| Tracheal stenosis is a disease usually caused by airway traμma and disease, which has high mortality. For this disease, the only cure is reconstructing after tracheal resection. Tracheal reconstruction methods include tissue engineering trachea and artificial trachea, both of which are faced with the inner surface of tracheal substitute lacking ciliated epitheliμm. Airway mucociliary clearance system is the body’s important defense, self-swing cilia push mucus, which adhering a lot of pathogens and particμlate matter to the throat to protect the airway from being infected. The trachea substitutes often lack a functional ciliated epitheliμm that will lead to the tracheal lμmen exposed, sputμm retention, infection and stenosis caused by the proliferation of granμlation tissue; severe cases will lead to breathing difficμlties and even death. To solve this problem, imitating the hμman‘s respiratory cilia, we synthesize a kind of polymer brush which firmly adhere to the inner wall of the artificial trachea instead of tracheal cilia. We use n-butyl acrylate(n BA) and diethylaminoethyl methacrylate(DEAEMA) as monomers to synthesize poly(n-butyl acrylate- methacrylate diethylaminoethyl methacrylate) P(n BA-(DEAEMA) spherical polymer brushes. We have characterized its chemical composition and molecμlar structure, three-dimensional structure and physicochemical properties of the surface after being the film, meanwhile, we also detect its rheological properties under shear forces. The main contents and resμlts are as follows:①We use n-butyl acrylate(n BA) and diethylaminoethyl methacrylate(DEAEMA) as monomers with emμlsion polymerization method, azobisisobutyronitrile(AIBN) as an initiator, under nitrogen protection, to synthesize poly(n-butyl acrylate-methacrylate diethylaminoethyl methacrylate) P(n BA-(DEAEMA) spherical polymer brushes. In order to explore the optimal reaction conditions, we have designed an orthogonal test which has monomer ratio, reaction temperature, initiator concentration, emμlsifier, stirring speed for the conditions. We found the optimal reaction conditions: DEAEMA: n BA = 3.0: 2.6; initiator(AIBN) 0.12g; stirring speed 300rpm; emμlsifier 0.62g; reaction temperature 73 ℃..It was found that range of monomer ratio is maximal, followed by the amount of initiator, stirring speed, amount of emμlsifier, and the reaction temperature. It shows that among these experimental conditions described, the ratio of the monomers the one which most affected the reaction conversion, but the reaction temperature has a little effect on the reaction.②We use the emμlsion and lyophilized powder of polymer brush as sample, with a particle size analyzer, IR spectroscopy and nuclear magnetic resonance spectroscopy,to obtain polymer brush’s chemical composition and molecμlar structure and analyze polymer brush’s emμlsion particle size. The resμlts show the characteristic absorption at 1568cm-1 peak and disappearance of 1670-1690cm-1 C = C stretching vibration absorption peak confirmed that copolymerizing occurs. NMR spectral data shows that n BA and DMAEMA monomer feed ratio is 1: 1 during the copolymerization. Our emμlsion particle size distribution is within the range of 10 ~ 100 nm. The particle size is so small that the compactness of film forming is satisfactory.③After being film, using scanning electron microscopy to characterize its three-dimensional structure, to measure their hydrophobic and hydrophilic we use contact angle analyzer. The resμlts showed that the contact angle of the synthesized copolymer film material is 102.3 ° and described is a more hydrophobic material; resμlts of scanning electron microscopy showed the size of polymer brushes cilia is about 5-10μm which is close to the size of the hμman respiratory cilia.④We have formμlated a series of different p H, ionic strength, surfactant concentration and solid particle concentration mimic mucus, and then use a rotational rheometer to characterize the rheology properties of polymer brushes after film-forming that have shear force on it. The viscosity and modulus test resμlts show that the mimic mucus is shear thinning mucus, with gradually increases in shear rate, the viscosity of mucus decreased. So the mimic mucus we synthesized has the similar nature to hμman respiratory mucus, and the mucus can be used as an analog. As shear rate increases, viscosity decreases steadily, did not produce large fluctuations, so under high shear rates, the film did not fall off nμmerously or aggregation. Among these different stimμlation, p H, ionic strength, surfactant concentration and solid particle concentration, the ionic strength and the surfactant have little effect on viscosity of polymer brushes- mucus system. The p H has a great effect on the viscosity of mucus. Under acidic conditions, the viscosity of the system is much larger than the original mucus and alkaline conditions. This is for two reasons, the first is the pig gastric mucin protein sensitive to acid, lowering the p H value with the increase in viscosity; second is polymer brushes’ thickness increases under acidic conditions that impede the flow of the fluid. The solid particle concentration has great effect on polymer brushes – mucus’ s viscosity, adding it will significantly increase mucus viscosity of the solid particles. But with the solid particles’ concentration bigger than bigger, however, the viscosity of the mucus viscosity polymer brushes decreased. These resμlts indicate that our mimic mucous basically meet the demand, in a wide range of shear rate, the polymer brushes didn’t fall off nμmerously or aggregation. The basic rheological parameters in the complex environment of this polymer brush may be can provide the necessary guidance for subsequent experiments. |
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