Structure, properties, and functional diversity of spider aciniform silk

Biomaterials are becoming increasingly popular in solving applied problems. Aciniform silk (wrapping silk) is one of the seven known types of silk secretions orb-web spiders produce. It has an impressive set of mechanical properties suggesting a high, hereto unexplored potential for textile and biomedical applications. Here we have summarized existing knowledge and identified the gaps in our understanding of the structure, functions, properties and biology of aciniform silk. Aciniform silk is composed of the protein aciniform spidroin (AcSp), which is characterized by relatively lower percentages of alanine and glycine than dragline silk. The specific mix of alpha helices and beta sheets is believed to bring about its great toughness and elasticity. The combination of high toughness and extensibility makes swathes of aciniform silk an ideal tool to keep the prey wrapped, but also for the protective encasing of spider egg clutches. Understanding of the relationship between the composition, properties and biological functions of aciniform silk is still rudimentary, as current studies are mostly mono-focal and barely apply an integrative approach. Closing this gap requires better integration of material science with ecological and evolutionary aspects. This will not only benefit a better understanding of why and how animals use silks, but it will also enable the production of better silk-inspired biomaterials with superior properties.