Synthesis of chitosan-coated near-infrared layered double hydroxide nanoparticles for in vivo optical imaging

We incorporated a near-infrared (NIR) fluorescent dye, indocyanine green (ICG), in amine-modified layered double hydroxide nanoparticles (LDHs) by electrostatic attractions to render LDHs-ICG as an efficient NIR contrast agent for in vivo optical imaging. The further coating of chitosan on the external surfaces of LDHs-ICG was achieved through the cross-linking of amine-modified LDHs and different amounts of chitosan by using glutaraldehyde (GA) as a cross-linked agent. The hybridization of this organic-inorganic nanocomposite produced an efficient NIR optical contrast agent because the adsorbed ICG molecules were stabilized in the layered structures of LDHs to prevent them from leaching and/or metabolizing in physiological conditions. The cell viability and hemolysis assay also showed low cytotoxicity and low release of hemoglobin from the cell lysis of red blood cells (RBCs). The in vivo biodistribution results demonstrated that the coating of LDHs with different amounts of chitosan can develop organ-specific drug delivery systems, which can efficiently regulate the nanoparticle accumulation in various organs with un-coated LDHs-ICG targeting the liver and spleen, mono-chitosan-coated LDHs-ICG targeting the lungs, double chitosan-coated LDHs-ICG targeting the lungs and liver, and trimethylammonium (TA) modified double chitosan-coated LDHs-ICG samples targeting the liver. In addition to the high potential for the employment of chitosan-coated LDHs-ICG samples for developing contrast agents for in vivo imaging, the LDH nanoparticles can deliver therapeutic drugs to desired target organs by controlling the coating amounts of chitosan. Therefore, this approach can improve efficiency for traditional cancer diagnosis and cancer chemotherapy.