Antibody-functionalized, stimuli responsive microgel gold-hybrid colloids: synthesis, characterizations and their use in pathogen detection

Abstract

Antibody-functionalized hybrid microgels serve as an innovative approach for various translational applications particularly for detection of pathogens. We have synthesized Poly (N-isoproplyacrylamide)-co-poly(acrylic acid) (PNIPAm-PAA) based microgels encapsulated with gold nanoparticles followed by loading on antibodies specific to diarrheal pathogen, Salmonella typhimurium using the established streptavidin-biotin chemistry. Antibody-loaded hybrid microgel particles are further characterized with respect to their loading efficiencies using UV-Vis spectrometry and pH/temperature-dependent swelling using dynamic light scattering. Our results showed that streptavidin-coated hybrid gold nanoparticles bind to biotinylated antibodies with high affinity. From UV-Vis spectroscopy, it was observed that antibody-conjugated PNIPAM-AuNS showed two peaks; one at a wavelength of 540 nm due to gold nanoparticles and another at a wavelength of 280 nm due to antibodies. The effect of temperature on the hydrodynamic radius (Rh) of PNIPAM microgel particles, PNIPAM-AuNS, streptavidin-coated PNIPAM-AuNS and biotinylated antibodies conjugated with PNIPAM-AuNS was determined by dynamic light scattering which was further confirmed from the temperature dependant swelling of these biotinylated antibodies loaded onto hybrid microgels which exhibit less thermoresponsivity than the control hybrid microgels. Our results establish stimuli-responsive polymer hybrids as important new hybrid biomaterials for the detection of Salmonella typhimurium.