Optical detection enhancement in porous volumetric microfluidic capture elements using refractive index matching fluids

Wiederoder, Michael S.; Peterken, L.; Lu, Anxian; Rahmanian, Omid; Raghavan, Srinivasa R.; DeVoe, Don L.

doi:10.1039/c5an00988j

Cited by 13 publications

(12 citation statements)

References 31 publications

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“…The trivial fact, shown here, is that a very small mismatch of refractive indexes between the pores and the outside medium decreases the scattering. This idea is used in a recent study [31], where optical detection through a porous matrix is enhanced thanks to an addition of fluid having a good matching refractive index.…”

Section: Simulation Results On Mlmc-mcrtmentioning

confidence: 99%

Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

Vaudelle

2018

Optics Communications

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle ID: .http://hdl.handle.net/10985/17263 To cite this version :Fabrice VAUDELLE -Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model A Monte Carlo code is built taking into account macroscopic spheroid cavities inside a turbid medium, i.e. in mixing Multi-Layer Monte Carlo (MLMC) and Monte Carlo Ray Tracing (MCRT). That simulates a tissue with a strong and heterogeneous porosity, such as flesh tissues of fruit or bone tissues. This kind of tissue, which has two scales of porosity (microscopic and macroscopic), differs notably of the homogeneous and continuous model used in the usual radiative transfer equation. The influence of the presence of spheroids can be observed on the shape of the effective phase function, on the effect related to the time-resolved diffusion solution or also on the scattering coefficient retrieved by means of the Beer-Lambert relationship. For instance, the reduced scattering coefficients retrieved thanks to time-resolved transmittance from MLMC-MCRT models having a lot of intertwined large cavities show variations coherent with those retrieved from bone tissue. Furthermore, the effect of porosity on optical transmission seems to have a real impact when relative refractive index is close to 1.In this case, the equivalence problem between such porous MLMC-MCRT model and a homogeneous turbid medium, can be discussed at the level of the angular intensity distribution over the plane boundaries. This requires to fit this angular distribution by an Adding-Doubling model using optimized optical depth and scattering phase function. Experimental scattering phase functions obtained from apple tissues are considered in order to test this idea, and then compared with those computed with a MLMC-MCRT model.

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Section: Simulation Results On Mlmc-mcrtmentioning

confidence: 99%

Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

Vaudelle

2018

Optics Communications

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“…15 Refractive index matching has recently been shown to enhance the optical detection sensitivity for more conventional microsystems made from silica capillaries or packed glass beads in plastic channels. 16 However, unless the unusually low refractive index of fluoropolymers is exploited in device fabrication, the refractive index of the substrate solution must be significantly increased to match that of the device for example by addition of glycerol or sugars.…”

Section: Introductionmentioning

confidence: 99%

Covalent immobilisation of antibodies in Teflon-FEP microfluidic devices for the sensitive quantification of clinically relevant protein biomarkers

Pivetal

Pereira²,

Barbosa

et al. 2017

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This study reports for the first time the sensitive colorimetric and fluorescence detection of clinically relevant protein biomarkers by sandwich immunoassays using the covalent immobilisation of antibodies onto the fluoropolymer surface inside Teflon®-FEP microfluidic devices. Teflon®-FEP has outstanding optical transparency ideal for high-sensitivity colorimetric and fluorescence bioassays, however this thermoplastic is regarded as chemically inert and very hydrophobic. Covalent immobilisation can offer benefits over passive adsorption to plastic surfaces by allowing better control over antibody density, orientation and analyte binding capacity, and so we tested a range of different and novel covalent immobilisation strategies. We first functionalised the inner surface of a 10-bore, 200 μm internal diameter FEP microcapillary film with high-molecular weight polyvinyl alcohol (PVOH) without changing the outstanding optical transparency of the device delivered by the matched refractive index of FEP and water. Glutaraldehyde immobilisation was compared with the use of photoactivated linkers and NHS-ester crosslinkers for covalently immobilising capture antibodies onto PVOH. Three clinically relevant sandwich ELISAs were tested against the cytokine IL-1β, the myocardial infarct marker cardiac troponin I (cTnI), and the chronic heart failure marker brain natriuretic peptide (BNP). Overall, glutaraldehyde immobilisation was effective for BNP assays, but yielded unacceptable background for IL-1β and cTnI assays caused by direct binding of the biotinylated detection antibody to the modified PVOH surface. We found NHS-ester groups reacted with APTES-treated PVOH coated fluoropolymers. This facilitated a novel method for capture antibody immobilisation onto fluoropolymer devices using a bifunctional NHS-maleimide crosslinker. The density of covalently immobilised capture antibodies achieved using PVOH/APTES/NHS/maleimide approached levels seen with passive adsorption, and sensitive and quantitative assay performance was achieved using this method. Overall, the PVOH coating provided an excellent surface for controlled covalent antibody immobilisation onto Teflon®-FEP for performing high-sensitivity immunoassays.

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“…23,24 By integrating paper elements, the total capture probe density increases due to more efficient surface chemistries and the inherent 3-D porous network of paper to enhance performance. 25,26 In addition, balancing the rotational centrifugal force with the capillary force of paper inserts facilitates manipulation of the flow rate and directionality not possible with paper alone. The deceleration and acceleration of the hybrid device also induce active mixing not feasible with paper alone that can enhance the assay performance.…”

Section: Introductionmentioning

confidence: 99%

Novel functionalities of hybrid paper-polymer centrifugal devices for assay performance enhancement

et al. 2017

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The presented work demonstrates novel functionalities of hybrid paper-polymer centrifugal devices for assay performance enhancement that leverage the advantages of both paper-based and centrifugal microfluidic platforms. The fluid flow is manipulated by balancing the capillary force of paper inserts with the centrifugal force generated by disc rotation to enhance the signal of a colorimetric lateral flow immunoassay for pathogenic . Low-cost centrifugation for pre-concentration of bacteria was demonstrated by sample sedimentation at high rotational speeds before supernatant removal by a paper insert via capillary force after deceleration. The live bacteria capture efficiency of the device was similar to a commercial centrifuge. This pre-concentrated sample when combined with gold nanoparticle immunoconjugate probes resulted in a detection limit that is 10× lower than a non-concentrated sample for a lateral flow immunoassay. Signal enhancement was also demonstrated through rotational speed variation to prevent the flow for on-device incubation and to reduce the flow rate, thus increasing the sample residence time for the improved capture of gold nanoparticle-bacteria complexes in an integrated paper microfluidic assay. Finally, multiple sequential steps including sample pre-concentration, filtration, incubation, target capture by an integrated paper microfluidic assay, silver enhancement and quenching, and index matching were completed within a single device. The detection limit was 10 colony forming units per ml, a 100× improvement over a similar paper-based lateral flow assay. The techniques utilize the advantages of paper-based microfluidic devices, while facilitating additional functionalities with a centrifugal microfluidic platform for detection performance enhancement in a low-cost, automated platform amenable to point-of-care environments.

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Optical detection enhancement in porous volumetric microfluidic capture elements using refractive index matching fluids

Cited by 13 publications

References 31 publications

Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

Light scattering in thin turbid tissue including macroscopic porosities: A study based on a Monte Carlo model

Covalent immobilisation of antibodies in Teflon-FEP microfluidic devices for the sensitive quantification of clinically relevant protein biomarkers

Novel functionalities of hybrid paper-polymer centrifugal devices for assay performance enhancement

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