Quartz Crystal Microbalance Application and In Silico Studies to Characterize the Interaction of Bovine Serum Albumin with Plasma Polymerized Pyrrole Surfaces: Implications for the Development of Biomaterials

Abstract

Plasma polymerized pyrrole/iodine (PPPy/I) microparticles and bovine serum albumin (BSA) protein have shown interesting results in experimental models for the treatment of traumatic spinal cord injury. By studying the interaction between BSA and PPPy/I by a quartz crystal microbalance (QCM) and docking, we obtained important results to elucidate possible cellular interactions and promote the use of these polymers as biomaterials. These measurements were also used to characterize the adsorption process using an equilibrium constant. In addition, atomic force microscopy (AFM) was used to obtain images of the QCM surface sensors before and after BSA adsorption. Furthermore, we carried out molecular dynamics simulations and molecular docking to characterize the molecular recognition between BSA and the previously reported PPPy/I structure. For this study, we used two combinatorial models that have not been tested. Thus, we could determine the electrostatic (ΔG ele) and nonelectrostatic (ΔG nonelec) components of the free binding energy (ΔG b). We demonstrated that BSA is adsorbed on PPPy/I with an adsorption constant of K = 24.35 μ–1 indicating high affinity. This observation combined with molecular docking and binding free energy calculations showed that the interaction between BSA and both combinatorial models of the PPPy structure is spontaneous.

Interactions of Cardiac Proteins with Plasma-Synthesized Polypyrrole (PSPy) to Improve Adult Cardiomyocytes Culture

“…Furthermore, the PSPy biomaterial plays a very important role in the tissue engineering. Molecular docking studies and the determination of binding free energy demonstrate the importance of the chemical diversity of the PSPy structure because it allows us to make combinations of functional groups that are present in experimentation such as the -NH 2 and hydroxyl -OH groups, and these have been confirmed by IR studies in our research group [ 29 , 31 ]. These groups are of great influence in their interaction with proteins; hence, the interest of the study carried out in this work is that we experimentally verified the direct interaction of cardiomyocytes with the PSPy biomaterial observed in rat primary cultures.…”

“…Integrin structures. Crystallized structures of the α2β1 (PBD ID 1AOX) [ 23 ] and α5β1 (PDB ID 3VI4) [ 25 ] domains, obtained from the Protein Data Bank, were minimized using CHARMM-GUI Version 3.8 to reduce stearic clashes, a 100-step Steepest Descent algorithm [ 34 ] as was described by Serratos et al [ 31 ].…”

“…Notably, α5β1 integrin protein structure was simulated by 100 ns. Technical details for molecular simulation among trajectories can be found in Serratos et al [ 31 ], and the cluster that obtained the best ΔG b values was used for the molecular docking assays in the present work.…”

“…It is important to mention that the molecule proposed by Kumar et al [ 30 ] is based on various characterization techniques and was proposed together with several functional groups that may or may not be in the R1, R2, and R3 chains; as it is a synthesis by plasma, it is difficult to determine a unique and exact structure of the components of the molecule. In our research group, several modeling works have already been carried out using the Kumar et al molecule as a starting point for the modeling of PSPy interactions with various proteins [ 31 , 33 , 36 ]. The following ligands were designed: Model 1 has a -NH 2 group in R1, a -C≡N group in R2, and R3 with a primary amine -OH.…”

“…A PSPy model was built and modified the R3 chain in the Kumar et al structure, adding carbon atoms to make the chains longer ( Figure 4 b), to observe if the interaction is favored with integrins. Recently, Serratos et al [ 31 ] used a modified structure and confirmed that when the -NH 2 and -OH groups are in R1 and especially R3 positions of the PPPy structure, electrostatic interactions are strongly favored, then hydrogen bonds, and in minor proportion non-polar contacts in the interaction with albumin.…”