1 Superparamagnetic iron oxide (SPIO) NPs are also extensively studied as the nano drug carriers of nerve growth factor (NGF) because of their strong magnetic properties that can be used to enhance the neurite growth and direct the neurite orientation mediated by external magnetic fields (MFs). In particular, gold (Au) nanoparticles have been used as a mediator to induce light-based neuro-stimulation through photothermal effect from localized surface plasmon resonance (LSPR). For cells treated with LED (1.90 mW/cm 2) and NGF-SPIO-Au NPs, a dramatic enhancement of neuronal differentiation (83%) and neurite outgrowth (51%) was found, and the upregulation of both the neural differentiation specific marker (β3-tubulin) and the cell adhesive molecule (integrin β1) was observed by the reverse transcription-polymerase chain reaction and western blot analysis.Įngineered nanoparticles (NPs) mediated by external stimuli have attracted accumulative attentions in nanomedicine for non-invasive or less invasive therapeutics. The strong heat generated through their plasmonic surface upon LED irradiation on NGF-SPIO-Au NPs was observed. A remarkable Ca 2+ influx was detected in differentiated PC-12 cells treated with NPs, irradiated by LED of 1.90 and 1.44 mW/cm 2 with great cell viability (>84%) and proliferations. NGF-SPIO-Au NPs of 20 μg/ml, were tested on PC-12 neuron-like cells, irradiated by LEDs (525 nm, 1.09, 1.44, and 1.90 mW/cm 2). Copyright (2000) American Chemical Society.This paper reports nerve growth factor functionalized superparamagnetic iron oxide–gold core-shell nanoparticles (NGF-SPIO-Au NPs), an engineered nanomedicine for non-invasive neuron regeneration when irradiated by a low-intensity light-emitting diode (LED). Reprinted with permission from Thomas and Kamat (Ref. This is indicated by an arrow with a cross mark. Due to the attachment of nitrogen onto the nanoparticles, conjugation between lone pair on nitrogen and the pyrene ring is blocked. 8.8: Gold nanoparticles-assisted enhancement of fluorescence in pyrene methyl amine. This results in enhanced fluorescence.įig. Gold suppresses the electron transfer between the nitrogen and the pyrene ring as shown by the arrows in Fig. Copyright (2003) American Chemical Society. Reprinted with permission from Ipe, et al. 8.7: Reversible binding of amino acids with spiropyran capped gold nanoparticles. 8.6: Various functionalized nanoparticles, with their chemical functionalities.įig. This was entirely different from the normal trend wherein heavy metals quench the fluorescence.
The fluorescence of pyrene was found to increase when attached to the metal surface. Such systems can be possible candidates for light-mediated binding and release of amino acid derivatives.Īnother interesting property was observed in pyrene methyl amine-capped gold nanoparticles. This open ring merocyanin can form a complex with amino acids which helps in forming a further layer of amino acid around the gold nanoparticles (Fig. When irradiated with light, spiropyran (SP) changes to the highly polar-colored merocyanin (MC) form. Under dark conditions, a majority of the spiropyran exist in the close ring form.
Photoswitchable gold nanoparticles with a double shell structure in which the inner shell is made of spiropyran, have been used to control the binding and release of the outer shell of amino acids.
These include derivatives of porphyrenes (Ref. Functionalization can be either through a ligand exchange reaction or using modified thiol as the capping agent in the Brust method.Various photoactive molecules have been attached to the surface of gold using the thiol end group and such structures are shown in Fig. The synthesis of functionalized nanomaterials has been receiving considerable attention during the past few years.