In order to endue silk fibroin (SF) sponges with antibacterial function, positively charged poly(hexamethylene biguanide) hydrochloride (PHMB) was incorporated in SF through electrostatic interaction and by freeze-drying technique. The influence of PHMB on the structure and antibacterial activities of SF sponges was investigated. The zeta potential of SF was increased significantly when PHMB was incorporated in SF. The pores with size from 80 to 300 µm and the microscale holes in the pore walls within PHMB-loaded SF sponges provided the channels of PHMB release. The PHMB loaded in the porous sponges showed continuous and slow release for up to 20 days. Effective growth inhibition of both Escherichia coli and Staphylococcus aureus was achieved when the mass ratio of PHMB/SF was higher than 2/100. These results suggest that the porous PHMB/SF sponges have the potential to be used as a novel wound dressing for open skin wounds.

Aim: To obtain a gene carrier that can effectively deliver loaded therapeutic genes to tumor cells, avoid toxic effects on normal cells and reduce nonspecific adsorption of plasma proteins. Methods: The conjugate of poly(ethylene glycol) (PEG) and MMP2SSP (PEG-MMP2SSP) was covalently coupled to cationized Antheraea pernyi silk fibroin (CASF) through disulfide bond exchange reaction to obtain a PEG-MMP2SSP-modified CASF (CASFMP). Results: The PEG chains were effectively cleaved from the CASFMP by MMP2. CASFMP/pDNA complexes inhibited human fibrosarcoma cell proliferation, and its cytotoxicity to human normal embryonic kidney cells was significantly lower than that of poly(ethylenimine)/pDNA after coculturing with cells for 24 h. Conclusion: CASFMP is a promising compound for use in gene therapy.

Summary. Sections of the retrosplenial cortex from adult and newborn mouse brains were observed with a light microscope. The retrosplenial cortex of the adult animals contained many neurons (10% of the total), including some dark neurons, with perineuronal sulfated proteoglycans detectable with cationic iron colloid and aldehyde fuchsin. The retrosplenial cortex of the adult animals also contained many neurons (10% of the total) with cell surface glycoproteins reactive to lectin Vicia Uillosa, soybean or Wisteria floribunda agglutinin. Double staining showed that the majority (75%) of the neurons labeled with lectins were stained with cationic iron colloid, and that some (25%) of them were not stained with this colloid. Double staining also showed that some (25%) of the neurons stained with cationic iron colloid were not labeled with lectins. These findings indicate that the perineuronal sulfated proteoglycans are, at least partly, independent from the cell surface glycoproteins. Observations of the sections from the newborn animals revealed that the perineuronal sulfated proteoglycans were produced by the associated satellite astrocytes 3-4 weeks after birth, and that the cell surface glycoproteins were produced by the associated nerve cells at earlier stages, or 2-3 weeks after birth. Dark neurons began to appear 3-4 weeks after birth. These dark neurons or their Golgi complexes were also reactive to lectins, suggesting the production of cell surface glycoproteins.Our light and electron microscopic studies of tissue sections stained with cationic iron colloid and aldehyde fuchsin have revealed the occurrence of many neurons with intensely negatively charged surface coats or perineuronal sulfated proteoglycans in the human brain (MURAKAMI et al

The present study aimed for a clear visualization of faintly deposited colloidal iron in tissue sections for light microscopy. Paraffin blocks containing paraformaldehyde-fixed brain tissue from healthy adult mice were cut into sections 10-15 microm thick. After deparaffinization, the sections were stained with fine cationic iron colloid at a pH value of 1.0-1.5, and treated with a mixture of potassium ferrocyanide and hydrochloride for Prussian blue reaction. Some sections were further treated with Bodian's protein silver after the Prussian blue reaction. This sensitized development of Prussian blue reaction with Bodian's protein silver more clearly visualized the faintly deposited cationic colloidal irons than the demonstration by Prussian blue reaction alone, and allowed an enhanced visualization of the perineuronal nets of sulfated proteoglycans in the brain. Thus, such fine perineuronal sulfated proteoglycans as those in the CA3 field of the hippocampus, which are weakly stained with cationic iron colloid and usually overlooked by a demonstration with only a Prussian blue reaction, could be clearly visualized with striking contrast by the sensitized development with Bodian's protein silver after the Prussian blue reaction. Preliminary hyaluronidase digestion erased Bodian's protein silver development of perineuronal sulfated proteoglycans. Though some axonal fibers were also additionally stained with Bodian's protein silver itself, this sensitized development is useful to enhance such weak colloidal iron signals as are hardly detectable by only Prussian blue reaction.

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