Functional designing of natural amino acids (NAA) has received considerable attention in recent years due to its excellent biocompatibility. A novel self-assembling NAA, peptide RAG-16, was designed by hybridizing the characteristic silk fibroin motif (Gly-Ala) with an ionic complementary peptide sequence (Arg-Ala-Asp-Ala) in our study. The self-assembly structure, viscoelastic property, and cyto compatibility of the peptide were investigated by atomic force microscopy, rheometer, Fourier transform infrared spectrum, and inverted fluorescence microscope. RAG-16 was able to form a three-dimensional compact network structure in water. High mechanical performance of the peptide hydrogel was found due to the increase of the silk I structure from inserted fibroin motif segment. Fluorescence staining showed that vast majority of MC3T3-E1 cells in the RAG-16 hydrogel could adhere to, survive, and distribute on different planes. To sum up, in this experiment, the functional designing of the NAA has exhibited its potential application in biomedical field.
Amino Acids ; chemistry ; Biocompatible Materials ; chemistry ; Fibroins ; chemistry ; Hydrogels ; chemistry ; Models, Molecular ; Nanostructures ; chemistry ; ultrastructure ; Peptides ; chemistry ; Silk ; chemistry

A multiple-stimuli-responsive drug-conjugated cross-linked micelles was prepared by radical copolymerization. The chemical structure, morphology, and size of the cross-linked micelles were characterized, and the drug loading of the micelle was calculated. The experimental results indicated that the hydrodynamic size of the drug-loaded micelles were about 100 nm, and the as prepared micelles could be degraded and swelled in presence of reducing glutathione (GSH). The low critical solution temperature (LCST) of the micelle was around 39.4℃. According to the experimental results, the micelles will shrink at temperature above the LCST. Subsequently, the accumulative drug release rate was up to 91.78% under acidic (pH 5.0), reductive (GSH 10 mmol/L) and high temperature (42.0℃) conditions mimicking the tumor microenvironment, while a relatively low release rate of 1.12% was observed without stimulation. The drug-conjugated cross-linked micelles showed a strong cell uptake behavior. In the cytotoxicity assay, the micelles exhibited effective anti-cancer activity and excellent biocompatibility. In brief, the experimental results show that the as-prepared drug-conjugated cross-linked micelle exhibits multiple stimuli-responsiveness, which holds great promise for anti-cancer drug delivery.