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1.
Nat Commun ; 10(1): 2109, 2019 05 08.
Artigo em Inglês | MEDLINE | ID: mdl-31068594

RESUMO

Nanopore sensors detect individual species passing through a nanoscale pore. This experimental paradigm suffers from long analysis times at low analyte concentration and non-specific signals in complex media. These limit effectiveness of nanopore sensors for quantitative analysis. Here, we address these challenges using antibody-modified magnetic nanoparticles ((anti-PSA)-MNPs) that diffuse at zero magnetic field to capture the analyte, prostate-specific antigen (PSA). The (anti-PSA)-MNPs are magnetically driven to block an array of nanopores rather than translocate through the nanopore. Specificity is obtained by modifying nanopores with anti-PSA antibodies such that PSA molecules captured by (anti-PSA)-MNPs form an immunosandwich in the nanopore. Reversing the magnetic field removes (anti-PSA)-MNPs that have not captured PSA, limiting non-specific effects. The combined features allow detecting PSA in whole blood with a 0.8 fM detection limit. Our 'magnetic nanoparticle, nanopore blockade' concept points towards a strategy to improving nanopore biosensors for quantitative analysis of various protein and nucleic acid species.


Assuntos
Anticorpos/química , Técnicas Biossensoriais/instrumentação , Nanopartículas de Magnetita/química , Nanoporos , Anticorpos/imunologia , Técnicas Biossensoriais/métodos , Calicreínas/análise , Calicreínas/imunologia , Limite de Detecção , Membranas Artificiais , Antígeno Prostático Específico/análise , Antígeno Prostático Específico/imunologia , Compostos de Silício/química , Fatores de Tempo
2.
Biosens Bioelectron ; 127: 229-235, 2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30622037

RESUMO

The work presented here describes the development of an optical label-free biosensor based on a porous silicon (PSi) Bragg reflector to study heterogeneity in single cells. Photolithographic patterning of a poly(ethylene glycol) (PEG) hydrogel with a photoinitiator was employed on RGD peptide-modified PSi to create micropatterns with cell adhesive and cell repellent areas. Macrophage J774 cells were incubated to form cell microarrays and single cell arrays. Moreover, cells on the microarrays were lysed osmotically with Milli-Q™ water and the infiltration of cell lysate into the porous matrix was monitored by measuring the red shift in the reflectivity. On average, the magnitude of red shift increased with the increase in the number of cells on the micropatterns. The red shift from the spots with single cells varied from spot to spot emphasizing the heterogeneous nature of the individual cells.


Assuntos
Técnicas Biossensoriais/métodos , Análise de Célula Única/métodos , Análise Serial de Tecidos/métodos , Hidrogéis/química , Polietilenoglicóis/química , Porosidade , Silício/química , Propriedades de Superfície
3.
Biosens Bioelectron ; 117: 530-536, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-29982124

RESUMO

The integration of plasmonic nanoparticles into biosensors has the potential to increase the sensitivity and dynamic range of detection, through the use of single nanoparticle assays. The analysis of the localized surface plasmon resonance (LSPR) of plasmonic nanoparticles has allowed the limit of detection of biosensors to move towards single molecules. However, due to complex equipment or slow analysis times, these technologies have not been implemented for point-of-care detection. Herein, we demonstrate an advancement in LSPR analysis by presenting a technique, which utilizes an inexpensive CMOS-equipped digital camera and a dark-field microscope, that can analyse the λmax of over several thousand gold nanospheres in less than a second, without the use of a spectrometer. This improves the throughput of single particle spectral analysis by enabling more nanoparticles to be probed and in a much shorter time. This technique has been demonstrated through the detection of interleukin-6 through a core-satellite binding assay. We anticipate that this technique will aid in the development of high-throughput, multiplexed and point-of-care single nanoparticle biosensors.

4.
Opt Lett ; 42(15): 2968-2971, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28957221

RESUMO

We experimentally investigate the influence of geometric aberrations in optical tweezers using back focal plane interferometry. We found that the introduction of coma aberrations causes significant modification to the Brownian motion of the trapped particle, producing an apparent cross-coupling between the in-plane aberrated axis and the weaker propagation axis. This coupling is evidenced by the emergence of a second dominant low frequency Lorentzian feature in the position power spectral density. The effect on Brownian motion was confirmed using a secondary unaberrated probe beam, ruling out the possibility of systematic optical effects related to the detection system.

5.
Phys Chem Chem Phys ; 18(29): 19765-72, 2016 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-27385513

RESUMO

Semiconductor (SC) quantum dots (QDs) have recently been fabricated by both chemical and plasma techniques for specific absorption and emission of light. Their optical properties are governed by the size of the QD and the chemistry of any passivation at their surface. Here, we decouple the effects of confinement and passivation by utilising DC magnetron sputtering to fabricate SC QDs in a perfluorinated polyether oil. Very high band gaps are observed for fluorinated QDs with increasing levels of quantum confinement (from 4.2 to 4.6 eV for Si, and 2.5 to 3 eV for Ge), with a shift down to 3.4 eV for Si when oxygen is introduced to the passivation layer. In contrast, the fluorinated Si QDs display a constant UV photoluminescence (3.8 eV) irrespective of size. This ability to tune the size and passivation independently opens a new opportunity to extending the use of simple semiconductor QDs.

6.
Phys Rev E ; 93(2): 022137, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26986318

RESUMO

We investigate the dynamics of high-aspect-ratio nanowires trapped axially in a single gradient force optical tweezers. A power spectrum analysis of the dynamics reveals a broad spectral resonance of the order of kHz with peak properties that are strongly dependent on the input trapping power. A dynamical model incorporating linear restoring optical forces, a nonconservative asymmetric coupling between translational and rotational degrees of freedom, viscous drag, and white noise provides an excellent fit to experimental observations. A persistent low-frequency cyclical motion around the equilibrium trapping position, with a frequency distinct from the spectral resonance, is observed from the time series data.

7.
Nano Lett ; 16(3): 1903-10, 2016 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-26848883

RESUMO

We demonstrate that silicon (Si) nanoparticles with scattering properties exhibiting strong dielectric resonances can be successfully manipulated using optical tweezers. The large dielectric constant of Si has a distinct advantage over conventional colloidal nanoparticles in that it leads to enhanced trapping forces without the heating associated with metallic nanoparticles. Further, the spectral features of the trapped nanoparticles provide a unique marker for probing size, shape, orientation and local dielectric environment. We exploit these properties to investigate the trapping dynamics of Si nanoparticles with different dimensions ranging from 50 to 200 nm and aspect ratios between 0.4 and 2. The unique combination of spectral and trapping properties make Si nanoparticles an ideal system for delivering directed nanoscale sensing in a range of potential applications.

8.
Adv Mater ; 27(40): 6144-50, 2015 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-26331712

RESUMO

Fluorescence lifetime imaging microscopy is successfully demonstrated in both one- and two-photon cases with surface modified, nanocrystalline silicon quantum dots in the context of bioimaging. The technique is further demonstrated in combination with Förster resonance energy transfer studies where the color of the nanoparticles is tuned by using organic dye acceptors directly conjugated onto the nanoparticle surface.


Assuntos
Microscopia de Fluorescência , Pontos Quânticos/química , Silício/química , Transferência Ressonante de Energia de Fluorescência/métodos , Células HeLa , Humanos , Microscopia de Fluorescência/métodos , Propriedades de Superfície
9.
Anal Chem ; 87(19): 9946-53, 2015 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-26312479

RESUMO

Herein is presented a microsensor technology as a diagnostic tool for detecting specific matrix metalloproteinases (MMPs) at very low concentrations. MMP-2 and MMP-9 are detected using label free porous silicon (PSi) photonic crystals that have been made selective for a given MMP by filling the nanopores with synthetic polymeric substrates containing a peptide sequence for that MMP. Proteolytic cleavage of the peptide sequence results in a shift in wavelength of the main peak in the reflectivity spectrum of the PSi device, which is dependent on the amount of MMP present. The ability to detect picogram amounts of MMP-2 and MMP-9 released by primary retinal pigment epithelial (RPE) cells and iris pigment epithelial (IPE) cells stimulated with lipopolysaccharide (LPS) is demonstrated. It was found that both cell types secrete higher amounts of MMP-2 than MMP-9 in their stimulated state, with RPE cells producing higher amounts of MMPs than IPE cells. The microsensor performance was compared to conventional protease detection systems, including gelatin zymography and enzyme linked immunosorbent assay (ELISA). It was found that the PSi microsensors were more sensitive than gelatin zymography; PSi microsensors detected the presence of both MMP-2 and MMP-9 while zymography could only detect MMP-2. The MMP-2 and MMP-9 quantification correlated well with the ELISA. This new method of detecting protease activity shows superior performance to conventional protease assays and has the potential for translation to high-throughput multiplexed analysis.


Assuntos
Metaloproteinase 2 da Matriz/análise , Metaloproteinase 9 da Matriz/análise , Nanoporos , Óptica e Fotônica/métodos , Silício/química , Sequência de Aminoácidos , Células Cultivadas , Cristalização , Ensaios Enzimáticos , Humanos , Iris/citologia , Iris/enzimologia , Limite de Detecção , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Nanoporos/ultraestrutura , Peptídeos/química , Peptídeos/metabolismo , Porosidade , Epitélio Pigmentado da Retina/citologia , Epitélio Pigmentado da Retina/enzimologia
10.
J Mater Chem B ; 2(23): 3582-3588, 2014 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-24910774

RESUMO

Porous silicon (PSi) rugate filters modified with alkyne-terminated monolayers were chemically patterned using a combination of photolithography of photoresist and click chemistry. Two chemical functionalities were obtained by conjugating, via click reactions, ethylene glycol moieties containing two different terminal groups to discrete areas towards the exterior of a PSi rugate filter. The patterning of biological species to the functionalized surface was demonstrated through the conjugation of fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA). Fluorescence microscopy showed selective positioning of FITC-BSA at discretely functionalized areas. Meanwhile, the optical information from precisely defined positions on the patterned surface was monitored by optical reflectivity measurements. The optical measurements revealed successful step-wise chemical functionalization followed by immobilization of gelatin. Multiplex detection of protease activity from different array elements on the patterned surface was demonstrated by monitoring the blue shifts in the reflectivity spectra resulted from the digestion of gelatin by subtilisin. Precise information from both individual elements and average population was acquired. This technique is important for the development of PSi into a microarray platform for highly parallel biosensing applications, especially for cell-based assays.

11.
Bioconjug Chem ; 25(7): 1282-9, 2014 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-24892699

RESUMO

Herein, the ability of porous silicon (PSi) particles for selectively binding to specific cells is investigated. PSi microparticles with a high reflectance band in the reflectivity profile are fabricated, and subsequently passivated and modified with antibodies via the Cu(I)-catalyzed alkyne-azide cycloaddition reaction and succimidyl activation. To demonstrate the ability of the antibody-modified PSi particles to selectively bind to one cell type over others, HeLa cells were transfected with surface epitopes fused to fluorescent proteins. The antibody-functionalized PSi particles showed good selectivity for the corresponding surface protein on HeLa cells, with no significant cross-reactivity. The results are important for the application of PSi particles in cell sensing and drug delivery.


Assuntos
Anticorpos Monoclonais/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Receptores da Transferrina/metabolismo , Silício/química , Alquinos/química , Anticorpos Monoclonais/imunologia , Azidas/química , Reação de Cicloadição , Proteínas de Fluorescência Verde/imunologia , Células HeLa , Humanos , Microscopia Eletrônica de Varredura , Porosidade , Silício/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
12.
Langmuir ; 30(18): 5209-16, 2014 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-24716818

RESUMO

In this study, we describe a solution procedure for the preparation and surface modification of photostable colloidal silicon quantum dots (SiQDs) for imaging of cancer cells. Photoluminescent SiQDs were synthesized by reduction of halogenated silane precursors using a microemulsion process. It was shown that 1,8-nonadiyne molecules could be grafted onto the surface of hydrogen-terminated SiQDs via ultraviolet (UV)-promoted hydrosilylation, demonstrated by Fourier transform infrared spectroscopy (FTIR) measurements. In addition, various azide molecules were coupled onto nonadiyne-functionalized particles, rendering particles dispersible in selected polar and nonpolar solvents. The photoluminescence of functionalized SiQDs was stable against photobleaching and did not vary appreciably within biologically applicable pH and temperature ranges. To demonstrate compatibility with biological systems, water-soluble SiQDs were used for fluorescent imaging of HeLa cells. In addition, the SiQDs were shown to be non-cytotoxic at concentrations up to 240 µg/mL. The results presented herein provide good evidence for the versatility of functionalized SiQDs for fluorescent bioimaging application.


Assuntos
Química Click/métodos , Pontos Quânticos , Silício/química , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente
13.
Chem Soc Rev ; 43(8): 2680-700, 2014 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-24395024

RESUMO

Concerns over possible toxicities of conventional metal-containing quantum dots have inspired growing research interests in colloidal silicon nanocrystals (SiNCs), or silicon quantum dots (SiQDs). This is related to their potential applications in a number of fields such as solar cells, optoelectronic devices and fluorescent bio-labelling agents. The past decade has seen significant progress in the understanding of fundamental physics and surface properties of silicon nanocrystals. Such understanding is based on the advances in the preparation and characterization of surface passivated colloidal silicon nanocrystals. In this critical review, we summarize recent advances in the methods of preparing high quality silicon nanocrystals and strategies for forming self-assembled monolayers (SAMs), with a focus on their bio-applications. We highlight some of the major challenges that remain, as well as lessons learnt when working with silicon nanocrystals (239 references).


Assuntos
Corantes Fluorescentes/química , Nanopartículas/química , Pontos Quânticos/química , Silício/química , Imunofluorescência , Humanos , Imagem por Ressonância Magnética , Microscopia Confocal
14.
ACS Appl Mater Interfaces ; 5(14): 6514-21, 2013 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-23781770

RESUMO

Porous silicon (PSi) is an ideal platform for label-free biosensing, and the development of porous silicon patterning will open a pathway to the development of highly parallel PSi biochips for detecting multiple analytes. The optical response of PSi photonic crystal is determined by the changes in the effective bulk refractive index resulting from reactions/events occurring within the internal pore space. Therefore, introducing precise chemical functionalities in the pores of PSi is essential to ensure device selectivity. Here we describe the fabrication of PSi patterns that possess discrete chemical functionalities that are restricted to precise locations. The key difference to previous patterning protocols for PSi is that the entire porous material is first modified with a self-assembled monolayer of a α,ω-diyne adsorbate prior to patterning using a microfabricated titanium mask. The distal alkyne moieties in the monolayer are then amenable to further selective modification by the archetypal "click" reaction, the copper catalyzed alkyne-azide cycloaddition (CuAAC), using the titanium mask as a resist. This type of patterning is suitable for further immobilization of biological recognition elements, and presents a new platform for highly parallel PSi biosensor for multiple detections.


Assuntos
Silício/química , Química Click , Fótons , Porosidade , Espectrofotometria Infravermelho , Raios Ultravioleta
15.
Analyst ; 138(13): 3593-615, 2013 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-23702690

RESUMO

Porous silicon photonics is the ideal platform for high sensitivity, high selectivity monitoring of biological molecules in a complex fluidic environment. The potential of this technology was identified almost 15 years ago, however, it has taken considerable advances in porous silicon surface chemistry, photonics, and micro-fabrication to create truly effective devices that can provide new insights into the behaviour of biological systems. In this review we provide a critical assessment of the development of porous silicon optical biosensors from the early demonstrations of affinity based sensing to the current trends in monitoring single cell activity and perspectives in the use of photonic microparticles for biomedical applications.


Assuntos
Técnicas Biossensoriais/métodos , Dióxido de Silício/química , Análise de Célula Única/métodos , Animais , Humanos , Microtecnologia , Fenômenos Ópticos , Porosidade
16.
Nano Lett ; 13(3): 1185-91, 2013 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-23394286

RESUMO

Axially resolved microphotoluminescence mapping of semiconductor nanowires held in an optical tweezers reveals important new experimental information regarding equilibrium trapping points and trapping stability of high aspect ratio nanostructures. In this study, holographic optical tweezers are used to scan trapped InP nanowires along the beam direction with respect to a fixed excitation source and the luminescent properties are recorded. It is observed that nanowires with lengths on the range of 3-15 µm are stably trapped near the tip of the wire with the long segment positioned below the focus in an inverted trapping configuration. Through the use of trap multiplexing we investigate the possibility of improving the axial stability of the trapped nanowires. Our results have important implication for applications of optically assisted nanowire assembly and optical tweezers based scanning probes microscopy.

17.
Chem Commun (Camb) ; 48(97): 11874-6, 2012 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-23125971

RESUMO

A solution method for preparing surface functionalized colloidal silicon quantum dots (SiQDs) is presented. SiQDs prepared by this method are reasonably monodispersed and can be further functionalized via thiol-ene click reactions to introduce specific functionalities (i.e. -NH(2), -COOH, -SO(3)(-), alkane, alkene).


Assuntos
Química Click , Pontos Quânticos , Silício/química , Compostos de Sulfidrila/química , Coloides/síntese química , Coloides/química , Estrutura Molecular , Tamanho da Partícula , Propriedades de Superfície
18.
Phys Chem Chem Phys ; 14(47): 16433-9, 2012 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-23132209

RESUMO

Herein, mesoporous silicon (PSi) is configured as a single sensing device that has dual readouts; as a photonic crystal sensor in a Rugate filter configuration, and as a high surface area porous electrode. The as-prepared PSi is chemically modified to provide it with stability in aqueous media and to allow for the subsequent coupling of chemical species, such as via Cu(I)-catalyzed cycloaddition reactions between 1-alkynes and azides ("click" reactions). The utility of the bimodal capabilities of the PSi sensor for monitoring surface coupling procedures is demonstrated by the covalent coupling of a ferrocene derivative, as well as by demonstrating ligand-exchange reactions (LER) at the PSi surface. Both types of reactions were monitored through optical reflectivity measurements, as well as electrochemically via the oxidation/reduction of the surface tethered redox species.


Assuntos
Técnicas Eletroquímicas/instrumentação , Filtração/instrumentação , Silício/química , Alquinos/química , Azidas/química , Eletrodos , Desenho de Equipamento , Oxirredução , Espectroscopia Fotoeletrônica , Porosidade , Propriedades de Superfície
19.
Langmuir ; 28(44): 15444-9, 2012 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-23078244

RESUMO

The ability to impart discrete surface chemistry to the inside and outside of mesoporous silicon is of great importance for a range of biomedical applications, from selective (bio)sensing to tissue-specific drug delivery. Here we present a generic strategy toward achieving depth-resolved functionalization of the external and internal porous surfaces by a simple change in the wavelength of the light being used to promote surface chemical reactions. UV-assisted hydrosilylation, limited by the penetration depth of UV light, is used to decorate the outside of the mesoporous structure with carboxylic acid molecules, and white light illumination triggers the attachment of dialkyne molecules to the inner porous matrix.


Assuntos
Alcenos/química , Alquinos/química , Luz , Silício/química , Raios Ultravioleta , Estrutura Molecular , Porosidade , Propriedades de Superfície
20.
Opt Express ; 20(10): 11232-40, 2012 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-22565745

RESUMO

We report on the demonstration of three-dimensional optical trapping inside the core of a hollow-core microstructured optical fiber specifically designed and fabricated for this purpose. Optical trapping was achieved by means of an external tweezers beam incident transversely on the fiber and focused through the fiber cladding. Trapping was achieved for a range of particle sizes from 1 to 5 µm, and manipulation of the particles in three-dimensions through the entire cross-section of the fiber core was demonstrated. Spectroscopy was also performed on single fluorescent particles, with the fluorescence captured and guided in the fiber core. Video tracking methods allowed the optical traps to be characterized and photobleaching of single particles was also observed and characterized.


Assuntos
Fibras Ópticas , Óptica e Fotônica , Desenho de Equipamento , Tecnologia de Fibra Óptica , Imagem Tridimensional , Luz , Micromanipulação , Distribuição Normal , Pinças Ópticas , Tamanho da Partícula , Fotodegradação , Refratometria , Espectrometria de Fluorescência/métodos , Espectrofotometria/métodos , Análise Espectral/instrumentação
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