Colorimetric and Fluorophoric Sensors for pH Sensing in Living Cells

Executive Summary

Innovators at Michigan State University (MSU) have developed a novel method for dynamic tracking of proteins in living cells. MSU’s novel method tags proteins with a wide variety of colors, enabling several different proteins to be detected and tracked simultaneously. Using this method, multiple color variants are genetically tagged onto a protein expressed in cells, allowing proteins to be visualized over a very broad light spectrum — including bright fluorescents — as soon as they are synthesized. Unlike green fluorescent protein (GFP), which is expensive and requires significant activation time, MSU’s low-cost technology allows proteins to be detected instantaneously. The ability to track specific proteins as they are expressed can provide critical tools for pharmaceutical research and development, genetic engineering, as well as a myriad of cell and molecular biology experiments.

Description of Technology

This technology for real-time imaging in live cells provides a low-cost alternative to existing fluorescent proteins, such as green fluorescent protein. The technique also can be used to determine real-time intracellular pH in discrete intracellular locations, organelles, and cellular structures. The colorimetric or fluorescent tags can be used in a wide variety of recombinant and assay platforms to enable many research efforts, including cell based protein localization, multi-color multiplex assays, in vitro detection, purification based on colorimetric characteristics, universal conjugation dyes, transgene selection markers, and natural food and plant colorings.

Key Benefits

• Unlimited color variants: Virtually all colors and fluorescent properties can be obtained and coexpressed with a gene of interest. Absorbance and light transmission of the chromophore ligand can be modulated across the visible range to near-infrared range (425–644 nm).
• Extremely fast: Colors become visible within minutes.
• Allows for temporal control of visualization: Since the fusion protein is only fluorescent upon the addition of the fluorophore, and the fusion binds the fluorophore within seconds, proteins present within a narrow time window can be specifically visualized.
• Functions in anaerobic environments: Unlike GFP, this technology does not require molecular oxygen to become fluorescent.

Applications

• Pharmaceutical: Developing new drugs (e.g., high-throughput and highcontent screening assays)
• Medical: Pursuing new treatments and diagnostics for a variety of diseases
• Agriculture: Developing transgenic organisms and new crops
• Brain research: Analyzing brain circuitry
• Infectious disease: Researching viral entry and infection of viruses
• Cell and molecular biology:
  • Viral infection
  • Intra/Extracellular receptor-mediated binding
  • Protein expression, trafficking, post-translational modifications, and targeted degradation
  • Cellular movement, attachment, growth, programmed death, and homeostasis

Patent Status

US Patent No. 9,169,305.

Inventors: Babak Borhan, James Geiger

Tech ID: TEC2011-0092