Composite Materials and Films Based on Melanins, Polydopamine, and Other Catecholamine-Based Materials

A Study of the Peculiarities of the Formation of a Hybrid Interface Based on Polydopamine between Dental Tissues and Dental Composites, Using IR and Raman Microspectroscopy, at the Submicron Level

The creation of buffer (hybrid) layers that provide improved adhesion to two heterogeneous materials is a promising and high-priority research area in the field of dental materials science. In our work, using FTIR and Raman microspectroscopy at the submicron level in a system of dental composites/intact dental enamel, we assessed the molecular features of formation and chemically visualized the hybrid interface formed on the basis of a nature-like adhesive, polydopamine (PDA). It is shown that a homogeneous bioinspired PDA-hybrid interface with an increased content of O-Ca-O bonds can be created using traditional methods of dental tissue pretreatment (diamond micro drilling, acid etching), as well as the subsequent alkalinization procedure and the developed synthesis technology. The development of the proposed technology for accelerated deposition of PDA-hybrid layers, as well as the creation of self-assembled biomimetic nanocomposites with antibacterial properties, may in the future find clinical application for minimally invasive dental restoration procedures.

Nanostructured Ceria: Biomolecular Templates and (Bio)applications

Ceria (CeO2) nanostructures are well-known in catalysis for energy and environmental preservation and remediation. Recently, they have also been gaining momentum for biological applications in virtue of their unique redox properties that make them antioxidant or pro-oxidant, depending on the experimental conditions and ceria nanomorphology. In particular, interest has grown in the use of biotemplates to exert control over ceria morphology and reactivity. However, only a handful of reports exist on the use of specific biomolecules to template ceria nucleation and growth into defined nanostructures. This review focusses on the latest advancements in the area of biomolecular templates for ceria nanostructures and existing opportunities for their (bio)applications.

New insight into melanin for food packaging and biotechnology applications

Melanin is a dark brown to black biomacromolecule with biologically active multifunctional properties that do not have a precise chemical structure, but its structure mainly depends on the polymerization conditions during the synthesis process. Natural melanin can be isolated from various animal, plant, and microbial sources, while synthetic melanin-like compounds can be synthesized by simple polymerization of dopamine. Melanin is widely used in various areas due to its functional properties such as photosensitivity, light barrier property, free radical scavenging ability, antioxidant activity, etc. It also has an excellent ability to act as a reducing agent and capping agent to synthesize various metal nanoparticles. Melanin nanoparticles (MNP) or melanin-like nanoparticles (MLNP) have the unique potential to act as functional materials to improve nanocomposite films' physical and functional properties. Various food packaging and biomedical applications have been made alone or by mixing melanin or MLNP. In this review, the general aspects of melanin that highlight biological activity, along with a description of MNP and the use as nanofillers in packaging films as well as reducing and capping agents and biomedical applications, were comprehensively reviewed.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.

Unconventional Constituents and Shared Molecular Architecture of the Melanized Cell Wall of C. neoformans and Spore Wall of S. cerevisiae

The fungal cell wall serves as the interface between the cell and the environment. Fungal cell walls are composed largely of polysaccharides, primarily glucans and chitin, though in many fungi stress-resistant cell types elaborate additional cell wall structures. Here, we use solid-state nuclear magnetic resonance spectroscopy to compare the architecture of cell wall fractions isolated from Saccharomyces cerevisiae spores and Cryptococcus neoformans melanized cells. The specialized cell walls of these two divergent fungi are highly similar in composition. Both use chitosan, the deacetylated derivative of chitin, as a scaffold on which a polyaromatic polymer, dityrosine and melanin, respectively, is assembled. Additionally, we demonstrate that a previously identified but uncharacterized component of the S. cerevisiae spore wall is composed of triglycerides, which are also present in the C. neoformans melanized cell wall. Moreover, we identify a tyrosine-derived constituent in the C. neoformans wall that, although it is not dityrosine, is a non-pigment constituent of the cell wall. The similar composition of the walls of these two phylogenetically distant species suggests that triglycerides, polyaromatics, and chitosan are basic building blocks used to assemble highly stress-resistant cell walls and the use of these constituents may be broadly conserved in other fungal species.

Facile and Controllable Growth of β-FeOOH Nanostructures on Polydopamine Spheres

Polydopamine (PDA) has a wide range of applications in biomedicine due to its high biocompatibility and surface chemistry and because of the presence of many functional groups in it, enabling further modification. As a catechol-like material, it has chelation properties for various types of metal ions, including iron. Here, we developed a procedure that uses PDA as a template to grow iron structures β-FeOOH directly on its surface. The innovative approach of this work relies on that these structures can be obtained in neutral conditions and selective iron-ion source. The influence of iron-ion source, environment, and solution concentration on the structure and amount of resulting material is presented. The growth has been characterized over time, taking into account their photothermal, magnetic, and colloidal stability properties. Moreover, we shed new light on understanding the interaction of PDA with iron ions for the growth of iron-based nanostructure on polydopamine particles. Finally, we predict that PDA@β-FeOOH nanoparticles could be a promising material in dual therapy merging photothermal therapy (PTT) treatment and magnetic resonance imaging (MRI) contrast agents.

Polydopamine Surface Chemistry: A Decade of Discovery

Polydopamine is one of the simplest and most versatile approaches to functionalizing material surfaces, having been inspired by the adhesive nature of catechols and amines in mussel adhesive proteins. Since its first report in 2007, a decade of studies on polydopamine molecular structure, deposition conditions, and physicochemical properties have ensued. During this time, potential uses of polydopamine coatings have expanded in many unforeseen directions, seemingly only limited by the creativity of researchers seeking simple solutions to manipulating surface chemistry. In this review, we describe the current state of the art in polydopamine coating methods, describe efforts underway to uncover and tailor the complex structure and chemical properties of polydopamine, and identify emerging trends and needs in polydopamine research, including the use of dopamine analogs, nitrogen-free polyphenolic precursors, and improvement of coating mechanical properties.

Bioinspired Catechol-Based Systems: Chemistry and Applications

Catechols are widely found in nature taking part in a variety of biological functions, ranging from the aqueous adhesion of marine organisms to the storage of transition metal ions [...].

Colour-Value Based Method for Polydopamine Coating-Stability Characterization on Polyethersulfone Membranes

Porous polyethersulfone membranes as used in oenology were investigated in order to evaluate temperature-dependent permeances in a temperature range from 10 to 35 °C. A temperature correction factor was determined for this type of membrane to get accurate and comparable results for further developments. Moreover, the membranes were modified with a bio-inspired polydopamine coating in order to reduce fouling. The performance of the membranes could be increased with respect to permeance and flux recovery under cross-flow conditions. In order to test the applicability and stability of the coating layer, they were treated with basic and acidic cleaning agents as used in industry for fouled membranes. The chemical stability of the coating layer was studied under basic and acidic conditions, by systematic observation of the colour change of the coated membranes over treatment time.