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BACKGROUND: Silk fibroin and chitosan are commonly used as scaffolds in tissue engineering, but there are some shortcomings in their separate application. When they are mixed, they can be modified each other. They give full play to each other's advantages and become ideal composite scaffolds. OBJECTIVE: To prepare Silk fibroin/chitosan composite scaffold and determineits properties. METHODS: The silk fibroin/chitosan composite scaffolds were prepared by freeze-drying method. The morphology and structure of the composite scaffolds were examined by scanning electron microscopy. The properties of the composite scaffolds were tested by thermogravimetric analysis, mechanical properties test, and cytotoxicity test. The quaternion chitosan was prepared. The nuclear magnetic resonance spectrum was detected by nuclear magnetic resonance instrument. The potential and particle size distribution were detected by Zeta potentiometer. The protection of DNA was detected by gel eledrophoresis. The binding with DNA was observed by transmission electron microscope. RESULTS AND CONCLUSION: (1) The results of scanning electron microscopy showed that the silk fibroin/chitosan composite scaffolds had a good three-dimensional pore structure, with a pore size of 50-100 urn. (2) The results of thermogravimetric analysis showed that when the temperature was less than 200 °C, the mass loss rate of silk fibroin/chitosan composite scaffold was lower. When the temperature increased to 200-500 °C, the mass loss rate of the scaffold began to accelerate, and the loss amount increased. At 800 °C, the residual mass of the composite scaffold was 38%. (3) The maximum strain of silk fibroin/chitosan composite scaffold reached 94.94%, and the maximum stress was 7.01 MPa. (4) The results of CCK-8 experiment showed that silk fibroin/chitosan composite scaffolds had no cytotoxicity to rabbit bone marrow mesenchymal stem cells and had good cell compatibility. (5) The results of nuclear magnetic resonance spectra showed that the quaternion degree of quaternary ammonium chitosan was about 20%. (6) The particle size distribution of quatemized chitosan was (588.56±52.39) nm, and the surface of quatemized chitosan was positively charged with a potential of (16.3±3.92) mV, which was beneficial to the combination with DNA. (7) The results of gel electrophoresis experiments showed that the higher the proportion of quaternion chitosan, the better the encapsulation of DNA. When the ratio of chitosan/DNA was 1 : 3, the encapsulation effect was achieved. (8) The results of transmission electron microscopy showed that most of the particles of quatemized chitosan/DNA were solid and round; the particle size difference was small; and the average particle size was about 200 nm. (9) The results showed that silk fibroin/chitosan composite scaffolds had a good biocompatibility and cell permeability, which was conducive to the growth of cells between scaffolds. [ABSTRACT FROM AUTHOR]

By cloning, sequencing and bioinibrmatics analysis, the Bmβ-COP gene was identified- The expression pattein in different tissues was detected to reveal the relationship between Bmfi-COP expression and silk productivity in silkworm. The result snowed that in genome of B. morif Bmβ-COP is the unique locus encoding β-COP protein. No alternative splicing event occurres. There is no difference among the expression patterns of Bmβ-COP gene in different tissues of different silkworm variety. No direct relationship between Brnfi-COP expression and different silk protein production of silkworm varieties was identified, but knocking down Bmβ-CQP perturbs the development and function of silk gland, resulting in worse silk productivity. [ABSTRACT FROM AUTHOR]

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Silk-based biomaterials are featured with excellent mechanical properties, good biocompatibility and biodegradability, which contribute to their potential applications in biomedical field. The current recognition of silk protein materials in structure and function provides a basic theory for the transformation of silk protein into new types of biomaterials. In addition, exogenous sequences encoding new peptide or structural domain can be inserted into the maternal gene sequences encoding silk proteins through genetic engineering technology to synthesize novel silk-based biomaterials with unique functions. This review summarizes the current trend and development perspective of genetically engineered functional silk-based materials for biomedical applications.