The biomarkers of many diseases such as malaria can be found in intradermal measurements. We will present two surface enhanced Raman spectroscopy (SERS) based methods for the detection of malaria biomarkers in blood, which are comparable to or outperform the standard clinical method. To eliminate the need of drawing blood, we will also report a stainless-steel microneedle based probe for direct intradermal SERS measurements. Moreover, we developed a deformable agarose needle to reduce the risk of sharp injury and cross contamination due to needle reuse. Tests in skin phantoms for glucose measurements demonstrated accuracy comparable to those traditional methods requiring blood drawing.

Shifted excitation Raman difference spectroscopy (SERDS) will be presented using customized diode lasers for the excitation. Here, hybrid diode laser based light sources at 671 nm and 488 nm and monolithic devices at 671 nm and 785 nm are shown as an example. Electro-optical and spectral properties are discussed with respect to the application. Raman experiments demonstrate their suitability as an excitation source for SERDS. The hybrid and monolithic concepts are transferable to other wavelengths. A portable SERDS sensor system including an in-house developed handheld probe is realized for in-situ investigations and will be described. Outdoor SERDS experiments in the apple orchard are performed and demonstrate SERDS as a powerful and easy-to-use tool which improves Raman spectroscopic experiments especially for in-situ investigations.

Surface plasmon resonance microscopy (SPRM) is a powerful label-free imaging technique with spatial resolution approaching the optical diffraction limit. The high sensitivity of SPRM to small changes in index of refraction at an interface allows imaging of dynamic protein structures within a cell. Visualization of subcellular features, such as focal adhesions (FAs), can be performed on live cells using a high numerical aperture objective lens with a digital light projector to precisely position the incident angle of the excitation light. Within the cell-substrate region of the SPRM image, punctate regions of high contrast are putatively identified as the cellular FAs. Optical parameter analysis is achieved by application of the Fresnel model to the SPRM data and resulting refractive index measurements are used to calculate protein mass. FAs are known to be regions of high protein density that reside at the cell-substratum interface. Comparing SPRM with fluorescence images of antibody stained for vinculin, a component in FAs, reveals similar measurements of FA size. In addition, a positive correlation between FA size and protein density is revealed by SPRM. Comparing SPRM images for two cell types reveals a distinct difference in the protein density and mass of their respective FAs. Application of SPRM to quantify mass can greatly aid monitoring basic processes that control FA mass and growth and contribute to accurate models that describe cell-extracellular interactions.

In this report, we describe improvement of image resolution in surface plasmon resonance microscopy (SPRM) which suffers from poor quality due to severe surface plasmon (SP) propagation. Our approach takes two-channel momentum sampling by switched light incidence followed by minimum filtering to implement spatially switched SPRM (ssSPRM). The performance evaluated with periodic wires in comparison with conventional SPRM and bright-field microscopy shows that the effect of SP propagation can be circumvented and the effective decay length of SPRM is calculated to increase by only 7% compared to that of bright-field images.

A novel approach for optical biosensing can be obtained based multiphoton induced luminescence (MIL) and its dependence on plasmonic coupling. It has been shown that the proximity of spherical AuNPs determines the generation of MIL in far-field multiphoton laser scanning microscopy (MPM). A stimuli responsive contrast mediator with high sensitivity can be created by controlling the aggregated state of AuNP. In this study we explore a system based on spherical AuNPs functionalized with β-cyclodextrin and multiple β-D-lactose units (lacto-CD-AuNP). The aim of the β- D-lactose units is to target cancer cells, based on overexpression of galectin3 (Gal-3) receptors. The results demonstrate that clustering of particles, and thereby MIL signal, was only acquired from tumor cell lines, i.e., SK-MEL-28 and A431, while not from normal keratinocytes (HEKn). Thus further studies should be undertaken to translate the concept to a preclinical setting.

Plasmonic nanoparticles are excellent nonbleaching probes for bio-imaging. Due to their anisotropic properties, polarization analysis of individual nanoparticles allows for revealing orientational information, plasmon mode assignment, and the local microenvironment. Previous implementations utilize mechanical rotation of conventional polarizers to align the polarization angles with specific axes of nanoparticles. However, the manufacturing defects of the polarizer (e.g., non-parallelism) limit the measurement stability (e.g., beam wobbling) in polarimetric imaging, while the mechanical rotation limits the measurement speed, and thus hinders accurate, real-time acquisition of individual nanoparticles.

Here, we demonstrate a high-speed nano-polarimetric system for stable plasmonic bio-imaging by integrating our voltage-tunable polarizer (VTP) into a microscope. The angular rotation of the polarization (0∼π) can be realized by applying voltage on the VTP. We show that our voltage-tunable system offers high extinction ratio (∼up to 250), and uniform transmission (∼55%) over a large input power range (<5% deviation for input power from 50 μW to ∼20 mW). Meanwhile, the transmission polarization can be rapidly tuned with a response time up to 50 ms. Compared to conventional polarizers, our system is able to provide reproducible and high-speed polarimetric images of individual nanoparticles with sub-pixel spatial precision. Such a polarimetric nanoimaging system could be a useful tool for real-time single nanoparticle bio-imaging with both high stability and time resolution.

Upconverting nanophosphors (UCNPs) absorb two or more photons at 980nm and emit a higher energy photon in the visible range. UCNPs provide distinct advantages as biological imaging agents in that they have no autofluorescence, don’t photobleach, are capable of deep tissue imaging, exhibit no blinking, and are physically robust. Through surface modifications with an amphiphilic polymer, we can not only functionalize UCNPs for targeted imaging, but also tether them to plasmonic nanoparticles such as gold nanorods (AuNRs) for enhanced upconversion and multifunctionality. We developed a process to construct UCNP-AuNR nanoclusters using polyethylene glycol. The UCNP-AuNR nanocluster is further modified with an anti-epidermal growth factor receptor (aEGFR), allowing specific binding to bladder cancer cells that highly express epidermal growth factor receptor. Once the nanoclusters bind to the cell membrane we can (1) perform targeted and high contrast imaging of the bladder cancer cells and (2) utilize localized surface plasmon of AuNRs to selectively kill the cells in situ upon detection by UCNP fluorescence. Successful conjugation and integrity of the UCNP-AuNR nanoclusters were confirmed via electron microscopy. Then, through a combination of brighftield, confocal upconversion fluorescence, and infrared darkfield microscopy we demonstrate selective binding and high-contrast upconversion imaging of the bladder cancer cells. Finally, through a series of in vitro studies, we demonstrate two different methods of cell killing. First, with a continuous wave laser, we demonstrate effective thermal ablation of cells. Second, with a femtosecond pulse laser, we demonstrate optoporation of the cell membrane that allows increased uptake of drugs.

We present a theory of the microscopic origins of the surface-enhanced circular dichroism (CD) with nanostructures. Recently, nanostructures and metamaterials have been used for the enhancement of CD signals of chiral molecules. However, the complete description of microscopic origins of the surface-enhanced circular dichroism (CD) has never been achieved. We find the total CD signals of the nanostructure coupled to chiral molecules can be decomposed into two factors: the induced and inherent CD. The inherent CD comes from the molecular absorption which can be enhanced by the strongly localized optical helicity density of resonant near-fields near the nanostructure. The induced CD is originated from the asymmetric absorption of light inside the nanostructure perturbed by nearby chiral molecules upon two opposite circularly polarized light. The recent surge of interest in the surface-enhanced CD spectroscopy has been inspired by the inherent CD enhancement, but our work shows that the induced CD can significantly contribute to the total CD signal of the chiral molecule/nanostructure coupled system. Using an example of gold nanodisk arrays, we demonstrate that the inherent and induced CD can compete with each other in plasmonic nanostructures. In this presentation, we also provide design principles for CD sensor using nanostructures and metamaterials.

The use of plasmonic nanoparticles (PNPs) in biophotonics has been steadily increasing, with a wide variety of emerging applications including detection and treatment of cancers. PNPs have unique, tunable optical properties arising from their surface plasmon resonance (SPR), and can be functionalized to achieve molecular targeting in vivo. Highly transient nanobubbles generated around PNPs due to pulsed laser-induced vaporization and cavitation may significantly impact diagnostic and therapeutic procedures. While much effort has been devoted to elucidating the mechanisms behind PNP nanobubble generation, there has not been a comprehensive study on the effect of nanoparticle size on nanobubble formation thresholds, and whether particle photodegradation occurs at these levels. Herein, we evaluate the melting and bubble generation thresholds of commercially available gold nanospheres in the 20-100 nm diameter range when exposed to nanosecond laser pulses. The 532-nm laser pulses are generated by a second-harmonic Q-switched Nd:YAG laser, providing output near the SPR of the gold nanospheres. Bubble generation is detected using a multimodality microscopy platform developed for simultaneous, nanosecond resolution pump-probe imaging, scattering response monitoring, and acoustic transient detection. PNP damage was further evaluated using transmission electron microscopy and spectrophotometry. The results of this study provide insights into damage thresholds as well as the concurrent and rapid optical, thermal, acoustic, and mechanical phenomena involved. This work will provide a foundation for improved understanding of a variety of PNPs and inform development of standard test methods for safety and efficacy evaluation of pulsed laser-PNP interactions in biophotonics.

Cell signaling activities play a critical role in physiological and disease processes. The analysis of the tumor microenvironment or the immune system activation is nowadays providing valuable insights towards disease understanding and novel therapies development. Due to the various dynamic profiles, it is essential to implement a continuous monitoring methodology for accurate analysis. The current fluorescent and colorimetric approaches hinder such applications due to their multiple time-consuming steps, molecular labeling, and the ‘snapshot’ endpoint readouts. Photonics technology, and especially nanoplasmonic biosensors offer a unique opportunity to implement lab-on-a-chip systems that provide highly sensitive and label-free analysis of cell signaling events in real time. Here, we will present a microfluidics-integrated nanoplasmonic biosensor for long-term and real-time monitoring of cell secretion activity. The biosensor consists of a gold nanohole array supporting extraordinary optical transmission (EOT), which has been optimized to enable ultra-sensitive and high-throughput biomolecular detection. The nanobiosensor is integrated with a specifically designed microfluidic system that provides well-controlled cell culture conditions for long-term monitoring. We achieved an outstanding sensitivity for the detection of vascular endothelial growth factor (VEGF) directly secreted from microfluidic-cultured cancer cells. We demonstrated real-time monitoring for over 10 hours, preserving good cell viability. The multiplexing capability of our nanobiosensor could enable simultaneous analysis of different cell types and molecules-of-interest. Thus, our innovative approach of probing live cells can be a powerful tool to evaluate cellular activities for diagnostics and novel therapy development.

About sixty years ago, the biological cell counter with an electrical currents detection technique through a micrometer size orifice was invented by Dr. Coulter. A couple of years ago, the ultrafast portable pore device (MinION) with an electrical detection technique was manufactured by Oxford Nanopore Technology. However, high error rates over 80% from this solid state nanopore device is initially reported in several journals. The high error rates may have been contributed from the electrical double layer formed in the pore channel. Even though the error rates have been reduced significantly. Considering the fact that most biosensors are utilizing the optical detection technique, the optical pore device can be an excellent candidate for the next generation single molecule sensor. We will report the fabrication process of the plasmonic optical nanopores.

This work is based on surface plasmon (SP’s) confinement in nano-slots of double slot ring resonator structure, which can employ for diverse liquid sensors and cause of anemia in homosapiens. The structure is depicted using hybrid plasmonic waveguides (HPW) due to its absolute attribute of longer propagation length of SP’s. The structure of waveguide is delineated in such a way that optical energy is extreme mainly in narrow slots of two metallic layers. The HPW based sensor is used to detect the causes of anemia which is very common and severe almost among every step of age. The compatibility and capability of sensor will be analyzed by calculating its sensitivity, quality factor and figure of merit.

The implementation of multiplexed point-of-care biosensors is a top priority to address the current epidemic problems originated by widespread pathogenic infections, like those caused by viruses or bacteria. A rapid and accurate detection, identification, and quantification of the infectious pathogens is essential not only to facilitate a prompt treatment but also to prevent onward transmission, reduce economic expenses, and significantly promote healthcare in resource-constrained environments. We have developed a nanoplasmonic biosensor based on nanohole arrays for fast and highly sensitive analysis in a simple and direct configuration. Our microarray is integrated into a microfluidic system to allow for highthroughput detection of multiple targets in a few minutes, without the need of sample pretreatment or amplification steps. Previously, we demonstrated the utility of the biosensor for the detection of hazardous live viruses, such as the Ebola or Vaccinia viruses, measured directly in biological media. Most recently we proved the truly multiplexing capability of our plasmonic microarray with the simultaneous identification and quantification of Chlamydia trachomatis and Neisseria gonorrhoeae in urine samples. We are able to detect and distinguish the two different bacteria with detection limits in the range of 10² -10³ bacteria/mL. With recent advances in plasmonics, optimized surface chemistry, and microfluidics integration, our biosensors could provide a non-invasive and rapid diagnosis at the point of care, especially when we combine the detection on a compact and low-cost optical reader.

A surface plasmon resonance based fiber optic sensor for the detection of triacylglycerides (TG) has been fabricated by immobilizing lipase enzyme (Lip11) on Zinc Oxide (ZnO) nanorods grown over a silver (Ag) film. The sensor probe exhibits high sensitivity for 0–500 mg/dl triacylglyceride concentration, which covers both the physiological range and high levels (which indicate coronary heart disease and hyperlipoprotenimia). After coating a silver layer of 40 nm on the fiber surface by the thermal evaporation, the ZnO nanorods are grown over the silver layer by first preparing nanoparticles (NPs) of ZnO using the Pacholski method. The silver coated fiber is then dipped into the ZnO nanoparticles solution and the ZnO NPs work as a seed layer for the growth of ZnO nanorods on the fiber surface. Here, ZnO nanorods play a double role in the sensing operation. They act as a matrix with high isoelectric point (9.5) which makes it possible to directly immobilize lipase enzyme which has low isoelectric point (4.9) by electrostatic adsorption without any requirement of functionalization. Second the ZnO nanorods layer enhances the sensitivity of the sensor as it works as a high index layer over the metal layer. As the concentration of TG change in the vicinity of the sensor, the refractive index and thickness of bio-recognition enzyme layer change and as a consequence the resonance wavelength in the absorbance spectra changes. The sensor has a fast response, high selectivity and sensitivity, low cost, label free detection and ease of fabrication.

Frequency comb has shown remarkable potential in time/frequency metrology, atomic/molecular spectroscopy and precision LIDARs. It will create novel possibilities in nano-photonics and plasmonics; however, its interrelation with surface plasmons is unexplored despite the important role that plasmonics play in nonlinear spectroscopy and quantum optics through the manipulation of light in a subwavelength scale. We demonstrate that frequency comb can be transferred by plasmonic nanostructures without noticeable degradation of less than 6.51×10^-19 in absolute position and 1 Hz in linewidth, which implies frequency comb’s potential applications in nanoplasmonic spectroscopy, quantum metrology and subwavelength photonic circuits.

Surface plasmon resonance (SPR) at planar metal/dielectric interfaces and localised SPR (LSPR) for metal nanoparticles have both been extensively studied, but it is less clear what happens to the optical properties of surface plasmon-polaritons (SPPs) at the micrometer scale. This paper characterises the angular responses of microscale gold patterns on a glass substrate using an SPR imaging configuration using a high numerical aperture objective lens. The potential use for biosensing is also discussed.

The propagation length of a SPP equals approximately 10 μm, so the geometries that are investigated are 10 × 16, 10 × 10, 6 × 16, and 6 × 6 μm sized rectangles with 2 μm spacings. The gold patterns are photolithographically produced using an image reversal process. Bright-field microscopy is used to investigate their morphology and stylus profilometry is used to check the gold thickness. The SPR responses were compared to planar gold film to see if they were characteristic and confirm the relation to SPR.

All the gold microstructures present plasmonic properties. SPR dips are observed for all samples, however, they are not as sensitive and are wider than that of planar gold film. This phenomenon becomes more pronounced as the length of the gold structure decreases, because of the spatial constriction of the propagating SPP. The process suggests that the SPR technique can be successfully implemented to detect individual action potentials. Further work is required in order to achieve a reliable process and investigate the capabilities and sensitivity of the proposed technique.