Remote Actuation of Magnetic Nanoparticles For Cancer Cell Selective Treatment Through Cytoskeletal Disruption

Motion of micron and sub-micron size magnetic particles in alternating magnetic fields can activate mechanosensitive cellular functions or physically destruct cancer cells. However, such effects are usually observed with relatively large magnetic particles (>250 nm) that would be difficult if at all possible to deliver to remote sites in the body to treat disease. Here we show a completely new mechanism of selective toxicity of superparamagnetic nanoparticles (SMNP) of 7 to 8 nm in diameter to cancer cells. These particles are coated by block copolymers, which facilitates their entry into the cells and clustering in the lysosomes, where they are then magneto-mechanically actuated by remotely applied alternating current (AC) magnetic fields of very low frequency (50 Hz). Such fields and treatments are safe for surrounding tissues but produce cytoskeletal disruption and subsequent death of cancer cells while leaving healthy cells intact

In Vitro Trafficking and Efficacy of Core-Shell Nanostructures for Treating Intracellular Salmonella Infections

Nanostructures encapsulating gentamicin and having either amphiphilic (N1) or hydrophilic (N2) surfaces were designed. Flow cytometry and confocal microscopy studies demonstrated a higher rate of uptake for amphiphilic surfaces. A majority of N1 were localized in the cytoplasm, whereas N2 colocalized with the endosomes/lysosomes. Colocalization was not observed between nanostructures and intracellular Salmonella bacteria. However, significant in vitro reductions in bacterial counts (0.44 log 10 ) were observed after incubation with N1, suggesting that the surface property of the nanostructure influences intracellular bacterial clearance

Live nephron imaging by MRI

The local sensitivity of MRI can be improved with small MR detectors placed close to regions of interest. However, to maintain such sensitivity advantage, local detectors normally need to communicate with the external amplifier through cable connections, which prevent the use of local detectors as implantable devices. Recently, an integrated wireless amplifier was developed that can efficiently amplify and broadcast locally detected signals, so that the local sensitivity was enhanced without the need for cable connections. This integrated detector enabled the live imaging of individual glomeruli using negative contrast introduced by cationized ferritin, and the live imaging of renal tubules using positive contrast introduced by gadopentetate dimeglumine. Here, we utilized the high blood flow to image individual glomeruli as hyperintense regions without any contrast agent. These hyperintense regions were identified for pixels with signal intensities higher than the local average. Addition of Mn2+ allowed the simultaneous detection of both glomeruli and renal tubules: Mn2+ was primarily reabsorbed by renal tubules, which would be distinguished from glomeruli due to higher enhancement in T1-weighted MRI. Dynamic studies of Mn2+ absorption confirmed the differential absorption affinity of glomeruli and renal tubules, potentially enabling the in vivo observation of nephron function. there has been considerable interest in observing individual nephrons and studying their function (6, 13, 14). Current techniques for nephron counting involve histology or acid maceration, thus are impractical for longitudinal preclinical studies or eventual clinical use. Micropuncture can study glomerular filtration of individual nephrons (7), but this destructive technique is applicable only to nephrons that are very close to the cortical surface. On the other hand, MRI is a nondestructive technique that has proven invaluable for structural and functional nephrology (4, 8, 9, 19–22). Contrast enhancement, based on the delivery of cationized ferritin, has enabled nondestructive observation of individual glomeruli (1, 2, 3, 5, 10). However, these high-resolution studies were mostly performed on ex vivo kidneys. In vivo observation of glomeruli is more challenging (5, 18), because it requires sensitive detection of remote signals emitted from deep inside the body. Whereas smaller MRI detectors placed close to the tissue of interest can improve local sensitivity, the need for cables to transfer the locally detected signals is cumbersome and introduces a risk of infection. Recently, a wireless amplified NMR detector (WAND) (15) was developed to actively amplify emitted signals from small, implantable MR detectors (11, 17). Such enhanced sensitivity enabled the in vivo observation of individual glomeruli using transverse dephasing (T2*) contrast introduced by cationized ferritin, and renal tubules enhanced by gadopentetate dimeglumine (Gd-DTPA) in longitudinal relaxation (T1) weighted images (16). In this work, we extended the contrast available for kidney anatomy and function. Glomeruli were observable in native kidney as hyperintense regions due to the high blood flow inside glomerulus arterioles. After MnCl2 was infused intravenously, the majority of Mn2+ accumulated in renal tubules and enhanced tubular signals to a greater extent, while glomeruli appeared as less enhanced regions compared with their surrounding tissues. Dynamic studies of MnCl2 absorption confirmed the differential affinity of glomeruli and renal tubules to Mn2+, paving way for in vivo studies of nephron function. The WAND technique can be used to noninvasively monitor nephron physiology in vivo and could potentially be used to study structure-function relationships and macromolecular filtration of individual nephrons. The ability to image glomeruli and renal tubules nondestructively may eventually enable the clinical use of the WAND as a chronic monitoring device for transplanted kidneys

Efficacy of Amphiphilic Core-Shell Nanostructures Encapsulating Gentamicin in an In Vitro Salmonella and Listeria Intracellular Infection Model

Core-shell nanostructures with nonionic amphiphilic shells and ionic cores encapsulating gentamicin were designed for therapy against intracellular pathogens, including Salmonella and Listeria . Flow cytometry and confocal microscopy showed that their uptake into J774A.1 macrophages proceeded mainly by fluid-phase endocytosis and clathrin-mediated pathways. The nanostructures were nontoxic in vitro at doses of 50 to 250 μg/ml, and they significantly reduced the amounts of intracellular Salmonella (0.53 log) and Listeria (3.16 log), thereby suggesting effective transport into the cells

Nanomedicine for intracellular therapy

Intracellular pathogens like Salmonella evade host phagocytic killing by various mechanisms. Classical antimicrobial therapy requires multiple dosages and frequent administration of drugs for a long duration. Intracellular delivery of antimicrobials using nanoparticle may effectively devise therapies for bacterial infections. This review will address the mechanisms used by Salmonella to avoid host pathogenic killing, reasons for therapeutic failure and advances in nanoparticle drug delivery technology for efficient intracellular bacterial clearance

Antibacterial efficacy of core-shell nanostructures encapsulating gentamicin against an in vivo intracellular Salmonella model

Pluronic based core-shell nanostructures encapsulating gentamicin were designed in this study. Block copolymers of (PAA −+ Na- b -(PEO- b -PPO- b -PEO)-b-PAA −+ Na) were blended with PAA − Na + and complexed with the polycationic antibiotic gentamicin to form nanostructures. Synthesized nanostructures had a hydrodynamic diameter of 210 nm, zeta potentials of −0.7 (±0.2), and incorporated ∼20% by weight of gentamicin. Nanostructures upon co-incubation with J774A.1 macrophage cells showed no adverse toxicity in vitro . Nanostructures administered in vivo either at multiple dosage of 5 μg g −1 or single dosage of 15 μg g −1 in AJ-646 mice infected with Salmonella resulted in significant reduction of viable bacteria in the liver and spleen. Histopathological evaluation for concentration-dependent toxicity at a dosage of 15 μg g −1 revealed mineralized deposits in 50% kidney tissues of free gentamicin-treated mice which in contrast was absent in nanostructure-treated mice. Thus, encapsulation of gentamicin in nanostructures may reduce toxicity and improve in vivo bacterial clearance

Wireless Amplified NMR detector (WAND) for high resolution in-vivo image of internal organs

Purpose To assess the feasibility of imaging deep-lying internal organs at high spatial resolution by imaging kidney glomeruli in a rodent model with use of a newly developed, wireless amplified nuclear magnetic resonance (MR) detector. Materials and Methods This study was approved by the Animal Care and Use Committee at the National Institutes of Health/National Institute of Neurologic Disorder and Stroke. As a preclinical demonstration of this new detection technology, five different millimeter-scale wireless amplified nuclear MR detectors configured as double frequency resonators were chronically implanted on the medial surface of the kidney in five Sprague-Dawley rats for MR imaging at 11.7 T. Among these rats, two were administered gadopentetate dimeglumine to visualize renal tubules on T1-weighted gradient-refocused echo (GRE) images, two were administered cationized ferritin to visualize glomeruli on T2*-weighted GRE images, and the remaining rat was administered both gadopentetate dimeglumine and cationized ferritin to visualize the interleaved pattern of renal tubules and glomeruli. The image intensity in each pixel was compared with the local tissue signal intensity average to identify regions of hyper- or hypointensity. Results T1-weighted images with 70-μm in-plane resolution and 200-μm section thickness were obtained within 3.2 minutes to image renal tubules, and T2*-weighted images of the same resolution were obtained within 5.8 minutes to image the glomeruli. Hyperintensity from gadopentetate dimeglumine enabled visualization of renal tubules, and hypointensity from cationic ferritin enabled visualization of the glomeruli. Conclusion High-spatial-resolution images have been obtained to observe kidney microstructures in vivo with a wireless amplified nuclear MR detector