Gradient patterns comprising bioactive compounds over comparably (in regard to a cell size) large areas are key for many applications in the biomedical sector, in particular, for cell screening assays, guidance, and migration experiments. Polymer pen lithography (PPL) as an inherent highly parallel and large area technique has a great potential to serve in the fabrication of such patterns. We present strategies for the printing of functional phospholipid patterns via PPL that provide tunable feature size and feature density gradients over surface areas of several square millimeters. By controlling the printing parameters, two transfer modes can be achieved. Each of these modes leads to different feature morphologies. By increasing the force applied to the elastomeric pens, which increases the tip-surface contact area and boosts the ink delivery rate, a switch between a dip-pen nanolithography (DPN) and a microcontact printing (μCP) transfer mode can be induced. A careful inking procedure ensuring a homogeneous and not-too-high ink-load on the PPL stamp ensures a membrane-spreading dominated transfer mode, which, used in combination with smooth and hydrophilic substrates, generates features with constant height, independently of the applied force of the pens. Ultimately, this allows us to obtain a gradient of feature sizes over a mm substrate, all having the same height on the order of that of a biological cellular membrane. These strategies allow the construction of membrane structures by direct transfer of the lipid mixture to the substrate, without requiring previous substrate functionalization, in contrast to other molecular inks, where structure is directly determined by the printing process itself. The patterns are demonstrated to be viable for subsequent protein binding, therefore adding to a flexible feature library when gradients of protein presentation are desired.
Nux MT and Nux 30c could reduce ethanol intake in rats. The altered solution structure of Nux 30c is thought to mimic Nux MT and produce ethanol aversion in rats.
Fascicular
rearrangement of an injured peripheral nerve requires
reconnection of nerve sprouts from anterior and Büngner bands
from distal sides of the lesion, failing to which leads to inefficient
regeneration of the injured nerve. However, existing neural scaffolds
have limited neuroregeneration efficiency because of either the lack
of alignment of fibers and a conductive second phase, leading to compromised
electrical conductivity, or the lack of extracellular matrix components
and in vivo validation. The present study reports
a biocompatible, multiwall carbon nanotube (MWCNT)-reinforced, anisotropically
conductive, electrospun, aligned nanofibrous scaffold, ensuring maximal
peripheral nerve regeneration. Electrospinning parameters were modulated
to deposit random and parallel fibers in separate scaffolds for comparative
analysis on the effect of fiber alignment on regeneration. Both types
of scaffolds were reinforced with MWCNTs to impart electrical conductivity.
Nonreinforced scaffolds were nonconductive. In this comparative study,
MWCNT-reinforced, aligned scaffolds showed better tensile property
with increased conductivity along the direction of alignment, thereby
ensuring an escalated neural-regeneration rate. Collectively, in vitro studies established the scaffolds to be highly
biocompatible, promoting cell growth and proliferation. With 85% more
anisotropic conductivity in the direction of the alignment and the
degradation kinetics tuned to the regeneration regime, the MWCNT-reinforced,
aligned scaffold efficiently healed injured sciatic nerves in rats
within 30 days. Rigorous revivification of the tissue was due to coordinated
Wallerian degeneration and expedited guided axonal regeneration. Structural
and functional analysis of nerves in vivo showed
the aligned, MWCNT-reinforced scaffold to be very efficient in peripheral
sciatic nerve regeneration. This study notes the efficacy of the coaxially
aligned, MWCNT-reinforced neural scaffold, with a capability of establishing
remarkable advancement in the field of peripheral neural regeneration.
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