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- Gschneidtner, Tina, 1985, et al.
(författare)
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Toward Plasmonic Biosensors Functionalized by a Photoinduced Surface Reaction
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:28, s. 14751-14758
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for efficient coupling of amine nucleophilic molecules of choice to a nanostructured gold surface via photoinduced surface chemistry. The method is based on photoactive self-assembled monolayers and can be used to functionalize localized surface plasmon resonance (LSPR) based biosensors with biorecognition motifs while reducing nonspecific binding via introduction of hydrophilic units. The photoactive linker molecule, 5-bromo-7-nitroindoline, couples nucleophilic molecules such as biotin ethylenediamine to a surface when exposed to UV-light. The specific, noncovalent recognition between biotin and streptavidin is used for demonstration of a simple biorecognition assay based on the LSPR sensing principle. By doing so, one can envision that the binding of any streptavidin fusion protein, being attached to specific spots at the gold surface, is monitored by an LSPR peak shift. Since the surface functionalization is based on a photoinduced reaction, this method can be used to functionalize the surface in a local and site-specific way, and biomedical applications such as drug-screening platforms, microarrays, solid support protein synthesis, and even single molecule experiments can be envisioned.
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| 2. |
- Chen, Si, 1985
(författare)
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Miniaturized localized surface plasmon resonance biosensors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract Reliable and sensitive biosensors are required for fast and accurate diagnostics. Localized surface plasmon resonances (LSPRs) in noble-metal nanoparticles possess very high refractive index sensitivity close to the metal surface and therefore constitute an attractive biosensing platform. In this thesis, label-free biosensing with LSPR was investigated and demonstrated. The spatial sensing ranges of the particles were determined by thin layer deposition of dielectric materials. A comparison between the classical SPR and LSPR was performed using the same experimental setup. No obvious performance difference between the two sensing techniques was found. The versatility of the LSPR sensing technique was demonstrated by miniaturization of the sensor area, which could be reduced down to ~250 nanoparticles without compromising the short-term noise level. To further miniaturize the LSPR sensor, multiple single nanoparticles were measured using hyperspectral imaging. It was shown that by combining LSPR refractive index sensing and an enzyme linked immunoassay (ELISA), i.e. a horseradish peroxidase catalyzed precipitation, an extremely low surface coverage of enzyme molecules could be detected on single isolated nanoparticles. In a follow up investigation, electron beam lithography (EBL) and hyperspectral imaging were combined to enable simultaneous measurements of up to 700 individual particles. This made it possible to study statistical variations between the sensor particles. The observed variations in the responses from individual particles were interpreted as a result of large variations in sensitivity over the particle surface combined with the size distribution of the precipitate. In a separate study, a photo functionalization strategy compatible with LSPR biosensors was investigated. A biotin moiety was successfully functionalized with UV light on a self-assembled monolayer of photoactive nitroindoline on gold surfaces. Adsorption of streptavidin and streptavidin conjugated HRP to the surface-bound biotin could be monitored by the LSPR sensor. This strategy might be utilized for spatially localized surface functionalization for multiplexed miniaturized LSPR sensors. In summary, despite many experimental problems, the results discussed in this thesis point towards a number of important biosensing applications of plasmonic nanoparticles.
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| 3. |
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| 4. |
- Chen, Si, 1985, et al.
(författare)
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Plasmon-enhanced enzyme-linked immunosorbent assay on large arrays of individual particles made by electron beam lithography.
- 2013
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 7:10
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasensitive biosensing is one of the main driving forces behind the dynamic research field of plasmonics. We have previously demonstrated that the sensitivity of single nanoparticle plasmon spectroscopy can be greatly enhanced by enzymatic amplification of the refractive index footprint of individual protein molecules, so-called plasmon-enhanced enzyme-linked immunosorbent assay (ELISA). The technique, which is based on generation of an optically dense precipitate catalyzed by horseradish peroxidase at the metal surface, allowed for colorimetric analysis of ultralow molecular surface coverages with a limit of detection approaching the single molecule limit. However, the plasmonic response induced by a single enzyme can be expected to vary for a number of reasons, including inhomogeneous broadening of the sensing properties of individual particles, variation in electric field enhancement over the surface of a single particle and variation in size and morphology of the enzymatic precipitate. In this report, we discuss how such inhomogeneities affect the possibility to quantify the number of molecules bound to a single nanoparticle. The discussion is based on simulations and measurements of large arrays of well-separated gold nanoparticles fabricated by electron beam lithography (EBL). The new data confirms the intrinsic single-molecule sensitivity of the technique but we were not able to clearly resolve the exact number of adsorbed molecules per single particle. The results indicate that the main sources of uncertainty come from variations in sensitivity across the surface of individual particles and between different particles. There is also a considerable uncertainty in the actual precipitate morphology produced by individual enzyme molecules. Possible routes toward further improvements of the methodology are discussed.
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