Preparation Of Temperature And PH Dual-responsive Intelligent Nanofibers And Research On Drug Sustained Release Properties

Multi-stimuli responsive intelligent nanofibers have broad application prospects because of their reversible abrupt changes in properties under specific conditions.For the temperature and pH dual-responsive intelligent nanofibers,it is a difficult problem to consider the intelligent response performance of temperature and pH at present.In order to solve this problem,the bagasse bleached pulp fiber is used in raw material to prepare cellulose nanofibers by two-step oxidation method in this paper.Active carboxyl groups were anchored on the surface of cellulose nanofibers,and polymer with temperature and pH dual-response was introduced to design and prepare a temperature and pH dual-response intelligent nanofibers.In-situ characterization technique was used to study the interaction mechanism of the dual responsive polymer molecular chain under the dual stimulation of temperature and pH.The biocompatibility,drug loading and sustained-release properties of smart nanofibers as drug carriers were analyzed,which provided theoretical guidance and experimental support for the structural design,in-situ characterization and application of multiple intelligent nanofibers.1.Carboxylated nanofibers（CNF-COOH）with high carboxyl density(0.98 mmol·g^-1)were prepared by two-step oxidation of bagasse bleached pulp fibers with sodium periodate and TEMPO,providing active sites for the introduction of dual responsive polymers.Based on the nano size effect of carboxylated nanofibers,a uniform suspension was formed in aqueous phase.Under the premise of maintaining the nano scale of the fiber,the temperature and pH dual-response smart nanofibers（CNF-PEI-NIPAM）was prepared by grafting high density temperature and pH dual-response polymer on the surface of nanofibers by using this‘similar homogeneous’reaction system.CNF-PEI-NIPAM has excellent temperature and pH response properties.It is hydrophilic under acid and low temperature conditions（water contact angle is 49.1°and 87.2°,respectively）,and hydrophobic under alkaline and high temperature conditions（water contact angle is 135.5°and 139.5°,respectively）.The material has balanced the dual response properties of temperature and pH,the contact Angle of water in the hydrophobic state are all higher than 135°,and has stable reversible transformation performance.Based on the in-situ variable temperature characterization technology of solid materials,the interaction mechanism of CNF-PEI-NIPAM dual responsive polymer molecular chain under the dual stimulation of temperature and pH was revealed,which provided experimental support for in-situ characterization of nanofiber based functional materials.2.From the perspective of biocompatibility and evaluation of smart nanofibers as drug carriers,the application possibility of smart nanofibers in food safety and biomedical fields was explored.Based on the evaluation and analysis of acute systemic toxicity,in vitro cytotoxicity,skin irritation and skin sensitization,CNF-PEI-NIPAM showed excellent biocompatibility.At the same time,CNF-PEI-NIPAM has good antibacterial property against Escherichia coli because of the high amino density(4.77 mmol·g^-1),and the antibacterial rate was more than 99%.Using CNF-PEI-NIPAM as drug carrier,the drug loading and release properties of CNF-PEI-NIPAM for three kinds of drugs（doxorubicin DOX,sodium salicylate NaSA and moxifloxacin MOXF）were investigated.The experimental results demonstated that the intelligent nanofibers showed sustained-release behavior for DOX and MOXF,and sudden release behavior for NaSA,which indicated that intelligent nanofibers had broad application in drug transportation and drug sustained release.