Bioinspired Nanocorals with Decoupled Cellular Targeting and Sensing Functionality
Bioinspired Nanocorals with Decoupled Cellular Targeting and Sensing Functionality
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DOI：
10.1002/smll.200901604
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发表时间：
2010-02-22
期刊：
影响因子：
13.3
通讯作者：
Lee, Luke P.
中科院分区：
文献类型：
--
作者：
Wu, Liz Y.;Ross, Benjamin M.;Lee, Luke P.
感知和检测活细胞内部和周围局部生物分子信号的能力可能会导致诊断准确性和治疗策略的革命性改进[1,2]，其中可以直接研究代表病理和治疗反应详细机制的分子成分或过程。因此，有一种强大的动力来设计小探针，从几十到几百纳米的尺寸，可以定位在活细胞内部或周围的特定区域，以促进分子检测。大多数为此目的开发的纳米探针作为标签或标记，结合并报告特定分子的存在，其读出信号基于探针的固有特性，例如荧光分子的发射，量子点或金属纳米粒子的散射。[3-6]相比之下，纳米等离子光学天线（即金属纳米颗粒）利用表面增强拉曼光谱（SERS）[7,8]和等离子共振能量转移（PRET）[9,10]等技术增强分子光谱信息是有希望的，因为读出信号是纳米探针表面附近分子的固有信号。这种分子指纹提供了潜在的无标签多通道读取出当地的生化成分。[11-14]实现有用的细胞纳米探针的关键技术是将配体附着在纳米探针表面，从而可以靶向特定的细胞类型或亚细胞区域。虽然靶向药物递送[15,16]、光热疗法[17,18]和磁共振成像（MRI）对比增强[19,20]已经被证明具有很大的临床诊断和治疗潜力，但纳米探针既可以实现靶向，也可以实现无标记传感（即SERS），但尚未有报道。通过单个纳米探针实现SERS靶向和传感是具有挑战性的，因为靶向附着在表面的配体会阻碍SERS检测。因此，纳米探针表面的一部分必须保持无配体，以防止SERS表面的阻断，避免混合信号的干扰，或者允许与不同的配体结合以结合感兴趣的分子。在这里，我们提出了一种新型的独立细胞探针，称为纳米珊瑚，它结合了细胞特异性靶向和生物分子传感，但解耦了两种功能模式（图1）。类似于天然海洋珊瑚使用粗糙的表面来最大化表面积以有效捕获光和食物颗粒，[21]纳米珊瑚在纳米尺度上利用高度粗糙的表面来增加分析物的吸附能力并产生高密度的SERS热点。与其他SERS细胞纳米探针（如纯金组成的纳米壳[22]和纳米月牙[7]）相比，纳米珊瑚的聚苯乙烯（PS）半球可以选择性地与抗体功能化，以靶向特定细胞的受体。这种功能化使纳米珊瑚的粗糙金区域清洁，用于SERS测量。因此，目标和传感机制是解耦的，可以为特定的实验单独设计。此外，PS区域还可以作为药物或其他输入化学物质的载体，通过表面疏水吸附[23]或封装[24]，使纳米珊瑚成为多功能纳米传感器。纳米珊瑚阵列的制造是一个简单而经济的三步过程，如图2所示。该工艺首先通过滴铸法在玻璃基板上形成一个六边形紧密堆积的PS纳米球单层。
The ability to sense and detect local biomolecular signaling inside and surrounding a living cell may lead to a revolutionary improvement in diagnostic accuracy and therapeutic strategy,[1, 2] wherein the molecular components or processes that represent detailed mechanisms of pathologies and treatment responses can be directly investigated. Hence, there is a strong driving force to engineer small probes, ranging from tens to hundreds of nanometers in size, that can be positioned in specified regions inside or surrounding living cells in order to facilitate molecular detection. Most nanoprobes developed for this purpose serve as labels or markers that bind to and report the presence of specific molecules, and their read-out signals are based on the intrinsic properties of the probe, such as the emission of ffuorescent molecules, quantum dots, or the scattering of metal nanoparticles.[3–6] In contrast, nanoplasmonic optical antennas (ie, metal nanoparticles) that enhance molecular spectral information, with techniques such as surfaceenhanced Raman spectroscopy (SERS)[7, 8] and plasmonic resonance energy transfer (PRET)[9, 10] are promising since the read-out signal is intrinsic to molecules in proximity to the nanoprobe surface. This molecular fingerprint offers the potential for label-free multichannel read out of local biochemical composition.[11–14] A key technology in achieving useful cellular nanoprobes is the attachment of ligands to the nanoprobe surface to allow targeting to specific cell types or subcellular regions. While targeted drug delivery,[15, 16] photothermal therapy,[17, 18] and magnetic resonance imaging (MRI) contrast enhancement [19, 20] have been demonstrated and have large potential for clinical diagnosis and treatment, nanoprobes that can achieve both targeting and label-free sensing (ie, SERS) have not yet been reported. Achieving both targeting and sensing via SERS in a single nanoprobe is challenging because targeting ligands attached on the surface will impede the SERS detection. Therefore, part of the nanoprobe surface must be kept ligandfree to prevent blocking of the SERS surface, avoid interference of mixed signals, and alternatively to allow conjugation with a different ligand to bind molecules of interest. Here we present a new type of stand-alone cellular probe called a nanocoral, which combines cellular specific targeting with biomolecular sensing, yet decouples the two functional modes (Figure 1). Analogous to natural sea corals that use rough surfaces to maximize surface area for efficient capture of light and food particles,[21] nanocorals utilize a highly roughened surface at the nanoscale to increase analyte adsorption capacity and create a high density of SERS hotspots. In contrast to other SERS cellular nanoprobes, such as nanoshells [22] and nanocrescents [7] composed purely of gold, the polystyrene (PS) hemisphere of the nanocoral can be selectively functionalized with antibodies to target the receptors of specific cells. This functionalization leaves the roughened gold region of the nanocoral clean for SERS measurements. Therefore, the targeting and sensing mechanisms are decoupled and can be separately engineered for a particular experiment. In addition, the PS region may also be used as a carrier for drugs or other input chemicals by surface hydrophobic adsorption [23] or encapsulation,[24] making the nanocoral a multifunctional nanosensor. The fabrication of the nanocoral array is a simple and costeffective three-step process, as illustrated in Figure 2. The process starts with the formation of a hexagonal close-packed monolayer of PS nanospheres on a glass substrate by a drop-cast method …