Photopolymerized PVA-g-GMA Hydrogels for Biomedical Applications: Factors Affecting Hydrogel Formation and Bioevaluation Tests

β-Lactoglobulin-based aerogels: Facile preparation and sustainable removal of organic contaminants from water

Economically and efficiently removing organic pollutants from water is still a challenge in wastewater treatment. Utilizing environmentally friendly and readily available protein-based natural polymers to develop aerogels with effective removal performance and sustainable regeneration capability is a promising strategy for adsorbent design. Here, a robust and cost-effective method using inexpensive β-lactoglobulin (BLG) as raw material was proposed to fabricate BLG-based aerogels. Firstly, photocurable BLG-based polymers were synthesized by grafting glycidyl methacrylate. Then, a cross-linking reaction, including photo-crosslinking and salting-out treatment, was applied to prepared BLG-based hydrogels. Finally, the BLG-based aerogels with high porosity and ultralight weight were obtained after freeze-drying. The outcomes revealed that the biocompatible BLG-based aerogels exhibited effective removal performance for a variety of organic pollutants under perfectly quiescent conditions, and could be regenerated and reused many times via a simple and rapid process of acid washing and centrifugation. Overall, this work not only demonstrates that BLG-based aerogels are promising adsorbents for water purification but also provides a potential way for the sustainable utilization of BLG.

Histological evaluation of the regenerative potential of a novel photocrosslinkable gelatin-treated dentin matrix hydrogel in direct pulp capping: an animal study

BACKGROUND

To assess histologically the success of the pulp capping approach performed in traumatically exposed dogs' teeth using a novel injectable gelatin-treated dentin matrix light cured hydrogel (LCG-TDM) compared with LCG, MTA and TheraCal LC.

METHODS

Sixty-four dogs' teeth were divided into two groups (each including 32 teeth) based on the post-treatment evaluation period: group I: 2 weeks and group II: 8 weeks. Each group was further subdivided according to the pulp capping material into four subgroups (n = 8), with subgroup A (light-cured gelatin hydrogel) as the control subgroup, subgroup B (LCG-TDM), subgroup C (TheraCal LC), and subgroup D (MTA). Pulps were mechanically exposed in the middle of the cavity floor and capped with different materials. An assessment of periapical response was performed preoperatively and at 8 weeks. After 2 and 8-week intervals, the dogs were sacrificed, and the teeth were stained with hematoxylin-eosin and graded by using a histologic scoring system. Statistical analysis was performed using the chi-square and Kruskal-Wallis tests (p = 0.05).

RESULTS

All subgroups showed mild inflammation with normal pulp tissue at 2 weeks with no significant differences between subgroups (p ≤ 0.05), except for the TheraCal LC subgroup, which exhibited moderate inflammation (62.5%). Absence of a complete calcified bridge was reported in all subgroups at 2 weeks, while at 8 weeks, the majority of samples in the LCG-TDM and MTA-Angelus subgroups showed complete dentin bridge formation and absence of inflammatory pulp response with no significant differences between them (p ≤ 0.05). However, the formed dentin in the LCG-TDM group was significantly thicker, with layers of ordered odontoblasts identified to create a homogeneous tubular structure and numerous dentinal tubule lines suggesting a favourable trend towards dentin regeneration. TheraCal LC samples revealed a reasonably thick dentin bridge with moderate inflammation (50%) and LCG showed heavily fibrous tissue infiltrates with areas of degenerated pulp with no signs of hard tissue formation.

CONCLUSIONS

LCG-TDM, as an extracellular matrix-based material, has the potential to regenerate dentin and preserve pulp vitality, making it a viable natural alternative to silicate-based cements for healing in vivo dentin defects in direct pulp-capping procedures.

Development of Poly(vinyl alcohol) Grafted Glycidyl Methacrylate/Cellulose Nanofiber Injectable Hydrogels for Meniscus Tissue Engineering

This study aimed to develop poly (vinyl alcohol) grafted glycidyl methacrylate/cellulose nanofiber (PVA-g-GMA/CNF) injectable hydrogels for meniscus tissue engineering. PVA-g-GMA is an interesting polymer for preparing cross-linking injectable hydrogels with UV radiation, but it has poor mechanical properties and low cell proliferation. In this study, CNF as a reinforcing agent was selected to improve mechanical properties and cell proliferation in PVA-g-GMA injectable hydro-gels. The effect of CNF concentration on hydrogel properties was investigated. Both PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3, 0.5, and 0.7% (w/v) CNF can be formed by UV curing at a wavelength of 365 nm, 6 mW/cm2 for 10 min. All hydrogels showed substantial microporosity with interconnected tunnels, and a pore size diameter range of 3-68 µm. In addition, all hydrogels also showed high physicochemical properties, a gel fraction of 81-82%, porosity of 83-94%, water content of 73-87%, and water swelling of 272-652%. The water content and swelling of hydrogels were increased when CNF concentration increased. It is worth noting that the reduction of porosity in the hydrogels occurred with increasing CNF concentration. With increasing CNF concentration from 0.3% to 0.7% (w/v), the compressive strength and compressive modulus of the hydrogels significantly increased from 23 kPa to 127 kPa and 27 kPa to 130 kPa, respectively. All of the hydrogels were seeded with human cartilage stem/progenitor cells (CSPCs) and cultured for 14 days. PVA-g-GMA hydrogels incorporating 0.5% and 0.7% (w/v) CNF demonstrated a higher cell proliferation rate than PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3% (w/v) CNF, as confirmed by MTT assay. At optimum formulation, 10%PVA-g-GMA/0.7%CNF injectable hydrogel met tissue engineering requirements, which showed excellent properties and significantly promoted cell proliferation, and has a great potential for meniscus tissue engineering application.

Photocrosslinkable gelatin-treated dentin matrix hydrogel as a novel pulp capping agent for dentin regeneration: I. synthesis, characterizations and grafting optimization

BACKGROUND

In recent years, treated dentin matrix (TDM) has been introduced as a bioactive hydrogel for dentin regeneration in DPC. However, no study has introduced TDM as a photocrosslinkable hydrogel with a natural photoinitiating system. Therefore, the present study aimed to explore the synthesis, characterizations and grafting optimization of injectable gelatin- glycidyl methacrylate (GMA)/TDM hydrogels as a novel photocrosslinkable pulp capping agent for dentin regeneration.

METHODS

G-GMA/TDM hydrogel was photocrosslinked using a new two-component photoinitiating system composed of riboflavin as a photoinitiator under visible light and glycine as a first time coinitiator with riboflavin. The grafting reaction conditions of G-GMA/TDM e.g. GMA concentration and reaction time were optimized. The kinetic parameters e.g. grafting efficiency (GE) and grafting percentage (GP%) were calculated to optimize the grafting reaction, while yield (%) was determined to monitor the formation of the hydrogel. Moreover, G-GMA/TDM hydrogels were characterized by swelling ratio, degradation degree, and cytotoxicity. The instrumental characterizations e.g. FTIR, 1H-NMR, SEM and TGA, were investigated for verifying the grafting reaction. Statistical analysis was performed using F test (ANOVA) and Post Hoc Test (P = 0.05).

RESULTS

The grafting reaction dramatically increased with an increase of both GMA concentration and reaction time. It was realized that the swelling degree and degradation rate of G-GMA/TDM hydrogels were significantly reduced by increasing the GMA concentration and prolonging the reaction time. When compared to the safe low and moderate GMA content hydrogels (0.048, 0.097 M) and shorter reaction times (6, 12, 24 h), G-GMA/TDM with high GMA contents (0.195, 0.391 M) and a prolonged reaction time (48 h) demonstrated cytotoxic effects against cells using the MTT assay. Also, the morphological surface of G-GMA/TDM freeze-dried gels was found more compacted, smooth and uniform due to the grafting process. Significant thermal stability was noticed due to the grafting reaction of G-GMA/TDM throughout the TGA results.

CONCLUSIONS

G-GMA/TDM composite hydrogel formed by the riboflavin/glycine photoinitiating system is a potential bioactive and biocompatible system for in-situ crosslinking the activated-light pulp capping agent for dentin regeneration.

Methacrylated Silk Fibroin Hydrogels: pH as a Tool to Control Functionality

The last decade has witnessed significant progress in the development of photosensitive polymers for in situ polymerization and 3D printing applications. Light-mediated sol-gel transitions have immense potential for tissue engineering applications as cell-laden materials can be crosslinked within minutes under mild environmental conditions. Silk fibroin (SF) is extensively explored in regenerative medicine applications due to its ease of modification and exceptional mechanical properties along with cytocompatibility. To efficiently design SF materials, the in vivo assembly of SF proteins must be considered. During SF biosynthesis, changes in pH, water content, and metal ion concentrations throughout the silkworm gland divisions drive the transition from liquid silk to its fiber form. Herein, we study the effect of the glycidyl-methacrylate-modified SF (SilkMA) solution pH on the properties and secondary structure of SilkMA hydrogels by testing formulations prepared at pH 5, 7, and 8. Our results demonstrate an influence of the prepolymer solution pH on the hydrogel rheological properties, compressive modulus, optical transmittance, and network swellability. The hydrogel pH did not affect the in vitro viability and morphology of human dermal fibroblasts. This work demonstrates the utility of the solution pH to tailor the SilkMA conformational structure development toward utility and function and shows the need to strictly control the pH to reduce batch-to-batch variability and ensure reproducibility.

Gelatin/poly(vinyl alcohol) based hydrogel film - A potential biomaterial for wound dressing: Experimental design and optimization followed by rotatable central composite design

The development of hydrogel films for biomedical applications is interesting due to their characteristics. Hydrogel films based on gelatin and poly(vinyl alcohol) (PVA) are developed and characterized using a rotatable central composite design. The optimized hydrogel film is obtained by the function desirability of the Statistica® software and is also characterized by swelling kinetics, oxygen permeability, adhesiveness, TGA, DSC, and XRD. The results of the experimental design show that gelatin and PVA concentrations have a significant influence on the response variables, and the exposure doses to UV light show no significant effect. The optimized hydrogel film is elastic, presents good mechanical resistance and swelling capacity in water and exudate solution, is permeable to oxygen, and is capable of adjusting itself and maintains contact close to the skin. In this way, considering all the properties evaluated, the optimized film has characteristics suitable for biomedical applications as wound dressings.

Water-Soluble Photoinitiators in Biomedical Applications

Light-initiated polymerization processes are currently an important tool in various industrial fields. The advancement of technology has resulted in the use of photopolymerization in various biomedical applications, such as the production of 3D hydrogel structures, the encapsulation of cells, and in drug delivery systems. The use of photopolymerization processes requires an appropriate initiating system that, in biomedical applications, must meet additional criteria such as high water solubility, non-toxicity to cells, and compatibility with visible low-power light sources. This article is a literature review on those compounds that act as photoinitiators of photopolymerization processes in biomedical applications. The division of initiators according to the method of photoinitiation was described and the related mechanisms were discussed. Examples from each group of photoinitiators are presented, and their benefits, limitations, and applications are outlined.

Electron beam-based fabrication of crosslinked hydrophilic carbon electrodes and their application for capacitive deionization

In this research, we demonstrated that a crosslinked hydrophilic carbon electrode with better electrochemical performance than hydrophobic counterparts can easily be produced using room-temperature, quick electron-beam irradiation with a hydrophilic methacryloyl-substituted polyvinyl alcohol (SPVA) binder. The SPVA binder was effectively synthesized by trans-esterification of PVA with glycidyl methacrylate. The hydrophilic carbon electrode cast on a graphite sheet from a slurry of activated carbon (AC) and SPVA was irradiated with an electron beam to form a crosslinked structure. The analytical results in terms of the morphology, solvent resistance, chemical composition, and contact angle revealed that the carbon electrode was completely crosslinked by electron-beam irradiation even at the dose of 100 kGy (irradiation time = 180 s). The new electrode exhibited superior water-wettability due to the hydrophilic functionality of SPVA. Furthermore, the hydrophilic carbon electrode with an AC : SPVA composition of 90 : 10 and an absorbed dose of 200 kGy, exhibited a specific capacitance of 127 F g-1 (67% higher than the hydrophobic poly(vinylidene fluoride) (PVDF)-based counterpart with the same composition). The specific capacitance was further improved to 160 F g-1 with an increase in the AC content. The hydrophilic carbon electrode exhibited noticeably better desalination efficiency than the hydrophobic PVDF-based counterpart.