGT) in mouse was compared with that of liposome-conjugated foreign DNAs. The results proved that through testes injection, the clusters of BPDs successfully reached the cytoplasm and the nuclear of spermatogenesis cell, and expressed in testes of transgene founder mice. Additionally, the ratio of founder mice obtained from BPDs (88%) is about 3 times higher than the control (25%) (p < 0.05). Interestingly, the motility of sperms recovered from epididymis of the founder mice from BPD group were significantly improved, as compared with the control (p < 0.01). Based on classic breeding, the ratio of transgene mice within the first filial was significantly higher in BPDs compared with the control (73.8% versus 11.6%, p < 0.05). TMGT in this study did not produce visible histological changes in the testis. In conclusion, nano-scaled BPDs could be an alternative strategy for efficiently producing transgene mice in vivo.

Bioengineered and biohybrid bacteria-based systems for drug delivery

The use of bacterial cells as agents of medical therapy has a long history. Research that was ignited over a century ago with the accidental infection of cancer patients has matured into a platform technology that offers the promise of opening up new potential frontiers in medical treatment. Bacterial cells exhibit unique characteristics that make them well-suited as smart drug delivery agents. Our ability to genetically manipulate the molecular machinery of these cells enables the customization of their therapeutic action as well as its precise tuning and spatio-temporal control, allowing for the design of unique, complex therapeutic functions, unmatched by current drug delivery systems. Early results have been promising, but there are still many important challenges that must be addressed. We present a review of promises and challenges of employing bioengineered bacteria in drug delivery systems and introduce the biohybrid design concept as a new additional paradigm in bacteria-based drug delivery.

A Natural Bacterium-Produced Membrane-Bound Nanocarrier for Drug Combination Therapy

To minimize the non-specific toxicity of drug combination during cancer therapy, we prepared a new system synthesized from bacteria to deliver the anticancer drugs cytosine arabinoside (Ara-C) and daunorubicin (DNR). In this study, we selected genipin (GP) and poly-l-glutamic acid (PLGA) as dual crosslinkers. Herewith, we demonstrated the preparation, characterization and in vitro antitumor effects of Ara-C and DNR loaded GP-PLGA-modified bacterial magnetosomes (BMs) (ADBMs-P). The results show that this new system is stable and exhibits optimal drug-loading properties. The average diameters of BMs and ADBMs-P were 42.0 ± 8.6 nm and 65.5 ± 8.9 nm, respectively, and the zeta potential of ADBMs-P (-42.0 ± 6.4 mV) was significantly less than that of BMs (-28.6 ± 7.6 mV). The optimal encapsulation efficiency and drug loading of Ara-C were 68.4% ± 9.4% and 32.4% ± 2.9%, respectively, and those of DNR were 36.1% ± 2.5% and 17.9% ± 1.6%. Interestingly, this system also exhibits long-term release behaviour sequentially, without an initial burst release. The Ara-C drug continued to release about 85% within 40 days, while DNR release lasted only for 13 days. Moreover, similar to free drugs, ADBMs-Ps are strongly cytotoxic to cancer cells in vitro (HL-60 cells), with the inhibition rate approximately 96%. This study reveals that this new system has a potential for drug delivery application in the future, especially for combination therapy.

Co-delivery of doxorubicin and recombinant plasmid pHSP70-Plk1-shRNA by bacterial magnetosomes for osteosarcoma therapy

To explore a novel combination of chemotherapy, gene therapy, and thermotherapy for osteosarcoma, a targeted heat-sensitive co-delivery system based on bacterial magnetosomes (BMs) was developed. The optimal culture conditions of magnetotactic bacteria (MTB) AMB-1 and characterization of BMs were achieved. A recombinant eukaryotic plasmid heat shock protein 70-polo-like kinase 1-short hairpin RNA (pHSP70-Plk1-shRNA) under transcriptional control of a thermosensitive promoter (human HSP70 promoter) was constructed for gene therapy. Doxorubicin (DOX) and pHSP70-Plk1-shRNA were included in the targeted thermosensitive co-delivery system, and in vitro DOX release activity, targeted gene silencing efficiency and in vitro antitumor efficacy were investigated. The results showed that the optimal culture conditions of MTB AMB-1 are an oxygen concentration of 4.0%, a pH value of 7.0, 20 μmol/L of ferrous sulfate, 800 mg/L of sodium nitrate, and 200 mg/L of succinic acid. The temperature of BMs reached 43°C within 3 minutes and could be maintained for 30 minutes by adjusting the magnitude of the alternating magnetic field (AMF). The diameters of BMs, BM-DOX, BM-recombinant eukaryotic plasmid pHSP70-Plk1-shRNA (shPlk1), and BM-DOX-shPlk1 were 43.7±4.6, 79.2±5.4, 88.9±7.8, and 133.5±11.4 nm, respectively. The zeta potentials of BMs, BM-DOX, BM-shPlk1, and BM-DOX-shPlk1 were -29.4±6.9, -9.5±5.6, -16.7±4.8, and -10.3±3.1 mV, respectively. Besides, the system exhibited good release behavior. DOX release rate from BM-DOX-shPlk1 was 54% after incubation with phosphate-buffered saline at 43°C and 37% after incubation with 50% fetal bovine serum, which was significantly higher than that at 37°C (P<0.05). In addition, the expressions of Plk1 mRNA and protein were significantly suppressed in cells treated with BM-DOX-shPlk1 following hyperthermia treatment under the influence of an AMF compared to other groups (P<0.05). Furthermore, evaluation of the effect of in vitro antitumor revealed that BM-DOX-shPlk1 following hyperthermia treatment under the influence of an AMF was significantly more effective than others in tumor inhibition. In conclusion, the new heat-sensitive co-delivery system represents a promising approach for the treatment of cancer.

Magnetotactic bacteria and magnetosomes - Scope and challenges

Geomagnetism aided navigation has been demonstrated by certain organisms which allows them to identify a particular location using magnetic field. This attractive technique to recognize the course was earlier exhibited in numerous animals, for example, birds, insects, reptiles, fishes and mammals. Magnetotactic bacteria (MTB) are one of the best examples for magnetoreception among microorganisms as the magnetic mineral functions as an internal magnet and aid the microbe to move towards the water columns in an oxic-anoxic interface (OAI). The ability of MTB to biomineralize the magnetic particles (magnetosomes) into uniform nano-sized, highly crystalline structure with uniform magnetic properties has made the bacteria an important topic of research. The superior properties of magnetosomes over chemically synthesized magnetic nanoparticles made it an attractive candidate for potential applications in microbiology, biophysics, biochemistry, nanotechnology and biomedicine. In this review article, the scope of MTB, magnetosomes and its challenges in research and industrial application have been discussed in brief. This article mainly focuses on the application based on the magnetotactic behaviour of MTB and magnetosomes in different areas of modern science.

Magnetotactic bacteria: nanodrivers of the future

Magnetotactic bacteria (MTB) represent a heterogeneous group of Gram-negative aquatic prokaryotes with a broad range of morphological types, including vibrioid, coccoid, rod and spirillum. MTBs possess the virtuosity to passively align and actively swim along the magnetic field. Magnetosomes are the trademark nano-ranged intracellular structures of MTB, which comprise magnetic iron-bearing inorganic crystals enveloped by an organic membrane, and are dedicated organelles for their magnetotactic lifestyle. Magnetosomes endue high and even dispersion in aqueous solutions compared with artificial magnetites, claiming them as paragon nanomaterials. MTB and magnetosomes offer high technological potential in modern science, technology and medicines. This review focuses on the applicability of MTB and magnetosomes in various areas of modern benefits.

Preparation and in vitro antitumor effects of cytosine arabinoside-loaded genipin-poly-l-glutamic acid-modified bacterial magnetosomes

To solve the problem of synthesized magnetic nanoparticles in cancer therapy, a new drug delivery system synthesized from bacteria was used to load cytosine arabinoside (Ara-C). Genipin (GP) and poly-l-glutamic acid (PLGA) were selected as dual cross-linkers. The preparation and characterization of Ara-C-loaded GP-PLGA-modified bacterial magnetosomes (BMs) (ABMs-P), as well as their in vitro antitumor effects, were all investigated. Transmission electron micrographs (TEM) and Fourier transform infrared (FTIR) spectroscopy suggested that Ara-C could be bound to the membrane of BMs modified by GP-PLGA. The diameters of the BMs and ABMs-P were 42.0±8.6 nm and 74.9±8.2 nm, respectively. The zeta potential revealed that the nanoparticles were stable. Moreover, this system exhibited optimal drug-loading properties and long-term release behavior. The optimal encapsulation efficiency and drug-loading were 64.1%±6.6% and 38.9%±2.4%, respectively, and ABMs-P could effectively release 90% Ara-C within 40 days, without the release of an initial burst. In addition, in vitro antitumor experiments elucidated that ABMs-P is cytotoxic to HL-60 cell lines, with an inhibition rate of 95%. The method of coupling drugs on BMs using dual cross-linkers is effective, and our results reveal that this new system has potential applications for drug delivery in the future.

Magnetotactic bacteria as potential sources of bioproducts

Magnetotactic bacteria (MTB) produce intracellular organelles called magnetosomes which are magnetic nanoparticles composed of magnetite (Fe₃O₄) or greigite (Fe₃S₄) enveloped by a lipid bilayer. The synthesis of a magnetosome is through a genetically controlled process in which the bacterium has control over the composition, direction of crystal growth, and the size and shape of the mineral crystal. As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane. These features are not observed in magnetic particles produced abiotically and thus magnetosomes are of great interest in biotechnology. Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms. Moreover, genome sequences have allowed researchers to study genes related to magnetosome production for the synthesis of magnetic particles for use in future commercial and medical applications. Here, we review the current information on the biology of MTB and apply, for the first time, a genome mining strategy on these microorganisms to search for secondary metabolite synthesis genes. More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.

Stimuli-responsive nanocarriers for drug delivery

Spurred by recent progress in materials chemistry and drug delivery, stimuli-responsive devices that deliver a drug in spatial-, temporal- and dosage-controlled fashions have become possible. Implementation of such devices requires the use of biocompatible materials that are susceptible to a specific physical incitement or that, in response to a specific stimulus, undergo a protonation, a hydrolytic cleavage or a (supra)molecular conformational change. In this Review, we discuss recent advances in the design of nanoscale stimuli-responsive systems that are able to control drug biodistribution in response to specific stimuli, either exogenous (variations in temperature, magnetic field, ultrasound intensity, light or electric pulses) or endogenous (changes in pH, enzyme concentration or redox gradients).

Suppression of breast tumor growth by DNA vaccination against phosphatase of regenerating liver 3

Phosphatase of regenerating liver (PRL)-3 is highly expressed in multiple cancers and has important roles in cancer development. Some small-molecule inhibitors and antibodies targeting PRL-3 have been recently reported to inhibit tumor growth effectively. To determine whether PRL-3-targeted DNA vaccination can induce immune response to prevent or inhibit the tumor growth, we established mouse D2F2 breast cancer cells expressing PRL-3 (D2F2/PRL-3) and control cells (D2F2/NC) with lentivirus, and constructed pVAX1-Igκ-PRL-3 plasmid (named as K-P3) as DNA vaccine to immunize BALB/c mice. We found that the K-P3 vaccine delivered by gene gun significantly prevented the growth of D2F2/PRL-3 compared with pVAX1-vector (P<0.01), but not of D2F2/NC, and improved the survival of D2F2/PRL-3-innoculated mice. Both PRL-3-targeted cytotoxic T lymphocytes (CTLs) and T-helper type 1 cell immune response (production of high levels of interferon-γ and tumor necrosis factor-α) were found to be involved in the preventive effect. Furthermore, PRL-3-targeted DNA immunization inhibited tumor growth of D2F2/PRL-3 cells in mice. We also evaluated the potential of immunization with PRL-3 protein, but no significant therapeutic or preventive effect was obtained on tumor growth. To enhance the immunity of PRL-3, we incorporated different molecular adjuvants, such as Mycobacterium tuberculosis heat-shock protein, CTL antigen 4 and M. tuberculosis T-cell stimulatory epitope (MT), into K-P3 vaccine for expressing the fusion proteins. We found that these adjuvant molecules did not significantly improve the antitumor activity of PRL-3 vaccine, but enhanced the production of PRL-3 antibodies in immunized mice. Summarily, our findings demonstrate that PRL-3-targeted DNA vaccine can generate significantly preventive and therapeutic effects on the growth of breast cancer expressing PRL-3 through the induction of cellular immune responses to PRL-3.

Self-assembled magnetic theranostic nanoparticles for highly sensitive MRI of minicircle DNA delivery

As a versatile gene vector, minicircle DNA (mcDNA) has a great potential for gene therapy. However, some serious challenges remain, such as to effectively deliver mcDNA into targeted cells/tissues and to non-invasively monitor the delivery of the mcDNA. Superparamagnetic iron oxide (SPIO) nanoparticles have been extensively used for both drug/gene delivery and diagnosis. In this study, an MRI visible gene delivery system was developed with a core of SPIO nanocrystals and a shell of biodegradable stearic acid-modified low molecular weight polyethyleneimine (Stearic-LWPEI) via self-assembly. The Stearic-LWPEI-SPIO nanoparticles possess a controlled clustering structure, narrow size distribution and ultrasensitive imaging capacity. Furthermore, the nanoparticle can effectively bind with mcDNA and protect it from enzymatic degradation. In conclusion, the nanoparticle shows synergistic advantages in the effective transfection of mcDNA and non-invasive MRI of gene delivery.