ABSTRACT Methods combining immunology and surface-enhanced Raman scattering (SERS) have been deve... more ABSTRACT Methods combining immunology and surface-enhanced Raman scattering (SERS) have been developed for the simultaneous detection, identification, and localization of proteinaceous binding media found in artworks. However, complex surface topographies and heterogeneous compositions of art samples represent significant challenges for the general optimization of this technique. In particular, aggregation of immuno-SERS nanoparticles can lead to non-specific SERS response across the sample surface, resulting in inaccurate identification of binding media or dubious localization maps. This aggregation also diminishes the sample area available for analysis, as excitation of visible nanoparticle aggregates by the Raman laser must be avoided during data collection. In the present work, we synthesize several types of immuno-SERS nanoparticles and investigate their applicability for the detection and localization of ovalbumin-rich (egg-based) binding media in art samples. Dimers of gold nanoparticles (Au NPs) connected by a Raman-active dithiolated linker are conjugated to secondary antibodies through either an amino or carboxyl functional group (SERS tags). The SERS tags display localized surface plasmon resonance (LSPR) at 532 nm. SERS spectra are acquired at 633 nm (SERS-633) in order to maximize tuning between laser excitation and LSPR, while avoiding sample burning. In an indirect immunoassay applied to replica art samples, carboxy-terminated SERS-633 tags show strong Raman reporter signal, specificity for the target protein, robust response in the presence of various inorganic pigments, and reduced aggregation on sample surfaces compared to amino-terminated or commercial SERS tags. Scanning electron microscopy (SEM) is used to visualize Au NPs bound to egg media in situ, demonstrating that carboxy-terminated SERS-633 tags remain as discrete dimer units throughout the assay.
Analytical and bioanalytical chemistry, Jan 15, 2015
A systematic study on the influence of pigments and sample aging on casein identification was per... more A systematic study on the influence of pigments and sample aging on casein identification was performed on 30 reconstructed paints. The protein in all the paints was extracted into solution for analysis. The amount of protein that can be retrieved for solution-based analysis in each of the reconstructed paints was studied with a well-developed NanoOrange method before and after artificial aging. The results showed that in the paints with calcium phosphate (in bone black) and copper carbonate, hydroxide, or acetate (in verdigris and azurite), the amount of protein that can be retrieved for liquid-phase analysis is much smaller than the other paints, indicating that the protein degradation was accelerated significantly in those paints. Carbon (in vine black), calcium carbonate (in natural chalk), and calcium sulfate (terra alba gypsum and ground alabaster) did not affect much the amount of protein that can be retrieved in the paints compared to non-pigmented binder, meaning that the p...
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
The search for stable varnishes which will saturate and provide a desired finish for a variety of... more The search for stable varnishes which will saturate and provide a desired finish for a variety of painted and decorative surfaces is ongoing. Varnish blends were investigated, composed of ratios from 2% to 98%, of Laropal A81 (a highly stable and commercially available low molecular weight urea‐aldehyde resin) in Paraloid B‐72, in order to capitalise on the positive properties of the individual resins and allow tailoring for specific surface problems in a single application. Aspects relevant to appearance and practice are reported in this paper. The structure of dried films was microscopically examined and their refractive index (RI) measured. Their effect on painted surfaces was evaluated through both instrumental measurement of specular gloss and saturation, and through subjective evaluation, which was influenced by diffuse as well as specular reflectance. Dried films of the entire range of blends were found to exhibit useful optical and aesthetic properties on a variety of paint surfaces, although it was felt that blends at either end of the range produced the most promising varnishes. Although the blends produced films that were phase separated, this did not cause any detrimental optical effects and may even contribute to the range of achievable surface effects. Subjective evaluation of appearance and working properties is shown to be important in any such investigation.
There are several analytical techniques currently in use in conservation science to identify prot... more There are several analytical techniques currently in use in conservation science to identify proteins in artworks. However, as is often the case, the determination of the exact location of a protein in a complex layer structure is challenging due to difficulty in separating layers. Localization of the protein in a cross-section has been demonstrated through attenuated total reflectance-Fourier transform infrared mapping and imaging as well as chemiluminescent and fluorescent-labeled antibodies; however, these techniques either require expensive instrumental setups or produce results that can be challenging to interpret. This paper will present research using surface-enhanced Raman scattering (SERS) nanotags complexed to secondary antibodies in conjunction with primary antibodies for the localization of ovalbumin, collagen, and casein in cross-sections from replicas and artworks containing avian egg, animal glue, or casein binders. The advantages of this technique over the others are (1) the detection method is a Raman microscope, equipment found in several museum laboratories; (2) the distinctive SERS signal from the nanotag increases the detection limit of the protein and decreases the interference from other colorants present in the cross-section layers; and finally, (3) the large (120 nm) SERS-labeled antibodies do not appear to penetrate into the cross-section, eliminating the risk of spurious signal and misidentification. Any agglomerations due to surface texture are clearly visible under normal illumination and can be avoided easily during analysis or removed with a light polish. This technique not only allows protein localization in multilayered samples while preserving the stratigraphic information but also retains the protein specificity of the antibody approach. Figure
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
ABSTRACT Methods combining immunology and surface-enhanced Raman scattering (SERS) have been deve... more ABSTRACT Methods combining immunology and surface-enhanced Raman scattering (SERS) have been developed for the simultaneous detection, identification, and localization of proteinaceous binding media found in artworks. However, complex surface topographies and heterogeneous compositions of art samples represent significant challenges for the general optimization of this technique. In particular, aggregation of immuno-SERS nanoparticles can lead to non-specific SERS response across the sample surface, resulting in inaccurate identification of binding media or dubious localization maps. This aggregation also diminishes the sample area available for analysis, as excitation of visible nanoparticle aggregates by the Raman laser must be avoided during data collection. In the present work, we synthesize several types of immuno-SERS nanoparticles and investigate their applicability for the detection and localization of ovalbumin-rich (egg-based) binding media in art samples. Dimers of gold nanoparticles (Au NPs) connected by a Raman-active dithiolated linker are conjugated to secondary antibodies through either an amino or carboxyl functional group (SERS tags). The SERS tags display localized surface plasmon resonance (LSPR) at 532 nm. SERS spectra are acquired at 633 nm (SERS-633) in order to maximize tuning between laser excitation and LSPR, while avoiding sample burning. In an indirect immunoassay applied to replica art samples, carboxy-terminated SERS-633 tags show strong Raman reporter signal, specificity for the target protein, robust response in the presence of various inorganic pigments, and reduced aggregation on sample surfaces compared to amino-terminated or commercial SERS tags. Scanning electron microscopy (SEM) is used to visualize Au NPs bound to egg media in situ, demonstrating that carboxy-terminated SERS-633 tags remain as discrete dimer units throughout the assay.
Analytical and bioanalytical chemistry, Jan 15, 2015
A systematic study on the influence of pigments and sample aging on casein identification was per... more A systematic study on the influence of pigments and sample aging on casein identification was performed on 30 reconstructed paints. The protein in all the paints was extracted into solution for analysis. The amount of protein that can be retrieved for solution-based analysis in each of the reconstructed paints was studied with a well-developed NanoOrange method before and after artificial aging. The results showed that in the paints with calcium phosphate (in bone black) and copper carbonate, hydroxide, or acetate (in verdigris and azurite), the amount of protein that can be retrieved for liquid-phase analysis is much smaller than the other paints, indicating that the protein degradation was accelerated significantly in those paints. Carbon (in vine black), calcium carbonate (in natural chalk), and calcium sulfate (terra alba gypsum and ground alabaster) did not affect much the amount of protein that can be retrieved in the paints compared to non-pigmented binder, meaning that the p...
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
The search for stable varnishes which will saturate and provide a desired finish for a variety of... more The search for stable varnishes which will saturate and provide a desired finish for a variety of painted and decorative surfaces is ongoing. Varnish blends were investigated, composed of ratios from 2% to 98%, of Laropal A81 (a highly stable and commercially available low molecular weight urea‐aldehyde resin) in Paraloid B‐72, in order to capitalise on the positive properties of the individual resins and allow tailoring for specific surface problems in a single application. Aspects relevant to appearance and practice are reported in this paper. The structure of dried films was microscopically examined and their refractive index (RI) measured. Their effect on painted surfaces was evaluated through both instrumental measurement of specular gloss and saturation, and through subjective evaluation, which was influenced by diffuse as well as specular reflectance. Dried films of the entire range of blends were found to exhibit useful optical and aesthetic properties on a variety of paint surfaces, although it was felt that blends at either end of the range produced the most promising varnishes. Although the blends produced films that were phase separated, this did not cause any detrimental optical effects and may even contribute to the range of achievable surface effects. Subjective evaluation of appearance and working properties is shown to be important in any such investigation.
There are several analytical techniques currently in use in conservation science to identify prot... more There are several analytical techniques currently in use in conservation science to identify proteins in artworks. However, as is often the case, the determination of the exact location of a protein in a complex layer structure is challenging due to difficulty in separating layers. Localization of the protein in a cross-section has been demonstrated through attenuated total reflectance-Fourier transform infrared mapping and imaging as well as chemiluminescent and fluorescent-labeled antibodies; however, these techniques either require expensive instrumental setups or produce results that can be challenging to interpret. This paper will present research using surface-enhanced Raman scattering (SERS) nanotags complexed to secondary antibodies in conjunction with primary antibodies for the localization of ovalbumin, collagen, and casein in cross-sections from replicas and artworks containing avian egg, animal glue, or casein binders. The advantages of this technique over the others are (1) the detection method is a Raman microscope, equipment found in several museum laboratories; (2) the distinctive SERS signal from the nanotag increases the detection limit of the protein and decreases the interference from other colorants present in the cross-section layers; and finally, (3) the large (120 nm) SERS-labeled antibodies do not appear to penetrate into the cross-section, eliminating the risk of spurious signal and misidentification. Any agglomerations due to surface texture are clearly visible under normal illumination and can be avoided easily during analysis or removed with a light polish. This technique not only allows protein localization in multilayered samples while preserving the stratigraphic information but also retains the protein specificity of the antibody approach. Figure
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of th... more Artists' acrylic paint surfaces can accumulate surface grime. Aqueous surface cleaning of these paints can be particularly problematic because they swell upon exposure to water and because of the presence of water extractable additives. Research to determine the parameters of ...
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