Biodegradable Thermomagnetically Responsive Soft Untethered Grippers

Soft-robotic devices such as polymeric microgrippers offer the possibility for pick and place of fragile biological cargo in hard-to-reach conduits with potential applications in drug delivery, minimally invasive surgery, and biomedical engineering. Previously, millimeter-sized self-folding thermomagnetically responsive soft grippers have been designed, fabricated, and utilized for pick-and-place applications but there is a concern that such devices could get lost or left behind after their utilization in practical clinical applications in the human body. Consequently, strategies need to be developed to ensure that these soft-robotic devices are biodegradable so that they would disintegrate if left behind in the body. In this paper, we describe the photopatterning of bilayer gels composed of a thermally responsive high-swelling poly(oligoethylene glycol methyl ether methacrylate ( M_n = 500)-bis(2-methacryloyl)oxyethyl disulfide), P(OEGMA-DSDMA), and a low-swelling poly(acrylamide- N, N'-bis(acyloyl)cystamine) hydrogel, in the shape of untethered grippers. These grippers can change shape in response to thermal cues and open and close due to the temperature-induced swelling of the P(OEGMA-DSDMA) layer. We demonstrate that the grippers can be doped with magnetic nanoparticles so that they can be moved using magnetic fields or loaded with chemicals for potential applications as drug-eluting theragrippers. Importantly, they are also biodegradable at physiological body temperature (∼37 °C) on the basis of cleavage of disulfide bonds by reduction. This approach that combines thermoresponsive shape change, magnetic guidance, and biodegradability represents a significant advance to the safe implementation of untethered shape-changing biomedical devices and soft robots for medical and surgical applications.

Neoadjuvant nano-photothermal therapy used before operation effectively assists in surgery for breast cancer

Nano-photothermal therapy (NPTT) has attracted increasing interest recently due to its high efficiency, excellent selectivity and non-ionizing radiation damage. Despite a tremendous amount of exciting pre-clinical results reported in the past few years, however, the further clinic application of NPTT is still difficult. To combine NPTT with clinical surgery more closely, novel multifunctional optical-magnetic nanosystems have been synthesized and applied for preoperative NPTT to assist in the follow-up surgery, termed "neoadjuvant NPTT". Remarkably, nanoparticles are mainly aggregated in the cytoplasm of tumor cells in vitro and largely accumulated in the tumor in vivo 24 h after injection. Under the guidance of tri-modality imaging, preoperative NPTT could shrink the tumor in a short time and make the boundary between the tumor and surrounding normal tissues clearer, which is conducive to subsequent surgery resection. Furthermore, the 50% survival rate is up to 50 days compared with 35 days for standard surgery, 31 days for PTT alone and 24 days for non-surgery groups. Therefore, NPTT can effectively assist in surgery used before operation. This study provides a new idea for the clinical transformation of NPTT in the future.

Galbanic Acid-Coated Fe3O4 Magnetic Nanoparticles with Enhanced Cytotoxicity to Prostate Cancer Cells

Galbanic acid is a natural sesquiterpene coumarin compound with different biological activities, particularly cytotoxicity against LNCaP (an androgen-dependent prostate cancer cell line). Galbanic acid induces apoptosis in LNCaP via down-regulation of androgen receptor. However, the poor water-solubility of galbanic acid limits further in vitro and in vivo studies. In this study we present the synthesis of galbanic acid-coated Fe₃O₄ magnetic nanoparticles and their cytotoxicity evaluation on three prostate cancer cell lines, including PC3 (an androgen-independent cell line), LNCaP, and DU145 (an androgen-independent cell line). The synthesized nanoparticles were characterized by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, scattering electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and vibrating sample magnetometry. Our cytotoxicity evaluation demonstrated that galbanic acid was cytotoxic only against LNCaP cells, while the galbanic acid-coated Fe₃O₄ nanoparticles showed cytotoxicity on all tested cells, including androgen-dependent and -independent cell lines. This indicates that other mechanisms are involved in the cytotoxicity of galbanic acid in addition to androgen receptor down-regulation. In conclusion, the loading of galbanic acid on the surface of Fe₃O₄ magnetic nanoparticles turned out to be a successful approach to enhance the solubility and cytotoxicity of this compound.

MRI-Compatible Injection System for Magnetic Microparticle Embolization

OBJECTIVE

Dipole field navigation and magnetic resonance navigation exploit B₀ magnetic fields and imaging gradients for targeted intra-arterial therapies by using magnetic drug-eluting beads (MDEBs). The strong magnetic strength (1.5 or 3 T) of clinical magnetic resonance imaging (MRI) scanners is the main challenge preventing the formation and controlled injection of specific-sized particle aggregates. Here, an MRI-compatible injector is proposed to solve the above problem.

METHODS

The injector consists of two peristaltic pumps, an optical counter, and a magnetic trap. The magnetic property of microparticles, the magnetic compatibility of different parts within the injector, and the field distribution of the MRI system were studied to determine the optimal design and setup of the injector. The performance was investigated through 30.4-emu/g biocompatible magnetic microparticles (230 ± 35 μm in diameter) corresponding to the specifications needed for trans-arterial chemoembolization in human adults.

RESULTS

The system can form aggregates containing 20 to 60 microparticles with a precision of six particles. The corresponding aggregate lengths range from 1.6 to 3.2 mm. Based on the injections of 50 MRI-visible boluses into a phantom which mimics realistic physiological conditions, 82% of the aggregates successfully reached subbranches.

CONCLUSION AND SIGNIFICANCE

This system has the capability to operate within the strong magnetic field of a clinical 3-T MRI, to form proper particle aggregates and to automatically inject these aggregates into the MRI bore. Moreover, the versatility of the proposed injector renders it suitable for selective injections of MDEBs during MR-guided embolization procedures.

Triple-Modal Imaging-Guided Chemo-Photothermal Synergistic Therapy for Breast Cancer with Magnetically Targeted Phase-Shifted Nanoparticles

Current nanodrug-based cancer therapy is susceptible to the problems of rapid clearance from circulation and limited therapeutic efficacy. Herein, we report a magnetically targeted and photothermal-triggered drug release nanotheranostics system based on superparamagnetic iron oxide (Fe₃O₄), IR780, doxorubicin (DOX), and perfluoropentane (PFP) entrapped poly-lactide- co-glycolide (PLGA) nanoparticles (IR780/Fe₃O₄@PLGA/PFP/DOX NPs) for triple-modal imaging-guided synergistic therapy of breast cancer. In this work, IR780 and Fe₃O₄ convert light into heat, which triggers DOX release from IR780/Fe₃O₄@PLGA/PFP/DOX NPs and a phase-shift thermoelastic expansion of PFP; this procedure further accelerates the DOX release and tissue extrusion deformation. Fe₃O₄ NPs also serve as the target moiety by an external magnet directed to the tumor. Specifically, the IR780/Fe₃O₄@PLGA/PFP/DOX NPs can be used for triple-modal imaging, including near infrared fluorescence, magnetic resonance, and ultrasound. Furthermore, the antitumor therapy studies reveal the extraordinary performance of IR780/Fe₃O₄@PLGA/PFP/DOX NPs in magnetically targeted synergistic chemo-photothermal therapy of cancer. Therefore, the multifunctional IR780/Fe₃O₄@PLGA/PFP/DOX NPs guided by the magnetic field show a great potential for cancer theranostics.

Iron oxide-carbon core-shell nanoparticles for dual-modal imaging-guided photothermal therapy

Nanostructured materials that have low tissue toxicity, multi-modal imaging capability and high photothermal conversion efficiency have great potential to enable image-guided near infrared (NIR) photothermal therapy (PTT). Here, we report a bifunctional nanoparticle (BFNP, ∼16 nm) comprised of a magnetic Fe3O4 core (∼9.1 nm) covered by a fluorescent carbon shell (∼3.4 nm) and prepared via a one-pot solvothermal synthesis method using ferrocene as the sole source. The BFNP exhibits excitation wavelength-tunable, upconverted and near-infrared (NIR) fluorescence property due to the presence of the carbon shell, and superparamagnetic behavior resulted from the Fe3O4 core. BFNPs demonstrate dual-modal imaging capacity both in vitro and in vivo with fluorescent imaging excited under a varying wavelength from 405 nm to 820 nm and with T2-weighted magnetic resonance imaging (r2 = 264.76 mM-1 s-1). More significantly, BFNPs absorb and convert NIR light to heat enabling photothermal therapy as demonstrated mice bearing C6 glioblastoma. These BFNPs show promise as an advanced nanoplatform to provide imaging guided photothermal therapy.

Urokinase-Conjugated Magnetite Nanoparticles as a Promising Drug Delivery System for Targeted Thrombolysis: Synthesis and Preclinical Evaluation

Mortality and disabilities as outcomes of cardiovascular diseases are primarily related to blood clotting. Optimization of thrombolytic drugs is aimed at the prevention of side effects (in particular, bleeding) associated with a disbalance between coagulation and anticoagulation caused by systemically administered agents. Minimally invasive and efficient approaches to deliver the thrombolytic agent to the site of clot formation are needed. Herein, we report a novel nanocomposite prepared by heparin-mediated cross-linking of urokinase with magnetite nanoparticles (MNPs@uPA). We showed that heparin within the composition evoked no inhibitory effects on urokinase activity. Importantly, the magneto-control further increased the thrombolytic efficacy of the composition. Using our nanocomposition, we demonstrated efficient lysis of experimental clots in vitro and in animal vessels followed by complete restoration of blood flow. No sustained toxicity or hemorrhagic complications were registered in rats and rabbits after single bolus i.v. injection of therapeutic doses of MNPs@uPA. We conclude that MNPs@uPA is a prototype of easy-to-prepare, inexpensive, biocompatible, and noninvasive thrombolytic nanomedicines potentially useful in the treatment of blood clotting.

HP-β-CD Functionalized Fe3O4/CNPs-Based Theranostic Nanoplatform for pH/NIR Responsive Drug Release and MR/NIRFL Imaging-Guided Synergetic Chemo/Photothermal Therapy of Tumor

The combination of chemotherapy and photothermal therapy has aroused great interest due to its better antitumor effect than either single therapy alone. Herein, we report on the development of hydroxypropyl-β-cyclodextrin functionalized Fe₃O₄/carbon nanoparticles (HFCNPs) for pH/near-infrared (NIR) responsive drug release, magnetic resonance/NIR fluorescence (MR/NIRFL) imaging-guided combined chemo/photothermal therapy. The high doxorubicin (DOX) loading capacity (61.2%) and controlled drug release by NIR irradiation and weak acid microenvironment render HFCNPs a good vector for DOX delivery and controlled release. Moreover, the MR/NIRFL dual-modal imaging was used to define the tumor location, size, and boundary and to track the tumor accumulation of HFCNPs and their biodistribution. The efficient accumulation and prolonged retention time of the nanoparticles in tumor are beneficial to tumor therapy. Taking advantage of the NIR laser-induced heating and hence promoted drug permeation, remarkable tumor inhibition was realized by synergetic chemo/photothermal therapy. In conclusion, the current work offers a promising approach to the development of smart and efficient multimodal cancer-targeted nanotheranostics.

BNNT/Fe₃O₄ System as an Efficient Tool for Magnetohyperthermia Therapy

Nanostructured materials have been widely studied aiming to biomedical applications, primarily for the purpose of carrying drugs or molecules of interest in a selected tissue or organ. In this context, boron nitride nanotubes (BNNTs), when functionalized with specific moieties, could be useful as nanovectors for delivery of proteins, drugs, and also RNAi molecules, due to their capacity to be uptaked by cells. The introduction of magnetic nanoparticles allows the use of such system as a hyperthermia agent. Thus, once it has been targeted to tumor areas, it could kill cancer cells by magnetohyperthermia therapy. In order to study this effect, magnetite nanoparticles were incorporated into hydroxilated BNNT. The system was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The results obtained show that magnetite nanoparticles are linked to the nanotubes. Magnetic measurements show that coercivity and magnetization were not disturbed after incorporation to the BNNT. Based on this, a new methodology for in vitro magnetohyperthermia experiments was developed, aiming to treat each cell group individually preserving its sterility. The biological assays of the system demonstrate its good cell viability and the great potential of this nanomaterial as a magnetohyperthermia agent for cancer treatment.

Neuroregenerative Effects of Electromagnetic Field and Magnetic Nanoparticles on Spinal Cord Injury in Rats

The present study aimed to evaluate the effect of iron oxide nanoparticles (IONPs) along with electromagnetic fields (MF) exposure on spontaneous and induced axonal sprouting after spinal cord injury (SCI). Adult male Wistar rats were subjected to spinal cord transection at the T13 segment. The IONP (25 μg/mL) embedded in 3% agarose gel was implanted at the injury site and subsequently exposed to MF (50 Hz, 17.96 μT, 2 hours/day for 5 weeks). Histological analysis of spinal cord tissue showed a significant increase in the expression of the growth-associated protein GAP-43 and it was found to be co-localized with neuronal nuclei marker and neurofilaments. The results show sprouting from mature neurons and axons, significantly less demyelination and more myelinated fibers were evident at the lesion site. However, no motor or somatosensory evoked potential response was observed, suggesting lack of long-distance functional connectivity. These findings highlight the therapeutic potential of IONPs along with MF exposure in promoting neuroregeneration after SCI.

Combining Bulk Temperature and Nanoheating Enables Advanced Magnetic Fluid Hyperthermia Efficacy on Pancreatic Tumor Cells

Many efforts are made worldwide to establish magnetic fluid hyperthermia (MFH) as a treatment for organ-confined tumors. However, translation to clinical application hardly succeeds as it still lacks of understanding the mechanisms determining MFH cytotoxic effects. Here, we investigate the intracellular MFH efficacy with respect to different parameters and assess the intracellular cytotoxic effects in detail. For this, MiaPaCa-2 human pancreatic tumor cells and L929 murine fibroblasts were loaded with iron-oxide magnetic nanoparticles (MNP) and exposed to MFH for either 30 min or 90 min. The resulting cytotoxic effects were assessed via clonogenic assay. Our results demonstrate that cell damage depends not only on the obvious parameters bulk temperature and duration of treatment, but most importantly on cell type and thermal energy deposited per cell during MFH treatment. Tumor cell death of 95% was achieved by depositing an intracellular total thermal energy with about 50% margin to damage of healthy cells. This is attributed to combined intracellular nanoheating and extracellular bulk heating. Tumor cell damage of up to 86% was observed for MFH treatment without perceptible bulk temperature rise. Effective heating decreased by up to 65% after MNP were internalized inside cells.

An in-vivo pilot study into the effects of FDG-mNP in cancer in mice

Purpose

Previously, fluorodeoxy glucose conjugated magnetite nanoparticles (FDG-mNPs) injected into cancer cells in conjunction with the application of magnetic hyperthermia have shown promise in new FDG-mNPs applications. The aim of this study was to determine potential toxic or unwanted effects involving both tumour cells and normal tissue in other organs when FDG-mNPs are administered intravenously or intratumourally in mice.

Materials and methods

FDG-mNPs were synthesized. A group of six prostate-tumour bearing mice were injected with 23.42 mg/ml FDG-mNPs (intravenous injection, n = 3; intratumoural injection into the prostate tumour, n = 3). Mice were euthanized and histological sampling of tissue was conducted for the prostate tumour, as well as for lungs, lymph nodes, liver, kidneys, spleen, and brain, at 1 hour (n = 2) and 7 days (n = 4) post-injection. A second group of two normal (non-cancerous) mice received the same injection intravenously into the tail vein and were euthanised at 3 and 6 months post-injection, respectively, to investigate if FDG-mNPs remained in organs at those time points.

Results

In prostate-tumour bearing mice, FDG-mNPs concentrated in the prostate tumour, while relatively small amounts were found in the organs of other tissues, particularly the spleen and the liver; FDG-mNP concentrations decreased over time in all tissues. In normal mice, no detrimental effects were found in either mouse at 3 or 6 months.

Conclusion

Intravenous or intratumoural FDG-mNPs can be safely administered for effective cancer cell destruction. Further research on the clinical utility of FDG-mNPs will be conducted by applying hyperthermia in conjunction with FDG-mNPs in mice.

Combination of fucoidan-based magnetic nanoparticles and immunomodulators enhances tumour-localized immunotherapy

Checkpoint immunotherapy that inhibits tumour immune evasion has demonstrated significant clinical success. However, the therapeutic response is limited to certain patient populations, and immunotoxicity as well as autoimmunity have compromised the therapeutic benefits. Here, we report on an inherently therapeutic fucoidan-dextran-based magnetic nanomedicine (IO@FuDex³) conjugated with a checkpoint inhibitor (anti-PD-L1) and T-cell activators (anti-CD3 and anti-CD28). IO@FuDex³ can repair the immunosuppressive tumour microenvironment by reinvigorating tumour-infiltrating lymphocytes, while targeting the nanomedicine via magnetic navigation to the tumour to minimize off-target effects. Treatment that combines IO@FuDex³ and magnetic navigation reduces the occurrence of adverse events and extends the median survival from 32 to 63 days with less than 1 per cent dose compared with soluble anti-PD-L1. Thus, we demonstrate the potential of integrating anti-PD-L1 and T-cell activators as a form of inherently therapeutic nanomedicine to augment the therapeutic index of combination checkpoint immunotherapy.

A combined low-frequency electromagnetic and fluidic stimulation for a controlled drug release from superparamagnetic calcium phosphate nanoparticles: potential application for cardiovascular diseases

Alternative drug delivery approaches to treat cardiovascular diseases are currently under intense investigation. In this domain, the possibility to target the heart and tailor the amount of drug dose by using a combination of magnetic nanoparticles (NPs) and electromagnetic devices is a fascinating approach. Here, an electromagnetic device based on Helmholtz coils was generated for the application of low-frequency magnetic stimulations to manage drug release from biocompatible superparamagnetic Fe-hydroxyapatite NPs (FeHAs). Integrated with a fluidic circuit mimicking the flow of the cardiovascular environment, the device was efficient to trigger the release of a model drug (ibuprofen) from FeHAs as a function of the applied frequencies. Furthermore, the biological effects on the cardiac system of the identified electromagnetic exposure were assessed in vitro and in vivo by acute stimulation of isolated adult cardiomyocytes and in an animal model. The cardio-compatibility of FeHAs was also assessed in vitro and in an animal model. No alterations of cardiac electrophysiological properties were observed in both cases, providing the evidence that the combination of low-frequency magnetic stimulations and FeHAs might represent a promising strategy for controlled drug delivery to the failing heart.

Recent advances in functional nanostructures as cancer photothermal therapy

Being a non-invasive and relatively safe technique, photothermal therapy has attracted a lot of interest in the cancer treatment field. Recently, nanostructure technology has entered the forefront of cancer therapy owing to its ability to absorb near-infrared radiation as well as efficient light to heat conversion. In this study, key nanostructures for cancer therapy including gold nanoparticles, magnetite iron oxide nanoparticles, organic nanomaterials, and novel two-dimensional nanoagents such as MXenes are discussed. Furthermore, we briefly discuss the characteristics of the nanostructures of these photothermal nanomaterial agents, while focusing on how nanostructures hold potential as cancer therapies. Finally, this review offers promising insight into new cancer therapy approaches, particularly in vivo and in vitro cancer treatments.

Glioma-Targeted Delivery of a Theranostic Liposome Integrated with Quantum Dots, Superparamagnetic Iron Oxide, and Cilengitide for Dual-Imaging Guiding Cancer Surgery

Herein, a theranostic liposome (QSC-Lip) integrated with superparamagnetic iron oxide nanoparticles (SPIONs) and quantum dots (QDs) and cilengitide (CGT) into one platform is constructed to target glioma under magnetic targeting (MT) for guiding surgical resection of glioma. Transmission electron microscopy and X-ray photoelectron spectroscopy confirm the complete coencapsulation of SPIONs and QDs in liposome. Besides, CGT is also effectively encapsulated into the liposome with an encapsulation efficiency of ∼88.9%. QSC-Lip exhibits a diameter of 100 ± 1.24 nm, zeta potential of -17.10 ± 0.11 mV, and good stability in several mediums. Moreover, each cargo shows a biphasic release pattern from QSC-Lip, a rapid initial release within initial 10 h followed by a sustained release. Cellular uptake of QSC-Lip is significantly enhanced by C₆ cells under MT. In vivo dual-imaging studies show that QSC-Lip not only produces an obvious negative-contrast enhancement effect on glioma by magnetic resonance imaging but also makes tumor emitting fluorescence under MT. The dual-imaging of QSC-Lip guides the accurate resection of glioma by surgery. Besides, CGT is also specifically distributed to glioma after administration of QSC-Lip under MT, resulting in an effective inhibition of tumors. The integrated liposome may be a potential carrier for theranostics of tumor.

Macrophage membrane-coated iron oxide nanoparticles for enhanced photothermal tumor therapy

Nanotechnology possesses the potential to revolutionize the diagnosis and treatment of tumors. The ideal nanoparticles used for in vivo cancer therapy should have long blood circulation times and active cancer targeting. Additionally, they should be harmless and invisible to the immune system. Here, we developed a biomimetic nanoplatform with the above properties for cancer therapy. Macrophage membranes were reconstructed into vesicles and then coated onto magnetic iron oxide nanoparticles (Fe₃O₄ NPs). Inherited from the Fe₃O₄ core and the macrophage membrane shell, the resulting Fe₃O₄@MM NPs exhibited good biocompatibility, immune evasion, cancer targeting and light-to-heat conversion capabilities. Due to the favorable in vitro and in vivo properties, biomimetic Fe₃O₄@MM NPs were further used for highly effective photothermal therapy of breast cancer in nude mice. Surface modification of synthetic nanomaterials with biomimetic cell membranes exemplifies a novel strategy for designing an ideal nanoplatform for translational medicine.

Dynamical Magnetic Response of Iron Oxide Nanoparticles Inside Live Cells

Magnetic nanoparticles exposed to alternating magnetic fields have shown a great potential acting as magnetic hyperthermia mediators for cancer treatment. However, a dramatic and unexplained reduction of the nanoparticle magnetic heating efficiency has been evidenced when nanoparticles are located inside cells or tissues. Recent studies suggest the enhancement of nanoparticle clustering and/or immobilization after interaction with cells as possible causes, although a quantitative description of the influence of biological matrices on the magnetic response of magnetic nanoparticles under AC magnetic fields is still lacking. Here, we studied the effect of cell internalization on the dynamical magnetic response of iron oxide nanoparticles (IONPs). AC magnetometry and magnetic susceptibility measurements of two magnetic core sizes (11 and 21 nm) underscored differences in the dynamical magnetic response following cell uptake with effects more pronounced for larger sizes. Two methodologies have been employed for experimentally determining the magnetic heat losses of magnetic nanoparticles inside live cells without risking their viability as well as the suitability of magnetic nanostructures for in vitro hyperthermia studies. Our experimental results-supported by theoretical calculations-reveal that the enhancement of intracellular IONP clustering mainly drives the cell internalization effects rather than intracellular IONP immobilization. Understanding the effects related to the nanoparticle transit into live cells on their magnetic response will allow the design of nanostructures containing magnetic nanoparticles whose dynamical magnetic response will remain invariable in any biological environments, allowing sustained and predictable in vivo heating efficiency.

Superparamagnetic Iron Oxide Nanorod Carriers for Paclitaxel Delivery in the Treatment and Imaging of Colon Cancer in Mice

A multifunctional magnetic drug delivery system was developed and explored as an efficient and less invasive technique to improve colon cancer diagnosis and therapy in mice. In this system, superparamagnetic iron oxide nanorod cores enhanced passive targeting by bandaging a magnet adjacent to the tumor site, whereas pluronic F127 shell acted as the carrier for paclitaxel. The pluronic-conjugated superparamagnetic iron oxide cores were prepared using the hydrothermal method. It was found that the initial pluronic concentration exerted a significant effect on the distribution of the diameters and lengths of the nanorods. Despite the variation in pluronic concentrations and dimensions of iron oxide products, all the samples exhibited negligible coercivity and remanence, confirming their superparamagnetic characteristics. The pluronic F127-superparamagnetic iron oxide nanocarriers were then prepared by encapsulation of nanorods into pluronic micelles and assessed for paclitaxel loading. Results showed that paclitaxel was incorporated into the core of the micelles through hydrophobic interactions, and that elevating both paclitaxel concentration and temperature increased the loading efficiency. The therapeutic effect of paclitaxel-loaded nanocarriers was then tested in in vitro and in vivo colon cancer models. Compared to docetaxel, the paclitaxel-loaded magnetic nanocarriers significantly suppressed tumor growth and improved survival time of xenograft mice. The accumulated magnetic nanocarriers inside the tumor also served as a contrast agent and enhanced magnetic resonance imaging localization and visualization of the small tumor.

Asymmetric Assembling of Iron Oxide Nanocubes for Improving Magnetic Hyperthermia Performance

Magnetic hyperthermia (MH) based on magnetic nanoparticles (MNPs) is a promising adjuvant therapy for cancer treatment. Particle clustering leading to complex magnetic interactions affects the heat generated by MNPs during MH. The heat efficiencies, theoretically predicted, are still poorly understood because of a lack of control of the fabrication of such clusters with defined geometries and thus their functionality. This study aims to correlate the heating efficiency under MH of individually coated iron oxide nanocubes (IONCs) versus soft colloidal nanoclusters made of small groupings of nanocubes arranged in different geometries. The controlled clustering of alkyl-stabilized IONCs is achieved here during the water transfer procedure by tuning the fraction of the amphiphilic copolymer, poly(styrene-co-maleic anhydride) cumene-terminated, to the nanoparticle surface. It is found that increasing the polymer-to-nanoparticle surface ratio leads to the formation of increasingly large nanoclusters with defined geometries. When compared to the individual nanocubes, we show here that controlled grouping of nanoparticles-so-called "dimers" and "trimers" composed of two and three nanocubes, respectively-increases specific absorption rate (SAR) values, while conversely, forming centrosymmetric clusters having more than four nanocubes leads to lower SAR values. Magnetization measurements and Monte Carlo-based simulations support the observed SAR trend and reveal the importance of the dipolar interaction effect and its dependence on the details of the particle arrangements within the different clusters.

Controllable synthesis of a novel magnetic core-shell nanoparticle for dual-modal imaging and pH-responsive drug delivery

In this study, novel magnetic core-shell nanoparticles Fe₃O₄@La-BTC/GO have been synthesized by the layer-by-layer self-assembly (LBL) method and further modified by attachment of amino-modified PEG chains. The nanoparticles were thoroughly characterized by x-ray diffraction, FTIR, scanning electron microscopy and transmission electron microscopy. The core-shell structure was shown to be controlled by the LBL method. The drug loading of doxorubicin (DOX) within the Fe₃O₄@La-BTC/GO-PEG nanoparticles with different numbers of deposited layers was investigated. It was found that DOX loading increased with increasing number of metal organic framework coating layers, indicating that the drug loading can be controlled through the controllable LBL method. Cytotoxicity assays indicated that the Fe₃O₄@La-BTC/GO-PEG nanoparticles were biocompatible. The DOX was released rapidly at pH 3.8 and pH 5.8, but at pH 7.4 the rate and extent of release was greatly attenuated. The nanoparticles therefore demonstrate an excellent pH-triggered drug release. In addition, the particles could be tracked by magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI). A clear dose-dependent contrast enhancement in T ₂-weighted MR images and fluorescence images indicate the potential of these nanoparticles as dual-mode MRI/FOI contrast agents.

Multifunctional Theranostic Nanoparticles Based on Exceedingly Small Magnetic Iron Oxide Nanoparticles for T1-Weighted Magnetic Resonance Imaging and Chemotherapy

The recently emerged exceedingly small magnetic iron oxide nanoparticles (ES-MIONs) (<5 nm) are promising T₁-weighted contrast agents for magnetic resonance imaging (MRI) due to their good biocompatibility compared with Gd-chelates. However, the best particle size of ES-MIONs for T₁ imaging is still unknown because the synthesis of ES-MIONs with precise size control to clarify the relationship between the r₁ (or r₂/r₁) and the particle size remains a challenge. In this study, we synthesized ES-MIONs with seven different sizes below 5 nm and found that 3.6 nm is the best particle size for ES-MIONs to be utilized as T₁-weighted MR contrast agent. To enhance tumor targetability of theranostic nanoparticles and reduce the nonspecific uptake of nanoparticles by normal healthy cells, we constructed a drug delivery system based on the 3.6 nm ES-MIONs for T₁-weighted tumor imaging and chemotherapy. The laser scanning confocal microscopy (LSCM) and flow cytometry analysis results demonstrate that our strategy of precise targeting via exposure or hiding of the targeting ligand RGD₂ on demand is feasible. The MR imaging and chemotherapy results on the cancer cells and tumor-bearing mice reinforce that our DOX@ES-MION3@RGD₂@mPEG3 nanoparticles are promising for high-resolution T₁-weighted MR imaging and precise chemotherapy of tumors.

Magnetic Nanotransducers in Biomedicine

Owing to their abilities to identify diseased conditions, to modulate biological processes, and to control cellular activities, magnetic nanoparticles have become one of the most popular nanomaterials in the biomedical field. Targeted drug delivery, controlled drug release, hyperthermia treatment, imaging, and stimulation of several biological entities are just some of the several tasks that can be accomplished by taking advantage of magnetic nanoparticles in tandem with magnetic fields. The huge interest towards this class of nanomaterials arises from the possibility to physically drive their spatiotemporal localization inside the body, and to deliver an externally applied stimulation at a target site. They in fact behave as actual nanotransducers, converting energy stemming from the external magnetic field into heat and mechanical forces, which act as signals for therapeutic processes such as hyperthermia and controlled drug release. Magnetic nanoparticles are a noninvasive tool that enables the remote activation of biological processes, besides behaving as formidable tracers for different imaging modalities, thus allowing to simultaneously carry out diagnosis and therapy. In view of all this, owing to their multifunctional and multitasking nature, magnetic nanoparticles are already one of the most important nanotechnological protagonists in medicine and biology, enabling an actual theranostic approach in many pathological conditions. In this Concept, we first provide a brief introduction on some physical properties of magnetic materials and on important features that determine the physical properties of magnetic nanoparticles. Thereafter, we will consider some major biomedical applications: hyperthermia, drug delivery/release, and nanoparticle-mediated control of biological processes, even at subcellular level.

Shape Tailored Magnetic Nanorings for Intracellular Hyperthermia Cancer Therapy

ABSTARCT

This work explores a new class of vortex/magnetite/iron oxide nanoparticles designed for magnetic hyperthermia applications. These nanoparticles, named Vortex Iron oxide Particles (VIPs), are an alternative to the traditional Superparamagnetic Iron Oxide Nanoparticles (SPIONs), since VIPs present superior heating power while fulfilling the main requirements for biomedical applications (low cytotoxicity and nonremanent state). In addition, the present work demonstrates that the synthesized VIPs also promote an internalization and aggregation of the particles inside the cell, resulting in a highly localized hyperthermia in the presence of an alternating magnetic field. Thereby, we demonstrate a new and efficient magnetic hyperthermia strategy in which a small, but well localized, concentration of VIPs can promote an intracellular hyperthermia process.

Folate-receptor-targeted NIR-sensitive polydopamine nanoparticles for chemo-photothermal cancer therapy

We propose the use of folate-receptor-targeted, near-infrared-sensitive polydopamine nanoparticles (NPs) for chemo-photothermal cancer therapy as an enhanced type of drug-delivery system which can be synthesized by in situ polymerization and conjugation with folic acid. The NPs consist of a Fe₃O₄/Au core, coated polydopamine, conjugated folic acid, and loaded anti-cancer drug (doxorubicin). The proposed multifunctional NPs show many advantages for therapeutic applications such as good biocompatibility and easy bioconjugation. The polydopamine coating of the NPs show a higher photothermal effect and thus more effective cancer killing compared to Fe₃O₄/Au nanoparticles at the same intensity as near-infrared laser irradiation. In addition, the conjugation of folic acid was shown to enhance cancer cellular uptake efficiency via the folate receptor and thus improve chemotherapeutic efficiency. Through in vitro cancer cell treatment testing, the proposed multifunctional NPs showed advanced photothermal and chemotherapeutic performance. Based on these enhanced anti-cancer properties, we expect that the proposed multifunctional NPs can be used as a drug-delivery system in cancer therapy.