Due to its excellent mechanical property, dye ability and skin affinity, PA6 has been widely used in apparel, home textiles, military products, etc. However, PA6 fiber is easy to breed bacteria and corroded by bacteria in humid environment. One of development tendency of functional PA6 fiber is to design and develop nylon 6 fiber with excellent antibacterial properties, which is also the research target of this paper. In the present investigation, ZnO antibacterial agent was prepared through sol-gel method, and antibacterial masterbatch was acquired via blending antibacterial agent with PA6 using a twin-screw, then antibacterial PA6 fiber was obtained through melt spinning. The thermal properties, crystallization property of antibacterial PA6 masterbatch were discussed. The effect of drawing ratio on fiber strength, elongation of break, orientation and crystallization was also investigated. The antibacterial properties of antibacterial agent and antibacterial PA6 fiber was analyzed by agar diffusion method. The results of Differential Scanning Calorimetry (DSC) suggests that the antibacterial agent causes the rise of crystallization temperature and crystallization rate. X-Ray Diffraction (XRD) and mechanical testing results reveal that the higher drawing ratio leads to higher orientation and strength of PA6 fiber, lower elongation at break. The addition of antibacterial agent increases the degree of orientation and crystallization, reduces the strength of fiber and tends to form α crystalline in PA6 fiber. Antibacterial tests show that antibacterial PA6 fiber has a good antibacterial performance against Staphylococcus aureus.
Detailed studies were performed to probe the effects of the cross-linking layer microstructure of pH-responsive shell cross-linked (SCL) micelles on the loading capacity of doxorubicin (DOX). Well-defined poly [(ethylene glycol)-block-2-(dimethylamino) ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEG-b-P(DMA- co-QDMA)-b-PDEA) copolymer with “clickable” moieties in the middle block by the quaternization with propargyl bromide dissolved molecularly in acidic solution; micellization occurred at alkaline solution to form three-layer “onionlike” micelles constituting PDEA cores, P(DMA-co-QDMA) inner shells, and PEG coronas. Two types of cross-linker bearing azide group: 1,6-bisazidehexane and bis-(azidoethyl) disulfide were utilized to prepare the SCL micelles with different cross-linking layer microstructure via click chemistry at basic aqueous media. The results showed that two types of SCL micelles possessed excellent stability. In neutral solution, these SCL micelles still maintained structural integrity, and the average hydrodynamic diameter of SCL micelles 1 and SCL micelles 2 increased to 80 nm and 90 nm, respectively. In the acidic solution, due to the complete protonated of the PDEA core, the sizes of the two types of SCL micelles increased to 95 nm and 110 nm, respectively, which were favorable for the diffusion of the encapsulated drug in the core. Moreover, the cross-linking degree had no effect on the size of SCL micelles. The loading efficiency and loading content of the SCL micelles were significantly better than those of the uncross-linked micelles, and loading capacity did not vary with degree of cross-linking. However, the SCL micelles 1 demonstrated better loading capacity. This study could be a guidance for the future research on the effects of the cross-linking layer microstructure on controlled doxorubicin release.
Two kinds of diblock copolymers containing glucose and phenylboronic acid moieties, respectively, poly (ethylene glycol)-b-poly (gluconamidoethyl methacrylate) (PEG-b-PGAMA) and poly (ethylene glycol)-b-poly (2-aminoethyl methacrylate-co-3-nitrophenyboronic acid methacrylate) (PEG-b-P(AMA-co-NPBMA)) were synthesized via atom transfer radical polymerization (ATRP) and post polymerization modification (PPM). Well-defined structure and narrow molecular weight distribution of the polymers were confirmed by proton Nuclear Magnetic Resonance (1H NMR) and Gel Permeation Chromatography (GPC). Based on the cross-linking between the diol groups of the glycopolymer and phenylboronic acid under physiological pH (7.4), complex micelles composed of PEG outer shell and boronate ester cross-linking core with a hydrodynamic diameter around 20nm were formed. Morphology, size and assembly behavior of the complex micelles were investigated by 1H NMR, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The results showed the formation/cleavage of boronate ester linkage is reversible upon the variation of solution pH, the complex micelles displayed pH sentiveties of assembling/disassembling behavior. Above pH 7.4, stable spherical micelles can be formed, whereas pH less than 5.5, the micelles dissociated into unimers. Therefore, such pH-responsive micelles based on dynamic complexation of phenyl boronate bonds are expected to be applied to pH-responsive nanodrug carriers
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