Centrifugation-Free Magnetic Isolation of Functional Mitochondria Using Paramagnetic Iron Oxide Nanoparticles

Machine learning assisted-nanomedicine using magnetic nanoparticles for central nervous system diseases

Magnetic nanoparticles possess unique properties distinct from other types of nanoparticles developed for biomedical applications. Their unique magnetic properties and multifunctionalities are especially beneficial for central nervous system (CNS) disease therapy and diagnostics, as well as targeted and personalized applications using image-guided therapy and theranostics. This review discusses the recent development of magnetic nanoparticles for CNS applications, including Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis, and drug addiction. Machine learning (ML) methods are increasingly applied towards the processing, optimization and development of nanomaterials. By using data-driven approach, ML has the potential to bridge the gap between basic research and clinical research. We review ML approaches used within the various stages of nanomedicine development, from nanoparticle synthesis and characterization to performance prediction and disease diagnosis.

Understanding intracellular nanoparticle trafficking fates through spatiotemporally resolved magnetic nanoparticle recovery

The field of nanomedicine has the potential to be a game-changer in global health, with possible applications in prevention, diagnostics, and therapeutics. However, despite extensive research focus and funding, the forecasted explosion of novel nanomedicines is yet to materialize. We believe that clinical translation is ultimately hampered by a lack of understanding of how nanoparticles really interact with biological systems. When placed in a biological environment, nanoparticles adsorb a biomolecular layer that defines their biological identity. The challenge for bionanoscience is therefore to understand the evolution of the interactions of the nanoparticle-biomolecules complex as the nanoparticle is trafficked through the intracellular environment. However, to progress on this route, scientists face major challenges associated with isolation of specific intracellular compartments for analysis, complicated by the diversity of trafficking events happening simultaneously and the lack of synchronization between individual events. In this perspective article, we reflect on how magnetic nanoparticles can help to tackle some of these challenges as part of an overall workflow and act as a useful platform to investigate the bionano interactions within the cell that contribute to this nanoscale decision making. We discuss both established and emerging techniques for the magnetic extraction of nanoparticles and how they can potentially be used as tools to study the intracellular journey of nanomaterials inside the cell, and their potential to probe nanoscale decision-making events. We outline the inherent limitations of these techniques when investigating particular bio-nano interactions along with proposed strategies to improve both specificity and resolution. We conclude by describing how the integration of magnetic nanoparticle recovery with sophisticated analysis at the single-particle level could be applied to resolve key questions for this field in the future.

Dual-Targeted Synthetic Nanoparticles for Cardiovascular Diseases

Atherosclerosis is one of the world's most aggressive diseases, claiming over 17.5 million lives per year. This disease is usually caused by high amounts of lipoproteins circulating in the blood stream, which leads to plaque formation. Ultimately, these plaques can undergo thrombosis and lead to major heart damage. A major contributor to these vulnerable plaques is macrophage apoptosis. Development of nanovehicles that carry contrast and therapeutic agents to the mitochondria within these macrophages is attractive for the diagnosis and treatment of atherosclerosis. Here, we report the design and synthesis of a dual-targeted synthetic nanoparticle (NP) to perform the double duty of diagnosis and therapy in atherosclerosis treatment regime. A library of dual-targeted NPs with an encapsulated iron oxide NP, mito-magneto (MM), with a magnetic resonance imaging (MRI) contrast enhancement capability was elucidated. Relaxivity measurements revealed that there is a substantial enhancement in transverse relaxivities upon the encapsulation of MM inside the dual-targeted NPs, highlighting the MRI contrast-enhancing ability of these NPs. Successful in vivo imaging documenting the distribution of MM-encapsulated dual-targeted NPs in the heart and aorta in mice ensured the diagnostic potential. The presence of mannose receptor targeting ligands and the optimization of the NP composition facilitated its ability to perform therapeutic duty by targeting the macrophages at the plaque. These dual-targeted NPs with the encapsulated MM were able to show therapeutic potential and did not trigger any toxic immunogenic response.

Isolation of mitochondria from cells and tissues

Isolated mitochondria are useful to study fundamental processes including mitochondrial respiration, metabolic activity, protein import, membrane fusion, protein complex assembly, as well as interactions of mitochondria with the cytoskeleton, nuclear encoded mRNAs, and other organelles. In addition, studies of the mitochondrial proteome, phosphoproteome, and lipidome are dependent on preparation of highly purified mitochondria (Boldogh, Vojtov, Karmon, & Pon, 1998; Cui, Conte, Fox, Zara, & Winge, 2014; Marc et al., 2002; Meeusen, McCaffery, & Nunnari, 2004; Reinders et al., 2007; Schneiter et al., 1999; Stuart & Koehler, 2007). Most methods to isolate mitochondria rely on differential centrifugation, a two-step centrifugation carried out at low speed to remove intact cells, cell and tissue debris, and nuclei from whole cell extracts followed by high speed centrifugation to concentrate mitochondria and separate them from other organelles. However, methods to disrupt cells and tissue vary. Moreover, density gradient centrifugation or affinity purification of the organelle are used to further purify mitochondria or to separate different populations of the organelle. Here, we describe protocols to isolate mitochondria from different cells and tissues as well as approaches to assess the purity and integrity of isolated organelles.

Green extraction of healthy and additive free mitochondria with a conventional centrifuge

In this research, we propose a novel centrifugal device for the massive extraction of healthy mitochondria with a centrifuge used in general laboratories within 30 minutes. The device mainly consists of two key components. One component is a microfluidic device, which is fabricated by photolithography, nickel electroforming, and polydimethylsiloxane casting, for the efficient disruption of the cell membrane. The other component is a stainless steel container, which is manufactured by computer numerical control machining, for the storage of the cell suspension. After assembly, the appropriate number of cells is pushed through the microfluidic device for cell membrane disruption by centrifugal force generated by a general laboratory centrifuge. The solution which contains cell debris and mitochondria are collected to purify the crude mitochondria via differential centrifugation. Compared with the quantity and efficiency of mitochondria isolated from the same number of cells using a conventional kit, device-extracted mitochondria show a more complete mitochondrial electron transport chain complex and a similar number of mitochondria verified by Western blot analysis of mitochondrial complexes I-V and mitochondrial outer membrane protein Tom20, respectively, as well as a normal mitochondrial structure revealed by transmission electron microscopy. Moreover, the mitochondrial membrane potential of device-extracted mitochondria stained with tetramethylrhodamine ethyl ester is higher than that of kit-extracted mitochondria. Furthermore, the coculture of device-extracted mitochondria with fibroblasts revealed that fibroblasts could uptake foreign mitochondria through endocytosis without drug treatment. These results show that the proposed microfluidic device preserves mitochondrial protein structure, membrane integrity, and membrane potential within 30 minutes of extraction and is a useful tool for therapeutic mitochondrial transplantation and regenerative medicine.

Fractionated mitochondrial magnetic separation for isolation of synaptic mitochondria from brain tissue

While mitochondria maintain essential cellular functions, such as energy production, calcium homeostasis, and regulating programmed cellular death, they also play a major role in pathophysiology of many neurological disorders. Furthermore, several neurodegenerative diseases are closely linked with synaptic damage and synaptic mitochondrial dysfunction. Unfortunately, the ability to assess mitochondrial dysfunction and the efficacy of mitochondrial-targeted therapies in experimental models of neurodegenerative disease and CNS injury is limited by current mitochondrial isolation techniques. Density gradient ultracentrifugation (UC) is currently the only technique that can separate synaptic and non-synaptic mitochondrial sub-populations, though small brain regions cannot be assayed due to low mitochondrial yield. To address this limitation, we used fractionated mitochondrial magnetic separation (FMMS), employing magnetic anti-Tom22 antibodies, to develop a novel strategy for isolation of functional synaptic and non-synaptic mitochondria from mouse cortex and hippocampus without the usage of UC. We compared the yield and functionality of mitochondria derived using FMMS to those derived by UC. FMMS produced 3x more synaptic mitochondrial protein yield compared to UC from the same amount of tissue, a mouse hippocampus. FMMS also has increased sensitivity, compared to UC separation, to measure decreased mitochondrial respiration, demonstrated in a paradigm of mild closed head injury. Taken together, FMMS enables improved brain-derived mitochondrial yield for mitochondrial assessments and better detection of mitochondrial impairment in CNS injury and neurodegenerative disease.

An Improved Method for Preparation of Uniform and Functional Mitochondria from Fresh Liver

Background and Aims: As the major energy source for mammalian cells, mitochondria have been the subject of numerous studies. However, the isolation and purification of healthy mitochondria, especially from fresh tissue, remains challenging. The most popular methods and kits involve various centrifugation steps which require substantial time and equipment but do not consistently provide pure preparations of functional mitochondria. The aim of this study was to determine whether methods could be devised to improve the purity and yield of functional mitochondria from fresh tissue. Methods: Fresh mouse liver was homogenized, and cells lysed. Particle size analysis, quantitation of mitochondrial DNA, mitochondrial oxygen consumption, and purity of mitochondria (by electron microscopy) were measured in samples after various purification steps and significant differences determined. Results: A two-step procedure consisting of centrifugation followed by filtration through 1.2μ and 0.8μ filters resulted in uniform mitochondrial preparations with diameters between 520-540 nm, and approximately 5-times more pure samples. The mitochondria thus obtained had oxygen consumption and sensitivities to mitochondrial inhibitors that were indistinguishable from those purified by centrifugation alone. Electron microscopy confirmed the presence of more uniform and 4-5 times greater concentrations of mitochondria compared to centrifugation alone. Conclusions: A two-step procedure consisting of sequential centrifugation followed by filtration is a rapid method for the production of highly purified, uniform and functional mitochondria.

Isolation of mitochondria from Saccharomyces cerevisiae using magnetic bead affinity purification

Isolated mitochondria are widely used to study the function of the organelle. Typically, mitochondria are prepared using differential centrifugation alone or in conjunction with density gradient ultracentrifugation. However, mitochondria isolated using differential centrifugation contain membrane or organelle contaminants, and further purification of crude mitochondria by density gradient ultracentrifugation requires large amounts of starting material, and is time-consuming. Mitochondria have also been isolated by irreversible binding to antibody-coated magnetic beads. We developed a method to prepare mitochondria from budding yeast that overcomes many of the limitations of other methods. Mitochondria are tagged by insertion of 6 histidines (6xHis) into the TOM70 (Translocase of outer membrane 70) gene at its chromosomal locus, isolated using Ni-NTA (nickel (II) nitrilotriacetic acid) paramagnetic beads and released from the magnetic beads by washing with imidazole. Mitochondria prepared using this method contain fewer contaminants, and are similar in ultrastructure as well as protein import and cytochrome c oxidase complex activity compared to mitochondria isolated by differential centrifugation. Moreover, this isolation method is amenable to small samples, faster than purification by differential and density gradient centrifugation, and more cost-effective than purification using antibody-coated magnetic beads. Importantly, this method can be applied to any cell type where the genetic modification can be introduced by CRISPR or other methods.