Application Of PH/Temperature Dual Responsive Gold Nanoparticle In Protein Activity Regulation

Proteins,as vital components of biological materials,are the main mediators of almost all bioactivity and one of the most important biological macromolecules in life activities.Therefore,it is valuable for protein research in many fields such as tissue engineering,drug delivery,and cell imaging.The composition and structure of the protein determine its unique biological activity.The researchers try to improve the functionality of proteins by different modifications.A lot of studies have shown that the conjugation of biologically active proteins with polymers,especially the responsive polymers which can well respond to environmental stimuli,can reversibly regulate protein functionality and maintain their stability.However,since the long chain of the polymer hinder the substrate from the active site of the protein,the conjugation of the polymer to the protein causes a decrease in the protein activity.Meanwhile,the method of site-directed conjugation of modified proteins can not protect proteins from trypsin decomposition,thus limiting the biological application of modified proteins.Moreover,the structure of the protein is easily destroyed by the external environment factors,resulting in the loss of its function.So the premise of protein modification is to maintain its activity and stability.Gold Nanoparticles(AuNPs)have been proven to be ideal carriers for proteins due to their excellent biocompatibility,controllable particle size,large specific surface area and good stability.In summary,the preparation of a system using gold nanoparticles as a carrier to load stimuli-responsive polymers and proteins to achieve switching-regulation of protein activity has broad prospects in biological applications.First,we conjugate the pyrophosphatase(PPase),pNIPAM and pMAA onto the surface of gold nanoparticles by Au-S bond to prepare AuNP-PPase-pNIPAM-pMAA composite particles.By adjusting the molecular weight of pNIPAM and pMAA,the activity state of the protein under different temperature and pH combinations was systematically investigated.The recycle ability of the complex in complex environment was investigated,and the resistance to trypsin hrydrolysis of the composite particles was explored.Studies have shown that this pH/temperature dual-responsive AuNPs complex not only achieves switching-mode precision regulation of protein activity,but also has high tolerance to trypsin relative to native proteins.This strategy of introducing temperature-sensitive polymers and pH-responsive polymers into protein-nanoparticle complex systems and regulating the protein activity in switching mode under different temperature and pH conditions has enormous potential for applications in controlled biocatalysis and water treatment.Secondly,in order to better control the distribution of responsive polymer molecules on the surface of the material,we further prepared copolymer modified gold nanoparticles of NIPAM and MAA,and studied the composite particles formed with Lysozyme at different temperature and pH conditions.The Lysozyme activity and the effect of the ratio of the monomers on the Lysozyme activity were studied.In addition,the bactericidal ability of the composite particles was explored.The results showed that the copolymer grafted gold nanoparticles can simultaneously respond to pH and temperature and regulate the Lysozyme activity.Moreover,antibacterial tests suggested that the composite particles could realize intelligent and controllable bactericidal effect under the condition of changing temperature and pH.This nanomaterial has potential applications in the fields of antibacterial sterilization and environmental protection.In summary,the surface of the gold nanoparticles can be used to introduce temperature-responsive homopolymers and pH-responsive homopolymers,or the corresponding copolymers,to achieve precise regulation of protein activity in complex conditions where both temperature and pH are changed.The regulation of protein activity can be achieved on different proteins modified composite particles.Both the recycling of composite particles and the anti-trypsin ability make it have great application potential in drug-loading,water treatment,biocatalysis.