Effects of cryopreservation, decellularization and novel extracellular matrix conditioning on the quasi-static and time-dependent properties of the pulmonary valve leaflet.

Decellularized allografts offer potential as heart valve substitutes and scaffolds for cell seeding. The effects of decellularization on the quasi-static and time-dependent mechanical behavior of the pulmonary valve leaflet under biaxial loading conditions have not previously been reported in the literature. In the current study, the stress-strain, relaxation and creep behaviors of the ovine pulmonary valve leaflet were investigated under planar-biaxial loading conditions to determine the effects of decellularization and a novel post-decellularization extracellular matrix (ECM) conditioning process. As expected, decellularization resulted in increased stretch along the loading axes. A reduction in relaxation was observed following decellularization. This was accompanied by a reduction in glycosaminoglycan (GAG) content. Based on previous implant studies, these changes may be of little functional consequence in the short term; however, the long term effects of decreased relaxation and GAG content remain unknown. Some restoration of relaxation was observed following ECM conditioning, especially in the circumferential specimen direction, which may help mitigate any detrimental effects due to decellularization. Regardless of processing, creep under biaxial loading was negligible.

Nanoscale patterning of alkyl monolayers on silicon using the atomic force microscope.

Self-assembled monolayers (SAMs) of 1-alkenes on hydrogen-passivated silicon substrates were successfully patterned on the nanometer scale using an atomic force microscope (AFM) probe tip. Nanoshaving experiments on alkyl monolayers formed on H-Si(111) not only demonstrate the flexibility of this technique but also show that patterning with an AFM probe is a viable method for creating well-defined, nanoscale features in a monolayer matrix in a reproducible and controlled manner. Features of varying depths (2-15 nm) were created in the alkyl monolayers by controlling the applied load and the number of etching scans made at high applied loads. The patterning on these SAM films is compared with the patterning of alkyl siloxane monolayers on silicon and mica.