外文翻譯生物分子

1、湖北汽車工業(yè)學(xué)院畢業(yè)設(shè)計(jì)（論文）英文翻譯生物分子-功能性納米線：從納米傳感器到納米載體摘要：納米線特別的屬性為設(shè)計(jì)新一代具有新奇功能的設(shè)備及系統(tǒng)提供了極佳前景。這篇回顧總結(jié)了近期在制備納米線-生物材料混合物和他們作為納米傳感器，納米制動(dòng)器和納米載體方面的科學(xué)研究成果。納米線可以通過與各種生化藥劑發(fā)生不同的化學(xué)反應(yīng)來實(shí)現(xiàn)功能化。納米線與生化藥劑如此的結(jié)合獲得了前所未有的混合系統(tǒng)，這種系統(tǒng)結(jié)合了生化藥劑的催化劑特性和納米線顯著的電子和結(jié)構(gòu)特性。受體-功能化的納米線在實(shí)時(shí)無標(biāo)記電子檢測(cè)生物分子的相互作用方面的優(yōu)點(diǎn)是格外顯著的。這種獨(dú)一無二的屬性決定了納米線的微結(jié)構(gòu)，特別是多節(jié)納米線的設(shè)計(jì)，為確定不同

2、生物分子結(jié)構(gòu)提供了準(zhǔn)確的空間領(lǐng)域。這使得獲得的納米線能同時(shí)操作幾項(xiàng)任務(wù)，并使得其在納米生物電子和納米醫(yī)藥方面的重要運(yùn)用成為可能。例如，運(yùn)用于納米醫(yī)藥方面的多節(jié)納米線可以選擇目標(biāo)，治療和成像。不同生物識(shí)別的這種空間定位也提供了一種極大的可能：在先決設(shè)計(jì)中實(shí)現(xiàn)納米線的自組。這種設(shè)計(jì)納米線-生物材料混合系統(tǒng)和設(shè)備的可能性和挑戰(zhàn)性將在接下來的部分中討論。1.為什么是納米線納米線在構(gòu)建納米技術(shù)中發(fā)揮了極其重要的作用。例如一維納米線最近獲得了極大的關(guān)注因?yàn)樗麄冊(cè)诓煌I(lǐng)域的應(yīng)用潛力。這種關(guān)注主要體現(xiàn)在納米線的高厚徑比（和新奇的電子傳導(dǎo)和光學(xué)特性）與極大的外表面有關(guān)的多功能性（多節(jié)）因?yàn)榘烁鞣N材料所以具備

3、了各種功能。不同厚徑比的納米線很好的協(xié)調(diào)了他們的光電特性。其中一個(gè)制備多節(jié)納米線的常用途徑包括電沉積進(jìn)一個(gè)主要多孔薄膜樣板的圓柱形納米孔，然后樣板溶解。這種樣板主導(dǎo)的電沉積代表了一種先進(jìn)的方法去制備直徑10-300nm長度50-2000nm的納米線。可以電鍍的材料包括金屬，高分子或者金屬氧化物，他們可以作為所獲得納米線的一部分。這種樣板輔助電化學(xué)綜合體對(duì)于制備廣泛的化學(xué)組成成分非常有用，包括一種金屬-半導(dǎo)體-聚合物納米線。多節(jié)納米線可以通過幾種材料有序的電沉積來制備，通過放入樣板孔中實(shí)現(xiàn)不同的先決長度（圖1）。每個(gè)納米線的不同片段具有獨(dú)特的化學(xué)物理性質(zhì)。這樣還可以用不同材料（因此還有特性）的單

4、元納米線段來設(shè)計(jì)復(fù)合納米線。這種特性決定了多節(jié)或者復(fù)合納米線的微結(jié)構(gòu)，使得獲得的納米線能同時(shí)進(jìn)行多個(gè)任務(wù)，還可以制備各種納米級(jí)設(shè)備例如感應(yīng)器，燃料細(xì)胞，制動(dòng)器和納米發(fā)動(dòng)機(jī)。圖1.多節(jié)納米線的薄膜樣板電化學(xué)制備納米線和生物分子的結(jié)合產(chǎn)生了新型混合系統(tǒng)：結(jié)合了生物材料催化特性和納米線良好的電子和結(jié)構(gòu)特點(diǎn)。使用準(zhǔn)確綁定于不同片段的分子連接體，可以沿著含有不同生物分子和其他材料的納米線尋找特定功能的單一片段。這種修改不同生物材料組成的納米線表面的能力，和各種生物分子的空間定位特性，為設(shè)計(jì)多功能納米線-生物材料混合系統(tǒng)提供了極大的保證，包括從納米感應(yīng)器到納米傳送汽車的多種重要應(yīng)用。它還為納米線自組成先決

5、結(jié)構(gòu)和先進(jìn)納米循環(huán)中的控制定位提供了極大的可能。這篇回顧總結(jié)了具有生物分子的納米線的功能，最近制備納米線-生物材料混合物的科學(xué)成果，和這種混合物在不同重要領(lǐng)域的可能運(yùn)用，包括納米感應(yīng)器，納米制動(dòng)器，和納米醫(yī)藥。2.表面功能化的納米線納米線通過各種建立的過程可以攜帶不同的生物分子,包括酶、抗體、核酸。這種功能化傳授催化和識(shí)別/綁定屬性到這些一維納米材料。根據(jù)特定的納米線材料,不同的功能化方案可以用于限制不同的生物分子到表面。而分子連接器(與捕獲的生物分子發(fā)生交聯(lián)作用)是最常用的,與生物分子直接功能化也可以使用。由于不同的相應(yīng)部分的表面化學(xué)，運(yùn)用樣板制造的多節(jié)納米線會(huì)導(dǎo)致空間控制功能化。單個(gè)片段可

6、以按預(yù)先設(shè)計(jì)的空間控制順序被修改。這種定位功能依賴于單一材料片段的不同反應(yīng)和沿著納米線精確綁定于不同片段的分子連接器。樣板制備方法促進(jìn)了納米線邊緣的生物功能化，滿足了各種（端到端）組裝應(yīng)用的需要。各種連鎖化學(xué)反應(yīng)可以用來使具有不同生物分子的單一片段依照相應(yīng)段材料的特定表面化學(xué)反應(yīng)實(shí)現(xiàn)功能化（圖2）。例如，烷基硫醇與金易結(jié)合，組氨酸與鎳易結(jié)合，而氰化物與鉑易結(jié)合。多節(jié)納米線的這種選擇性功能化需要注意相應(yīng)綁定的親和力和功能化的順序。使用烷基硫醇的多功能性形成自組裝層源于它們的能力,可以進(jìn)一步修改為化學(xué)或生物表面活性層(通過共價(jià)耦合不同材料的功能末端)。例如,不同的羧基或氨基功能團(tuán)可用于交聯(lián)胺或通過

7、碳水化合物調(diào)節(jié)的酯化或酰胺化反應(yīng)捕獲的生物分子的羧基酸基團(tuán)。生物素連接器可以嵌入傳導(dǎo)聚合物段而醛組可以被整合到硅納米線的表面。直接與生物分子功能化的納米線(沒有鏈接器)也可以實(shí)現(xiàn)。例如,硫醇化的DNA自組裝在金表面,而酶可以在聚合物納米線的電聚合生長期間被截留。在后一種情況下, 用于溶解膜模板的苛刻化學(xué)條件可能對(duì)生物催化反應(yīng)的結(jié)果產(chǎn)生深遠(yuǎn)的(不良)影響。此外,導(dǎo)電聚合物納米線可以在電聚合化和樣板溶解步驟之后(通過某些群體,如。,羧基單體) 功能化。各種生物醫(yī)學(xué)應(yīng)用將受益于納米線表面上大量的親水基團(tuán)(比如半個(gè)。聚(乙二醇),乙醇胺),從而使其抗蛋白質(zhì)。表面化學(xué)還應(yīng)該確保正確的方向,因此需要一個(gè)具

8、有良好生物活性和可接受的受體(特別是在生物親和性實(shí)驗(yàn)中)。在黃金納米線上的硫烷混合層尤其具有吸引力，它控制受體取向而減少非特異性吸附的影響。圖2. 選擇性功能化的多節(jié)的金屬納米線與寡核苷酸和蛋白質(zhì)通過不同的連接器連接。這樣的空間局部功能化給予以納米線為基礎(chǔ)的設(shè)備多功能性。3.以納米線生物材料為基礎(chǔ)的親和力生物傳感器納米線獨(dú)特的性質(zhì)為生物識(shí)別接口從電子信號(hào)轉(zhuǎn)導(dǎo)到強(qiáng)大的生物電信號(hào)傳感器的設(shè)計(jì)提供出色的前景。一維(1 d)半導(dǎo)體或?qū)щ娋酆衔锛{米線等電子檢測(cè)尤其具有吸引力,他們能無標(biāo)簽實(shí)時(shí)監(jiān)測(cè)生物分子的相互作用。因?yàn)榧{米線的表面體積比高和新穎的電子傳遞性能,他們的電子電導(dǎo)受到輕微的表面擾動(dòng)的強(qiáng)烈影響。

9、把目標(biāo)生物分子綁定到功能化受體的半導(dǎo)體納米線從而導(dǎo)致在“大部分”納米線結(jié)構(gòu)中載體的損耗或積累, 因此產(chǎn)生了不同的電導(dǎo)率信號(hào)。與其相反的是，平面薄膜半導(dǎo)體器件只有表面受到綁定事件的影響。這樣的納米線傳感器從而直接提供對(duì)生物親和力相互作用的無標(biāo)簽的實(shí)時(shí)電檢測(cè)。實(shí)時(shí)監(jiān)控功能還能通過高度可逆的電導(dǎo)率變化顯示來自表面受限受體的目標(biāo)分析物的綁定(捕獲)和解脫(釋放)(圖3)。圖3. 單個(gè)病毒從一個(gè)硅納米線設(shè)備的抗體受體上綁定和解脫并隨時(shí)間變化產(chǎn)生相應(yīng)的電導(dǎo)率變化。納米線的極小規(guī)模也顯示出對(duì)大量減少納米傳感器陣列的極大潛力。它能把大量的傳感元件安裝到一小塊地方用于創(chuàng)建高度密集陣列設(shè)備。盡管仍然面臨挑戰(zhàn)，就裝

10、配可控性和連接性來講，納米線是優(yōu)于類似的1 (D) 碳納米管的。單個(gè)納米線感應(yīng)器元件和不同表面受體的功能化導(dǎo)致不同的目標(biāo)生物分子多組分生物檢測(cè)和為疾病生物標(biāo)志物的篩選提供了廣闊的前景。2001年的前輩的開創(chuàng)性工作說明了這些功能：利用摻硼硅納米線來監(jiān)控不同的生物分子的相互作用。這種半導(dǎo)體納米線的使類型和摻雜劑級(jí)別相適應(yīng)并控制焊絲直徑的能力，尤其引人矚目，這優(yōu)化他們的電氣性能，因此還優(yōu)化靈敏度。4.基于納米線的DNA檢測(cè)和組裝功能化的半導(dǎo)體納米線傳感器與寡核苷酸探針提供一個(gè)有吸引力的方案用于無標(biāo)記電子檢測(cè)DNA雜交。Lieber的團(tuán)隊(duì)修改硅納米線與肽核酸(PNA)受體用來檢測(cè)基因突變，其占囊性纖維

11、化病例誘發(fā)率的75%左右。由于提高了PNA探針識(shí)別不匹配的能力，這種PNA功能化的納米線能夠區(qū)分在囊性纖維化跨膜受體（CFTR）基因中的野生型DF508突變體。通過干預(yù)一個(gè)親和素蛋白質(zhì)層，PNA受體連接到納米線表面。這個(gè)概念被GAO et al擴(kuò)展用來設(shè)計(jì)一種依賴濃度的電阻來顯示PNA捕捉探針-功能化硅納米線陣列，其可以在一個(gè)大動(dòng)態(tài)范圍內(nèi)響應(yīng)，檢測(cè)極限高達(dá)10fm。表面固定通過末端為氨基的PNA探針與硅烷化的硅納米線陣列的醛基結(jié)合來實(shí)現(xiàn)。Ozkan的團(tuán)隊(duì)報(bào)道了三段式納米線的使用,由碲化鉻-黃金-碲化鉻組成和電化學(xué)有序沉積而成, 作為場效應(yīng)晶體管(FET)用于DNA雜交的超靈敏檢測(cè)。黃金段提供了

12、有利的表面功能化屬性用于連接硫醇化的 ssDNA探針，在半導(dǎo)體CdSe段顯示出引人矚目的電氣性能和調(diào)變納米線電導(dǎo)性。希斯的小組報(bào)道了使用烷基化無氧硅納米線在一個(gè)生理相關(guān)的媒介內(nèi)實(shí)時(shí)測(cè)量DNA雜交。這些DNA化驗(yàn)使用的末端為氨基的烷基層是直接產(chǎn)生在末端為氫基的硅納米線上的。實(shí)時(shí)DNA檢測(cè)功能如圖4所示。圖4.在硅納米線傳感器上不同濃度DNA目標(biāo)物的實(shí)時(shí)監(jiān)測(cè)。除了用作電子傳感器, 攜帶ssDNA的納米線可以用作放大標(biāo)記雜交檢測(cè)。例如,我們的團(tuán)隊(duì)展示了使用金-銦納米線的電化學(xué)檢測(cè)DNA雜交。在這里,長段銦提供了一個(gè)高度敏感的剝離伏安法探針檢測(cè)而短的黃金段用于耦合二次硫醇化的DNA探針。DNA功能化納

13、米線的雜交和空間定位表面功能化的多節(jié)納米線在提供表面圖案的設(shè)計(jì)和創(chuàng)建預(yù)定的兩或三維納米線的架構(gòu)方面也大有前途。秩序井然的納米結(jié)構(gòu)的創(chuàng)建是以納米線為基礎(chǔ)的微型設(shè)備的許多成功應(yīng)用的關(guān)鍵。Mallouk的團(tuán)隊(duì)發(fā)布了金納米線的雜交-誘導(dǎo)DNA組裝成預(yù)定設(shè)計(jì)的圖案。這種DNA為向?qū)У募{米線組裝應(yīng)該使他們作為構(gòu)建微型設(shè)備模塊和納米循環(huán)元素的使用更容易。在最近來自賓夕法尼亞州大學(xué)的另一個(gè)貢獻(xiàn)中，Keating的組描述了使用電場力來把寡核苷酸官能化的納米線的不同部分導(dǎo)到一個(gè)微芯片的特定區(qū)域同時(shí)提供在每個(gè)納米線和在這個(gè)區(qū)域光刻成像出的特征的準(zhǔn)確的記錄。5.酶-功能化的納米線酶-功能化的納米線結(jié)合了酶的生物催化性

14、質(zhì)與納米線的獨(dú)特優(yōu)勢(shì)。這樣被酶限制的納米線可用于不同生物電子設(shè)備,包括生物傳感器、生物燃料電池, 生物制動(dòng)器。氧化鋅(ZnO)納米線的物理和化學(xué)性質(zhì)與葡萄糖氧化酶(氣態(tài)氧)相適應(yīng)用來構(gòu)建一個(gè)高性能的葡萄糖傳感器(圖7)。這樣的表現(xiàn)歸功于氧化鋅納米線的中介效應(yīng)和大的比表面積。氧化鋅的離電子點(diǎn)(IEP) 對(duì)于通過靜電相互作用固定酸性蛋白質(zhì)正是一個(gè)好的陣列。硅納米線(SiNWs)也被證實(shí)支持該陣列，用于在葡萄糖生物傳感器中酶的固定。因此葡萄糖氧化酶是在不同治療后吸附到SiNWs上, 或者生成, HF-腐蝕的或羧基-酸功能化的。電流型生物傳感器與羧基-功能化的 SiNWs最多能檢測(cè)出0.01毫米葡萄糖

15、。圖7.以氣態(tài)氧/氧化鋅-納米線為基礎(chǔ)的葡萄糖傳感器的制備酶-功能化的納米線還可以被用于設(shè)計(jì)即期切換生物電子設(shè)備。這樣的電子生物設(shè)備的磁性開關(guān)(激活)已經(jīng)利用金/鎳等分的納米線完成了。這類自適應(yīng)納米線具有磁激活生物電子的流程，為規(guī)范生物燃料細(xì)胞，生物反應(yīng)器，和對(duì)特定需求的生物傳感裝置的操作提供了巨大的希望。這里,黃金段作為酶的“載體”,而鎳提供了磁處理。圖8顯示了這些以納米線為基礎(chǔ)的生物葡萄糖電子化的調(diào)節(jié)過程。納米線在水平方向的定位導(dǎo)致了酶可調(diào)節(jié)的活化作用-由于納米線受限的氣態(tài)氧和界面二茂鐵中介物（A）的有效接觸。納米線切換到垂直位置阻礙了氣態(tài)氧和界面二茂鐵(B) 之間的通信。通過切換酶-功能

16、化的納米線在水平和垂直位置之間的表面取向，這種磁調(diào)制生物電子過程可以重復(fù)多次。圖8.以納米線為基礎(chǔ)的生物電子轉(zhuǎn)換流程的優(yōu)化。設(shè)置包括氣態(tài)氧-金/鎳納米線和二茂鐵-改性表面,在磁場中的水平位置(A)和垂直位置(B)，激活(A)和阻礙(B)之間的納米線-受限的酶和二茂鐵表面間的通信。上部也顯示了相應(yīng)的循環(huán)伏安。類似的可切換的生物電子系統(tǒng)用于開發(fā)乙醇的酶轉(zhuǎn)換連接醇脫氫酶（ADH）-功能化的納米線。為此,我們把金/鎳納米線的多功能性和碳納米管(CNT)的電性能相結(jié)合。集成納米線-CNT微系統(tǒng)依靠ADH-功能化的三段式 (Ni-Au-Ni)納米線和CNT-改良的測(cè)量電流的傳感器。納米線從垂直切換到水平的

17、取向轉(zhuǎn)換 (在乙醇基底和NAD +輔因子的存在下)把抗利尿激素及其NADH產(chǎn)物帶到CNT薄膜上。這促進(jìn)了NADH的電子檢測(cè)和NAD +的再生，這是連續(xù)重復(fù)生物電子作用所必需的。這樣功能化磁性納米線的控制生物電子化過程的能力已經(jīng)被用于開發(fā)雙重若能系統(tǒng),甲醇和乙醇連接到AOx和ADH同時(shí)發(fā)生電子感應(yīng),分別被固定在黃金段的中央。6.用于藥品運(yùn)輸?shù)募{米線載體納米材料在醫(yī)學(xué)方面的使用，特別是在運(yùn)輸給定藥品方面，是納米技術(shù)最重要的應(yīng)用之一。而球形納米粒子在納米醫(yī)藥方面的應(yīng)用得到最大的關(guān)注,然而對(duì)于多功能操作，這樣的粒子有一個(gè)重要的限制, 它們只有一個(gè)(外)表面。相比之下,納米線可以提供獨(dú)特的空間定義的地區(qū)

18、(段),由不同的材料組成, 這就允許這些線同時(shí)執(zhí)行一些任務(wù),包括選擇目標(biāo)、個(gè)體化治療和成像功能。然而,健康問題可能會(huì)限制這些材料的選擇。這樣的金納米線可以因此吸收near-IR(NIR)光和發(fā)射所需的熱量用來局部高熱破壞腫瘤。 這是特別重要的體內(nèi)應(yīng)用因?yàn)檫@是在NIR光譜范圍內(nèi)通過生物組織的最大的光透射率。通過從金納米粒子到黃金納米線的過程中改變形狀,還可以提高散射特性和增強(qiáng)成像能力。具有不同的生物分子的功能化納米線在納米醫(yī)學(xué)方面應(yīng)用的重要性不能被高估了。表面化學(xué)的控制修改對(duì)于目標(biāo)藥物輸送是至關(guān)重要的。額外的注意事項(xiàng),如特異性針對(duì)非特異性吸收,細(xì)胞毒性,循環(huán)壽命也必須加緊解決。由于許多有吸引力的

19、屬性(如上所述)功能化金納米線得到了相當(dāng)大的關(guān)注,它能有效阻止癌細(xì)胞診斷和選擇性光熱光譜分析治療。例如, 金納米線與抗-EGFR抗體(EGFR:表皮生長因子受體) 發(fā)生共軛作用被用于特定的綁定到惡性細(xì)胞。圖9。功能化金納米線在體內(nèi)針對(duì)乳腺癌的腫瘤。這些納米線通過赫賽汀酸共價(jià)反應(yīng)連接到赫賽汀。PEG硫醇通過硫醇的一部分連接到納米線。同樣,赫賽汀的抗體和聚乙二醇(PEG)共同固定在金納米線(圖9)最近開始使用于在體內(nèi)針對(duì)乳腺腫瘤的治療。在金納米棒上的PEG或CTAB涂層在光熱光譜分析腫瘤消融方面被證明非常有用。 埃爾賽義德的小組也報(bào)告縮氨酸金納米棒的制備(通過三烷基-三唑鏈接器),和他們有效的傳導(dǎo)

20、能力,并能迅速進(jìn)入細(xì)胞。最近展示了不同DNA寡核苷酸的選擇性光從金納米線中釋放。這種路徑依賴超快激光輻照產(chǎn)生選擇性的金納米棒并為傳送多種藥品的策略提供了相當(dāng)大的保證。英文原文：Biomolecule-Functionalized Nanowires: From Nanosensors to NanocarriersJoseph Wang*aThe unique properties of nanowires offer excellent prospects for designing a new generation of devices and systems exhibiting nov

21、el functions. This Review discusses recent scientific accomplishments in the preparation of nanowirebiomaterial hybrids and their potential applications as nanosensors, nanoactuators, and nanocarriers. Nanowires can be readily functionalized with various biochemicals through different linkage chemis

22、tries. Such integration of nanowires and biomolecules leads to novel hybrid systems which couple the recognition or catalytic properties of biomaterials with the attractive electronic and structural characteristics of nanowires. Receptor-functionalized nanowires are particularly attractive for direc

23、t real-time label-free electrical detection of biomolecular interactions. The unique control over the microstructure of nanowires, and particularly the design of multisegment nanowires, offer spatially defined regions for the defined organization of different biomolecules. This allows the resulting

24、nanowires to perform several tasks simultaneously, and opens the door to a variety of important applications in the areas of nanobioelectronics and nanomedicine. For example, multisegment nanowires designed for nanomedicine applications can couple the selective targeting, therapy, and imaging functi

25、ons. Such spatially defined anchoring of different biorecognition sites provides also distinct opportunities for the self assembly of nanowires into predetermined designs. The opportunities and challenges involved in designing such nanowirebiomaterial hybrid systems and devices are discussed in the

26、following sections.Why Nanowires?Nanowires are critically important building blocks of nanotechnology. 1, 2 Such one-dimensional (1D) nanomaterials have received considerable recent attention owing to their potential applications in different fields. Such attention reflects primarily the high aspect

27、 ratio of nanowires (and corresponding novel electron transport and optical properties) and the versatility associated with the ability to generate multiple outer surfaces (segments) consisting of different materials and hence different spatially resolved functions. The ability to prepare nanowires

28、of different aspect ratios allows fine tuning of their electronic and optical properties. One common versatile route for preparing multifunctional nanowires involves electrodeposition into the cylindrical nanopores of a host porous membrane template, followed by dissolution of the template.3, 4 Such

29、 template- directed electrodeposition represents an attractive approach for preparing nanowires with diameters of 10300 nm and lengths of 502000 nm. Any material that can be electroplated, including metals, polymers, or metal oxides, can be used as a portion of the resulting nanowires. Such template

30、-assisted electrochemical synthesis has been extremely useful for preparing nanowires with broad range of chemical compositions, including a metallic, semiconductor and polymeric nanowires. Multisegment nanowires can be prepared through sequential electrodeposition of several materials, with differe

31、nt predetermined lengths, into the pores of the template (Figure 1).5 Each of these different segments possesses unique chemical and physical properties. It is also possible to combine different materials (and hence properties) into a single-segment nanowire through the design of composite nanowires

32、 (e.g., gold/ polypyrrole).6 The unique control over the microstructure of multisegment or composite nanowires leads to multifunctionality that allows the resulting nanowires to perform several tasks simultaneously, and opens the door to a variety of important nanoscale devices such as sensors, fuel

33、 cells, actuators, and nanomotors.The integration of nanowires and biomolecules leads to new hybrid systems that couple the recognition or catalytic properties of biomaterials with the attractive electronic and structural characteristics of nanowires. Using molecular linkages that specifically bind

34、to different segments, it is possible to selectively functionalize the individual segments along the nanowires with different biomolecules as well as with other materials.7 Such ability to modify the surfaces of nanowires with different biomaterials, and the unique spatial organization of the variou

35、s biomolecules, offer considerable promise for designing multifunctional nanowirebiomaterial hybrid systems for diverse and important applications, ranging from nanosensors to nanodelivery vehicles. It also offers distinct opportunities for self-assembly of nanowires into predetermined architectures

36、 and their controlled positioning in advanced nanocircuitry.This Review discusses the functionalization of nanowires with biomolecules, recent scientific accomplishments in the preparation of nanowirebiomaterial hybrids, and the potential applications of such hybrids in different important areas, in

37、cluding nanosensors, nanoactuators, and nanomedicine.Surface Functionalization of NanowiresNanowires can be functionalized with different biomolecules, including enzymes, antibodies or nucleic acids, through a variety of established procedures. Such functionalization imparts catalytic and recognitio

38、n/binding properties onto these 1D nanomaterials. Depending on the specific nanowire material, different functionalization schemes can be used for confining different biomolecules onto the surface. While molecular linkers (cross-linked to the captured biomolecule) are most commonly used, direct fuct

39、ionalization with the biomolecule can also be employed. Template-grown multisegment nanowires can lead to spatially controlled functionalization owing to the distinct surface chemistry of the corresponding segments.7 The individual segments can thus be modified sequentially with defined spatial cont

40、rol. Such localized functionalization relies on the differential reactivity of the individual segment materials and involves molecular linkages that bind specifically to different segments along the nanowires. The template preparation route facilitates the biofunctionalization of the edges of nanowi

41、res, as desired for various (end-to-end) assembly applications.Various linkage chemistries can be used to functionalize the individual segments with different biomolecules in accordance with the specific surface chemistry of the corresponding segment material (Figure 2). For example, alkyl thiols bi

42、nd strongly to gold, histidine binds strongly to nickel, while isocyanides bind strongly to platinum. Such selective functionalization of multisegment nanowires requires careful attention to the relative binding affinities and to the order of functionalization. The versatility of using alkyl thiols

43、stems from their ability to form self-assembled monolayers that can be further modified into chemically- or biologically reactive surface layers (via covalent coupling of different materials to their functional end group). For example, different carboxylic or amine end groups can be used for cross-l

44、inking with the amine or carboxylic-acid groups of the captured biomolecule through carbodiimde-mediated esterification or amidation reactions. Biotin linkers can be embedded within conducting-polymer segments while aldehyde groups can be incorporated onto silicon nanowire surfaces.Direct functional

45、ization of nanowires with biomolecules (without a linker) can also be achieved. For example, thiolated DNA can be self-assembled on gold surfaces while enzymes can be entrapped during the electropolymeric growth of polymeric nanowires. In the latter case, the harsh chemical conditions used for disso

46、lving the membrane template may have a profound (adverse) effect upon the resulting biocatalytic activity. 8 Alternately, conducting polymer nanowires can be functionalized after the electropolymerization and template-dissolution steps (through certain groups, e.g., carboxy, in the monomer). Various

47、 biomedical applications would benefit from blocking of the remaining surface of the nanowire with hydrophilic moieties e.g., poly(ethylene glycol), ethanolamine and hence making it protein resistant. The surface chemistry should also ensure proper orientation and hence an optimal bioactivity and ac

48、cessibility of the receptor (particularly in connection to bioaffinity assays). Mixed monolayers of alkylthiols on gold nanowires are particularly attractive for controlling the receptor orientation while minimizing non-specific adsorption effects.NanowireBiomaterial-Based Affinity BiosensorsThe uni

49、que properties of nanowires offer excellent prospects for interfacing biological recognition events with electronic signal transduction towards the design of powerful bioelectronic sensors.912 One-dimensional (1D) semiconductor or conducting-polymer nanowires are particularly attractive for such ele

50、ctronic detection as they lead to a label-free real-time monitoring of biomolecular interactions. Because of the high surface-to-volume ratio and novel electron-transport properties of these nanowires, their electronic conductance is strongly influenced by minor surface perturbations. Binding of tar

51、get biomolecules to receptor-functionalized semiconductor nanowires thus leads to depletion or accumulation of carriers in the “bulk” of the nanowire structure and hence to distinct conductivity signals.13 This is in contrast to planar thin-film semiconductor devices where only the surface region is

52、 influenced by the binding event. Such nanowire transducers thus offer direct label-free real-time electrical detection of bioaffinity interactions. The real-time monitoring capability is coupled with highly reversible conductivity changes upon binding (capture) and unbinding (release) of the target

53、 analyte from the surfaceconfined receptor (Figure 3).14The extreme smallness of nanowires offers also great promise for massive redundancy in nanosensor arrays. It allows packing of a huge number of nanowire sensing elements onto a small footprint for creating highly dense array devices.15 While st

54、ill facing scalability challenges, nanowires are advantageous over analogous 1D carbon nanotubes in terms of fabrication controllability and connectivity. Functionalizing the individual nanowire sensing elements with different surface receptors leads to multiplexed bioassays of different target biom

55、olecules and holds great promise for the screening of disease biomarkers.9 The pioneering work of Lieber in 200113 illustrated these capabilities in connection to the monitoring of different biomolecular interactions and using boron-doped silicon nanowires. The ability to tailor the type and level o

56、f the dopant within such semiconductor nanowires, and to control the wire diameter, has been particularly attractive for tuning their electrical properties and hence their sensitivity. Nanowire-Based DNA Detection and Assembly Functionalizing semiconductor nanowire transducers with oligonucleotide p

57、robes offers an attractive route for label-free electronic detection of DNA hybridization.1619 Liebers group modified silicon nanowires with peptide nucleic acid (PNA) receptors for detecting the gene mutation responsible for about 75% of cases of cystic fibrosis.16 Owing to the improved mismatch di

58、scrimination of PNA probes, the PNA-functionalized nanowires were able to distinguish wild-type from the DF508 mutation site in the cystic fibrosis transmembrane receptor (CFTR) gene. The PNA receptors were linked to the nanowire surface using intervening an avidin protein layer. The concept was exp

59、anded by Gao et al18 for designing PNA capture probe-functionalized Si nanowires arrays displaying a concentration- dependent resistance response over a large dynamic range with a detection limit of 10 fm. Surface immobilization was accomplished by attaching amine-terminated PNA probes to the aldehyde moieties of the silanized silicon nanowire arrays.Ozkans group17 reported on the use of