Gold nanoparticle (GNP)-based aggregation assay is simple, fast, and employs a colorimetric detection method. Although previous studies have reported using GNP-based colorimetric assay to detect biological and chemical targets, a mechanistic and quantitative understanding of the assay and effects of GNP parameters on the assay performance is lacking. In this work, we investigated this important aspect of the GNP aggregation assay including effects of GNP concentration and size on the assay performance to detect malarial DNA. Our findings lead us to propose three major competing factors that determine the final assay performance including the nanoparticle aggregation rate, plasmonic coupling strength, and background signal. First, increasing nanoparticle size reduces the Brownian motion and thus aggregation rate, but significantly increases plasmonic coupling strength. We found that larger GNP leads to stronger signal and improved limit of detection (LOD), suggesting a dominating effect of plasmonic coupling strength. Second, higher nanoparticle concentration increases the probability of nanoparticle interactions and thus aggregation rate, but also increases the background extinction signal. We observed that higher GNP concentration leads to stronger signal at high target concentrations due to higher aggregation rate. However, the fact the optimal LOD was found at intermediate GNP concentrations suggests a balance of two competing mechanisms between aggregation rate and signal/background ratio. In summary, our work provides new guidelines to design GNP aggregation-based POC devices to meet the signal and sensitivity needs for infectious disease diagnosis and other applications.

中文翻译：

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通过纳米颗粒大小，浓度和大小组合调整寡核苷酸检测的金纳米颗粒比色测定。

基于金纳米颗粒（GNP）的聚集测定法简单，快速，并且采用比色检测方法。尽管以前的研究已经报道了使用基于GNP的比色测定来检测生物学和化学目标，但是仍缺乏对测定的机械和定量理解以及GNP参数对测定性能的影响。在这项工作中，我们研究了GNP聚集测定法的这一重要方面，包括GNP浓度和大小对检测疟疾DNA的测定性能的影响。我们的发现使我们提出了决定最终测定性能的三个主要竞争因素，包括纳米粒子聚集速率，等离子体耦合强度和背景信号。首先，增加纳米粒子的尺寸会降低布朗运动，从而降低聚集率，但显着提高了等离子体耦合强度。我们发现，较大的GNP会导致更强的信号并改善检测限（LOD），表明等离激元耦合强度起主要作用。其次，较高的纳米粒子浓度增加了纳米粒子相互作用的可能性，从而增加了聚集速率，但同时也增加了背景消光信号。我们观察到较高的GNP浓度会由于较高的聚集速率而在较高的目标浓度下导致较强的信号。然而，在中等GNP浓度下发现最佳LOD的事实表明，聚集速率和信号/背景比之间存在两种竞争机制的平衡。总之，