Adhesive protein-free synthetic hydrogels for retinal pigment epithelium cell culture with low ROS level

Development of a novel self-healing Zn(II)-metallohydrogel with wide bandgap semiconducting properties for non-volatile memory device application

A rapid and effective strategy has been devised for the swift development of a Zn(II)-ion-based supramolecular metallohydrogel, termed Zn@PEH, using pentaethylenehexamine as a low molecular weight gelator. This process occurs in an aqueous medium at room temperature and atmospheric pressure. The mechanical strength of the synthesized Zn@PEH metallohydrogel has been assessed through rheological analysis, considering angular frequency and oscillator stress dependencies. Notably, the Zn@PEH metallohydrogel exhibits exceptional self-healing abilities and can bear substantial loads, which have been characterized through thixotropic analysis. Additionally, this metallohydrogel displays injectable properties. The structural arrangement resembling pebbles within the hierarchical network of the supramolecular Zn@PEH metallohydrogel has been explored using FESEM and TEM measurements. EDX elemental mapping has confirmed the primary chemical constituents of the metallohydrogel. The formation mechanism of the metallohydrogel has been analyzed via FT-IR spectroscopy. Furthermore, zinc(II) metallohydrogel (Zn@PEH)-based Schottky diode structure has been fabricated in a lateral metal-semiconductor-metal configuration and  it's charge transport behavior has also been studied. Notably, the zinc(II) metallohydrogel-based resistive random access memory (RRAM) device (Zn@PEH) demonstrates bipolar resistive switching behavior at room temperature. This RRAM device showcases remarkable switching endurance over 1000 consecutive cycles and a high ON/OFF ratio of approximately 270. Further, 2 × 2 crossbar array of the RRAM devices were designed to demonstrate OR and NOT logic circuit operations, which can be extended for performing higher order computing operations. These structures hold promise for applications in non-volatile memory design, neuromorphic and in-memory computing, flexible electronics, and optoelectronic devices due to their straightforward fabrication process, robust resistive switching behavior, and overall system stability.

Self-Healing Alginate Hydrogel Formed by Dynamic Benzoxaborolate Chemistry Protects Retinal Pigment Epithelium Cells against Oxidative Damage

Oxidative stress is considered as a major factor causing retinal pigment epithelium (RPE) dysfunction and finally leading to retinal diseases such as age-related macular degeneration (AMD). Developing hydrogels for RPE cell delivery, especially those with antioxidant feature, is emerging as a promising approach for AMD treatment. Herein, a readily prepared antioxidant alginate-based hydrogel was developed to serve as a cytoprotective agent for RPE cells against oxidative damage. Alg-BOB was synthesized via conjugation of benzoxaborole (BOB) to the polysaccharide backbone. Hydrogels were formed through self-crosslinking of Alg-BOB based on benzoxaborole-diol complexation. The resulting hydrogel showed porous micro-structure, pH dependent mechanical strength and excellent self-healing, remolding, and injectable properties. Moreover, the hydrogel exhibited excellent cytocompatibility and could efficiently scavenge reactive oxygen species (ROS) to achieve an enhanced viability of ARPE-19 cells under oxidative condition. Altogether, our study reveals that the antioxidant Alg-BOB hydrogel represents an eligible candidate for RPE delivery and AMD treatment.

Injectable Hydrogel Based on Gellan Gum/Silk Sericin for Application as a Retinal Pigment Epithelium Cell Carrier

The damage to retinal pigment epithelium (RPE) cells can lead to vision loss and permanent blindness. Therefore, an effective therapeutic strategy has emerged to replace damaged cells through RPE cell delivery. In this study, we fabricated injectable gellan gum (GG)/silk sericin (SS) hydrogels as a cell carrier by blending GG and SS. To determine the appropriate concentration of SS for human RPE ARPE-19, 0, 0.05, 0.1, and 0.5% (w/v) of SS solution were blended in 1% (w/v) GG solution (GG/SS 0%, GG/SS 0.05%, GG/SS 0.1%, and GG/SS 0.5%, respectively). The physical and chemical properties were measured through Fourier-transform infrared spectroscopy, scanning electron microscopy, mass swelling, and weight loss. Also, viscosity, injection force, and compressive tests were used to evaluate mechanical characteristics. Cell proliferation and differentiation of ARPE-19 were evaluated using quantitative dsDNA analysis and real-time polymerase chain reaction, respectively. The addition of SS gave GG/SS hydrogels a compressive strength similar to that of natural RPE tissue, which may well support the growth of RPE and enhance cell proliferation and differentiation. In particular, the GG/SS 0.5% hydrogel showed the most similar compressive strength (about 10 kPa) and exhibited the highest gene expression related to ARPE-19 cell proliferation. These results indicate that GG/SS 0.5% hydrogels can be a promising biomaterial for cell delivery in retina tissue engineering.

Hawthorn polyphenols reduce high glucose-induced inflammation and apoptosis in ARPE-19 cells by regulating miR-34a/SIRT1 to reduce acetylation

Diabetic retinopathy is a major complication in patients with diabetes. Herein, we investigate how hawthorn polyphenol extract (HPE) affects high glucose-induced oxidation, inflammation, and apoptosis in ARPE-19 cells. HPLC-MS/MS was used to determine HPE content and composition. Reactive oxygen species (ROS) production was assessed using fluorescence microscopy, while glucose-induced gene and protein expressions were analyzed using real-time PCR and western blotting in cells transfected with miR-34a mimics. We found that treating cells with 10 μg/ml of HPE, 30 μM procyanidin B2, chlorogenic acid, epicatechin, or resveratrol (positive control) significantly reduced ROS production and decreased apoptosis and inflammation-related factors (p < .01). Moreover, the expression level of SIRT1 was increased, while that of acetylated NF-κB p65 and p53 proteins was decreased. These data suggest that HPE can inhibit oxidative damage, inflammation, and apoptosis through the AMPK/SIRT1/NF-κB pathway, and decrease miR-34a/SIRT1/p53 pathway activation in ARPE-19 cells, thereby demonstrating a potential use as a food additive to mitigate hyperglycemia-induced retinal damage. PRACTICAL APPLICATIONS: Hawthorn polyphenol extract (HPE) significantly reduced ROS levels, apoptosis, and the expression of inflammation-related factors in ARPE-19 cells. HPE also inhibited the AMPK/SIRT1/NF-κB and miR-34a/SIRT1/p53 pathways, which are involved in hyperglycemia-induced inflammation and apoptosis of ARPE-19 cells by regulating acetylation. Thus, HPE, as a potential food additive, may mitigate hyperglycemia-induced retinal damage.

Regenerative medicine as a novel strategy for AMD treatment: a review

Age-related macular degeneration (AMD) is known as a major cause of irreversible blindness in elderly adults. The segment of the retina responsible for central vision damages in the disease process. Degeneration of retinal pigmented epithelium (RPE) cells, photoreceptors, and choriocapillaris associated with aging participate for visual loss. In 2010, AMD involved 6.6% of all blindness cases around the world. Some of the researches have evaluated the replacing of damaged RPE in AMD patients by using the cells from various sources. Today, the advancement of RPE differentiation or generation from stem cells has been gained, and currently, clinical trials are testing the efficiency and safety of replacing degenerated RPE with healthy RPE. However, the therapeutic success of RPE transplantation may be restricted unless the transplanted cells can be adhered, distributed and survive for long-term in the transplanted site without any infections. In recent years a variety of scaffold types were used as a carrier for RPE transplantation and AMD treatment. In this review, we have discussed types of scaffolds; natural or synthetic, solid or hydrogel and their results in RPE replacement. Eventually, our aim is highlighting the novel and best scaffold carriers that may have potentially promoting the efficacy of RPE transplantation.

The development of a rapid self-healing semiconducting monoethanolamine-based Mg(OH)2 metallogel for a Schottky diode application with a high ON/OFF ratio

A rapid self-healing Mg(OH)₂ metallogel developed by mixing monoethanolamine and an Mg(ii) salt offers a Schottky barrier diode device with a high ON/OFF ratio.

Enhanced retinal pigment epithelium (RPE) regeneration using curcumin/alginate hydrogels: In vitro evaluation

The retinal pigment epithelium (RPE) plays a significant role in retaining structural integrity of eye. Factors such as reduction in cell regeneration due to aging and physical injury pose a major hurdle in RPE regeneration. In this study, we exploited the use of alginate (AGT) incorporated with Curcumin (CCI) forming a hydrogel based system CCI/AGT. The fabricated hydrogel could anchor RPE cell in it. In vitro cell analysis revealed that the CCI/AGT hydrogel shows good biocompatibility, enhanced cell growth ability and higher ECM formation compared to the pure AGT hydrogel. In particular, the presence of CCI in the hydrogels enhances the cells proliferation of the 23% respect to the pure alginate. Also the expression of crucial genes for retina functions and matrix production were positively affected by CCI presence, with an increment of 45% for RPE65, 32% for CRALBP and 26% for Collagen type 1. In vitro tests demonstrated the potential application of CCI/AGT hydrogels for transplantation under the sub-retinal space acting as a cell delivery vehicle and also their capability to provide an appropriate environment for RPE regeneration. These results suggest that CCI/AGT hydrogel could be translated into a potential surgical graft for biological implantation of retinal tissue engineering.

Photochemical coating of Kapton® with hydrophilic polymers for the improvement of neural implants

The polyimide Kapton® was coated photochemically with hydrophilic polymers to prevent undesirable cell growth on the polyimide surface. The polymer coatings were generated using photochemically reactive polymers synthesized by a simple and modular strategy. Suitable polymers or previously synthesized copolymer precursors were functionalized with photoactive arylazide groups by a polymer analogous amide coupling reaction with 4-azidobenzoic acid. A photoactive chitosan derivative (chitosan-Az) and photochemically reactive copolymers containing DMAA, DEAA or MTA as primary monomers were synthesized using this method. The amount of arylazide groups in the polymers was adjusted to approximately 5%, 10% and 20%. As coating on Kapton® all polymers effect a significantly reduced water contact angle (WCA) and consequently a rise of the surface hydrophilicity compared to the untreated Kapton®. The presence of the polymer coatings was also proven by ATR-IR spectroscopy. Coatings with chitosan-Az and the DEAA copolymer cause a distinct inhibition of the growth of fibroblasts. In the case of the DMAA copolymer even a strong anti-adhesive behavior towards fibroblasts was verified. Biocompatibility of the polymer coatings was proven which enables their utilization in biomedical applications.

Self-healing polysaccharide-based hydrogels as injectable carriers for neural stem cells

Self-healing injectable hydrogels can be formulated as three-dimensional carriers for the treatment of neurological diseases with desirable advantages, such as avoiding the potential risks of cell loss during injection, protecting cells from the shearing force of injection. However, the demands for biocompatible self-healing injectable hydrogels to meet above requirements and to promote the differentiation of neural stem cells (NSCs) into neurons remain a challenge. Herein, we developed a biocompatible self-healing polysaccharide-based hydrogel system as a novel injectable carrier for the delivery of NSCs. N-carboxyethyl chitosan (CEC) and oxidized sodium alginate (OSA) are the main backbones of the hydrogel networks, denoted as CEC-l-OSA hydrogel ("l" means "linked-by"). Owing to the dynamic imine cross-links formed by a Schiff reaction between amino groups on CEC and aldehyde groups on OSA, the hydrogel possesses the ability to self-heal into a integrity after being injected from needles under physiological conditions. The CEC-l-OSA hydrogel in which the stiffness mimicking nature brain tissues (100~1000 Pa) can be finely tuned to support the proliferation and neuronal differentiation of NSCs. The multi-functional, injectable, and self-healing CEC-l-OSA hydrogels hold great promises for NSC transplantation and further treatment of neurological diseases.

Polymer Coatings of Cochlear Implant Electrode Surface - An Option for Improving Electrode-Nerve-Interface by Blocking Fibroblast Overgrowth

Overgrowth of connective tissue and scar formation induced by the electrode array insertion increase the impedance and, thus, diminish the interactions between neural probes as like cochlear implants (CI) and the target tissue. Therefore, it is of great clinical interest to modify the carrier material of the electrodes to improve the electrode nerve interface for selective cell adhesion. On one side connective tissue growth needs to be reduced to avoid electrode array encapsulation, on the other side the carrier material should not compromise the interaction with neuronal cells. The present in vitro-study qualitatively and quantitatively characterises the interaction of fibroblasts, glial cells and spiral ganglion neurons (SGN) with ultrathin poly(N,N-dimethylacrylamide) (PDMAA), poly(2-ethyloxazoline) (PEtOx) and poly([2-methacryloyloxy)ethyl]trimethylammoniumchlorid) (PMTA) films immobilised onto glass surfaces using a photoreactive anchor layer. The layer thickness and hydrophilicity of the polymer films were characterised by ellipsometric and water contact angle measurement. Moreover the topography of the surfaces was investigated using atomic force microscopy (AFM). The neuronal and non-neuronal cells were dissociated from spiral ganglions of postnatal rats and cultivated for 48 h on top of the polymer coatings. Immunocytochemical staining of neuronal and intermediary filaments revealed that glial cells predominantly attached on PMTA films, but not on PDMAA and PEtOx monolayers. Hereby, strong survival rates and neurite outgrowth were only found on PMTA, whereas PDMAA and PEtOx coatings significantly reduced the SG neuron survival and neuritogenesis. As also shown by scanning electron microscopy (SEM) SGN strongly survived and retained their differentiated phenotype only on PMTA. In conclusion, survival and neuritogenesis of SGN may be associated with the extent of the glial cell growth. Since PMTA was the only of the polar polymers used in this study bearing a cationic charge, it can be assumed that this charge favours adhesion of both glial cells and SG neurons glial cells and SGN.

BODIPY based self-healing fluorescent gel formation via acylhydrazone linkage

Polymeric BODIPY derivatives with reactive functional groups undergo reversible formation of covalent bonds leading to self-healing properties.

Exceptionally tough and notch-insensitive magnetic hydrogels

Most existing magnetic hydrogels are weak and brittle. The development of strong and tough magnetic hydrogels would extend their applications into uncultivated areas, such as in actuators for soft machines and guided catheters for magnetic navigation systems, which is still a big challenge. Here a facile and versatile approach to fabricating highly stretchable, exceptionally tough and notch-insensitive magnetic hydrogels, Fe(3)O(4)@Fe-alginate/polyacrylamide (PAAm), is developed, by dispersing alginate-coated Fe(3)O(4) nanoparticles into the interpenetrating polymer networks of alginate and PAAm, with hybrid physical and chemical crosslinks. A cantilever bending beam actuator as well as a proof-of-concept magnetically guided hydrogel catheter is demonstrated. The method proposed in this work can be integrated into other strong and tough magnetic hydrogels for the development of novel hydrogel nanocomposites with both desirable functionality and superior mechanical properties.

Self-healing gels based on constitutional dynamic chemistry and their potential applications

This review presents recent developments and potential applications of physical and chemical self-healing gels based on constitutional dynamic chemistry.