Abstract
In this paper, we report an easy route for preparing new metal nanorod-polymer composites consisting of gold nanorods, Au NRs, and temperature responsive copolymer “microgel” particles. The microgel particles of ~200 nm in size, which contain carboxylic acid groups, were prepared by surfactant-free emulsion polymerization of a selected mixture made of N-isopropylacylamide and acrylic acid in the presence of a cross-linker N,N′-methylenebisacrylamide. The electrostatic interactions between the cationic cetyltrimethylammonium bromide (CTAB) stabilized Au NRs and anionic microgel particles were expected to occur in order to prepare stable Au NRs-microgel composite particles. The optical and structural characterization of the composite was achieved using UV-Vis spectroscopy, Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) and dynamic light scattering (DLS). TEM image shows that Au NRs are attached on the surface of the microgel particles. Dynamic light scattering measurements prove that the composite particles are temperature responsive, which means the particles undergo a decrease in size as the temperature increases above its phase transition temperature. In vitro cytotoxicity of the composite materials were tested by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Lactate dehydrogenase (LDH), and hemolysis assay, which showed non-toxicity (biocompatibility).
Highlights
Stimuli-responsive polymers or so-called “smart polymers” have the capacity of altering their chemical or physical properties upon exposure to an external environment
We report the results obtained by studying the properties of the temperature responsive Au NRs-microgel composite particles prepared by electrostatic interactions between the two opposite-charged particles where the NRs are connected to the microgel particles
The typical proton signals around 1.0 ppm ascribed to the –CH3 with a hydrodynamic diameter of ca. 200 nm1 were synthesized by surfactant-free emulsion protons of the NIPAM units were observed in the H NMR spectra of the copolymers, and the signal polymerization
Summary
Stimuli-responsive polymers or so-called “smart polymers” have the capacity of altering their chemical or physical properties upon exposure to an external environment. Over the last two decades, these stimuli-responsive polymers have been studied broadly for their promising applications as biosensors [1,2] for their drug delivery [2,3,4,5] and for their use as regenerative medicine [6,7] Among these stimuli-responsive polymers, poly(N-isopropylacrylamide) (PNIPAM) and its copolymers or microgels/nanogels (three dimensionally crosslink colloidal particles) have been an area of interest due to the fact that this material has the capacity to alter or respond to external stimuli [8]. Our research group has reported [35] earlier on the development of thermo and pH-responsive microgel-based Au NRs and their structural characterization with atomic force microscopy and the volume phase transition behavior upon near-IR laser irradiation. All these properties make these prepared composite materials more beneficial for further biological applications like photothermal-therapy and drug delivery application
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