Citrate-Based Polyester Elastomer with Artificially Regulatable Degradation Rate on Demand.

Citrate-based polymers are commonly used to create biodegradable implants. In an era of personalized medicine, it is highly desired that the degradation rates of citrate-based implants can be artificially regulated as required during clinical applications. Unfortunately, current citrate-based polymers only undergo passive degradation, which follows a specific degradation profile. This presents a considerable challenge for the use of citrate-based implants. To address this, a novel citrate-based polyester elastomer (POCSS) with artificially regulatable degradation rate is developed by incorporating disulfide bonds (S-S) into the backbone chains of the crosslinking network of poly(octamethylene citrate) (POC). This POCSS exhibits excellent and tunable mechanical properties, notable antibacterial properties, good biocompatibility, and low biotoxicity of its degradation products. The degradation rate of the POCSS can be regulated by breaking the S-S in its crosslinking network using glutathione (GSH). After a period of subcutaneous implantation of POCSS scaffolds in mice, the degradation rate eventually increased by 2.46 times through the subcutaneous administration of GSH. Notably, we observed no significant adverse effects on its surrounding tissues, the balance of the physiological environment, major organs, and the health status of the mice during degradation.

Quadruple H-Bonding and Polyrotaxanes Dual Cross-linking Supramolecular Elastomer for High Toughness and Self-healing Conductors.

Tough and self-healable substrates can enable stretchable electronics long service life. However, for substrates, it still remains a challenge to achieve both high toughness and autonomous self-healing ability at room temperature. Herein, a strategy by using the combined effects between quadruple H-bonding and slidable cross-links is proposed to solve the above issues in the elastomer. The elastomer exhibits high toughness (77.3 MJ m-3 ), fracture energy (≈127.2 kJ m-2 ), and good healing efficiency (91 %) at room temperature. The superior performance is ascribed to the inter and intra crosslinking structures of quadruple H-bonding and polyrotaxanes in the dual crosslinking system. Strain-induced crystallization of PEG in polyrotaxanes also contributes to the high fracture energy of the elastomers. Furthermore, based on the dual cross-linked supramolecular elastomer, a highly stretchable and self-healable electrode containing liquid metal is also fabricated, retaining resistance stability (0.16-0.26 Ω) even at the strain of 1600 %.

Sliding Cyclodextrin Molecules along Polymer Chains to Enhance the Stretchability of Conductive Composites.

The demand for stretchable electronics with a broader working range is increasing for wide application in wearable sensors and e-skin. However, stretchable conductors based on soft elastomers always exhibit low working range due to the inhomogeneous breakage of the conductive network when stretched. Here, a highly stretchable and self-healable conductor is reported by adopting polyrotaxane and disulfide bonds into the binding layer. The binding layer (PR-SS) builds the bridge between polymer substrates (PU-SS) and silver nanowires (AgNWs). The incorporation of sliding molecules endows the stretchable conductor with a long sensing range (190%) due to the energy dissipation derived from the sliding nature of polyrotaxanes, which is two times higher than the working range (93%) of conductors based on AP-SS without polyrotaxanes. Furthermore, the mechanism of sliding effect for the polyrotaxanes in the elastomers is investigated by SEM for morphological change of AgNWs, in situ small-angle x-ray scattering, as well as stress relaxation experiments. Finally, human-body-related sensing tests and a self-correction system in fitness are designed and demonstrated.

Tough and Water-Resistant Bioelastomers with Active-Controllable Degradation Rates.

Biodegradable electronic devices have gained significant traction in modern medical applications. These devices are generally desired to have a long enough working lifetime for stable operation and allow for active control over their degradation rates after usage. However, current biodegradable materials used as encapsulations or substrates for these devices are challenging to meet the two requirements due to the constraints of inadequate water resistance, poor mechanical properties, and passive degradation characteristics. Herein, we develop a novel biodegradable elastomer named POC-SS-Res by introducing disulfide linkage and resveratrol (Res) into poly(1,8-octanediol-co-citrate) (POC). Compared to POC, POC-SS-Res exhibits good water resistance and excellent mechanical properties in PBS, providing effective protection for devices. At the same time, POC-SS-Res offers the unique advantage of an active-controllable degradation rate, and its degradation products express low biotoxicity. Good biocompatibility of POC-SS-Res is also demonstrated. Bioelectronic components encapsulated with POC-SS-Res have an obvious prolongation of working lifetime in PBS compared to that encapsulated with POC, and its degradation rate can be actively controlled by the addition of glutathione (GSH).

Hybrid Double-Sided Tape with Asymmetrical Adhesion and Burst Pressure Tolerance for Abdominal Injury Treatment.

Patients with open abdominal (OA) wounds have a mortality risk of up to 30%, and the resulting disabilities would have profound effects on patients. Here, we present a novel double-sided adhesive tape developed for the management of OA wounds. The tape features an asymmetrical structure and employs an acellular dermal matrix (ADM) with asymmetric wettability as a scaffold. It is constructed by integrating a tissue-adhesive hydrogel composed of polydopamine (pDA), quaternary ammonium chitosan (QCS), and acrylic acid cross-linking onto the bottom side of the ADM. Following surface modification with pDA, the ADM would exhibit characteristics resistant to bacterial adhesion. Furthermore, the presence of a developed hydrogel ensures that the tape not only possesses tissue adhesiveness and noninvasive peelability but also effectively mitigates damage caused by oxidative stress. Besides, the ADM inherits the strength of the skin, imparting high burst pressure tolerance to the tape. Based on these remarkable attributes, we demonstrate that this double-sided (D-S) tape facilitates the repair of OA wounds, mitigates damage to exposed intestinal tubes, and reduces the risk of intestinal fistulae and complications. Additionally, the D-S tape is equally applicable to treating other abdominal injuries, such as gastric perforations. It effectively seals the perforation, promotes injury repair, and prevents the formation of postoperative adhesions. These notable features indicate that the presented double-sided tape holds significant potential value in the biomedical field.

Improvement in bacterial cellulose production by co-culturing Bacillus cereus and Komagataeibacter xylinus.

Bacterial cellulose (BC) is a bio-produced nanostructure material widely used in biomedical, food, and paper-manufacturing industries. However, low production efficiency and high-cost have limited its industrial applications. This study aimed to examine the level of improvement in BC production by co-culturing Bacillus cereus and Komagataeibacter xylinus. The BC yield in corn stover enzymatic hydrolysate was found to be obviously enhanced from 1.2 to 4.4 g/L after the aforementioned co-culturing. The evidence indicated that acetoin (AC) and 2,3-butanediol (2,3-BD) produced by B. cereus were the key factors dominating BC increment. The mechanism underlying BC increment was that AC and 2,3-BD increased the specific activity of AC dehydrogenase and the contents of adenosine triphosphate (ATP) and acetyl coenzyme A (acetyl-CoA), thus promoting the growth and energy level of K. xylinus. Meanwhile, the immobilization of BC could also facilitate oxygen acquisition in B. cereus under static conditions. This study was novel in reporting that the co-culture could effectively enhance BC production from the lignocellulosic enzymatic hydrolysate.

The association between circadian rhythm of cortisol and shift work regularity among midwives-A multicenter study in Southeast China.

Objective: This article aims to explore the association between the trends of cortisol rhythm and the regularity of shift work among midwives. Methods: Midwives from six Southeast Chinese hospitals were recruited through cluster sampling in a multi-center cross-sectional study. Urine samples were collected half an hour after waking up, at 11:00, 19:00, and 23:00 on two consecutive days in a longitudinal cohort. The urinary cortisol was assayed by the chemiluminescence method. Results: A total of 86 midwives were included in this study, contributing 688 cortisol samples. The midwives displayed a circadian rhythm in cortisol secretion, with zeniths in the morning and nadirs in the evening. The trend of the first day was repeated on the second day. Although the total working hours per week of the two groups, namely the regular shift group (N = 43) and the irregular shift group (N = 43), were the same, significant main effects of groups (F = 62.569, p < 0.001), time (F = 45.304, p < 0.001), and group-by-time interaction (F = 226.695, p < 0.001) were indicated through linear mixed models. The main effect of day was not statistically significant, with F = 0.105 and p = 0.746. The fluctuation range of cortisol curve in the group with irregular schedules was slightly lower than that in the group with regular schedules. Conclusion: Our results may indicate that cortisol was more inhibited in midwives with irregular shift patterns than those with regular shift patterns. It is necessary to further study the relationship between cortisol rhythm and patterns of midwives' shifts in future so as to lay a foundation for hospital managers to develop a more reasonable scheduling system for midwives with the further purpose to minimize their occupational fatigue and ensure the safety of mothers and infants.