The copolymer POPD-co-PNA quenches BSA fluorescence revealing many of its photophysical characteristics including a higher association constant and its scintillating presence on the latter.

No abstract

Biomaterials are natural or synthetic materials that are biodegradable and interact cordially with biological systems (Qu et al., 2019). These can be well-defined as a material envisioned to interface with biological systems for evaluation, treatment and replacement of organs, tissues or function of the body (Basu & Ghosh, 2017; Reis et al., 2016). They play a key role in the human health system which is attained from nature or the environment (Mir et al., 2018). Generally, biopolymers are the main class of biomaterials as biopolymers are biocompatible, biodegradable and human body-friendly (Rebelo et al., 2017). These biopolymers are further classified as biodegradable and non-biodegradable according to their nature (Andreeßen & Steinbüchel, 2019; Kabir et al., 2020). Due to their outstanding biocompatibility, biodegradable polymers are known as the best candidate for biomedical applications such as drug delivery systems, vascular grafts, surgical sutures, artificial skin, bone fixation devices, gene delivery systems, tissue engineering and diagnostic applications. Biomedical engineering is an attractive branch which deals with engineering and biology together to put on engineering materials and rudiments in the field of healthcare and medicine. Tissue engineering is also a part of it that fulfils the purposes of recovering or exchange failing or broken body tissue by merging cells, scaffolds and bioactive molecules. Scaffolds should combine various functions such as biodegradability, biocompatibility, ideal mechanical strength, adequate porosity for small molecule transportation, controllability, implantation and sterilization. Hence, natural polymers such as gelatin and chitosan are the perfect match for scaffold fabrication and synthetic aliphatic polyesters too. However, these revealed poor hydrophilicity which limits the cell attachment on surfaces and lack of sites for covalent bonding. While having their biodegradable nature, biopolymers or conventional polymers are insulators in nature so that limits the use in some biomedical applications where conducting properties of biomaterials is indispensable (George et al., 2020). In many applications of implants in the body, such as in bone fixing materials, dental materials and bone substitution materials, there is a need for such type of material showing long-term stable performance. In other applications such as controlled drug delivery, regenerative medicine, tissue engineering

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.

No abstract