Multifunctional Fe₃O₄@polydopamine core-shell nanocomposites for intracellular mRNA detection and imaging-guided photothermal therapy

Abstract

Multifunctional nanocomposites have the potential to integrate sensing, diagnostic, and therapeutic functions into a single nanostructure. Herein, we synthesize Fe3O4@polydopamine core-shell nanocomposites (Fe3O4@PDA NCs) through an in situ self-polymerization method. Dopamine, a melanin-like mimic of mussel adhesive proteins, can self-polymerize to form surface-adherent polydopamine (PDA) films onto a wide range of materials including Fe3O4 nanoparticles used here. In such nanocomposites, PDA provides a number of advantages, such as near-infrared absorption, high fluorescence quenching efficiency, and a surface for further functionalization with biomolecules. We demonstrate the ability of the Fe3O4@PDA NCs to act as theranostic agents for intracellular mRNA detection and multimodal imaging-guided photothermal therapy. This work would stimulate interest in the use of PDA as a useful material to construct multifunctional nanocomposites for biomedical applications.

Figure 1

(a) Schematic illustration of the preparation of Fe₃O₄@PDA NCs. (b) RNA detection with the Fe₃O₄@PDA-based nanoprobe. (c) Application of Fe₃O₄@PDA NCs for intracellular mRNA detection and multimodal imaging-guided photo-thermal therapy.

Figure 2

(a) TEM image of the Fe₃O₄@PDA NCs obtained by self-polymerization of DA on the surface of Fe₃O₄ NPs. (b) UV–vis absorption spectra of Fe₃O₄ NPs (0.1 mg mL⁻¹) before and after PDA coating. The inset photo shows the color change between Fe₃O₄ NPs and Fe₃O₄@PDA NCs. (c) Fluorescence quenching of 50 nM FAM-hpDNA in the presence of Fe₃O₄@PDA NCs with a series of concentrations (0, 0.01, 0.02, 0.03, 0.04 mg mL⁻¹). (d) Fluorescence emission spectra of Fe₃O₄@PDA-DNA nanoprobe treated with 200 nM complementary target and 200 nM noncomplementary control sequence. Excitation: 480 nm, emission: 520 nm.

Figure 3

(a) Intracellular testing of the Fe₃O₄@PDA-based nanoprobe. CLSM images of MCF-7 and MCF-10A cells treated with the nanoprobe. Left panels are FAM fluorescence associated with c-myc mRNA, center panels are bright field image of cells, and right panels are the overlay of FAM fluorescence and the bright field image. (b) Simultaneous detection of multiple mRNAs in living cells. CLSM images of MCF-7 and MCF-10A cells treated with multiplexed nanoprobes. Left panels are FAM fluorescence associated with c-myc mRNA, center panels are Cy3 fluorescence associated with TK1 mRNA, and right panels are the overlay of FAM fluorescence and Cy3 fluorescence. Scale bars are 50 μm.

Figure 4

(a) T₂-weighted MR images of the Fe₃O₄@PDA NCs in aqueous solution at different Fe concentrations. (b) Corresponding T₂ relaxation rate of the Fe₃O₄@PDA NCs as a function of Fe concentration. (c) T₂-weighted MR images of MCF-7 cells (5 × 10⁵) incubated with the Fe₃O₄@PDA NCs at different Fe concentrations. (d) PA images and (e) corresponding PA intensity of the Fe₃O₄@PDA NCs with different concentrations. (f) PA images of MCF-7 cells (5 10⁵) incubated with different concentrations of Fe₃O₄@PDA NCs.

Figure 5

(a) Temperature elevation of different concentrations of Fe₃O₄@PDA NCs as a function of irradiation time. (b) CLSM images of differently treated MCF-7 cells stained with PI: (b₁) 5 min of laser irradiation only; (b₂) Fe₃O₄@PDA NCs only; (b₃) Fe₃O₄@PDA NCs and 2 min of laser irradiation; and (b₄) Fe₃O₄@PDA NCs and 5 min of laser irradiation. Left panels are PI fluorescence corresponding to dead cells, and right panels are the overlay of PI fluorescence and the bright field image. Scale bars are 50 μm. (c) Cell viability of MCF-7 cells exposed to different concentrations of Fe₃O₄@PDA NCs with or without laser irradiation.