In this work, the fabrication and in vitro degradation of porous fumarate-based/alumoxane nanocomposites were evaluated for their potential as bone tissue engineering scaffolds. The biodegradable polymer poly (propylene fumarate)/propylene fumarate-diacrylate (PPF/PF-DA), a macrocomposite composed of PPF/PF-DA and boehmite microparticles, and a nanocomposite composed of PPF/PF-DA and surface-modified alumoxane nanoparticles were used to fabricate porous scaffolds by photo-crosslinking and salt-leaching. Scaffolds then underwent 12 weeks of in vitro degradation in phosphate buffered saline at 37 degrees C. The presence of boehmite microparticles and alumoxane nanoparticles in the polymer inhibited scaffold shrinkage during crosslinking. Furthermore, the incorporation of alumoxane nanoparticles into the polymer limited salt-leaching, perhaps due to tighter crosslinking within the nanocomposite. Analysis of crosslinking revealed that the acrylate and overall double bond conversions in the nanocomposite were higher than in the PPF/PF-DA polymer alone, though these differences were not significant. During 12 weeks of in vitro degradation, the nanocomposite lost 5.3% +/- 2.4% of its mass but maintained its compressive mechanical properties and porous architecture. The addition of alumoxane nanoparticles into the fumarate-based polymer did not significantly affect the degradation of the nanocomposite compared with the other materials in terms of mass loss, compressive properties, and porous structure. These results demonstrate the feasibility of fabricating degradable nanocomposite scaffolds for bone tissue engineering by photo-crosslinking and salt-leaching mixtures of fumarate-based polymers, alumoxane nanoparticles, and salt microparticles.
The amygdaloid complex located within the medial temporal lobe plays an important role in the acquisition and expression of learned fear associations (Quirk et al. 2003) and contains three main components: the lateral nucleus (LA), the basal nucleus (BLA), and the central nucleus (CE) (Faber and Sah, 2002). The lateral nucleus of the amygdala (LA) is widely accepted to be a key site of plastic synaptic events that contributes to fear learning (Pare, Quirk, LeDoux, 2004). There are two main types of neurons within the LA and the BLA: principal pyramidal-like cells which form projection neurons and are glutamatergic and local circuit GABAergic interneurons (Faber and Sah, 2002). In auditory fear conditioning, convergence of tone [conditioned stimulus (CS)] and foot-shock [unconditioned stimulus (US)] inputs potentiates the synaptic transmission containing CS information from the thalamus and cortex to LA, which leads to larger responses in LA in the presentation of subsequent tones only. The increasing LA responses disinhibit the CE neurons via the intercalated (ITC) cells, eliciting fear responses via excessive projections to brain stem and hypothalamic sites (Pare, Quirk, LeDoux, 2004). As a result, rats learn to freeze to a tone that predicts a foot-shock. Once acquired, conditioned fear associations are not always expressed and repeated presentation of the tone CS in the absence of US causes conditioned fear responses to rapidly diminish, a phenomenon termed fear extinction (Quirk et al. 2003). Extinction does not erase the CS-US association, instead it forms a new memory that inhibits conditioned response (Quirk et al. 2003)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.