Electrical behavior of polymer hydrogel composed of poly(vinyl alcohol)-hyaluronic acid in solution

Current Understanding of Hydrogel for Drug Release and Tissue Engineering

Due to their good absorption, satisfactory biocompatibility, and high safety, hydrogels have been widely used in the field of biomedicine, including for drug delivery and tissue regeneration. In this review, we introduce the characteristics and crosslinking methods of natural and synthetic hydrogels. Then, we highlight the design and principle of intelligent hydrogels (i.e., responsive hydrogels) used for drug release. Moreover, we introduce the application of the application of hydrogels in drug release and tissue engineering, and the limitations and research directions of hydrogel in drug release and tissue engineering are also considered. We hope that this review can provide a reference for follow-up studies in related fields.

Electromechanical response performance of a reinforced biomass gel artificial muscle based on natural polysaccharide of sodium alginate doped with an ionic liquid for micro-nano regulation

In this paper, a reinforced Biomass Gel Artificial Muscle (BGAM) was fabricated by natural polysaccharide of Sodium Alginate (SA) doped with an Ionic Liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm][BF₄]). Micro-nano regulation effect and reinforcement mechanism of IL doping content on electromechanical response performance of BGAM were researched during a single cycle and repeated cycles. Then, a green fabrication process and a set of valid test methods for BGAM were proposed in detail. The experimental results showed that when IL doping content was 4 mL, the BGAM achieved optimal modification, with a porosity of 70.47%, where it internally adopted the porous polymer structure of ion channels. Additionally, specific capacitance of BGAM attained a maximum value of 126.98 mF/g, and the inner resistance and elastic modulus reached minimum values of 2.018 Ω and 1.871 MPa, separately. Thus, the optimal working life and output-force density values, namely, 1720 s and 13.072 mN/g, respectively, were also determined for the BGAM.

Polymer-Based Electrophoretic Deposition of Nonwovens for Medical Applications: The Effect of Carrier Structure, Solution, and Process Parameters

Hyaluronate and alginate are non-toxic and biocompatible polymers, which can be used for surface modification and functionalization of many kinds of materials. Electrophoretic deposition (EPD) has several advantages, including its versatility, simplicity, and ability to coat substrates with complex shapes, and is used for the creation of antimicrobial or hydrophobic coatings on metallic biomaterials, among other applications. However, its utilization for applying biopolymer layers on textiles is very limited due to the more complex structure and spatial characteristics of fibrous materials. The aim of this research was to analyze the effects of selected EPD process parameters and the structural characteristics of fibrous carriers on the kinetics of the process and the microscopic characteristics of the deposited layers. The influence of solution characteristics, process parameters, and carrier structures obtained using two different techniques (melt blown and spun-bonded) were analyzed. The morphology and structure of the created deposits were analyzed using scanning electron microscopy and computed tomography, and molecular structure analysis was performed with Fourier Transform Infrared spectroscopy. The surface mass and thickness of fibrous poly (lactic acid)-based carriers were analyzed in accordance with the respective standards. This study serves as a basis for discussion and further development of this method with regard to fibrous materials for medical applications.

Environmentally responsive hydrogels for repair of cardiovascular tissue

Cardiovascular diseases (CVDs) pose a serious threat to human health, which are characterized by high disability and mortality rate globally such as myocardial infarction (MI), atherosclerosis, and heart failure. Although stem cells transplantation and growth factors therapy are promising, their low survival rate and loss at the site of injury are major obstacles to this therapy. Recently, the development of hydrogel scaffold materials provides a new way to solve this problem, which have shown the potential to treat CVD. Among these scaffold materials, environmentally responsive hydrogels have great prospects in repairing the microenvironment of cardiovascular tissues and vascular regeneration. They provide a new method for the treatment of cardiovascular tissue repair and space-time control for the release of various therapeutic drugs, including small-molecule drugs, growth factors, and stem cells. Herein, this article reviews the occurrence and current treatment of CVD, as well as the repair of cardiovascular injury by several environmental responsive hydrogels systems currently used, mainly focusing on the delivery of growth factors or the application of cell therapy to revascularization. In addition, we will also discuss the enormous potential and personal perspectives of environmentally responsive hydrogels in cardiovascular repair.

Biomaterials for drug delivery patches

The limited efficiency of conventional drugs has been instigated the development of new and more effective drug delivery systems (DDS). Transdermal DDS, are associated with numerous advantages such its painless application and less frequent replacement and greater flexibility of dosing, features that triggered the research and development of such devices. Such systems have been produced using either biopolymer; or synthetic polymers. Although the first ones are safer, biocompatible and present a controlled degradation by human enzymes or water, the second ones are the most currently available in the market due to their greater mechanical resistance and flexibility, and non-degradation over time. This review highlights the most recent advances (mainly in the last five years) of patches aimed for transdermal drug delivery, focusing on the different materials (natural, synthetic and blends) and latest designs for the development of such devices, emphasizing also their combination with drug carriers that enable enhanced drug solubility and a more controlled release of the drug over the time. The benefits and limitations of different patches formulations are considered with reference to their appliance to transdermal drug delivery. Furthermore, a record of the currently available patches on the market is given, featuring their most relevant characteristics. Finally, a list of most recent/ongoing clinical trials regarding the use of patches for skin disorders is detailed and critical insights on the current state of patches for transdermal drug delivery are also provided.

Smart Polymeric Hydrogels for Cartilage Tissue Engineering: A Review on the Chemistry and Biological Functions

Stimuli responsive hydrogels (SRHs) are attractive bioscaffolds for tissue engineering. The structural similarity of SRHs to the extracellular matrix (ECM) of many tissues offers great advantages for a minimally invasive tissue repair. Among various potential applications of SRHs, cartilage regeneration has attracted significant attention. The repair of cartilage damage is challenging in orthopedics owing to its low repair capacity. Recent advances include development of injectable hydrogels to minimize invasive surgery with nanostructured features and rapid stimuli-responsive characteristics. Nanostructured SRHs with more structural similarity to natural ECM up-regulate cell-material interactions for faster tissue repair and more controlled stimuli-response to environmental changes. This review highlights most recent advances in the development of nanostructured or smart hydrogels for cartilage tissue engineering. Different types of stimuli-responsive hydrogels are introduced and their fabrication processes through physicochemical procedures are reported. The applications and characteristics of natural and synthetic polymers used in SRHs are also reviewed with an outline on clinical considerations and challenges.

Surface modification of the conducting polymer, polypyrrole, via affinity peptide

A novel strategy for affinity-based surface modification of the conducting polymer, polypyrrole, (PPy), has been developed. A 12-amino acid peptide (THRTSTLDYFVI, hereafter denoted T59) was previously identified via the phage display technique. This peptide noncovalently binds to the chlorine-doped conducting polymer polypyrrole (PPyCl). Studies have previously shown that conductive polymers have promising application in neural electrodes, sensors, and for improving regeneration and healing of peripheral nerves and other tissues. Thus, the strong and specific attachment of bioactive molecules to the surface of PPy using the T59 affinity peptide is an exciting new approach to enhance the bioactivity of electrically active materials for various biomedical applications. We demonstrate this by using T59 as a tether to modify PPyCl with the laminin fragment IKVAV to enhance cell interactions, as well as with the so-called stealth molecule poly(ethylene glycol; PEG) to decrease cell interactions. Using these two modification strategies, we were able to control cell attachment and neurite extension on the PPy surface, which is critical for different applications (i.e., the goal for tissue regeneration is to enhance cell interactions, whereas the goal for electrode and sensor applications is to reduce glial cell interactions and thus decrease scarring). Significantly, the conductivity of the PPyCl surface was unaffected by this surface modification technique, which is not the case with other methods that have been explored to surface modify conducting polymers. Finally, using subcutaneous implants, we confirmed that the PPyCl treated with the T59 peptide did not react in vivo differently than untreated PPyCl.

Multipurpose smart hydrogel systems

This paper represents the review of the last investigations in the field of smart polymeric hydrogels and our contribution to this matter. New hydrogel systems and nanocomposites based on acrylic monomers (acrylamide, acrylonitrile, acrylic acid, N-isopropylacrylamide etc.) with incorporated nanosized colloidal silver, hydroxyapatite and carbon nanotubes with a new set of properties have been obtained and examined. These systems can sharply change their characteristics when minor external physical (electric and magnetic fields, temperature etc.) or chemical (pH, ionic strength) stimuli are applied. Such stimulus-responsive polymeric systems are very promising from the standpoint of different medical applications, especially for the development of intelligent drug delivery systems. On the base of designed hydrogel iontophoretic transdermal therapeutic systems, endoprosthesis for the replacement of bone tissue and hydrogel burns coatings with immobilized mesenchymal cells were obtained and tested.

Regulation of the matrix microenvironment for stem cell engineering and regenerative medicine

The extracellular matrix (ECM) microenvironment consists of structural and functional molecules. The ECM relays both biochemical and biophysical cues to and from the cells to modulate cell behavior and function. The biophysical cues can be engineered and applied to cells by means of spatial patterning, matrix rigidity, and matrix actuation. Tissue engineering strategies that utilize ECMs to direct stem cell organization and lineage specification show tremendous potential. This review describes the technologies for modulating ECM spatial patterning, matrix rigidity, chemical composition, and matrix actuation. The role of ECMs in vascular tissue engineering is then discussed as a model of tissue engineering and regenerative medicine.

Biocompatibility Evaluation of Chitosan-based Injectable Hydrogels for the Culturing Mice Mesenchymal Stem Cells In Vitro

A thermosensitive polymer can be held liquid before being injected to deliver living cells or therapeutic agents and formed monolithic gels when injected in vivo. In this study, chitosan-based thermosensitive hydrogels were prepared, characterized and the biocompatibility for culturing mice bone mesenchymal stem cells (BMSC) on 2D films and within 3D hydrogel were investigated. The gelation temperature and biocompatibility could be modulated by addition hydroxyethyl cellulose (HEC) to chitosan—glycerophosphate (CH—GP) formulation. The CH—GP—HEC liquid solution can turn into gel at body temperature and has highly compatible with BMSC. Therefore, the CH—GP—HEC gel could be used as an attractive injected in-situ forming scaffold for future applications of delivering biologically active therapeutics for tissue engineering filed.

Activation of membrane receptors by neurotransmitter released from temperature-sensitive hydrogels

The present paper describes the design, construction and testing of a temperature-sensitive N-isopropylacrylamide hydrogel device for studying the controlled presentation of gamma-aminobutyric acid (GABA) to GABA(C) membrane receptors expressed in Xenopus laevis oocytes. Upon temperature lowering, the GABA-loaded hydrogel positioned near the surface of the GABA(C)-expressing oocyte elicits a membrane current response resembling that induced by superfusion of the oocyte with free GABA. The response to cooling is not observed when GABA is omitted from the hydrogel loading solution. In addition, picrotoxin, a known GABA(C) receptor antagonist, inhibits the oocyte membrane current response associated with temperature lowering of GABA-loaded hydrogels. The data indicate that the present system affords a temperature-regulated release of GABA from the hydrogel and a resulting activation of the expressed GABA(C) receptors.