A mucoadhesive drug delivery system can improve the effectiveness of a drug by maintaining the drug concentration and allowing targeting and localization of the drug at a specific site. Acrylic-based hydrogels have been used extensively as a mucoadhesive system owing to their flexibility and excellent bioadhesion. In this experiment, poly(acrylic acid) was selected to prepare the bioadhesive hydrogel adhering to mucosal surfaces using a radiation process. Poly(acrylic acid) was dissolved in water to a prepare poly(acrylic acid) solution, and the solution was then irradiated by an electron beam at up to 75 kGy to make hydrogels. Their physical properties, such as gel percent, swelling percent and adhesive strength to mucosal surfaces, were investigated. Triamcinolone acetonide was used as a model drug. The dried poly(acrylic acid) film was dipped in a 0.1 wt% triamcinolone acetonide solution in ethanol, and then dried at 25 °C. The release of triamcinolone acetonide was determined at different time intervals, and UV (Ultraviolet)-Vis spectroscopy was used to determine the released concentration of triamcinolone acetonide at 238 nm. It was shown that poly(acrylic acid)-based drug carriers were successfully prepared for use in a bioadhesive drug delivery system.

Conducting polymer (CP)-based hydrogels exhibit the behaviors of bending or contraction/relaxation due to electrical stimulation. They are similar in some ways to biological organs and have advantages regarding manipulation and miniaturization. Thus, these hydrogels have attracted considerable interest for biomedical applications. In this study, we prepared PPy/PVP hydrogel with different concentrations and content through polymerization and cross-linking induced by gamma-ray irradiation at 25 kGy to optimize the mechanical properties of the resulting PPy/PVP hydrogel. Optimization of the PPy/PVP hydrogel was confirmed by characterization using scanning electron microscopy, gel fraction, swelling ratio, and Fourier transform infrared spectroscopy. In addition, we assessed live-cell viability using live/dead assay and CCK-8 assay, and found good cell viability regardless of the concentration and content of Py/pTS. The conductivity of PPy/PVP hydrogel was at least 13 mS/cm. The mechanical properties of PPy/PVP hydrogel are important factors in their application for biomaterials. It was found that 0.15PPy/PVP20 (51.96 ± 6.12 kPa) exhibited better compressive strength than the other samples for use in CP-based hydrogels. Therefore, it was concluded that gamma rays can be used to optimize PPy/PVP hydrogel and that biomedical applications of CP-based hydrogels will be possible.

Bacterial cellulose (BC) is an excellent biomaterial with many medical applications. In this study, resorbable BC membranes were prepared for guided bone regeneration (GBR) using an irradiation technique for applications in the dental field. Electron beam irradiation (EI) increases biodegradation by severing the glucose bonds of BC. BC membranes irradiated at 100 kGy or 300 kGy were used to determine optimal electron beam doses. Electron beam irradiated BC membranes (EI-BCMs) were evaluated by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, thermal gravimetric analysis (TGA), and using wet tensile strength measurements. In addition, in vitro cell studies were conducted in order to confirm the cytocompatibility of EI-BCMs. Cell viabilities of NIH3T3 cells on 100k and 300k EI-BCMs (100 kGy and 300 kGy irradiated BC membranes) were significantly greater than on NI-BCMs after 3 and 7 days (p < 0.05). Bone regeneration by EI-BCMs and their biodegradabilities were also evaluated using in vivo rat calvarial defect models for 4 and 8 weeks. Histometric results showed 100k EI-BCMs exhibited significantly larger new bone area (NBA; %) than 300k EI-BCMs at 8 weeks after implantation (p < 0.05). Mechanical, chemical, and biological analyses showed EI-BCMs effectively interacted with cells and promoted bone regeneration.

Metronidazole (MD) is known as a periodontitis medicine and has been widely used in antibiotics for resistance to anaerobic bacteria, periodontal disease, and other threats. To treat diseases, drug delivery carriers are needed with a high bioadhesive property and enhanced drug penetration. Poly (acrylic acid) (PAA) hydrogel films have a good bioadhesive property and are able to localize the absorption site and increase the drug residence time. In this study, we fabricated a MD loaded PAA hydrogel with different MD content (0.1, 0.25, 0.5, and 1 wt%) using varying doses (25, 50, and 75 kGy) and the radiation doses (25, 50, or 75 kGy) in a one-step gamma-ray irradiation process. The chemical and physical structure were determined through a Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, gel content, and compressive strength. In addition, MD loaded PAA hydrogels were performed to MD release behaviors and cytotoxicity. Finally, we conducted antibacterial activity to demonstrate the prevention of growth of bacteria as a therapeutic dressing. The basic chemical structure analysis of MD was changed greatly at radiation doses of 50 and 75 kGy due to degradation by gamma-ray irradiation. However, when the absorbed dose was 25 kGy, the chemical structure analysis of MD did not change significantly, and the gel content and compressive strength of MD/PAA hydrogel were approximately 80% and 130 kPa, respectively. The MD/PAA hydrogels exhibited no cytotoxicity and good antibacterial activity against Escherichia coli, Staphylococcus aureus, and Streptococcus mutans. These results provide good evidence that MD/PAA hydrogel prepared by gamma-ray irradiation has potential as a competitive candidate for the therapeutic dressing.

Honey-based wound dressings have attracted a lot of attention from modern scientists owing to their anti-inflammatory and antibacterial effects without antibiotic resistance. Such dressings also promote moist wound healing, and have been considered natural, abundant, and cheap materials for folk marketing. This study investigated the various behaviors and characteristics of chestnut honey-impregnated carboxymethyl cellulose sodium hydrogel paste (CH–CMC) as a therapeutic dressing, such as its moist retention, antibacterial activity for inhibiting the growth of Staphylococcus aureus and Escherichia coli, and the rate of wound healing in db/db mice. The results provide good evidence, suggesting that CH–CMC has potential as a competitive candidate for diabetic ulcer wound healing.

Crosslinking of polyolefin-based polymers can improve their thermal and mechanical properties, which can then be used in various applications. Radiation-induced crosslinking can be done easily and usefully by irradiation without a crosslinking agent. In addition, polymer blending can improve thermal and mechanical properties, and chemical resistance, compared to conventional single polymers. In this study, high-density polyethylene (HDPE)/ethylene vinyl acetate (EVA)/polyurethane (PU) blends were prepared by radiation crosslinking to improve the thermal and mechanical properties of HDPE. This is because HDPE, a polyolefin-based polymer, has the weaknesses of low thermal resistance and flexibility, even though it has good mechanical strength and machinability. In contrast, EVA has good flexibility and PU has excellent thermal properties and wear resistance. The morphology and mechanical properties (e.g., tensile and flexure strength) were characterized using scanning electron microscopy (SEM) and a universal testing machine (UTM). The gel fraction, thermal shrinkage, and abrasion resistance of samples were confirmed. In particular, after storing at 180 °C for 1 h, the crosslinked HDPE-PU-EVA blends exhibited ~4-times better thermal stability compared to non-crosslinked HDPE. When subjected to a radiation dose of 100 kGy, the strength of HDPE increased, but the elongation sharply decreased (80%). On the other hand, the strength of the HDPE-PU-EVA blends was very similar to that of HDPE, and the elongation was more than 3-times better (320%). Finally, the abrasion resistance of crosslinked HDPE-PU-EVA was ~9-times better than the crosslinked HDPE. Therefore, this technology can be applied to various polymer products requiring high heat resistance and flexibility, such as electric cables and industrial pipes.