Multi-functional core-shell hybrid nanogels for pH-dependent magnetic manipulation, fluorescent pH-sensing, and drug delivery

Remotely optical sensing and drug delivery using an environmentally-guided magnetically-driven hybrid nanogel particle could allow for medical diagnostics and treatment. Such multifunctional hybrid nanogels (<200 nm) were prepared through the first synthesis of magnetic Ni NPs, followed by a moderate growth of fluorescent metallic Ag on the surface of Ni NPs, and then a coverage of a pH-responsive copolymer gel shell of poly(ethylene glycol-co-methacrylic acid) [p(EG-MAA)] onto the Ni-Ag bimetallic NP cores (18 +/- 5 nm). The introduction of the pH-responsive p(EG-MAA) gel shell onto the magnetic and fluorescent Ni-Ag NPs makes the polymer-bound Ni-Ag NPs responsive to pH over the physiologically important range 5.0-7.4. The hybrid nanogels can adapt to surrounding pH and regulate the sensitivity in response to external magnetic field (such as a small magnet of 0.1 T), resulting in the accumulation of the hybrid nanogels within the duration from hours to a few seconds as the pH value decreases from 7.4 to 5.0. The pH-dependent magnetic response characteristic of the hybrid nanogels were further integrated with the pH change to fluorescent signal transduction and pH-regulated anticancer drug (a model drug 5-fluorouracil) delivery functions. The hybrid nanogels can overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells. The multiple responsive hybrid nanogel that can be manipulated in tandem endogenous and exogenous activation should enhance our ability to address the complexity of biological systems. (C) 2011 Elsevier Ltd. All rights reserved.