An amperometric biosensor fabricated from electro-co-deposition of sodium alginate and horseradish peroxidase

Electrophoretic Deposition of Hybrid Calcium Alginate-Gold Nanoparticle Hydrogel Films via Catalyzed Electrooxidation of Hydroquinone

The electrophoretic deposition (EPD) of hybrid alginate (Alg)-Au nanoparticle (NP) films results from the localized pH drop at the electrode surface due to oxidation of hydroquinone (HQ) catalyzed by 4 and 15 nm diameter citrate-coated gold NPs (cit-Au NPs). The localized pH drop at the electrode leads to neutralization of both Alg and cit, leading to EPD of both Alg and cit-Au NPs simultaneously. Post-treatment of the film with Ca²⁺ solution leads to hybrid Ca-Alg-Au NP hydrogel films. The EPD of Alg in the presence of 4 nm cit-Au NPs occurs at ∼0.8 V (vs Ag/AgCl) as compared to ∼1.0 V in the presence of 15 nm cit-Au NPs and ∼1.4 V in the absence of cit-Au NPs. This is due to the higher catalytic activity of 4 nm cit-Au NPs compared to 15 nm cit-Au NPs for the oxidation of HQ. UV-vis spectra of Ca-Alg-Au NP hydrogel films show absorbance features for both Ca-Alg and Au NPs entrapped within the hydrogel. As the concentration of Au NPs in the EPD solution increases, the Ca-Alg absorbance and localized surface plasmon resonance (LSPR) peak of the Au NPs increases, confirming the role of the Au NPs as a catalyst for EPD of Alg. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the Ca-Alg-Au NP hydrogel films show characteristic peaks for Ca-Alg and protonated alginic acid groups. The hydrogel thickness is greater with cit-Au NPs compared to without cit-Au NPs at constant EPD potential and time. Forming Ca-Alg and hybrid Ca-Alg-Au NP hydrogel films at low potentials has potential applications in electrochemical and optical sensor development, catalysis, and biological studies.

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.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Electrophoretic deposition of biomaterials

Electrophoretic deposition (EPD) is attracting increasing attention as an effective technique for the processing of biomaterials, specifically bioactive coatings and biomedical nanostructures. The well-known advantages of EPD for the production of a wide range of microstructures and nanostructures as well as unique and complex material combinations are being exploited, starting from well-dispersed suspensions of biomaterials in particulate form (microsized and nanoscale particles, nanotubes, nanoplatelets). EPD of biological entities such as enzymes, bacteria and cells is also being investigated. The review presents a comprehensive summary and discussion of relevant recent work on EPD describing the specific application of the technique in the processing of several biomaterials, focusing on (i) conventional bioactive (inorganic) coatings, e.g. hydroxyapatite or bioactive glass coatings on orthopaedic implants, and (ii) biomedical nanostructures, including biopolymer-ceramic nanocomposites, carbon nanotube coatings, tissue engineering scaffolds, deposition of proteins and other biological entities for sensors and advanced functional coatings. It is the intention to inform the reader on how EPD has become an important tool in advanced biomaterials processing, as a convenient alternative to conventional methods, and to present the potential of the technique to manipulate and control the deposition of a range of nanomaterials of interest in the biomedical and biotechnology fields.