Order-Order Transition in Statistical Copolymer Thin Film Induced by LCST-Type Behavior.

In this paper, we describe the formation of an ordered structure in a copolymer thin film through hydration, which subsequently transitions to a different ordered structure upon dehydration. A statistical copolymer of poly(N-octadecyl acrylamide-stat-hydroxymethyl acrylamide) with a comonomer content ratio of 1:1, denoted as p(ODA50/HEAm50), was synthesized via free radical copolymerization. We prepared a thin film of this copolymer on a solid substrate and annealed it at 60 °C under humid conditions. This treatment formed a side-chain segregated lamellar (SCSegL) structure, in which the ODA and HEAm units are oriented perpendicularly to the polymer backbone and opposite each other. Increasing the annealing temperature to 90 °C led to a transition to a side-chain mixed lamellar (SCMixL) structure, where the ODA and HEAm units are also oriented perpendicularly to the polymer backbone but in both directions. The quartz crystal microbalance (QCM) data indicate that p(ODA50/HEAm50) exhibits LCST-like behavior with a transition temperature of approximately 50 °C. We conclude that the formation of the SCSegL structure at 60 °C is due to pronounced segregation between the water-adsorbed HEAm groups and the hydrophobic ODA. Conversely, dehydration at 90 °C reduces the segregation forces, forming the SCMixL structure, which exhibits lower strain. These results demonstrate that the p(ODA50/HEAm50) film undergoes an order-to-order transition driven by the hydration-dehydration process. Additionally, we found that changes in the lamellar structure significantly alter the swelling properties of the film.

The hybrid CL-SP-D molecule has the potential to regulate xenogeneic rejection by human neutrophils more efficiently than CD47.

OBJECTIVE: Innate immunity plays a vital role in xenotransplantation. A CD47 molecule, binding to the SIRPα expressed on monocyte/macrophage cells, can suppress cytotoxicity. Particularly, the SIRPα contains ITIM, which delivers a negative signal. Our previous study demonstrated that the binding between CL-P1 and surfactant protein-D hybrid (CL-SP-D) with SIRPα regulates macrophages' phagocytic activity. In this study, we examined the effects of human CD47 and CL-SP-D expression on the inhibition of xenograft rejection by neutrophils in swine endothelial cells (SECs). METHODS: We first examined SIRPα expression on HL-60 cells, a neutrophil-like cell line, and neutrophils isolated from peripheral blood. CD47-expressing SECs or CL-SP-D-expressing SECs were generated through plasmid transfection. Subsequently, these SECs were co-cultured with HL-60 cells or neutrophils. After co-culture, the degree of cytotoxicity was calculated using the WST-8 assay. The suppressive function of CL-SP-D on neutrophils was subsequently examined, and the results were compared with those of CD47 using naïve SECs as controls. Additionally, we assessed ROS production and neutrophil NETosis. RESULTS: In initial experiments, the expression of SIRPα on HL-60 and neutrophils was confirmed. Exposure to CL-SP-D significantly suppressed the cytotoxicity in HL-60 (p = 0.0038) and neutrophils (p = 0.00003). Furthermore, engagement with CD47 showed a suppressive effect on neutrophils obtained from peripheral blood (p = 0.0236) but not on HL-60 (p = 0.4244). The results of the ROS assays also indicated a significant downregulation of SEC by CD47 (p = 0.0077) or CL-SP-D (p = 0.0018). Additionally, the suppression of NETosis was confirmed (p = 0.0125) in neutrophils co-cultured with S/CL-SP-D. CONCLUSION: These results indicate that CL-SP-D is highly effective on neutrophils in xenogeneic rejection. Furthermore, CL-SP-D was more effective than CD47 at inhibiting neutrophil-mediated xenograft rejection.