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Supramolecular nanostructures formed through self-assembly can have energy landscapes, which determine their structures and functions depending on the pathways selected for their synthesis and processing and on the conditions they are exposed to after their initial formation. We report here on the structural damage that occurs in supramolecular peptide amphiphile nanostructures, during freezing in aqueous media, and the self-repair pathways that restore their functions. We found that freezing converts long supramolecular nanofibers into shorter ones, compromising their ability to support cell adhesion, but a single heating and cooling cycle reverses the damage and rescues their bioactivity. Thermal energy in this cycle enables noncovalent interactions to reconfigure the nanostructures into the thermodynamically preferred long nanofibers, a repair process that is impeded by kinetic traps. In addition, we found that nanofibers disrupted during freeze-drying also exhibit the ability to undergo thermal self-repair and recovery of their bioactivity, despite the extra disruption caused by the dehydration step. Following both freezing and freeze-drying, which shorten the 1D nanostructures, their self-repair capacity through thermally driven elongation is inhibited by kinetically trapped states, which contain highly stable noncovalent interactions that are difficult to rearrange. These states decrease the extent of thermal nanostructure repair, an observation we hypothesize applies to supramolecular systems in general and is mechanistically linked to suppressed molecular exchange dynamics.

Background. The presence of distal bowel gas in an infant does not exclude the diagnosis of duodenal atresia. Case Presentation. We report a term neonate with Down syndrome. The infant developed vomiting and cyanosis with each feeding soon after birth. Plain film abdominal X-rays showed a nonspecific gas-filled stomach and small bowel. Duodenal atresia and an anomalous common bile were noted on an upper GI study and exploratory laparotomy. Conclusion. In the absence of a “double bubble” appearance and intestinal gas distally on a plain radiograph, one must not exclude duodenal atresia as the differential diagnosis.