This research was financially supported by Ministry of Science and Technology, Taiwan (104-2514-S-009 -001, 104-2627-M-009-001 and 102-2311-B-009-004-MY3). We thank the National Nano Device Laboratories (NDL) for its valuable assistance during device fabrication and analysis.

1. Fabricação e Preservação de Dispositivos pSNWFET <ol><li> fabricação de dispositivos Nota: O pSNWFET foi fabricado usando uma técnica de parede lateral espaçador, como relatado anteriormente 23,24. <ol><li> Preparar a camada dieléctrica portão. <ol><li> Um tampão de óxido de 100 nm de espessura térmica (SiO 2) camada num substrato de Si utilizando o (gás de processo de O2 e H2 a 980 ° C durante 4 h) molhado processo de oxidação 25. </li><li> Depositar um nitreto de 50 nm de espessura (Si 3 N 4) camada utilizando deposição de vapor químico de baixa pressão (LPCVD) 25 a 980 ° C durante 4 h. </li></ol></li><li> Depositar uma camada de 100 nm de espessura de ortossilicato de tetraetilo (TEOS) usando LPCVD 25 a 780 ° C durante 4 h. </li><li> Realizar litografia padrão usando um deslizante I-linha para determinar as estruturas de óxido de manequim. <ol><li> Brasão superfície do wafer com uma camada fotorresistente 830-nm de espessura. </li><li> EuNSERT um photomask definido pelo padrão para o passo I-line. </li><li> Processar a exposição usando a linha I-passo (comprimento de onda: 365 nm) a uma intensidade de 1980 J à temperatura ambiente. </li><li> Desenvolver o wafer dentro de um desenvolvedor para 5 min. </li><li> Realizar o processo de ataque químico isotrópico por meio de um padrão de plasma indutivamente acoplado etcher 25 com HBr e Cl gás de plasma durante 1 min. </li></ol></li><li> Depositar uma camada de silício amorfo de 100 nm de espessura (α-Si) utilizando LPCVD 25. </li><li> Executar um passo de recozimento a 600 ° C em N2 ambiente durante 24 horas para transformar a α-Si em uma estrutura policristalina. </li><li> Íons implante de fósforo através de fonte / dreno (S / D) doping em baixa energia (5E 15 cm-2) 25. </li><li> Realizar litografia padrão usando o passo I-linha para remover a camada de poli-Si e formar a nanofios de polissilício (pSNW) 25. Nota: Repita o passo 1.1.3 para implantar dopformigas em outros do que as regiões S / D lugares com remoção de poli-Si e formam os canais parede lateral Si de uma forma auto-alinhados. </li><li> Realizar o processo de passivação (camada de óxido de 200 nm de espessura TEOS) usando LPCVD a 780 ° C durante 5 h 25. </li><li> Realizar litografia padrão usando o passo I-linha para expor os canais de nanofios e compressas de teste forma usando o processo de ataque químico de dois passos seco / húmido. <ol><li> Repita o passo 1.1.3. </li><li> Executar o processo de corrosão úmida (FHD: HF / H 2 O durante 1 min). </li></ol></li></ol></li><li> preservação wafer <ol><li> Selar o wafer em um saco de armazenamento de vácuo e armazená-lo em um armário seco eletrônico (humidade relativa &lt;40% à temperatura ambiente). </li></ol></li></ol> 2. Pré-tratamento do dispositivo <ol><li> de limpeza dispositivo <ol><li> Lave o dispositivo com acetona pura. </li><li> Sonicar (46 kHz, 80 W) do dispositivo em acetona pura durante 10 min. </li> &lt;li&gt; Sonicar (46 kHz, 80 W) do dispositivo em etanol puro (99,5%) durante 5 min. </li><li> Seque a superfície do dispositivo com azoto. </li></ol></li><li> plasma de oxigênio <ol><li> Tratar o dispositivo com o O 2 no plasma a 18 W durante 30 segundos. </li></ol></li></ol> 3. A imobilização da sonda de ADN na superfície do dispositivo <ol><li> Modificação grupo amina <ol><li> Mergulha-se o dispositivo num trietoxissilano 2,0% (3-aminopropil) (APTES) / solução de etanol durante 30 min. </li><li> Lavar o dispositivo com etanol três vezes, e depois sonicado (46 kHz, 80 W) do dispositivo em etanol durante 10 min. </li><li> Aquecer o dispositivo sobre uma placa quente a 120 ° C durante 10 minutos para criar grupos de amina em SNWs. </li></ol></li><li> Modificação grupo aldeído <ol><li> Mergulha-se o dispositivo em glutaraldeído a 12,5% durante 1 h à temperatura ambiente para criar grupos aldeído na superfície. Evitar a exposição à luz. </li><li> Lave a sagacidade dispositivoh 10 mM de tampão de fosfato de sódio (Na-PB; pH 7,0) três vezes e, em seguida, secar a superfície do dispositivo com azoto. </li></ol></li><li> Imobilização sonda de DNA <ol><li> Mergulha-se o dispositivo numa solução contendo 1 uM de sondas de ADN durante a noite. </li><li> Mergulha-se o dispositivo em tampão Tris 10 mM (pH 8,0) com mM de NaBH3CN 4,0 durante 30 minutos para bloquear os grupos aldeído que não reagiram. </li><li> Lavar o dispositivo com Na-PB (pH 7,0) três vezes e, em seguida, secar a superfície do dispositivo com azoto. </li></ol></li></ol> 4. Confirmação e análise das modificações de superfície na pSNWFET <ol><li> perfil de pH após cada etapa de modificação da superfície <ol><li> Prepare 10 mM Na-PB em pH 3,0-9,0. <ol><li> Prepare fosfato de sódio 10 mM tribásico dodeca (Na 3 PO 4) em água desionizada (pH 11,60). </li><li> Preparar 10 mM de ácido fosfórico (H 3 PO 4), em água desionizada(PH 2,35). </li><li> Colocar o eléctrodo de pH em 500 ml de Na 10 mM 3 PO tampão 4, e misturar esta solução com diferentes volumes de 10 mM H tampão 3 PO 4 enquanto se mede o valor de pH para se obter tampões com valores de pH de 3.0, 4.0, 5.0, 6.0 , 7.0, 8.0 e 9.0. </li></ol></li><li> medição de condutância AC Nota: O circuito de medição incluído um gerador de sinal AC pequeno e um Microwire Au que serviu de eletrodo de porta líquido. <ol><li> Determinar a tensão da porta de líquido óptimo (V LG) para a medição de 26 em cada etapa de modificação (passos 2.2, 3.1, 3.2, e 3.3). Nota: As propriedades eléctricas do dispositivo, depois de quatro modificações de superfície sobre o SNW foram medidos tal como descrito nesta secção. No passo 2.2, o pSNWFET não modificado contendo a camada de óxido nativa é modificada; Fase 3.1 implica a alteração do dispositivo com o grupo amina de APTES; 3.2 passo envolve a modificação com o descarregadagrupo funcional de glutaraldeído; e passo 3.3 envolve a modificação sonda de DNA. <ol><li> Entregar o mM de Na-PB 10 (pH 7,0) solução de a superfície de SNW usando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) para o contacto directo com o SNW. </li><li> Medir a condutância em tempo real do dispositivo durante a varredura V LG 0,80-1,30 V. <ol><li> Efectuar a medição da condutância usando a técnica de aprisionamento 27 à temperatura ambiente. </li><li> Converter os sinais de corrente alternada em um sinal de tensão AC usando um pré-amplificador de corrente de baixo ruído. </li><li> Recolher dados sobre a condutância (G) por aumento da V LG 0,80-1,30 V (intervalo = 0,02 V). </li></ol></li><li> Determine o LG V ideal (mais sensível V LG) do dispositivo 26. <ol><li> Traçar as curvas de passo GV LG 4.1.2.1.2.3 para obter a equação da curva. </li><li> Differentiate da equação, e calcular os valores em cada ponto de V LG. </li><li> Dividir o valor do passo 4.1.2.1.3.2 por G, e determinar o óptimo V LG de acordo com o número máximo. </li></ol></li></ol></li><li> Medir a condutância em tempo real, do perfil de pH a cada passo da modificação da superfície. <ol><li> Efectuar a medição da condutância usando a técnica de aprisionamento 27 à temperatura ambiente. </li><li> Converter o sinal de corrente AC em sinais de tensão AC usando um pré-amplificador de corrente de baixo ruído. </li><li> Defina o ideal V LG para cada etapa de modificação da superfície (passo 2.2: V LG = 1,02, passo 3.1: V LG = 0,98, passo 3.2: V LG = 0,98, e o passo 3.3: V LG = 1,0). </li><li> Fornecer a solução de 10 mM de Na-PB com valores de pH 3,0-9,0 para a superfície da SNW (taxa de fluxo: 5,0 ml / hr), E recolher os dados sobre a condutância a uma tensão de drenagem de 0,01 V. </li></ol></li></ol></li></ol></li><li> A medição das propriedades eléctricas (a curva I D -V BG) do dispositivo em 10 mM de Na-PB (pH 7,0) a seguir a cada passo de modificação de superfície (passos 2.2, 3.1, 3.2, e 3.3.) Nota: As propriedades eléctricas do dispositivo após quatro modificações de superfície na SNW foram medidos: no passo 2.2, o pSNWFET não modificado contendo a camada de óxido nativo é modificada; 3.1 passo envolve a modificação do dispositivo com o grupo amina de APTES; 3.2 passo implica a modificação com o grupo funcional não carregado de glutaraldeído; e passo 3.3 implica modificação sonda de DNA. <ol><li> Fornecer a solução à superfície da SNW mM de Na-PB 10 (pH 7,0) (passos 2.2, 3.1, 3.2, e 3.3), utilizando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) para o contacto directo com o SNW. </li><li> Medir o I D </em&gt; Do dispositivo (passos 2.2, 3.1, 3.2, e 3.3), utilizando um analisador semicondutor comercial e de software. <ol><li> Selecione o modo &quot;nMOSFET&quot;. </li><li> Selecione &quot;I D - V BG&quot; módulos. Nota: I D é a corrente de dreno / source e V BG é a tensão da porta de trás. </li><li> Definir uma tensão de polarização constante (V D = 0,5 V), enquanto varrendo o portão potencial (V BG) de -1 a 3,0 V (intervalo = 0,2 V). </li><li> Clique no ícone Executar para obter I D - Curvas V BG. </li></ol></li></ol></li></ol> 5. DNA Biossensoriais Nota: Em um experimento típico, o I D - V curva B G é determinado por três vezes para garantir que nenhuma outra variação é OBSErved. <ol><li> A determinação da linha de base <ol><li> Fornecer a solução de 10 mM de Na-PB (pH 7,0) à superfície imobilizada SNW-sonda o ADN durante 10 minutos usando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) e, depois incubar a SNW durante 30 min. </li><li> Medir o I D do dispositivo (repita o passo 4.2.2). </li></ol></li><li> Sentindo de DNA de hibridização / DNA <ol><li> Carga 22:00 ADN alvo complementar na superfície SNW o ADN imobilizado-sonda durante 10 minutos usando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) e, depois incubar a SNW durante 30 min. </li><li> Entregar a solução de 10 mM de Na-PB (pH 7,0) sobre a superfície de SNW durante 10 min, utilizando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) para lavar o ADN alvo não ligadas longe. </li><li> Repetir o passo 4.2.2 para medir o I D do dispositivo. </li></ol></li><li> Reconfirmar o sinal de hibridação ADN / ADN. <ol><li> Carga 1 nM DNA recuperação em tele ADN sonda imobilizado superfície SNW durante 10 min, utilizando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) e, depois incubar a SNW durante 30 min. </li><li> Entregar a solução de 10 mM de Na-PB (pH 7,0) sobre a superfície de SNW durante 10 min, utilizando uma bomba de seringa (taxa de fluxo: 5,0 ml / h). </li><li> Repetir o passo 4.2.2 para medir o I D do dispositivo. </li></ol></li><li> O controlo negativo <ol><li> Carga de 100 pM de ADN não-complementar na superfície SNW o ADN imobilizado-sonda durante 10 minutos usando uma bomba de seringa (taxa de fluxo: 5,0 ml / h) e, depois incubar a SNW durante 30 min. </li><li> Entregar a solução de 10 mM de Na-PB (pH 7,0) sobre a superfície de SNW durante 10 min, utilizando uma bomba de seringa (taxa de fluxo: 5,0 ml / h). </li><li> Repetir o passo 4.2.2 para medir o I D do dispositivo. </li></ol></li></ol>

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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+titrations+and+ionization+state+sensitive+imaging+of+functional+groups+in+aqueous+solutions+by+chemical+force+microscopy.">Force titrations and ionization state sensitive imaging of functional groups in aqueous solutions by chemical force microscopy.</a> J Am Chem Soc. 119, 2006-2015 (1997).</li><li>Townsend, M. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+evaluation+of+the+FluChip+diagnostic+microarray+for+influenza+virus+surveillance.">Experimental evaluation of the FluChip diagnostic microarray for influenza virus surveillance.</a> J Clin Microbiol. 44, 2863-2871 (2006).</li><li>Wang, L. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+detection+and+differentiation+of+Newcastle+disease+and+avian+influenza+viruses+using+oligonucleotide+microarrays.">Simultaneous detection and differentiation of Newcastle disease and avian influenza viruses using oligonucleotide microarrays.</a> Vet Microbiol. 127, 217-226 (2008).</li><li>Lin, C. -. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recovery+Based+Nanowire+Field-Effect+Transistor+Detection+of+Pathogenic+Avian+Influenza+DNA.">Recovery Based Nanowire Field-Effect Transistor Detection of Pathogenic Avian Influenza DNA.</a> Jpn J Appl Phys. 51 (02BL02), (2012).</li><li>Lee, K. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Well+controlled+assembly+of+silicon+nanowires+by+nanowire+transfer+method.">Well controlled assembly of silicon nanowires by nanowire transfer method.</a> Nanotechnology. 18 (445302), (2007).</li><li>Li, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequence-specific+label-free+DNA+sensors+based+on+silicon+nanowires.">Sequence-specific label-free DNA sensors based on silicon nanowires.</a> Nano Lett. 4, 245-247 (2004).</li><li>McAlpine, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-performance+nanowire+electronics+and+photonics+on+glass+and+plastic+substrates.">High-performance nanowire electronics and photonics on glass and plastic substrates.</a> Nano Lett. 3, 1531-1535 (2003).</li><li>Cui, Y., Wei, Q., Park, H., Lieber, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanowire+nanosensors+for+highly+sensitive+and+selective+detection+of+biological+and+chemical+species.">Nanowire nanosensors for highly sensitive and selective detection of biological and chemical species.</a> Science. 293, 1289-1292 (2001).</li><li>Patolsky, F., Zheng, G., Lieber, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanowire-based+biosensors.">Nanowire-based biosensors.</a> Anal Chem. 78, 4260-4269 (2006).</li><li>Hsiao, C. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+poly-silicon+nanowire+field+effect+transistor+for+biosensing+application.">Novel poly-silicon nanowire field effect transistor for biosensing application.</a> Biosens Bioelectron. 24, 1223-1229 (2009).</li></ol>

The authors have nothing to disclose.

Comercializar o top-down e fabricação de baixo para cima abordagens para sSNWFETs é considerado difícil por causa de seu custo de 32,33, SNW controle de posição 34,35, e sua escala de 36 baixa produção. Por outro lado, a fabricação pSNWFETs é o custo simples e de baixo 37. Através da abordagem de cima para baixo e combinação com a técnica de formação de parede lateral espaçador (Figura 1), o tamanho da SNW pode ser controlada ajustando a dura...

nanofios de silício transistores de efeito de campo (SNWFETs) têm as vantagens de ultra-alta sensibilidade e respostas elétricas diretos variação de carga ambiental. Em SNWFETs tipo n, por exemplo, quando uma molécula negativamente (ou positivamente) carregado aproxima-se do nanofio de silício (SNW), os transportadores em SNW estão esgotados (ou acumular). Por conseguinte, a condutividade da SNWFET diminui (ou aumenta) 1. Portanto, qualquer molécula carregada perto da superfície da SNW do dispositivo SNWFET pode ser detectada. biomoléculas vitais, incluindo enzimas, proteínas, nucleótidos, e muitas moléculas na superfície celular são portadores de carga e pode ser monitorizada utilizando SNWFETs. Com modificações adequadas, particularmente imobilizar uma sonda biomolecular na SNW, um SNWFET pode ser desenvolvida em um biossensor sem rótulo. Vigilância utilizando biomarcadores é fundamental para o diagnóstico de doenças. Como mostrado na Tabela 1, vários estudos têm utilizado NWFEBiosensores baseados em T para livre-label, ultra-alta-sensibilidade e detecção em tempo real de vários alvos biológicos, incluindo um único vírus 2, trifosfato de adenosina quinase e de ligação 3, sinais neuronais 4, íons metálicos 5,6, toxinas bacterianas 7, de dopamina 8, DNA 9-11, RNA 12,13, enzimas e biomarcadores de câncer 14-19, hormônios humanos 20, e citocinas 21,22. Estes estudos demonstraram que biossensores baseados em NWFET representam uma plataforma de detecção poderosa para uma ampla gama de espécies biológicas e químicas em solução. Em biossensores baseados em SNWFET, a sonda imobilizada na superfície do dispositivo SNW reconhece um biotarget específica. Imobilização de uma bioprobe geralmente envolve uma série de etapas, e é fundamental que cada etapa é realizada adequadamente para garantir o bom funcionamento do biossensor. Várias técnicas têm sido desenvolvidas para analisar os scomposição urface, incluindo espectroscopia de raios-X de fotoelétrons (XPS), elipsometria, medição do ângulo de contato, microscopia de força atômica (AFM) e microscopia eletrônica de varredura (MEV). Métodos como a AFM e SEM fornecem evidência direta de imobilização bioprobe no dispositivo de nanofios, enquanto que métodos como XPS, elipsometria, e medição do ângulo de contato são dependentes de experimentos paralelos realizados em outros materiais similares. Neste relatório, nós descrevemos a confirmação de cada passo de modificação usando dois métodos independentes. XPS é usado para examinar as concentrações de átomos específicos sobre hóstias de silício policristalino, e as variações nas propriedades eléctricas do dispositivo são medidos directamente para confirmar a variação de carga na superfície do SNW. Nós empregamos biosensing DNA usando SNWFETs policristalinos (pSNWFETs) como um exemplo para ilustrar este protocolo. Imobilizar uma sonda de ADN na superfície da SNW envolve três passos: a modificação do grupo amina na superfície hidroxilo nativo do SNW, almodificação grupo dehyde, e 5&#39;-aminomodified imobilização sonda de DNA. Em cada etapa de modificação, o dispositivo pode detectar directamente a variação da carga do grupo funcional imobilizada na superfície do SNW, porque as cargas superficiais causar alterações potenciais locais interfacial através do dieléctrico portão que altera a corrente e a condutância do canal 1. Encargos que cercam a superfície de SNW pode eletricamente modular as propriedades eléctricas do dispositivo pSNWFET; por conseguinte, as propriedades de superfície do SNW desempenhar um papel crucial na determinação das características eléctricas dos dispositivos pSNWFET. Nos processos descritos, a imobilização de um bioprobe na superfície do SNW pode ser determinada directamente e confirmada através da medição eléctrico, e o dispositivo está preparado para aplicações biosensoriamento.

<table border="0" cellpadding="0" cellspacing="0" width="862">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Acetone</td>
			<td style="width:191px;">ECHO</td>
			<td style="width:179px;">AH-3102</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:327px;">(3-Amonopropyl)triethoxysilane (APTES), &#8805;98%</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;">A3648</td>
			<td>Danger</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Ethanol, anhydrous, 99.5%</td>
			<td style="width:191px;">ECHO</td>
			<td style="width:179px;">484000203108A-72EC</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Glutaraldehyde solution (GA), 50%</td>
			<td style="width:191px;">Sigma-Aldrich</td>
			<td style="width:179px;">G7651</td>
			<td>Avoid light</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Sodium cyanoborohydride, &#8805;95.0%&#160;</td>
			<td style="width:191px;">Fluka</td>
			<td style="width:179px;">71435</td>
			<td>Danger and deliquescent</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:327px;">Sodium phosphate tribasic dodecahydrate, &#8805;98%</td>
			<td style="width:191px;">Sigma</td>
			<td style="width:179px;">04277</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Phosphoric acid, &#8805;99.0%</td>
			<td style="width:191px;">Fluka</td>
			<td style="width:179px;">79622</td>
			<td>Deliquescent</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Photoresist (iP3650)</td>
			<td style="width:191px;">Tokyo Ohka Kogyo Co., LTD</td>
			<td style="width:179px;">THMR-iP3650 HP</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Synthetic oligonucleotides, HPLC purified</td>
			<td style="width:191px;">Protech Technology</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:327px;">Tris(hydroxymethyl)aminomethane (Tris), &#8805;99.8%</td>
			<td style="width:191px;">USB</td>
			<td style="width:179px;">75825</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Keithley 2636 System SourceMeter</td>
			<td style="width:191px;">Keithley</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:327px;">SR830 DSP Lock-In Amplifier</td>
			<td style="width:191px;">Stanford Research Systems</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:327px;">SR570 Low-noise Current Preamplifier</td>
			<td style="width:191px;">Stanford Research Systems</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:327px;">Ni PXI Express</td>
			<td style="width:191px;">National Instruments</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of silicon nanowire field-effect transistor for chemical and biosensing applications

Surveillance using biomarkers is critical for the early detection, rapid intervention, and reduction in the incidence of diseases. In this study, we describe the preparation of polycrystalline silicon nanowire field-effect transistors (pSNWFETs) that serve as biosensing devices for biomarker detection. A protocol for chemical and biomolecular sensing by using pSNWFETs is presented. The pSNWFET device was demonstrated to be a promising transducer for real-time, label-free, and ultra-high-sensitivity biosensing applications. The source/drain channel conductivity of a pSNWFET is sensitive to changes in the environment around its silicon nanowire (SNW) surface. Thus, by immobilizing probes on the SNW surface, the pSNWFET can be used to detect various biotargets ranging from small molecules (dopamine) to macromolecules (DNA and proteins). Immobilizing a bioprobe on the SNW surface, which is a multistep procedure, is vital for determining the specificity of the biosensor. It is essential that every step of the immobilization procedure is correctly performed. We verified surface modifications by directly observing the shift in the electric properties of the pSNWFET following each modification step. Additionally, X-ray photoelectron spectroscopy was used to examine the surface composition following each modification. Finally, we demonstrated DNA sensing on the pSNWFET. This protocol provides step-by-step procedures for verifying bioprobe immobilization and subsequent DNA biosensing application.

Vários SNWFETs têm sido relatados para servir como transdutores de biossensores (Tabela 1). SNWFETs monocristalino (sSNWFETs) e pSNWFETs mostrar propriedades elétricas comparáveis ​​como transdutores em soluções aquosas, e ambos foram relatados para ter muitas aplicações biosensoriamento. Uma característica vantajosa do dispositivo de pSNWFET usado neste estudo é a sua procedimento simples e fabricação de baixo custo. A Figura 1a mostra o...

Watch this Scientific Journal Video about Preparation of Silicon Nanowire Field-effect Transistor for Chemical and Biosensing Applications at JoVE.com

Preparation of Silicon Nanowire Field-effect Transistor for Chemical and Biosensing Applications

We describe key steps for biosensing by using polysilicon nanowire field-effect transistors, including the preparation of the device and the immobilization and confirmation of a DNA molecular probe on the nanowire surface, as well as conditions for DNA sensing.

Preparação de Silicon Nanowire transistor de efeito de campo para aplicações químicas e Biossensoriais

Surveillance using biomarkers is critical for the early detection, rapid intervention, and reduction in the incidence of diseases. In this study, we ...

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11.0K visualizações.  National Chiao Tung University. We describe key steps for biosensing by using polysilicon nanowire field-effect transistors, including the preparation of the device and the immobilization and confirmation of a DNA molecular probe on the nanowire surface, as well as conditions for DNA sensing.

Vídeo: Preparation of Silicon Nanowire Field-effect Transistor for Chemical and Biosensing Applications

Soft Lithographic Functionalization and Patterning Oxide-free Silicon and Germanium

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a stable interface that permits efficient electron transport and protects underlying substrates from oxidative degradation. Group IV semiconductors can be effectively protected with highly-ordered self-assembled monolayers (SAMs) composed of simple alkyl chains that act as impervious barriers to both organic and aqueous solutions. Simple alkyl SAMs, however, are inert and not amenable to traditional patterning techniques. The motivation for immobilizing organic molecular systems on semiconductors is to impart new functionality to the surface that can provide optical, electronic, and mechanical function, as well as chemical and biological activity. 
Microcontact printing (&mu;CP) is a soft-lithographic technique for patterning SAMs on myriad surfaces.1-9 Despite its simplicity and versatility, the approach has been largely limited to noble metal surfaces and has not been well developed for pattern transfer to technologically important substrates such as oxide-free silicon and germanium. Furthermore, because this technique relies on the ink diffusion to transfer pattern from the elastomer to substrate, the resolution of such traditional printing is essentially limited to near 1 &mu;m.10-16
In contrast to traditional printing, inkless &mu;CP patterning relies on a specific reaction between a surface-immobilized substrate and a stamp-bound catalyst. Because the technique does not rely on diffusive SAM formation, it significantly expands the diversity of patternable surfaces. In addition, the inkless technique obviates the feature size limitations imposed by molecular diffusion, facilitating replication of very small (&lt;200 nm) features.17-23 However, up till now, inkless &mu;CP has been mainly used for patterning relatively disordered molecular systems, which do not protect underlying surfaces from degradation.
Here, we report a simple, reliable high-throughput method for patterning passivated silicon and germanium with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The technique utilizes a preformed NHS-reactive bilayered system on oxide-free silicon and germanium. The NHS moiety is hydrolyzed in a pattern-specific manner with a sulfonic acid-modified acrylate stamp to produce chemically distinct patterns of NHS-activated and free carboxylic acids. A significant limitation to the resolution of many &mu;CP techniques is the use of PDMS material which lacks the mechanical rigidity necessary for high fidelity transfer. To alleviate this limitation we utilized a polyurethane acrylate polymer, a relatively rigid material that can be easily functionalized with different organic moieties. Our patterning approach completely protects both silicon and germanium from chemical oxidation, provides precise control over the shape and size of the patterned features, and gives ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. The approach is general and applicable to other technologically-relevant surfaces.

Here we describe a simple method for patterning oxide-free silicon and germanium with reactive organic monolayers and demonstrate functionalization of the patterned substrates with small molecules and proteins. The approach completely protects surfaces from chemical oxidation, provides precise control over feature morphology, and provides ready access to chemically discriminated patterns.

Funcionalização litografia macia e livre de óxido Patterning silício e germânio

The development of hybrid electronic devices relies in large part on the integration of (bio)organic materials and inorganic semiconductors through a ...

Bioengenharia

Preparation of 3D Fibrin Scaffolds for Stem Cell Culture Applications

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells inside of 3D biomaterial scaffolds provides a way to accurately mimic these microenvironments, providing an advantage over traditional 2D culture methods using polystyrene as well as a method for engineering replacement tissues 2. While 2D tissue culture polystrene has been used for the majority of cell culture experiments, 3D biomaterial scaffolds can more closely replicate the microenvironments found in vivo by enabling more accurate establishment of cell polarity in the environment and possessing biochemical and mechanical properties similar to soft tissue.3 A variety of naturally derived and synthetic biomaterial scaffolds have been investigated as 3D environments for supporting stem cell growth. While synthetic scaffolds can be synthesized to have a greater range of mechanical and chemical properties and often have greater reproducibility, natural biomaterials are often composed of proteins and polysaccharides found in the extracelluar matrix and as a result contain binding sites for cell adhesion and readily support cell culture. Fibrin scaffolds, produced by polymerizing the protein fibrinogen obtained from plasma, have been widely investigated for a variety of tissue engineering applications both in vitro and in vivo 4. Such scaffolds can be modified using a variety of methods to incorporate controlled release systems for delivering therapeutic factors 5. Previous work has shown that such scaffolds can be used to successfully culture embryonic stem cells and this scaffold-based culture system can be used to screen the effects of various growth factors on the differentiation of the stem cells seeded inside 6,7.
 This protocol details the process of polymerizing fibrin scaffolds from fibrinogen solutions using the enzymatic activity of thrombin. The process takes 2 days to complete, including an overnight dialysis step for the fibrinogen solution to remove citrates that inhibit polymerization. These detailed methods rely on fibrinogen concentrations determined to be optimal for embryonic and induced pluripotent stem cell culture. Other groups have further investigated fibrin scaffolds for a wide range of cell types and applications - demonstrating the versatility of this approach 8-12.

This work details the preparation of 3D fibrin scaffolds for culturing and differentiating plutipotent stem cells. Such scaffolds can be used to screen the effects of various biological compounds on stem cell behavior as well as modified to contain drug delivery systems.

Preparação de fibrina Andaimes 3D para aplicações de cultura de células-tronco

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells ...

Porous Silicon Microparticles for Delivery of siRNA Therapeutics

Small interfering RNA (siRNA) can be used to suppress gene expression, thereby providing a new avenue for the treatment of various diseases. However, the successful implementation of siRNA therapy requires the use of delivery platforms that can overcome the major challenges of siRNA delivery, such as enzymatic degradation, low intracellular uptake and lysosomal entrapment. Here, a protocol for the preparation and use of a biocompatible and effective siRNA delivery system is presented. This platform consists of polyethylenimine (PEI) and arginine (Arg)-grafted porous silicon microparticles, which can be loaded with siRNA by performing a simple mixing step. The silicon particles are gradually degraded over time, thereby triggering the formation of Arg-PEI/siRNA nanoparticles. This delivery vehicle provides a means for protecting and internalizing siRNA, without causing cytotoxicity. The major steps of polycation functionalization, particle characterization, and siRNA loading are outlined in detail. In addition, the procedures for determining particle uptake, cytotoxicity, and transfection efficacy are also described.

Delivery remains the main challenge for the therapeutic implementation of small interfering RNA (siRNA). This protocol involves the use of a multifunctional and biocompatible siRNA delivery platform, consisting of arginine and polyethylenimine grafted porous silicon microparticles.

Porous Silicon micropartículas para entrega de siRNA Therapeutics

Small interfering RNA (siRNA) can be used to suppress gene expression, thereby providing a new avenue for the treatment of various diseases. However, the ...

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy.
The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

We present a protocol for the synthesis of RGD-functionalized hydrogels as devices for cell and drug delivery. The procedure involves copper catalyzed alkyne-azide cycloaddition (CuAAC) between alkyne-modified polyacrylic acid (PAA) and a RGD-azide derivative. The hydrogels are formed using microwave-assisted polycondensation and their physicochemical properties are investigated.

A Síntese de hidrogéis RGD-funcionalizado como uma ferramenta para aplicações terapêuticas

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Formação Light-mediada e padronização de hidrogéis para aplicações de cultura celular

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

Extraction of Plant-based Capsules for Microencapsulation Applications

Microcapsules derived from plant-based spores or pollen provide a robust platform for a diverse range of microencapsulation applications. Sporopollenin exine capsules (SECs) are obtained when spores or pollen are processed so as to remove the internal sporoplasmic contents. The resulting hollow microcapsules exhibit a high degree of micromeritic uniformity and retain intricate microstructural features related to the particular plant species. Herein, we demonstrate a streamlined process for the production of SECs from Lycopodium clavatum spores and for the loading of hydrophilic compounds into these SECs. The current SEC isolation procedure has been recently optimized to significantly reduce the processing requirements which are conventionally used in SEC isolation, and to ensure the production of intact microcapsules. Natural L. clavatum spores are defatted with acetone, treated with phosphoric acid, and extensively washed to remove sporoplasmic contents. After acetone defatting, a single processing step using 85% phosphoric acid has been shown to remove all sporoplasmic contents. By limiting the acid processing time to 30 hr, it is possible to isolate clean SECs and avoid SEC fracturing, which has been shown to occur with prolonged processing time. Extensive washing with water, dilute acids, dilute bases, and solvents ensures that all sporoplasmic material and chemical residues are adequately removed. The vacuum loading technique is utilized to load a model protein (Bovine Serum Albumin) as a representative hydrophilic compound. Vacuum loading provides a simple technique to load various compounds without the need for harsh solvents or undesirable chemicals which are often required in other microencapsulation protocols. Based on these isolation and loading protocols, SECs provide a promising material for use in a diverse range of microencapsulation applications, such as, therapeutics, foods, cosmetics, and personal care products.

This protocol/manuscript describes a streamlined process for the production of sporopollenin exine capsules (SECs) from Lycopodium clavatum spores and for the loading of hydrophilic compounds into these SECs.

Cápsulas à base de plantas de extração de para aplicações de microencapsulação

Microcapsules derived from plant-based spores or pollen provide a robust platform for a diverse range of microencapsulation applications. Sporopollenin ...

Rapid Mix Preparation of Bioinspired Nanoscale Hydroxyapatite for Biomedical Applications

Hydroxyapatite (HA) has been widely used as a medical ceramic due to its good biocompatibility and osteoconductivity. Recently there has been interest regarding the use of bioinspired nanoscale hydroxyapatite (nHA). However, biological apatite is known to be calcium-deficient and carbonate-substituted with a nanoscale platelet-like morphology. Bioinspired nHA has the potential to stimulate optimal bone tissue regeneration due to its similarity to bone and tooth enamel mineral. Many of the methods currently used to fabricate nHA both in the laboratory and commercially, involve lengthy processes and complex equipment. Therefore, the aim of this study was to develop a rapid and reliable method to prepare high quality bioinspired nHA. The rapid mixing method developed was based upon an acid-base reaction involving calcium hydroxide and phosphoric acid. Briefly, a phosphoric acid solution was poured into a calcium hydroxide solution followed by stirring, washing and drying stages. Part of the batch was sintered at 1,000 &#176;C for 2 h in order to investigate the products&#39; high temperature stability. X-ray diffraction analysis showed the successful formation of HA, which showed thermal decomposition to &#946;-tricalcium phosphate after high temperature processing, which is typical for calcium-deficient HA. Fourier transform infrared spectroscopy showed the presence of carbonate groups in the precipitated product. The nHA particles had a low aspect ratio with approximate dimensions of 50 x 30 nm, close to the dimensions of biological apatite. The material was also calcium deficient with a Ca:P molar ratio of 1.63, which like biological apatite is lower than the stoichiometric HA ratio of 1.67. This new method is therefore a reliable and far more convenient process for the manufacture of bioinspired nHA, overcoming the need for lengthy titrations and complex equipment. The resulting bioinspired HA product is suitable for use in a wide variety of medical and consumer health applications.

This paper describes a novel method for the rapid manufacture of high quality bioinspired nanoscale hydroxyapatite. This biomaterial is of great significance in the manufacture of a wide range of innovative medical devices for clinical applications in orthopedics, craniofacial surgery and dentistry.

Rápido Mix Preparação de Bioinspirada Nanoscale hidroxiapatita para aplicações biomédicas

Hydroxyapatite (HA) has been widely used as a medical ceramic due to its good biocompatibility and osteoconductivity. Recently there has been interest ...

Rapid Fabrication of Custom Microfluidic Devices for Research and Educational Applications

Microfluidic devices allow for the manipulation of fluids, particles, cells, micro-sized organs or organisms in channels ranging from the nano to submillimeter scales. A rapid increase in the use of this technology in the biological sciences has prompted a need for methods that are accessible to a wide range of research groups. Current fabrication standards, such as PDMS bonding, require expensive and time consuming lithographic and bonding techniques. A viable alternative is the use of equipment and materials that are easily affordable, require minimal expertise and allow for the rapid iteration of designs. In this work we describe a protocol for designing and producing PET-laminates (PETLs), microfluidic devices that are inexpensive, easy to fabricate, and consume significantly less time to generate than other approaches to microfluidics technology. They consist of thermally bonded film sheets, in which channels and other features are defined using a craft cutter. PETLs solve field-specific technical challenges while dramatically reducing obstacles to adoption. This approach facilitates the accessibility of microfluidics devices in both research and educational settings, providing a reliable platform for new methods of inquiry.

Here we present a protocol to design and fabricate custom microfluidic devices with minimal financial and time investment. The aim is to facilitate the adoption of microfluidic technologies in biomedical research laboratories and educational settings.

Fabricação rápida de dispositivos microfluídicos personalizados para pesquisa e aplicações educacionais

Microfluidic devices allow for the manipulation of fluids, particles, cells, micro-sized organs or organisms in channels ranging from the nano to ...

Synthesis of Near-Infrared Emitting Gold Nanoclusters for Biological Applications

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been devoted to their development. In this protocol, a recently developed, facile method for preparation of water soluble, biocompatible, and colloidally stable near-infrared emitting AuNCs have been described in detail. This room-temperature, bottom-up chemical synthesis provides easily functionalizable AuNCs capped with thioctic acid and thiol-modified polyethylene glycol in aqueous solution. The synthetic approach requires neither organic solvents or additional ligand exchange nor extensive knowledge of synthetic chemistry to reproduce. The resulting AuNCs offer free surface carboxylic acids, which can be functionalized with various biological molecules bearing a free amine group without adversely affecting the photoluminescent properties of the AuNCs. A quick, reliable procedure for flow cytometric quantification and confocal microscopic imaging of AuNC uptake by HeLa cells also been described. Due to the large Stokes shift, proper setting of filters in flow cytometry and confocal microscopy is necessary for efficient detection of near-infrared photoluminescence of AuNCs.

A reliable and easily reproducible method for preparation of functionalizable, near-infrared emitting photoluminescent gold nanoclusters and their direct detection inside HeLa cells by flow cytometry and confocal laser scanning microscopy is described.

Síntese de nanoaglomerados de ouro emissor próximos para aplicações biológicas

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been ...

Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications

These methods describe how to formulate injectable, supramolecular polymer-nanoparticle (PNP) hydrogels for&#160;use as biomaterials. PNP hydrogels are composed of two components: hydrophobically modified cellulose as the network polymer and self-assembled core-shell nanoparticles that act as non-covalent cross linkers through dynamic, multivalent interactions. These methods describe both the formation of these self-assembled nanoparticles through nanoprecipitation as well as the formulation and mixing of the two components to form hydrogels with tunable mechanical properties. The use of dynamic light scattering (DLS) and rheology to characterize the quality of the synthesized materials is also detailed. Finally, the utility of these hydrogels for drug delivery, biopharmaceutical stabilization, and cell encapsulation and delivery is demonstrated through in vitro experiments to characterize&#160;drug release, thermal stability, and cell settling and viability. Due to its biocompatibility, injectability, and mild gel formation conditions, this hydrogel system is a readily tunable platform suitable for a range of biomedical applications.

This protocol describes the synthesis and formulation of injectable, supramolecular polymer-nanoparticle (PNP) hydrogel biomaterials. Applications of these materials for drug delivery, biopharmaceutical stabilization, and cell encapsulation and delivery are demonstrated.

Hidrogéis de polímero supramolecular injetável para aplicações de entrega de células e medicamentos

These methods describe how to formulate injectable, supramolecular polymer-nanoparticle (PNP) hydrogels for&#160;use as biomaterials. PNP hydrogels are ...