Kang Kyung Aih, Wang Jianting
Department of Chemical Engineering, University of Louisville, Louisville, KY, 40292, USA.
Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, 20993, USA.
J Nanobiotechnology. 2014 Dec 7;12:56. doi: 10.1186/s12951-014-0056-2.
BACKGROUND: Molecular sensing/imaging utilizing fluorophores has been one of the most frequently used techniques in biomedical research. As for any molecular imaging techniques, fluorescence mediated sensing always seeks for greater specificity and sensitivity. Since fluorophores emit fluorescence while their electron energy state changes, manipulating the local electromagnetic field around the fluorophores may be a way to enhance the specificity and sensitivity. Gold nanoparticles (GNPs) are known to form a very strong electromagnetic field on their surface [i.e., surface plasmon field (SPF)], upon receiving photonic energy. The level of fluorescence change by GNP-SPF may range from complete quenching to extensive enhancement, depending upon the SPF strength, excitation and emission wavelengths, and quantum yield of the fluorophore. METHOD: Here, we report a novel design that utilizes BOTH fluorescence quenching and enhancement abilities of the GNP in one single nano-entity, providing high specificity and sensitivity. The construct utilizes a specially designed molecular dual-spacer that places the fluorphore at the location with an appropriate GNP-SFP strength before and after exposed to the biomarker. A model system to test the concept was an optical signal mediator activated by urokinase-type plasminogen activator (uPA; breast cancer secreting enzyme). RESULTS: The resulting contrast agent shows less than 10% of the natural fluorescence but, in the presence of uPA, its fluorescence emission is triggered and emits its fluorescence approximately twice of the natural form. CONCLUSION: This study demonstrated that our novel design of an optical contrast agent can be conditionally activated with enhanced sensitivity, using both quenching and enhancement phenomena of fluorophores in the electromagnetic field of the appropriate strengths (in this case, locally generated by the GNP-SPF). This entity is similar to molecular beacon in terms of specificity but with greater sensitivity. In addition, it is not restricted to only DNA or RNA sensing but for any designs that cause the change in the distance between the fluorophore and GNP, upon the time of encountering biomarker of interest.
背景：利用荧光团的分子传感/成像一直是生物医学研究中最常用的技术之一。对于任何分子成像技术而言，荧光介导的传感始终追求更高的特异性和灵敏度。由于荧光团在其电子能态变化时会发出荧光，因此操纵荧光团周围的局部电磁场可能是提高特异性和灵敏度的一种方法。已知金纳米颗粒（GNP）在接收光子能量后会在其表面形成非常强的电磁场[即表面等离子体场（SPF）]。GNP-SPF引起的荧光变化程度可能从完全淬灭到大幅增强不等，这取决于SPF强度、激发和发射波长以及荧光团的量子产率。 方法：在此，我们报告了一种新颖的设计，该设计在单个纳米实体中同时利用了GNP的荧光淬灭和增强能力，从而提供了高特异性和灵敏度。该构建体利用了一种特殊设计的分子双间隔物，该间隔物在暴露于生物标志物之前和之后将荧光团置于具有适当GNP-SFP强度的位置。一个测试该概念的模型系统是由尿激酶型纤溶酶原激活剂（uPA；乳腺癌分泌酶）激活的光信号介质。 结果：所得造影剂显示出的天然荧光不到10%，但在存在uPA的情况下，其荧光发射被触发，发出的荧光约为天然形式的两倍。 结论：本研究表明，我们新型的光学造影剂设计可以通过利用适当强度（在这种情况下，由GNP-SPF局部产生）的电磁场中荧光团的淬灭和增强现象，以增强的灵敏度进行条件激活。该实体在特异性方面与分子信标相似，但具有更高的灵敏度。此外，它不仅限于DNA或RNA传感，还适用于任何在遇到感兴趣的生物标志物时导致荧光团与GNP之间距离发生变化的设计。
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