Figure 1: Generation of MagBICE nanoparticles and in vitro binding properties.

(a) Schematic showing the concept of cell matchmaking by MagBICE and the preparation of MagBICE nanoparticles. (b) TEM images of unconjugated FH and MagBICE₁ nanoparticles. Conjugated antibodies (pointed as ‘Abs’) were negatively stained with uranyl acetate and iron oxide cores (indicated as ‘Fe’) in the complex were unstained. (c) Fluorescent micrographs showing clusters of unconjugated FH and MagBICE₁ stained with anti-mouse Texas-Red and anti-rabbit FITC secondary Abs, identifying the anti-MLC and anti-CD45 Abs on MagBICE₁. (d) SDS–PAGE image showing the reduction of Ab amount in the supernatant after the conjugation reaction. (e) A280 protein concentrations in the pre- and post-conjugation solutions (P=0.0002; n=3). (f) Average hydrodynamic sizes of unconjugated FH and MagBICE₁ particles measured by a zeta metre (P=0.0013; n=3). (g) Average zeta potentials of unconjugated FH and MagBICE₁ particles measured by a zeta metre (P=0.1608; n=3). (h) Schematic showing the experiment where rat BMCs were incubated with FH or MagBICE₁ and then further incubated with secondary Abs (anti-rabbit FITC) for detection. Fluorescent microscopic images showing the binding of MagBICE₁, but not FH, to rat BMCs (scale bars, 20 μm). (i) Flow cytometry analysis showing the specific binding of MagBICE₁ to rat BMCs. (j) Prussian blue staining of the iron cores showing the binding of MagBICE₁, but not unconjugated FH, to rat BMCs (scale bars, 20 μm; P=0.0002; n=5). (k) Fluorescent microscopic images showing the binding of MagBICE₁, but not unconjugated FH, to injured cardiomyocytes (NRCMs). The anti-MLC and anti-CD45 Abs on MagBICE₁ were detected by anti-mouse Texas-Red and anti-rabbit FITC secondary Abs, respectively (scale bars, 50 μm). The percentages of FITC-positive NRCMs were quantified (P<0.0001; n=5). (l) Fluorescent microscopic images showing MagBICE₁ conjoined rat BMCs (DiD-labelled; magenta) with injured NRCMs (green; scale bars, 50 μm). The numbers of BMCs attaching to NRCMs were quantified (P<0.0001; n=9). All data are mean±s.d. Comparisons between any two groups were performed using two-tailed unpaired Student’s t-test. *P<0.05. DAPI, 4′,6-diamidino-2-phenylindole.