Musundi B. Wabuyele

Development of an advanced hyperspectral imaging (HSI) system with applications for cancer detection.

An advanced hyper-spectral imaging (HSI) system has been developed having obvious applications for cancer detection. This HSI system is based on state-of-the-art liquid crystal tunable filter technology coupled to an endoscope. The goal of this unique HSI technology being developed is to obtain spatially resolved images of the slight differences in luminescent properties of malignant versus non-malignant tissues. In this report, the development of the instrument is discussed and the capability of the instrument is demonstrated by observing mouse carcinomas in-vivo. It is shown that the instrument successfully distinguishes between normal and malignant mouse skin. It is hoped that the results of this study will lead to advances in the optical diagnosis of cancer in humans.

Hyperspectral surface-enhanced Raman imaging of labeled silver nanoparticles in single cells

We describe the development of an acousto-optic tunable filter (AOTF)-based hyperspectral surface-enhanced Raman imaging (HSERI) system equipped with an intensified charged coupled device and an avalanche photodiode. The AOTF device is a miniature rapid-scanning solid-state device that has no moving parts and can be rapidly tuned (microseconds) either sequentially or randomly, over a wide spectral range between 600 and 900nm [corresponding to a large relative wave number range (∼0–4500cm−1)], with respect to a 632.8nm excitation and can also acquire images at a fairly narrow band of ∼7cm−1. In this article we describe a confocal surface-enhanced Raman imaging (SERI) system developed in our laboratory that combines hyperspectral imaging capabilities with surface-enhanced Raman scattering (SERS) to identify cellular components with high spatial and temporal resolution. The HSERI system’s application to cellular imaging is demonstrated using SERS-labeled nanoparticles in cellular systems.

Surface-enhanced Raman scattering detection of chemical and biological agent simulants

Surface-enhanced Raman scattering spectra of chemical and biological agent simulants, such as dimethyl methylphonate, pinacolyl methylphosphonate, diethyl phosphoramidate, 2-chloroethyl ethylsulfide, bacillus globigii, erwinia herbicola, and bacillus thuringiensis were obtained from silver-oxide film-deposited substrates. Thin AgO films ranging in thickness from 50 to 250 nm were produced by chemical bath deposition onto glass slides. Further Raman intensity enhancements were noticed in UV irradiated surfaces due to photo-induced Ag nanocluster formation, which may provide a possible route to producing highly useful plasmonic sensors for the detection of chemical and biological agents upon visible-light illumination.

Plasmonics nanoprobes: detection of single-nucleotide polymorphisms in the breast cancer BRCA1 gene

This paper describes the application of plasmonics-based nanoprobes that combine the modulation of the plasmonics effect to change the surface-enhanced Raman scattering (SERS) of a Raman label and the specificity of a DNA hairpin loop sequence to recognize and discriminate a variety of molecular target sequences. Hybridization with target DNA opens the hairpin and physically separates the Raman label from the metal nanoparticle thus reducing the plasmonics effect and quenching the SERS signal of the label. We have successfully demonstrated the specificity and selectivity of the nanoprobes in the detection of a single-nucleotide polymorphism (SNP) in the breast cancer BRCA1 gene in a homogenous solution at room temperature. In addition, the potential application of plasmonics nanoprobes for quantitative DNA diagnostic testing is discussed.

Surface-enhanced Raman scattering (SERS) detection for chemical and biological agents

Surface-enhanced Raman scattering (SERS) spectra of chemical agent simulants such as dimethyl methylphonate (DMMP), pinacolyl methylphosphonate (PMP), diethyl phosphoramidate (DEPA), and 2-chloroethyl ethylsulfide (CEES), and biological agent simulants such as bacillus globigii (BG), erwinia herbicola (EH), and bacillus thuringiensis (BT) were obtained from silver oxide film-deposited substrates. Thin AgO films ranging in thickness from 50 nm to 250 nm were produced by chemical bath deposition onto glass slides. Further Raman intensity enhancements were noticed in UV irradiated surfaces due to photo-induced Ag nanocluster formation, which may provide a possible route to producing highly useful plasmonic sensors for the detection of chemical and biological agents upon visible light illumination.

Dual modality fluorescence and reflectance hyperspectral imaging: principle and applications

We present the principles and applications of our dual-modality fluorescence and reflectance hyperspectral imaging (DMHSI) system. In this paper we report on background work done using laser induced fluorescence (LIF) by the group in the early detection of esophageal cancer. We then demonstrate the capabilities of our new DMHSI system. The system consists of a laser, endoscope, AOTF, and two cameras coupled with optics and electronics. Preliminary results, performed on mouse tissue, show that the system can delineate normal and malignant tissue regions in real-time.

Near-Field Scanning Optical Microscopy for Bioanalysis at Nanometer Resolution

The nondestructive imaging of biomolecules in nanometer domains in their original location and position as adsorbed or deposited on a surface is of garners considerable experimental interest. Near-field scanning optical microscopy (NSOM) is an emerging technique with its astonishing resolving power of <100-nm domains, and nondestructive nature compared with other scanning probe microscopic techniques is an emerging technique to achieve this goal. At the single-molecule level of resolution, it is possible to use the NSOM as a critical tool for visualization of proteins on surfaces to obtain more fundamental information about their orientation and locality without disturbing their original orientation and position, and level of interaction with the surface. Several areas of science and medicine can benefit from this type of study especially for biomedical and biochip applications. To illustrate possible applications, imaging of green fluorescent proteins and biomolecules associated with multidrug resistance proteins in tumor cells will be demonstrated using NSOM.

Hyperspectral fluorescence imaging system for biomedical diagnostics

An advanced hyper-spectral imaging (HSI) system has been developed for use in medical diagnostics. One such diagnostic, esophageal cancer is diagnosed currently through biopsy and subsequent pathology. The end goal of this research is to develop an optical-based technique to assist or replace biopsy. In this paper, we demonstrate an instrument that has the capability to optically diagnose cancer in laboratory mice. We have developed a real-time HSI system based on state-of-the-art liquid crystal tunable filter (LCTF) technology coupled to an endoscope. This unique HSI technology is being developed to obtain spatially resolved images of the slight differences in luminescent properties of normal versus tumorous tissues. In this report, an in-vivo mouse study is shown. A predictive measure of cancer for the mice studied is developed and shown. It is hoped that the results of this study will lead to advances in the optical diagnosis of esophageal cancer in humans.

Surface-enhanced Raman scattering molecular nanoprobes

Nanoparticles are increasingly finding a wide application in the biological studies due to their unique physical and chemical properties. Colloidal nanoparticles are efficient substrate that exhibit surface-enhanced Raman scattering (SERS) phenomenon by enhancing the scattering cross-sections of conjugated Raman active molecules thus enabling highly sensitive biological probes. However, biological and medical applications would require nanoparticles to be conjugated to biomolecules. A universal approach for conjugation of mercarptoacetic acid-capped silver nanoparticles to biomolecules is described. The surface functionalized silver colloids were labeled with a Raman active dye and used for cellular imaging. We also described the use of silver nanoparticle to develop a new class of SERS nanoprobes for molecular recognition and detection of specific nucleic acid sequences.

Portable Raman integrated tunable sensor (RAMiTs) for environmental field monitoring

This paper describes a self-contained, portable Raman instrument that has been developed for environmental and homeland defense applications. The instrument consists of a 830-nm diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode for detection. The primary component of this system is the AOTF and it has been selected based on its spectral range along with its high resolution, ~7.5 cm-1. Software has been developed in house using C programming language for controlling the instrument (i.e. the AOTF frequency, the signal acquisition, etc.). Evaluation of this instrument has been performed by analyzing several standard samples and comparing to a conventional Raman system. In addition to system evaluation, this paper will also discuss potential applications of this instrument to trace detection of hazardous chemicals using the Raman Integrated Tunable Sensor (RAMiTs) coupled with surface-enhance Raman scattering process.