In situ vascular tissue engineering has been proposed as a promising approach to fulfill the need for small-diameter blood vessel substitutes. The approach comprises the use of a cell-free instructive scaffold to guide and control cell recruitment, differentiation, and tissue formation at the locus of implantation. Here we review the design parameters for such scaffolds, with special emphasis on differentiation of recruited ECFCs into the different lineages that constitute the vessel wall. Next to defining the target properties of the vessel, we concentrate on the target cell source, the ECFCs, and on the environmental control of the fate of these cells within the scaffold. The prospects of the approach are discussed in the light of current technical and biological hurdles.
Silicon (Si) and
composites thereof, preferably with carbon (C),
show favorable lithium (Li) storage properties at low potential, and
thus hold promise for application as anode active materials in the
energy storage area. However, the high theoretical specific capacity
of Si afforded by the alloying reaction with Li involves many challenges.
In this article, we report the preparation of small-size Si particles
with a turbostratic carbon shell from a polymer precoated powder material.
Galvanostatic charge/discharge experiments conducted on electrodes
with practical loadings resulted in much improved capacity retention
and kinetics for the Si/C composite particles compared to physical
mixtures of pristine Si particles and carbon black, emphasizing the
positive effect that the core–shell-type morphology has on
the cycling performance. Using in situ differential electrochemical
mass spectrometry, pressure, and acoustic emission measurements, we
gain insights into the gassing behavior, the bulk volume expansion,
and the mechanical degradation of the Si/C composite-containing electrodes.
Taken together, our research data demonstrate that some of the problems
of high-content Si anodes can be mitigated by carbon coating. Nonetheless,
continuous electrolyte decomposition, particle fracture, and electrode
restructuring due to the large volume changes during battery operation
(here, ∼170% in the voltage range of 600–30 mV vs Li
+
/Li) remain as serious hurdles toward practical implementation.
In
the past decade, significant progress has been made in the field
of biomaterials, for potential applications in tissue engineering
or drug delivery. We have recently developed a new class of thermoplastic
elastomers, based on ureidopyrimidinone (UPy) quadruple hydrogen bonding
motifs. These supramolecular polymers form nanofiber-like aggregates
initially via the dimerization of the UPy units followed
by lateral urea-hydrogen bonding. Combined kinetic and thermodynamic
studies unravel the pathway complexity in the formation of these polymorphic
nanofibers and the subtlety of the polymer’s design, while
these morphologies are so critically important when these materials
are used in combination with cells. We also show that the cell behavior
directly depends on the length and shape of the nanofibers, illustrating
the key importance of macromolecular and supramolecular organization
of biomaterials. This study leads to new design rules that determine
what factors are decisive for a polymer to be a good candidate as
biomaterial.
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