This Small Business Innovation Research (SBIR) Phase I project concerns the development of an optical fiber biosensor platform that achieves exceptionally high sensitivity through use of a nanoscale, high refractive index, self-assembled polymer coating on the cladding surface. A rapid, specific, and sensitive detection system for methicilin-resistant Staphylococcus aureus (MRSA) and other biological analytes will be developed that is inexpensive, portable and rugged. The key innovation is the combination of ionic self-assembled multilayers (ISAMs), which allow deposition of a variety of materials including polymers and nanoparticles into multiple layers each just a nanometer thick, with turnaround point long-period gratings (TAP-LPGs), which have strong, broadband attenuation peaks that are highly sensitive to changes on the exterior of the optical fiber cladding. The TAP-LPG provides a highly sensitive, robust, inexpensive biosensor platform where the presence of target materials is detected simply by changes in the transmitted intensity at a particular wavelength, while the ISAM film amplifies the sensitivity by providing a high refractive index, high surface area, nanoscale coating on the cladding that can be readily coupled to a vast array of receptor molecules such as antibodies.
The broader impact / commercial potential of this project includes the creation of a novel, inexpensive, highly sensitive, rugged, portable biosensor platform that will allow early and rapid diagnosis of MRSA infection. The broad antibiotic resistance of MRSA makes it a particularly important target for rapid diagnosis so that the proper treatment can be promptly administered. MRSA is responsible for thousands of deaths annually in the United States and extended hospital visits for >100,000 patients per year. Further, the proposed novel biological diagnostic platform combines the precision of photonic sensing and nanotechnology with a versatile affinity binding system to make ultrasensitive measurements of biomarkers for a vast array of additional important targets for medical diagnostics, drug discovery, and environmental monitoring. In addition, the small size and low cost of the system makes it also applicable to remote and impoverished areas of the globe. Furthermore, the project will provide fundamental information on the optical properties of nanoscale self-assembled films and their interactions with biological molecules and organisms.
The goal of this Phase I SBIR project by Virgina nanoTech (VnT) and its partners at Virginia Tech is to develop a rapid, inexpensive, point-of-care, clinical device for early diagnosis of infection by methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a bacterium that has developed resistance to the vast majority of current antibiotics and causes serious systemic infections as well as a range of skin and soft-tissue infections. As a result of the rapid development of MRSA infections and the quite limited number of antibiotics that are effective against this bacterium, MRSA killed more people (>18,000) in the United States in 2005 than AIDS. In addition, MRSA-infected patients often require hospitalization (>90,000 per year), and the length of stay increases with time between infection and treatment. The increasing existence of MRSA in a wide range of healthcare and community settings has become a serious healthcare problem requiring rapid diagnosis and treatment. The standard method for identification of MRSA involves sending a sample (e.g. swab) to a centralized facility for culture and species identification, followed by growth in or on a nutrient medium containing antibiotics, such as methicilin or oxacillin. This conventional culture, identification, and susceptibility testing of MRSA requires a minimum of 1-2 days and is not amenable to rapid decision making. Our key innovation is the combination of nanoscale ionic self-assembled multilayer (ISAM) films and turnaround point long-period grating (TAP-LPG) optical fibers to enable the rapid and sensitive quantification of bound species to the surface of the optical fiber. Our prior work demonstrated the ability to detect as few as 500 cell/ml in under an hour. Our Phase I project focused on further improvements in the sensitivity and specificity of the sensor, demonstration of the technology's applicability to clinical-relevant samples, and, development of an automated first-generation prototype device. In order to achieve these objectives, we focused on four tasks. Key highlights of our accomplishments include identification of an appropriate blocking strategy to dramatically reduce the possibility of false positives, demonstration of correct identification of methicillin-resistant bacteria from methicillin-sensitive bacteria in more than forty different strains of bacteria at the very low concentrations of 104 cells/ml, demonstration of the ability to distinguish between samples taken from mice infected with MRSA and non-MRSA-bacteria, and development of an automated fluidic device prototype that has also indicated some novel approaches to further improve the method for identification of whether a sample is positive or negative.
