Abstract: This work aims to study the effect of pH stability and CO₂ employing on the proliferation,subculture and virus production level of MRC-5 for increasing its cells subculture capacity. Preparing cell culture medium with serial pH value by adding NaHCO₃ and monitoring the dynamic variation of pH combined with CO₂,the cell morphology and proliferation during passages in different condition were evaluated. Furthermore,the cell sensitivity to virus using varicella-zoster virus（VZV）was observed. When cell culture medium with the NaHCO₃ as buffer,the pH of culture medium in the sealed group cultured without CO₂ partial pressure fluctuated in wide range,correspondingly the cells grew aberrantly and subculture to passage 35-37 was in a significantly weakened trend. The VZV production on passage 31 cells of sealed groups was 4.64 Lg PFU/mL. On the contrary,cells under CO₂ partial pressure condition presented a superior state because pH varied gently,and this group of MRC-5 cells could subculture to passage 41 with steady cell viability upon 80%,and the VZV production on the passage 31 was 4.83 Lg PFU/mL. In conclusions,employing NaHCO₃ buffer paired with proper CO₂partial pressure is conducive to the optimization and improvement of MRC-5 cells morphologies.

Key words: cell culture, MRC-5, CO₂ partial pressure, pH stability