Regulating cell behavior via regional patterned distribution of heparin-like polymers

Molecular patterning on biomaterial surfaces is an effective strategy to regulate biomaterial properties. Among the specific molecules, due to their biological functions, such as regulating cell behavior, heparin-like polymers (HLPs) have attracted much attention. In this study, HLP-distributed regional patterned surfaces (300 μm diameter circular array) were prepared by the combination of visible light-induced graft polymerization, transfer imprinting, and self-assembly to regulate the behavior of human umbilical vein endothelial cells (HUVECs) and human umbilical vein smooth muscle cells (HUVSMCs). The introduction of the regional pattern on HLP-modified surfaces enhanced the promotion effect of sulfonate-containing polymer (pSS) and sulfonate-, and glyco-containing copolymer (pS-co-pM), and slightly weakened the inhibition effect of glyco-containing polymer (pMAG) on the growth of HUVECs and HUVSMCs. Compared with flat surfaces, it was found that the unmodified regional patterned surfaces inhibit the spreading of HUVECs and HUVSMCs, while significantly promoting the spreading of HUVECs and HUVSMCs on all the HLP-distributed regional patterned surfaces. The patterned surface modified with pS-co-pM had the highest average spread area of HUVECs (∼10,554 μm2), which was 193 % higher than that of the unmodified flat surface. This trend was somewhat related to surface VEGF adsorption. The combination of regional divisive patterns and different HLP distributions enriched the potential of further exploring the influences of HLP chemical distributions and complex surface environments on cell-material interactions.

Evolving community structure in the international pesticide trade networks

The statistical properties of the international trade networks of all commodities as a whole have been extensively studied. However, the international trade networks of individual commodities often behave differently. Due to the importance of pesticides in agricultural production and food security, we investigated the evolving community structure in the international pesticide trade networks (iPTNs) of five categories from 2007 to 2018. We reveal that the community structures in the undirected and directed iPTNs exhibit regional patterns. However, the regional patterns are very different for undirected and directed networks and for different categories of pesticides. Moreover, the community structure is more stable in the directed iPTNs than in the undirected iPTNs. We also extract the intrinsic community blocks for the directed international trade networks of each pesticide category. It is found that the largest intrinsic community block is the most stable, appears in every pesticide category, and contains important economies (Belgium, Germany, Spain, France, the United Kingdom, Italy, the Netherlands, and Portugal) in Europe. Other important and stable intrinsic community blocks are Canada and the United States in North America, Argentina and Brazil in South America, and Australia and New Zealand in Oceania. These results suggest that, in the international trade of pesticides, geographic distance and the complementarity of important and adjacent economies are significant factors.