Due to the heterogeneity of ERBB2-expression between tumors and over the course of treatment, a non-invasive molecular imaging agent is needed to accurately detect overall ERBB2 status. Peptides are a highly advantageous platform for molecular imaging, since they have excellent tumor penetration and rapid pharmacokinetics. One limitation of peptides however, is their traditionally low target affinity, and consequently, tumor uptake. The peptide KCCYSL was previously selected from a bacteriophage (phage) display library to bind ERBB2 and did so with moderate affinity of 295 nM. In order to enhance tumor uptake and clinical utility of the peptide, a novel phage microlibrary was created by flanking the parent sequence with random amino acids, followed by reselection using parallel strategies for high affinity and specific ERBB2 binding in an attempt to affinity maturate the peptide. One limitation of traditional phage display selections is difficulty in releasing the highest affinity phages from the target by incubation of acidic buffer. In an attempt to recover high affinity second-generation peptides from the ERBB2 microlibrary, two elution strategies, sonication and target elution, were undertaken. Sonication resulted in an approximately 50-fold enhancement in recovered phage per round of selection in comparison to target elution. Despite the differences in elution efficiency, the affinities of phage-displayed peptides selected from either strategy were relatively similar. Although both selections yielded peptides with significantly improved affinity in comparison to KCCYSL, the improvements were modest, most likely because the parental peptide binding cannot be improved by additional amino acids.

中文翻译：

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多种噬菌体选择策略可提高靶向ERBB2的肽的亲和力。

由于肿瘤之间和整个治疗过程中ERBB2表达的异质性，因此需要一种非侵入性分子显像剂来准确检测ERBB2的总体状态。肽是分子成像的高度有利平台，因为它们具有出色的肿瘤渗透性和快速的药代动力学。然而，肽的一个局限性是它们传统上的低靶标亲和力，因此是肿瘤吸收。先前从噬菌体（噬菌体）展示文库中选择了肽KCCYSL以结合ERBB2，并以295 nM的中等亲和力结合了该肽。为了增强该肽的肿瘤吸收能力和临床实用性，通过在亲本序列的两侧插入随机氨基酸来创建新的噬菌体微文库，然后使用高亲和力和特异性ERBB2结合的平行策略进行重选，以尝试使肽亲和力成熟。传统噬菌体展示选择的一个局限性是难以通过温育酸性缓冲液从靶中释放出最高亲和力的噬菌体。为了从ERBB2微库中回收高亲和力的第二代多肽，我们采取了两种洗脱策略：超声处理和目标洗脱。与目标洗脱相比，超声处理每轮选择可使回收的噬菌体提高约50倍。尽管洗脱效率有所不同，但从任一种策略中选择的噬菌体展示肽的亲和力都相对相似。尽管与KCCYSL相比，两种选择均产生了亲和力显着提高的肽，