A series of naphthalimide derivatives as intra and extracellular pH sensors

Abstract

A series of new naphthalimide derivatives were synthesized and studied. Three of the materials (SM1, SM2, and SM3) possess methacrylate(s) moieties as pH sensor monomers, enabling these compounds to be polymerized with other monomers for thin film preparation for extracellular pH sensing. Herein, poly(2-hydroxyethyl methacrylate)-co-poly(acrylamide) (PHEMA-co-PAM) was chosen as the polymer matrix. Structure influences on pH responses and pKa values were studied. The film P3 composed of the sensing moiety SM3 has a pKa close to the usual biological environmental pH of ~7. It was used as an extracellular pH sensor to monitor pH change during the metabolism of prokaryotic Escherichia coli (E. coil). On the other hand, the three sensor monomers are new intracellular biomarkers to sense lysosomes of eukaryotic cells since (1) their pKa values are in a range of 5.9 to 6.8; (2) their emission intensities at acidic conditions (such as at pH 5) are much stronger than those at a neutral condition of pH 7; (3) lysosomes range in size from 0.1 to 1.2 μm in diameter with pH ranging from 4.5 to 5.0, which is much more acidic than the pH value of the cytoplasm (usually with a pH value of ~7.2); and (4) the acidity of lysosomes enables a protonation of the amino groups of the pH probes making the sensors emit brightly in acidic organelles by inhibiting the photo-induced electron transfer from the amino groups to the fluorophores. Lysosome sensing was demonstrated using live human brain glioblastoma U87MG cell line, human cervical cancer HeLa cell line, and human esophagus premalignant CP-A and CP-D cell lines by observations of small acidic spherical organelles (lysosomes) and significant colocalizations (82 ~ 95%) of the sensors with a commercially available lysosome-selective staining probe LysoTracker Red® under confocal fluorescence microscopy.

Development of microscopic time‐domain dual lifetime referencing luminescence detection for pH monitoring in microfluidic free‐flow isoelectric focusing

“…For the pH sensitive probe 5(6)-carboxyfluorescein N-hydroxysuccinimide ester was covalently linked to an amino-modified pHEMA copolymer (amino-pHEMA) based on earlier work on the polymerization of HEMA [46,[48][49][50] by the following procedure:…”

Method for physiologic phenotype characterization at the single-cell level in non-interacting and interacting cells

“…We are developing an ATP sensor system, and are in the process of optimizing custom optical sensors that can be embedded in polymer matrices pH, K þ , and temperature sensing. [36][37][38][39] In the near future we will combine a fully automated platform developed by our group for spectrally-resolved measurement of multiparameter sensor responses, combined with a microfluidics module for serial or parallel delivery of biochemical and environmental stimuli to cells confined in arrays of microwells. We will combine metabolic profile measurements with gene transcription level profiling at the single-cell level that will be applied after phenotype characterization to establish the relationships between expression levels of specific genes and cell phenotypes.…”

A Photo-Induced Electron Transfer Based Chemosensor for the Selective Detection of Zn2+ Ions

“…Several probes for Zn 2+ and Cu 2+ have been reported [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] with 4-amino-1,8-naphthalimide as the signalling moiety, but none of them are useful for detection of both the metal ions on duel "off-on" or "on-off " modes. Generally, the fluorescence of 4-piperazino-1,8-naphthalimide derivatives is quenched due to PET arising from the piperazine nitrogen [32][33][34][35]. In the present study, binding of a Zn 2+ ion quenches the PET process, resulting in the fluorescence emission from the chemosensor.…”

“…The fluorescence of 4-piperazino-1,8-naphthalimide derivatives are usually quenched either completely or partially due to PET [32][33][34][35]. During our screening experiments involving different solvents and metal ions, probe 1 showed significant quantum of fluorescence in aqueous and non-aqueous media indicating partial quenching due to PET process.…”