添食法制备改性蚕丝的研究进展

Research Progress on Preparation of Modified Silk by Feeding Method

蚕丝是优异的天然蛋白质纤维,被广泛地应用在纺织、服装、生物医学等领域。蚕丝的形成需经历一个复杂的过程:家蚕首先在后部丝腺合成丝素蛋白,丝素蛋白液经过中部丝腺,与其合成分泌的丝胶液一起,通过腺腔内的压力进入到前部丝腺、吐丝管,再通过榨丝区的肌肉活动对丝蛋白受到的剪切力进行调节,使其二级结构改变,最后在家蚕头部的牵伸摆动下,迅速固化,形成蚕丝。蚕丝虽然具有优异的性能,但仍存在抗菌性能及抗紫外性能差等缺陷,这在一定程度上限制了蚕丝的应用及蚕丝产业的进一步发展。通过对蚕丝进行改性并赋予其新的功能可拓展蚕丝的应用领域,促进蚕丝产业的发展。添食法具有简单、高效、环保及有利于规模化生产等优点,可在源头改性蚕丝的性能,是大量制备改性蚕丝的最有效方法。添食物质的选择至关重要。首先,添食物质不能有毒性;添食后,不能影响家蚕正常的生理及生命活动。其次,要注意添食物质颗粒的尺寸。此外,选择的添食物质需要有突出的性能。综合以上因素,纳米颗粒成为添食家蚕的首选物质。研究者们选择不同种类的纳米颗粒进行添食,取得了一定的成果。在保证蚕丝质地柔软光滑本质的同时,能大幅提升蚕丝的力学性能,且改善蚕丝的热稳定性能。目前,通过添食纳米颗粒制备的蚕丝的力学性能最高可提高111.25%。荧光蚕丝在生物医药工程、光学和光电子领域都具有巨大的应用价值。近年来,有多种方法已应用于制备荧光蚕丝,但大都不够环保且难以大规模持续生产。研究人员通过给五龄时期的家蚕添食具有荧光效应的染料或稀土荧光粉的方法可获得彩色荧光蚕丝。通过此方法所得的荧光蚕丝不仅具有良好的荧光性能,而且具有优异的荧光稳定性。但添食荧光材料会对家蚕的生理和生命活动造成一定影响,并使蚕丝的力学性能有所降低。为了制备具有不同功能的蚕丝,研究人员拓展了添食物质的种类,利用含氮物质、超细羽绒粉体、色素等进行添食,得到了质量突出的蚕茧及力学性能优异的改性蚕丝。本文以添食物质、添食后制备的改性蚕丝的结构及性能为重点,综述了近年来利用纳米物质、荧光物质及其他物质添食制备改性蚕丝的研究进展,客观分析了不同添食物质对蚕丝结构、力学性能及热性能等的影响,展望了添食法未来的研究及发展方向。

Silk is a natural protein fiber that is widely used in textile,clothing,biomedicine and other fields.The formation of silk is a complicated process.Firstly,the silk fibroin proteins are synthesized in posterior silk gland.Then,liquid silk fibroin proteins are transported to the middle silk gland and are mixed together with sericin secreted in middle silk gland.These mixture are transported to the front of the silk gland and spinneret under the pressure of the lumens.The secondary structure of silk protein are adjusted and varied under the shear force through the muscular activity in silk-press area.These silk proteins are extruded quickly with the swinging of silkworm’s head and the solid silk fiber is formed finally.Although silk has excellent performance,it still has some defects such as poor antibacterial activity and low ultraviolet resistance,which limits the application of silk and the further development in silk industry.Modifying silk and endowing it new functions can expand the application field of silk and promote the development of silk industry.The feeding method,with the advantages of simplicity,high efficiency,environmental protection and large-scale production,can modify the properties of silk in origin,and it is the most effective method to obtain modified silk in large scale.The choice of feeding ingredients is crucial in silkworm feeding method.First of all,feeding ingredients should be nontoxic.After feeding,the physical activities and the vital movement of silkworm should not be influenced.Secondly,the size of feeding ingredients must be the focus.Moreover,the selected ingredients must have outstanding properties.Combined with the above factors,nanoparticles become the preferred materials for feeding silkworm.Researchers have made some achievement through trial and exploration of different nanoparticles.The mechanical properties of silk are remarkably improved and the thermal stability of silk is also improved under the premise of the soft and smooth nature of silk fiber.So far,the mechanical properties of silk can be increased by 111.25%through the feeding of nanoparticles.The fluorescent silk has great application value in many fields including biomedical engineering,optics and optoelectronics.In recent years,a variety of methods have been used to prepare fluorescent silk,but most of them are not environment-friendly and difficult to have the mass production.Colored fluorescent silk has been obtained by feeding fluorescent dyes or rare earth phosphor to silkworms during their fifth instar.The fluorescence silk prepared by this method not only has the good fluorescence properties,but also has the excellent fluorescence stability.Howe-ver,the feeding of fluorescent materials may affect the physical activities and vital movement of silkworms and reduce the mechanical properties of silk.In order to prepare silk with different functions,researchers have utilized different types of feeding substances.The nitrogen-containing substances,superfine down powder,pigment and so on have been chosen to feed silkworm and the cocoon with good properties and modified silk with excellent mechanical properties have been gained.In this paper,the structure and properties of modified silk prepared by feeding nanoparticels,fluorescent materials and other ingredients were reviewed in detail.The effect of different feeding ingredients on silk structure,mechanical properties and thermal stability were discussed objectively.And the future study and development trend of the silkworm feeding method were proposed.