Modular assembly of proteins on nanoparticles. Nanoparticle-binding proteins

Decoration of nanoparticles with biomolecules has applications in drug delivery and medical diagnostics and can be achieved using a range of well-established chemistries. However, when it comes to structurally complex molecules such as proteins, their intrinsic diversity makes it difficult to find a universal chemical cross-linking strategy that consistently produce functional nanoparticles conjugates. Therefore, protocols for immobilisation have to be empirically and tediously optimised case-by-case. On the other hand, proteins can adsorb spontaneously onto metal surfaces as it is the case for antibodies adsorbed onto gold nanoparticles for their use in lateral flow assays or immunogold staining of tissues. Although passive adsorption is straightforward, unfortunately the adsorbed protein is likely to undergo denaturation, it is not uniformly oriented and, overall, its functionality is compromised.Here we study the use of intermediate designer proteins that are adsorbed onto gold nanoparticles, they contribute to the stability of the colloid suspension and carry a domain which specifically binds to an affinity tag. An arbitrary protein of interest which presents a specific counter-tag can bind to the functionalised particles by simple mixing, with reduced chance to undergo denaturation and inactivation. Importantly, by using this hierarchical strategy, there is no need for optimisation of the conditions, as these are only determined by the affinity system and not by a nanoparticle-protein interaction.

利用生物分子(biomolecules)对纳米颗粒(nanoparticles)进行修饰，可应用于药物递送(drug delivery)与医学诊断(medical diagnostics)领域，且可依托一系列成熟的化学方法完成。然而，针对蛋白质这类结构复杂的分子，其固有多样性使得难以开发出一种通用化学交联策略，以稳定制备功能性纳米颗粒偶联物。因此，固定化(immobilisation)方案必须逐一通过实验且繁琐地进行优化。
另一方面，蛋白质可自发吸附至金属表面，例如侧向流检测(lateral flow assays)或组织免疫金染色(immunogold staining of tissues)中所用的、吸附于金纳米颗粒(gold nanoparticles)的抗体。尽管被动吸附(passive adsorption)操作简便，但吸附的蛋白质极易发生变性，且无法实现定向均匀分布，整体功能会受到损害。
本研究探讨了吸附于金纳米颗粒的中间设计蛋白(intermediate designer proteins)的应用：这类蛋白可提升胶体悬浮液(colloid suspension)的稳定性，并带有一个可特异性结合亲和标签(affinity tag)的结构域。任意带有特异性配对标签(counter-tag)的目标蛋白质，仅需通过简单混合即可结合至该功能化颗粒，变性与失活的概率大幅降低。
重要的是，采用该层级策略(hierarchical strategy)无需对反应条件进行优化，因为反应条件仅由亲和系统(affinity system)决定，而非纳米颗粒-蛋白质相互作用(nanoparticle-protein interaction)。