Colloidal strategies for electrophoretic deposition of organic-inorganic composites for biomedical applications

A Brief Insight to the Electrophoretic Deposition of PEEK-, Chitosan-, Gelatin-, and Zein-Based Composite Coatings for Biomedical Applications: Recent Developments and Challenges

Electrophoretic deposition (EPD) is a powerful technique to assemble metals, polymer, ceramics, and composite materials into 2D, 3D, and intricately shaped implants. Polymers, proteins, and peptides can be deposited via EPD at room temperature without affecting their chemical structures. Furthermore, EPD is being used to deposit multifunctional coatings (i.e., bioactive, antibacterial, and biocompatible coatings). Recently, EPD was used to architect multi-structured coatings to improve mechanical and biological properties along with the controlled release of drugs/metallic ions. The key characteristics of EPD coatings in terms of inorganic bioactivity and their angiogenic potential coupled with antibacterial properties are the key elements enabling advanced applications of EPD in orthopedic applications. In the emerging field of EPD coatings for hard tissue and soft tissue engineering, an overview of such applications will be presented. The progress in the development of EPD-based polymeric or composite coatings, including their application in orthopedic and targeted drug delivery approaches, will be discussed, with a focus on the effect of different biologically active ions/drugs released from EPD deposits. The literature under discussion involves EPD coatings consisting of chitosan (Chi), zein, polyetheretherketone (PEEK), and their composites. Moreover, in vitro and in vivo investigations of EPD coatings will be discussed in relation to the current main challenge of orthopedic implants, namely that the biomaterial must provide good bone-binding ability and mechanical compatibility.

Electrophoretic deposition of polymers and proteins for biomedical applications

This review is focused on new electrophoretic deposition (EPD) mechanisms for deposition biomacromolecules, such as biopolymers, proteins and enzymes. Among the rich literature sources of EPD of biopolymers, proteins and enzymes for biomedical applications we selected papers describing new fundamental deposition mechanisms. Such deposition mechanisms are of critical importance for further development of EPD method and its emerging biomedical applications. Our goal is to emphasize innovative ideas which have enriched colloid and interface science of EPD during recent years. We describe various mechanisms of cathodic and anodic EPD of charged biopolymers. Special attention is focused on in-situ chemical modification of biopolymers and crosslinking techniques. Recent innovations in the development of natural and biocompatible charged surfactants and film forming agents are outlined. Among the important advances in this area are the applications of bile acids and salts for EPD of neutral polymers. Such innovations allowed for the successful EPD of various electrically neutral functional polymers for biomedical applications. Particularly important are biosurfactant-polymer interactions, which facilitate dissolution, dispersion, charging, electrophoretic transport and deposit formation. Recent advances in EPD mechanisms addressed the problem of EPD of proteins and enzymes related to their charge reversal at the electrode surface. Conceptually new methods are described, which are based on the use of biopolymer complexes with metal ions, proteins, enzymes and other biomolecules. This review describes new developments in co-deposition of biomacromolecules and future trends in the development of new EPD mechanisms and strategies for biomedical applications.

Colloidal-electrochemical fabrication strategies for functional composites of linear polyethylenimine

Colloidal-electrochemical fabrication strategies have been developed for the deposition of linear polyethylenimine (LPEI) composite materials. Electrophoretic deposition (EPD) allowed for the fabrication of composite films containing Mn₃O₄ and ZnO nanoparticles, as well as advanced flame retardant materials, such as halloysite nanotubes and memory-type Al-Mg-Zr complex hydroxide (AMZ) in the matrix of the water-insoluble LPEI. A liquid-liquid extraction method has been designed for the agglomerate-free processing of AMZ particles. Efficient extraction was achieved using decylphosphonic acid as an extractor. A conceptually new polymer complex (PC)-EPD method has been developed, which is based on the use of LPEI-metal ion complexes. Proof-of-concept studies involved the fabrication of LPEI-Ni(OH)₂ and LPEI-MnOx nanocomposites. The composites showed valuable flame retardant and charge-storage properties. The analysis of basic EPD and PC-EPD mechanisms as well as complexing properties of LPEI has driven the development of new strategies for the fabrication of organic composites. Hemoglobin was used as a model protein for the fabrication of composite films. Another important finding was the fabrication of composites, containing cyclodextrin, which is a unique carrier of various functional organic molecules. EPD and PC-EPD are versatile methods, which allow for the deposition of novel LPEI based composites containing various functional materials.

Adsorption of Maleic Acid Monomer on the Surface of Hydroxyapatite and TiO2: A Pathway toward Biomaterial Composites

Poly(styrene- alt-maleic acid) adsorption on hydroxyapatite and TiO₂ (rutile) was studied using experimental techniques and complemented by ab initio simulations of adsorption of a maleic acid segment as a subunit of the copolymer. Ab initio calculations suggest that the maleic acid segment forms a strong covalent bonding to the TiO₂ and hydroxyapatite surfaces. If compared to vacuum, the presence of a solvent significantly reduces the adsorption strength as the polarity of the solvent increases. The results of first-principles calculations are confirmed by the experimental measurements. We found that the adsorbed poly(styrene- alt-maleic acid) allowed efficient dispersion of rutile and formation of films by the electrophoretic deposition. Moreover, rutile can be codispersed and codeposited with hydroxyapatite to form composite films. The coatings showed an enhanced corrosion protection of metallic implants in simulated body fluid solutions, which opens new avenues for the synthesis, dispersion, and colloidal processing of advanced composite materials for biomedical applications.

Fabrication of Mn3O4-carbon nanotube composites with high areal capacitance using cationic and anionic dispersants

Mn₃O₄-multiwalled carbon nanotube (MWCNT) electrodes for supercapacitors with high active mass loadings have been fabricated with the goal of achieving a high area normalized capacitance (C_S) and enhanced capacitance retention at high charge-discharge rates. Poly(4-styrenesulfonic acid-co-maleic acid) sodium salt P(SSA-MA) was used as a charging and dispersing agent for the fabrication of Mn₃O₄. The unique bonding properties of the MA monomers allowed efficient P(SSA-MA) adsorption on Mn₃O₄, whereas SSA monomers imparted a negative charge. Cationic ethyl violet (EV) and pyronin Y (PY) dyes were used for dispersion and charging of MWCNT. Good dispersion of the individual components and their electrostatic heterocoagulation facilitated efficient mixing, which allowed enhanced capacitive behavior at mass loadings of 28.4 mg cm^-2, which meet requirements for practical applications. The highest capacitance of 2.8 F cm^-2 was obtained at a scan rate of 2 mV s^-1 for the composites, prepared using PY. However, the composites, prepared using EV showed better capacitance retention of 88% in the scan rate range of 2-100 mV s^-1 and the capacitance of 2.1 F cm^-2 was obtained at a scan rate of 100 mV s^-1. The composites showed activation behavior during cycling, which resulted in a capacitance increase and electrical resistance reduction. The results of this investigation showed that Mn₃O₄-MWCNT composites, prepared by new colloidal methods are promising materials for practical applications in electrochemical supercapacitors.