pH-dependent protein adsorption on mesoporous silica nanoparticle (MSN) was examined as a unique means for pH monitoring. Assuming that the degree of protein adsorption determines the distance separating protein molecules, we examined the feasibility of nanoscale pH probes based on fluorescence resonance energy transfer (FRET) between two fluorescent proteins (mTurquoise2 and mNeonGreen, as donor and acceptor, respectively). Since protein adsorption on MSN is pH-sensitive, both fluorescent proteins were modified to make their isoelectric points (pIs) identical, thus achieving comparable adsorption between the proteins and enhancing FRET signals. The adsorption behaviors of such modified fluorescent proteins were examined along with ratiometric FRET signal generation. Results demonstrated that the pH probes could be manipulated to show feasible sensitivity and selectivity for pH changes in hosting solutions, with a good linearity observed in the pH range of 5.5–8.0. In a demonstration test, the pH probes were successfully applied to monitor progress of enzymatic reactions. Such an “in situ-assembling” pH sensor demonstrates a promising strategy in developing nanoscale fluorescent protein probes. [Figure not available: see fulltext.].
Bibliographical noteFunding Information:
This work was sponsored by Shanghai Pujiang Program (16PJ1402500), National Natural Science Foundation of China (21672065, 21303050 and 31471659), and the National Special Fund for State Key Laboratory of Bioreactor Engineering (grant number 2060204).
© 2017, Springer-Verlag GmbH Germany.
- Fluorescent proteins
- In situ-assembling
- Mesoporous silica nanoparticle
- pH probes