Supplemental figure 1: Histological correlation. (a) Low-power view and (b) high power view (inset) of swine liver post MC transplantation stained with Prussian Blue (PB) for iron. PB-positive MCs are lodged in sinuses. (c) Ex vivo MR image of corresponding slice in (a). (d) 3D reconstruction of MC distribution (green) obtained with in vivo MRI (for full 3D animation see Supplementary movie 2). Blue = gall bladder.

Supplementary Information

Magnetic Resonance-Guided, Real-Time Targeted Delivery and Imaging of

Magnetocapsules Immunoprotecting Pancreatic Islet Cells

Brad P. Barnett1,2, Aravind Arepally1, Parag V. Karmarkar1, Di Qian1, Wesley D. Gilson1,

Piotr Walczak1,2, Valerie Howland1, Leo Lawler1, Cal Lauzon1,2,

Matthias Stuber1, Dara L. Kraitchman1, Jeff W.M. Bulte1,2

1Russell H. Morgan Department of Radiology and Radiological Science and 2Institute for Cell

Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States.

Methods

Permeability of microcapsules

For lectin permeability measurements, capsules were incubated with either 15 � L (1 mg/mL)

of FITC-Triticum vulgare (WGA, MW=36 kDa), FITC-Maackia amurensis I (MAL-I, MW=75

kDa), FITC-Ricinus communis (RCA-I, MW=120 kDa), or FITC-Sambuca nigra (SNA,

MW=150 kDa). All lectins were obtained from EY Lab Inc., except FITC-Maackia amurensis I

(Vector laboratories). Capsules were incubated for 48h at 4°C on a mechanical rocker, after which

they were examined microscopically (Olympus X51 and IX71 epifluorescence microscopes

equipped with an Olympus DP-70 digital acquisition system) following embedding with

Vectashield mounting medium (Vector). Macroscopic images of microcapsules in 6-well plates

were obtained with a D100 6MP Digital SLR Camera (Nikon).

Glucose-Stimulated Insulin Secretion

A static incubation assay was used to assess the insulin secretion response of encapsulated

human islets. A step-wise increase in glucose concentration from 3.3 to 16.7 mM D-glucose in

RPMI 1640 medium (purchased as glucose-free) was used to assess the glucose responsiveness

of encapsulated cells. The glucose responsiveness index was calculated as (1-(3.3mM (c-

peptide)/16.7mM (c-peptide)). Following 24 hr of culture post encapsulation, islets were pre-

incubated at 37°C for 45 min in glucose and serum-free RPMI-1640 with 0.5% BSA and 3.3

mmol/L glucose added. Fifty encapsulated islets were placed in a culture insert (membrane pore

diameter 12 � m; Millicell PFC) in six well plates. 5 mL of fresh serum-free RPMI-1640 with 0.5%

BSA and 3.3 mmol/L glucose was added to each well. After an additional 45-min incubation

period at 37°C, the media was removed and replaced with RPMI-1640 with 0.5% BSA and 16.7

mmol/L glucose, again with 5 mL of media added per well. Encapsulated islets were incubated for

an additional 45 min in this high-glucose medium. Aliquots of the medium at low (3.3 mmol/L)

and high (16.7 mmol/L) glucose concentrations were stored at -80°C. The C-peptide content of the

samples was determined with an enzyme-linked immunosorbent assay (ultrasensitive human c-

peptide ELISA, Alpco Diagnostics); results (in ng/ml) were expressed as the mean of three

independent experiments.

MRI of phantoms

Phantom imaging was performed on a 3T Philips Achieva MR scanner with a 6-element

cardiac phased-array receiver coil. For three-dimensional T2-*weighted gradient echo imaging,

which provides hypointense contrast, the imaging parameters were: repetition time (TR)=7.0 ms;

echo time (TE)=2.3 ms; flip angle (FA)=15°; field of view (FOV)=22 cm; matrix=512x512; and

slice thickness (ST)=1 mm. For fast spin echo 3D IRON imaging, which provides bright contrast,

the imaging parameters were the same except for TR=1300 ms; TE=12.0 ms; IRON pulse

bandwidth (BWIRON)=170Hz; and turbo factor=18.

MRI of mice

MRI was performed at 9.4 T (Bruker horizontal scanner) using a custom-built animal

holder and a whole-body volume transmitting/receiving coil. T2-weighted spin echo (SE) and T2*-

weighted gradient echo sequences (GRE) were used. The SE parameters were TR=1500 ms,

TE=15 ms, FOV=3x3 cm, matrix=196x196, ST=0.8 mm, and number of signal averages=4. GRE

parameters were the same, except for TR=500 ms, TE=6 ms, matrix=296x296, and FA=30°.

MRI of swine

Animals were sedated with 1 ml/50 lbs of telazol/ketamine/xylazine (100/10/100 mg/ml

IM) and induced with sodium thiopental (25 mg/ml IV to effect). Induction was followed by

endotracheal intubation and mechanical ventilation with oxygen and 1-2% isoflurane anesthesia. In

vivo imaging was performed on a 1.5 T MR scanner (CV/i, GE Medical Systems) using a 4

channel phased-array coil and a real-time, steady-state free precession sequence (TR=3.4 ms,

TE=1.2 ms, FA=45º, receiver BW=125 kHz, ST=10 mm, FOV=30x30 cm, and matrix=128x128).

In combination with an interactive scan plane acquisition (i-Drive, GE Medical Systems), the

needle was advanced into the IVC. Prior to and following the puncture procedure, a contrast-

enhanced MR angiogram (MRA) of the mesenteric venous system was obtained by IV injection of

30 ml of 0.1 mmol/kg gadopentate dimeglumine (Magnevist, Berlex Laboratories Inc.) at 2 ml/sec.

The imaging parameters were: TR=4.8 ms, TE=1.4 ms, flip angle=25º, BW=31.2 kHz,

FOV=30x30 cm2, and matrix=256x256.

MRI of explanted liver

MRI was performed at 3T on a Philips Achieva MR scanner using a 6-element cardiac phased-

array coil and a three-dimensional GRE sequence. The imaging parameters were: TR=12.8 ms,

TE=6.3 ms, FA=15°, FOV=28 cm, matrix=512x512, and slice thickness=1 mm. MR data

processing was performed using Amira 3.1 software (Mercury Computer Systems). For

visualization of MC liver distribution, a signal intensity threshold was applied to dissect the range

of signal intensities that corresponded to MCs. For the obtained data, surface rendering of MC-

related pixels was performed, color-coded (green), and superimposed with surface rendering of the

complete data set (red).

Results

Table 1: Permeability (√) and nonpermeability (X) of non-labeled capsules and MCs for lectins with

various molecular weights. Following incorporation of Feridex♦, the permeability is unaltered with free

diffusion of lectins ≤75 kDa, but not for lectins ≥120 kDa.

Capsules – Feridex Capsules + Feridex

36 kDa √ √

75 kDa √ √

120 kDa X X

150 kDa X X