Multi-functional epoxides cross-linked collagen sponges for tissue engineering scaffolds

With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products,the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century.In present work,the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds,which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications.The bi-to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors,then using freeze-drying to form the final sponges.The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440μm.The sponges had presented the resistance to enzymatic degradation,shape-remaining ability,and reversible compressibility in aqueous environments,which all could be regulated through the functionalities of epoxides.The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higherfunctionality of epoxides would bring higher cross-linking degree.Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors,and improve the compressive strengths and thermal stabilities of sponges.Nevertheless,the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.

Factors affecting thermal stability of collagen from the aspects of extraction,processing and modification

Collagen,as a thermal-sensitive protein,is the most abundant structural protein in animals.Native collagen has been widely applied in various fields due to its specific physicochemical and biological properties.The beneficial properties would disappear with the collapse of the unique triple helical structure during heating.Understanding thermal stability of collagen is of great significance for practical applications.Previous studies have shown the thermal stability would be affected by the different sources,extraction methods,solvent systems in vitro and modified methods.Accordingly,the factors affecting thermal stability of collagen are discussed in detail in this review.

Investigation of the solubility and dispersion degree of calf skin collagen in ionic liquids

The dissolution of collagen in ionic liquids(ILs)was highly dependent on the polarity of ILs,which was influenced by their sorts and concentrations.Herein,the solubility and dispersion degree of collagen in two sorts of ILs,namely 1-ethyl-methylimidazolium tetrafluoroborate([EMIM][BF4])with low polarity and 1-ethyl-3-methylimidazolium acetate([EMIM][Ac])with high polarity in a concentration range from 10% to 70% at 10℃ were investigated.When 150 mg of collagen was added to 30 mg of ILs,the minimum soluble collagen concentration was 0.02 mg/mL in 70%[EMIM][BF4]with lowest polarity and the maximum was 3.57 mg/mL in 70%[EMIM][Ac]with highest polarity,which indicates that soluble collagen and insoluble collagen fibers were both present.For insoluble collagens,differential scanning calorimetry showed that the thermal-stability was weakened when increasing the ILs concentration and polarity,and the fiber arrangement was looser with a more uniform lyophilized structure,observed by atomic force microscopy and scanning electron microscopy.For soluble collagens,electrophoresis patterns and Fourier transform infrared spectroscopy showed that no polypeptide chain degradation occurred during dissolution,but the thermal denaturation temperature decreased by 0.26℃~7.63℃ with the increase of ILs concentrations,measured by ultra-sensitive differential scanning calorimetry.Moreover,the aggregation of collagen molecules was reduced when ILs polarity was increased as determined by fluorescence measurements and dynamic light scattering,which resulted in an increased loose fiber arrangement observed by atomic force microscopy.If the structural integrity of collagen needs to be retained,then the ILs sorts and concentrations should be considered.

GENERALIZED p-VALUES FOR TESTING REGRESSION COEFFICIENTS IN PARTIALLY LINEAR MODELS

The one-sided and two-sided hypotheses about the parametric component in partially linear model are considered in this paper. Generalized p-values are proposed based on fiducial method for testing the two hypotheses at the presence of nonparametric nuisance parameter. Note that the nonparametric component can be approximated by a linear combination of some known functions, thus, the partially linear model can be approximated by a linear model. Thereby, generalized p-values for a linear model are studied first, and then the results are extended to the situation of partially linear model. Small sample frequency properties are analyzed theoretically. Meanwhile, simulations are conducted to assess the finite sample performance of the tests based on the proposed p-values.

Design and experiment of the pneumatic double disc precision seed metering device for Chinese flowering cabbage

Single seed metering devices for Chinese flowering cabbage planting machines have suffered such deficiencies as low efficiency,poor accuracy,and instability.To overcome these limitations,a pneumatic double disc precision seed metering device was designed.This innovative device can simultaneously plant four rows,considering the specific agricultural requirements and the geometric characteristics for Chinese flowering cabbage seeds.The precise parameters of the key component seed disc were derived through theoretical calculation.In addition,a detailed account was given for the working principle and workflow of the seed metering device.The discrete element method and EDEM software were employed to optimize the seed disc by exploring the effects of seed disc rotational speed and interleaving seed slots on seed viability.Orthogonal rotation experiments were conducted to evaluate the impact of seed disc rotational speed and negative pressure.While rates of qualified seeding,double seeding and missing seeding were adopted as test indicators.Testing results show that,at a seed disc rotational speed of 41.5 r/min and a negative pressure of 3.80 kPa,the average qualified seeding rate is 90.13%,the average missing seeding rate is 3.30%,and the average double seeding rate is 6.02%.These values satisfy the agricultural requirements for planting Chinese flowering cabbage.The findings can also provide valuable insights for the structural optimization and design of precision seed metering devices for Chinese flowering cabbage.

INTEGRAL-TYPE TESTS FOR GOODNESS-OF-FIT

A family of integral-type goodness-of-fit tests is investigated. This family includes some existing tests, such as the Cramer-von Mises test and Anderson-Darling test, etc. The asymptotic distributions of the tests in the family under the null and local alternative hypotheses are established. The almost sure convergence under a fixed underlying distribution is obtained. Furthermore, simulations are conducted to compare the powers of the tests in the family. Simulation results show that for different alternatives, the more powerful tests are different, and the parameter ）, has great influence on the tests in small sample cases.

LARGE SAMPLE AND ROBUST PROPERTIES OF L^2-MEDIAN

As a competitive depth, L^2-depth is modified from L^2-depth. Its induced median is called L^2-median. Basic properties of the median and its sample version are provided. Especially, the strong consistency of sample median is gained under weaker condition. Robustness of the median and its sample version is discussed. Besides ease of computation, it is shown that L^2-median has both good large-sample and robust properties. Simulation studies are also given to compare the breakdown point of L^2-median with that of other depth-induced medians.

High-strength collagen/delphinidin film incorporated with Vaccinium oxycoccus pigment for active and intelligent food packaging

This study developed an active and intelligent collagen-based packaging film with high strength for visually monitoring the freshness of fish.The results of scanning electron microscopy and atomic force microscopy showed that the film based on cross-linked collagen/delphinidin catalyzed by laccase exhibited a denser layer structure and a rougher surface.The dry and wet tensile strengths of the laccase-catalyzed collagen/delphinidin film(Col/Dp-LA film)increased by 41.74 MPa and 13.13 MPa in comparison with that of the pure collagen film,respectively.Moreover,the Col/Dp-LA film presented good antioxidant and barrier properties demonstrated by the results of free radical scavenging rate,light transmission rate,and water vapor permeability.The intelligent collagen-based film was obtained by incorporating Vaccinium oxycoccus pigment into the Col/Dp-LA film,which could change color under different pH values.When applied to the preservation offish fillets,the film could release Dp to minimize oxidative rancidity and prolong the shelf life of the fish for 2 days.Meanwhile,the film showed visual color changes from purplish-red to greyish-blue after the fish spoilage.These results indicated that the collagen film treated with delphinidin,laccase,and Vaccinium oxycoccus pigment has potential application value in the field of active and intelligent food packaging.