Chitin-based scaffolds are an integral part of the skeleton of the marine demosponge Ianthella basta

The skeleton of demosponges such as Ianthella basta is known to be a composite material formed from organic constituents, mostly collagenous proteins (spongin). Here, we show for the first time that a filigree, chitin-based scaffold is an integral constituent of the skeleton of I. basta. These chitin-based scaffolds can be isolated from the sponge skeletons using an extraction and purification technique based on the treatment with alkaline solutions. Solidstate 13C NMR, Raman, and FTIR spectroscopy as well as chitinase digestion reveal that the extracted material indeed consists of chitin. The morphology of the extracted material has been determined by light and electron microscopy. It consists of cross-linked chitin fibers of ca. 40 – 100 nm diameter forming a micro-structured network. The overall shape of this network closely resembles the shape of the integer sponge skeleton. For the first time, solidstate 13C NMR spectroscopy is used to characterize chitin from the skeleton of a marine sponge on a molecular level. The 13C NMR signals of the chitin-based scaffolds are relatively broad indicating a high amount of disordered chitin, possibly in the form of surface-exposed molecules. X-ray diffraction shows that the scaffolds extracted from I. basta are indeed lowly crystalline and consist of loosely packed chitin with large surfaces. The spectroscopic signature of these chitin-based scaffolds is closer to that of alpha-chitin than beta-chitin.