Fabrication
of a surface-engineered electrospun scaffold having biomimetic properties
like the extracellular matrix (ECM) is essential for neural tissue
engineering. An electroconductive and elastomeric scaffold with aligned
fibers acting as a substrate may have a great impact on the directional
outgrowth of neurites. In this study, we have electrospun electrically
conductive, polyurethane-based elastomeric and topographically aligned
fibro-porous neural scaffolds. Adhesive proteins of the ECM are documented
to have an important role in controlling neuronal cell behavior, including
cell adhesion, proliferation, and neurite outgrowth. These bio-adhesion
proteins or nanomaterials mimicking their action, if used for surface
modification of neural scaffolds, may have the potential to accelerate
the nerve repair process. Thus, electrospun scaffolds fabricated were
surface-engineered using a unique and modified single-step electrospraying
technique to coat the scaffold surface with an exploratory bio-adhesion
agent, a thin layer of graphene oxide (GO) films. The study was then
carried out to determine if the GO-coated electrospun electroconductive
polycarbonate urethane (PCU) substrate can improve the bio-interface
attributes of these scaffolds or may alter the neurite outgrowth of
PC-12 cells like any other bio-adhesion proteins. Therefore, the hybrid
scaffolds with GO coatings were compared with similar scaffolds coated
with poly-l-lysine (PLL) for neural cell adhesion, proliferation,
and neurite extension. Neurite outgrowth studies showed that although
the average neurite length was comparable on both GO- and PLL-coated
surfaces, the length profile of neurites, when categorized based on
length, showed an increased number of lengthier neurites on the GO-coated
hybrid scaffolds. In particular, the study brings out an innovative
surface engineering technique for the coating of GO on polymeric scaffolds.
It may be further put together in designing of hybrid surfaces with
nanotopographical biophysical cues on three-dimensional neural scaffolds,
which in turn may stimulate an accelerated neuronal regeneration via
providing an enhanced ECM like milieu.
Encoding and consolidating information through learning and memory is vital in adaptation and survival. Dopamine (DA) is a critical neurotransmitter that modulates behavior. However, the role of DA in learning and memory processes is not well defined.Herein, we used the olfactory adaptive learning paradigm in Caenorhabditis elegans to elucidate the role of DA in the memory pathway. Cat-2 mutant worms with low DA synthesis showed a significant reduction in chemotaxis index (CI) compared to the wild type (WT) after short-term conditioning. In dat-1::ICE worms, having degeneration of DA neurons, there was a significant reduction in adaptive learning and memory. When the worms were trained in the presence of exogenous DA (10 mM) instead of food, a substantial increase in CI value was observed. Furthermore, our results suggest that both dop-1 and dop-3 DA receptors are involved in memory retention. The release of DA during conditioning is essential to initiate the learning pathway. We also noted an enhanced cholinergic receptor activity in the absence of dopaminergic neurons. The strains expressing GCaMP6 in DA neurons (pdat-1::GCaMP-6::mCherry) showed a rise in intracellular calcium influx in the presence of the conditional stimulus after training, suggesting DA neurons are activated during memory recall. These results reveal the critical role of DA in adaptive learning and memory, indicating that DA neurons play a crucial role in the effective processing of cognitive function.
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