Nanofiber optical junctions for advanced biological sensing
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Designing advanced photonic materials for biological sensors will enable new point-of-care (POC) diagnostic capabilities and expand current biocompatible optical technologies. Our goal is to develop the next-generation optical chips that can be used for advanced biochemical recognition and identification. We are proposing to use subwavelength optical waveguides to detect subtle changes caused by chemical (e.g., pH, protein, DNA) interactions occurring at the interface of coupled nanofibers. The waveguides will be used to transmit light across biofunctionalized optical junctions formed between multiple waveguide cavities. These junctions can be abrupt 90° inter-wire bends or more moderate junctions formed between staggered cavities with overlapping evanescent fields. To chemically activate the intercavity regions we have chosen to use environmental-responsive (ER) materials as the sandwich material between coupled nanofibers. There is a wide selection of ER materials that will be tested on the waveguide junctions, including thermoplastic polymers, hydrogels, and biomimetic membranes (e.g., lipid bilayer) which respond to specific chemical environments by swelling or changing their shape/physical properties. As the ER materials undergoes chemical-induced shape change, the flow of light across the junction is drastically altered and identification of the chemical species can occur. The initial aims of this project will be directed at characterizing the optical performance of unmodified (i.e., no ER materials) junctions. Most of these studies will be focused on quantifying the power transfer across various coupling junctions (including orthogonal and staggered configurations) and determining if the best optical feedback for the nanofiber junctions (e.g., waveguide output or scattered light from junction). We will also be identifying the best methods of depositing ER materials at the junctions. For example, we will be experimenting with different deposition techniques (e.g., dip-coating, drop casting) and also determining if the ER materials can be directly grown into the junction (e.g., hydrogel synthesis). As we begin to understand the performance of the waveguides in the presence of ER materials, we will begin initial sensing tests on the nanofiber junctions using a pH sensitive poly(acrylic acid) (PAAc) hydrogel as the ER material.This intercavity material will be used to characterize the performance (i.e., pH sensitivity) of the optical junctions and also to demonstrate multiplexed pH detection using parallel nanofiber junctions. Concurrent with the pH sensing experiment, we will have ongoing efforts for dentifying new ER materials that can be used to detect bio-relevant species such as proteins, DNA, and antibodies. Systems to test will include various types of lipid membrane structures (e.g., nanolipoprotein particles), biofunctionalized hydrogels, and polymer-based films. The aims of this proposal are well aligned with the bio-defense missions of LLNL and the research goals of UC. By advancing biophotonic sensing devices we position the lab and UC for continued success in health related research. We anticipate generating a significant amount of high impact research that will be published in biological and physical journals at the same time stimulating tremendous interest from industrial firms. With the capability of integrating dense arrays of active transduction centers, nanofiber optical junctions offer an exciting new pathway to analytical and diagnostic instrumentation designed for applications such as pathogen detection, cancer monitoring, cellular pH sensing, and therapeutic development.