Abstract
Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin’s poor mechanical properties in wet conditions and the difficulties in transforming it into an applicable form. To overcome these challenges, we created a novel biomimetic chitin composite. This regenerated chitin, prepared with ionic liquid, showed improved mechanical properties in wet conditions by mimicking insect cuticle and squid beak sclerotization, i.e., catechol-meditated cross-linking. By ionic liquid-based heat treatment, dopamine oxidation produced melanin-like compounds and dopamine-meditated cross-links without any solvent evaporation and oxidant utilization. The dopamine-meditated sclerotization increased the ultimate tensile strength (UTS) of the regenerated chitin by 2.52-fold, measured after six weeks of phosphate-buffered saline (PBS) submersion. In addition, the linear swelling ratio (LSR) of the chitin film was reduced by about 22%. This strategy raises a possibility of using regenerated chitin as an artificial hard tissue in wet conditions.
Highlights
IntroductionChitin (a linear structural polysaccharide mainly composed of poly-N-acetyl-Dglucosamine connected by β-1,4 linkages) is one of the main hard-tissue components of crustaceans, insects and fungi [1]
Chitin is one of the main hard-tissue components of crustaceans, insects and fungi [1]
Regenerated films of pure chitin and dopamine-containing composites were successfully fabricated via the ionic liquid process
Summary
Chitin (a linear structural polysaccharide mainly composed of poly-N-acetyl-Dglucosamine connected by β-1,4 linkages) is one of the main hard-tissue components of crustaceans, insects and fungi [1]. Ionic liquid is an eco-friendly solvent, as it is recyclable and generates hardly any air-pollutants, due to its non-volatility, low-reactivity and low-flammability This process has been shown to directly convert raw crustacean waste from crab and shrimp into chitin products without the need for purification [10]. During the sclerotization of insect cuticle, oxidation of catechol moieties improves mechanical properties in wet conditions by producing hydrophobic polyphenolic compounds, such as melanin, and cross-linking reactions with chitin filaments and proteins [14,15]. Mechanical properties and resistance to swelling of regenerated chitin in wet conditions were improved by biomimetic sclerotization, i.e., the oxidation of dopamine, a physiological catecholic material [18]. 1-ethyl-3-methylimidazolium acetate ([C2mim] [OAc], an ionic liquid) solution without using toxic cross-linking agents, such as aldehyde, glutaraldehyde and periodate [19,20]
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