Magnetic particles for the separation and purification of nucleic acids

Adsorption behaviors of DNA/cation complexes on amino and silica chip surfaces: a dual polarization interferometry study

The adsorption of DNA/Ca(2+), DNA/Cu(2+), and DNA/Co(NH3)6(3+) complexes on amino and silica chip surfaces were investigated using dual polarization interferometry. A more compact DNA/cation complex layer formed on the amino chip surface compared with that on the silica chip surface at the same cation condition. The real-time mass, thickness, and density changes were monitored during the adsorption process. The overall results show that the approaching complexes can cause the conformation rearrangement of the preadsorbed complexes and the preadsorbed complexes affect the deposition pattern of the approaching complexes during the adsorption of DNA/Ca(2+) and DNA/Cu(2+) complexes on both chip surfaces. The relatively strong electrostatic repulsion between the approaching and adsorbed complexes results in multiple mass loading rate changes and loose attachment of the approaching complexes. The weak repulsion between the DNA/Co(NH3)6(3+) complexes cannot induce this kind of conformation rearrangement. Thus, no multiple mass loading rate changes were observed. Meanwhile, the preadsorbed DNA/Co(NH3)6(3+) complex can also affect the deposition pattern of the approaching complex because of the geometric resistance. Therefore, this study will help better understand the conformation change and deposition pattern of complexes with different charge conditions during the adsorption process on the solid-liquid interface.

In situ magnetic separation of antibody fragments from Escherichia coli in complex media

Background

In situ magnetic separation (ISMS) has emerged as a powerful tool to overcome process constraints such as product degradation or inhibition of target production. In the present work, an integrated ISMS process was established for the production of his-tagged single chain fragment variable (scFv) D1.3 antibodies (“D1.3”) produced by E. coli in complex media. This study investigates the impact of ISMS on the overall product yield as well as its biocompatibility with the bioprocess when metal-chelate and triazine-functionalized magnetic beads were used.

Results

Both particle systems are well suited for separation of D1.3 during cultivation. While the triazine beads did not negatively impact the bioprocess, the application of metal-chelate particles caused leakage of divalent copper ions in the medium. After the ISMS step, elevated copper concentrations above 120 mg/L in the medium negatively influenced D1.3 production. Due to the stable nature of the model protein scFv D1.3 in the biosuspension, the application of ISMS could not increase the overall D1.3 yield as was shown by simulation and experiments.

Conclusions

We could demonstrate that triazine-functionalized beads are a suitable low-cost alternative to selectively adsorb D1.3 fragments, and measured maximum loads of 0.08 g D1.3 per g of beads. Although copper-loaded metal-chelate beads did adsorb his-tagged D1.3 well during cultivation, this particle system must be optimized by minimizing metal leakage from the beads in order to avoid negative inhibitory effects on growth of the microorganisms and target production. Hereby, other types of metal chelate complexes should be tested to demonstrate biocompatibility. Such optimized particle systems can be regarded as ISMS platform technology, especially for the production of antibodies and their fragments with low stability in the medium. The proposed model can be applied to design future ISMS experiments in order to maximize the overall product yield while the amount of particles being used is minimized as well as the number of required ISMS steps.

Imaging DNA with fluorochrome bearing metals

Molecules that fluoresce upon binding DNA are widely used in assaying and visualizing DNA in cells and tissues. However, using light to visualize DNA in animals is limited by the attenuation of light transmission by biological tissues. Moreover, it is now clear that DNA is an important mediator of dead cell clearance, coagulation reactions, and an immunogen in autoimmune lupus. Attaching metals (e.g., superparamagnetic nanoparticles, gadolinium ions, radioactive metal ions) to DNA-binding fluorochromes provides a way of imaging DNA in whole animals, and potentially humans, without light. Imaging metal-bearing, DNA-binding fluorochromes and their target DNA by magnetic resonance imaging may shed light on the many key roles of DNA in health and disease beyond the storage of genetic information.

Semi-continuous in situ magnetic separation for enhanced extracellular protease production-modeling and experimental validation

In modern biotechnology proteases play a major role as detergent ingredients. Especially the production of extracellular protease by Bacillus species facilitates downstream processing because the protease can be directly harvested from the biosuspension. In situ magnetic separation (ISMS) constitutes an excellent adsorptive method for efficient extracellular protease removal during cultivation. In this work, the impact of semi-continuous ISMS on the overall protease yield has been investigated. Results reveal significant removal of the protease from Bacillus licheniformis cultivations. Bacitracin-functionalized magnetic particles were successfully applied, regenerated and reused up to 30 times. Immediate reproduction of the protease after ISMS proved the biocompatibility of this integrated approach. Six subsequent ISMS steps significantly increased the overall protease yield up to 98% because proteolytic degradation and potential inhibition of the protease in the medium could be minimized. Furthermore, integration of semi-continuous ISMS increased the overall process efficiency due to reduction of the medium consumption. Process simulation revealed a deeper insight into protease production, and was used to optimize ISMS steps to obtain the maximum overall protease yield.

[Protocols of proteins interactomics: molecular fishing on optical chips and magnetic nanoparticles]

Now it is absolutely clear, that the majority of proteins in living systems function due to interaction with each other in stable or dynamic proteins complexes. Therefore necessity of deeper studies of proteins functions causes expansion of protein-protein interaction research. In the present review the brief description and comparative estimation of experimental methods and protocols of protein interactomics, based on technology of molecular fishing on an optical chips and paramagnetic nanoparticles is given.

Comparison of the Abbott RealTime High Risk HPV with Genomica HPV Clinical Array for the detection of human papillomavirus DNA

Human papillomavirus (HPV) has been identified as the major cause of cervical cancer worldwide and HPV DNA testing is recommended in primary cervical cancer screening. Several molecular tests for detection/typing of HPV DNA with different sensitivity and specificity are commercially available. The present study compared the performance of the Abbott RealTime High Risk HPV assay and the Genomica HPV Clinical Array CLART2 in 78 specimens (63 cervical smears and 15 rectal/urethral swabs).The typing results of the Genomica assay were in absolute agreement with each of the four possible result categories of the Abbott assay (HPV16, HPV18, Other HR HPV, not detected) in 87.2% (68/78) of the samples, with a Cohen' kappa agreement coefficient for every HR type of 0.62 (95% CI: 0.39-0.85), higher in cervical swabs (k = 0.74, 95% CI: 0.50-0.99) than in rectal/urethral swabs (k = 0.36, 95% CI: 0.00-0.82). There was an excellent agreement of the Genomica results with those of Abbott in cervical samples harbored HPV single infection (100% agreement). Nonetheless, both methods may lose sensitivity for detecting HPV types in multiple infections, giving discordant results (10/78). This underlines the importance of establishing the analytical sensitivity in HPV type detection in single and multiple HPV infections. In rectal/urethral swabs, 5 of 15 (33%) discordant cases were observed, most of which became compatible when the Genomica assay was performed starting from nucleic acid extracted with the Abbott m2000sp system. These results suggest that nucleic extraction based on the magnetic beads technique is suitable for HPV DNA detection in urethral/rectal swabs.

Tunable diffusion of magnetic particles in a quasi-one-dimensional channel

The diffusion of a system of ferromagnetic dipoles confined in a quasi-one-dimensional parabolic trap is studied using Brownian dynamics simulations. We show that the dynamics of the system is tunable by an in-plane external homogeneous magnetic field. For a strong applied magnetic field, we find that the mobility of the system, the exponent of diffusion, and the crossover time among different diffusion regimes can be tuned by the orientation of the magnetic field. For weak magnetic fields, the exponent of diffusion in the subdiffusive regime is independent of the orientation of the external field.

Monodispersed magnetic polystyrene beads with excellent colloidal stability and strong magnetic response

Monodispersed polystyrene beads incorporated with Fe(3) O(4) nanoparticles are prepared via dispersion polymerization. The resultant magnetic beads present well-defined composite structures, excellent colloidal stability, and strong magnetic response. The formation mechanism for the monodispersed composite beads, incorporated with preformed Fe(3) O(4) nanocrystals, was investigated. The potential applications of the monodispersed magnetic beads in bacteria capturing were demonstrated. After being coated with anti-Salmonella CSA-1 antibody, the magnetic beads show capturing efficiencies of >99.4% in isolating Salmonella sp.

The role of cobalt ferrite magnetic nanoparticles in medical science

The nanotechnology industry is rapidly growing and promises that the substantial changes that will have significant economic and scientific impacts be applicable to a wide range of areas, such as aerospace engineering, nano-electronics, environmental remediation and medical healthcare. In this area, cobalt ferrite nanoparticles have been regarded as one of the competitive candidates because of their suitable physical, chemical and magnetic properties like the high anisotropy constant, high coercivity and high Curie temperature, moderate saturation magnetization and ease of synthesis. This paper introduces the magnetic properties, synthesis methods and some medical applications, including the hyperthermia, magnetic resonance imaging (MRI), magnetic separation and drug delivery of cobalt ferrite nanoparticles.

Multiphasic DNA adsorption to silica surfaces under varying buffer, pH, and ionic strength conditions

Reversible interactions between DNA and silica are utilized in the solid phase extraction and purification of DNA from complex samples. Chaotropic salts commonly drive DNA binding to silica but inhibit DNA polymerase amplification. We studied DNA adsorption to silica using conditions with or without chaotropic salts through bulk depletion and quartz crystal microbalance (QCM) experiments. While more DNA adsorbed to silica using chaotropic salts, certain buffer conditions without chaotropic salts yielded a similar amount of eluted DNA. QCM results indicate that under stronger adsorbing conditions the adsorbed DNA layer is initially rigid but becomes viscoelastic within minutes. These results qualitatively agreed with a mathematical model for a multiphasic adsorption process. Buffer conditions that do not require chaotropic salts can simplify protocols for nucleic acid sample preparation. Understanding how DNA adsorbs to silica can help optimize nucleic acid sample preparation for clinical diagnostic and research applications.

G-quadruplex-forming oligonucleotide conjugated to magnetic nanoparticles: synthesis, characterization, and enzymatic stability assays

In the present work, we report the conjugation of superparamagnetic nanoparticles to a fluorescently labeled oligodeoxyribonucleotide (ODN) able to fold into stable unimolecular guanine quadruple helix under proper ion conditions by means of its thrombin-binding aptamer (TBA) sequence. The novel modified ODN, which contained a fluorescent dU(Py) unit at 3'-end and a 12-amino-dodecyl spacer (C(12)-NH(2)) at 5' terminus, was characterized by ESI-MS and optical spectroscopy (UV, CD, fluorescence), and analyzed by RP-HPLC chromatography and electrophoresis. From CD and fluorescence experiments, we verified that dU(Py) and C(12)-NH(2) incorporation does not interfere with the conformational stability of the G-quadruplex. Subsequently, the conjugation of the pyrene-labeled ODN with the magnetite particles was performed, and the ODN-conjugated nanoparticles were studied through optical spectroscopy (UV, CD, fluorescence) and by enzymatic and chemical assays. We found that the nanoparticles enhanced the stability of the TBA ODN to enzymatic degradation. Finally, we evaluated the amount of the TBA-conjugated nanoparticles immobilized on a magnetic separator in view of the potential use of the nanosystem for the magnetic capture of thrombin from complex mixtures.

Chitosan functionalized magnetic particle-assisted detection of genetically modified soybeans based on polymerase chain reaction and capillary electrophoresis

The high quality of DNA template is one of the key factors to ensure the successful execution of polymerase chain reaction (PCR). Therefore, development of DNA extraction methods is very important. In this work, chitosan modified magnetic particles (MPs) were synthesized and employed for extraction of genomic DNA from genetically modified (GM) soybeans. The extraction protocol used aqueous buffers for DNA binding to and releasing from the surface of the MPs based on the pH inducing the charge switch of amino groups in chitosan modified MPs. The extracted DNA was pure enough (A(260)/A(280)=1.85) to be directly used as templates for PCR amplification. In addition, the PCR products were separated by capillary electrophoresis for screening of GM organisms. The developed DNA extraction method using chitosan modified MPs was capable of preparation of DNA templates, which were PCR inhibitor free and ready for downstream analysis. The whole process for DNA extraction and detection was preferable to conventional methods (phenol-chloroform extraction, PCR, and gel electrophoresis) due to its simplicity and rapidity as well as its avoiding the use of toxic reagents and PCR inhibitors.

Challenges in environmental detection of human viral pathogens

There is substantial potential for human exposure to viruses in environmental matrixes. Identification of virally contaminated environmental reservoirs requires assays with sufficient sensitivity to detect low copy numbers of viral targets. However, low detection sensitivity frequently requires sample concentration during which inhibitors to downstream assays co-isolate with desired target. Conventional detection assays (e.g., cell culture, polymerase chain reaction) require a priori selection of appropriate cell lines or primers and probes based on the viruses anticipated to be present in the sample. This can underestimate exposure risks by excluding unidentified or unknown virus. Emerging methods including nonspecific adsorption/elution, filtration, and total nucleic acid sequencing, that are capable of concentrating, purifying, and detecting total virus and/or total virus nucleic acid will aid in estimates of exposure risk, source tracking, intervention efficacy, and evaluation of virus fate and transport. Development and implementation of novel virus detection techniques must integrate quality assurance guidelines to validate results and provide opportunities for interstudy comparison.

The use of strong anion-exchange (SAX) magnetic particles for the extraction of therapeutic siRNA and their analysis by liquid chromatography/mass spectrometry

Traditional methods for extracting oligonucleotides from serum and other biological fluids are often time-consuming and require multiple steps. Magnetic particle based separation of oligonucleotides has gained importance recently due to the advantages of simplicity and high efficiency. Here we report the development and optimization of commercially available strong anion-exchange (SAX) magnetic beads for the extraction of siRNA from human serum. The beads allowed for rapid extraction of siRNA from human serum in 100-200 μL of liquid chromatography/mass spectrometry (LC/MS)-compatible buffer in less than 1 h for a 96-well plate with no further drying steps. Due to the strong cation-binding properties of oligonucleotides, volatile ammonium salts such as triethylammonium bicarbonate (TEAB), ammonium bicarbonate, and NH(4) Cl were used to elute the siRNA from the beads. For more hydrophobic siRNA sequences, the addition of 5-10% organic solvent was required for elution. The recovery of chemically modified siRNA from human serum was around 80% for two types of beads examined; however, the recovery for highly modified sequences differed greatly between the two types of beads. In addition to extracting highly modified oligonucleotides, the SAX beads were also able to extract liposomal formulated siRNAs from serum with no interference from the lipid formulation. The extraction of siRNA from human serum was linear over the tested range of 50 ng/mL to 10 µg/mL. Using this extraction methodology, we have created a workflow to monitor siRNA serum stability by LC/MS. Initial observations confirm that RNase A type degradation with strand cleavage on the 3' side of uridine or cytosine is the dominant cleavage pattern in serum. This finding has implications for the selection and modification of therapeutic siRNAs and demonstrates the utility of magnetic beads as a simple and rapid extraction technique for siRNA.

Development of a single-step subtraction method for eukaryotic 18S and 28S ribonucleic acids

The abundance of mammalian 18S and 28S ribosomal RNA can decrease the detection sensitivity of bacterial or viral targets in complex host-pathogen mixtures. A method to capture human RNA in a single step was developed and characterized to address this issue. For this purpose, capture probes were covalently attached to magnetic microbeads using a dendrimer linker and the solid phase was tested using rat thymus RNA (mammalian components) with Escherichia coli RNA (bacterial target) as a model system. Our results indicated that random capture probes demonstrated better performance than specific ones presumably by increasing the number of possible binding sites, and the use of a tetrame-thylammonium-chloride (TMA-Cl-) based buffer for the hybridization showed a beneficial effect in the selectivity. The subtraction efficiency determined through real-time RT-PCR revealed capture-efficiencies comparable with commercially available enrichment kits. The performance of the solid phase can be further fine tuned by modifying the annealing time and temperature.

A completely automated sample preparation instrument and consumable device for isolation and purification of nucleic acids

Molecular diagnostic analysis and life science studies are dependent on the ability to effectively prepare samples for analysis. We report the development of a system that enables robust sample preparation of nucleic acids. To enable completely automated sample preparation, a consumable cartridge and consumable module system were developed to emulate every step of the sample preparation process. This included enzyme and reagent addition, temperature-controlled incubations, noncontact mixing of enzymes and reagents, buffer exchanges, and sample elution. Using this system, completely automated methods were developed for the purification of viral RNA and DNA from plasma and whole blood and of bacterial genomic DNA from water and whole blood. Extracted nucleic acids were detected and quantified using real-time PCR. The data indicate that automated viral DNA extraction was more efficient than sample extractions performed using a manual process, whereas automated total RNA extraction from the same samples was equivalent to controls. Additionally, we found that the process for bacterial genomic DNA extraction from either water or whole blood was equivalent to the manual extraction processes. We conclude the instrument, consumable cartridge, and reagent system enables easy, cost-effective, and robust sample preparation regardless of the experience of the operator.

Optical detection systems using immobilized aptamers

Advances in the development and the applications of optical biosensing systems based on immobilized aptamers are presented. These nucleic acid sequences have been used as new molecular recognition elements to develop heterogeneous assays, biosensors and microarrays. Among different detection modes that have been employed, optical ones which are described here are among the most used. Since their first report in 1996, numerous optical detection systems using aptamers and mainly based on fluorescence have been developed. Two main approaches have been used: label-based (using fluorophore, luminophore, enzyme, nanoparticles) or aptamer label-free detection systems (e.g. surface plasmon resonance, optical resonance). Most methods are based on a labeling approach. Some targets can be optically detected using not only colorimetry, chemiluminescence or the most developed fluorescence mode but also more recent non conventional optical methods such as surface plasmon-coupled directional emission (SPCDE). The first SPCDE-based aptasensor for thrombin detection has recently been reported in 2009. Aptasensors based on surface-enhanced Raman scattering spectroscopy (SERS) which presents advantages compared to fluorescence have also been described. Different label-free techniques have recently been shown to be suitable for developing performant aptasensors or aptamer-based microarrays, such as surface plasmon resonance (SPR), diffraction grating, evanescent-field-coupled (EFC) waveguide-mode, optical resonance or Brewster angle straddle interferometry (BASI). Important advances have been realized on optical aptamer-based detection systems that appear as highly efficient devices with enormous potential.

Advances in DNA-based techniques for the detection of seafood species substitution on the commercial market

Increased worldwide trade and processing of seafood has increased the potential for species substitution on the commercial market. To detect and prevent species substitution, several deoxyribonucleic acid (DNA)-based methods have been developed that can be used to identify species in a variety of food types. For large-scale applications, such as regulatory screening, these methods must be rapid, cost-effective, reliable, and have high potential for automation. This review highlights recent technological advances in DNA-based identification methods, with a focus on seafood species identification in automated, high-throughput settings. Advances in DNA isolation methods include silica-based columns for use in high-throughput operations and magnetic bead particles for increased and targeted recovery of DNA. The three most widely used methods for seafood species identification (polymerase chain reaction [PCR] sequencing, PCR-restriction fragment length polymorphism, and species-specific PCR) will be discussed, with a focus on the incorporation of technologies such as rapid PCR cycling, microfluidic chips, and real-time PCR. Emerging methods, including DNA microarrays and next-generation sequencing will also be explored for their potential to identify seafood species on a large scale. Overall, many of the technological advances discussed here offer complementary properties that will enable species identification in a variety of settings and with a range of products.

Efficient and scalable serial extraction of DNA and RNA from frozen tissue samples

Advances in cancer genomics have created a demand for scalable sample processing. We here present a process for serial extraction of nucleic acids from the same frozen tissue sample based on magnetic silica particles. The process is automation friendly with high recoveries of pure DNA and RNA suitable for analysis.

HIV diagnostics: challenges and opportunities

Accurate HIV diagnostic testing continues to pose challenges, but there are also opportunities for assay performance improvements in key areas for specific intended-use settings. The genetic diversity of HIV can result in false and discordant results in assays that fail to detect new variant strains. The use of antiretroviral therapies has resulted in drug-resistant variants that require monitoring by sequencing and genotyping methods. Nucleic acid testing is the most sensitive and reliable platform for detection, but it is costly and limited to centralized testing facilities, making implementation difficult in resource-limited settings where HIV has hit the hardest. Rapid antibody tests suitable for point-of-care use are becoming more accessible in resource-limited settings, but these tests may not detect HIV during the acute infection stage. Emerging antigen/antibody combination assays are viable alternatives to nucleic acid testing for diagnosis of recent infections. Although patient monitoring (e.g., via CD4+ T-cell count and viral load determination) and infant diagnoses still rely on clinical laboratory-based testing, point-of-care options are being developed. There are other technical challenges to HIV diagnostic testing and emerging biodetection technologies that may be able to address them, but they are not yet proven.

Immiscible phase nucleic acid purification eliminates PCR inhibitors with a single pass of paramagnetic particles through a hydrophobic liquid

Extraction and purification of nucleic acids from complex biological samples for PCR are critical steps because inhibitors must be removed that can affect reaction efficiency and the accuracy of results. This preanalytical processing generally involves capturing nucleic acids on microparticles that are then washed with a series of buffers to desorb and dilute out interfering substances. We have developed a novel purification method that replaces multiple wash steps with a single pass of paramagnetic particles (PMPs) though an immiscible hydrophobic liquid. Only two aqueous solutions are required: a lysis buffer, in which nucleic acids are captured on PMPs, and an elution buffer, in which they are released for amplification. The PMPs containing the nucleic acids are magnetically transported through a channel containing liquid wax that connects the lysis chamber to the elution chamber in a specially designed cartridge. Transporting PMPs through the immiscible phase yielded DNA and RNA as pure as that obtained after extensive wash steps required by comparable purification methods. Our immiscible-phase process has been applied to targets in whole blood, plasma, and urine and will enable the development of faster and simpler purification systems.

Magnetic barcoded hydrogel microparticles for multiplexed detection

Magnetic polymer particles have been used in a wide variety of applications ranging from targeting and separation to diagnostics and imaging. Current synthesis methods have limited these particles to spherical or deformations of spherical morphologies. In this paper, we report the use of stop flow lithography to produce magnetic hydrogel microparticles with a graphical code region, a probe region, and a magnetic tail region. These anisotropic multifunctional magnetic polymer particles are an enhanced version of previously synthesized "barcoded" particles (Science, 2007, 315, 1393-1396) developed for the sensitive and rapid multiplexed sensing of nucleic acids. The newly added magnetic region has acquired dipole moments in the presence of weak homogeneous magnetic fields, allowing the particles to align along the applied field direction. The novel magnetic properties have led to practical applications in the efficient orientation and separation of the barcoded microparticles during biological assays without disrupting detection capabilities.

Comparative evaluation of two automated systems for nucleic acid extraction of BK virus: NucliSens easyMAG versus BioRobot MDx

The objective of this study was to compare the performance of two automated nucleic acid extraction systems. Specifically, the NucliSens easyMAG system (bioMerieux, Marcy l'Etoile, France), which incorporates magnetic bead technology, was compared with the BioRobot MDx system (Qiagen GmbH, Hilden, Germany), which uses a silica membrane-based method of nucleic acid extraction. Nucleic acids from the BK virus (BKV DNA) were extracted from 98 plasma and 57 urine specimens using the Real-Q BKV quantitation kit (Biosewoom, Seoul, Korea). Failed PCR was defined as negative BKV DNA results having more than 36 threshold cycles of the internal control by the manufacturer's instruction. The PCR failure rate of nucleic acids isolated from plasma samples using the MDx system was similar to that of plasma samples processed using the easyMAG system (2.0% and 3.1%, respectively). The PCR failure rate of nucleic acids isolated from urine samples using the MDx system was higher than that of urine samples processed using the easyMAG system (33.3% and 12.5%, respectively). These data suggest that the PCR inhibitors present in urine specimens are removed more efficiently by the easyMAG system. Among amplified specimens, the discordant results obtained from the two systems revealed that the BKV DNA load ranged from 2.3 log10 copies/mL to 4.6 log10 copies/mL. Of the 25 urine specimens that yielded BKV DNA by both extraction systems, 15 specimens (60.0%) yielded higher BKV DNA loads by the easyMAG system, indicating that the easyMAG system extracted nucleic acid more efficiently than did the MDx system. In conclusion, the easyMAG method outperformed the MDx method when used to extract BKV DNA from urine samples. Magnetic bead-based extraction methods such as the easyMAG system are therefore preferable for the quantitation of viral DNA in urine.

Biomedical applications of distally controlled magnetic nanoparticles

Nano-sized magnetic particles are increasingly being used across a wide spectrum of biomedical fields. Upon functionalization to enable specific binding, magnetic particles and their targets can be conveniently positioned in vitro and in vivo by the distal application of magnetic fields. Furthermore, such particles can be magnetically heated after reaching their in vivo targets, thus inducing localized cell death that has a considerable therapeutic value in, for instance, cancer therapy. In this context, innovative biomedical research has produced novel applications that have exciting clinical potential. Such applications include magnetically enhanced transfection, magnetically assisted gene therapy, magnetically induced hyperthermia and magnetic-force-based tissue engineering, and the principles and utilities of these applications will be discussed here.