Poly(thioctic acid): From Bottom-Up Self-Assembly to 3D-Fused Deposition Modeling Printing

Exploring the application of piezoelectric ceramics in bone regeneration

Piezoelectric ceramics are piezoelectric materials with polycrystalline structure and have been widely used in many fields such as medical imaging and sound sensors. As knowledge about this kind of material develops, researchers find piezoelectric ceramics possess favorable piezoelectricity, biocompatibility, mechanical properties, porous structure and antibacterial effect and endeavor to apply piezoelectric ceramics to the field of bone tissue engineering. However, clinically no piezoelectric ceramics have been exercised so far. Therefore, in this paper we present a comprehensive review of the research and development of various piezoelectric ceramics including barium titanate, potassium sodium niobate and zinc oxide ceramics and aims to explore the application of piezoelectric ceramics in bone regeneration by providing a detailed overview of the current knowledge and research of piezoelectric ceramics in bone tissue regeneration.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Rapidly Gelled Lipoic Acid-Based Supramolecular Hydrogel for 3D Printing of Adhesive Bandage

Developing a strongly adhesive, easily removable, and robust bandage is valuable in trauma emergencies. Poly(lipoic acid) (PLA)-based adhesives with good mechanical properties have been well-developed through a thermal ring-opening polymerization (ROP) method that is easiness. However, the additive manufacturing of PLA-based adhesives remains a challenge. Herein, α-lipoic acid (LA) and trometamol (Tris) are found to rapidly form a supramolecular hydrogel at room temperature with injectability and 3D printing potential. Meanwhile, the synthesized LA-grafted hyaluronic acid and cellulose nanocrystals are involved not only to optimize the extrusion of 3D printing but also to effectively promote fidelity and prevent the inverse closed-loop depolymerization of PLA in water. The hydrogel bandage exhibits strong adhesion to skin while it can be removed with no residue by water flushing, showing protection to neo-tissue during dressing replacement. The in vivo application of the hydrogel bandage significantly promoted wound healing by closing the wound, forming a physical barrier, and providing an anti-inflammatory effect, showing great potential in future clinical applications.

Arginine-solubilized lipoic acid-induced β-sheets of silk fibroin-strengthened hydrogel for postoperative rehabilitation of breast cancer

Breast cancer is the most common cancer among women worldwide, and adjuvant radiotherapy (RT) following tumor removal is one of the most commonly used treatments for breast cancer. However, the high risk of tumor recurrence and inevitable radiation skin injury after RT remain fatal problems, seriously challenging the patient's postoperative rehabilitation. Herein, a multifunctional poly (lipoic acid)-based hydrogel is constructed through one-step heating the mixture of α-lipoic acid (LA)/arginine (Arg)/silk fibroin (SF), without introducing any non-natural molecules. The multiple synergistic interactions among LA, Arg, and SF not only enhance the solubilization of LA in aqueous systems but also stabilize poly(lipoic acid) through strong salt bridge hydrogen bonds and ionic hydrogen bonds. Intriguingly, the LA-based surfactant induced β-sheet transformation of SF can further modulate the bulk strength of the hydrogel. Regulating the content of LA in hydrogels not only allows efficient control of hydrogel bioactivity but also enables the evolution of hydrogels from injectable forms to adhesive patches. Based on the different biological activities and forms of hydrogels, they can be implanted internally or applied externally on the mice's skin, achieving simultaneous prevention of tumor recurrence post-surgery and assistance in treating radiation-induced skin damage after radiotherapy.

Optically transparent and mechanically tough glass with impact resistance and flame retardancy enabled by covalent/supramolecular interactions

Exploring glass materials beyond inorganic components represents a new direction in the development of artificial transparent materials. Inspired by the successes of polymeric and supramolecular glasses, we shifted our attention to the preparation of a transparent glass through the polymerization of low-molecular-weight monomers that are naturally tailored with noncovalent recognition motifs. In this work, an imidazolium unit bearing a vinyl group and a tetrafluoroborate counter anion was selected to construct an artificial glass. Experimental and theoretical investigations revealed that the cross-linking behavior of anions effectively transformed linear polymeric chains into three-dimensional networks. The polymeric-supramolecular glass exhibits a tough tensile strength (61.31 MPa), high Young's modulus (1.17 GPa), and good optical transparency (>90%), which are comparable to those of polymethyl methacrylate. Moreover, the obtained glass maintains excellent mechanical toughness and optical transparency over a wide temperature range (from -150 to 150 °C). The material shows a superior impact resistance (18.34 kJ m-2) and flame retardancy (V0 rating), which are barely achieved by supramolecular materials.

An injectable biomimetic hydrogel adapting brain tissue mechanical strength for postoperative treatment of glioblastoma without anti-tumor drugs participation

Adapting the mechanical strength between the implant materials and the brain tissue is crucial for the postoperative treatment of glioblastoma. However, no related study has been reported. Herein, we report an injectable lipoic acid‑iron (LA-Fe) hydrogel (LFH) that can adapt to the mechanical strength of various brain tissues, including human brain tissue, by coordinating Fe3+ into a hybrid hydrogel of LA and its sodium salt (LANa). When LFH, which matches the mechanical properties of mouse brain tissue (337 ± 8.06 Pa), was injected into the brain resection cavity, the water content of the brain tissue was maintained at a normal level (77%). Similarly, LFH did not induce the activation or hypertrophy of glial astrocytes, effectively preventing brain edema and scar hyperplasia. Notably, LFH spontaneously degrades in the interstitial fluid, releasing LA and Fe3+ into tumor cells. The redox couples LA/DHLA (dihydrolipoic acid, reduction form of LA in cells) and Fe3+/Fe2+ would regenerate each other to continuously provide ROS to induce ferroptosis and activate immunogenic cell death. As loaded the anti-PDL1, anti-PDL1@LFH further enhanced the efficacy of tumor-immunotherapy and promoted tumor ferroptosis. The injectable hydrogel that adapted the mechanical strength of tissues shed a new light for the tumor postoperative treatment.

An organic/inorganic hybrid soft material for supramolecular adhesion

Thioctic acid (TA) has been widely used to construct soft materials via supramolecular copolymerization with organic chemicals. In this study, TA and the inorganic compound MoS2 are used to fabricate poly[TA-MoS2] via dynamic covalent and supramolecular interactions. Poly[TA-MoS2] exhibits good and long-lasting adhesion performance on various artificial surfaces, with an adhesion strength up to 3.72 MPa (15 days). Further, it exhibits tough adhesion effects in an aqueous environment. Moreover, poly[TA-MoS2] displays good thermal processing behavior, thus enabling its molding through 3D printing.

Biomass and Transparent Supramolecular Elastomers for Green Electronics Enabled by the Controlled Growth and Self-Assembly of Dynamic Polymer Networks

Determining the optimal method for preparing supramolecular materials remains a profound challenge. This process requires a combination of renewable raw materials to create supramolecular materials with multiple functions and properties, including simple fabrication, sustainability, a dynamic nature, good toughness, and transparency. In this work, a strategy is presented for toughening supramolecular networks based on solid-phase chain extension. This toughening strategy is simple and environmentally friendly. In addition, a series of biobased elastomers are designed and prepared with adjustable performance characteristics. This strategy can significantly improve the transparency, tensile strength, and toughness of the synthesized elastomer. The synthesized biobased elastomers have great ductility, repairability, and recyclability, and they show good adhesion and dielectric properties. A biobased ionic skin is assembled from these biobased elastomers. Assembled ionic skin can sensitively detect external stimuli (such as stretching, bending, compression, or temperature changes) and monitor human movement. The conductive and dielectric layers of the biobased ionic skin are both obtained from renewable raw materials. This research provides novel molecular design approaches and material selection methods for promoting the development of green electronic devices and biobased elastomers.

Supramolecular/Dynamic Covalent Design of High-Performance Pressure-Sensitive Adhesive from Natural Low-Molecular-Weight Compounds

Adhesive materials have played an essential role in the history of humanity. Natural adhesives composed of low-molecular-weight monomers have been overshadowed by modern petroleum-based glues. With the development of green economy, the demand for eco-friendly materials has increased. Herein, two natural biocompatible compounds, namely thioctic acid (TA) and malic acid (MA), are selected to prepare a high-performance pressure-sensitive adhesive poly[TA-MA]. This adhesive can be quantitatively obtained via a simple mixing and heating process. Poly[TA-MA] shows interesting and useful properties, including reversible flexibility, high elongation, and good self-healing, owing to its dynamic polymerization pattern and reversible cross-linking behavior. Poly[TA-MA] exhibits excellent adhesion performance under various extreme conditions, such as at low temperatures and in hot water. High values of shear strength (3.86 MPa), peel strength (7.90 N cm-1), loop tack (10.60 N cm-1), tensile strength (1.02 MPa), and shear resistance (1628 h) demonstrate the strong adhesive effect of poly[TA-MA]. Additionally, TA can be regenerated in the monomer forms from poly[TA-MA] with high recovery rate (>90%). Meanwhile, strong anti-bacterial behavior of poly[TA-MA] is recorded. This study not only reported a new pressure-sensitive adhesive but also fully displayed the feasibility of using natural small molecules to achieve robust surface adhesion.

Biological applications of lipoic acid-based polymers: an old material with new promise

Lipoic acid (LA) is a versatile antioxidant that has been used in the treatment of various oxidation-reduction diseases over the past 70 years. Owing to its large five-membered ring tension, the dynamic disulfide bond of LA is highly active, enabling the formation of poly(lipoic acid) (PLA) via ring-opening polymerization (ROP). Herein, we first summarize disulfide-mediated ROP polymerization strategies, providing basic routes for designing and preparing PLA-based materials. PLA, as a biologically derived, low toxic, and easily modified material, possesses dynamic disulfide bonds and universal non-covalent carboxyl groups. We also shed light on the biomedical applications of PLA-based materials based on their biological and structural features and further divide recent works into six categories: antibacterial, anti-inflammation, anticancer, adhesive, flexible electronics, and 3D-printed tissue scaffolds. Finally, the challenges and future prospects associated with the biomedical applications of PLA are discussed.

Passerini polymerization of α-lipoic acid for dynamically crosslinking 1,2-dithiolane-functionalized polymers

Passerini polymerization using naturally occurring α-lipoic acid as a raw material yields polyamides with 1,2-dithiolane functional groups in a one-step reaction. The polyamide exhibits characteristics of an adaptable dynamically crosslinked network through reversible ring-opening reaction of 1,2-dithiolane, enabling self-healing, reusable strong adhesion, and regeneration through decrosslinking and re-crosslinking.

3D bioprinting approaches for spinal cord injury repair

Regenerative healing of spinal cord injury (SCI) poses an ongoing medical challenge by causing persistent neurological impairment and a significant socioeconomic burden. The complexity of spinal cord tissue presents hurdles to successful regeneration following injury, due to the difficulty of forming a biomimetic structure that faithfully replicates native tissue using conventional tissue engineering scaffolds. 3D bioprinting is a rapidly evolving technology with unmatched potential to create 3D biological tissues with complicated and hierarchical structure and composition. With the addition of biological additives such as cells and biomolecules, 3D bioprinting can fabricate preclinical implants, tissue or organ-like constructs, andin vitromodels through precise control over the deposition of biomaterials and other building blocks. This review highlights the characteristics and advantages of 3D bioprinting for scaffold fabrication to enable SCI repair, including bottom-up manufacturing, mechanical customization, and spatial heterogeneity. This review also critically discusses the impact of various fabrication parameters on the efficacy of spinal cord repair using 3D bioprinted scaffolds, including the choice of printing method, scaffold shape, biomaterials, and biological supplements such as cells and growth factors. High-quality preclinical studies are required to accelerate the translation of 3D bioprinting into clinical practice for spinal cord repair. Meanwhile, other technological advances will continue to improve the regenerative capability of bioprinted scaffolds, such as the incorporation of nanoscale biological particles and the development of 4D printing.

A supramolecular approach for converting renewable biomass into functional materials

The rational transformation and utilization of biomass have attracted increasing attention because of its high importance in sustainable development and green economy. In this study, we used a supramolecular approach to convert biomass into functional materials. Six biomass raw materials with distinct chemical structures and physical properties were copolymerized with thioctic acid (TA) to afford poly[TA-biomass]s. The solvent-free copolymerization leads to the convenient and quantitative fabrication of biomass-based versatile materials. The non-covalent bonding and reversible solid-liquid transitions in poly[TA-biomass]s endow them with diversified features, including thermal processability, 3D printing, wet and dry adhesion, recyclability, impact resistance, and antimicrobial activity. Benefiting from their good biocompatibility and nontoxicity, these biomass-based materials are promising candidates for biological applications.

Super Adhesive Fluorescent Materials for Encrypted Messages, Underwater Leak Repair, and Their Potential Application in Fluorescent Tattoos

Achieving high-performance luminescence for underwater bonding remains a significant challenge in materials science. This study addresses this issue by synthesizing a luminescent material based on an aggregation-induced emission (AIE) monomer and copolymerizing it with lipoic acid (LA) to create an AIE supramolecular polymer. The resulting copolymer exhibits strong fluorescence under ultraviolet (UV) irradiation at 365 nm due to the AIE of TPEE and enables underwater adhesion. The P(LA-TPEE) polymer demonstrates potential for digital encryption and decryption of quick response (QR) codes underwater. Furthermore, it can dissolve well in anhydrous ethanol, producing an environment-friendly and super waterproof adhesive. Most notably, the P(LA-TPEE) solution can be sprayed on human skin, creating an invisible tattoo that only became visible under UV light due to the hydrogen bond (H-bond) and π-π structures. This smart tattoo can be quickly wiped away with alcohol, avoiding the painful and harmful process of tattoo removal. It can also be repeatedly applied to draw the preferred tattoo pattern. This AIE supramolecular polymer shows great potential in underwater adhesion and repair, underwater message encryption, and non-toxic and painless invisible tattooing. Overall, this study provides a valuable approach for material design in the future.

Supramolecular Soft Material Enabled by Metal Coordination and Hydrogen Bonding: Stretchability, Self-Healing, Impact Resistance, 3D Printing, and Motion Monitoring

Metal coordination can significantly improve the macroscopic performance of many materials by enhancing their dynamic features. In this study, two supramolecular interactions, Fe³⁺ -carboxylic acid coordination, and structural water-induced hydrogen bonding, into an artificial polymer were introduced. Various attractive features, including flexibility and stretchability, are achieved because of the bulk state and dynamic hydrogen bonds of poly(thioctic acid-water) (poly[TA-H]). These unique features are considerably enhanced after the incorporation of Fe³⁺ cations into poly[TA-H] because metal coordination increased the mobility of the poly[TA-H] chains. Thus, the poly(thioctic acid-water-metal) (poly[TA-HM]) copolymer exhibited better flexibility and stretchability. Moreover, notable underwater/low-temperature self-healing capacity is obtained via the synergistic effect of the metal and hydrogen bonding. Most of the impact energy is quickly absorbed by poly[TA-H] or poly[TA-HM] and effectively and rapidly dissipated via reversible debonding/bonding via the interactions between the metal and hydrogen. Macroscopic plastic deformation or structural failure is not observed during high-speed (50-70 m s^-1 ) impact experiments or high-altitude (90 m) falling tests. Furthermore, poly[TA-HM] displayed good thermal molding properties, which enabled its processing via 3D fused deposition modeling printing. Poly[TA-HM] also showed considerable effectiveness for monitoring complicated, dynamic, and irregular biological activities owing to its highly pressure-sensitive nature.