Rapid and Facile Light-Based Approach to Fabricate Protease-Degradable Poly(ethylene glycol)-norbornene Microgels for Cell Encapsulation.

Thiol-norbornene photoclickable poly (ethylene glycol) (PEG)-based (PEG-NB) hydrogels are attractive biomaterials for cell encapsulation, drug delivery, and regenerative medicine applications. Although many crosslinking strategies and chemistries have been developed for PEG-NB bulk hydrogels, fabrication approaches of PEG-NB microgels have not been extensively explored. Here, a fabrication strategy for 4-arm amide-linked PEG-NB (PEG-4aNB) microgels using flow-focusing microfluidics for human mesenchymal stem/stromal cell (hMSCs) encapsulation is presented. PEG-4aNB photochemistry allows high-throughput, ultrafast generation, and cost-effective synthesis of monodispersed microgels (diameter 340 ± 18, 380 ± 24, and 420 ± 15 µm, for 6, 8, and 10 wt% of PEG-4aNB, respectively) using an in situ crosslinking methodology in a microfluidic device. PEG-4aNB microgels show in vitro degradability due to the incorporation of a protease-degradable peptide during photocrosslinking and encapsulated cells show excellent viability and metabolic activity for at least 13 days of culture. Furthermore, the secretory profile (i.e., MMP-13, ICAM-1, PD-L1, CXCL9, CCL3/MIP-1, IL-6, IL-12, IL-17E, TNF-α, CCL2/MCP-1) of encapsulated hMSCs shows increased expression in response to IFN-γ stimulation. Collectively, this work shows a versatile and facile approach for the fabrication of protease-degradable PEG-4aNB microgels for cell encapsulation.

Key Features of Polyimide-Derived Carbon Molecular Sieves.

Carbon molecular sieve (CMS) membranes have impressive separation properties; however, both chemical and morphology structures need to be understood better. Here we characterize CMS with the simplest polyimide (PI) PMDA/pPDA (PMDA=pyromellitic dianhydride, pPDA=p-phenylenediamine), using FTIR, solid-state 15 N-NMR and 13 C-NMR, XPS, XRD, and Raman spectra to study chemical structure. We also compare gas separation properties for this CMS to a CMS derived from a more conventional PI precursor. The detailed characterization shows the presence of aromatic pyridinic, pyrrolic rings as well as graphitic, pyridonic components and a few other groups in both CMS types derived from the very different precursors. The CMS morphologies, while related to precursor and pyrolysis temperature details, show similarities consistent with a physical picture comprising distributed molecular sieving plate-like structures. These results assist in understanding diverse CMS membrane separation performance.

In-Plane Cation Ordering and Sodium Displacements in Layered Honeycomb Oxides with Tetravalent Lanthanides: Na2LnO3 (Ln = Ce, Pr, and Tb).

The detailed structural characterization of "213" honeycomb systems is a key concern in a wide range of fundamental areas, such as frustrated magnetism, and technical applications, such as cathode materials, catalysts, and thermoelectric materials. Na2LnO3 (Ln = Ce, Pr, and Tb) are an intriguing series of "213" honeycomb systems because they host tetravalent lanthanides. "213" honeycomb materials have been reported to adopt either a cation-disordered R3̅m subcell, a cation-ordered trigonal (P3112), or monoclinic (C2/c or C2/m) supercell. On the basis of analysis of the average (synchrotron diffraction) and local [pair distribution function (PDF) and solid-state NMR] structure probes, cation ordering in the honeycomb layer of Na2LnO3 materials has been confirmed. Through rationalization of the 23Na chemical shifts and quadrupolar coupling constants, the local environment of Na atoms was probed with no observed evidence of cation disorder. Through these studies, it is shown that the Na2LnO3 materials adopt a C2/c supercell derived from symmetry-breaking displacements of intralayered Na atoms from the ideal crystallographic position (in C2/m). The Na displacement is validated using distortion index parameters from diffraction data and atomic displacement parameters from PDF data. The C2/c supercell is faulted, as evidenced by the increased breadth of the superstructure diffraction peaks. DIFFaX simulations and structural considerations with a two-phase approach were employed to derive a suitable faulting model.