High-throughput extracellular pH monitoring and antibiotics screening by polymeric fluorescent sensor with LCST property

Methods. 2019 Sep 15;168:51-61. doi: 10.1016/j.ymeth.2019.04.017. Epub 2019 Apr 30.


Monitoring extracellular pH (pHe) is important for biology understanding, since pHe and its homeostasis are closely relevant to cellular metabolism. Hydrogel-based pHe sensors have attracted significant attention and showed wide application, while they are tedious with significant time-cost operation and reproducibility variations for high-throughput application. Herein, we synthesized two polymers for pHe monitoring which are soluble in water at room temperature with easy operations and high reproducibility among various micro-plate wells for high-throughput analysis. P1 (P(OEGMA-co-MEO2MA-co-pHS)) and P2 (P(OEGMA-co-pHS)) were synthesized via the Reversible Addition Fragmentation Chain Transfer (RAFT) copolymerization of oligo(ethylene glycol) methacrylate (OEGMA), 2-(2'-methoxyethoxy) ethyl methacrylate (MEO2MA) and the pH sensitive fluorescence moiety N-fluoresceinyl methacrylamide (pHS). P1 is soluble in water at room temperature (25 °C) while insoluble at the temperature above 33 °C, indicating its feature of lower critical solution temperature (LCST) at 33 °C. Further P1 showed higher pH sensitivity and photostability than P2 (without LCST property) when used at physiological temperature (37 °C). Thus, P1 was chosen to in-situ monitor the micro-environmental acidification of E. coli, Hela and Ramos cells during their growth, and the metabolism inhibiting activity of a representative antibiotic, ampicillin. Cell concentration-dependent cellular acidification and drug concentration-dependent inhibition of cellular acidification were observed, demonstrating that the LCST polymer (P1) is suitable for real-time cellular acidification monitoring as well as for high-throughput drug screening. This study firstly demonstrated the use of a LCST polymeric sensor for high-throughput screening of antibiotics and investigation of cell metabolism.

Keywords: Antibiotics activity; Extracellular pH monitoring; Lower critical solution temperature; Polymers; pH Sensors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry*
  • Anti-Bacterial Agents / pharmacology
  • Cell Line, Tumor
  • Cell Respiration
  • Drug Carriers / chemistry*
  • Escherichia coli / metabolism
  • Fluorescent Dyes / chemistry*
  • HeLa Cells
  • Humans
  • Hydrogels / chemistry
  • Hydrogen-Ion Concentration
  • Methacrylates
  • Photochemistry
  • Polymerization
  • Polymers / chemistry*
  • Reproducibility of Results
  • Temperature


  • Anti-Bacterial Agents
  • Drug Carriers
  • Fluorescent Dyes
  • Hydrogels
  • Methacrylates
  • Polymers