Spectroscopic and Biophysical Interaction Studies of Water-soluble Dye modified poly(o-phenylenediamine) for its Potential Application in BSA Detection and Bioimaging

Abstract

Ultrasound-assisted synthesis of water soluble poly(o-phenylenediamine) (POPD) and its doping with Acid Orange (AO), Fluorescein (Fluo) and Rhodamine-6G (R6G) dyes was carried out with a view to enhance the photophysical properties of POPD. XPS studies confirmed that doping of POPD occured through hydrogen bonding between NH group of POPD and C=O/SO − , S=O groups of the dyes. The presence of strong hydrogen bonding was also confirmed via UV-vis studies by the addition of urea and sodium chloride to the dye modified POPD adducts. Molar extinction coefficient of these adducts was found to bear a close relationship with the molecular structure. Fluorescence life time, (τ f, ) was found to be lowest (1.8 ns) for AO-POPD and highest (3.2 ns) for Fluo-POPD. The structure of AO-POPD was more strained, while that of Fluo-POPD was least strained. Intrinsic fluorescence decay constant, (k 0 f ) showed increasing values for POPD, AO-POPD, Fluo-POPD, R6G-POPD as 0.071, 0.072, 0.153, and 0.172 (10 8 s −1 ), which could be correlated to the increasing strain-free molecular structure of the adducts. Circular dichroism spectra (CD) of BSA in presence of POPD and R6G- POPD revealed that it partially broke its helical structure, while Fluo-POPD and AO-POPD showed enhancement in the helical content. The 3-D fluorescence studies confirmed enhancement in hydrophobicity of POPD and R6G- POPD and increase in hydrophylicity of AO-POP and Fluo-POPD in the microenvironment of tryptophan residue-213 of BSA. Fluo-POPD and R6G-POPD adducts were chosen to find out the lowest detection limit (LOD) of BSA by differential pulse voltammetry (DPV) which was found to be 1.35 nM, and 1.65 nM using Fluo-POPD and R6G -POPD respectively. The binding constant of BSA with Fluo-POPD- and R6G-POPD was obtained as 3.98 × 10 6 Lmol −1 and 5.27 × 10 2 Lmol −1 . These polymers could therefore, be used for the detection of BSA. Live cell imaging revealed that POPD nanoparticles were bound to the outer membrane of E . coli , while R6G-POPD, showed penetration into the cytoplasm and excellent labeling of E . coli . This facile technique could be used to design tunable biomarkers by tailoring the conjugated polymer with a desired dye molecule.

Experimental and Theoretical Studies of Novel Azo Benzene Functionalized Conjugated Polymers: In-vitro Antileishmanial Activity and Bioimaging

“…The experimental and theoretical spectra were observed to be in good agreement which confirmed the proposed chmical structure of the polymers. www.nature.com/scientificreports www.nature.com/scientificreports/ Upon excitation at 480 nm, the fluorescence spectra of PANI-AB and PPd-AB exhibited emission maxima at 570 nm while PNA-AB and PLu-AB showed broad emission humps spanning between 500-570 nm corresponding to S 1 →S o transition 22,27 , Fig. 4(a).…”

“…The values of intrinsic viscosity were calculated to be 0.41 for PANI-AB, 0.45 for PNA-AB, 0.42 for PLu-AB and 0.47 for PPd-AB. Hence, the weight average molecular weights (M w ) were presumed to be ranging between 10,500-19,000 27 . characterization Spectral analysis.…”

Synthesis, characterization, and biophysical interaction studies of water-dispersible polypyrrole/polythiophene co-oligomers with bovine serum albumin and human serum albumin: an experimental and theoretical approach

“…S1(a)), revealed a sharp peak at δ = 8.3 ppm of NH protons of pyrrole. 24 The heterocyclic ring protons adjacent to the NH group appeared at δ = 7.3 ppm and δ = 7.6 ppm. The 1 H-NMR spectrum of WD-PTh (given in the ESI† as S1(b)) exhibited a doublet peak at δ = 7.2 ppm and δ = 7.4 ppm corresponding to the protons of the heterocyclic ring of PTh.…”

Conducting polymers/zinc oxide-based photocatalysts for environmental remediation: a review

“…Polyphenylenediamines are the derivatives of polyaniline and exist in 3 isomers; ortho, meta, and para (Riaz et al 2017 , 2018 ; Jadoun et al 2021d ). Polyphenylenediamines have two free amine groups for functionalization before and after polymerization to enhance the properties of the polymer such as electroactivity, conductivity, sensitivity, thermal stability for their application in metal ions adsorption, anticorrosion coatings, sensors (Jadoun et al 2021d ), but the nanohybrids of polyphenylenediamines with ZnO are very rarely studied for photocatalysis (Jadoun et al 2017a ; Riaz et al 2019 ; Sandoval et al 2019 ). The bandgap of poly(o-phenylenediamine) ( ortho isomer) is 2.2 eV which is quite low in comparison to ZnO (Olgun and Gülfen 2014 ).…”