Kenneth Squire did not know what to expect when attending his first academic conference — SPIE Photonics West 2018, a conference about light-based science and technology. So, he was pretty surprised to take home two awards.

“It’s really exciting to get that recognition and to know that I am capable of doing research and presenting my findings at that level,” said Squire, a graduate student in electrical and computer engineering in the College of Engineering at Oregon State University.

Squire’s research advances techniques to detect antigens such as biotoxins that can infect food or biomarkers for disease. His research is under the direction of Alan Wang, associate professor of electrical and computer engineering who heads the Engineering Photonics Research Laboratory in the School of Electrical Engineering and Computer Science.

The paper for which Squire received the Prizmatix Young Investigator Award was “Ultra-sensitive fluorescent imaging-biosensing using biological photonic crystals.”

In this research, Squire, along with Dr. Xianming Kong and other collaborators, were able to enhance the optical signals for florescence imaging using diatoms, which are single-celled algae.

“The hope is that this can be used for cellphone based biosensors,” Squire said. Sensitivity is the challenge for developing sensors that can be used outside of pristine laboratory conditions.

“Using these diatoms, we were able to enhance the sensitivity. So, even though your equipment isn’t quite as good, and even though you don’t have the perfect conditions, you can still get detection levels that are practical,” Squire said.

They have applied for a patent on the technology and are currently working on an application to detect a biomarker for cardiovascular disease.

Squire’s second award at the conference was runner up for Best Student Presentation for his paper entitled, “Facile detection of toxic ingredients in seafood using biologically enabled photonic crystal materials.“

This research utilized the fossilized remains of diatoms, called diatomaceous earth, which is sometimes used for filters. The device that Squire, Kong and collaborators developed was able to separate the target from other material in the sample, and enhance the optical signals for better detection of biotoxins that can infect food.

The study demonstrated successful detection of Sudan I, an illegal carcinogenic dye, in various chili products, and histamine, a naturally occurring toxin, in seafood that was intentionally contaminated and in decomposing tuna.

The device, called a thin layer chromatography plate, separates the target molecule from the rest of the sample matrix and enhances the performance of the detection.  The detection method that was employed uses scattered light from a laser which creates a unique fingerprint for different molecules (surface-enhanced Raman scattering).

“The Photonics West conference was a great opportunity to present our work.  Leading up to the conference, many of our group members were instrumental in the preparation and polishing of the presentations that led to these awards and I am very grateful to them for their help and support,” Squire said.

Abstracts

Ultra-sensitive fluorescent imaging-biosensing using biological photonic crystals

Kenneth Squire, Xianming Kong, Paul LeDuff, Gregory Rorrer, Alan X. Wang

Optical biosensing is a growing area of research known for its low limits of detection.  Among optical sensing techniques, fluorescence detection is among the most established and prevalent.  Fluorescence imaging is an optical biosensing modality that exploits the sensitivity of fluorescence in an easy-to-use process. Fluorescence imaging allows a user to place a sample on a sensor and use an imager, such as a camera, to collect the results.  The image can then be processed to determine the presence of the analyte.  Fluorescence imaging is appealing because it can be performed with as little as a light source, a camera and a data processor thus being ideal for nontrained personnel without any expensive equipment.  Fluorescence imaging sensors generally employ an immunoassay procedure to selectively trap analytes such as antigens or antibodies.  When the analyte is present, the sensor fluoresces thus transducing the chemical reaction into an optical signal capable of imaging.  Enhancement of this fluorescence leads to an enhancement in the detection capabilities of the sensor.  Diatoms are unicellular algae with a biosilica shell called a frustule.  The frustule is porous with periodic nanopores making them biological photonic crystals.  Additionally, the porous nature of the frustule allows for large surface area capable of multiple analyte binding sites.  In this paper, we fabricate a diatom based ultra-sensitive fluorescence imaging biosensor capable of detecting the antibody mouse immunoglobulin down to a concentration of 1 nM.  The measured signal has an enhancement of 6× when compared to sensors fabricated without diatoms.

Facile detection of toxic ingredients in seafood using biologically enabled photonic crystal materials

Xianming Kong, Kenneth Squire, and Alan X. Wang

Surface-enhanced Raman scattering (SERS) spectroscopy has attracted considerable attention recently as a powerful detection platform in biosensing because of the wealth of inherent information ascertained about the chemical and molecular composition of a sample. However, real-world samples are often composed of many components, which renders the detection of constitutes of mixed samples very challenging for SERS sensing. Accordingly, separation techniques are needed before SERS measurements. Thin layer chromatography (TLC) is a simple, fast and cost-effective technique for analyte separation and can a play pivotal role for on-site sensing. However, combining TLC with SERS is only successful to detect a limited number of analytes that have large Raman scattering cross sections. As a kind of biogenic amine, histamine (2-(4-imidazolyl)-ethylamine) has a relationship with many health problems resulting from seafood consumption occurring worldwide. Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. As a kind of natural photonic biosilica from geological deposits, it has a variety of unique properties including highly porous structure, excellent adsorption capacity, and low cost. In addition, the two dimensional periodic pores on diatomite earth with hierarchical nanoscale photonic crystal features can enhance the localized optical field. Herein, we fabricate TLC plates from diatomite as the stationary phase combining with SERS to separate and detect histamine from seafood samples. We have proved that the diatomite on the TLC plate not only functions as stationary phase, but also provides additional Raman enhancement, in which the detection limit of 2 ppm was achieved for pyrene in mixture.