Tunable Thermoelectric Performance of the Nanocomposites Formed by Diketopyrrolopyrrole/Isoindigo-Based Donor–Acceptor Random Conjugated Copolymers and Carbon Nanotubes

This paper presents the development of thermoelectric properties in nanocomposites comprising donor–acceptor random conjugated copolymers and single-walled carbon nanotubes (SWCNTs). The composition of the conjugated polymers, specifically the ratio of diketopyrrolopyrrole (DPP) to isoindigo (IID), is manipulated to design a series of random conjugated copolymers (DPP0, DPP5, DPP10, DPP30, DPP50, DPP90, DPP95, and DPP100). The objective is to improve the dispersion of SWCNTs into smaller bundles, leading to enhanced thermoelectric properties of the polymer/SWCNT nanocomposite. This dispersion strategy promotes an interconnected conducting network, which plays a critical role in optimizing the thermoelectric performance. Accordingly, the effects of morphologies on the thermoelectric properties of the nanocomposites are systematically investigated. The DPP95/SWCNT nanocomposite exhibits the strongest interaction, resulting in the highest power factor (PF) of 711.1 μW m–1 K–2, derived from the high electrical conductivity of 1690 S cm–1 and Seebeck coefficient of 64.8 μV K–1. The prototype flexible thermoelectric generators assembled with a DPP95/SWCNT film achieve a maximum power output of 20.4 μW m–2 at a temperature difference of 29.3 K. These findings highlight the potential of manipulating the composition of random conjugated copolymers and incorporating SWCNTs to efficiently harvest low-grade waste heat in wearable thermoelectric devices

The Epidermal Growth Factor-like Domain of CD93 Is a Potent Angiogenic Factor

<div><p>Human CD93, an epidermal growth factor (EGF)-like domain containing transmembrane protein, is predominantly expressed in the vascular endothelium. Studies have shown that AA4, the homolog of CD93 in mice, may mediate cell migration and angiogenesis in endothelial cells. Soluble CD93 has been detected in the plasma of healthy individuals. However, the role of soluble CD93 in the endothelium remains unclear. Recombinant soluble CD93 proteins with EGF-like domains (rCD93D123, with domains 1, 2, and 3; and rCD93D23, with domains 2 and 3) were generated to determine their functions in angiogenesis. We found that rCD93D23 was more potent than rCD93D123 in stimulating the proliferation and migration of human umbilical vein endothelial cells (HUVECs). Production of matrix-metalloproteinase 2 increased after the HUVECs were treated with rCD93D23. Further, in a tube formation assay, rCD93D23 induced cell differentiation of HUVECs through phosphoinositide 3-kinase/Akt/endothelial nitric oxide synthase and extracellular signal-regulated kinases-1/2 signaling. Moreover, rCD93D23 promoted blood vessel formation in a Matrigel-plug assay and an oxygen-induced retinopathy model <em>in vivo</em>. Our findings suggest that the soluble EGF-like domain containing CD93 protein is a novel angiogenic factor acting on the endothelium.</p> </div

Possible mechanisms of TLR4 in promotion of AAA development.

<p>The schematic diagram shows that TLR4 on VSMCs, possibly in conjugation with RAGE on macrophages, sustains both inflammation and proteolysis in the aortic wall during aneurysm development.</p

TLR4 knockout reduces cytokine production, HMGB1 and RAGE expression and macrophage accumulation preceding AAA formation.

<p>(A) TNF-α, IL-6 and MCP-1 concentration on day 3 by ELISA (n = 6 per group). (B, C) HMGB1 (B) and RAGE (C) levels on day 3 by Western blot (n = 6 per group). (D) Macrophage numbers on day 3, day 7 and day 28 (n = 6 per group). (E) Macrophage immunostaining on day 7 and day 28. (*<i>P</i><0.05, **<i>P</i><0.01, n.s. <i>P</i>>0.05 compared with ScSnJ mice. L indicates lumen. All scale bars represent 50 μm. White arrows indicate examples of MOMA-2-positive, DAPI-stained macrophages.)</p

rCD93D23 induces tube formation through the activation of Akt and ERK in HUVECs on Matrigel <i>in vitro</i>.

<p>(A) rCD93D23 induced tube formation in a dose-dependent manner. (B) The tube formation induced by boiled rCD93D23, and rCD93D23 in the presence of polyclonal anti-CD93D23 IgG (10 µg/ml), U0126 (10 µM), or LY294002 (10 µM). Each value represents the mean ± SD (n = 3), and similar results were obtained in three independent experiments. **, <i>p</i><0.01; ***, <i>p</i><0.001 vs. control. ###, <i>p</i><0.001 vs. rCD93D23.</p

Upregulation of TLR4 during experimental AAA formation in mice.

<p>(A) Aortic diameter change during the 28 days of CaCl₂-induced AAA formation (relative to day 0, n = 6 per group). (B) Time-course of TLR4 expression (relative to the level in normal aorta, n = 4 per group). (C) Representative microscopic photos of double-immunofluorescent staining for TLR4 with α-SMA and for TLR4 with MOMA-2 (a marker for macrophages). (D) VSMC content indicated by intensity of α-SMA staining on day 14 and day 28 (n = 6 per group). (*<i>P</i><0.05, **<i>P</i><0.01, n.s. <i>P</i>>0.05 compared with NaCl-group. Aortic specimens for double-immunofluorescent staining were obtained 14 days after AAA induction. L indicates lumen. All scale bars represent 50 μm.)</p

Effect of rCD93 domain proteins on the chemotactic migration and MMP secretion of HUVECs.

<p>A migration assay was performed in Transwell. (A) HUVECs (1 × 10⁵ cells) suspended in M199 supplemented with 1% FBS were added to the upper wells. The lower wells were filled with different concentrations of rCD93D123 (A) or rCD93D23 (B), or with 10 ng/ml of VEGF. (C) The lower wells were filled with rCD93D23 (30 ng/ml) in the absence or presence of CD93D23 Ab (5 µg/ml), boiled rCD93D23, or 10 ng/ml of VEGF. Each value represents the mean ± SD (n = 3), and similar results were obtained in three independent experiments. *, <i>p</i><0.05; **, <i>p</i><0.01; ***, <i>p</i><0.001 vs. medium alone. ###, <i>p</i><0.001 vs. rCD93D23. (D) The culture media of HUVECs treated with different concentrations of rCD93D23 or VEGF (10 ng/ml) were used in gelatin zymography. The similar results were obtained in three independent experiments. ***, <i>p</i><0.001 vs. medium alone.</p

TLR4-knockout (A, B, C, D) and TLR4-mutant (E, F, G, H) mice are resistant to experimental AAA formation.

<p>(A, E) Aortic diameter on day 0 and day 28 after AAA induction (n = 18 per group in ScSnJ [wild-type controls] versus ScNJ [TLR4-knockout mice], n = 15 per group in HeN [wild-type controls] versus HeJ [TLR4-mutant mice]). (B, F) HMGB1 level by Western blot (n = 4 per group). (C, G) TNF-α, IL-6, MCP-1 concentrations by ELISA (n = 6 per group). (D, H) MMP levels by ELISA (n = 6 per group). (*<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001, n.s. <i>P</i>>0.05 compared with respective controls.)</p

TLR4 mediates cytokine production in HASMCs.

<p>(A) Basal levels of IL-6 and MCP-1 were assessed after being cultured in fresh medium without stimulation for 24 hours (n = 4 per group). (B, C, D) The protein expression of TLR4 in cell lysates (B) and levels of IL-6 (C) and MCP-1 (D) in supernatants were assessed after HMGB1 treatment for 24 hours (n = 4 per group). (E) Levels of IL-6 and MCP-1 were assessed after HMGB1 treatment (100 ng/dl) for 24 hours (n = 4 per group). (*<i>P</i><0.05, **<i>P</i><0.01 compared with untreated or control siRNA group.)</p

rCD93D23 induces HUVEC migration through the activation of Akt and ERK.

<p>(A) rCD93D23 dose-dependently induced FAK, ERK1/2, Akt, and eNOS phosphorylation. HUVECs were treated with different concentrations of rCD93D23 or VEGF (10 ng/ml) for 30 min. (B) rCD93D23 time-dependently induced FAK, ERK1/2, Akt, and eNOS phosphorylation in HUVECs. HUVECs were stimulated with 50 ng/ml of rCD93D23 for various time periods as indicated. The similar results were obtained in three independent experiments. *, <i>p</i><0.05; **, <i>p</i><0.01; ***, <i>p</i><0.001 vs. control (C) HUVEC suspensions were pretreated with LY294002 (10 µM) or U0126 (10 µM). The lower wells were filled with rCD93D23 (30 ng/ml) or VEGF (10 ng/ml). Each value represents the mean ± SD (n = 3), and similar results were obtained in three different experiments. ***, <i>p</i><0.001 vs. control. ###, <i>p</i><0.001 vs. rCD93D23.</p