Chitosan-graft-poly（lactic acid） （CS-g-PLA） copolymer was synthesized through emulsion self-assembly in a water-in-oil （W/O） microemulsion. The water phase was composed of CS aqueous solution, while the oil phase was made up of PLA in chloroform. The W/O microemulsion was fabricated in the presence of surfactant span-80 and the self-assembly was performed between PLA and CS under the effect of N-（3-dimethylaminopropyl）-N＇ethylcarbodiimide hydrochloride （EDC＇HCI）. FTIR and IH-NMR analysis indicated PLA was grafted onto the backbone of CS via the reaction between the carboxyl groups in PLA and the amino groups in CS. 1H-NMR characterization further revealed the grafting content of PLA was 16%. The obtained CS-g-PLA could self-assemble to form micelles, their size distributed in the range of 125-375 nm with average diameter of 142 nm. The present design integrates the favorable biological properties of CS and the excellent mechanical properties of PLA, which makes CS-g-PLA copolymer a promising candidate as a carrier for targeted bioactive molecules delivery.
The woodpecker does not suffer head/eye impact injuries while drumming on a tree trunk with high acceleration （more than 1000xg） and high frequency. The mechanism that protects the woodpecker＇s head has aroused the interest of ornithologists, biologists and scientists in the areas of mechanical engineering, material science and electronics engineering. This article reviews the literature on the biomechanisms and materials responsible for protecting the woodpecker from head impact injury and their applications in engineering and human protection.
