丝素纳米纤维及丝素复合纳米纤维在生物医学材料领域应用的研究进展

丝素蛋白独特的氨基酸组成和空间结构,使其成为一种具有良好生物相容性和可降解性的生物材料,采用高压静电纺丝技术制备的丝素纳米纤维与丝素复合纳米纤维更是赋予了丝素纤维在生物医学材料领域更为良好的应用性能。本文系统介绍了近年来静电纺丝素纳米纤维及丝素复合纳米纤维在生物医学材料(包括骨组织工程材料,软骨、伤口、神经和血管修复材料,药物缓释材料等)领域的应用及改性研究进展,在此基础上简要展望了静电纺丝素纳米纤维研究需要创新的重点课题。     

静电纺丝素蛋白与无机物复合纳米材料的研究进展

利用静电纺丝技术制备再生丝素纳米纤维具有高比表面积、高孔隙率以及良好的生物相容性的优势,所以广泛应用于生物材料和组织工程等领域。单一的再生丝素纳米纤维脆性大,力学性能差,而采用由不同的无机粒子或合成高聚物与丝素共混制备复合纳米纤维可以极大地改善单纯使用一种材料的适应性,并且使复合纤维同时具备多种优势。本文综述近年来国内外静电纺丝制备再生丝素与无机粒子或合成高聚物复合纳米纤维的研究现状,旨在为提高丝素纳米纤维的综合性能,拓展其应用。     

丝素蛋白作为药物载体的研究进展

丝素蛋白作为一种具有优良性能的天然高分子材料,在生物医学领域被深入研究。丝素蛋白材料形态易塑,生物相容性良好,生物降解性可控且降解产物无毒,因此是理想的药物载体。本文综述了丝素膜、丝素凝胶、丝素纳米纤维和丝素微球等不同类型的药物载体,并展望了其研究和应用前景。     

用丝素蛋白涂覆涤纶织物的研究

将丝素蛋白溶液涂覆于经过化学刻蚀处理的涤纶织物上,获得丝素蛋白涂覆涤纶织物,并对丝素蛋白涂覆涤纶织物进行理化性能检测和结构特性分析。结果表明,丝素蛋白涂覆整理涤纶织物的涂覆增重率为11.6%,热水溶失保持率为84.17%,回潮率增加3.8倍,涂覆涤纶织物的断裂强度和伸度略有降低,但其静电压峰值和静电压衰减时间都得到了明显的改善。涂覆涤纶织物的纤维间填充了丝素蛋白,红外分光光谱检测到丝素蛋白的吸收特征,初步显示了丝素蛋白涂覆涤纶织物具有改善织物性能的效果。     

丝素的多功能开发与应用

丝素又名丝心蛋白,占整个茧丝纤维的2/3,蚕儿吐的茧丝在脱去包裹在外层的丝胶后,即得丝素.丝素纤维在缫丝厂根据生产纤度的要求,数根合并为一根生丝.尽管丝胶和丝素的氨基酸组成类别基本相同,但丝胶是水溶性的,丝素是非水溶性的,因此用作纤维素材的是丝素,丝胶在制丝加工过程中被脱出,是丝绸厂废水的主要成分.丝素主要由侧链较小的甘、丙、丝氨酸组成,此外还含有一些大侧链酪、缬、脯等氨基酸.经检测,组成丝素的18种氨基酸中,包含了8种人体必需的氨基酸,其二级结构呈β-折叠片层,多肽链呈锯齿状,反平行式β-折叠片层平行堆积成多层结构,截面积呈角圆的三角形.     

丝素作为固定化酶载体材料的研究进展

酶的固定化在化学、生物医学以及生物感应器等领域应用较广。固定化酶的效果在很大程度上取决于载体结构。丝素作为固定化酶载体材料有其独特的优势。本文综述了国内外以不同的丝素形态作为固定化酶载体材料的研究进展,重点介绍了非纳米丝素固定化酶和纳米丝素固定化酶（丝素纳米颗粒和丝素纳米纤维）的研究进展。     

纳米TiO2改性丝素复合膜的研究

为了进一步改善丝素蛋白膜的结构性能,用溶胶凝胶法制备了不同比例纳米TiO_2改性的丝素蛋白复合膜。对生成的纳米粒子进行粒径分析表明,成膜前后纳米粒径约为80nm左右。对丝素膜的结构和热性能用X射线衍射(XRD)、扫描电镜(SEM)、热重分析(TGA和DTG)进行表征：XRD测试结果表明,随着纳米TiO_2的加入,复合丝素膜的结晶结构从SilkⅠ向SilkⅡ转化;SEM测试结果表明,TiO_2能与丝素形成较好的键合;TGA和DTG测试表明,复合丝素膜的热转变温度较之于纯丝素膜有所提高。     

丝素蛋白微载体药物递送系统的研究进展

家蚕丝素蛋白是一种天然的高分子,具有生物相容性、可降解性和可塑性,在医药学领域有巨大应用前景.以丝素蛋白为材料构建的微载体药物递送系统能够有效运输药物至疾病部位,控制药物的释放行为,提高药物的治疗效率.本文介绍了药物载体递送系统概况,对丝素蛋白的结构、性能,丝素蛋白微载体药物递送系统形式,所装载药物分类及其在动物水平上的疾病治疗研究进行阐述,并对丝素蛋白微载体的现存问题和发展前景进行分析,为进一步开发丝素蛋白药物递送系统提供参考依据.     

家蚕丝素蛋白与无机纳米颗粒复合材料的构建及其应用的研究

家蚕丝素蛋白是天然生物大分子,具有良好的生物相容性、可控的降解性以及优异的机械性能,能够作为高分子材料在生物医学、光学、电子等多个领域进行应用。与此同时,无机纳米颗粒因其小尺寸与多功能特性,在化工、材料、医学等多个行业发挥重要的作用。将丝素蛋白与无机纳米颗粒结合,构建复合材料能够发挥两者的优势,获得特殊的性能,拓展材料的应用范围。近年来,基于丝素蛋白与无机纳米颗粒的复合材料被广泛研究,新的功能特性被挖掘,应用形式多样,这对于提升蚕丝蛋白的应用价值具有重要意义。本文综述了丝素蛋白与无机纳米颗粒复合材料的研究进展,包括复合材料的类别、材料的复合形式、复合材料的应用,并对丝素蛋白与无机纳米颗粒复合材料的发展做出展望。     

纳米二氧化钛-丝素复合膜的溶解性初探

研究了纳米二氧化钛在丝素溶液中的分散性 ,制备了不同配比的纳米二氧化钛—丝素复合膜 ,并对复合膜和纯丝素膜的溶解性能进行了初探。发现复合膜的溶失率比纯丝素膜的溶失率有所下降 ,认为添加二氧化钛纳米粒子的丝素可用于纤维、织物的功能性整理     

Gelatinase activity in synovial fluid and synovium obtained from healthy and osteoarthritic joints of dogs

OBJECTIVE: To determine matrix metalloproteinase (MMP) activity in synovial fluid (SF) obtained from the joints of dogs with degenerative joint disease (DJD) secondary to various underlying conditions. SAMPLE POPULATION: 35 samples of SF obtained from 18 clinically normal (control) dogs and 34 samples of SF obtained from 17 dogs with DJD; dogs with DJD were from 2 populations (client-owned dogs and research dogs that had DJD secondary to the lysosomal storage disease mucopolysaccharidosis VII). PROCEDURE: MMP activity in samples of SF was semiquantitatively examined by use of gelatin or casein zymography. Western blot analysis was performed by use of antibodies for MMP-2 and MMP-9. In addition, in situ MMP activity was observed in sections of synovial membrane obtained from healthy and osteoarthritic joints. RESULTS: Samples of SF from osteoarthritic joints had higher MMP-2 activity and dramatically increased MMP-9 activity, compared with values for healthy joints. Substrate-overlay analyses indicated minimal gelatin-degrading activity in synoviocytes obtained from control dogs, whereas greater activity was seen in osteoarthritic synoviocytes, with additional activity in the underlying tissue. CONCLUSIONS AND CLINICAL RELEVANCE: Higher MMP-2 activity and dramatic increases in MMP-9 activity were associated with the osteoarthritic state, even though MMP-2 activity was detected in healthy joints. This study expands information on MMP production in SF of osteoarthritic joints in other species and documents the similarity of MMP activity patterns regardless of the cause of DJD.     

Intramammary infusion of an Enterococcus faecium SF68 preparation promoted the involution of drying off Holstein cows partly related to neutrophil‐associated matrix metalloproteinase 9

A problem for dairy cows following milk stasis is to cope with a high risk of intramammary infection and there is a need to initiate an extensive renewal of secretory modules in mammary glands so that milk production in next lactation may be optimized. We recently reported that ultrasonicated Enterococcus faecium SF68 (SF68) is compatible with cow mammary glands and an enhancer of innate immunity during the immediate post‐milk stasis period. The current study further examines the concomitant effect of ultrasonicated SF68 on mammary tissue remodeling. Four Holstein cows each received intramammary infusions of regular antibiotic dry‐cow formula (positive control) and two different doses of SF68 in different quarters. Analyses of individual quarter secretion samples showed faster neutrophil infiltration, earlier modifications in protein composition, including caseins and lactoferrins, as well as more prompt elevation of the specific unit of 92‐kDa matrix metalloproteinase 9 (MMP9) in SF68‐infused quarters compared to the positive controls. Intramammary infusion of ultrasonicated SF68 seems able to accelerate the regression of mammary synthetic capacity and potentiate the breakdown of glandular extracellular matrix, indicating a more efficient mammary gland involution. Correlation analyses imply that the ability of ultrasonicated SF68 to induce faster neutrophil chemotaxis and the associated MMP9 release is partly responsible.     

Physiological Concentrations of Acute-Phase Proteins and Immunoglobulins in Equine Synovial Fluid

Synovial fluid (SF) is capable of reflecting infectious, immunological, or inflammatory joint conditions in horses by altering its composition and appearance. Although plasma and SF compositions are quantitatively different, this latter compartment reflects changes in plasma macromolecules. Therefore, changes in serum immunoglobulin protein concentrations tend also to alter intracapsular levels. Therefore, it is necessary to know the physiological concentrations of proteins present in SF. The aim of this study was to determine the levels of total protein, albumin, transferrin, haptoglobin, α1-acid glycoprotein, ceruloplasmin, and immunoglobulins A and G in SF of six healthy horses. The synovial proteinogram was obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The SF proteins reached a maximum of 25% of serum concentrations, varying inversely with molecular weight of the protein, except for the ceruloplasmin.     

Synovial fluid total protein concentration as a possible marker for canine idiopathic polyarthritis

Idiopathic polyarthritis (IPA) is a very common inflammatory arthropathy in the dog. Canine IPA is diagnosed mainly by detecting increased number of leukocytes in the synovial fluid (SF), which is easily influenced by glucocorticoid therapy. We obtained 31 SF samples from 24 IPA dogs prior to (n=19) and/or after (n=12) 1 to 10 weeks of glucocorticoid therapy. The SF total protein concentrations of IPA dogs were significantly higher than those of dogs with non-arthritis diseases (n=34) and healthy controls (n=10). Our data revealed that the SF total protein concentrations are not influenced by several weeks of glucocorticoid therapy. Hence, the SF total protein concentration is applicable as a diagnostic marker of canine IPA even when the patients are receiving glucocorticoid therapy.     

Distribution of penicillin-G and spiramycin to tissue cages and subcutaneous tissue fluid in calves

Antibacterial drug concentrations in serum, tissue cage fluid (TCF) and subcutaneous tissue fluid (SF), sampled either by filter paper discs or by microcapillaries, were measured after single intramuscular injections of potassium penicillin-G (KPG), procaine penicillin-G (PPG) and spiramycin adipate in calves. Concentration-time curves had essentially similar profiles in serum and SF, but peak levels were lower and occurred later in SF. From approximately four hours after drug administration, penicillin-G levels in SF were similar to levels in serum after KPG as well as after PPG administration. Elimination half-life (t1/2) of penicillin-G in serum was similar to t1/2 in SF after PPG administration but was longer in SF than in serum after KPG administration. Spiramycin concentrations were higher in SF than in serum and the t1/2 of spiramycin in SF was longer than in serum. For all three drugs, the t1/2 was longer in TCF than in serum and concentration-time curves in TCF were characterised by a slow rise and decline. The two methods of sampling SF, by filter paper discs and by microcapillaries, gave similar but not identical results. Penetration into SF and TCF, measured as the total area under curve ratio, was better for spiramycin than for penicillin-G, but the latter drug had a higher penetration ratio to TCF in the first 12 hours.     

Risk factor analysis and relative supersaturation as tools for identifying calcium oxalate stone-forming dogs

Twenty-four hour urine samples were collected from 17 calcium oxalate (CaOx) stone-forming (SF) dogs and 17 normal (N), age-, breed- and sex-matched dogs. Urinary CaOx relative supersaturation (RSS) was calculated and found to be significantly higher in the SF group than the N group. RSS measurement is not readily applicable to veterinary practice; thus, alternatives were explored. Discriminant analysis failed to identify key factors differentiating most SF from N dogs. Urinary calcium, oxalate and uric acid, which differed between the SF and N animals, were combined into a measure of relative probability of CaOx stone formation (PSF) to establish whether this approach could be used to assess the risk of CaOx stone formation in dogs. Although there was good correlation between the techniques, RSS more clearly discriminated between SF and N dogs. These data suggest that neither PSF nor discriminant analysis is preferable to RSS for assessing the risk of CaOx stone formation in dogs.     

Collagenase-1 (MMP-1) activity in equine synovial fluid: influence of age, joint pathology, exercise and repeated arthrocentesis

REASONS FOR PERFORMING STUDY: Matrix metalloproteinases (MMPs) are considered candidate biomarkers for both physiological and pathological tissue remodelling because of their key role in articular cartilage homeostasis. As disruption of the collagenous architecture is thought to be pivotal in chronic degenerative diseases such as osteoarthritis (OA), the collagenases form an interesting subset of the MMPs. The significance of any biomarker in synovial fluid (SF) can be assessed properly only when fluctuations in patterns induced by physiological processes such as development and growth, and by external influences and interventions such as exercise and repeated arthrocentesis, are known and taken into account. OBJECTIVES: To investigate the activity of MMP-1 in equine SF at different stages of development and in joints affected by OA, and the influence of exercise and repeated arthrocentesis thereon. METHODS: MMP-1 activity was determined in SF of normal joints of fetal, juvenile and mature horses, and in SF of horses suffering from OA, using an internally quenched fluorogenic peptide substrate. MMP-1 activity was also measured in SF from horses subjected to an exercise regimen and those subjected to repeated arthrocentesis. RESULTS: An age-related decline in the SF levels of active MMP-1 was observed. MMP-1 activity was 15-fold higher in fetal than in juvenile animals, which showed significantly higher MMP-1 activity levels than mature horses. In SF of OA joints, MMP-1 activity was increased. Exercise did not affect MMP-1 activity in SF, but repeated arthrocentesis (within 60 h) increased MMP-1 activity significantly. CONCLUSIONS: The high MMP-1 activity in SF of young individuals parallels the high metabolic activity occurring during rapid growth and differentiation at early age. The elevated MMP-1 activity in SF of OA joints probably reflects pathological matrix degradation, confirming the potential of MMP-1 to serve as a biochemical marker for early joint disease. Moderate exercise is not likely to influence the outcome of MMP-1 activity measurements in equine SF, but arthrocentesis should be taken into account as a possible confounding factor. POTENTIAL RELEVANCE: Given the crucial role of the collagen matrix for tissue integrity, MMP-1 activity may be a useful tool in diagnostic, therapeutic or prognostic studies in horses suspected of OA. However, care should be taken to exclude fluctuations in MMP-1 activity induced by physiological processes such as development and growth, and by interventions such as repeated arthrocentesis.     

Supplemental fat in high-energy rations for lactating cows: effects on intake, digestion, milk yield, and composition

Supplemental fats (SF) have special value in the diets of dairy cows with superior productive ability, because the high energy density of SF allows greater energy consumption and direct transfer of the fatty acids (FA) of the SF to milk fat; this increases metabolic efficiency. Some SF, especially oils with a high degree of unsaturation, disturb ruminal fermentation, decrease fiber digestibility, and lower milk fat test; however, oilseeds (e.g., whole cottonseed) can be fed without observable ruminal inhibition, probably because of a slow release of the oil into ruminal contents. A number of commercial fat supplements are available that have little effect on ruminal fermentation and are highly digestible postruminally. A product of the calcium salts of palm oil fatty acids was shown to have a NE for lactation of more than three times that of corn. As the emphasis in milk pricing formula changes from milk fat to milk protein, there is greater concern regarding the propensity of fat supplements to decrease milk protein (casein) percentage. In two studies, a supplement of ruminally protected lysine and methionine largely prevented the reduction in casein percentage that occurred with feeding SF, indicating that the amino acid profile of undegraded dietary protein is important with regard to preventing the lower casein percentage. Combining fat supplements that are slowly released in the rumen with those that are inert in the rumen will allow maximal use of SF.     

Influence of Enterococcus faecium SF68 Probiotic on Giardiasis in Dogs

Background: Giardiasis is a common, potentially zoonotic disease, and dogs often harbor and shed cysts without showing clinical signs. Treatment with the probiotic Enterococcus faecium SF68 has been shown to stimulate mucosal and systemic immunity in a variety of animal models and in young dogs, and to reduce giardial cyst and antigen shedding in rodents.
Hypothesis: Adult dogs with chronic naturally acquired giardiasis will have decreased giardial fecal cyst and antigen shedding and increased innate and adaptive immunity after 6 weeks probiotic treatment with E. faecium SF68.
Animals: Twenty adult dogs.
Methods: After a 6-week dietary equilibration period, dogs were randomized to receive E. faecium SF68 or placebo for 6 weeks, and then crossed over to the alternate treatment. We measured cyst shedding, fecal giardial antigen, fecal immunoglobulin A (IgA) concentration, and circulating leukocyte phagocytic activity at multiple timepoints to determine the effect of E. faecium SF68 on giardiasis and immune responses in these dogs.
Results: No differences were observed between placebo or E. faecium SF68 treatment for giardial cyst shedding, fecal antigen shedding, fecal IgA concentration, or leukocyte phagocytic activity.
Conclusions: Short-term treatment with E. faecium SF68 of dogs with chronic naturally acquired subclinical giardiasis fails to affect giardial cyst shedding or antigen content and does not alter innate or adaptive immune responses.