This PDF file contains the front matter associated with SPIE Proceedings Volume 9340, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Plasmonic sensors are extremely promising candidates for label-free single molecule analysis but require exquisite control over the physical arrangement of metallic nanostructures. We employ self-assembly based on the DNA origami technique for accurate positioning of individual 40 nm gold nanoparticles with gaps of 3.3±1 nm. This is probed through far field scattering measurements on individual dimers. This plasmonic coupling allows us to use surface enhanced Raman scattering (SERS) to detect a small number of dye molecules as well as short single-stranded DNA oligonucleotides in the vicinity of the dimers. This demonstrates that DNA origami is a powerful tool with great potential for a wide variety of biosensing and single-molecule applications.

Label-free detection methods of DNA bases using surface-enhanced Raman spectroscopy (SERS) have yet to be successfully utilized due to inconsistent signal readouts. We have identified the primary reason for the discrepancies in the SERS signals of nucleic acids as being caused by the charge-transfer chemical resonance of the base silver system which is dependent on excitation wavelength. Time-dependent density functional theory (TD-DFT) methods to calculate the electronic transitions and resonance Raman spectra of base silver complexes are performed, and the optimal excitation wavelength for the charge-transfer electronic transition is found for each base silver complex. The enhancement caused by the chemical resonance is then experimentally measured for adenine, cytosine, guanine and thymine at multiple excitation wavelengths. The dependence of the Raman intensity on excitation wavelength shows good agreement with the TD-DFT calculations. In order to fully achieve the maximum Raman intensity, both the electromagnetic and chemical resonance must be enhanced by the appropriate wavelength selection. Based on the optimal chemical resonance Raman wavelength, we design a SERS substrate which has an electromagnetic maximum wavelength that matches the chemical resonance wavelength. By aligning both resonances, the highest Raman intensity can be found for each base silver system. We have proven that the variance in DNA bases' Raman intensities are caused by chemical enhancement. By incorporating the chemical resonance and optimizing both the chemical and electromagnetic resonance, we believe a label-free DNA SERS based detection method can be realized.

Urine can be obtained easily, readily and non-invasively. The analysis of urine can provide metabolic information of the body and the condition of renal function. Creatinine is one of the major components of human urine associated with muscle metabolism. Since the content of creatinine excreted into urine is relatively constant, it is used as an internal standard to normalize water variations. Moreover, the detection of creatinine concentration in urine is important for the renal clearance test, which can monitor the filtration function of kidney and health status. In more details, kidney failure can be imminent when the creatinine concentration in urine is high. A simple device and protocol for creatinine sensing in urine samples can be valuable for point-of-care applications. We reported quantitative analysis of creatinine in urine samples by using stamping surface enhanced Raman scattering (S-SERS) technique with nanoporous gold disk (NPGD) based SERS substrate. S-SERS technique enables label-free and multiplexed molecular sensing under dry condition, while NPGD provides a robust, controllable, and high-sensitivity SERS substrate. The performance of S-SERS with NGPDs is evaluated by the detection and quantification of pure creatinine and creatinine in artificial urine within physiologically relevant concentration ranges.

Surface-Enhanced Resonance Raman Spectroscopy (SERRS) has great potential for improving cancer research and diagnosis. Capable of sub-femtomolar detection, and a high degree of multiplexing, SERRS is an attractive new technique for studying cancer biology. We have developed PEGylated silica-coated gold nanostars that can be tuned to match the Raman laser-light source wavelength, providing high-level SERRS/SERS enhancement when combined with various reporter molecules. Furthermore, the particles were conjugated with cyclo-RGDf/k peptide to investigate integrin expression of breast cancer cells using high-speed Raman mapping. We propose that this may provide a better understanding of the role of integrins in breast cancer invasiveness.

Surface enhancement Raman spectroscopy (SERS) has drawn much attention in recent years because its ability to greatly enhance Raman signals to allow for the detection of molecules at low concentration. When using metallic nanoparticles as SERS substrates, many studies have shown that the size of the interparticle gap significantly affects the enhancement of the Raman signals. Given that the optimal interparticle gap is as small as a few nanometers, fabricating sensitive, uniform, and reproducible SERS substrates remains challenging. Here we report a three-dimensional SERS substrate created through the assembly of core-shell nanoparticles using DNA. By using DNA of appropriate sequence and length, DNA-functionalized nanoparticles were assembled into ordered and highly packed nanostructures. The interparticle distance was precisely controlled by adjusting the design of the DNA and the thickness of the silver shell coated on the gold nanoparticles. Compared with randomly aggregated nanoparticles, the interparticle distance in the synthesized nanostructures can be more uniform and better controlled. In addition, the DNA-guided assembly process allows us to create precise nanostructures without using complex and expensive fabrication methods. The study demonstrates that the synthesized nanostructures can be used as effective SERS substrates to successfully measure the Raman signals of malachite green, a toxic compound that is sometimes illegally used on fish, as well as Fluorescein isothiocyanate (FITC) at low concentrations.

Raman imaging is an optical method that provides chemo-selective contrast, microscopic resolution and multiplexing capability. Medical applications, however, still suffer from weak signals and resulting long acquisition times. Plasmon resonance effects can drastically increase signals for Surface Enhanced Raman Scattering (SERS). Here, we present concepts towards an ideal, multimodal SERS agent for medical applications. Enhancement of intrinsic spectra of biological tissue is combined with contrast in Photoacoustic- and Magnetic Resonance Tomography, making this imaging agent highly promising for clinical radiology.

Plasmonic metal nanostructures have shown great potential in sensing, photovoltaics, imaging and biomedicine, principally due to enhancement of the local electric field by light-excited surface plasmons, the collective oscillation of conduction band electrons. Thin films of nanoporous gold have received a great deal of interest due to the unique 3- dimensional bicontinuous nanostructures with high specific surface area. However, in the form of semi-infinite thin films, nanoporous gold exhibits weak plasmonic extinction and little tunability in the plasmon resonance, because the pore size is much smaller than the wavelength of light. Here we show that by making nanoporous gold in the form of disks of sub-wavelength diameter and sub-100 nm thickness, these limitations can be overcome. Nanoporous gold disks (NPGDs) not only possess large specific surface area but also high-density, internal plasmonic “hot-spots” with impressive electric field enhancement, which greatly promotes plasmon-matter interaction as evidenced by spectral shifts in the surface plasmon resonance. In addition, the plasmonic resonance of NPGD can be easily tuned from 900 to 1850 nm by changing the disk diameter from 300 to 700 nm. The coupling between external and internal nanoarchitecture provides a potential design dimension for plasmonic engineering. The synergy of large specific surface area, high-density hot spots, and tunable plasmonics would profoundly impact applications where plasmonic nanoparticles and non-plasmonic mesoporous nanoparticles are currently employed, e.g., in in-vitro and in-vivo biosensing, molecular imaging, photothermal contrast agents, and molecular cargos.

Surface Plasmon Resonance (SPR) is a wave phenomenon occurring at a metal-dielectric interface. A SPR-based biosensor operates by monitoring changes in the refractive index close to the interface that are produced in response to the interaction between the analyte and the receptors immobilized on the metal’s surface. The performance of these sensors depends on many parameters, including channel geometry, material properties and parameters related to chemical interaction between the analyte and immobilized receptors. This paper presents an integrated model that predicts the sensitivity of an SPR-based sensing platform under the Kretschmann configuration. The model uses the analytical solution of the differential equations that describe the analyte-bioreceptor interaction to correlate changes in analyte concentration to changes in refractive index at the sensing surface. These results are then connected with COMSOL simulations that relate changes in refractive index to changes in the SPR reflectivity curves. The resultant relations are integrated and the model is evaluated under different scenarios. This model will aid in the optimization of assay parameters prior to experimentation for maximum sensitivity; saving both time and expensive chemical reagents during the experimental phase.

Surface plasmon resonance (SPR) sensors have become valuable analytical sensors for biomolecule detection. While SPR is heralded with high sensitivity, label-free and real-time detection, nonspecific adsorption and detection of ultralow concentrations remain issues. Nonspecific adsorption can be minimized using adequate surface chemistry. For example, we have employed peptide monolayers to reduce nonspecific adsorption of crude serum or cell lysate. It is important to uncover the nature of molecules nonspecifically adsorbing to surfaces in these biofluids, to further improve understanding of the nonspecific adsorption processes. Mass spectrometry (MS) provides a complementary tool to SPR to identify biomolecule adsorbed to surface. Trypsic digestion of the proteins adsorbed to surfaces led to identification of characteristic peptides from the proteins involved in nonspecific adsorption. Nonspecific adsorption in crude cell lysate results mainly from lipids, as confirmed with SPR and MS but proteins were observed on some surfaces. In another application of SPR and MS, imaging SPR can be used in combination to imaging MS to image tissue sections. Thin sections of mouse liver were inserted in the fluidic chamber of a SPRi instrument and proteins were transferred to the SPRi chip. The SPR chip was then imaged using MALDI imaging MS to identify the biomolecules that were transferred to the SPRi chip.

We tune nanoantennas to resonate within mid-infrared wavelengths to match the vibrational resonances of C=C and C-H of the hormone estradiol. Modelling and fabrication of the nanoantennas produce plasmon resonances between 2 μm to 7 μm. The hormone estradiol was dissolved in ethanol and evaporated, leaving thickness of a few hundreds of nanometres on top of gold asymmetric split H-like shaped on a fused silica substrate. The reflectance was measured and a red-shift is recorded from the resonators plasmonic peaks. Fourier transform infrared spectroscopy is use to observe enhanced spectra of the stretching modes for the analyte which belongs to alkenyl biochemical group.

We report a versatile nanophotonic biosensing platform that enables both colorimetric detection and enhanced Raman spectroscopy detection of molecular binding events. Through the integration of electron-beam lithography, dip-pennanolithography and molecular self-assembly, we demonstrate plasmonic nanostructures which change geometry and plasmonic properties in response to molecularly-mediated nanoparticle binding events. These biologically-active nanostructured surfaces hold considerable potential for use as multiplexed sensor platforms for point-of-care diagnostics, and as scaffolds for a new generation of molecularly dynamic metamaterials.

Modulation of the cell membrane permeability by the plasmonic interaction of gold nanoparticles and short laser pulses for cell manipulation or destruction has been the objective of several recent studies. Gold nanoparticles in close vicinity to the cellular membrane are irradiated to evoke a nanoscale membrane perforation, enabling extracellular molecules to enter the cell. However, besides several basic studies no real translation from proof of concept experiments to routine usage of this approach was achieved so far.

In order to provide a reproducible and easy-to-use platform for gold nanoparticle mediated (GNOME) laser manipulation, we established an automated and encased laser setup. We demonstrate its feasibility for high-throughput cell manipulation. In particular, protein delivery into canine cancer cells is shown. The biofunctional modification of cells was investigated using the caspase 3 protein, which represents a central effector molecule in the apoptotic signaling cascade. An efficient and temporally well-defined induction of apoptosis was observed with an early onset 2 h after protein delivery by GNOME laser manipulation. Besides protein delivery, modulation of gene function using GNOME laser transfection of antisense molecules was demonstrated, showing the potential of this technique for basic science and screening purposes.

Concluding, we established GNOME laser manipulation of cells as a routine method, which can be utilized reliably for the efficient delivery of biomolecules. Its intrinsic features, being low impairment of the cell viability, high delivery efficiency and universal applicability, render this method well suited for a large variety of biomedical application.

There have been tremendous interests about the fabrication of the Au plasmonic nanopore due to its capability of the nanosize optical biosensor. We have investigated the influence of low energy electron beam irradiation on an Au nanomembrane during Au nanopore formation. In this report, the influence of electron beam irradiation on the Au nanopore formation will be reported. The nanopores on the 200 nm thick Au membrane were initially fabricated using focused ion beam (FIB) and high energy electron beam techniques such as transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). During high energy electron beam by using TEM, either a “shrinking” or a “opening” phenomenon is reported dependent on the ratio of thickness to aperture diameter. However, for a FESEM electron beam irradiation, a shrinking phenomenon is always observed. In this report, the nanopore formation during FESEM electron beam irradiation will be reported depending upon energy absorption and thermal diffusivity.

Direct SERS analysis of proteins has been mainly devoted to the characterization of short peptide fragments or to the prosthetic group of metallo-proteins due to their strong SERS response. Nonetheless, this perspective restricts the investigation to very limited peptide sequences and appears of scarce interest for a thorough characterization of the protein. We tried to overcome the above limitations by setting-up an effective platform for the structural SERS detection of proteins. Our proposal escapes the needs of a preliminary modification of the biomolecule and confers rapidity and reproducibility to the analysis. Optimal results are achieved by the use of nonspherical tipped metallic nanostructures with controlled architectural parameters and their assembly into organized bidimensional arrays including a regular distribution of hot spots for protein entrapment and detection. The investigation evidenced that both the contact points between nanoparticle corners and the holes at the interface between nanoparticles are responsible for substantial SERS activity.

Localized surface plasmon resonance (LSPR) biosensors have drawn much attention for their promising application in point-of-care diagnostics. While surface plasmon resonance (SPR) biosensing systems have been well developed, LSPR systems have the advantages of simpler and more compact setups. The LSPR peak shifts caused by the binding of molecules to the LSPR substrates, however, are usually smaller than 1 nm if no signal amplification mechanism is used. When using nanoparticles to enhance the sensitivity of LSPR biosensors, because of the short field penetration depth, the nanoparticles should be very close to the LSPR substrate to induce significant shifts in the LSPR peak position. In this study, we used DNA aptamers and gold nanorods to significantly increase the change in the LSPR peak position with the concentration of the target molecules. We have successfully used the proposed mechanism to detect 0.1 nM interferongamma (IFN-γ), a biomarker related to the diagnosis of latent tuberculosis infection. The calibration curves obtained in pure buffers and serum-containing buffers show that accurate detection can be achieved even when the sample is from complex biological fluids such as serum. Because of the enhancement in the sensitivity by the proposed sensing scheme, it is possible to use a low-cost spectrometer to build a LSPR biosensing system.

We analyze the transmission property of nanostructures made on silver and gold metal for the applications in optical biosensors. Various structures such as slit only, slit groove slit, and multiple slit and groove structures are taken into account to find the effect of various physical parameters such as number of grooves, number of slits and others on the transmission of different wavelength light sources through the structure. A broad wavelength of 400 nm to 900 nm is used to analyze the transmission through the structure. With these structures and broad light source, change in transmission intensity is analyzed with the change in the refractive index. The change in refractive index of the analyte varies transmission intensity and wavelength shift at the output beam which can be used for sensing the amount of analyte such as monitoring glucose amount on blood/saliva, hydrogen peroxide and others. The detection of these analytes can be used to detect the different disease. The analysis of the transmittance through the nanostructure can be used for the detection of several disease such as diabetes and others through the saliva, blood and others non-invasively.

We numerically investigated plasmonic properties of gold coated 300 nm core shell particles (CS). It is known that the surface plasmon decays into the medium that encompasses the metal nanoparticle. This decay converts changes in the local refractive index into a frequency shift of the SPR. In this work, the core material was polystyrene and the shell was a thin gold layer. We showed that this CS exhibits two plasmonic modes in the visible-near infrared regime. The blue end plasmonic mode was confined at the core-metal dielectric interface and the red end plasmonic mode was attributed to a surface mode that depends on dielectric properties of the surrounding medium. The application of the red end plasmonic mode as a surface plasmon resonance (SPR) sensor revealed that it exhibits wavelength shift of 764±13 nm per refractive index unit change of the surrounding medium (nm/RIU). Potential biomedical applications of these sensors are discussed.

We present a theoretical approach to single nanoparticle detection using surface plasmon scattering microscopy. Through rigorous coupled wave analysis assuming light incidence on a gold coated BK7 glass substrate under total internal reflection condition for a 200-nm polystyrene as targets attached to the gold film, it was found that surface plasmon polariton induced by incident light on the gold thin film is perturbed. As a result, parabolic waves were observed in the reflection plane. By varying angles of incidence and wavelengths, optimum incident conditions for surface plasmon scattering microscopy were obtained.

Surface enhanced Raman spectroscopy (SERS) based on plasmonic colocalization between DNA attached gold nanoparticles and silver nanoislands substrates. Raman spectra measured on a silver nanoislands substrate were observed 20 and 1.8 folds signal enhancements relative to them on a film substrate with high and low numerical apertures of lenses, respectively. By comparison between calculations and experiments results, we proved that distinct differences of the signal enhancements came from changing field of view on random nanoislands substrate. Consequently, we show that nanoislands substrates with a precise position control can be a good candidate for a SERS substrate which can achieve significant signal enhancements without a complicated lithographic process.

Brillouin spectroscopy is a powerful tool for elasticity-sensitive non-invasive optical imaging. However, its relatively weak signal strength usually results long acquisition time and poor spectral quality. In this study, enhancements of Brillouin scattering at 532 nm was observed from various acoustic modes of alkaline-earth boroaluminosilicate glass coated with periodic arrays of gold nanodisks. The similar enhancements were also observed from the bulk phonons within the various liquids (including methanol and water) covered on the gold nanodisks. This enhancement is considered to be attributed by the surface plasmons generated by the nanostructures, and is found to be dependent on their geometries (i.e., aspect ratio and diameter) of the golden nanodisks. When employing the recent advances in virtually imaged phased array (VIPA) based background-free Brillouin spectrometers, the acquisition time could even be further optimized. The results of this study suggest that nanodisk arrays can provide a platform for practical implementation of surface-enhanced Brillouin scattering analogous to other surface-enhanced spectroscopies, and suggest an approach for further reduce the integration time for Brillouin spectroscopy.

Plasmon-resonant nanoparticles attached to cell membranes, under laser treatment can temporarily increase membrane permeability. In this paper, the influence of continuous-wave and pulsed (nanosecond) laser irradiation on living cells incubated with gold nanoparticles was investigated. Gold nanospheres, nanostars, and nanorods with different functionalization were used as plasmonic agents. The dependence between increase of medium temperature on the irradiation time was showed for nanostars and nanorods with different surface properties. Cells samples incubated with gold nanorods showed the highest temperature increase. Feasibility of cell optoporation by the use of gold nanospheres with variable functionalization was demonstrated. The cell membrane permeability was successfully enhanced as shown by the uptake of the fluorescent dye upon nanosecond laser treatment. Toxicity of the nanoparticles was estimated by MTT assay.