Marianne Prévôt, Leah Bergquist, Anshul Sharma, Taizo Mori, Yungxiang Gao, Tanmay Bera, Chenhui Zhu, Michelle Leslie, Richard Cukelj, LaShanda T. J. Korley, Ernest Freeman, Jennifer McDonough, Robert Clements, Elda Hegmann
We report here on cell growth and proliferation within a 3D architecture created using smectic liquid crystal elastomers (LCEs) leading to a responsive scaffold for tissue engineering. The investigated LCE scaffolds exhibit biocompatibility, controlled degradability, with mechanical properties and morphologies that can match development of the extracellular matrix. Moreover, the synthetic pathway and scaffold design offer a versatility of processing, allowing modifications of the surface such as adjusting the hydrophilic/hydrophobic balance and the mobility of the LC moieties to enhance the biomaterial performance. First, we succeeded in generating LCEs whose mechanical properties mimic muscle tissue. In films, our LCEs showed cell adhesion, proliferation, and alignment. We also achieved creating 3D LCE structures using either metallic template or microsphere scaffolds. Finally, we recorded a four times higher cell proliferation capability in comparison to conventional porous films and, most importantly, anisotropic cell growth that highlights the tremendous effect of liquid crystal moieties within LCEs on the cell environment.
Studies of chiroptical effects of chiral ligand-capped gold nanoparticles (Au NPs) are a fascinating and rapidly evolving field in nanomaterial research with promising applications of such chiral metal NPs in catalysis and metamaterials as well as chiral sensing and separation. The aim of our studies was to seek out a system that not only allows the detection and understanding of Au NP chirality but also permits visualization and ranking — considering size, shape and nature as well as density of the ligand shell — of the extent of chirality transfer to a surrounding medium. Nematic liquid crystal (N-LC) phases are an ideal platform to examine these effects, exhibiting characteristic defect textures upon doping with a chiral additive. To test this, we synthesized series of Au NPs capped with two structurally different chiral ligands and studied well-dispersed mixtures in two nematic liquid crystal hosts. Induced circular dichroism (ICD) spectropolarimetry and polarized light optical microscopy (POM) confirmed that all Au NPs induce chiral nematic (N*-LC) phases, and measurements of the helical pitch as well as calculation of the helical twisting power (HTP) in various cell geometries allowed for an insightful ranking of the efficiency of chirality transfer of all Au NPs as well as their free ligands.
We here report on the alignment and electro-optic properties of nematic liquid crystals (LCs) either containing nanoscale
particles as additives or featuring particles patterned on substrates. The investigated nematic LCs or LC dispersions are
doped or in contact with magic-sized semiconductor CdSe nanocrystals (MSNCs) or silane- and alkylthiol monolayercapped
gold nanoparticles. Three single-sized CdSe quantum dots capped with myristic acid exhibiting bright bandgap
photoluminescence (PL) at λmax ~ 463 nm were tested as additives. Two of the quantum dots only vary in the amount of
defects as indicated by different bandgap and deep trap PL. The third MSNC sample is compositionally different, doped
with Zn. These MSNCs with almost identical sizes were doped at different concentrations (1-5 wt%) into the nematic
phase of the 2-phenylpyrimidine-based LC1. Only the Zn-doped MSNCs showed the formation of birefringent stripes
surrounded by areas of homeotropic alignment between plain glass slides at all concentrations as observed for many
other nanoparticle-doped nematic LCs reported earlier by our group. In polyimide-coated glass slides favoring planar
orientation of the nematic director, planar alignment was observed. Similarly, siloxane-coated gold nanoparticle
additives with narrow size distribution, but larger size, show homeotropic alignment between plain glass and planar
alignment in rubbed polyimide-coated cells. Surprisingly then, we succeeded in creating alignment patterns using
smaller, ~2 nm alkylthiol-capped gold nanoparticles using a process called stenciling that allowed us to generate patterns
of homeotropic alignment in a continuum of planar alignment of the nematic LC. Finally, electro-optic investigations on
some of these samples revealed that only the Zn-doped magic-sized MSNCs significantly lower the dielectric anisotropy
as well as the splay elastic constant of the nematic host, despite identical size and surface functionality of the three used
MSNCs, which highlights the tremendous effect of the nanocrystal core composition on the electro-optic properties of
the nematic host.
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