Chitosan-mediated and spatially selective electrodeposition of nanoscale particles

Programmable Physical Properties of Freestanding Chitosan Membranes Electrofabricated in Microfluidics

Microfluidic-integrated freestanding membranes with suitable biocompatibility and tunable physicochemical properties are in high demand for a wide range of life science and biological studies. However, there is a lack of facile and rapid methods to integrate such versatile membranes into microfluidics. A recently invented interfacial electrofabrication of chitosan membranes offers an in-situ membrane integration strategy that is flexible, controllable, simple, and biologically friendly. In this follow-up study, we explored the ability to program the physical properties of these chitosan membranes by varying the electrofabrication conditions (e.g., applied voltage and pH of alginate). We found a strong association between membrane growth rate, properties, and fabrication parameters: high electrical stimuli and pH of alginate resulted in high optical retardance and low permeability, and vice versa. This suggests that the molecular alignment and density of electrofabricated chitosan membranes could be actively tailored according to application needs. Lastly, we demonstrated that this interfacial electrofabrication could easily be expanded to produce chitosan membrane arrays with higher uniformity than the previously well-established flow assembly method. This study demonstrates the tunability of the electrofabricated membranes' properties and functionality, thus expanding the utility of such membranes for broader applications in the future.

Electrochemically deposition of catechol-chitosan hydrogel coating on coronary stent with robust copper ions immobilization capability and improved interfacial biological activity

Establishing a facile and versatile strategy to confer coronary stent with improved interfacial biological activity is crucial for novel cardiovascular implants. Developing a coating with NO release ability catalyzed by metal ions, such as copper, will be highly advantageous for the functionalized surface modification of metal stents. However, most available strategies involve drawbacks of low efficiency, complex processes, and toxic chemicals. Therefore, in this study, we report a green and facile electrobiofabrication method to construct the bioactive hydrogel coating by combining chitosan, catechol groups and copper ions on coronary stent and titanium surfaces. Experimental results demonstrated that the chitosan hydrogel coating can be precisely controlled synthesis via electrochemical deposition and serves as a versatile platform for copper ions immobilization. Additionally, mussel-inspired catechol groups could be chemically grafted on chitosan chains to further enhance the film mechanical properties and binding abilities of copper ions. Moreover, in vitro cell biocompatibility and catalyzed NO-generation activity have also been accessed and which suggesting great possibilities for biomedical applications. Therefore, by coupling the electrobiofabrication approach and multi-functionalities of the hybrid film, this report would advance the development of biomimetic hydrogel coating for vascular engineering (e.g., coronary stent) and other biomedical devices.

Surface functionalization of chitosan as a coating material for orthopaedic applications: A comprehensive review

Metallic implants have dominated the biomedical implant industries for the past century for load-bearing applications, while the polymeric implants have shown great promise for tissue engineering applications. The surface properties of such implants are critical as the interaction of implant surfaces, and the body tissues may lead to unfavourable reactions. Desired implant properties are biocompatibility, corrosion resistance, and antibacterial activity. A polymer coating is an efficient and economical way to produce such surfaces. A lot of research has been carried out on chitosan (CS)-modified metallic and polymer scaffolds in the last decade. Different methods such as electrophoretic deposition, sol-gel methods, dip coating and spin coating, electrospinning, etc. have been utilized to produce CS coatings. However, a systematic review of chitosan coatings on scaffolds focussing on widely employed techniques is lacking. This review surveys literature concerning the current status of orthopaedic applications of CS for the purpose of coatings. In this review, the various preparation methods of coating, and the role of the surface functionalities in determining the efficiency of coatings are discussed. Effect of nanoparticle additions on the polymeric interfaces and in regulating the properties of surface coatings are also investigated in detail.

Wire templated electrodeposition of vessel-like structured chitosan hydrogel by using a pulsed electrical signal

Herein, by performing a templated electrodeposition process with an oscillating electrical signal stimulation, a vessel-like structured chitosan hydrogel (diameter about 0.4 mm) was successfully prepared in the absence of salt conditions. Experimental results demonstrated that the hydrogel growth (e.g. the thickness) is linearly correlated with the imposed charge transfer and can be well quantified by using a theoretical moving front model. Morphological observations indicated that the heterogeneous multilayer structure was spatially and temporally controlled by an externally employed electrical signal sequence while the channel structure could be determined by the shaped electrode. Moreover, the oscillating ON-OFF cycles were proved to strongly affect the film structure, leading to a more compact hydrogel coating with a lower water content, higher crystallinity, complex layer architecture and relatively strong mechanical properties that could be easily peeled off as a free-standing hollow tube. Importantly, all the experiments were conducted under mild conditions that allowed additional enhancing materials to be added in to further improve the mechanical and/or biological properties. Thus, this work advances a very promising self-assembly technology for the construction of a multi-functional hydrogel coating and artificial blood vessel regeneration.

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.

Electrobiofabrication: electrically based fabrication with biologically derived materials

While conventional material fabrication methods focus on form and strength to achieve function, the fabrication of material systems for emerging life science applications will need to satisfy a more subtle set of requirements. A common goal for biofabrication is to recapitulate complex biological contexts (e.g. tissue) for applications that range from animal-on-a-chip to regenerative medicine. In these cases, the material systems will need to: (i) present appropriate surface functionalities over a hierarchy of length scales (e.g. molecular features that enable cell adhesion and topographical features that guide differentiation); (ii) provide a suite of mechanobiological cues that promote the emergence of native-like tissue form and function; and (iii) organize structure to control cellular ingress and molecular transport, to enable the development of an interconnected cellular community that is engaged in cell signaling. And these requirements are not likely to be static but will vary over time and space, which will require capabilities of the material systems to dynamically respond, adapt, heal and reconfigure. Here, we review recent advances in the use of electrically based fabrication methods to build material systems from biological macromolecules (e.g. chitosan, alginate, collagen and silk). Electrical signals are especially convenient for fabrication because they can be controllably imposed to promote the electrophoresis, alignment, self-assembly and functionalization of macromolecules to generate hierarchically organized material systems. Importantly, this electrically based fabrication with biologically derived materials (i.e. electrobiofabrication) is complementary to existing methods (photolithographic and printing), and enables access to the biotechnology toolbox (e.g. enzymatic-assembly and protein engineering, and gene expression) to offer exquisite control of structure and function. We envision that electrobiofabrication will emerge as an important platform technology for organizing soft matter into dynamic material systems that mimic biology's complexity of structure and versatility of function.

Hydrogel electrodeposition based on bipolar electrochemistry

Bipolar electrochemistry has attracted great interest for applications based on sensing, electrografting, and electrodeposition, because the technique enables electrochemical reactions to be induced at multiple bipolar electrodes (BPEs) with only a single power supply. However, there are only a few reports on the biofabrication of hydrogels using BPEs. In this study, we applied bipolar electrochemistry to achieve the electrodeposition of calcium-alginate hydrogels at specified target areas, which is possible because of the use of water electrolysis to obtain acidification at the anodic pole. This scheme was used to successfully fabricate an array of hydrogel deposits at a BPE array. In addition, hydrogels were successfully fabricated either at only the target BPEs or only the target areas of BPEs by repositioning the driving electrodes. Furthermore, a hydrogel was drawn on a large BPE as a canvas by using small driving electrodes. As a demonstration of the electrodeposited hydrogels for bioapplications, mammal cells were cultured in the hydrogels. Because the amount and shape of the hydrogel deposits can be controlled by using the bipolar system, the system we developed can be used for biosensors and cell culture platforms.

Connecting Biology to Electronics: Molecular Communication via Redox Modality

Biology and electronics are both expert at for accessing, analyzing, and responding to information. Biology uses ions, small molecules, and macromolecules to receive, analyze, store, and transmit information, whereas electronic devices receive input in the form of electromagnetic radiation, process the information using electrons, and then transmit output as electromagnetic waves. Generating the capabilities to connect biology-electronic modalities offers exciting opportunities to shape the future of biosensors, point-of-care medicine, and wearable/implantable devices. Redox reactions offer unique opportunities for bio-device communication that spans the molecular modalities of biology and electrical modality of devices. Here, an approach to search for redox information through an interactive electrochemical probing that is analogous to sonar is adopted. The capabilities of this approach to access global chemical information as well as information of specific redox-active chemical entities are illustrated using recent examples. An example of the use of synthetic biology to recognize external molecular information, process this information through intracellular signal transduction pathways, and generate output responses that can be detected by electrical modalities is also provided. Finally, exciting results in the use of redox reactions to actuate biology are provided to illustrate that synthetic biology offers the potential to guide biological response through electrical cues.

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.

Label-free immunosensor based on one-step electrodeposition of chitosan-gold nanoparticles biocompatible film on Au microelectrode for determination of aflatoxin B1 in maize

Gold nanoparticles (AuNPs) embedded in chitosan (CHI) film, well-dispersed and smaller in size (about 10 nm), were fabricated by one-step electrodeposion on Au microelectrode in solution containing chitosan and chloride trihydrate. The nano-structure CHI-AuNPs composite film offers abundant amine groups, good conductivity, excellent biocompatibility and stability for antibody immobilization. The combination of aflatoxin B1 (AFB1) with immobilized antibody introduces a barrier to electron transfer, resulting in current decreasement. The morphologies and characterizations of modified microelectrodes were investigated by scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR). The proposed non-enzyme and label-free immunosensor exhibited high sensitive amperometric response to AFB1 concentration in two linear ranges of 0.1 to 1 ng mL(-1) and 1 to 30 ng mL(-1), with the detection limit of 0.06 ng mL(-1) (S/N=3). The immunoassay was also applied for analysis of maize samples spiked with AFB1. Considering the sample extraction procedure, the linear range and limit of detection were assessed to be 1.6-16 ng mL(-1) and 0.19 ng mL(-1) respectively. The simple method showed good fabrication controllability and reproducibility for immunosensor design.

An electrodeposited graphite oxide/cobalt hydroxide/chitosan ternary composite on nickel foam as a cathode material for hybrid supercapacitors

In this paper, we report the development of a graphite oxide (GO)/cobalt hydroxide (Co(OH)₂)/chitosan composite to be used as a cathode material for hybrid supercapacitors.

Self-assembly with orthogonal-imposed stimuli to impart structure and confer magnetic function to electrodeposited hydrogels

A magnetic nanocomposite film with the capability of reversibly collecting functionalized magnetic particles was fabricated by simultaneously imposing two orthogonal stimuli (electrical and magnetic). We demonstrate that cathodic codeposition of chitosan and Fe3O4 nanoparticles while simultaneously applying a magnetic field during codeposition can (i) organize structure, (ii) confer magnetic properties, and (iii) yield magnetic films that can perform reversible collection/assembly functions. The magnetic field triggered the self-assembly of Fe3O4 nanoparticles into hierarchical "chains" and "fibers" in the chitosan film. For controlled magnetic properties, the Fe3O4-chitosan film was electrodeposited in the presence of various strength magnetic fields and different deposition times. The magnetic properties of the resulting films should enable broad applications in complex devices. As a proof of concept, we demonstrate the reversible capture and release of green fluorescent protein (EGFP)-conjugated magnetic microparticles by the magnetic chitosan film. Moreover, antibody-functionalized magnetic microparticles were applied to capture cells from a sample, and these cells were collected, analyzed, and released by the magnetic chitosan film, paving the way for applications such as reusable biosensor interfaces (e.g., for pathogen detection). To our knowledge, this is the first report to apply a magnetic field during the electrodeposition of a hydrogel to generate magnetic soft matter. Importantly, the simple, rapid, and reagentless fabrication methodologies demonstrated here are valuable features for creating a magnetic device interface.

Electrochemical deposition to construct a nature inspired multilayer chitosan/layered double hydroxides hybrid gel for stimuli responsive release of protein

A single electrodeposition process to fabricate multilayered chitosan/layered double hydroxides (LDHs) hybrid hydrogel for stimuli responsive protein release.

Biofunctionalization of titanium implant with chitosan/siRNA complex through loading-controllable and time-saving cathodic electrodeposition

For the first time, siRNA has been cathodically electrodeposited on a titanium surface for efficient target gene silencing.

Conductive carbon nanotube hydrogel as a bioanode for enhanced microbial electrocatalysis

Enhancing microbial electrocatalysis through new material design is essential to the efficient and stable operation of bio-electrochemical system (BES). In this work, a novel conductive carbon nanotube (CNT) hydrogel was fabricated by electrodepositing both CNT and chitosan onto a carbon paper electrode and used as a BES anode electrode. The microscopic, spectroscopic, and electrochemical analytical results show that the CNT hydrogel exhibited an excellent electrochemical activity. In the BES tests, the current generation and the maximum power density of the MFC with the CNT hydrogel increased by 23% and 65%, respectively, compared with the control. This demonstrates that the utilization of such a hydrogel offers an effective approach to enhance the current generation of BES. The great conductivity of CNT and the high content of oxygen-containing functional groups (C-OH, C═O, etc.) on their surface were found to be responsible for the improvements. Our work provides a facile way to prepare appropriate BES electrodes and offers a straightforward and effective route to enhance the BES performance.

Label-free electrochemiluminescence detection of specific-sequence DNA based on DNA probes capped ion nanochannels

A label-free electrochemiluminescence method for detecting specific-sequence DNA has been developed based on DNA probes capped ion nanochannels. This method is simple, inexpensive, and can be potentially expanded for the design of different types of ECL aptasensors.

ZnO/Cu nanocomposite: a platform for direct electrochemistry of enzymes and biosensing applications

Unique structured nanomaterials can facilitate the direct electron transfer between redox proteins and the electrodes. Here, in situ directed growth on an electrode of a ZnO/Cu nanocomposite was prepared by a simple corrosion approach, which enables robust mechanical adhesion and electrical contact between the nanostructured ZnO and the electrodes. This is great help to realize the direct electron transfer between the electrode surface and the redox protein. SEM images demonstrate that the morphology of the ZnO/Cu nanocomposite has a large specific surface area, which is favorable to immobilize the biomolecules and construct biosensors. Using glucose oxidase (GOx) as a model, this ZnO/Cu nanocomposite is employed for immobilization of GOx and the construction of the glucose biosensor. Direct electron transfer of GOx is achieved at ZnO/Cu nanocomposite with a high heterogeneous electron transfer rate constant of 0.67 ± 0.06 s(-1). Such ZnO/Cu nanocomposite provides a good matrix for direct electrochemistry of enzymes and mediator-free enzymatic biosensors.

pH- and voltage-responsive chitosan hydrogel through covalent cross-linking with catechol

A new method for covalently cross-linking chitosan is developed by chemically oxidizing catechol to o-quinone which subsequently reacts with and cross-links chitosan through Michael addition and Schiff base formation. The cross-linked chitosan film shows a pH-responsive, switchlike behavior toward the negatively charged redox probe, Fe(CN)(6)(3-/4-), and withstands harsh acidic conditions. The negative Fe(CN)(6)(3-/4-) is found to be trapped and enriched in the catechol-cross-linked chitosan film under acidic conditions and released into solution by either increasing pH or applying a negative voltage. Chitosan films made with different techniques, i.e., solvent evaporation (simple deposition), electrodeposition, and covalent cross-linking, are examined using cyclic voltammetry and electrochemical impedance spectroscopy (EIS), and the results demonstrate that fabrication methods greatly affect the properties of the chitosan films.

Chitosan nanoparticles: a promising system in novel drug delivery

The ability of nanoparticles to manipulate the molecules and their structures has revolutionized the conventional drug delivery system. The chitosan nanoparticles, because of their biodegradability, biocompatibility, better stability, low toxicity, simple and mild preparation methods, offer a valuable tool to novel drug delivery systems in the present scenario. Besides ionotropic gelation method, other methods such as microemulsion method, emulsification solvent diffusion method, polyelectrolyte complex method, emulsification cross-linking method, complex coacervation method and solvent evaporation method are also in use. The chitosan nanoparticles have also been reported to have key applications in parentral drug delivery, per-oral administration of drugs, in non-viral gene delivery, in vaccine delivery, in ocular drug delivery, in electrodeposition, in brain targeting drug delivery, in stability improvement, in mucosal drug delivery in controlled drug delivery of drugs, in tissue engineering and in the effective delivery of insulin. The present review describes origin and properties of chitosan and its nanoparticles along with the different methods of its preparation and the various areas of novel drug delivery where it has got its application.

Hybrid antimicrobial enzyme and silver nanoparticle coatings for medical instruments

We report a method for the synthesis of antimicrobial coatings on medical instruments that combines the bacteriolytic activity of lysozyme and the biocidal properties of silver nanoparticles. Colloidal suspensions of lysozyme and silver nanoparticles were electrophoretically deposited onto the surface of stainless steel surgical blades and needles. Electrodeposited films firmly adhered to stainless steel surfaces even after extensive washing and retained the hydrolytic properties of lysozyme. The antimicrobial efficacy of coatings was tested by using blades and needles in an in vitro lytic assay designed to mimic the normal application of the instruments. Coated blades and needles were used to make incisions and punctures, respectively, into agarose infused with bacterial cells. Cell lysis was seen at the contact sites, demonstrating that antimicrobial activity is transferred into the media, as well as retained on the surface of the blades and needles. Blade coatings also exhibited antimicrobial activity against a range of bacterial species. In particular, coated blades demonstrated potent bactericidal activity, reducing cell viability by at least 3 log within 1.5 h for Klebsiella pneumoniae, Bacillus anthracis Sterne, and Bacillus subtilis and within 3 h for Staphylococcus aureus and Acinetobacter baylyi. The results confirmed that complex antimicrobial coatings can be created using facile methods for silver nanoparticle synthesis and electrodeposition.

A simple strategy for one-step construction of bienzyme biosensor by in-situ formation of biocomposite film through electrodeposition

One-step construction of horseradish peroxidase (HRP) and glucose oxidase (GOD) bienzyme biosensor was established based on a simple and controllable electrodeposition approach by in-situ formation of biocomposite film on electrode. With hydrogen peroxide (H(2)O(2)) instantly generated by GOD-catalyzed oxidation of glucose, quantitative measurement of glucose could be achieved. In the proposed electrodeposition strategy, Concanavalin A (Con A) was applied as bifunctional cross-linker for in-situ incorporating of HRP-GOD in biocompatible chitosan (CS) matrix due to its biospecific affinity interaction with CS and glycoproteins. Scanning electron microscopy showed that the HRP-GOD/Con A/CS biocomposite film possessed highly porous surface. The developed bienzyme biosensor exhibited a fast amperometric response for the determination of glucose. The linear response of the developed biosensor for the determination of glucose ranged from 1.0x10(-6) to 2.2x10(-4) M with a detection limit of 6.7x10(-7) M. The biosensor can be used to determine glucose in serum directly. The biosensor presented high stability owing to the design of the introduction of Con A and instant generation of H(2)O(2) with bienzyme system. The one-step construction of biosensor based on non-manual technique in biocompatible environment was direct and facile.