Water interplay in trehalose polymorphism

An investigation on the transformation paths of trehalose polymorphs and the interplay of water molecules is presented with the aim of underlining the role of trehalose structural and dynamic functions in the ‘‘protection” of biosystems and living organisms. To this end, physico-chemical studies have been carried out on water–trehalose interactions and on the structure and stability of the several forms, from the solution to the solid state (either amorphous or crystalline). In this paper the relevant results are critically presented and discussed with particular reference to most recent findings. The dehydration process performed under different confined conditions and controlled scan rates provides a dynamic phase diagram as a function of the time-scales of trehalose transformations and water effusion. A careful analysis of these data and of the stability of the glassy state in the presence of water evidences the reversibility of some trehalose transitions under the same conditions of natural processes of slow heating and controlled evaporation rate. This observation points at the hypothesis of the occurrence of these reversible paths at the basis of the bioprotection process. In this paper, the relevant results from our laboratory and literature are critically presented and discussed in reference to the most recent findings.