樹枝狀高分子的非典型螢光現象及其在生醫影像技術上的應用

Intrinsic Blue Luminescence from Dendrimers and Hyperbranched Polymers toward Bioimaging

朱智謙(Chih-Chien Chu) ； 林彥均(Yen-Chun Lin) ； 蕭力嘉(Li-Chia Hsiao)

《化學》 68卷2期 (2010/06) Pp. 87-94

https://doi.org/10.6623/chem.2010010

摘要

在本回顧論文中，我們將介紹樹枝狀高分子不尋常的自發性螢光現象。一般以氮作為分歧點的樹枝狀或超分歧高分子氧化都會產生自發性藍色螢光，激發與放射波長為380 與460nm，量子轉換效率大約在50~60%左右。這一類的螢光高分子缺乏共軛的結構卻能夠發出類似芘分子的藍色螢光，推測可能的原因為樹枝狀結構中作為分歧點的三級胺基團。這一類樹枝狀高分子的自發性螢光受到pH值的影響，在酸性溶液中的螢光放射強度會高於中性與鹼性的溶液；另外，樹枝狀高分子也會產生電致發光的現象，而其電致發光光譜與一般的螢光放射光譜相互吻合，這個結果說明了氧化還原反應導致三級胺基團產生電子電洞對的再結合，進而放出非典型的藍色螢光。由於這一類樹枝狀高分子具有高度的水溶性與生物親合性，加上其自發性藍色螢光的特質，未來在生醫影像技術上的應用潛力相當高。

關鍵字

樹枝狀高分子 ； 螢光 ； 電致發光 ； 生醫影像 ； 氧化 ； 奈米粒子

並列摘要

In this review article, we report the unusual blue luminescence from 1 → 2 N-branched dendrimers and hyperbranched polymers and the applications toward bioimaging. These nonclassical fluorophores lacking of conjugation backbone exhibit remarkable blue fluorescence with moderate quantum yield (52%) upon oxidative treatments. The protonation of tertiary amines within dendrimers leads to a more rigid dendritic structure due to strong charge-charge repulsion, so that the emission intensity increases as the pH value decreases. Moreover, the electro-chemiluminescence (ECL) was also observed during the potential scan between +1.9 V and -2.5 V, implying the electron-hole recombination process of the tertiary amines generates the unusual blue emission. We also found a simple triethylamine upon oxidation shows a similar emission profile with lower quantum yield (0.25%). This result suggested that when the tertiary amines were concentrated and restricted in a confined dedrimer “pocket”, the fluorescence could be enhanced due to the delocalization of electron/holes produced from amines in the excited states. Using the intrinsic fluorescence from these dendrimers toward bioimaging has its advantages: (1) it does not require the incorporation of potentially toxic organic and inorganic fluorophores; (2) the size and mobility of the dendrimers will be unaffected, and the risk of the attached optical probes dissociating before the dendrimer reaches its target is also avoided.

並列關鍵字

Dendrimers ； Luminescence ； ECL ； Bioimaging ； Oxidation ； Nanoparticles