O trabalho aqui relatado foi apoiada por doações da Auburn University AUDFS e USAF CRADA 07-277-60MDG-01. As opiniões expressas neste artigo são de responsabilidade dos autores e não refletem a política oficial ou a posição da Força Aérea dos EUA, Departamento de Defesa, ou do Governo dos EUA.

1. Ajustando o estágio <ol><li> Obter estirpe S. aureus ATCC 12600, S. aureus ATCC 27690 e Bacillus subtilis ATCC 6051. Cepas resistentes à meticilina de S. aureus - MRSA1, MRSA 2, MRSA 5, MRSA 13 de MRSA 26 de MRSA 34, MRSA 45, B. anthracis Sterne, Salmonella typhimurium LT2, Shigella flexneri, Yersinia enterocolotica, Proteus mirabilis, Klebsiella pneumoniae 13.882, o fago lítico 12600. </li><li> Obter anticorpos de PBP 2a de pérolas de látex conjugadas. </li><li> Prepara NZY meio como descrito 21. </li><li> Obter uma solução salina tamponada com fosfato (PBS). </li><li> Prepare água deionizada como subfase de Langmuir-Blodgett (LB) deposição monocamada. </li></ol> 2. Propagação bacteriófago e Titulação <ol><li> Incubar 5 ml de cultura de uma noite de S. aureus ATCC 12600 (3,6 x 10 8 unidades formadoras de colónias (CFU) / ml) com 500 ul de fagos (3 x 10 9 &lt;/ Sup&gt; UFP / ml) em 500 ml de meio NZY em 2 L em agitador Flack-incubadora a 37 ° C durante a noite. </li><li> Centrifugar cultura em 4424 xg durante 10 min a 4 ° C. </li><li> Sobrenadante re-centrifugado a 11.325 xg durante 10 min a 4 ° C. </li><li> Filtrar o sobrenadante através de um filtro Millipore de 0,22. </li><li> Centrifugar o filtrado a 75.395 g durante 1,5 horas. </li><li> Dissolve-se o pellet em 100 ul de água destilada. </li><li> Preparar diluições de 10 vezes de suspensão de fagos em meio NZY. </li><li> Placa 1 ml de cultura overnight (ON) de S. aureus ATCC 12600 em cada uma das duas placas com agar NZY para certificar-se toda a superfície é coberta. Remover o excesso de cultura e deixe seca a superfície durante 30 minutos. </li><li> Manchar uma amostra (10 ul) da diluição de fago apropriado sobre a superfície da placa e incubar a 37 ° C durante 18-24 horas. </li><li> Examinar a formação de placas e calcular o título do fago. Os títulos de bacteriófagos (t) são calculadas na base da quantidade de pLaques (N) formada por 10 mL de volume (v), da suspensão de fagos e o factor de diluição (F). O título foi calculado pela fórmula:. T = N / (VXF) Por exemplo, para o número de placas de diluição de 75 a 10 -7 e o volume de 10 ul (10 -3 x 10 ml), a titulação é igual 75 / (10 x 10 x 10 -3 -7) = 7,5 x 10 10 unidades formadoras de placas (PFU) por ml de suspensão. </li></ol> 3. O fago imobilizado e ouro <ol><li> Limpeza peças de quartzo revestidos com ouro (60 mm 2) no plasma por gravura em atmosfera de árgon durante 10 min e, em seguida esterilizar por 6 horas sob luz UV num armário estéril. </li><li> Adicionar 50 microlitros de 1 x 10 9 UFP / ml de suspensão de fago com a superfície de ouro de cada peça numa placa de Petri estéril e incubar durante a noite numa câmara húmida à temperatura ambiente. </li><li> Remover e titule a suspensão de fagos restantes. </li><li> Lave as peças com fago ligado 5 vezes com PBS para remover desacopladofago. </li></ol> 4. Ensaio de infecciosidade do fago imobilizado sobre uma superfície seca <ol><li> Espalhe uma cultura de O / N de S. Aureus ATCC 12600 em uma placa de ágar NZY e permitir secagem. </li><li> Coloque um pedaço de ouro com fago imobilizada sobre a face da placa para baixo. </li><li> Observar uma zona de lise após 12 horas de incubação a 37 ° C que indica a infectividade. </li><li> Use peças cobertas de ouro sem fago em experimentos de controle. </li></ol> 5. Testes de atividade lítica de Phage livre e ligada em líquido <ol><li> Adicionar uma cultura ON da S. aureus ATCC 12600-10 ml de NZY em cada dos quatro balões de 300 ml sidearm (6 x 10 6 CFU / mL em cada frasco). </li><li> Adicionar Em dois frascos de 2 x 10 6 PFU / ml de fago livre. </li><li> Use os outros dois frascos como controles. </li><li> Monitorizar a evoluo no tempo de S. lise celular aureus para 570 min por medição da densidade óptica (DO 600) em intervalos de 30 min para todos os frascos.</li><li> Dê uma medição final às 24 horas. </li><li> Repita os passos de 5,1-5,5, mas usar peças de ouro com fagos ligados ao invés de fagos livres, e peças de ouro sem fago em frascos de controle. </li></ol> 6. Perda de fagos ligados durante a incubação <ol><li> Adicionar 50 ul de 1 x 10 9 UFP / ml de fago na superfície do pedaço de ouro estéril numa placa de Petri que está colocado numa câmara húmida durante a noite à temperatura ambiente. </li><li> Retirar a suspensão de fagos não ligados com a superfície de ouro e titulação. </li><li> Lava-se a peça de ouro com os fagos ligados cinco vezes com PBS e coloque em 1 ml de solução de NZY em tubo de 15 ml, agitador em incubadora a 37 ° C durante 8 horas. </li><li> Determinar o título do fago isolada como descrito em 2. </li></ol> 7. Fago Spheroids Preparação <ol><li> Combinando 400 ul de estoque de fago 12600 suspensão (10 11 UFP / ml) com um volume igual de clorofórmio espectrofotométrica grau em 1 ml frascoà temperatura ambiente. </li><li> Gentilmente vórtice a suspensão de fagos-clorofórmio 5-6 vezes (intervalos de 5 seg) ao longo de um minuto de duração. </li><li> Permitiu a suspensão para estabilizar por 30 segundos e, em seguida, pipeta da fase superior contendo esferóides foi pipetado off para a preparação monocamada. </li><li> Dedique alguns microlitros da suspensão esferóides para a transmissão e microscopia eletrônica de varredura. </li><li> Use uma suspensão esferóide restante para a fabricação de biossensores. </li></ol> 8. Preparação Biosensor <ol><li> Limpe os sensores QCM-D por plasma de gravura em argônio por 10 min PDC-32G Harrick limpo plasma. </li><li> Lavar o sensor com hexano para remover as impurezas orgânicas. </li><li> Preparar e limpar a calha do saldo filme conforme descrito em 22. </li><li> Preencha através LB com uma solução subfase e limpá-lo com uma barreira de cocho e estabilizar a calha a 20 ± 0,1 ° C </li><li> Espalhe aliquota de 300 ul de fago 12600 em suspensi aquosoem (10 11 PFU / ml) na subfase LB. </li><li> Prepare monocamada fago para solução subfase LB, permitindo que 300 mL alíquota de fago suspensão aquosa 12.600 (10 11 PFU / ml) de atropelar um bastão de vidro wettable inclinado que está parcialmente submerso na subfase 22,23. </li><li> Estabilizar a monocamada preparada durante 10 minutos e, em seguida comprimi-lo a uma velocidade de 30 mm / min (45 cm 2 / min), a uma pressão constante até que 19 N / m é atingido. </li><li> Executar uma película de deposição vertical sobre o sensor posicionado perpendicular QCM-D a uma velocidade de 4,5 mm / min por meio de imersão do sensor sucessivamente dentro e fora da monocamada de sete vezes. A microscopia electrónica de depositadas monocamadas de fagos antes da exposição a bactérias amostras mostrou que as camadas eram contínuos, homogéneo e uniforme (dados não mostrados). </li><li> Repita os passos de 4,5-4,8 com uma suspensão de esferóide fago que é preparada em 3. </li><li> Use biossensores fago fabricados para detecção de MRSA, o elétronA microscopia e elipsometria. </li></ol> 9. Teste Biosensor, Discriminação de resistente à meticilina e bactérias Staphylococcus sensíveis <ol><li> Neste protocolo, biossensores com fago não modificada e modificada e esferóides fago estão preparados. Um microbalança de cristal de quartzo, com quatro câmaras de fluxo do sensor é usado para monitorar a ligação de bactérias para o fago imobilizados na superfície do sensor de QCM. PBP 2a de pérolas de látex de anticorpos conjugados são utilizados para discriminar entre resistente à meticilina (MRSA), estafilococos e bactérias sensíveis. Todas as medições são realizadas em modo de fluxo (50 ul / min) a 5 MHz. </li><li> Estabelecer uma freqüência de ressonância linha de base do sensor QCM em água (~ 30 min). </li><li> Desenhar uma suspensão das células vivas de estafilococos sensíveis à meticilina bacterianas em água (10 9 CFU / ml) através da célula de teste. </li><li> Monitorar continuamente as mudanças na freqüência de ressonância sensores e dissipação de energia para o primeiro harmônico, using o software Q-Soft. </li><li> Quando as mudanças na freqüência de ressonância sensores e dissipação atingiu níveis de saturação, adicionar a suspensão de esferas de látex PBP anticorpos conjugados (6,77 x10 10 contas / ml) para o fluxo durante o monitoramento contínuo da freqüência e dissipação. </li><li> Repita os passos de 9,2-9,5 para células de bactérias estafilococos resistentes à meticilina (MRSA). </li><li> Definir uma mudança de frequência através da variação da massa, devido à ligação de pelo Sauerbrey 24,25 equação Af =-Dm xn / C, onde C é a sensibilidade de uma massa constante (C = 17,7 ng x cm x Hz -2 -1 de 5 MHz, bactérias ), m é a massa e o símbolo n representa o número harmónico (n = 1). </li><li> Definir uma mudança de dissipação de energia (Δ D) a partir da gravação do decaimento exponencial de oscilação (frequência e amplitude de amortecimento, que permitiu a quantificação da energia dissipada e armazenadas durante um período de oscilação,E e E dissipada armazenados, respectivamente: D = E Δ dissipada / 2 πE armazenado. Δ D é medido em unidades de dissipação (DU), um DU = 10 -6 unidades relativas). </li></ol>

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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aseptic+Laboratory+Techniques:+Plating+Methods.">Aseptic Laboratory Techniques: Plating Methods.</a> J. Vis. Exp. (63), e3064 (2012).</li></ol>

Os autores declaram que não têm interesses financeiros concorrentes.

É bem sabido que os fagos podem ser usados ​​como sondas de biossensor para 28 agentes patogénicos bacterianos. Foi demonstrado neste trabalho que, juntamente com os anticorpos de fago PBP 2a podem ser utilizadas para resolver o problema antigo: discriminação estirpes resistentes e sensíveis a antibióticos rápidos. Verificou-se no entanto os fagos não modificados estafilocócicas normais não são adequados para a detecção de bactérias com dispositivos QCM, embora e...

Cepas resistentes de Staphylococcus aureus meticilina têm sido apontados como um fator essencial nas infecções e surtos nosocomiais 4-8. Formas comuns de reconhecimento de resistência à meticilina, tais como o ensaio de difusão em disco de agar oxacilina tela ou de microdiluição em caldo, dependem das condições de cultivo adaptadas para aumentar a expressão da resistência. As alterações incluem a utilização de oxacilina, incubação a 30 ou 35 ° C em vez de 37 ° C, e a inclusão de NaCl ao meio de crescimento. Além disso, para a detecção correcta por estes tipos de técnicas, um longo período de incubação de 24 horas em vez de 16 a 18 horas é necessário. Técnicas rápidos com o nível adequado (&gt; 96%) de sensibilidade para a identificação da resistência à meticilina incluem técnicas de microdiluição automatizados tais como o GPS Vitek-SA cartão, o sistema rápido de ATB estafilococo, e o sistema de painel Microscan rápida que produzem resultados após 3-11 hr 9-11. The Crystal MA RSA é um sistema de identificação de método rápido baseado no reconhecimento de crescimento de S. aureus na presença de 2% de NaCl e 4 mg de oxacilina por litro, com um sensor de fluorescência sensíveis ao oxigénio. Sensibilidades reivindicados variam entre 91 a 100% após 4 horas de incubação 12-14. Estes métodos fenotípicos estão limitados nas suas precisões pelo impacto de estirpes prevalentes que expressam resistência heterogénea. Portanto, os métodos mais amplamente aceito para o reconhecimento da resistência à meticilina é PCR ou hibridização DNA do gene mecA 15. No entanto, esta técnica requer que o ADN purificado e é extremamente sensível a vários aditivos (impurezas), que incluem fragmentos de células 16. Além disso, estas técnicas de precisar de um tempo para executar. Estratégias para o reconhecimento do produto do gene mecA, a proteína PBP 2a, pode ser utilizado para determinar a resistência e podem ser mais fiáveis ​​em comparação com as técnicas de ensaio padrão 17. de Staphylococcus aureus, incluindo aqueles que têm resistência à meticilina 1,2,18. Neste trabalho, proposta uma nova técnica para o reconhecimento específico e detecção de MRSA, tais como o reconhecimento de bactéria juntamente com a conformação de MRSA em tempo real. Para este fim específico a S. bacteriófago aureus com um amplo espectro de hospedeiros (incluindo MRSA), combinada com o anticorpo monoclonal contra a proteína (PBP 2as) têm sido utilizados. PBP 2a é uma proteína de parede celular, e é a causa de resistividade antibiótico de MRSA. No entanto anticorpo PBP 2a não é específico para S. aureus, uma vez que algumas bactérias possuem outras proteínas de ligação aos antibióticos com similaridade de sequência com o PBP 2a 19,20. Por conseguinte, neste trabalho, S. bacteriófago aureus e anticorpos contra a proteína PBP 2a têm sido utilizados. Para ser capaz de desenvolver um biossensor para especificamente detectar e identificar SARM um dispositivo com uma acção em dois passos foi utilizado. O passo inicial usou um S. aureus bacteriófago monocamada como uma sonda de sensor, enquanto que o segundo passo de PBP 2a empregues anticorpos específicos. Portanto, o primeiro passo será reconhecer S. bactéria Staphylococcus, como o outro irá ser sensível à proteína de ligação ao antibiótico. Quando os sinais recebidos a partir de dois passos são positivas, isso indica a detecção específica de MRSA.

<table border="1">
		<tbody>
		 <tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Reagents</td>
		 </tr>
		 <tr>
			<td>Phosphate buffered saline (PBS) </td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>P4417 </td>
			<td></td>
		 </tr>
		 <tr>
			<td>spectrophotometric-grade chloroform </td>
			<td>Sigma-Aldrich, 
				St. Louis, MO </td>
			<td>154733 </td>
			<td>(99.8% A.C.S.) </td>
		 </tr>
		 <tr>
			<td>Hexane-Anhydrous </td>
			<td>Sigma-Aldrich, 
				St. Louis, MO</td>
			<td>29609-0</td>
			<td>(95%)</td>
		 </tr>
		 <tr>
			<td>Ethyl Alcohol </td>
			<td>Pharmco products Inc. Brookfield, CT </td>
			<td>64-17-5</td>
			<td>190 Proof</td>
		 </tr>	
		 <tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		 </tr>
		 <tr>
			<td>PBP 2a antibody conjugated latex beads</td>
			<td>Denka Seiken Co., Ltd, Tokyo, Japan</td>
			<td>The MRSA-Screen test</td>
			<td></td>
		 </tr>
		 <tr>
			<td>S. aureus ATCC 12600, S. aureus ATCC 27690 and Bacillus subtilis ATCC 6051 from </td>
			<td>American Type Culture Collection (Manassas, VA);</td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>MRSA1, MRSA 2, MRSA 5, MRSA 13, MRSA 26, MRSA 34, MRSA 45, B. anthracis Sterne, Salmonella typhimurium LT2, Shigella flexneri, Yersinia enterocolotica, Proteus mirabilis, Klebsiella pneumoniae 13882; The lytic phage 12600 </td>
			<td>The culture collection of Auburn University, Auburn, AL</td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>Centrifuge </td>
			<td>Beckman Coulter</td>
			<td>Optima L-90K
				Ultra Centrifuge</td>
			<td></td>
		 </tr>
		 <tr>
			<td>KSV 2200 LB film balance</td>
			<td>KSV Chemicals, Finland</td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>Light microscope optical system </td>
			<td>CitoViva Technology Inc., Auburn, AL </td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>QCM-D</td>
			<td>Q-Sense AB, V&auml;stra Fr&ouml;lunda, Sweden </td>
			<td>E4</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Scanning electron microscope (SEM)</td>
			<td>JEOL USA Inc., Peabody, MA</td>
			<td>JEOL-7000F SEM </td>
			<td></td>
		 </tr>
		 <tr>
			<td>Transmitting electron microscopy (TEM)</td>
			<td>JEOL USA Inc., Peabody, MA</td>
			<td>JEOL, JEM 2010 </td>
			<td></td>
		 </tr>
		 <tr>
			<td>Stericup, Presterilized</td>
			<td>Millipore Corporation, Billerica, MA</td>
			<td>SCGPU05RE</td>
			<td>0.22 &mu;m, GP Express PLUS membrane</td>
		 </tr>
		 <tr>
			<td>Bio-Assay dish</td>
			<td>NUNC A/S, Denmark</td>
			<td>240835</td>
			<td>Dimensions(mm), 245 x 245 x 25</td>
		 </tr>
		 <tr>
			<td>Pipettes</td>
			<td>Gilson, Pipetman, France</td>
			<td>P100, P200, P1000</td>
			<td></td>
		 </tr>
		 <tr>
			<td>C24 Incubator Shaker</td>
			<td>New Brunswick Scientific, CT</td>
			<td>Classic C24</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Gold-coated quartz pieces</td>
			<td>Auburn University, AL</td>
			<td></td>
			<td>Homemade</td>
		 </tr>
		 <tr>
			<td>Petri dishes</td>
			<td>Fisher Brand, USA</td>
			<td>0875713</td>
			<td>100 mmX15 mm </td>
		 </tr>
		 <tr>
			<td>SterilGard III Advance</td>
			<td>The Baker Company, ME</td>
			<td>SG403</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Culture Growing Flasks</td>
			<td>Corning Incorporated, NY</td>
			<td>4995</td>
			<td>PYREX 250 ml Erlenmeyer flasks </td>
		 </tr>
		 <tr>
			<td>Optical Spectrometer</td>
			<td>Genesys 20. Thermo Spectronic, USA.</td>
			<td>4001</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Plasma Cleaner</td>
			<td>Harrick Plasma, USA</td>
			<td>PDC-32G</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Millipore water purification system</td>
			<td>Millipore</td>
			<td>Direct-Q</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Imaging Ellipsometer</td>
			<td>Accurion, USA</td>
			<td>nanofilm_ep3se
			</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Software </td>
			<td>Q-Sense AB, Sweden</td>
			<td>QSoft, QTools</td>
			<td></td>
		 </tr>
		</tbody>
 </table>

biosensor for detection of antibiotic resistant staphylococcus bacteria

Um bacteriófago lítico estruturalmente transformadas tendo uma ampla gama de hospedeiros de estirpes de Staphylococcus aureus e uma proteína de ligação à penicilina (PBP 2A) contas de látex de anticorpos conjugados têm sido utilizados para criar um biossensor para a discriminação concebido resistente à meticilina (MRSA) e sensível (MSSA) S . espécies aureus 1,2. Os fagos foram convertidos em esferóides fago pelo contato com a interface água-clorofórmio. Fago monocamadas esferóides foram movidos para uma superfície de biosensor por Langmuir-Blodgett (LB) técnica 3. Os biossensores criados foram examinados por uma microbalança de cristal de quartzo com dissipação de rastreamento (QCM-D) para avaliar as interações bactéria-fago. Interações bactéria-esferóides levou a freqüência de ressonância reduzida e um aumento na dissipação de energia, tanto para MRSA e MSSA isolados. Após a ligação de bactérias, esses sensores têm sido ainda mais exposto ao anticorpo a proteína de ligação à penicilina esférula de látexs. Sensores analisados ​​com MRSA respondeu a PBP 2a contas de anticorpos, embora sensores inspecionados com MSSA não deu nenhuma resposta. Esta distinção experimental determina uma discriminação clara entre resistente à meticilina e S. sensível aureus. Igualmente vinculados e bacteriófagos não ligados suprimir o crescimento de bactérias nas superfícies e em suspensões de água. Uma vez fagos são transformados em esferóides, eles mantêm a sua atividade lítica forte e mostram alta capacidade de captação bacteriana. O fago e o fago esferóides pode ser utilizado para teste e de esterilização de microorganismos resistentes aos antibióticos. Outras aplicações podem incluir a utilização em terapia de bacteriófago e superfícies antimicrobianas.

O fago demonstrou atividade lítica contra todas as cepas testadas de S. aureus, incluindo as estirpes MRSA, como indicado pelo teste de mancha de fago. Tamanhos de placas geralmente variou de 5 a 15 mm. Sem atividade foi encontrada contra outras culturas-teste (Tabela 1). Um crescimento normal de S. aureus ATCC 12600 em meio NZY em agitador-incubadora a 37 ° C é mostrada na Figura 1A (uma curva marcados por círculos vazios). O número d...

Watch this Scientific Journal Video about Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria at JoVE.com

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Biossensores fagos líticos e contas de anticorpos são capazes de discriminar entre resistente à meticilina (MRSA) e bactérias estafilococos sensíveis. Os fagos foram imobilizadas por um método de Langmuir-Blodgett sobre uma superfície de um sensor de microbalança de cristal de quartzo e trabalhado como de largo espectro de estafilococos sondas. Contas de anticorpos reconhecer MRSA.

Biossensor para detecção de bactérias Staphylococcus resistente a antibióticos

A structurally transformed lytic bacteriophage having a broad host range of Staphylococcus aureus strains and a penicillin-binding protein (PBP 2a) ...

biosensor-for-detection-antibiotic-resistant-staphylococcus

Research

JoVE Journal

Bioengineering

23.9K visualizações.  Auburn University. Biossensores fagos líticos e contas de anticorpos são capazes de discriminar entre resistente à meticilina (MRSA) e bactérias estafilococos sensíveis. Os fagos foram imobilizadas por um método de Langmuir-Blodgett sobre uma superfície de um sensor de microbalança de cristal de quartzo e trabalhado como de largo espectro de estafilococos sondas. Contas de anticorpos reconhecer MRSA.

Vídeo: Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Fabrication of Carbon Nanotube High-Frequency Nanoelectronic Biosensor for Sensing in High Ionic Strength Solutions

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density5 in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded6-8.
We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers9-11. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies11-12. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier.
Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube13, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber14 onto the device, and (d) carry out high frequency sensing in different ionic strength solutions11.

We describe the device fabrication and measurement protocol for carbon nanotube based high frequency biosensors. The high frequency sensing technique mitigates the fundamental ionic (Debye) screening effect and allows nanotube biosensor to be operated in high ionic strength solutions where conventional electronic biosensors fail. Our technology provides a unique platform for point-of-care (POC) electronic biosensors operating in physiologically relevant conditions.

Fabricação de Nanotubos de Carbono de Alta Frequência Nanoelectronic Biosensor de Sensoriamento em High Solutions força iônica

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them ...

Bioengenharia

Optical Detection of E. coli Bacteria by Mesoporous Silicon Biosensors

A label-free optical biosensor based on a nanostructured porous Si is designed for rapid capture and detection of Escherichia coli K12 bacteria, as a model microorganism. The biosensor relies on direct binding of the target bacteria cells onto its surface, while no pretreatment (e.g.&#160;by cell lysis) of the studied sample is required. A mesoporous Si thin film is used as the optical transducer element of the biosensor. Under white light illumination, the porous layer displays well-resolved Fabry-P&#233;rot fringe patterns in its reflectivity spectrum. Applying a fast Fourier transform (FFT) to reflectivity data results in a single peak. Changes in the intensity of the FFT peak are monitored. Thus, target bacteria capture onto the biosensor surface, through antibody-antigen interactions, induces measurable changes in the intensity of the FFT peaks, allowing for a &#39;real time&#39; observation of bacteria attachment.
The mesoporous Si film, fabricated by an electrochemical anodization process, is conjugated with monoclonal antibodies, specific to the target bacteria. The immobilization, immunoactivity and specificity of the antibodies are confirmed by fluorescent labeling experiments. Once the biosensor is exposed to the target bacteria, the cells are directly captured onto the antibody-modified porous Si surface. These specific capturing events result in intensity changes in the thin-film optical interference spectrum of the biosensor. We demonstrate that these biosensors can detect relatively low bacteria concentrations (detection limit of 104 cells/ml) in less than an hour.

Optical Detection of E. coli Bacteria by Mesoporous Silicon Biosensors

A label-free optical biosensor for rapid bacteria detection is introduced. The biosensor is based on a nanostructured porous Si, which is designed to directly capture the target bacteria cells onto its surface. We use monoclonal antibodies, immobilized onto the porous transducer, as the capture probes. Our studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations within minutes with no prior sample processing (such as cell lysis).

A detecção óptica de<em&gt; E. coli</em&gt; Bactérias por mesoporosos Silicon Biossensores

A label-free optical biosensor based on a nanostructured porous Si is designed for rapid capture and detection of Escherichia coli K12 bacteria, as a ...

Stress-induced Antibiotic Susceptibility Testing on a Chip

We have developed a rapid microfluidic method for antibiotic susceptibility testing in a stress-based environment. Fluid is passed at high speeds over bacteria immobilized on the bottom of a microfluidic channel. In the presence of stress and antibiotic, susceptible strains of bacteria die rapidly. However, resistant bacteria survive these stressful conditions. The hypothesis behind this method is new: stress activation of biochemical pathways, which are targets of antibiotics, can accelerate antibiotic susceptibility testing. As compared to standard antibiotic susceptibility testing methods, the rate-limiting step -&#160;bacterial growth -&#160;is omitted during antibiotic application. The technical implementation of the method is in a combination of standard techniques and innovative approaches. The standard parts of the method include bacterial culture protocols, defining microfluidic channels in polydimethylsiloxane&#160;(PDMS), cell viability monitoring with fluorescence, and batch image processing for bacteria counting. Innovative parts of the method are in the use of culture media flow for mechanical stress application, use of enzymes to damage but not kill the bacteria, and use of microarray substrates for bacterial attachment. The developed platform can be used in antibiotic and nonantibiotic related drug development and testing. As compared to the standard bacterial suspension experiments, the effect of the drug can be turned on and off repeatedly over controlled time periods. Repetitive observation of the same bacterial population is possible over the course of the same experiment.

We have developed a microfluidic platform for rapid antibiotic susceptibility testing. Fluid is passed at high speeds over bacteria immobilized on the bottom of a microfluidic channel. In the presence of stress and antibiotic, susceptible strains of bacteria die rapidly. However, resistant bacteria can survive these stressful conditions.

Teste de suscetibilidade de antibiótico induzido por estresse em um chip

We have developed a rapid microfluidic method for antibiotic susceptibility testing in a stress-based environment. Fluid is passed at high speeds over ...

High-throughput Identification of Bacteria Repellent Polymers for Medical Devices

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as contributing to antimicrobial resistance. One possible avenue for the reduction of device-associated infections is the identification of bacteria-repellent polymer coatings for these devices, which would prevent bacterial binding at the initial attachment step. A method for the identification of such repellent polymers, based on the parallel screening of hundreds of polymers using a microarray, is described here. This high-throughput method resulted in the identification of a range of promising polymers that resisted binding of various clinically relevant bacterial species individually and also as multi-species communities. One polymer, PA13 (poly(methylmethacrylate-co-dimethylacrylamide)), demonstrated significant reduction in attachment of a number of hospital isolates when coated onto two commercially available central venous catheters. The method described could be applied to identify polymers for a wide range of applications in which modification of bacterial attachment is important.

A high-throughput microarray method for the identification of polymers which reduce bacterial surface binding on medical devices is described.

High-throughput identificação de bactérias Polymers Repelente para dispositivos médicos

Medical devices are often associated with hospital-acquired infections, which place enormous strain on patients and the healthcare system as well as ...

The Use of a &#946;-lactamase-based Conductimetric Biosensor Assay to Detect Biomolecular Interactions

Biosensors are becoming increasingly important and implemented in various fields such as pathogen detection, molecular diagnosis, environmental monitoring, and food safety control. In this context, we used &#946;-lactamases as efficient reporter enzymes in several protein-protein interaction studies. Furthermore, their ability to accept insertions of peptides or structured proteins/domains strongly encourages the use of these enzymes to generate chimeric proteins. In a recent study, we inserted a single-domain antibody fragment into the Bacillus licheniformis BlaP &#946;-lactamase. These small domains, also called nanobodies, are defined as the antigen-binding domains of single chain antibodies from camelids. Like common double chain antibodies, they show high affinities and specificities for their targets. The resulting chimeric protein exhibited a high affinity against its target while retaining the &#946;-lactamase activity. This suggests that the nanobody and &#946;-lactamase moieties remain functional. In the present work, we report a detailed protocol that combines our hybrid &#946;-lactamase system to the biosensor technology. The specific binding of the nanobody to its target can be detected thanks to a conductimetric measurement of the protons released by the catalytic activity of the enzyme.

The Use of a &amp;#946;-lactamase-based Conductimetric Biosensor Assay to Detect Biomolecular Interactions

In this work, we report a new method to study protein-protein interactions using a conductimetric biosensor based on the hybrid &#946;-lactamase technology. This method relies on release of protons upon hydrolysis of &#946;-lactams.

O uso de um ensaio de β-lactamase-baseado titulometria Biosensor para detectar interações biomoleculares

Biosensors are becoming increasingly important and implemented in various fields such as pathogen detection, molecular diagnosis, environmental ...

Development of an Electrochemical DNA Biosensor to Detect a Foodborne Pathogen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, significantly affecting the rate of human mortality and morbidity. Conventional methods for the detection of V. parahaemolyticus such as culture-based methods, immunological assays, and molecular-based methods require complicated sample handling and are time-consuming, tedious, and costly. Recently, biosensors have proven to be a promising and comprehensive detection method with the advantages of fast detection, cost-effectiveness, and practicality. This research focuses on developing a rapid method of detecting V. parahaemolyticus with high selectivity and sensitivity using the principles of DNA hybridization. In the work, characterization of synthesized polylactic acid-stabilized gold nanoparticles (PLA-AuNPs) was achieved using X-ray Diffraction (XRD), Ultraviolet-visible Spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Field-emission Scanning Electron Microscopy (FESEM), and Cyclic Voltammetry (CV). We also carried out further testing of stability, sensitivity, and reproducibility of the PLA-AuNPs. We found that the PLA-AuNPs formed a sound structure of stabilized nanoparticles in aqueous solution. We also observed that the sensitivity improved as a result of the smaller charge transfer resistance (Rct) value and an increase of active surface area (0.41 cm2). The development of our DNA biosensor was based on modification of a screen-printed carbon electrode (SPCE) with PLA-AuNPs and using methylene blue (MB) as the redox indicator. We assessed the immobilization and hybridization events by differential pulse voltammetry (DPV). We found that complementary, non-complementary, and mismatched oligonucleotides were specifically distinguished by the fabricated biosensor. It also showed reliably sensitive detection in cross-reactivity studies against various food-borne pathogens and in the identification of V. parahaemolyticus in fresh cockles.

A protocol for the development of an electrochemical DNA biosensor comprising a polylactic acid-stabilized, gold nanoparticles-modified, screen-printed carbon electrode to detect Vibrio parahaemolyticus is presented.

Desenvolvimento de um Biosensor eletroquímico do DNA para detectar um patógeno de origem alimentar

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, ...

Biosensor-based High Throughput Biopanning and Bioinformatics Analysis Strategy for the Global Validation of Drug-protein Interactions

Receptors and enzyme proteins are important biomolecules that act as binding targets for bioactive small molecules. Thus, the rapid and global validation of the drug-protein interactions is highly desirable for not only understanding the molecular mechanisms underlying therapeutic efficacy but also for assessing drug characteristics, such as adsorption, distribution, metabolism, excretion, and toxicity (ADMET) for clinical use. Here, we present a biosensor-based high throughput strategy for the biopanning of T7 phage-displayed short peptides that can be easily displayed on the phage capsid. Subsequent analysis of the amino acid sequences of peptides containing short segments, as &#34;broken relics&#34;, of the drug-binding sites using bioinformatics programs in receptor ligand contact (RELIC) suite, is also shown. By applying this method to two clinically approved drugs, an anti-tumor irinotecan, and an anti-flu oseltamivir, the detailed process for collecting the drug-recognizing peptide sequences and highlighting the drug-binding sites of the target proteins are explained in this paper. The strategy described herein can be applied for any small molecules of interest.

This study aimed to present a strategy for identifying drug-peptide interactions. The strategy involves the biopanning of drug-recognizing short peptides based on a quartz-crystal microbalance (QCM) biosensor, followed by bioinformatics analysis for quantitatively assessing the information obtained for the drug recognition and annotation of the drug-binding sites on proteins.

Estratégia de análise de biopanning e bioinformática baseada em biosensor para a validação global de interações medicamentosas-proteínas

Receptors and enzyme proteins are important biomolecules that act as binding targets for bioactive small molecules. Thus, the rapid and global validation ...

Photodegradable Hydrogel Interfaces for Bacteria Screening, Selection, and Isolation

Biologists have long attempted to understand the relationship between phenotype and genotype. To better understand this connection, it is crucial to develop practical technologies that couple microscopic cell screening with cell isolation at high purity for downstream genetic analysis. Here, the use of photodegradable poly(ethylene glycol) hydrogels for screening and isolation of bacteria with unique growth phenotypes from heterogeneous cell populations is described. The method relies on encapsulating or entrapping cells with the hydrogel, followed by culture, microscopic screening, then use of a high-resolution light patterning tool for spatiotemporal control of hydrogel degradation and release of selected cells into a solution for retrieval. Applying different light patterns allows for control over the morphology of the extracted cell, and patterns such as rings or crosses can be used to retrieve cells with minimal direct UV light exposure to mitigate DNA damage to the isolates. Moreover, the light patterning tool delivers an adjustable light dose to achieve various degradation and cell release rates. It allows for degradation at high resolution, enabling cell retrieval with micron-scale spatial precision. Here, the use of this material to screen and retrieve bacteria from both bulk hydrogels and microfabricated lab-on-a-chip devices is demonstrated. The method is inexpensive, simple, and can be used for common and emerging applications in microbiology, including isolation of bacterial strains with rare growth profiles from mutant libraries and isolation of bacterial consortia with emergent phenotypes for genomic characterizations.

The use of photodegradable hydrogels to isolate bacterial cells by utilizing a high-resolution light pattering tool is reported. Essential experimental procedures, results, and advantages of the process are reviewed. The method enables rapid and inexpensive isolation of targeted bacteria showing rare or unique functions from heterogeneous communities or populations.

Interfaces de hidrogel fotodegradável para triagem, seleção e isolamento de bactérias

Biologists have long attempted to understand the relationship between phenotype and genotype. To better understand this connection, it is crucial to ...

Measurement of the Acid-Resistant Fluorescent Reporter Protein mCherry2

Pick any colony from the MRS agar plate containing electroporated L.reuteri cells and inoculate into a 96 well microplate containing filter sterilized MRS broth per well and an appropriate selection antibiotic. Incubate aerobically for 24 hours at 37 degrees Celsius without shaking. The next day, L.reuteri will precipitate out of the media in the stationary phase.Resuspend the culture by pipetting. Add 200 microliters of culture into a flat, clear, bottom 96 well plate. Transfer the plate to a plate reader and measure the optical density and fluorescence of M cherry two and other relevant reporters.Colony morphology noticeably changes in the presence of oxygen. Under low oxygen conditions colonies appear white, opaque, smooth and round. Under partial or leaky conditions, colonies appear undulate, and umbanet.Whereas under atmospheric oxygen levels colonies always appear low bait, round and dry. In wild Type L.rueteri, growth and reporter protein expression vary between colonies making accurate deductions difficult. Plasmid curing, and re-transformation can result in more stable expression but it is an uncommon and unique occurrence reliant on more stable mutant phenotypes spontaneously occurring.

Medição da proteína fluorescente reporter resistente a ácidos mCherry2

<meta charset="utf8"></head><body>Óxido de grafeno antibacteriano/nanocompósitos de cobre para bactérias resistentes

Fabrication of Antibacterial Graphene Oxide/Copper Nanocomposites

Antibiotics are currently the most used antibacterial treatment for killing bacteria. However, bacteria develop resistance when continually overexposed to antibiotics. Developing&#160;antimicrobial agents that can replace existing antibiotics is essential because antibiotic-resistant bacteria have resistance mechanisms for all current antibiotics and can promote nosocomial infections. To address this challenge, in this study, we propose graphene oxide/copper (GO/Cu) nanocomposites as antibacterial materials that can replace the existing antibiotics. GO/Cu nanocomposites are characterized by transmission electron microscopy and scanning electron microscopy. They show that copper (Cu) nanoparticles are well-grown on the graphene oxide sheets. Additionally, a microdilution broth method is used to confirm the efficacy of the antimicrobial substance against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (P. aeruginosa), which are frequently implicated in nosocomial infections. Specifically, 99.8% of MRSA and 84.7% of P. aeruginosa are eliminated by 500 &#181;g/mL of GO/Cu nanocomposites. Metal nanocomposites can eradicate antibiotic-resistant bacteria by releasing ions, forming reactive oxygen species, and physically damaging the bacteria. This study demonstrates the potential of antibacterial GO/Cu nanocomposites in eradicating antibiotic-resistant bacteria.

<meta charset="utf8"></head><body>Autor em destaque: Nanocompósitos metálicos para eliminar bactérias resistentes a antibióticos

Herein, we introduce graphene oxide/copper (GO/Cu) nanocomposites as an antibacterial nanomaterial. The antibacterial effectiveness of the GO/Cu nanocomposites was evaluated against both antibiotic-resistant gram-positive and gram-negative bacteria.

Fabricação de Nanocompósitos Antibacterianos de Óxido de Grafeno/Cobre

Antibiotics are currently the most used antibacterial treatment for killing bacteria. However, bacteria develop resistance when continually overexposed to ...