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    Chitosan loses innate beneficial properties after being dissolved in acetic acid: Supported by detailed molecular modeling
    (American Chemical Society, 2020) Bilican, İsmail; Pekdemir, Sami; Önses, Mustafa Serdar; Akyüz, Lalehan; Altuner, Ergin Murat; Koç Bilican, Behlül; Zang, Liansheng; Mujtaba, Muhammad; Muler?ikas, Povilas; Kaya, Murat
    Chitosan, which is obtained via deacetylation of chitin, has a variety of uses in agriculture, food, medicine, pharmaceuticals, and cosmetics. Industrial chitosan is in a gel form, which is produced by dissolving in acetic acids. These gels can be chitosan-only films or composite films that include other ingredients such as plant extracts or other polymers. Chitosan-based films, however, are not as natural as chitosan dissolved in weak acids, and they lack some of chitosan's innate properties. In this study, natural chitosan films (NCFs) were obtained from the pupa shells of black soldier flies through a process that maintains the original structure. The semisynthetic film (SCF) was then produced by dissolving the same NCF in acetic acid along with glycerol and glutaraldehyde. The semisynthetic film remarkably lost the beneficial properties of the natural film. The deteriorated characteristics include hydrophobicity, crystallinity, thermal properties, as well as a loss of fibril structure and a reduction in bacterial attachment. Moreover, the Ag-deposited NCFs manifested strikingly higher surface-enhanced Raman scattering activity as compared with the semisynthetic ones. These results, including the molecular modeling data, demonstrate that dissolving chitosan in acetic acid changes its polymeric structure. © 2020 American Chemical Society.
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    Production of natural chitin film from pupal shell of moth: Fabrication of plasmonic surfaces for SERS-based sensing applications
    (Elsevier Ltd, 2021) Chen, Yong-Ming; Pekdemir, Sami; Bilican, İsmail; Koç Bilican, Behlül; Çakmak, Betül; Ali, Asad; Zang, Lian-Sheng; Önses, M. Serdar; Kaya, Murat
    Commercially available types of chitin or chitin isolate are usually in powder form and are nanofibrous in microstructure. However, the surface characteristics of natural chitin in the body of insects are currently understudied. Herein, natural chitin film was successfully produced from bio-waste of insect pupae of the Japanese giant silkworm. Two different surface morphologies of the chitin film were observed. We report for the first time a micropapillary surface structure of chitin which was observed on the dorsal side of the film. To further potential of the micropapillary structured natural chitin in sensing applications, we develop a protocol for generating a nanoscopic film of Ag using thermal evaporation. The Ag-deposited natural chitin films exhibited surface-enhanced Raman scattering (SERS) activity to an extent depending on the structure of the film. In conclusion, materials science has been expanded by addition of a natural, three-dimensional chitin film with utilizable properties.