Surface-enhanced spatially-offset raman spectroscopy (SESORS) in tissue analogs

Surface-enhanced, spatially-offset Raman spectroscopy (SESORS) combines the remarkable enhancements in sensitivity afforded by surface-enhanced Raman spectroscopy (SERS) with the non-invasive, sub-surface sampling capabilities of spatially-offset Raman spectroscopy (SORS). Taken together, these techniques show great promise for in vivo Raman measurements. Herein, we present a step forward for this technique, demonstrating SESORS through tissue analogs of six known and varied thickness, with a large number of distinct spatial offsets, in a back-scattering optical geometry. This is accomplished by spin-coating SERS-active nanoparticles (NPs) on glass slides, and monitoring the relative spectral contribution from the NPs and tissue sections, respectively, as a function of both tissue thickness and spatial offset of the collection probe. The results show that SESORS outperforms SERS alone for this purpose, NP signal is attainable at tissue thicknesses in excess of 6.75 mm, and that greater tissue thicknesses require greater spatial offsets to maximize NP signal, all with an optical geometry optimized for utility. This demonstration represents a step forward toward the implementation of SESORS for non-invasive, in vivo analysis

Bioanalytical measurements enabled by surface-enhanced Raman scattering (SERS) probes

Since its discovery in 1974, surface-enhanced Raman scattering (SERS) has gained momentum as an important tool in analytical chemistry. SERS is used widely for analysis of biological samples, ranging from in vitro cell culture models, ex vivo tissue and blood samples, and direct in vivo application. New insights have been gained into biochemistry, with an emphasis on biomolecule detection, from small molecules such as glucose and amino acids to larger biomolecules such as DNA, proteins, and lipids. These measurements have increased our understanding of biological systems, and significantly, they have improved diagnostic capabilities. SERS probes display unique advantages in their detection sensitivity and multiplexing capability. We highlight key considerations that are required when performing bioanalytical SERS measurements, including sample preparation, probe selection, instrumental configuration, and data analysis. Some of the key bioanalytical measurements enabled by SERS probes with application to in vitro, ex vivo, and in vivo biological environments are discussed

Aging and the Comprehension of Narrative Film

A recent theory of event segmentation states that during the perception of ongoing activity, individuals construct and update event models in working memory. This occurs by dividing activity into units (or events) and updating working memory representations at the boundaries between these events. Previous research shows that younger adults tend to segment continuous, everyday activity better than older adults, showing better agreement with group norms on the temporal location of event boundaries. However, past research has also shown that older adults have a preserved ability to comprehend events in narrative text. The present experiment tested whether age differences exist within the segmentation of ongoing activity in narrative film, and how they may differ. Results showed minimal age differences in segmentation between age groups. This supports the possibility that narrative structure may serve to support the comprehension of continuous activity for older adults

Aging and the segmentation of narrative film

The perception of event structure in continuous activity is important for understanding and remembering experience. Although the segmentation of experience into events is a normal concomitant of perceptual processing, there are individual differences in how well this segmentation is accomplished. Previous research shows that younger adults tend to segment continuous naturalistic everyday activity, such as someone washing a car, better than older adults. This suggests an age-related impairment in the perception of event structure. However, past research has also shown that older adults have a preserved ability to comprehend events in narrative text, which suggests that narrative may improve the event processing of older adults. This study tested whether there are age-differences in event segmentation at the intersection of continuous activity and narrative: narrative film. In support of the possibility that narrative structure supports event understanding for older adults, we found minimal age-differences in segmentation performance

Advances in biofunctional SERS-active nanoparticles for future clinical diagnostics and therapeutics

The synergy afforded by the combination of biofunctionalised nanoparticles and surface enhanced Raman scattering (SERS) has expanded the analytical toolbox for clinical diagnostics and therapeutics. Since their inception, SERS-active nanoparticles have been developed into biofunctional nanoparticles (BFNPs) using a variety of methods to attach biomolecules and pacification layers to nanoparticles to enable detection of various diseases or cancers in vitro and in vivo. However, while there are many reports of the use of BFNPs for diagnostic or therapeutic applications, very few are implemented in a “real” clinical setting, for example, detection of disease biomarkers in tissue or the delivery of drugs to affected cells. This review covers recent advances made in the development of BFNPs for SERS-based detection of clinical samples using in vitro and in vivo methods

Plasmonic color analysis of Ag-coated black-Si SERS substrate

Red-Green-Blue (RGB) dark-field imaging can direct the choice of laser excitation for Raman enhancements on nanostructured plasmonic surfaces. Here we demonstrate that black silicon (b-Si) is a structured surface that has been shown to effectively absorb broad wavelengths of light, but also enables surface enhanced Raman scattering (SERS) when coated with silver (Ag). Coating b-Si with increasing amounts of Ag results in increased dark-field scattering at discrete frequencies associated with localized plasmon resonances. The dark-field scattering was monitored by collecting a far-field image with an inexpensive complementary metal oxide semiconductor (CMOS) camera, similar to what is available on most mobile phones. Color analysis of the RGB pixel intensities correlates with the observed SERS intensity obtained with either green (532 nm) or red (633 nm) laser excitation in SERS experiments. Of particular note, the SERS response at 633 nm showed low spectral variation and a lack of background scattering compared to SERS at 532 nm. The difference in background suggests sub-radiant (dark or Fano resonances) may be associated with the SERS response at 633 nm and a non-resonant character of SERS. These results indicate that b-Si serves a template where Ag nucleates during physical vapor deposition. Increased deposition causes the deposits to coalesce, and at larger Ag thicknesses, bulk scattering is observed. Comparison with a high enhancement Ag SERS substrate further illustrates that a high density of plasmonic junctions, or hotspots, is important for maximizing the SERS response. The randomness of the b-Si substrate and the corresponding Ag nano-features contributes to a broadband spectral response and enhancement in SERS. Metal-coated b-Si is a promising SERS substrate due to its performance and facile fabrication