This review highlights the state-of-the-art in the application of magnetic nanoparticles (MNPs) and their composites for remote controlled therapies. Novel macro- to nano-scale systems that utilize remote controlled drug release due to actuation of MNPs by static or alternating magnetic fields and magnetic field guidance of MNPs for drug delivery applications are summarized. Recent advances in controlled energy release for thermal therapy and nanoscale energy therapy are addressed as well. Additionally, studies that utilize MNP-based thermal therapy in combination with other treatments such as chemotherapy or radiation to enhance the efficacy of the conventional treatment are discussed.

Targeted pulmonary delivery facilitates the direct application of bioactive materials to the lungs in a controlled manner and provides an exciting platform for targeting magnetic nanoparticles (MNPs) to the lungs. Iron oxide MNPs remotely heat in the presence of an alternating magnetic field (AMF) providing unique opportunities for therapeutic applications such as hyperthermia. In this study, spray drying was used to formulate magnetic nanocomposite microparticles (“MnMs”) consisting of iron oxide MNPs and D-mannitol. The physicochemical properties of these MnMs were evaluated and the in vitro aerosol dispersion performance of the dry powders was measured by the Next Generation Impactor®. For all powders the mass median aerosol diameter (MMAD) was < 5 µm and deposition patterns revealed that MnMs could deposit throughout the lungs. Heating studies with a custom AMF showed that MNPs retain excellent thermal properties after spray drying into composite dry powders, with specific absorption ratios (SAR) >200 W/g, and in vitro studies on a human lung cell line indicated moderate cytotoxicity of these materials. These inhalable composites present a class of materials with many potential applications and pose a promising approach for thermal treatment of the lungs through targeted pulmonary administration of MNPs.

Magnetic hyperthermia as a treatment modality is acquiring increased recognition for loco-regional therapy of primary and metastatic lung malignancies by pulmonary delivery of magnetic nanoparticles (MNP). The unique characteristic of magnetic nanoparticles to induce localized hyperthermia in the presence of an alternating magnetic field (AMF) allows for preferential killing of cells at the tumor site. In this study we demonstrate the effect of hyperthermia induced by low and high dose of MNP under the influence of an AMF using 3D tumor tissue analogs (TTA) representing the micrometastatic, perfusion independent stage of triple negative breast cancer (TNBC) that infiltrates the lungs. While application of inhalable magnetic nanocomposite microparticles (MnMs) to the micrometastatic TNBC model comprised of TTA generated from cancer and stromal cells, showed no measureable adverse effects in the absence of AMF-exposure, magnetic hyperthermia generated under the influence of an AMF in TTA incubated in a high concentration of MNP (1 mg/ mL) caused significant increase in cellular death/ damage with mechanical disintegration and release of cell debris indicating the potential of these inhalable composites as a promising approach for thermal treatment of diseased lungs. The novelty and significance of this study lies in the development of methods to evaluate in vitro the application of inhalable composites containing MNPs in thermal therapy using a physiologically relevant metastatic TNBC model representative of the microenvironmental characteristics in secondary lung malignancies.

Poly(ethylene glycol) (PEG) hydrogels are hydrophilic, high water content, polymeric networks that represent excellent candidates as engineering biomaterials for a broad range of applications. A key challenge for many biomedical applications is the control of transport properties within the resulting 3D crosslinked gels. The effects of the water content at synthesis and crosslinker molecular weights on gel chemical structure and equilibrium volumetric swelling ratio, Q, are studied for a series of PEG hydrogels. In addition, the translational diffusion coefficients of a model probe molecule, Rhodamine 110, are determined directly within the hydrogels by fluorescence correlation spectroscopy measurements. Increasing the water content at synthesis results in larger observed swelling behavior and faster particle transport within the formed PEG hydrogels for two different crosslinker molecular weights due to fewer physical crosslinks in the gels. Comparison of the particle translational diffusion coefficient to the swelling ratio shows a linear relationship for all crosslink densities examined.

Nanoparticles represent one of the most widely studied classes of advanced drug delivery platforms in recent years due to a wide range of unique properties and capabilities that can be utilized to improve upon traditional drug administration. Conversely, hydrogel nanoparticles (HNPs) – also called nanogels – represent a unique class of materials that combine the intrinsic advantages of nanotechnology with the inherent capabilities of hydrogels. Responsive hydrogels pose a particularly interesting class of materials that can sense and respond to external stimuli and previous reports of inhalable hydrogel particles have highlighted their potential in pulmonary delivery. Here, we synthesized two different pH-responsive HNPs, designated HNP120 and HNP270, by incorporating functional monomers with a common crosslinker and characterized their physicochemical properties. One of the HNP systems was selected for incorporation into a composite dry powder by spray drying, and the aerodynamic performance of the resulting powder was evaluated. The HNP120s displayed a hydrodynamic diameter of approximately 120 nm in their fully swollen state and a minimal diameter of around 80 nm while the HNP270s were approximately 270 nm and 115 nm, respectively. Electron microscopy confirmed particle size- and morphological uniformity of the HNPs. The HNP120s were spray dried into composite dry powders for inhalation and cascade impaction studies showed good aerosol performance with a mass median aerosol diameter (MMAD) of 4.82 ± 0.37 and a fine particle fraction > 30%. The HNPs released from the spray dried composites retained their responsive behavior thereby illustrating the potential for these materials as intelligent drug delivery systems that combine the advantages of nanotechnology, lung targeting through pulmonary delivery, and stimuli-responsive hydrogels.