Artificial antibody created by conformational reconstruction of the complementary-determining region on gold nanoparticles.

Mimicking protein-like specific interactions and functions has been a long-pursued goal in nanotechnology. The key challenge is to precisely organize nonfunctional surface groups on nanoparticles into specific 3D conformations to function in a concerted and orchestrated manner. Here, we develop a method to graft the complementary-determining regions of natural antibodies onto nanoparticles and reconstruct their “active” conformation to create nanoparticle-based artificial antibodies that recognize the corresponding antigens. Our work demonstrates that it is possible to create functions on nanoparticles by conformational engineering, namely tuning flexible surface groups into specific conformations. Our straightforward strategy could be used further to create other artificial antibodies for various applications and provides a new tool to understand the structure and folding of natural proteins. To impart biomedical functions to nanoparticles (NPs), the common approach is to conjugate functional groups onto NPs by dint of the functions of those groups per se. It is still beyond current reach to create protein-like specific interactions and functions on NPs by conformational engineering of nonfunctional groups on NPs. Here, we develop a conformational engineering method to create an NP-based artificial antibody, denoted “Goldbody,” through conformational reconstruction of the complementary-determining regions (CDRs) of natural antibodies on gold NPs (AuNPs). The seemingly insurmountable task of controlling the conformation of the CDR loops, which are flexible and nonfunctional in the free form, was accomplished unexpectedly in a simple way. Upon anchoring both terminals of the free CDR loops on AuNPs, we managed to reconstruct the “active” conformation of the CDR loops by tuning the span between the two terminals and, as a result, the original specificity was successfully reconstructed on the AuNPs. Two Goldbodies have been created by this strategy to specifically bind with hen egg white lysozyme and epidermal growth factor receptor, with apparent affinities several orders of magnitude stronger than that of the original natural antibodies. Our work demonstrates that it is possible to create protein-like functions on NPs in a protein-like way, namely by tuning flexible surface groups to the correct conformation. Given the apparent merits, including good stability, of Goldbodies, we anticipate that a category of Goldbodies could be created to target different antigens and thus used as substitutes for natural antibodies in various applications.

在纳米技术中，模拟类蛋白质的特异性相互作用和功能一直是一个长期追求的目标。关键的挑战在于将纳米颗粒上的非功能性表面基团精确地组织成特定的三维构象，使其以协同有序的方式发挥作用。在此，我们开发了一种方法，将天然抗体的互补决定区接枝到纳米颗粒上，并重建其“活性”构象，以创建能够识别相应抗原的基于纳米颗粒的人工抗体。我们的工作表明，通过构象工程，即将柔性表面基团调整为特定构象，在纳米颗粒上创建功能是可能的。我们这种简单的策略可进一步用于创建其他用于各种应用的人工抗体，并为理解天然蛋白质的结构和折叠提供了一种新工具。 为了赋予纳米颗粒（NPs）生物医学功能，常见的方法是借助功能基团本身的功能将其连接到纳米颗粒上。通过对纳米颗粒上的非功能基团进行构象工程来在纳米颗粒上创建类蛋白质的特异性相互作用和功能，目前仍然无法实现。在此，我们开发了一种构象工程方法，通过对金纳米颗粒（AuNPs）上天然抗体的互补决定区（CDRs）进行构象重建，创建了一种基于纳米颗粒的人工抗体，称为“金体（Goldbody）”。控制在游离形式下具有柔性且无功能的CDR环的构象这一看似无法克服的任务，竟然以一种简单的方式得以完成。在将游离CDR环的两端锚定在AuNPs上之后，我们通过调整两端之间的跨度成功地重建了CDR环的“活性”构象，结果在AuNPs上成功地重建了原始的特异性。通过这种策略已经创建了两种金体，它们分别与鸡蛋清溶菌酶和表皮生长因子受体特异性结合，其表观亲和力比原始天然抗体强几个数量级。我们的工作表明，以类蛋白质的方式，即通过将柔性表面基团调整为正确的构象，在纳米颗粒上创建类蛋白质的功能是可能的。鉴于金体具有良好稳定性等明显优点，我们预计可以创建一系列金体来靶向不同的抗原，从而在各种应用中用作天然抗体的替代品。