Experimental characterization of elastocapillary and osmocapillary effects on multi-scale gel surface topography

Surface topography significantly affects various surface properties of polymer gels. Unlike conventional materials where surface topography is largely a geometric property, the surface topography of a polymer gel is governed by the competition between capillary, elastic, and osmotic effects, which leads to complex stimuli-responsive effects. Elastocapillary deformation and osmocapillary phase separation are two phenomena that are known to flatten gel surface topography. Here we experimentally quantify how osmocapillary phase separation affects gel surface topography by fabricating ionogels with multi-scale topography and characterizing the swelling-dependent surface flattening. Our observation confirms the vital role of the osmocapillary length in governing the surface behavior of swollen ionogels. This study provides the first quantitative experimental verification of the osmocapillary phase separation and shows the insufficiency of the previous studies based on elastocapillary deformation alone.

Polysaccharides, proteins, and synthetic polymers based multimodal hydrogels for various biomedical applications: A review

Nature-derived or biologically encouraged hydrogels have attracted considerable interest in numerous biomedical applications owing to their multidimensional utility and effectiveness. The internal architecture of a hydrogel network, the chemistry of the raw materials involved, interaction across the interface of counter ions, and the ability to mimic the extracellular matrix (ECM) govern the clinical efficacy of the designed hydrogels. This review focuses on the mechanistic viewpoint of different biologically driven/inspired biomacromolecules that encourages the architectural development of hydrogel networks. In addition, the advantage of hydrogels by mimicking the ECM and the significance of the raw material selection as an indicator of bioinertness is deeply elaborated in the review. Furthermore, the article reviews and describes the application of polysaccharides, proteins, and synthetic polymer-based multimodal hydrogels inspired by or derived from nature in different biomedical areas. The review discusses the challenges and opportunities in biomaterials along with future prospects in terms of their applications in biodevices or functional components for human health issues. This review provides information on the strategy and inspiration from nature that can be used to develop a link between multimodal hydrogels as the main frame and its utility in biomedical applications as the primary target.

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.

Investigation of biological effects of chitosan magnetic nano-composites hydrogel

The growing concern about microorganism infections, especially hospital-acquired infections, has driven the demand for effective and safe agents in recent years. Herein, novel nanocomposites were prepared based on layered double hydroxides (LDH NPs), Fe₂O₃nanoparticles (Fe₂O₃NPs), and chitosan hydrogel beads in different concentrations. The characteristics and composition of the prepared materials were investigated by various techniques such as XRD, FESEM, and FTIR. The results indicate that the nanocomposites are synthesized successfully, and each component is present in hydrogel matrixes. Then, their biomedical properties, including antibacterial, antifungal, and antioxidant activity, were examined. Our findings demonstrate that the antimicrobial activity of nanocomposites significantly depends on the concentration of each component and their chemical groups. It shows itself in the result of the inhibitory zone of all bacteria or fungi samples. The obtained results indicate that the nanocomposite of Chitosan-hydrogel beads with 20% LDH and Fe₂O₃(CHB-LDH-Fe₂O₃%20) and Chitosan-hydrogel beads based on 20% LDH (CHB-LDH%20) showed excellent antibacterial and antifungal properties against all tested bacteria and fungi (P ≤ 0.01). In addition, the antioxidant effects of the synthesized materials (especially CHB-LDH Fe₂O₃%20 and CHB-LDH%20) were investigated, showing high antioxidant efficacy against DPPH free radicals (P ≤ 0.01). According to our findings, we can say that these materials are promising biomaterials for inhibiting some infectious bacteria and fungi.

Interference of layered double hydroxide nanoparticles with pathways for biomedical applications

Recent decades have witnessed a surge of explorations into the application of multifarious materials, especially biomedical applications. Among them, layered double hydroxides (LDHs) have been widely developed as typical inorganic layer materials to achieve remarkable advancements. Multiple physicochemical properties endow LDHs with excellent merits in biomedical applications. Moreover, LDH nanoplatforms could serve as "molecular switches", which are capable of the controlled release of payloads under specific physiological pH conditions but are stable during circulation in the bloodstream. In addition, LDHs themselves are composed of several specific cations and possess favorable biological effects or regulatory roles in various cellular functions. These advantages have caused LDHs to become increasingly of interest in the area of nanomedicine. Recent efforts have been devoted to revealing the potential factors that interfere with the biological pathways of LDH-based nanoparticles, such as their applications in shaping the functions of immune cells and in determining the fate of stem cells and tumor treatments, which are comprehensively described herein. In addition, several intracellular signaling pathways interfering with by LDHs in the above applications were also systematically expatiated. Finally, the future development and challenges of LDH-based nanomedicine are discussed in the context of the ultimate goal of practical clinical application.

Nanoarchitectured two-dimensional layered double hydroxides-based nanocomposites for biomedical applications

Despite the exceptional physicochemical and morphological characteristics, the pristine layered double hydroxides (LDHs), or two-dimensional (2D) hydrotalcite clays, often suffer from various shortcomings in biomedicine, such as deprived thermal and chemical stabilities, acid-prone degradation, as well as lack of targeting ability, hampering their scale-up and subsequent clinical translation. Accordingly, diverse nanocomposites of LDHs have been fabricated by surface coating of organic species, impregnation of inorganic species, and generation of core-shell architectures, resulting in the complex state-of-the-art architectures. In this article, we initially emphasize various bothering limitations and the chemistry of these pristine LDHs, followed by discussions on the engineering strategies of different LDHs-based nanocomposites. Further, we give a detailed note on diverse LDH nanocomposites and their performance efficacy in various biomedical applications, such as drug delivery, bioimaging, biosensing, tissue engineering and cell patterning, deoxyribonucleic acid (DNA) extraction, as well as photoluminescence, highlighting the influence of various properties of installed supramolecular assemblies on their performance efficacy. In summary, we conclude with interesting perspectives concerning the lessons learned to date and the strategies to be followed to further advance their scale-up processing and applicability in medicine.

Electrical signals regulate the release of insulin from electrodeposited chitosan composite hydrogel: An in vitro and in vivo study

Electrical signal controlled drug release from polymeric drug delivery system provides an efficient way for accurate and demandable drug release. In this work, insulin was loaded on inorganic nanoplates (layered double hydroxides, LDHs) and coated on a copper wire by co-electrodeposition with chitosan. The formed structure in chitosan composite hydrogel entrapped insulin efficiently, which were proved by various techniques. In addition, the drug loaded chitosan composite hydrogel demonstrated good biocompatibility as suggested by cell attachment. In vitro drug release experiment showed fast responsive pulsed release of insulin by biasing electrical signals. The in vivo experiment in diabetic rats revealed controllable insulin release in plasma and stable decrease of blood glucose can be achieved by using appropriate electrical signal. In addition, HE staining suggested negligible effect to the tissue by electrical signals. This work suggests that the electrical signal controlled insulin release from chitosan composited hydrogel may be a promising administration route for insulin.

One-step programmable electrofabrication of chitosan asymmetric hydrogels with 3D shape deformation

Programmable asymmetric hydrogels with tunable structure/shape or physical/chemical properties in response to external stimuli show particular significance in smart systems, but there is lack of simple, rapid, and cheap strategy to design such hydrogel systems. Herein, we report a one-step electrodeposition method to construct chitosan asymmetric hydrogels with tunable thickness and pore size that can be conveniently modulated by the process parameters. Our approach greatly simplifies the process of hydrogel preparation with complex shapes and asymmetric structure organization. The formation mechanism of asymmetric structure has been proposed, based on gelation behavior and entanglement of chitosan chains in the hydrogel-solution system under the electric field. By changing the shape of the electrodes, hydrogels with the morphology of strip, tube, flower, etc. can be obtained precisely and conveniently. They can perform programmable 2D to 3D smart dynamic deformation under pH and metal ions stimulation, indicating the broad application potential in soft robot and biosensor areas.

Activation of the Catalytic Activity of Thrombin for Fibrin Formation by Ultrasound

The regulation of enzyme activity is a method to control biological function. We report two systems enabling the ultrasound-induced activation of thrombin, which is vital for secondary hemostasis. First, we designed polyaptamers, which can specifically bind to thrombin, inhibiting its catalytic activity. With ultrasound generating inertial cavitation and therapeutic medical focused ultrasound, the interactions between polyaptamer and enzyme are cleaved, restoring the activity to catalyze the conversion of fibrinogen into fibrin. Second, we used split aptamers conjugated to the surface of gold nanoparticles (AuNPs). In the presence of thrombin, these assemble into an aptamer tertiary structure, induce AuNP aggregation, and deactivate the enzyme. By ultrasonication, the AuNP aggregates reversibly disassemble releasing and activating the enzyme. We envision that this approach will be a blueprint to control the function of other proteins by mechanical stimuli in the sonogenetics field.

Electro-deposition synthesis of tube-like collagen-chitosan hydrogels and their biological performance

Electro-deposition is a smart, safe and efficient method for biomaterial manufacturing. Collagen, a functional protein with excellent biocompatibility and biosafety, is a promising candidate for tissue engineering and biomedical applications. However, there are few reports on electro-deposition of biomaterials using collagen without electrically or magnetically active nanoparticles. In this study, electro-deposition was employed to swiftly fabricate tube-like collagen-chitosan hydrogels in a mild environment. Fourier transform infrared spectroscopy was employed to analyze the ingredients of the tube-like hydrogels. The result showed that the hydrogels contained both collagen and chitosan. The distribution and content of collagen in the hydrogels was further measured by hematoxylin-eosin staining and hydroxyproline titration. Collagen was distributed homogeneously and its content was related to the initial collagen:chitosan ratio. The tension resistance of the composite gels and the thermal stability of collagen in the composites were obviously enhanced by the chitosan doping. Meanwhile, the tube-like hydrogels retained a good ability to promote cell proliferation of collagen. This method offers a convenient approach to the design and fabrication of collagen-based materials, which could effectively retain the bioactivity and biosafety of collagen and furnish a new way to enhance the stability of collagen and the tensile strength of collagen-based materials.

One-step electrochemically induced counterion exchange to construct free-standing carboxylated cellulose nanofiber/metal composite hydrogels

The fabrication of polymeric composite hydrogel with hierarchical structure in a simple, controllable, and straightforward process poses great importance for manufacturing nanomaterials and subsequent applications. Herein, we report a one-step and template-free counterion exchange method to construct free-standing carboxylated cellulose nanofiber composite hydrogels. Metal ions were electrochemically and locally released from the electrode and chelated with carboxylated cellulose nanofibers, leading to the in-situ formation of composite hydrogels. The properties of composite hydrogels can be easily programmed by the type of electrode, current density, and electrodeposited suspension. Significantly, the composited hydrogels exhibited interconnected nanoporous structure, enhanced thermal degradation, improved mechanical strength and antibacterial activity. The results suggest great potential of anodic electrodeposition to fabricate nanofiber/metal composite hydrogels.

Advanced drug delivery applications of layered double hydroxide

Layered double hydroxides (LDHs), also known as anionic clays or hydrotalcite-like compounds, are a class of nanomaterials that attained great attention as a carrier for drug delivery applications. The lamellar structure of this compound exhibits a high surface-to-volume ratio which enables the intercalation of therapeutic agents and releases them at the target site, thereby reducing the adverse effect. Moreover, the intercalated drug can be released in a sustained manner, and hence the frequency of drug administration can be decreased. The co-precipitation, ion exchange, manual grinding, and sol-gel methods are the most employed for their synthesis. The unique properties like the ease of synthesis, low cost, high biocompatibility, and low toxicity render them suitable for biomedical applications. This review presents the advances in the structure, properties, method of preparation, types, functionalization, and drug delivery applications of LDH. Also, this review provides various new conceptual insights that can form the basis for new research questions related to the drug delivery applications of LDH.

Synthesis of Graphene-Based Biopolymer TiO2 Electrodes Using Pyrolytic Direct Deposition Method and its Catalytic Performance

The traditional methods used to synthesize graphene layers over semiconductors are chemical-based methods. In the present investigation, a novel photoelectroactive electrode was synthesized using a chitosan biopolymer without the usage of chemicals. A chitosan-biopolymer layer over the surface of TiO2 was generated by electrodeposition. Furthermore, the pyrolysis method was used for the conversion of a biopolymer into graphene layers. The catalytic activity of the fabricated electrodes was investigated by the photo-electro-Fenton (PEF) process to oxidize chloramphenicol and nadolol pharmaceutical drugs in wastewater, remove metals (scandium, neodymium, and arsenic) and degrade real municipal wastewater. The PEF operational parameters (pH, voltage, reaction time, and Fenton catalytic dose) were optimized for the overall degradation of chloramphenicol and nadolol pharmaceutical drugs in wastewater. It was observed that at the optimum process operational parameters it took 40 min to degrade chloramphenicol and nadolol pharmaceutical drugs in wastewater. It was proved that biopolymer-based photoelectroactive novel electrodes render good catalytic activity. Furthermore, the reusability study of fabricated electrodes showed excellent storage and self-healing properties.

Electrodeposition of Polysaccharide and Protein Hydrogels for Biomedical Applications

In the last few decades, polysaccharide and protein hydrogels have attracted significant attentions and been applied in various engineering fields. Polysaccharide and protein hydrogels with appealing physical and biological features have been produced to meet different biomedical applications for their excellent properties related to biodegradability, biocompatibility, nontoxicity, and stimuli responsiveness. Numerous methods, such as chemical crosslinking, photo crosslinking, graft polymerization, hydrophobic interaction, polyelectrolyte complexation and electrodeposition have been employed to prepare polysaccharide and protein hydrogels. Electrodeposition is a facile way to produce different polysaccharide and protein hydrogels with the advantages of temporal and spatial controllability. This paper reviews the recent progress in the electrodeposition of different polysaccharide and protein hydrogels. The strategies of pH induced assembly, Ca2+ crosslinking, metal ions induced assembly, oxidation induced assembly derived from electrochemical methods were discussed. Pure, binary blend and ternary blend polysaccharide and protein hydrogels with multiple functionalities prepared by electrodeposition were summarized. In addition, we have reviewed the applications of these hydrogels in drug delivery, tissue engineering and wound dressing.

Influence of surface morphology and structure of alginate microparticles on the bioactive agents release behavior

The structure-property relationship in alginate microparticles (microspheres and microcapsules prepared with or without Trichoderma viride spores (Tv) was investigated. Surface morphology, structure and release behavior from alginate microparticles strongly depend on calcium concentration and presence of Tv and chitosan layer. All microparticles exhibited a granular surface structure with substructures consisting of abundant smaller particles. In vitro active agents release study revealed that the increase in calcium cation concentration reduced the release rate of Tv (˜84% for microspheres; ˜57% for microcapsules) and calcium cations (˜20% for microspheres; ˜23% for microcapsules). The average decrease in k values due to chitosan layer addition is 41% for Tv and 93% for calcium ions, respectively. The underlying Tv release mechanism from microspheres is anomalous transport kinetics, whereas from microcapsules is controlled by Type II transport. The differences in microparticle surface properties did not affect the mechanism controlling calcium ions release detected as diffusion through microparticles.

Electrofabrication of functional materials: Chloramine-based antimicrobial film for infectious wound treatment

Electrical signals can be imposed with exquisite spatiotemporal control and provide exciting opportunities to create structure and confer function. Here, we report the use of electrical signals to program the fabrication of a chloramine wound dressing with high antimicrobial activity. This method involves two electrofabrication steps: (i) a cathodic electrodeposition of an aminopolysaccharide chitosan triggered by a localized region of high pH; and (ii) an anodic chlorination of the deposited film in the presence of chloride. This electrofabrication process is completed within several minutes and the chlorinated chitosan can be peeled from the electrode to yield a free-standing film. The presence of active NCl species in this electrofabricated film was confirmed with chlorination occurring first on the amine groups and then on the amide groups when large anodic charges were used. Electrofabrication is quantitatively controllable as the cathodic input controls film growth during deposition and the anodic input controls film chlorination. In vitro studies demonstrate that the chlorinated chitosan film has antimicrobial activities that depend on the chlorination degree. In vivo studies with a MRSA infected wound healing model indicate that the chlorinated chitosan film inhibited bacterial growth, induced less inflammation, developed reorganized epithelial and dermis structures, and thus promoted wound healing compared to a bare wound or wound treated with unmodified chitosan. These results demonstrate the fabrication of advanced functional materials (i.e., antimicrobial wound dressings) using controllable electrical signals to both organize structure through non-covalent interactions (i.e., induce chitosan's reversible self-assembly) and to initiate function-conferring covalent modifications (i.e., generate chloramine bonds). Potentially, electrofabrication may provide a simple, low cost and sustainable alternative for materials fabrication.

STATEMENT OF SIGNIFICANCE

We believe this work is novel because this is the first report (to our knowledge) that electronic signals enable the fabrication of advanced antimicrobial dressings with controlled structure and biological performance. We believe this work is significant because electrofabrication enables rapid, controllable and sustainable materials construction with reduced adverse environmental impacts while generating high performance materials for healthcare applications. More specifically, we report an electrofbrication of antimicrobial film that can promote wound healing.

Electrodeposition of reduced graphene oxide with chitosan based on the coordination deposition method

The electrodeposition of graphene has drawn considerable attention due to its appealing applications for sensors, supercapacitors and lithium-ion batteries. However, there are still some limitations in the current electrodeposition methods for graphene. Here, we present a novel electrodeposition method for the direct deposition of reduced graphene oxide (rGO) with chitosan. In this method, a 2-hydroxypropyltrimethylammonium chloride-based chitosan-modified rGO material was prepared. This material disperses homogenously in the chitosan solution, forming a deposition solution with good dispersion stability. Subsequently, the modified rGO material was deposited on an electrode through codeposition with chitosan, based on the coordination deposition method. After electrodeposition, the homogeneous, deposited rGO/chitosan films can be generated on copper or silver electrodes or substrates. The electrodeposition method allows for the convenient and controlled creation of rGO/chitosan nanocomposite coatings and films of different shapes and thickness. It also introduces a new method of creating films, as they can be peeled completely from the electrodes. Moreover, this method allows for a rGO/chitosan film to be deposited directly onto an electrode, which can then be used for electrochemical detection.

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 chitosan/gelatin coatings with controlled porous surface topography to enhance initial osteoblast adhesive responses

Electrophoretically deposited (EPD) coatings have often been employed recently for the addition of different new chemical compositions to classic chitosan coatings to improve the biocompatibility and therapeutic potential of coated implants. However, little attention has been paid to enhance the cell response to EPD coatings via integrating the effects of chemical components and surface topography. Here, we fabricated EPD chitosan/gelatin (CS/G) coatings with controlled porous surface topography by controlling bubble generation in the EPD process via changing the gelatin content in solution from 0, 0.01, 0.1, and 1 to 10 mg ml^-1. The pure chitosan coating surface was characterized by homogeneous large pores of 500 μm. After 0.01 mg ml^-1 gelatin was added, 180 μm small pores appeared on the walls of large pores. As the gelatin content increased to 0.1 mg ml^-1, a number of small pores increased noticeably. When the gelatin content reached 1 mg ml^-1, large pores disappeared, and the coating displayed homogeneous small pores. 10 mg ml^-1 gelatin concentration led to coatings consisting of small pores with not integral and continuous structures. The initial osteoblastic responses, including cell adherence progress, spreading area, proliferation rate, and focal adhesion-related gene expression, gradually improved from 0 to 0.01, 0.1, and 1 mg ml^-1 gelatin content, but decreased from 1 to 10 mg ml^-1. All these results indicated that the initial cell responses to coatings reached a peak when it was 1 mg ml^-1 gelatin and they had homogeneous small pores, which might contribute to the synergistic effects of the porous surface structure and components. This work would be beneficial for expanding the potential application of EPD coatings.

Stimuli-Responsive Delivery of Therapeutics for Diabetes Treatment

Diabetic therapeutics, including insulin and glucagon-like peptide 1 (GLP-1), are essential for diabetic patients to regulate blood glucose levels. However, conventional treatments that are based on subcutaneous injections are often associated with poor glucose control and a lack of patient compliance. In this review, we focus on the different stimuli-responsive systems to deliver therapeutics for diabetes treatment to improve patient comfort and prevent complications. Specifically, the pH-responsive systems for oral drug delivery are introduced first. Then, the closed-loop glucose-responsive systems are summarized based on different glucose-responsive moieties, including glucose oxidase (GOx), glucose binding protein (GBP), and phenylboronic acid (PBA). Finally, the on-demand delivery systems activated by external remote triggers are also discussed. We conclude by discussing advantages and limitations of current strategies, as well as future opportunities and challenges in this area.

Multilayered drug delivery coatings composed of daidzein-loaded PHBV microspheres embedded in a biodegradable polymer matrix by electrophoretic deposition

Drug encapsulation with predetermined loading, and the fabrication of multilayered drug delivery coatings by a combination of EPD and LbL deposition.