Understanding the correlation between source and chiral, physichochemical properties of chitin nanocrystals; insights from beetle (Cetonia aurata) skeletal segments

Chitin properties are known to vary depending on animal taxa, organismal source, and specific skeletal segments; However, the influence of these source-dependent variations on the physicochemical characteristics of chitin nanocrystals, particularly their Bouligand architecture, remains largely unexplored. Herein, chitin nanocrystals were isolated from seven different skeletal segments of C. aurata and characterized. Significant variation was observed in nanocrystal size, with wing-derived nanocrystals averaging 320 ± 127 nm and abdomen-derived nanocrystals 203 ± 104 nm, while surface charges ranged, with thorax-1 exhibiting the highest (45.68 ± 1.2 mV). All characteristic peaks were observed for both chitin and chitin nanocrystals, with the latter displaying sharper peaks and a slight increase in crystallinity, attributed to the removal of amorphous regions. Wing-derived chitin nanocrystals showed the highest thermal stability (372 °C), potentially due to lower surface area. Chitin nanocrystals-based films were produced to investigate the chiral behavior of isolated chitin nanocrystals. All the films displayed a unique helicoidal Bouligand structure with visible pitches, except those from thorax-1. The formation of mesophase (unclear pitch in Bouligand architecture) in thorax-1 films is likely due to nanocrystal dimensions and surface charges. This is further supported by the lower roughness and contact angle values observed in thorax-1 films.