Abstract
Knowledge of the interactions between polymer and protein is very important to fabricate the potential materials for many bio-related applications. In this regard, the present work investigated the effect of copolymers on the conformation and thermal stability of bovine serum albumin (BSA) with the aid of biophysical techniques such as fluorescence spectroscopy, circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC). In comparison with that of copolymer PGA-1.5, our fluorescence spectroscopy results reveal that the copolymer PGA-1, which has a lower PEGMA/AA ratio, shows greater influence on the conformation of BSA. Copolymers induced unfolding of the polypeptide chain of BSA, which was confirmed from the loss in the negative ellipticity of CD spectra. DSC results showed that the addition of PGA-1 and PGA-1.5 (0.05% (w/v) decreased the transition temperature by 14.8 and 11.5 °C, respectively). The results from the present study on the behavior of protein in response to changes in the chemical composition of synthetic polymers are significant for various biological applications such as enzyme immobilization, protein separations, sensor development and stimuli-responsive systems.
Highlights
Synthetic polymers, stimuli responsive polymers, have received extensive attention and opened a broad field of potential applications in bioimaging, drug delivery, tissue engineering and bioactive surfaces [1,2,3,4,5], due to their extraordinary response to changes in temperature, pH, ionic strength and enzymes [6,7,8,9,10,11,12,13,14]
These fluorophores can be excited at the wavelength of ~285 nm; most of the fluorescence attributed to Trp because of the efficient resonance energy transfer (RET) from tyrosine to tryptophan [46]
The stability of the model protein, bovine serum albumin (BSA), in the presence of PNIPAM based thermoresponsive copolymers with different polyethyleneglycol methacrylate (PEGMA)/acrylic acid (AA) ratios was evaluated in aqueous solution with the aid of experimental and docking studies
Summary
Stimuli responsive polymers, have received extensive attention and opened a broad field of potential applications in bioimaging, drug delivery, tissue engineering and bioactive surfaces [1,2,3,4,5], due to their extraordinary response to changes in temperature, pH, ionic strength and enzymes [6,7,8,9,10,11,12,13,14]. Poly(N-isopropylacrylamide) (PNIPAM) is a well-known environmentally sensitive polymer, which shows lower critical solution temperature (LCST) behavior in water [32] This characteristic behavior of PNIPAM aqueous systems has been studied for use in a number of biomedical fields, such as drug delivery systems [33,34], tissue engineering [35], cell therapy [36] and so on. It was shown that poly(acrylic acid)-based drug carriers were successfully applied in delivering bioadhesive drugs [38] All these excellent applications inspired us to prepare copolymers consisting of NIPAM, PEGMA and AA. Since the study of the behavior of BSA in the presence of responsive polymers plays a key role in determination of the polymer’s biocompatibility for various biomedical applications and helps in the rational design of effective therapeutic carriers, the present results may pave the way to construct PNIPAM-based biomedical devices
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