In Vivo Pulmonary Delivery and Magnetic-Targeting of Dry Powder

Oct 25, 2017 - Dominique N. Price†, Loreen R. Stromberg†‡, Nitesh K. Kunda† , and Pavan Muttil†§. † Department of Pharmaceutical Sciences...
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Brief Article

In vivo pulmonary delivery and magnetictargeting of dry powder nano-in-microparticles Dominique N. Price, Loreen R. Stromberg, Nitesh K Kunda, and Pavan Muttil Mol. Pharmaceutics, Just Accepted Manuscript • DOI: 10.1021/acs.molpharmaceut.7b00532 • Publication Date (Web): 25 Oct 2017 Downloaded from http://pubs.acs.org on October 30, 2017

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Molecular Pharmaceutics

In vivo pulmonary delivery and magnetictargeting of dry powder nano-inmicroparticles

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Dominique N. Price1, Loreen R. Stromberg1,2, Nitesh K. Kunda1, and Pavan Muttil1,3*

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Health Sciences Center, Albuquerque, New Mexico

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Department of Mechanical Engineering, Iowa State University, Ames, Iowa

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The University of New Mexico Cancer Center, Albuquerque, New Mexico

Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico

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Conflicts of Interest: The authors have no conflicts of interest to declare.

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Abstract

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This brief communication evaluates the cytotoxicity and targeting capability of a dry powder

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chemotherapeutic. Nano-in-microparticles (NIMs) are a dry powder drug delivery vehicle

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containing superparamagnetic iron oxide nanoparticles (SPIONs) and either doxorubicin (w/w

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solids) or fluorescent nanospheres (w/v during formulation; as a drug surrogate) in a lactose

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matrix. In vitro cytotoxicity was evaluated in A549 adenocarcinoma cells using MTS and LDH

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assays to assess viability and toxicity after 48 hours of NIMs exposure. In vivo magnetic-field-

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dependent targeting of inhaled NIMs was evaluated in a healthy mouse model. Mice were

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endotracheally administered fluorescently-labeled NIMs either as a dry powder or a liquid

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aerosol in the presence of an external magnet placed over the left lung. Quantification of

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fluorescence and iron showed a significant increase in both fluorescence intensity and iron

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content to the left magnetized lung. In comparison, we observed decreased targeting of

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fluorescent nanospheres to the left lung from an aerosolized liquid suspension, due to the

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dissociation of SPIONs and nanoparticles during pulmonary administration. We conclude that

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dry powder NIMs maintain the therapeutic cytotoxicity of doxorubicin and can be better

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targeted to specific regions of the lung, in the presence of a magnetic field, compared to a liquid

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suspension.

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Keywords: Targeted pulmonary delivery; nano-in-microparticles (NIMs); pulmonary

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chemotherapeutic; aerosolized drug delivery; non-small cell lung cancer; superparamagnetic

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iron oxide nanoparticles (SPIONs)

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Introduction

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Lung cancer is the second most commonly diagnosed cancer in both men and women, and it has

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the highest mortality rate compared to all other types of cancer accounting for 26.5% of all

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cancer deaths1–3. Conventional chemotherapy for lung cancer is administered intravenously and

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does not distinguish between cancerous and healthy cells. The high concentrations of

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chemotherapeutic agents that are required for systemic administration often lead to nonspecific

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adverse effects, while lung tumor microenvironments that are distantly located from capillaries

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receive sub-therapeutic drug concentrations.

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Pulmonary drug delivery has been used to treat respiratory diseases such as asthma and

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microbial infections, as well as systemic diseases4–9. The lungs are well-suited for drug delivery

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due to their large surface area, thin alveolar epithelium, easily permeable membrane, and

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extensive vasculature, which allow substantial and rapid drug absorption for increased local and

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systemic efficacy9. Pulmonary delivery of chemotherapy has been evaluated in human trials for

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the treatment of lung cancer10–15. A phase I/II study of inhaled doxorubicin combined with

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systemic platinum-based therapy was administered to twenty-eight patients with advanced non-

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small cell lung cancer11. However, while the results of this localized delivery were promising, a

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few patients experienced dose-limiting pulmonary-toxicity. In a preclinical study, Dames and

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colleagues attempted to minimize toxicity to the whole lung by targeting a therapeutic surrogate

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to a specific lung lobe in mice using iron oxide nanoparticles in the presence of an external

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magnetic field16. However, targeting to the magnetized lobe was minimal due to the separation

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of the drug surrogate and iron oxide nanoparticles during pulmonary administration of the liquid ACS Paragon Plus Environment

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suspension.

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The aim of this study was two-fold, 1) to determine if dry powder nano-in-microparticles

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(NIMs)17 containing doxorubicin still display therapeutic cytotoxicity after the spray drying

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process and 2) to evaluate the magnetic-field-dependent targeting of dry powder NIMs

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administered endotracheally into the lungs of healthy mice (Fig. 1A). Our hypothesis was that

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the incorporation of a chemotherapeutic agent and iron-oxide nanoparticles in a powder matrix

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should prevent the separation of nanoparticles and therapeutic observed by Dames et al., while

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still targeting the drug payload to the magnetized lung region (Fig. 1A)16. This inhalable drug-

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delivery approach has the potential to reduce toxicity to healthy tissues by targeting drugs

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directly to specific regions of the lung, thus achieving therapeutic concentration near solid

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tumors (Fig. 1B)18,19.

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Experimental Methods

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Materials

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Alpha-D-(+)-lactose monohydrate Respitose ML-001 was a gift from DMV-Fonterra

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Excipients GmbH & Co. KG (Goch, Germany). FluidMAG-UC SPIONs with a hydrodynamic

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diameter of 50 nm was purchased from Chemicell GmbH (Berlin, Germany). Fluorescent dye-

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containing NIMs were formulated with Molecular Probes® FluoSpheres® Carboxylate-

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Modified Nanospheres (F8783, 0.02µm, λex = 660nm and λem = 680nm, Molecular Probes®,

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Life Technologies, Thermo Fisher Scientific, Inc. Waltham, MA, USA).

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Formulation and characterization of the NIMs delivery vehicle

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Spray drying of the NIMs delivery vehicle was performed as described previously17.

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Briefly, a suspension containing approximately 20% (w/w) SPIONs and either 2.8% (w/w)

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doxorubicin (Selleck Chemicals, LLC, Houston, TX, USA) (w/w) (for in vitro studies) or 10%

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(w/w) fluorescent nanospheres (fluorescent drug surrogate for in vivo studies) was spray-dried

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in MilliQ water and a lactose matrix (2.5% w/v total feed concentration) (Fig. 1A). A B-290 ACS Paragon Plus Environment

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mini-spray dryer with a standard two-fluid nozzle (0.7mm diameter) (Büchi Corporation,

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Flawil, Switzerland), was used to spray dry the suspension with the following parameters: inlet

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temperature 170 ± 2°C, outlet temperature 103 ± 2°C, aspirator rate 100%, and an atomization

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air flow rate of 742NL/h. Spray-dried control microparticles were formulated containing a

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higher concentration of 5% lactose only (w/v) in MilliQ water to keep particle sizing similar.

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Figure 1: Magnetic field-dependent lung targeting. A) Pictorial representation of NIMs dry

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powder showing lactose (gray), doxorubicin (red), and SPIONs (black)17. B) Scanning electron

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microscope image of NIMs dry powder. C) Schematic of endotracheal delivery of magnetically-

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targeted NIMs. D) Orientation of the permanent magnet in thoracotomized mice prior to

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pulmonary delivery of NIMs. E) Orientation of the trachea, right lung, and left lung prior to

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imaging. SPIONs are visible in the trachea and left lung (shown by arrows) demonstrating

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magnetic targeting.

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Dry powder NIMs particle sizing

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NIMs geometric particle size was measured using a Mastersizer 3000 analyzer (Malvern

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Instruments Ltd, Worcestershire, UK) attached to a dry-dispersion accessory device (Aero S,

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Malvern Instruments). A pressure of 4 bars was used for the venturi dispenser with a feed rate of

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90%. The refractive index of the sample was taken to be the average of the NIMs components

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multiplied by the percent (w/w) contained in the formulation: 70% w/w lactose (1.35), 20% w/w

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SPIONs (2.42), and 10% w/w fluorescent nanospheres (1.52) for a weighted average of 1.58.

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The results were expressed in terms of Dv50 (volumetric median diameter). All samples were

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analyzed in triplicate and are expressed as mean ± standard deviation. The aerodynamic

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diameter of the NIMs was determined using a Next Generation Impactor (NGI) (model 170,

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MSP Corporation, Shoreview, MN). NIMs were insufflated into the NGI using the DP4 dry

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powder insufflator™ for rat (Penn Century, Inc., USA). The NGI was operated with a flow rate

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of 30L/min for 10min. Particle deposition was determined by the gravimetric method.

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Cell culture

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Human lung adenocarcinoma A549 cells (ATCC® CCL-185™) (American Type Tissue

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Culture, Manassas, Virginia, USA) were grown in Ham’s F12K (Kaighn’s) medium and

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supplemented with fetal bovine serum (FBS), 5% L-glutamine, 3% antimycotic, and 3%

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antibiotic (Life Technologies, Grand Island, NY, USA).

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Cytotoxicity studies

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Confluent cells were exposed to dry powder NIMs containing doxorubicin (D-NIMs)

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and controls (doxorubicin solution, lactose solution, and SPIONs suspension). A549 cell

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viability and toxicity were tested using the CytoTox96® Non-Radioactive (3-(4,5-

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dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium

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cell proliferation assay and the CytoTox96® Non-Radioactive lactate dehydrogenase (LDH)

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cytotoxicity assay, respectively. Briefly, D-NIMs were uniformly dispersed in F12K non-

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supplemented media with FBS at three different doxorubicin concentrations: 0.16µg/mL (low

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concentration), 1.6µg/mL (medium concentration), and 16µg/mL (high concentration) (referred

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to henceforth as low, medium, and high dose). The same media was used to generate free

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doxorubicin solutions with concentrations of 0.3µg/mL (low), 3µg/mL (medium), and 30µg/mL

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(high). Controls consisting of lactose solution and SPIONs suspension were used at

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concentrations similar to those present in NIMs, as ratios from the spray dried feed solution

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were held constant relative to doxorubicin. Prior to exposure, A549 cells were washed with

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fresh media and 100µL of the suspensions/solutions (D-NIMs; doxorubicin only; lactose;

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SPIONs).

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CellTiter 96® Aqueous One Solution Reagent MTS assay (Promega, Madison,

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Wisconsin, USA) and CytoTox96® Non-Radioactive Assay LDH assay (Promega, Madison,

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Wisconsin, USA) were performed according to the manufacturer’s instructions. In brief, at time

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periods of 1, 8, 24, 48 hours post-exposure, 80µL of cell culture supernatant was aspirated from

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each well and centrifuged at 10,000 rpm for 10 minutes to settle any SPIONs or cells. MTS

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reagent was mixed with the cell culture supernatant at a ratio of 1:6 (MTS) or 1:2 (LDH),

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aliquoted into a black optical bottom 96-well plate and incubated at 37°C and 5% CO2 for 3

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hours (MTS) or 30 min (LDH). For LDH development, 50µL of stop solution was added to each

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well. Absorbance was measured at a wavelength of 490nm. Results were plotted as absorbance

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over time with respect to increasing amounts of doxorubicin present in the D-NIMs.

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In vivo study design

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Male Balb/c mice (6-8 weeks old; Jackson Laboratory, Sacramento, CA, USA) were

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used for the in vivo targeting studies. All rodents were housed in a temperature and light cycle

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controlled facility, and their care followed the guidelines of the National Institutes of Health and

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an approved Institutional Animal Care and Use Committee protocol (IACUC protocol number

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11-100747-HSC). Mice were randomly assigned to 5 different groups with n=3 per group: 1)

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Untreated control mice; 2) Mice administered NIMs dry powders magnetically-targeted to the

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left lung; 3) Mice administered NIMs dry powders in the absence of magnetic targeting; 4) Mice

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administered NIMs liquid suspensions magnetically-targeted to the left lung; 5) Mice

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administered NIMs liquid suspensions in the absence of magnetic targeting. For the in vivo

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studies, doxorubicin in the NIMs was replaced with fluorescent nanoparticles as a drug

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surrogate to facilitate imaging.

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Mice were anesthetized with a standard dose of xylazine/ketamine. A dry powder

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Insufflator™ for mouse (DP-4-M; Penn-Century Inc., Wyndmoor, PA, USA) was attached to a

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1mL disposable plastic syringe that was used to endotracheally administer the dry powder

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NIMs. Briefly, anesthetized mice were placed on their back on a intubation platform (Penn-

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Century Inc., Wyndmoor, PA, USA) and the tracheal opening was visualized by inserting a

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small animal laryngoscope (Model LS2; Penn-Century Inc.)20. The insufflator delivery tube was

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inserted gently into the trachea of the animal, proximal to the carina, until the bend of the

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delivery tube was positioned at the incisors. Skin over the left lung of the mouse was carefully

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dissected without exposing the thoracic cavity

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neodymium−iron−boron (NdFeB) permanent cylindrical magnet (grade N52, 22mm long ×

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20mm in diameter; Applied Magnets, Plano, TX) was centered 1mm above the left lung to avoid

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contact with the tissue, with the edge of the magnet perpendicular to the upper region of the left

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lung (Fig. 1C). Skin removal was performed to decrease the distance between the lung and the

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magnet, and maximize the magnetic targeting. The orientation of the magnet over the left lung

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was critical for the NIMs to be sufficiently attracted to the magnetic pole that was created by the

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externally-applied magnetic field. We had previously characterized the permanent magnet to

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have a magnetic field of 0.58 Tesla17.

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and a commercially available

Approximately 2.0mg of NIMs were loaded in the insufflator and administered using the 8 ACS Paragon Plus Environment

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plastic syringe with an air volume of 500µL for a total of 10 puffs (10 actuations). Of the 2.0mg

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loaded in the insufflator, 0.5mg was delivered into the mouse lung based on the gravimetric

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analysis of the insufflator before and after dosing. A NIMs liquid suspension was administered

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using the MicroSprayer® aerosolizer (1A-1C; Penn-Century) for mouse and was attached to a

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hand-operated, high-pressure syringe (FMJ-250; Penn-Century)21. Mice were endotracheally

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intubated and 50µL of saline containing 0.5mg of the NIMs dry powder (w/v solids; containing

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equivalent amounts of the fluorescent dye and SPIONs) was administered directly into the

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airways with the MicroSprayer®. Control mice were treated similarly using the dry powder

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NIMs and liquid suspension in the absence of magnetic-field-dependent targeting. Mice were

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sacrificed immediately after pulmonary delivery; lungs and trachea were removed en bloc,

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separated (Fig. 1D), and fluorescence and iron deposition were quantified in the respective

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tissues.

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Fluorescence quantification

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NIMs dry powder and NIMs suspension were administered endotracheally and targeted

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to the left lung in the presence of a permanent magnet. Individual lung lobes and trachea were

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excised and imaged immediately for fluorescence (λex = 660nm and λem = 680nm) with an

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exposure time of 10 seconds using a Caliper IVIS Lumina II imaging system (Caliper Life

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Sciences). A region of interest (ROI) was drawn around the trachea, left lung, right lung, and

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background. The ROI area was kept constant at 2.5 cm2 and fluorescence was expressed as units

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of average radiance efficiency (RE) (p/sec/cm2/sr)/(µW/cm2)22.

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Equation 1. Fluorescence calculations

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% Targeting =

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Targeting Efficiency L:R Ratio = %

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× 100 %   

Percent targeting was calculated by determining ratios of the fluorescence intensity (FI individual)

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fluorescence intensity (FI

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denominator (Equation 1), and multiplied by 100. Targeting efficiency L:R ratio was calculated

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using the percent targeting of the left lung in the numerator, divided by the percent targeting of

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the right lung in the denominator.

sum)

of the three ROI areas (trachea, left lung, and right lung) in the

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Iron quantification

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Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to

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measure ferrous iron content in the mouse lungs and trachea. Briefly, tissue was digested with

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0.5mL nitric acid (HNO3) at 105 °C for 1 hour and vortexed until completely dissolved

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(protocol modified from Niazi et al.23). After cooling, the samples were brought up to a known

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volume with MilliQ water. Samples were analyzed with a PerkinElmer Optima 4300 DV ICP-

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OES. The recommended wavelength for iron was used, Fe (II)-λ-259.939 nm. A five-point

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calibration standard range was used that ranged from 0.1 ppm to 25 ppm (mg/L). Endogenous

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iron was analyzed from the lungs of untreated mice (n = 3), and the average of these values was

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subtracted from the treated mice. Calibration and instrument verification samples were

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incorporated before and after analyzing the samples, as well as periodically throughout the

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measurements.

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Equation 2. Iron calculations

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% Targeting =

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Targeting Efficiency L:R Ratio = %[]

[] [] 

× 100 %[]   

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Targeting efficiency ratio was calculated by determining ratios of the iron content from

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individual tissue (e.g. left lung) in the numerator, divided by the sum of the total iron content for

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all three tissues (trachea, left lung, and right lung) in the denominator (Equation 2), and

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multiplied by 100. Targeting efficiency L:R ratio was calculated using the percent targeting of

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the left lung in the numerator, divided by the percent targeting of the right lung in the

2

denominator.

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Dye and iron targeting corroboration

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Equation 3. Fluorescence and iron differentials

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Fluorescence differential = 

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Iron differential = [)*+]

!" #$

!" #$

− &'$(" #$

− [)*+]&'$(" #$

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Targeting of dye and iron was corroborated by calculating the differential between the

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fluorescence (relative efficiency) or iron concentrations in left lung compared to the right

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(Equation 3).

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Statistical analysis

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All statistical analysis was performed using GraphPad Prism statistical software

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(GraphPad Software, San Diego, CA). Paired t-tests with Bonferroni correction were used to

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compare two or more groups of independent data. The difference between variants was

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considered significant if p < .05. For comparisons of more than two groups an ordinary one-way

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ANOVA was used to determine significance, with Tukey’s multiple comparisons and a Brown-

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Forsythe test used to compare variances. If more than two variables were taken into account, a

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two-way ANOVA was employed with Sidak’s multiple comparison. A post hoc power

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calculation was performed using the free program G*power (Dusseldorf, Germany)24,25. For in

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vivo animal experiments with equivalent sample sizes and an effect size of n = 3, the power was

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calculated to be > 0.95.

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Results

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Dry powder NIMs formulation and characterization

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Dry powder NIMs for pulmonary administration were prepared as described previously

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using lactose as the bulking agent17,26. NIMs were characterized for aerodynamic and geometric

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diameters, surface charge of the SPIONs, morphology, magnetic behavior, iron content, and

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drug loading (Table 1)17. For this study, doxorubicin, a common chemotherapeutic agent with

3

demonstrated activity against lung cancer, was used. NIMs with doxorubicin will be referred to

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as D-NIMs. Table 1. Characterization of SPIONs and NIMs* SPIONs average radius density zeta potential

NIMs

56 ± 6nm 2.5 g/cm3 -49 mV

Concentration (w/w) 1.6% Doxorubicin 10.6% Fe3O4 Laser Diffraction 1.6µm Next generation Impaction MMAD‡ 3.27µm FPF‡ > 90% GSD‡ ± 1.69

*

For more details on the NIMs powder preparation and characterization consult McBride et al [17] For NIMs dry powder ‡ Mass Median Aerodynamic Diameter (MMAD), Fine Particle Fraction (FPF), Geometric Standard Deviation (GSD) †

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In vitro evaluation of chemotherapeutic efficacy

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To assess whether the doxorubicin in D-NIMs retained its cytotoxicity (and therefore its

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therapeutic effect) after spray drying, a MTS assay was utilized to measure cell viability of lung

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adenocarcinoma cells after D-NIMs exposure. We hypothesized that D-NIMs would quickly

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release the doxorubicin and would have similar or increased cytotoxicity compared to free

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doxorubicin in A549 cells. The left panel of Figure 2 compares A549 cells treated with D-

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NIMs, as well as controls consisting of spray-dried lactose, SPIONs alone, and free doxorubicin

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solution. A549 cells were exposed to low, medium, and high doses of free doxorubicin solution

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or D-NIMs for a total of 48 hours (Fig. 2). It is important to note that the concentration of

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doxorubicin was approximately doubled in the free doxorubicin solution control group

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compared to the D-NIMs dry powder group at all three doses. The low concentration of free

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doxorubicin solution (0.03µg) or D-NIMs (0.016µg) showed minimal cytotoxicity, and cells

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were as viable as untreated A549 cells after 48 hours of exposure (Fig. 2A, MTS panel).

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However, medium and high doses of doxorubicin solution and D-NIMs were toxic to 12 ACS Paragon Plus Environment

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adenocarcinoma cells compared to SPION and lactose controls. Importantly, at both medium

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and high doses, no significant differences were seen between the free doxorubicin and D-NIMs

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groups ((67±1.67)% and (58±0.51)% respectively), despite D-NIMs containing doxorubicin at

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nearly half the concentration of the free doxorubicin group. (Fig 2C, MTS panel).

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Figure 2. MTS viability and LDH cytotoxicity assay of A549 cells exposed to doxorubicin-

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loaded NIMs. MTS (left panel) and LDH (right panel) assay measuring viability and

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cytotoxicity, respectively, of A549 lung adenocarcinoma cells after 48 hours of exposure to A) 13 ACS Paragon Plus Environment

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low dose of D-NIMs compared to free doxorubicin (1µg NIMs containing 0.016µg doxorubicin

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compared to 0.03µg free doxorubicin), B) medium dose of D-NIMs compared to free

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doxorubicin (10µg NIMs containing 0.16µg doxorubicin compared to 0.3µg free doxorubicin),

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and C) high dose of D-NIMs compared to free doxorubicin (100µg NIMs containing 1.6µg

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doxorubicin compared to 3.0µg free doxorubicin). Free doxorubicin control (dark gray), Spray-

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dried lactose control (light gray), SPIONs control (dashed gray), D-NIMs (black); for both MTS

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and LDH panels. Lactose and SPIONs controls were used at the ratios from the spray dried feed

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solution and were held constant relative to doxorubicin. A two-way ANOVA with Sidak’s

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multiple comparison test was used to determine statistical significance. *p