Magnetic nanoparticle drug carriers and their study by quadrupole magnetic field-flow fractionation

Field-Flow Fractionation in Molecular Biology and Biotechnology

Field-flow fractionation (FFF) is a family of single-phase separative techniques exploited to gently separate and characterize nano- and microsystems in suspension. These techniques cover an extremely wide dynamic range and are able to separate analytes in an interval between a few nm to 100 µm size-wise (over 15 orders of magnitude mass-wise). They are flexible in terms of mobile phase and can separate the analytes in native conditions, preserving their original structures/properties as much as possible. Molecular biology is the branch of biology that studies the molecular basis of biological activity, while biotechnology deals with the technological applications of biology. The areas where biotechnologies are required include industrial, agri-food, environmental, and pharmaceutical. Many species of biological interest belong to the operational range of FFF techniques, and their application to the analysis of such samples has steadily grown in the last 30 years. This work aims to summarize the main features, milestones, and results provided by the application of FFF in the field of molecular biology and biotechnology, with a focus on the years from 2000 to 2022. After a theoretical background overview of FFF and its methodologies, the results are reported based on the nature of the samples analyzed.

The Power of Field-Flow Fractionation in Characterization of Nanoparticles in Drug Delivery

Asymmetric-flow field-flow fractionation (AF4) is a gentle, flexible, and powerful separation technique that is widely utilized for fractionating nanometer-sized analytes, which extend to many emerging nanocarriers for drug delivery, including lipid-, virus-, and polymer-based nanoparticles. To ascertain quality attributes and suitability of these nanostructures as drug delivery systems, including particle size distributions, shape, morphology, composition, and stability, it is imperative that comprehensive analytical tools be used to characterize the native properties of these nanoparticles. The capacity for AF4 to be readily coupled to multiple online detectors (MD-AF4) or non-destructively fractionated and analyzed offline make this technique broadly compatible with a multitude of characterization strategies, which can provide insight on size, mass, shape, dispersity, and many other critical quality attributes. This review will critically investigate MD-AF4 reports for characterizing nanoparticles in drug delivery, especially those reported in the last 10-15 years that characterize multiple attributes simultaneously downstream from fractionation.

Research progress of stimulus-responsive antibacterial materials for bone infection

Infection is one of the most serious complications harmful to human health, which brings a huge burden to human health. Bone infection is one of the most common and serious complications of fracture and orthopaedic surgery. Antibacterial treatment is the premise of bone defect healing. Among all the antibacterial strategies, irritant antibacterial materials have unique advantages and the ability of targeted therapy. In this review, we focus on the research progress of irritating materials, the development of antibacterial materials and their advantages and disadvantages potential applications in bone infection.

Iron-Based Ceramic Composite Nanomaterials for Magnetic Fluid Hyperthermia and Drug Delivery

Because of the unique physicochemical properties of magnetic iron-based nanoparticles, such as superparamagnetism, high saturation magnetization, and high effective surface area, they have been applied in biomedical fields such as diagnostic imaging, disease treatment, and biochemical separation. Iron-based nanoparticles have been used in magnetic resonance imaging (MRI) to produce clearer and more detailed images, and they have therapeutic applications in magnetic fluid hyperthermia (MFH). In recent years, researchers have used clay minerals, such as ceramic materials with iron-based nanoparticles, to construct nanocomposite materials with enhanced saturation, magnetization, and thermal effects. Owing to their unique structure and large specific surface area, iron-based nanoparticles can be homogenized by adding different proportions of ceramic minerals before and after modification to enhance saturation magnetization. In this review, we assess the potential to improve the magnetic properties of iron-based nanoparticles and in the preparation of multifunctional composite materials through their combination with ceramic materials. We demonstrate the potential of ferromagnetic enhancement and multifunctional composite materials for MRI diagnosis, drug delivery, MFH therapy, and cellular imaging applications.

Combined Magnetic Hyperthermia and Photothermia with Polyelectrolyte/Gold-Coated Magnetic Nanorods

Magnetite nanorods (MNRs) are synthesized based on the use of hematite nanoparticles of the desired geometry and dimensions as templates. The nanorods are shown to be highly monodisperse, with a 5:1 axial ratio, and with a 275 nm long semiaxis. The MNRs are intended to be employed as magnetic hyperthermia and photothermia agents, and as drug vehicles. To achieve a better control of their photothermia response, the particles are coated with a layer of gold, after applying a branched polyethyleneimine (PEI, 2 kDa molecular weight) shell. Magnetic hyperthermia is performed by application of alternating magnetic fields with frequencies in the range 118-210 kHz and amplitudes up to 22 kA/m. Photothermia is carried out by subjecting the particles to a near-infrared (850 nm) laser, and three monochromatic lasers in the visible spectrum with wavelengths 480 nm, 505 nm, and 638 nm. Best results are obtained with the 505 nm laser, because of the proximity between this wavelength and that of the plasmon resonance. A so-called dual therapy is also tested, and the heating of the samples is found to be faster than with either method separately, so the strengths of the individual fields can be reduced. Due to toxicity concerns with PEI coatings, viability of human hepatoblastoma HepG2 cells was tested after contact with nanorod suspensions up to 500 µg/mL in concentration. It was found that the cell viability was indistinguishable from control systems, so the particles can be considered non-cytotoxic in vitro. Finally, the release of the antitumor drug doxorubicin is investigated for the first time in the presence of the two external fields, and of their combination, with a clear improvement in the rate of drug release in the latter case.

An overview and bibliometric analysis on the colorectal cancer therapy by magnetic functionalized nanoparticles for the responsive and targeted drug delivery

With the growing demands for personalized medicine and medical devices, nanomedicine is a modern scientific field, and research continues to apply nanomaterials for therapeutic and damaged tissue diagnosis. In this regard, substantial progress has been made in synthesizing magnetic nanoparticles with desired sizes, chemical composition, morphologies, and surface chemistry. Among these materials, nanomagnetic iron oxides have demonstrated promise as unique drug delivery carriers due to cancer treatment. This carrier could lead to responsive properties to a specific trigger, including heat, pH, alternative magnetic field, or even enzymes, through functionalization and coating of magnetic nanoparticles, along with biocompatibility, good chemical stability, easy functionalization, simple processing, and ability to localize to the tumor site with the assistance of external magnetic field. Current studies have focused on magnetic nanoparticles' utilities in cancer therapy, especially for colorectal cancer. Additionally, a bibliometric investigation was performed on the public trends in the field of the magnetic nanoparticle to drug delivery and anticancer, which represented progressing applications of these carriers in the multidisciplinary zones with a general view on future research and identified potential opportunities and challenges. Furthermore, we outline the current challenges and forthcoming research perspective for high performance and fostering advanced MNPs in colorectal cancer treatment.

Biomimetic Magnetite Nanoparticles as Targeted Drug Nanocarriers and Mediators of Hyperthermia in an Experimental Cancer Model

Simple Summary

The application of simultaneous and different strategies to treat cancer appears a promising therapeutic approach. Herein we proposed the application of chemotherapy combined with a magnetic nanocarrier delivery system to an in vitro and an in vivo experimental mammary carcinoma model. Drug-loaded biomimetic magnetic nanoparticle can be directed and concentrated on the tumor cells or site by the apposition of a magnet. Moreover, these nanoparticles can respond to an alternating magnetic field by developing hyperthermia around 43 °C, a temperature at which tumor cells, but not healthy cells, are particularly sensitive and thus induced to death. Indeed, when this nanoformulation is injected in vivo in the tumor site, and hyperthermia is generated, the combined chemo-thermal therapy mediated by these drug-loaded magnetic nanoparticles have a stronger therapeutic benefit compared to that carried out by the chemotherapeutic alone. These nanoformulation and strategy are thus promising tools for translational applications in cancer therapy.

Abstract

Biomimetic magnetic nanoparticles mediated by magnetosome proteins (BMNPs) are potential innovative tools for cancer therapy since, besides being multifunctional platforms, they can be manipulated by an external gradient magnetic field (GMF) and/or an alternating magnetic field (AMF), mediating targeting and hyperthermia, respectively. We evaluated the cytocompatibility/cytotoxicity of BMNPs and Doxorubicin (DOXO)-BMNPs in the presence/absence of GMF in 4T1 and MCF-7 cells as well as their cellular uptake. We analyzed the biocompatibility and in vivo distribution of BMNPs as well as the effect of DOXO-BMNPs in BALB/c mice bearing 4T1 induced mammary carcinomas after applying GMF and AMF. Results: GMF enhanced the cell uptake of both BMNPs and DOXO-BMNPs and the cytotoxicity of DOXO-BMNPs. BMNPs were biocompatible when injected intravenously in BALB/c mice. The application of GMF on 4T1 tumors after each of the repeated (6×) iv administrations of DOXO-BMNPs enhanced tumor growth inhibition when compared to any other treatment, including that with soluble DOXO. Moreover, injection of DOXO-BMNPs in the tumor combined with application of an AMF resulted in a significant tumor weight reduction. These promising results show the suitability of BMNPs as magnetic nanocarriers for local targeted chemotherapy and as local agents for hyperthermia.

Recent Advances in Continuous-Flow Particle Manipulations Using Magnetic Fluids

Magnetic field-induced particle manipulation is simple and economic as compared to other techniques (e.g., electric, acoustic, and optical) for lab-on-a-chip applications. However, traditional magnetic controls require the particles to be manipulated being magnetizable, which renders it necessary to magnetically label particles that are almost exclusively diamagnetic in nature. In the past decade, magnetic fluids including paramagnetic solutions and ferrofluids have been increasingly used in microfluidic devices to implement label-free manipulations of various types of particles (both synthetic and biological). We review herein the recent advances in this field with focus upon the continuous-flow particle manipulations. Specifically, we review the reported studies on the negative magnetophoresis-induced deflection, focusing, enrichment, separation, and medium exchange of diamagnetic particles in the continuous flow of magnetic fluids through microchannels.

Robust synthesis of sugar-coumarin based fluorescent 1,4-disubstituted-1,2,3-triazoles using highly efficient recyclable citrate grafted β-cyclodextrin@magnetite nano phase transfer catalyst in aqueous media

Green synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction using nano magnetic Fe₃O₄ core decorated with cyclodextrin-citric acid (Fe₃O₄@CD-CIT) acting as a phase transfer nanoreactor with low copper loading under ultrasonication at 40 °C, in aqueous media is described. Anchoring the surface of magnetite with cyclodextrin (CD) prevents its agglomeration and at the same time, CD provides a hydrophobic niche for lipophilic reactants while its outer hydrophilic core makes the reaction feasible in water yielding almost quantitative yield of desired products. Magnetic separation using an external magnet, recyclability and reuse (7 times), without appreciably affecting the %yield of the products are its other attractive attributes. Gram scale synthesis was also achieved with 93% yield.

Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential

In this work novel magnetic cationic liposomal nanoformulations were synthesized for the encapsulation of a crystallographically defined ternary V(IV)-curcumin-bipyridine (VCur) complex with proven bioactivity, as potential anticancer agents. The liposomal vesicles were produced via the thin film hydration method employing N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP) and egg phosphatidylcholine lipids and were magnetized through the addition of citric acid surface-modified monodispersed magnetite colloidal magnetic nanoparticles. The obtained nanoformulations were evaluated for their structural and textural properties and shown to have exceptional stability and enhanced solubility in physiological media, demonstrated by the entrapment efficiency and loading capacity results and the in vitro release studies of their cargo. Furthermore, the generated liposomal formulations preserved the superparamagnetic behavior of the employed magnetic core maintaining the physicochemical and morphological requirements for targeted drug delivery applications. The novel nanomaterials were further biologically evaluated for their DNA interaction potential and were found to act as intercalators. The findings suggest that the positively charged magnetic liposomal nanoformulations can generate increased concentration of their cargo at the DNA site, offering a further dimension in the importance of cationic liposomes as nanocarriers of hydrophobic anticancer metal ion complexes for the development of new multifunctional pharmaceutical nanomaterials with enhanced bioavailability and targeted antitumor activity.

Magnetic Drug Delivery: Where the Field Is Going

Targeted delivery of anticancer drugs is considered to be one of the pillars of cancer treatment as it could allow for a better treatment efficiency and less adverse effects. A promising drug delivery approach is magnetic drug targeting which can be realized if a drug delivery vehicle possesses a strong magnetic moment. Here, we discuss different types of magnetic nanomaterials which can be used as magnetic drug delivery vehicles, approaches to magnetic targeted delivery as well as promising strategies for the enhancement of the imaging-guided delivery and the therapeutic action.

Functional Diagnostic and Therapeutic Nanoconstructs for Efficient Probing of Circulating Tumor Cells

The circulation of tumor cells in peripheral blood is mostly recognized as a prerequisite for cancer progression or systemic invasion, and it correlates with the pivotal hallmark of malignancies known as metastasis. Multiple detection schemes for circulating tumor cells (CTCs) have emerged as the most discerning criteria for monitoring the outcome of anticancer therapy. Therefore, there has been a tremendous increase in the use of robust nanostructured platforms for observation of these mobile tumor cells through various simultaneous diagnosis and treatment regimens developed from conventional techniques. This review seeks to give detailed information about the nature of CTCs as well as techniques for exploiting specific biomarkers to help monitor cancer via detection, capturing, and analysis of unstable tumor cells. We will further discuss nanobased diagnostic interventions and novel platforms which have recently been developed from versatile nanomaterials such as polymer nanocomposites, metal organic frameworks, bioderived nanomaterials and other physically responsive particles with desirable intrinsic and external properties. Herein, we will also include in vivo nanotheranostic platforms which have received a lot of attention because of their enormous clinical potential. In all, this review sums up the general potential of key promising nanoinspired systems as well as other advanced strategies under research and those in clinical use.

Magnetic Drug Targeting: Preclinical in Vivo Studies, Mathematical Modeling, and Extrapolation to Humans

A sound theoretical rationale for the design of a magnetic nanocarrier capable of magnetic capture in vivo after intravenous administration could help elucidate the parameters necessary for in vivo magnetic tumor targeting. In this work, we utilized our long-circulating polymeric magnetic nanocarriers, encapsulating increasing amounts of superparamagnetic iron oxide nanoparticles (SPIONs) in a biocompatible oil carrier, to study the effects of SPION loading and of applied magnetic field strength on magnetic tumor targeting in CT26 tumor-bearing mice. Under controlled conditions, the in vivo magnetic targeting was quantified and found to be directly proportional to SPION loading and magnetic field strength. Highest SPION loading, however, resulted in a reduced blood circulation time and a plateauing of the magnetic targeting. Mathematical modeling was undertaken to compute the in vivo magnetic, viscoelastic, convective, and diffusive forces acting on the nanocapsules (NCs) in accordance with the Nacev-Shapiro construct, and this was then used to extrapolate to the expected behavior in humans. The model predicted that in the latter case, the NCs and magnetic forces applied here would have been sufficient to achieve successful targeting in humans. Lastly, an in vivo murine tumor growth delay study was performed using docetaxel (DTX)-encapsulated NCs. Magnetic targeting was found to offer enhanced therapeutic efficacy and improve mice survival compared to passive targeting at drug doses of ca. 5-8 mg of DTX/kg. This is, to our knowledge, the first study that truly bridges the gap between preclinical experiments and clinical translation in the field of magnetic drug targeting.

Antitumor effect of TRAIL on oral squamous cell carcinoma using magnetic nanoparticle-mediated gene expression

We developed a new magnetic nanovector to improve the efficiency and targeting of transgene therapy for oral squamous cell carcinoma (OSCC). Positively charged polymer PEI-modified Fe(3)O(4) magnetic nanoparticles were tested as gene transfer vectors in the presence of a magnetic field. The Fe(3)O(4) nanoparticles were prepared by a co-precipitation method and had good dispersibility in water. These nanoparticles modified by PEI were combined with negatively charged pACTERT-EGFP via electrostatic interaction. The transfection efficiency of the magnetic nano-gene vector with the magnetic field was determined by a fluorescence-inverted microscope and flow cytometry. The results showed significant improvement compared with the control group (p < 0.05). The magnetic complexes also exhibited up to 6-times higher transfection efficiency compared with commonly used PEI or lipofectin. On the basis of these results, the antitumor effect with suicide gene therapy using pACTERT-TRAIL in vitro and vivo was evaluated. In vitro apoptosis was determined with the Annexin V-FITC Apoptosis Detection Kit. The results suggested that PEI-modified Fe(3)O(4) nanoparticles could mediate the killing of Tca83 cells. Furthermore, treatment with pACTERT-TRAIL delivered by magnetic nanoparticles showed a significant cytostatic effect through the induction of apoptosis in a xenograft model. This indicates that magnetic nano-gene vectors could improve the transgene efficiency for Tca83 cells and could exhibit antitumor functions with the plasmid pACTERT-TRAIL. This may be a new way to treat OSCC.

Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow

Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures, require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation.

Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles

A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles.

Magnetophoresis at the nanoscale: tracking the magnetic targeting efficiency of nanovectors

Aim: Most of the research efforts in magnetic targeting have been focused on the development of magnetic nanovectors, while the investigation of methods for tracking their magnetic targeting efficiency remains inappropriately addressed. We propose herein a miniaturized approach for appraising magnetophoretic mobility at the nanoscale. Materials & methods: A simple and easy-to-use chamber including a microtip as a magnetic attractor was developed to perform magnetophoretic measurement at the size scale of nano-objects, and under bright field or fluorescence microscopy. Different sets of magnetic nanocontainers were produced and their magnetophoretic mobility was investigated. Real-time observations of the Brownian motion of the nanocontainers were also carried out for simultaneous size determination. Results: Attraction of the nanocontainers at the microtip is demonstrated as a qualitative method that immediately distinguishes magnetically responsive nano-objects. The combination of the analysis of Brownian motion, together with the magnetophoretic mobility, inferred both the size, the magnetophoretic velocity and the magnetic content of the nanocontainers. Additionally, nanomagnetophoresis experiments under fluorescence microscopy provided information on the constitutive core/shell integrity of the nanocontainers and the co-internalization of a fluorescent cargo. Conclusion: This nanomagnetophoresis method represents a promising tool to estimate the feasibility of magnetic targeting in laboratory routine.

Original submitted 28 November 2011; Revised submitted 28 February 2012; Published online 18 June 2012

Microfluidic synthesis of microfibers for magnetic-responsive controlled drug release and cell culture

This study demonstrated the fabrication of alginate microfibers using a modular microfluidic system for magnetic-responsive controlled drug release and cell culture. A novel two-dimensional fluid-focusing technique with multi-inlets and junctions was used to spatiotemporally control the continuous laminar flow of alginate solutions. The diameter of the manufactured microfibers, which ranged from 211 µm to 364 µm, could be well controlled by changing the flow rate of the continuous phase. While the model drug, diclofenac, was encapsulated into microfibers, the drug release profile exhibited the characteristic of a proper and steady release. Furthermore, the diclofenac release kinetics from the magnetic iron oxide-loaded microfibers could be controlled externally, allowing for a rapid drug release by applying a magnetic force. In addition, the successful culture of glioblastoma multiforme cells in the microfibers demonstrated a good structural integrity and environment to grow cells that could be applied in drug screening for targeting cancer cells. The proposed microfluidic system has the advantages of ease of fabrication, simplicity, and a fast and low-cost process that is capable of generating functional microfibers with the potential for biomedical applications, such as drug controlled release and cell culture.

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.

Review on the progress in synthesis and application of magnetic carbon nanocomposites

This review focuses on the synthesis and application of nanostructured composites containing magnetic nanostructures and carbon-based materials. Great progress in fabrication of magnetic carbon nanocomposites has been made by developing methods including filling process, template-based synthesis, chemical vapor deposition, hydrothermal/solvothermal method, pyrolysis procedure, sol-gel process, detonation induced reaction, self-assembly method, etc. The applications of magnetic carbon nanocomposites expanded to a wide range of fields such as environmental treatment, microwave absorption, magnetic recording media, electrochemical sensor, catalysis, separation/recognization of biomolecules and drug delivery are discussed. Finally, some future trends and perspectives in this research area are outlined.

Nanomaterials: applications in cancer imaging and therapy

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics that are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multimodal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge, physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and to achieve active targeting. This is stimulating the development of a diverse range of nanometer-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Doxorubicin loaded magnetic polymersomes: theranostic nanocarriers for MR imaging and magneto-chemotherapy

Hydrophobically modified maghemite (γ-Fe(2)O(3)) nanoparticles were encapsulated within the membrane of poly(trimethylene carbonate)-b-poly(l-glutamic acid) (PTMC-b-PGA) block copolymer vesicles using a nanoprecipitation process. This formation method gives simple access to highly magnetic nanoparticles (MNPs) (loaded up to 70 wt %) together with good control over the vesicles size (100-400 nm). The simultaneous loading of maghemite nanoparticles and doxorubicin was also achieved by nanoprecipitation. The deformation of the vesicle membrane under an applied magnetic field has been evidenced by small angle neutron scattering. These superparamagnetic hybrid self-assemblies display enhanced contrast properties that open potential applications for magnetic resonance imaging. They can also be guided in a magnetic field gradient. The feasibility of controlled drug release by radio frequency magnetic hyperthermia was demonstrated in the case of encapsulated doxorubicin molecules, showing the viability of the concept of magneto-chemotherapy. These magnetic polymersomes can be used as efficient multifunctional nanocarriers for combined therapy and imaging.

Quantification of nanoparticle uptake by cells using microscopical and analytical techniques

Quantification of nanoparticles in biological systems (i.e., cells, tissues and organs) is becoming a vital part of nanotoxicological and nanomedical fields. Dose is a key parameter when assessing behavior and any potential risk of nanomaterials. Various techniques for nanoparticle quantification in cells and tissues already exist but will need further development in order to make measurements reliable, reproducible and intercomparable between different techniques. Microscopy allows detection and location of nanoparticles in cells and has been used extensively in recent years to characterize nanoparticles and their pathways in living systems. Besides microscopical techniques (light microscopy and electron microscopy mainly), analytical techniques such as mass spectrometry, an established technique in trace element analysis, have been used in nanoparticle research. Other techniques require ‘labeled’ particles, fluorescently, radioactively or magnetically. However, these techniques lack spatial resolution and subcellular localization is not possible. To date, only electron microscopy offers the resolving power to determine accumulation of nanoparticles in cells due to its ability to image particles individually. So-called super-resolution light microscopy techniques are emerging to provide sufficient resolution on the light microscopy level to image or ‘see’ particles as individual particles. Nevertheless, all microscopy techniques require statistically sound sampling strategies in order to provide quantitative results. Stereology is a well-known sampling technique in various areas and, in combination with electron microscopy, proves highly successful with regard to quantification of nanoparticle uptake by cells.

Magnetic Drug Targeting in Partly Occluded Blood Vessels Using Magnetic Microspheres

Magnetic drug targeting can be used for treating stenosis and thrombosis in partly occluded blood vessels. Herein, a numerical investigation of magnetic drug targeting using functionalized magnetic microspheres in partly occluded blood vessels is conducted. An Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow. An implantable cylindrical permanent magnet insert is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted, and the influence of the flow Re, magnetic insert diameter, and its radial and axial position on the “targeting efficiency” is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug-carrying magnetic particles in a predesignated target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for an in vitro setup for the investigation of magnetic drug targeting in stenosed blood vessels.

Cytotoxic Activities of Silver Nanoparticles and Silver Ions in Parent and Tamoxifen-Resistant T47D Human Breast Cancer Cells and Their Combination Effects with Tamoxifen against Resistant Cells

Studies on biomedical applications of nanoparticles are growing with a rapid pace. In medicine, nanoparticles may be the solution for multi-drug-resistance which is still a major drawback in chemotherapy of cancer. In the present study, we investigated the potential cytotoxic effect of silver nanoparticles (Ag NPs) and silver ions (Ag(+)) in both parent and tamoxifen-resistant T47D cells in presence and absence of tamoxifen. Ag NPs were synthesized (< 28 nm) and MTT assay was carried out. The associated IC(50) values were found to be: 6.31 µg/ml for Ag NPs/parent cells, 37.06 µg/ml for Ag NPs/tamoxifen-resistant cells, 33.06 µg/ml for Ag(+)/parent cells and 10.10 µg/ml for Ag(+)/resistant cells. As a separate experiment, the effect of subinhibitory concentrations of Ag NPs and Ag(+) on the proliferation of tamoxifen-resistant cells was evaluated at non-toxic concentrations of tamoxifen. Our results suggested that in non-cytotoxic concentrations of silver nanomaterials and tamoxifen, the combinations of Ag(+)-tamoxifen and Ag NPs-tamoxifen are still cytotoxic. This finding may be of great potential benefit in chemotherapy of breast cancer; since much lower doses of tamoxifen may be needed to produce the same cytotoxic effect and side effects will be reduced.

Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation

Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery. Magnetic field-flow fractionation (MgFFF) has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation. This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected.

Magnetic Biotransport: Analysis and Applications

Magnetic particles are finding increasing use in bioapplications, especially as carrier particles to transport biomaterials such as proteins, enzymes, nucleic acids and whole cells etc. Magnetic particles can be prepared with biofunctional coatings to target and label a specific biomaterial, and they enable controlled manipulation of a labeled biomaterial using an external magnetic field. In this review, we discuss the use of magnetic nanoparticles as transport agents in various bioapplications. We provide an overview of the properties of magnetic nanoparticles and their functionalization for bioapplications. We discuss the basic physics and equations governing the transport of magnetic particles at the micro- and nanoscale. We present two different transport models: a classical Newtonian model for predicting the motion of individual particles, and a drift-diffusion model for predicting the behavior of a concentration of nanoparticles that takes into account Brownian motion. We review specific magnetic biotransport applications including bioseparation, drug delivery and magnetofection. We demonstrate the transport models via application to these processes.