Hyaluronic acid/tannic acid hydrogel sunscreen with excellent anti-UV, antioxidant, and cooling effects.

Excessive exposure to UV radiation is one of the major factors that causes skin aging, erythema, burns, and skin cancer. Recently, the usage of sunscreens for skin protection has increased because the amount of UV radiation reaching the Earth's surface has increased owing to the destruction of the ozone layer that blocks UV radiation. Hydrogels with a three-dimensional network structure exhibit physical and chemical properties that are similar to those of the extracellular matrix in the human body, a high water content, flexibility, and biocompatibility. Therefore, they are applied in a wide range of fields, such as in cosmetics, medicines, and pharmaceuticals. However, conventional hydrogel-based sunscreens have drawbacks such as complicated process conditions, high cost, and low biocompatibility. In this study, a novel hydrogel-type sunscreen with excellent UV protection and cooling effects was prepared by a very simple process using two natural materials, hyaluronic acid (HA) and tannic acid (TA). The HA/TA hydrogels exhibited broad-spectrum UV protection in the UVA and UVB regions (280-360 nm). In addition, they showed excellent adhesion to the skin surface, antioxidative activity, cooling effect, and high moisture content, demonstrating great application potential as a hydrogel-type sunscreen.

Effect of tannic acid on the mechanical and adhesive properties of catechol-modified hyaluronic acid hydrogels.

Hyaluronic acid (HA) is applied in various fields, including pharmaceutical science, owing to its favorable biological properties such as moisture retention, non-toxicity, biodegradability, biocompatibility and biodegradability. In particular, many studies have aimed at its application in the form of a hydrogel. However, the applications of HA hydrogels are limited owing to their poor mechanical properties. In this study, an HA-catechol conjugate (HA-Cat) was synthesized by reacting the HA polymer with dopamine to improve its adhesion to various substrates. The HA-Cat hydrogel was prepared via oxidative crosslinking using a small amount of NaIO4 as the oxidant, and the hydrogel formation was investigated by rheological and mechanical studies. Further, the effect of tannic acid (TA) on the adhesive strength and compressive strength of the HA-Cat/TA hydrogels was examined according to the amount of NaIO4 used for crosslinking and the TA contents. Both the adhesive and compressive properties of the HA-Cat hydrogels were improved with the addition of TA. The HA-based hydrogels containing TA have great potential as cost-effective and biocompatible medical adhesives.

Self-crosslinkable hyaluronate-based hydrogels as a soft tissue filler.

With increasing interest in aging and skin care, the use of fillers to increase the volume of soft tissue volume is increasing globally. However, the side effects caused by the residual chemical crosslinking agents present in these fillers limit the effective application of commercialized filler products. Therefore, the development of a novel crosslinking system with a non-toxic chemical crosslinking agent is required to overcome the limitations of commercial hyaluronate (HA)-based fillers. In this paper, a new injectable hydrogel with enhanced mechanical properties, tissue adhesion, injectability, and biocompatibility is reported. The HA derivatives modified with catechol groups (HA-DA) were crosslinked by self-oxidation under in vivo physiological conditions (pH 7.4) without chemical crosslinkers to form hydrogels, which can be further accelerated by the dissolved oxygen in the body. The fabricated HA-DA filler showed excellent mechanical properties and could be easily injected with a low injection force. Further, the HA-DA filler stably attached to the injection site due to the tissue adhesion properties of the catechol groups, thus leading to an improved displacement stability. In addition, the HA-DA filler showed excellent cell viability, cell proliferation, and biocompatibility. Therefore, the HA-DA hydrogel is a novel soft tissue filler with great potential to overcome the limitations of commercial soft tissue fillers.

Visible-light-induced hyaluronate hydrogel for soft tissue fillers.

Hyaluronic acid (HA) is widely used as a filler owing to its excellent biocompatibility and biodegradability. However, commercial HA-based filler products have some limitations and can cause side effects due to the presence of residual chemical crosslinking agents. In this study, tyramine (Tyr) was introduced into HA to impart photocrosslinking ability to HA, and a photocrosslinked hydrogel was formed using a less toxic vitamin B2 derivative as a photoinitiator. For injection, an injectable filler was prepared by converting the photocrosslinked hydrogel to a microgel form. The crosslinking of the tyramine-modified HA (HA-Tyr) hydrogel, which can be applied as a soft tissue filler, increased with an increase in the irradiation time, and the crosslinked hydrogel showed excellent mechanical strength, elastic recovery rate, and injectability. It also showed non-cytotoxicity and cell proliferation behavior in fibroblasts. Therefore, injectable HA hydrogels have great potential as an alternative to conventional commercial dermal fillers.

Effect of photoinitiator on chain degradation of hyaluronic acid.

OBJECTIVES: Photocrosslinking systems of polymers have been widely studied using UV or visible light irradiation. However, the photodegradation behavior derived from light irradiation was rarely reported, comparing with the photocrosslinking. In this study, the tyramine-modified hyaluronic acid (HA/Tyr) hydrogel was prepared using riboflavin (RF) as a photoinitiator, and the degradation behavior of HA by the reactive oxygen species (ROS) generated in photochemical process was investigated. MATERIALS AND METHODS: The HA/Tyr conjugate was synthesized by EDC/NHS chemistry to introduce phenol group. Degree of substitution (DS, %) of phenol group to HA molecule was about 25%. The structural change of HA/Tyr was measured by proton nuclear magnetic resonance (1H-NMR) and attenuated total reflectance infrared spectroscopy (ATR-FTIR), and the rheological properties of photocrosslinked HA/Tyr hydrogel were investigated by rheometer. RESULTS: The HA/Tyr solution with 25% substitution formed a stable hydrogel via visible light irradiation in the presence of RF photoinitiator. Rheological data of HA/Tyr solution showed that the storage modulus (G') was increased with increasing HA concentration. Additionally, it was found that RF initiated by visible light irradiation induced the degradation of HA molecular chain, and consequently reduced the viscosity of HA/Tyr solutions. CONCLUSION: The results indicate that RF-based photoinitiator system caused the degradation of HA molecule by ROS generated in photochemical process as well as the crosslinking of HA/Tyr.

Phosphorylated JNK mediated apoptosis induced by all trans retinoid acid in human retinoblastoma cell line / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the mechanism of all trans retinoid acid (ATRA) inhibition of cell growth and induction of apoptosis in human retinoblastoma Y79 cells.</p><p><b>METHODS</b>Antiproliferating effects of ATRA on Y79 cells were studied by (3)H-thymidine incorporation. Cell cycle analysis was performed by flow cytometry, apoptosis of the ATRA-treated cells was determined by DNA fragmentation analysis and JNK phosphorylation analyzed by Western blot.</p><p><b>RESULTS</b>After 36h treatment of 1 micro mol/L ATRA, (3)H-thymidine incorporation decreased to 40% with Y79 cells arrested in G(0)/G(1) and Sub-G(1) peak appeared. DNA ladder was observed in DNA fragmentation analysis after 36h treatment of ATRA. Curcumin, a JNK blocker, blocked the apoptosis and the growth inhibition induced by ATRA. JNK was phosphorylated in 10 to 20 min.</p><p><b>CONCLUSION</b>ATRA can induce the apoptosis in Y79 cells by phosphorylation of JNK, which suggests that ATRA may have clinical application prospects for treatment of retinoblastoma.</p>