Magnetically Responsive Nanoparticles Research Articles

New Vision for Visual Prostheses.

Developments of new strategies to restore vision and improving on current strategies by harnessing new advancements in material and electrical sciences, and biological and genetic-based technologies are of upmost health priorities around the world. Federal and private entities are spending billions of dollars on visual prosthetics technologies. This review describes the most current and state-of-the-art bioengineering technologies to restore vision. This includes a thorough description of traditional electrode-based visual prosthetics that have improved substantially since early prototypes. Recent advances in molecular and synthetic biology have transformed vision-assisted technologies; For example, optogenetic technologies that introduce light-responsive proteins offer excellent resolution but cortical applications are restricted by fiber implantation and tissue damage. Other stimulation modalities, such as magnetic fields, have been explored to achieve non-invasive neuromodulation. Miniature magnetic coils are currently being developed to activate select groups of neurons. Magnetically-responsive nanoparticles or exogenous proteins can significantly enhance the coupling between external electromagnetic devices and any neurons affiliated with these modifications. The need to minimize cytotoxic effects for nanoparticle-based therapies will likely restrict the number of usable materials. Nevertheless, advances in identifying and utilizing proteins that respond to magnetic fields may lead to non-invasive, cell-specific stimulation and may overcome many of the limitations that currently exist with other methods. Finally, sensory substitution systems also serve as viable visual prostheses by converting visual input to auditory and somatosensory stimuli. This review also discusses major challenges in the field and offers bioengineering strategies to overcome those.

Iron oxide nanoparticles for magnetically-guided and magnetically-responsive drug delivery.

In this review, we discuss the recent advances in and problems with the use of magnetically-guided and magnetically-responsive nanoparticles in drug delivery and magnetofection. In magnetically-guided nanoparticles, a constant external magnetic field is used to transport magnetic nanoparticles loaded with drugs to a specific site within the body or to increase the transfection capacity. Magnetofection is the delivery of nucleic acids under the influence of a magnetic field acting on nucleic acid vectors that are associated with magnetic nanoparticles. In magnetically-responsive nanoparticles, magnetic nanoparticles are encapsulated or embedded in a larger colloidal structure that carries a drug. In this last case, an alternating magnetic field can modify the structure of the colloid, thereby providing spatial and temporal control over drug release.

Magnetically actuated alginate scaffold: a novel platform for promoting tissue organization and vascularization.

Among the greatest hurdles hindering the successful implementation of tissue-engineered cardiac patch as a therapeutic strategy for myocardial repair is the know-how to promote its rapid integration into the host. We previously demonstrated that prevascularization of the engineered cardiac patch improves cardiac repair after myocardial infarction (MI); the mature vessel networks were generated by including affinity-bound angiogenic factors in the patch and its transplantation on the blood vessel-enriched omentum. Here, we describe a novel in vitro strategy to promote the formation of capillary-like networks in cell constructs without supplementing with angiogenic factors. Endothelial cells (ECs) were seeded into macroporous alginate scaffolds impregnated with magnetically responsive nanoparticles (MNPs), and after pre-culture for 24 h under standard conditions the constructs were subjected to an alternating magnetic field of 40 Hz for 7 days. The magnetic stimulation per se promoted EC organization into capillary-like structures with no supplementation of angiogenic factors; in the non-stimulated constructs, the cells formed sheets or aggregates. This chapter describes in detail the preparation method of the MNP-impregnated alginate scaffold, the cultivation setup for the cell construct under magnetic field conditions, and the set of analyses performed to characterize the resultant cell constructs.

Cardiac tissue engineering in magnetically actuated scaffolds

Cardiac tissue engineering offers new possibilities for the functional and structural restoration of damaged or lost heart tissue by applying cardiac patches created in vitro. Engineering such functional cardiac patches is a complex mission, involving material design on the nano- and microscale as well as the application of biological cues and stimulation patterns to promote cell survival and organization into a functional cardiac tissue. Herein, we present a novel strategy for creating a functional cardiac patch by combining the use of a macroporous alginate scaffold impregnated with magnetically responsive nanoparticles (MNPs) and the application of external magnetic stimulation. Neonatal rat cardiac cells seeded within the magnetically responsive scaffolds and stimulated by an alternating magnetic field of 5 Hz developed into matured myocardial tissue characterized by anisotropically organized striated cardiac fibers, which preserved its features for longer times than non-stimulated constructs. A greater activation of AKT phosphorylation in cardiac cell constructs after applying a short-term (20 min) external magnetic field indicated the efficacy of magnetic stimulation to actuate at a distance and provided a possible mechanism for its action. Our results point to a synergistic effect of magnetic field stimulation together with nanoparticulate features of the scaffold surface as providing the regenerating environment for cardiac cells driving their organization into functionally mature tissue.

122 Drug-loaded Magnetically-responsive Nanoparticles: Validation of Anti-tumor Activity

122 Drug-loaded Magnetically-responsive Nanoparticles: Validation of Anti-tumor Activity

Formulation and In Vitro Characterization of Composite Biodegradable Magnetic Nanoparticles for Magnetically Guided Cell Delivery

Cells modified with magnetically responsive nanoparticles (MNP) can provide the basis for novel targeted therapeutic strategies. However, improvements are required in the MNP design and cell treatment protocols to provide adequate magnetic properties in balance with acceptable cell viability and function. This study focused on select variables controlling the uptake and cell compatibility of biodegradable polymer-based MNP in cultured endothelial cells. Fluorescent-labeled MNP were formed using magnetite and polylactide as structural components. Their magnetically driven sedimentation and uptake were studied fluorimetrically relative to cell viability in comparison to non-magnetic control conditions. The utility of surface-activated MNP forming affinity complexes with replication-deficient adenovirus (Ad) for transduction achieved concomitantly with magnetic cell loading was examined using the green fluorescent protein reporter. A high-gradient magnetic field was essential for sedimentation and cell binding of albumin-stabilized MNP, the latter being rate-limiting in the MNP loading process. Cell loading up to 160 pg iron oxide per cell was achievable with cell viability >90%. Magnetically driven uptake of MNP-Ad complexes can provide high levels of transgene expression potentially useful for a combined cell/gene therapy. Magnetically responsive endothelial cells for targeted delivery applications can be obtained rapidly and efficiently using composite biodegradable MNP.

Endothelial delivery of antioxidant enzymes loaded into non-polymeric magnetic nanoparticles

Antioxidant enzymes have shown promise as a therapy for pathological conditions involving increased production of reactive oxygen species (ROS). However the efficiency of their use for combating oxidative stress is dependent on the ability to achieve therapeutically adequate levels of active enzymes at the site of ROS-mediated injury. Thus, the implementation of antioxidant enzyme therapy requires a strategy enabling both guided delivery to the target site and effective protection of the protein in its active form. To address these requirements we developed magnetically responsive nanoparticles (MNP) formed by precipitation of calcium oleate in the presence of magnetite-based ferrofluid (controlled aggregation/precipitation) as a carrier for magnetically guided delivery of therapeutic proteins. We hypothesized that antioxidant enzymes, catalase and superoxide dismutase (SOD), can be protected from proteolytic inactivation by encapsulation in MNP. We also hypothesized that catalase-loaded MNP applied with a high-gradient magnetic field can rescue endothelial cells from hydrogen peroxide toxicity in culture. To test these hypotheses, a family of enzyme-loaded MNP formulations were prepared and characterized with respect to their magnetic properties, enzyme entrapment yields and protection capacity. SOD- and catalase-loaded MNP were formed with average sizes ranging from 300 to 400 nm, and a protein loading efficiency of 20–33%. MNP were strongly magnetically responsive (magnetic moment at saturation of 14.3 emu/g) in the absence of magnetic remanence, and exhibited a protracted release of their cargo protein in plasma. Catalase stably associated with MNP was protected from proteolysis and retained 20% of its initial enzymatic activity after 24 h of exposure to pronase. Under magnetic guidance catalase-loaded MNP were rapidly taken up by cultured endothelial cells providing increased resistance to oxidative stress (62 ± 12% cells rescued from hydrogen peroxide induced cell death vs. 10 ± 4% under non-magnetic conditions). We conclude that non-polymeric MNP formed using the controlled aggregation/precipitation strategy are a promising carrier for targeted antioxidant enzyme therapy, and in combination with magnetic guidance can be applied to protect endothelial cells from oxidative stress mediated damage. This protective effect of magnetically targeted MNP impregnated with antioxidant enzymes can be highly relevant for the treatment of cardiovascular disease and should be further investigated in animal models.

Magnetically Responsive Biodegradable Nanoparticles Enhance Adenoviral Gene Transfer in Cultured Smooth Muscle and Endothelial Cells

Replication-defective adenoviral (Ad) vectors have shown promise as a tool for gene delivery-based therapeutic applications. Their clinical use is however limited by therapeutically suboptimal transduction levels in cell types expressing low levels of Coxsackie-Ad receptor (CAR), the primary receptor responsible for the cell entry of the virus, and by systemic adverse reactions. Targeted delivery achievable with Ad complexed with biodegradable magnetically responsive nanoparticles (MNP) may therefore be instrumental for improving both the safety and efficiency of these vectors. Our hypothesis was that magnetically driven delivery of Ad affinity-bound to biodegradable MNP can substantially increase transgene expression in CAR deficient vascular cells in culture. Fluorescently labeled MNP were formulated from polylactide with inclusion of iron oxide and surface-modified with the D1 domain of CAR as an affinity linker. MNP cellular uptake and GFP reporter transgene expression were assayed fluorimetrically in cultured endothelial and smooth muscle cells using lambda(ex)/lambda(em) of 540 nm/575 nm and 485 nm/535 nm, respectively. Stable vector-specific association of Ad with MNP resulted in formation of MNP-Ad complexes displaying rapid cell binding kinetics following a brief exposure to a high gradient magnetic field with resultant gene transfer levels significantly increased compared to free vector or nonmagnetic control treatment. Multiple regression analysis suggested a mechanism of MNP-Ad mediated transduction distinct from that of free Ad, and confirmed the major contribution of the complexes to the gene transfer under magnetic conditions. The magnetically enhanced transduction was achieved without compromising the cell viability or growth kinetics. The enhancement of adenoviral gene delivery by affinity complexation with biodegradable MNP represents a promising approach with a potential to extend the applicability of the viral gene therapeutic strategies.

Magnetic vectoring of magnetically responsive nanoparticles within the murine peritoneum

Magnetically responsive nanoparticles (MNPs) might be candidates for pro-drug formulations for intraperitoneal (i.p.) treatment of ovarian cancer. We conducted feasibility experiments in an i.p. human ovarian carcinoma xenograft model to determine whether MNPs can be effectively vectored within this environment. Our initial results based on magnetic resonance imaging (MRI) indicate that i.p.-injected ∼15 nm magnetite-based MNPs can in fact migrate toward NdFeB magnets externally juxtaposed to the peritoneal cavity above the xenografts growing in the anterior abdominal wall. MNP localization to the tumor/peri-tumoral environment occurs. Further development of this MNP pro-drug strategy is underway.

161 POSTER Magnetic localization of magnetically-responsive nanoparticles to human ovarian carcinoma peritoneal xenografts

161 POSTER Magnetic localization of magnetically-responsive nanoparticles to human ovarian carcinoma peritoneal xenografts

918. Nanoparticle Mediated Gene Delivery to Magnetized Implants

Top of pageAbstract Gene therapy has shown promise; however few methods are available for site-specific gene vector delivery. To address this problem, we employed magnetized implants to localize magnetically responsive nanoparticles (MNP) carrying a surface immobilized recombinant adenovirus (AdV) receptor protein domain, D1. The MNP were formed by a modified emulsification-solvent evaporation technique. Covalent attachment of anionic thiol- and photoreactive polyallylamine derivate to the MNP surface was achieved by exposure of the MNP suspension to UV light. The MNP surface was attached to the D1 through formation of disulfide bonds. MNP capture was investigated in vitro using 304 grade Stainless Steel (SS) compression springs electroplated with a thin layer of NiCo alloy. In static conditions, the springs captured a higher percentage of the MNP in an applied 700G magnetic field as compared to the no-field controls (25% vs. 2%). Gene transduction was studied by incubating MNP for 1 hr with GFP encoding adenovirus to form MNP-AdV composites. Rat aortic smooth muscle cells (A10) and bovine aortic endothelial cells (BAEC) in culture exposed to the MNP-AdV composites for 60 seconds in the 700G applied magnetic field showed higher gene transduction in comparison to the no-field controls. Additionally, MNP localization was examined in male Sprague-Dawley rats, using 316L grade SS compression springs (1.0mm outer diameter) as the MNP delivery platform in a model of stent-angioplasty. Using the external carotid artery approach, the springs were implanted into the common carotid arteries. Several MNP loading strategies are currently under investigation, including pre-loading the MNP onto the spring, local arterial injection, and intravenous injection of the MNP. After delivery, the harvested arterial sections were cut longitudinally, the springs were removed, and the arterial tissue and springs were evaluated by fluorescent microscopy. Results demonstrated that an applied 150G magnetic field leads to greater MNP localization in vivo. The images below depict the endothelial surface (en face) of the common carotid artery after excision from the rat and removal of the spring. The magnetized springs were pre-loaded with BODIPY 564/570 labeled MNP prior to implantation. The MNP pattern on the tissue (a) indicates that the applied 150G field assists MNP uptake after blood flow is re-established in comparison to the no-field control shown in (b). MNP retention on the spring after 10 minutes of blood circulation was also higher (3.7 fold increase) than the no-field control. It is concluded that AdV delivery using MNP and magnetized implants can potentially achieve higher levels of localized transgene expression than observed with free AdV.