Self-Assembly of Synthetic and Biological Polymeric Systems of ...

the energy landscape of the aggregation process, which makes the fibrillation process difficult.
In contrast, under acidic conditions a continuous progressive enhancement of HSA fibrillation
is observed as the electrolyte concentration in solution increases. Both the distinct protein
ionization state and the initial structural states of the protein before incubation may be the
origin of this behavior. According to ThT fluorescence data, the fibrillation kinetics of HSA does
not show a lag phase except at pH 3.0 in the absence of added salt. The HSA fibrils obtained at
the end of the fibrillation process show structural features typical of classical amyloid fibers, as
denoted by XRD, CD and TEM techniques. Finally, we describe the physical and structural
properties of additional supraself-assembled structures of HSA under solution conditions in
which amyloid fibrils are formed. We have detected the formation of ordered aggregates of
amyloid fibrils, i.e. spherulites, by means of polarized optical microscopy, laser confocal
microscopy and TEM. These structures possess a radial arrangement of the fibrils around a
disorganized protein core, and have sizes of several micrometers.
Figure 5.6 pH conditions and helical contents of the five organized forms of albumin including
crystal structure of the N form, and the proposed configuration of the F and E forms (136).
5.5.- Amyloid fibrils as biomaterials
The bottom-up strategy takes advantage of the functionality of molecular materials and
molecular recognition properties for self-assembly (142). The construction of functional
nanomaterials and components through the bottom-up strategy has potential applications in
different areas as electronics, tissue engineering, drug delivery, sensing… (143)(144). In this
regard, self-assembly properties of biomacromolecules, as phospholipids, DNA, peptides, and
proteins, can be an alternative for the obtention of new materials.
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