Nanoplasmonics in Paper-Based Analytical Devices

Chemical and biological sensing are crucial tools in science and technology. Plasmonic nanoparticles offer a virtually limitless number of photons for sensing applications, which can be available for visual detection over long periods. Moreover, cellulosic materials, such as paper, represent a versatile building block for implementation of simple, yet valuable, microfluidic analytical devices. This mini review outlines the basic theory of nanoplasmonics and the usability of paper as a nanoplasmonic substrate exploiting its features as a (bio)sensing platform based on different mechanisms depending on localized surface plasmon resonance response. Progress, current trends, challenges and opportunities are also underscored. It is intended for general researchers and technologists who are new to the topic as well as specialist/experts in the field

Photoluminescent lateral flow based on non-radiative energy transfer for protein detection in human serum

A new paper-based lateral flow immunoassay configuration was engineered and investigated. The assay is intended for the detection of a model protein in human serum, that is, human immunoglobulin G, with the aim to demonstrate a virtually universal protein detection platform. Once the sample is added in the strip, the analyte is selectively captured by antibody-decorated silica beads (Ab-SiO) onto the conjugate pad and the sample flows by capillarity throughout the strip until reaching the test line, where a sandwich-like immunocomplex takes place due to the presence of antibody-functionalized QDs (Ab-QDs) onto the test line. Eventually, GO is added as a revealing agent and the photoluminescence of those sites protected by the complex Ab-SiO/Antigen/Ab-QDs will not be quenched, whereas those photoluminescent sites directly exposed are expected to be quenched by GO, including the control line, made of bare QDs, reporting that the assay occurred successfully. Hence, the photoluminescence of the test line is modulated by the formation of sandwich-like immunocomplexes. The proposed device achieves a limit of detection (LOD) of 1.35 ng mL in standard buffer, which is lower when compared with conventional lateral flow technology reported by gold nanoparticles, including other amplification strategies. Moreover, the resulting device was proven useful in human serum analysis, achieving a LOD of 6.30 ng mL in this complex matrix. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications, and can be easily transferred to other analytes such as clinically relevant protein biomarkers

Validity of a single antibody-based lateral flow immunoassay depending on graphene oxide for highly sensitive determination of E. coli O157:H7 in minced beef and river water

Considering the health risks of E. coli O157:H7 presence in food and water, an affordable and highly sensitive detection method is crucial. Herein, we report the first use of a single antibody-based fluorescent lateral flow immunoassay (FLFIA) depending on non-radiative energy transfer between graphene oxide and quantum dots for determination of E. coli O157:H7 in beef and river water. FLFIA showed a high sensitivity rate thousand-fold better than the conventional lateral flow (LF). In inoculated minced beef and river water samples, the limits of detection were 178 and 133 CFU g or mL, respectively. Besides, it presented a high selectivity in the presence of other possible interfering bacteria. The single antibody approach reduced the assay cost to 60% less than the conventional LF. Alongside, the results could be read by portable LF readers or smartphones. These advantages offer FLFIA as a promising technology for pathogen detection in food and water

Microorganism-decorated nanocellulose for efficient diuron removal

The environmental impacts of diuron have generated growing interest in remediation methods to prevent the potential threat of diuron to ecosystem integrity and human beings. Here, a simple and effective nanocellulose-based biocomposite coupled with Arthrobacter globiformis D47 as a herbicide degrader is presented for the rapid elimination of diuron. First, bacterium D47 was immobilized on the fiber networks of the nanocellulose, forming a bacteria-decorated nanocellulose (BDN) that outperformed direct utilization of bacterial suspensions for diuron decomposition. More importantly, the advantageous features of BDN could remarkably broaden its applicability since the bio-hybrid material rapidly degraded diuron and its major metabolite 3,4-dichloroaniline at low concentrations (1-10 mg ⁻¹). In addition, the morphology of BDN revealed the excellent biocompatibility of nanocellulose as cell scaffolding for bacterial proliferation. Then, the adsorption capacity of the nanocellulose and the enzymatic metabolism of the bacteria were validated as a joint mechanism of the BDN biocomposites in the removal of diuron. In addition, the wide applicability of BDN was further verified by the degradation of diuron in environmental matrices and other phenylurea herbicide targets. Therefore, the novel microorganism-immobilized nanocellulose composites provide a promising alternative material combining functional microorganisms with emerging nanomaterials, which may facilitate the bioremediation of organic xenobiotic pollution in complex environments

Graphene-based hybrid for enantioselective sensing applications

Chirality is a major field of research of chemical biology and is essential in pharmacology. Accordingly, approaches for distinguishing between different chiral forms of a compound are of great interest. We report on an efficient and generic enantioselective sensor that is achieved by coupling reduced graphene oxide with γ-cyclodextrin (rGO/γ-CD). The enantioselective sensing capability of the resulting structure was operated in both electrical and optical mode for of tryptophan enantiomers (D-/L-Trp). In this sense, voltammetric and photoluminescence measurements were conducted and the experimental results were compared to molecular docking method. We gain insight into the occurring recognition mechanism with selectivity toward D- and L-Trp as shown in voltammetric, photoluminescence and molecular docking responses. As an enantioselective solid phase on an electrochemical transducer, thanks to the different dimensional interaction of enantiomers with hybrid material, a discrepancy occurs in the Gibbs free energy leading to a difference in oxidation peak potential as observed in electrochemical measurements. The optical sensing principle is based on the energy transfer phenomenon that occurs between photoexcited D-/L-Trp enantiomers and rGO/γ-CD giving rise to an enantioselective photoluminescence quenching due to the tendency of chiral enantiomers to form complexes with γ-CD in different molecular orientations as demonstrated by molecular docking studies. The approach, which is the first demonstration of applicability of molecular docking to show both enantioselective electrochemical and photoluminescence quenching capabilities of a graphene-related hybrid material, is truly new and may have broad interest in combination of experimental and computational methods for enantiosensing of chiral molecules

Production of biofunctionalized MoS2 flakes with rationally modified lysozyme: a biocompatible 2D hybrid material

Bioapplications of 2D materials embrace demanding features in terms of environmental impact, toxicity and biocompatibility. Here we report on the use of a rationally modified lysozyme to assist the exfoliation of MoS2 bulk crystals suspended in water through ultrasonic exfoliation. The design of the proposed lysozyme derivative provides this exfoliated 2D-materail with both, hydrophobic groups that interact with the surface of MoS2 and hydrophilic groups exposed to the aqueous medium, which hinders its re-aggregation. This approach, clarified also by molecular docking studies, leads to a stable material (ζ-potential, 27 ± 1 mV) with a yield of up to 430 μg ml−1. The bio-hybrid material was characterized in terms of number of layers and optical properties according to different slots separated by diverse centrifugal forces. Furthermore the obtained material was proved to be biocompatible using human normal keratinocytes and human cancer epithelial cells, whereas the method was demonstrated to be applicable to produce other 2D materials such as graphene. This approach is appealing for the advantageous production of high quality MoS2 flakes and their application in biomedicine and biosensing. Moreover, this method can be applied to different starting materials, taking the denatured lysozyme a promising bio-tool for surface functionalization of 2D materials

Micromotor enhanced microarray technology for protein detection

Microengines meet microarray technology. The transport of a target molecule toward a sensing surface can play a critical role in biodetection performance. The mixing induced by the motion of self-propelled micromotors can assist such transport and consequently enhance the performance of surface–based biosensing systems, particularly in microarray–based immunosensing that can be extended to DNA and cell analysis.Peer ReviewedPostprint (published version

Nanomaterials based microarray platforms for biodetection

Tesi per compendi de publicacions. La consulta íntegra de la tesi, inclosos els articles no comunicats públicament per drets d'autor, es pot realitzar prèvia petició a l'Arxiu de la UPCAnalytical disciplines are an important field for the progress of healthcare and medicine. In fact the technologies related to analytical disciplines may reveal important information for early diagnosis, treatment of diseases, food safety and environmental monitoring. In this regard, novel advances in analytical disciplines are highly desired. As a promising tool, biosensors are useful systems that enable the detection of agents with diagnostic interest. Since nanotechnology enables the manipulation and control at the nanoscale, biosensors based on nanotechnology offer powerful capabilities to diagnostic technology. In this dissertation, the advantages of the integration of nanomaterials into microarray technology are widely studied, generally in terms of sensitivity. Particularly, the performance of cadmium-selenide/zinc-sulfide (CdSe@ZnS) quantum dots (QDs) and the fluorescent dye Alexa 647 as reporter in an assay designed to detect apolipoprotein E (ApoE) has been compared. The assay is a sandwich immunocomplex microarray that functions via excitation by visible light. ApoE was chosen for its potential as a biomarker for Alzheimer's disease. The two versions of the microarray (QD or Alexa 647) were assessed under the same experimental conditions. The QDs proved to be highly e¿ective reporters in the microarrays, although their performance strongly varied in function of the excitation wavelength. At 633 nm, the QD microarray, at an excitation wavelength of 532 nm, provided a limit of detection (LOD) of ~62 pg mL-1, ¿ve times more sensitive than that of the Alexa microarray (~307 pg mL-1). Finally, serial dilutions from a human serum sample were assayed with high sensitivity and acceptable precision and accuracy (Anal. Chem. 2012, 84:6821). Since graphene oxide (GO) is a recently discovered nanomaterial and microarray technology relies on optical signals, the photonic properties of GO are discussed and the state-of-the-art of GO in optical biosensing has been widely documented (Adv. Mater. 2012, 24:3298). Furthermore, GO has been studied as a highly efficient quencher of QDs, reporting a quenching efficiency of nearly 100%. Finally, such interaction between GO and QDs has been proposed as a highly sensitive transduction system for microarray-based biodetection (Carbon 2012, 50:2987). This research aims at demonstrating how the endeavour of the fusion between nanomaterials and microarray technology exhibits enormous possibilities towards biomarker screening, food safety and environmental monitoring.Las tecnologías relacionadas con el diagnóstico son un campo importante para el progreso de la medicina y el cuidado de las salud. Por ejemplo, estas tecnologías pueden aportar valiosa información para el tratamiento y diagnóstico temprano de enfermedades, seguridad en alimentos y monitoreo del medio ambiente. En este contexto, los sistemas de biosensado son una herramienta muy prometedora que permite la detección de agentes con interés diagnostico. Dado que la nanotecnología facilita la manipulación y control a la nanoescala, los sistemas de biodetección basados en nanotecnología poseen poderosas capacidades que pueden ser explotadas en las tecnologías relacionadas con el diagnóstico. En esta tesisis se han estudiado las ventajas que aporta la integración de nanomateriales a la tecnología de microarrays, generalmente en términos de sensibilidad. Particularmente, se ha estudiado el desempeño de la integración de nanocristales semiconductores (NS) para la detección de un biomarcador relacionado con Alzheimer en formato microarray. En dicho microarray se ha observado un importante rendimiento, mostrando un excelente limite de detección de 62 pg mL-1, el cual supera a otros metodos convencionales de detección como el ELISA (470 pg mL-1). También se ha analizado un banco de diluciones de una muestra de suero humano con precisión y exactitud aceptables (Anal. Chem. 2012, 84:6821). Por otra parte, ya que el óxido de grafeno (OG) es un material muy novedoso y la tecnología de microarrays depende de señales ópticas, se ha documentado ampliamente el estado del arte sobre el uso de (OG) en en el campo del biosensado óptico (Adv. Mater. 2012, 24:3298). Adicionalmente, se ha estudiado al OG como un desactivador de fluorescencia de NS altamente eficiente, presentando una eficiencia en la desactivación de NS de casi el 100%. Finalmente se ha aplicado dicha interacción entre NS y OG para diseñar un sistema de transducción altamente sensible (Carbon 2012, 50:2987 ). Esta investigación tiene por objetivo demostrar las ventajas y el potencial que posee la fusión entre los nanomateriales y la tecnología de microarrays como un sistema aplicado al campo del diagnósticoPostprint (published version

Nanopaper as an optical sensing platform

Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC. The platforms include a colorimetric-based sensor based on nanopaper containing embedded silver and gold nanoparticles; a photoluminescent-based sensor, comprising CdSe@ZnS quantum dots conjugated to nanopaper; and a potential up-conversion sensing platform constructed from nanopaper functionalized with NaYF4:Yb3+@Er3+&SiO2 nanoparticles. We have explored modulation of the plasmonic or photoluminescent properties of these platforms using various model biologically relevant analytes. Moreover, we prove that BC is and advantageous preconcentration platform that facilitates the analysis of small volumes of optically active materials (∼4 μL). We are confident that these platforms will pave the way to optical (bio)sensors or theranostic devices that are simple, transparent, flexible, disposable, lightweight, miniaturized and perhaps wearable.This work was supported by MINECO (Spain, MAT2014-52485-P, BIO2013-49464-EXP). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295).Peer Reviewe

Graphene oxide as an optical biosensing platform: A progress report

A few years ago, crucial graphene oxide (GO) features such as the carbon/oxygen ratio, number of layers, and lateral size were scarcely investigated and, thus, their impact on the overall optical biosensing performance was almost unknown. Nowadays valuable insights about these features are well documented in the literature, whereas others remain controversial. Moreover, most of the biosensing systems based on GO were amenable to operating as colloidal suspensions. Currently, the literature reports conceptually new approaches obviating the need of GO colloidal suspensions, enabling the integration of GO onto a solid phase and leading to their application in new biosensing devices. Furthermore, most GO‐based biosensing devices exploit photoluminescent signals. However, further progress is also achieved in powerful label‐free optical techniques exploiting GO in biosensing, particularly using optical fibers, surface plasmon resonance, and surface enhanced Raman scattering. Herein, a critical overview on these topics is offered, highlighting the key role of the physicochemical properties of GO. New challenges and opportunities in this exciting field are also highlighted.E.M.‐N. acknowledges the financial support from CONACYT (Mexico, Grant 293523) and National System of Researchers, CONACYT (Mexico, Grant 74314). A.M. thanks the support from European Commission through the Graphene Flagship Core 2 project. ICN2 acknowledges the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV2201320295. ICN2 is also funded by the CERCA Program/Generalitat de Catalunya.Peer reviewe