The affinity of surfaces toward proteins is found to be a key parameter to govern the synthesis of polymer brushes by surface-initiated biocatalytic atom transfer radical polymerization (SI-bioATRP). While the “ATRPase” hemoglobin (Hb) stimulates only a relatively slow growth of protein repellent brushes, the synthesis of thermoresponsive grafts can be regulated by switching the polymer’s attraction toward proteins across its lower critical solution temperature (LCST). Poly(N-isopropylacrylamide) (PNIPAM) brushes are synthesized in discrete steps of thickness at temperatures above LCST, while the biocatalyst layer is refreshed at T < LCST. Multistep surface-initiated biocatalytic ATRP demonstrates a high degree of control, results in high chain end group fidelity and enables the synthesis of multiblock copolymer brushes under fully aqueous conditions. The activity of Hb can be further modulated by tuning the accessibility of the heme pocket within the protein. Hence, the multistep polymerization is accelerated at acid pH, where the enzyme undergoes a transition from its native to a molten globule conformation. The controlled synthesis of polymer brushes by multistep SI-bioATRP highlights how a biocatalytic synthesis of grafted polymer films can be precisely controlled through the modulation of the polymer’s interfacial physicochemical properties, in particular of the affinity of the surface toward proteins. This is not only of importance to gain a predictive understanding of surface-confined enzymatic polymerizations, but also represents a new way to translate bioadhesion into a controlled functionalization of materials.

中文翻译：

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通过可切换的生物亲和性控制表面的酶促聚合

发现表面对蛋白质的亲和力是控制通过表面引发的生物催化原子转移自由基聚合（SI-bioATRP）进行聚合物刷合成的关键参数。虽然“ ATRPase”血红蛋白（Hb）仅刺激相对较慢的蛋白质排斥刷的生长，但可以通过在较低的临界溶液温度（LCST）上切换聚合物对蛋白质的吸引力来调节热响应性接枝的合成。在高于LCST的温度下以不连续的厚度步骤合成聚N-异丙基丙烯酰胺（PNIPAM）刷子，同时在T处刷新生物催化剂层<LCST。多步表面引发的生物催化ATRP表现出高度的控制力，可实现高链端基保真度，并能够在完全含水的条件下合成多嵌段共聚物刷。可以通过调节蛋白质中血红素口袋的可及性来进一步调节Hb的活性。因此，在酸性pH下加速了多步聚合，其中酶经历了从其天然构象到熔融小球构象的转变。通过多步SI-bioATRP进行聚合物刷的受控合成，突显了如何通过调节聚合物的界面物理化学特性（特别是表面对蛋白质的亲和力）来精确控制接枝聚合物薄膜的生物催化合成。