Abstract:
Accurate monitoring of pH variations inside cells is important for the early diagnosis of diseases such as
cancer. Even though a variety of different pH sensors are available, construction of a custom-made
sensor array for measuring minute variations in a narrow biological pH window, using easily available
constituents, is a challenge. Here we report two-component hybrid sensors derived from a protein and
organic dye nanoparticles whose sensitivity range can be tuned by choosing different ratios of the
components, to monitor the minute pH variations in a given system. The dye interacts noncovalently
with the protein at lower pH and covalently at higher pH, triggering two distinguishable fluorescent
signals at 700 and 480 nm, respectively. The pH sensitivity region of the probe can be tuned for every
unit of the pH window resulting in custom-made pH sensors. These narrow range tunable pH sensors
have been used to monitor pH variations in HeLa cells using the fluorescence imaging technique
