Catechol-cation adhesion on silica surfaces: molecular dynamics simulations

Molecular Dynamics Study of Chitosan Adsorption at a Silica Surface

Chitosan is a nontoxic biopolymer with many potential biomedical and material applications due to its biodegradability, biocompatibility, and antimicrobial properties. Here, fully atomistic molecular dynamics simulations and enhanced sampling methods have been used to study the adsorption mechanism of chitosan oligomers on a silica surface from an aqueous solution. The free energy of adsorption of chitosan on a silica surface was calculated to be 0.6 kcal mol-1 per monomer in 0.15 mol L-1 aqueous solution, which is comparable to k B T at room temperature. The loading capacity of chitosan on the silica surface was found to be 0.094 mg m-2, and it is dominated by charge compensation. Furthermore, the hydrogen bonding between chitosan and silica was analyzed. The nitrogen and hydroxyl group oxygen chitosan atoms were found to be the main contributors to the hydrogen bonding between chitosan and silica. These findings have the potential to guide the experimental design of chitosan-coated silica nanoparticles for applications such as drug delivery or additives for biopolymer food packaging.

Structure, Properties, and Applications of Silica Nanoparticles: Recent Theoretical Modeling Advances, Challenges, and Future Directions

Silica nanoparticles (SNPs), one of the most widely researched materials in modern science, are now commonly exploited in surface coatings, biomedicine, catalysis, and engineering of novel self-assembling materials. Theoretical approaches are invaluable to enhancing fundamental understanding of SNP properties and behavior. Tremendous research attention is dedicated to modeling silica structure, the silica-water interface, and functionalization of silica surfaces for tailored applications. In this review, the range of theoretical methodologies are discussed that have been employed to model bare silica and functionalized silica. The evolution of silica modeling approaches is detailed, including classical, quantum mechanical, and hybrid methods and highlight in particular the last decade of theoretical simulation advances. It is started with discussing investigations of bare silica systems, focusing on the fundamental interactions at the silica-water interface, following with a comprehensively review of the modeling studies that examine the interaction of silica with functional ligands, peptides, ions, surfactants, polymers, and carbonaceous species. The review is concluded with the perspective on existing challenges in the field and promising future directions that will further enhance the utility and importance of the theoretical approaches in guiding the rational design of SNPs for applications in engineering and biomedicine.

Sustained Delivery of the Antiviral Protein Griffithsin and Its Adhesion to a Biological Surface by a Silk Fibroin Scaffold

The protein Griffithsin (Grft) is a lectin that tightly binds to high-mannose glycosylation sites on viral surfaces. This property allows Grft to potently inhibit many viruses, including HIV-1. The major route of HIV infection is through sexual activity, so an important tool for reducing the risk of infection would be a film that could be inserted vaginally or rectally to inhibit transmission of the virus. We have previously shown that silk fibroin can encapsulate, stabilize, and release various antiviral proteins, including Grft. However, for broad utility as a prevention method, it would be useful for an insertable film to adhere to the mucosal surface so that it remains for several days or weeks to provide longer-term protection from infection. We show here that silk fibroin can be formulated with adhesive properties using the nontoxic polymer hydroxypropyl methylcellulose (HPMC) and glycerol, and that the resulting silk scaffold can both adhere to biological surfaces and release Grft over the course of at least one week. This work advances the possible use of silk fibroin as an anti-viral insertable device to prevent infection by sexually transmitted viruses, including HIV-1.

A Molecular Dynamics Model for Biomedical Sensor Evaluation: Nanoscale Numerical Simulation of an Aluminum-Based Biosensor

Metallic nanostructured-based biosensors provide label-free, multiplexed, and real-time detections of chemical and biological targets. Aluminum-based biosensors are favored in this category, due to their enhanced stability and profitability. Despite the recent advances in nanotechnology and the significant improvement in development of these biosensors, some deficiencies restrict their utilization. Hence a detailed insight into their behavior in different conditions would be crucial, which can be achieved with nanoscale numerical simulation. With this aim, an Aluminum-based biosensor is chosen to be analyzed with the help of all-atom molecular dynamics model (AA-MD), using large-scale atomic/molecular massively parallel simulator (LAMMPS). The surface properties and adsorption process through different flow conditions and various concentration of the target, are investigated in this study. In the future work, the results of this study will be used for developing a predictive model for surface properties of the biosensor. Clinical Relevance- The role of biosensors in clinical applications and early diagnosis is evident. This work provides a model for predicting the binding behavior of the target molecules on the biosensor surface in different conditions. Results demonstrate an increase in the adsorption of ethanol on the biosensor surface of 7% up to 80% with changing the velocity from 0.001 m/s to 1 m/s Although for cases with higher concentration this trend becomes complicated necessitating the implementation of machine learning models in the future works.

Poly-dopamine, poly-levodopa, and poly-norepinephrine coatings: Comparison of physico-chemical and biological properties with focus on the application for blood-contacting devices

Thanks to its simplicity, versatility, and secondary reactivity, dopamine self-polymerized coatings (pDA) have been widely used in surface modification of biomaterials, but the limitation in secondary molecular grafting and the high roughness restrain their application in some special scenarios. Therefore, some other catecholamine coatings analog to pDA have attracted more and more attention, including the smoother poly-norepinephrine coating (pNE), and the poly-levodopa coating (pLD) containing additional carboxyl groups. However, the lack of a systematic comparison of the properties, especially the biological properties of the above three catecholamine coatings, makes it difficult to give a guiding opinion on the application scenarios of different coatings. Herein, we systematically studied the physical, chemical, and biological properties of the three catecholamine coatings, and explored the feasibility of their application for the modification of biomaterials, especially cardiovascular materials. Among them, the pDA coating was the roughest, with the largest amount of amino and phenolic hydroxyl groups for molecule grafting, and induced the strongest platelet adhesion and activation. The pLD coating was the thinnest and most hydrophilic but triggered the strongest inflammatory response. The pNE coating was the smoothest, with the best hemocompatibility and histocompatibility, and with the strongest cell selectivity of promoting the proliferation of endothelial cells while inhibiting the proliferation of smooth muscle cells. To sum up, the pNE coating may be a better choice for the surface modification of cardiovascular materials, especially those for vascular stents and grafts, but it is still not widely recognized.

Stimuli-responsive degrafting of polymer brushes via addressable catecholato-metal attachments

Surface attached catecholato-metal complexes serve as polymer brush initiators with well-defined densities and enable stimuli-responsive degrafting of polymer brushes.

Molecular Dynamics Simulation Study of Adsorption of Bioinspired Oligomers on Alumina Surfaces

The adsorption of small oligomers on a model metal oxide surface was studied with atomistically detailed molecular dynamics simulations. The oligomers consisted of two different repeat units: a maleimide, which contains a catechol functional group as in the dopamine residue found in marine adhesive proteins, and a methyl acrylate. A hydroxylated alumina surface was used as the model metal oxide surface. Adsorption interactions were investigated in aqueous as well as anhydrous conditions. In anhydrous conditions, the model oligomers displayed strong adsorption interactions with the surface. However, in aqueous conditions, the adsorption interactions were significantly weakened because of the competition with the water molecules for adsorption sites near the surface. Catechol functional groups in the model oligomers were found to play an important role in adsorption interactions with the alumina surface via hydrogen bonds. However, diverse adsorption properties were observed depending on compositions and sequences of two different repeat units and self-aggregations, indicating that the hydrogen bonding capability of catechol groups is not the sole factor determining adsorption properties.

Adsorption of ethanol molecules on the Al (1 1 1) surface: a molecular dynamic study

The adsorption process of ethanol molecules on Al slabs was investigated by molecular dynamic simulations with a ReaxFF force field. The force field used in this paper has been validated by comparing adsorption energy results with quantum mechanical (QM) calculations. All simulations were performed under the canonical (NVT) ensemble. The single-molecule adsorption simulation shows that the hydroxyl group plays a more important role in the whole progress than the ethyl group. Besides, decomposition of hydroxyl groups was also observed during multimolecule adsorption processes. Simulations of adsorption processes of Al slab by ethanol molecules at different temperatures and pressures (controlled by the number of ethanol molecules) was also performed. System energy and radial distribution function (RDF) plots were invoked to describe adsorption processes and centro-symmetry parameter (CSP) analysis was adopted to study the surface properties with coating layers. Our results indicate that the whole adsorption process can be divided into two periods and the greater the pressure, the more ethanol molecules diffuse into the Al slab. How raising the temperature helps the adsorption processes is related to the initial number of molecules. The crystal structure of the Al surface will become amorphous under the constant impact of ethanol molecules.

Recent Trends in Mussel-Inspired Catechol-Containing Polymers (A Review)

Syntheses and applications of mussel-inspired polymeric materials have gained a foothold in research in recent years. Mussel-inspired chemistry coupled to Michael addition and Schiff’s base reactions was the key success for this intensive research. Unequivocally, The basic building brick of these materials is catechol-containing moiety, namely, 3,4-dihydroxyphenyl-L-alanine (L-DOPA or DOPA) and dopamine (DA). These catechol-based units within the chemical structure of the material ensure chiefly its adhesive characteristic to adherends of different natures. The newly-made catechol-bearing polymeric materials exhibit unique features, implying their importance in several uses and applications. Technology advent is being advantaged with these holdfast mussel protein-like materials. This review sheds light into the recent advances of such mussel-inspired materials for their adhesion capacity to several substrata of different natures, and for their applications mainly in antifouling coatings and nanoparticles technology.