LC-MS results of MEL-A.

(a), Mass spectra of different homologs isolated from the cultivation medium optimized by LC-MS. The units of CH2 or 2H molecular weight differences which are resulted from the different lengths of fat acid chain and the degree of unsaturation present in these compounds. (b), Loss of the erythritol, fatty acids and acetic acid was shown in the MS2 spectra.</p

Effects of MEL-A on cell cycle distributions of B16 cells.

<p>Cells were treated with different concentrations of MEL-A for 24 h. (a) ~ (e) refer to the cell cycle distributions of B16 cells treated by 0, 9.0, 15.0, 20.0, 25.0 μg/mL MEL-A, respectively. G1/G0, S, G2/M and Sub-G1 indicate the different cell phases. Mean ± SD, n = 3. The results in (f) summarized the relative ratios of each cell cycle, indicating that MEL-A caused cell cycle arrest at the S phase. The cell population of Sub-G1 phase was slightly increased with exposure to above 15.0 μg/mL of MEL-A.</p

Detected MEL-A homologs with various masses and fatty acids chain combinations.

<p>Detected MEL-A homologs with various masses and fatty acids chain combinations.</p

The solution state of MEL-A in water.

<p>(a), mean particle sizes of MEL-A solution at the concentrations of 12.0 mg/L. (b), mean particle sizes of MEL-A solution at the concentrations of 12.0 μg/L. (c), the surface tension of MEL-A changed with various concentrations. The concentration at the curve break records the critical micelle concentration (CMC).</p

Effects of MEL-A on the protein expression and mRNA expression in B16 cells.

(A) and (B), protein expression analysis of Caspase-3, cleaved Caspase-3, Caspase-12, Bcl-2, CHOP and GRP78 in the B16 cells treated with 15.0 μg/mL MEL-A for 24 h. The untreated cells were used as control. (C) and (D), fold changes of IRE1 and ATF6 protein expression. (E), mRNA expression analysis of Bcl-2, Caspase-3, CHOP, GRP78 and Caspase-12 in the B16 cells treated with 15.0 μg/mL MEL-A for 24 h. The untreated cells were used as control. Mean ± SD, n = 3.</p

¹H NMR spectrum and ¹³C NMR spectrum of MEL-A.

<p>(a), ¹H signals at 0~7.0 ppm and (b), ¹³C signals at 0~180.0 ppm. (c), Structure of MELs, MEL-A: R₁ = R₂ = Ac; MEL-B: R₁ = Ac, R₂ = H; MEL-C: R₁ = H, R₂ = Ac; MEL-D: R₁ = R₂ = H, n = 6–16.</p

Effects of MEL-A on apoptosis of B16 cells.

<p>Cells were treated with different concentrations of MEL-A for 24 h. (a) ~ (f) refer to the cell population changes of B16 treated by 0, 6.0, 9.0, 12.0, 15.0, 25.0 μg/mL MEL-A, respectively. Most MEL-A-induced cells were evident in B2 fraction, and the tendency of the induced cells apoptosis was in a dose-dependent manner. Mean ± SD, n = 3.</p

The viabilities of B16 cells and NIH3T3 cells in response to MEL-A treatments.

<p>(a), B16 cells treated with increasing doses of MEL-A had obvious changes. (b), the viability of the normal NIH3T3 cells treated by 15.0 μg/mL MEL-A for 72 h. (c, d, e, f) refers to the photographs of untreated B16 cells, and cells treated with MEL-A for 24 h, 48 h and 72 h. (g, h, m, n) refers to the photographs of untreated NIH3T3 cells and cells treated with MEL-A for 24 h, 48 h, and 72 h, respectively.</p

Micelle-Cross-Linked Hydrogels with Strain Stiffening Properties Regulated by Intramicellar Cross-Linking

Micelle-cross-linked hydrogels are promising candidates for tough hydrogels with a tailorable chemical composition, nanostructure, mechanical properties, and functionality. In this article, intramicellar cross-linking was demonstrated to be a facile strategy for achieving micelle-cross-linked hydrogels with an adaptive strain stiffening property and decoupled fracture stress and Young’s modulus. Core-cross-linked micelles with tunable intramicellar cross-linking density and tailorable chemical composition were synthesized by polymerization-induced self-assembly at a high concentration and were used as the macro-cross-linkers for tough polyacrylamide hydrogels. With the increase in the intramicellar cross-linking, these hydrogels exhibited increasing fracture stress and almost consistent Young’s modulus, enabling a decoupled regulation of the fracture stress and modulus. Mooney–Rivlin analyses suggested the enhanced strain stiffening with the intramicellar cross-linking originating from the increasing permanent cross-links, which was confirmed by the relaxation and cyclic tensile tests. The structure–performance correlation was further verified by two additional core-cross-linked micelles with varying chemical compositions. Based on the structure–performance correlation, a photoresponsive micelle-cross-linked hydrogel was designed by using coumarin groups as the photoswitch for the regulation of the intramicellar cross-linking density. Taking advantage of the photoswitched dimerization/cleavage of coumarin, a photomodulated strain stiffening property and the decoupled regulation of the fracture stress and modulus were achieved. This work has provided new insights into the design of tough hydrogels with adaptive mechanical properties

Polymerization-Induced Self-Assembly Toward Micelle-Crosslinked Tough and Ultrastretchable Hydrogels

As a promising class of tough and ultrastretchable hydrogels, micelle-crosslinked hydrogels have been restrained by the scarcity of micellar crosslinkers with a high concentration, controlled nanostructure, and uniform size distribution. Herein, polymerization-induced self-assembly (PISA) was demonstrated to be a general and powerful platform for micellar crosslinkers, affording micelle-crosslinked hydrogels with tailorable chemical structures, mechanics, and functionality. Poly­(N,N-dimethylacrylamide)-b-poly­(diacetone acrylamide) (PDMAc-b-PDAAM) micellar crosslinkers with a controlled nanostructure and uniform size distribution were prepared via PISA and one-step post-polymerization modification at high concentrations. Copolymerization of these micellar crosslinkers with acrylamide generated tough and ultrastretchable hydrogels, whose mechanical properties were found correlated with the concentration, nanostructure, and chemical composition of the micelles. The energy dissipation mechanism of these micelle-crosslinked hydrogels was analyzed via cyclic mechanical tests and stress relaxation experiments. The general feasibility of PISA toward micelle-crosslinked hydrogels was verified by systematic evaluation of both aqueous (including 2-methoxyethyl acrylate, tetrahydro-2-furanylmethyl acrylate, and 4-hydroxybutyl acrylate) and alcoholic (including benzyl methacrylate, lauryl methacrylate, styrene, and benzyl acrylate) PISA formulations, producing hydrogels with diverse chemical structures, mechanics, and functionalities depending on the micellar crosslinkers. The modularity of this strategy was further demonstrated by the fabrication of fluoro-functionalized hydrogels with fluoro-containing micellar crosslinkers. This strategy has significantly enlarged the scope and application of micelle-crosslinked hydrogels