A Near-Infrared Photothermal-Responsive Underwater Adhesive with Tough Adhesion and Antibacterial Properties.

Developing tunable underwater adhesives that possess tough adhesion in service and easy detachment when required remains challenging. Herein, a strategy is proposed to design a near infrared (NIR) photothermal-responsive underwater adhesive by incorporating MXene (Ti3 C2 Tx )-based nanoparticles within isocyanate-modified polydimethylsiloxane (PDMS) polymer chains. The developed adhesive exhibits long-term and tough adhesion with an underwater adhesion strength reaching 5.478 MPa. Such strong adhesion is mainly attributed to the covalent bonds and hydrogen bonds at the adhesive-substrate interface. By making use of the photothermal-response of MXene-based nanoparticles and the thermal response of PDMS-based chains, the adhesive possesses photothermal-responsive performance, exhibiting sharply diminished adhesion under NIR irradiation. Such NIR-triggered tunable adhesion allows for easy and active detachment of the adhesive when needed. Moreover, the underwater adhesive exhibits photothermal antibacterial property, making it highly desirable for underwater applications. This work enhances the understanding of photothermal-responsive underwater adhesion, enabling the design of tunable underwater adhesives for biomedical and engineering applications.

An underwater stable and durable gelatin composite hydrogel coating for biomedical applications.

Developing underwater stable and durable hydrogel coatings with drag-reducing, drug release, and antibacterial properties is essential for lots of biomedical applications. However, most hydrogel coatings cannot meet the requirement of underwater stability and versatility, which severely limits their widespread use. In this work, an underwater stable, durable and substrate-independent gelatin composite hydrogel (GMP) coating is developed through covalent crosslinks, where a silane coupling agent with an unsaturated double bond is grafted onto a substrate of co-deposited polydopamine and polyethylenimine. GMP coating can be easily coated onto various medical device surfaces, such as artificial joints, catheters, tracheal tubes and titanium alloys, showing excellent structural stability and mechanical tunability under extreme conditions of ultrasonic treatment for 1 h (400 W of ultrasonic power) or underwater shearing for 14 days (400 rpm). Besides, friction experiment reveals that GMP coating exhibits good lubrication properties (coefficient of friction < 0.003). The drug-loading and bacterial inhibition ring tests show that the GMP coating has a tunable drug release ability with the final releasing ratios of 70-95% by changing the content of poly (ethylene glycol) diacrylate. This work offers a scalable approach of fabricating bio-functional and stable hydrogel coatings, which can be potentially used in biomedical applications.

Optimizing the Production of Hydrogel Microspheres Using Microfluidic Chips: The Influence of Surface Treatment on Droplet Formation Mechanism.

Microfluidic chips have been widely applied in biology and medical research for stably generating uniform droplets that can be solidified into hydrogel microspheres. However, issues such as low microsphere yield, lengthy experimental processes, and susceptibility to environmental interference need to be addressed. In this work, a simple and effective method was developed to modify microfluidic chips at room temperature to improve the production performance of hydrogel microspheres. Numerical simulation-assisted experiments were conducted to comprehensively understand the effect of solution viscosity, hydrophilicity, and flow rate ratio on droplet formation during microsphere production. Chitosan was selected as the main component and combined with poly(ethylene glycol) diacrylate to prepare photocurable hydrogel microspheres as a demonstration. As a result, grafting fluoro-silane (FOTS) increased the contact angle of the channel from 90 to approximately 110°, which led to a 12.2% increase in droplet yield. Additionally, FOTS-modification attenuated the impact of the flow rate ratio on droplet yield by 19.1%. Alternatively, depositing dopamine decreased the channel's contact angle from 90 to 60°, resulting in a 21.4% increase in particle size and enabling the chip to adjust droplet size over a wider range. Further study demonstrates that the obtained hydrogel microspheres can be modified with layers of aldehyde, which can potentially be used for controlled drug release. Overall, this study proposed a facile method for adjusting the yield and droplet size through surface treatment of microfluidic chips while also enhancing the understanding of the synergistic effects of multiple factors in microfluidics-based microsphere production.

Kneading-Dough-Inspired Quickly Dispersing of Hydrophobic Particles into Aqueous Solutions for Designing Functional Hydrogels.

Hydrogels containing hydrophobic materials have attracted great attention for their potential applications in drug delivery and biosensors. This work presents a kneading-dough-inspired method for dispersing hydrophobic particles (HPs) into water. The kneading process can quickly mix HPs with polyethyleneimine (PEI) polymer solution to form "dough", which facilitates the formation of stable suspensions in aqueous solutions. Combining with photo or thermal curing processes, one type of HPs incorporated PEI-polyacrylamide (PEI/PAM) composite hydrogel exhibiting good self-healing ability, tunable mechanical property is synthesized. The incorporating of HPs into the gel network results in the decrease in the swelling ratio, as well as the enhancement of the compressive modulus by more than five times. Moreover, the stable mechanism of polyethyleneimine-modified particles has been investigated using surface force apparatus, where the pure repulsion during approaching contributes to the good stability of the suspension. The stabilization time of the suspension is dependent on the molecular weight of PEI: the higher the molecular weight is, the better the stability of the suspension will be. Overall, this work demonstrates a useful strategy to introduce HPs into functional hydrogel networks. Future research can be focused on understanding the strengthening mechanism of HPs in the gel networks.