Synthesis, properties, and applications of a polyampholyte hydroxypropyl chitosan derivative with the phenylboronic acid functional group.

Phenylboronic acid (PBA) groups are effective in building glucose-responsive drug delivery systems. Chitosan (CS) offers distinct advantages in the construction of PBA-based biomaterials, such as biodegradability and biocompatibility. However, challenges still persist due to the limited solubility of CS. This study proposes an efficient approach to introduce PBA groups into CS chains within 1 h via the O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU)-mediated amidation between 3-carboxyphenylboronic acid (CPBA) and O-hydroxypropyl chitosan (HPCS). The results showed that a wide range of substitution degrees, from 0.15 to 0.78, could be finely controlled by the amount of CPBA added. Furthermore, the obtained novel carboxyphenylboronic acid-grafted hydroxypropyl chitosan (PBA-HPCS) derivative showed enhanced crystallinity and thermostability compared to HPCS, and it demonstrated solubility in an alkaline solution. Based on the reversible bonding between the boronic acid group and cis-1,2/1,3-diols, PBA-HPCS was successfully used as an efficient crosslinker for the preparation of hydrogels incorporating sorbitol and polyhydroxy polymers, such as guar gum and polyvinyl alcohol. These hydrogels exhibited rapid gelation, rapid self-healing, injectability, and responsiveness to glucose and pH. These findings suggest that PBA-HPCS holds promise for advancing the development of PBA-based biomaterials.

GC/QQQ coupling with metabolomics for selection of predicator of tea fermentation.

Fermentation is the most crucial process for manufacture of black tea. Signature components were desired for the establishment of accurate prediction of fermentation degree. In this study, finished black teas were prepared using leaves that had been fermented for various times, and sensory quality evaluation was performed. Tracking analysis of volatiles during fermentation was conducted to discriminate the iconic compounds. On the basis of both the sensory evaluation results and the enzymatic oxidation traits of fermentation, the ratio of ß-cyclocitral to γ-pylpyrone was proposed as an indicator. A positive correlation was observed between this ratio and the sensory score of finished black tea with varied duration of fermentation, and the correlation coefficient was 0.78. Furthermore, widely plant-targeted metabolomics was applied to cognize the fermentation. Comparative analysis of metabolites was conducted by category, and special attention was paid to flavonoids and terpenes. Significant metabolic differences emerged discriminatively. The results would be useful for intelligent modulation of the manufacture of black tea.

Study on TEMPO-Mediated Oxidation of N-Succinyl Chitosan and the Water Retention Property.

C-6 oxidized chitosan is of great interest in obtaining a new moisture retention polymer like hyaluronic acid. The direct C-6 specific oxidation of chitosan mediated by the TEMPO/NaClO/NaBr system has proven to be difficult because of the high crystalline and high C-2 amino group content. In this work, the pre-modification of chitosan by N-succinylation was investigated and followed by the TEMPO-mediated C-6 specific oxidation under homogeneous conditions. The desired 6-oxidized N-succinyl chitosan product was obtained within 15 min with a yield of about 92%. The structure of these chitosan derivatives was confirmed by FTIR and NMR spectroscopy. Moreover, it was observed that the selective oxidation led to a great improvement in water solubility and moisture retention ability. These results present a wide range of possibilities for expanding the utilization of chitosan resources.

A Novel pH- and Salt-Responsive N-Succinyl-Chitosan Hydrogel via a One-Step Hydrothermal Process.

In this study, we synthesized a series of pH-sensitive and salt-sensitive N-succinyl-chitosan hydrogels with N-succinyl-chitosan (NSCS) and the crosslinker glycidoxypropyltrimethoxysilane (GPTMS) via a one-step hydrothermal process. The structure and morphology analysis of the NSCS and glycidoxypropyltrimethoxysilane-N-succinyl chitosan hydrogel (GNCH) revealed the close relation between the swelling behavior of hydrogels and the content of crosslinker GPTMS. The high GPTMS content could weaken the swelling capacity of hydrogels and improve their mechanical properties. The hydrogels show high pH sensitivity and reversibility in the range of pH 1.0 to 9.0, and exhibit on-off switching behavior between acidic and alkaline environments. In addition, the hydrogels perform smart swelling behaviors in NaCl, CaCl2, and FeCl3 solutions. These hydrogels may have great potential in medical applications.