Tuning the Mechanical Properties of Poly(Ethylene Glycol) Microgel‐Based Scaffolds to Increase 3D Schwann Cell Proliferation

2D in vitro studies have demonstrated that Schwann cells prefer scaffolds with mechanical modulus approximately 10× higher than the modulus preferred by nerves, limiting the ability of many scaffolds to promote both neuron extension and Schwann cell proliferation. Therefore, the goals of this work are to develop and characterize microgel‐based scaffolds that are tuned over the stiffness range relevant to neural tissue engineering and investigate Schwann cell morphology, viability, and proliferation within 3D scaffolds. Using thiol‐ene reaction, microgels with surface thiols are produced and crosslinked into hydrogels using a multiarm vinylsulfone (VS). By varying the concentration of VS, scaffold stiffness ranges from 0.13 to 0.76 kPa. Cell morphology in all groups demonstrates that cells are able to spread and interact with the scaffold through day 5. Although the viability in all groups is high, proliferation of Schwann cells within the scaffold of G* = 0.53 kPa is significantly higher than other groups. This result is ≈5× lower than previously reported optimal stiffnesses on 2D surfaces, demonstrating the need for correlation of 3D cell response to mechanical modulus. As proliferation is the first step in Schwann cell integration into peripheral nerve conduits, these scaffolds demonstrate that the stiffness is a critical parameter to optimizing the regenerative process.

     

New synthetic pathways into dithiazolyl radicals: Preparation and characterisation of 3′-methyl-benzo-1,3,2-dithiazolyl, M’BDTA

A general three-step synthesis to a range of benzo-fused-1,3,2-dithiazolylium salts bearing both electron-withdrawing (CN) and electron-donating (Me) groups is described. This methodology has also been extended to pyridyl derivatives and offers a potential route to a diversity of 1,3,2-dithiazolylium rings and their corresponding 1,3,2-dithiazolyl free radicals. The key steps in the reaction are treatment of a substituted 1,2,-dichlorobenzene with two equivalents of [^tBuS]Na, followed by chlorination to yield the corresponding bis(sulfenyl chloride). Subsequent ring closure with Me₃SiN₃ yields the target 1,3,2-dithiazolylium ring system in good yield. The preparation and crystal structures of 3′-methyl-benzo-1,3,2-dithiazolylium chloride and 3′-methyl-benzo-1,3,2-dithiazolyl are described and the electronic properties of the radical examined through EPR spectroscopy, DFT calculations and variable temperature magnetic susceptibility measurements.     

Beta-amino acid-containing hybrid peptides--new opportunities in peptidomimetics

Hybrid peptides consisting of alpha-amino acids with judiciously placed beta-amino acids show great promise as peptidomimetics in an increasing range of therapeutic applications. This reflects a combination of increased stability, high specificity and relative ease of synthesis.     

1,2,3-triazolate-bridged tetradecametallic transition metal clusters [M14(L)6O6(OMe)18X6] (M=FeIII, CrIII and VIII/IV) and related compounds: ground-state spins ranging from S=0 to S=25 and spin-enhanced magnetocaloric effect

We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe)18Cl6] (M=FeIII, CrIII) and [V14(L)6O6(OMe)18Cl6-xOx] (L=anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M14} complexes [Fe14(C2H2N3)6O6(OMe)18Cl6], [Cr14(bta)6O6(OMe)18Cl6] (btaH=benzotriazole), [V14O6(Me2bta)6(OMe)18Cl6-xOx] [Me2btaH=5,6-Me2-benzotriazole; eight metal sites are VIII, the remainder are disordered between {VIII-Cl}2+ and {VIV=O}2+] and for the distorted [FeIII14O9(OH)(OMe)8(bta)7(MeOH)5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronic spins of S相似文献   

Conducting polymer diffraction gratings on gold surfaces created by microcontact printing and electropolymerization at submicron length scales

Conducting polymer diffraction gratings on Au substrates have been created using microcontact printing of C18-alkanethiols, followed by electropolymerization of either poly(aniline) (PANI) or poly(3,4-ethylenedioxythiophene) (PEDOT). Soft-polymer replicas of simple diffraction grating masters (1200 lines/mm) were used to define the alkanethiol template for polymer growth. Growth of PANI and PEDOT diffraction gratings was followed in real time, through in situ tapping-mode atomic force microscopy, and by monitoring diffraction efficiency (DE) as a function of grating depth. DE increased as grating depth increased, up to a limiting efficiency (13-26%, with white light illumination), defined by the combined optical properties of the grating and the Au substrate, and ultimately limited by the loss of resolution due to coalescence of the polymer films. Grating efficiency is strongly dependent upon the grating depth and the refractive index contrast between the grating material and the surrounding solutions. Both PEDOT and PANI gratings show refractive index changes as a function of applied potential, consistent with changes in refractive index brought about by the doping/dedoping of the conducting polymer. The DE of PANI gratings are strongly dependent on the pH of the superstrate solution; the maximum sensitivity (DeltaDE/DeltapH) is achieved with PANI gratings held at +0.4 V versus Ag/AgCl, where the redox chemistry is dominated by the acid-base equilibrium between the protonated (emeraldine salt) and deprotonated (emeraldine base) forms of PANI. Simulations of DE were conducted for various combinations of conducting polymer refractive index and grating depth, to compute sensitivity parameters, which are maximized when the grating depth is ca. 50% of its maximum obtainable depth.     

Preparation of 4-hydroxy-3-substituted, 2H-1-benzopyran-2-ones and 2H-1-benzothiopyran-2-ones from carboxylic esters and methyl salicylates or methyl thiosalicylate

C(α)-Carboxylic acid esters were treated with excess lithium diisopropylamide, condensed with methyl salicylates or methyl thiosalicylate, followed by acid cyclization to either 4-hydroxy-3-substituted, 2H-1-benzopyran-2-ones (coumarins), or 2H-1-benzothiopyran-2-ones (thiocoumarins).     

Multimodal Interfaces for Cell Phones and Mobile Technology

By modeling users' natural spoken and multimodal communication patterns, more powerful and highly reliable interfaces can be designed that support emerging mobile technology. In this paper, we highlight three different examples of research that is advancing state-of-the-art mobile technology. The first is the development of fusion-based multimodal systems, such as ones that combine speech and pen or touch input, which are substantially improving the robustness and stability of system recognition. The second is modeling of multimodal communication patterns to establish open-microphone engagement techniques that work in challenging multi-person mobile settings. The third is new approaches to adaptive processing, which are able to transparently guide user input to match system processing capabilities. All three research directions are contributing to the design of more reliable, usable, and commercially promising mobile systems of the future.