DLP 3D printed hydrogels with hierarchical structures post-programmed by lyophilization and ionic locking

Transforming Cell-Drug Interaction through Granular Hydrogel-Mediated Delivery of Polyplex Nanoparticles for Enhanced Safety and Extended Efficacy in Gene Therapy

The utilization of hydrogels for DNA/cationic polymer polyplex nanoparticle (polyplex) delivery has significantly advanced gene therapy in tissue regeneration and cancer treatment. However, persistent challenges related to the efficacy and safety of encapsulated polyplexes, stemming from issues such as aggregation, degradation, or difficulties in controlled release during or postintegration with hydrogel scaffolds, necessitate further exploration. Here, we introduce an injectable gene therapy gel achieved by incorporating concentrated polyplexes onto densely packed hydrogel microparticles (HMPs). Polyplexes, when uniformly adhered to the gene therapy gel through reversible electrostatic interactions, can detach from the HMP surface in a controlled manner, contrasting with free polyplexes, and thereby reducing dose-dependent toxicity during transfection. Additionally, the integration of RGD cell adhesion peptides enhances the scaffolding characteristics of the gel, facilitating cell adhesion, migration, and further minimizing toxicity during gene drug administration. Notably, despite the overall transfection efficiency showing average performance, utilizing confocal microscopy to meticulously observe and analyze the cellular states infiltrating into various depths of the gene therapy gel resulted in the groundbreaking discovery of significantly enhanced local transfection efficiency, with primary cell transfection approaching 80%. This phenomenon could be potentially attributed to the granular hydrogel-mediated delivery of polyplex nanoparticles, which revolutionizes the spatial and temporal distribution and thus the "encounter" mode between polyplexes and cells. Moreover, the gene therapy gel's intrinsic injectability and self-healing properties offer ease of administration, making it a highly promising candidate as a novel gene transfection gel dressing with significant potential across various fields, including regenerative medicine and innovative living materials.

Independent Configuration and Reprogramming of Porous Characters in Macroporous Hydrogel Enabled by the Orthogonal Dynamic Network

Macroporous hydrogels have attracted much attention in both industry and academia, where the morphological characteristics of pores are essential. Despite significant improvements on regulating porous structures, the independent configuration and reprogramming of porosity and pore size still remain challenging owing to the lack of a chemical design to decouple the mechanism for adjusting each characteristic. Here, we report a strategy to adaptively control porous features relying on an orthogonal dynamic network. Disulfide bonds are employed to relax polymer chains during freezing via UV irradiation, thus, generating pores in hydrogels. On such a basis, the porosity is continuously switched from 0 to 75% by controlling network relaxation ratios. Subsequently, the pore size is further reversibly manipulated through the association or dissociation of dynamic metallic coordination. As a result, the porosity and pore size achieved independent configurations. Meanwhile, the dynamic nature of the network makes it possible to reprogram the porous character of a prepared hydrogel. Beyond these, the photopatterning of pores represents the capability to regulate the third feature. Our strategy provides an effective way to arbitrarily manipulate porous morphologies, which can inspire the design of future functional porous materials.

A High-Density Hydrogen Bond Locking Strategy for Constructing Anisotropic High-Strength Hydrogel-Based Meniscus Substitute

Mimicking anisotropic features is crucial for developing artificial load-bearing soft tissues such as menisci). Here, a high-density hydrogen bond locking (HDHBL) strategy, involving preloading a poly(N-acryloylsemicarbazide) (PNASC) hydrogel with an aqueous solution containing a hydrogen bond breaking agent, followed by water exchange, to fabricate anisotropic high-strength hydrogels are proposed. During this process, multiple high-density hydrogen bonds of the PNASC network are re-established, firmly freezing oriented molecular chains, and creating a network with an anisotropic microstructure. The resulting anisotropic hydrogels exhibit superior mechanical properties: tensile strength over 9 MPa, Young's modulus exceeding 120 MPa along the orientation direction, and fatigue thresholds exceeding 1900 J m-2. These properties meet the mechanical demands for load-bearing tissue substitutes compared to other reported anti-fatigue hydrogels. This strategy enables the construction of an anisotropic meniscal scaffold composed of circumferentially oriented microfibers by preloading a digital light processing-3D printed PNASC hydrogel-based wedge-shaped construct with a resilient poly(N-acryloyl glycinamide) hydrogel. The 12-week implantation of a meniscus scaffold in rabbit knee joints after meniscectomy demonstrates a chondroprotective effect on the femoral condyle and tibial plateau, substantially ameliorating the progression of osteoarthritis. The HDHBL strategy enables the fabrication of various anisotropic polymer hydrogels, broadening their scope of application.

3D-Printed Hydrogel for Diverse Applications: A Review

Hydrogels have emerged as a versatile and promising class of materials in the field of 3D printing, offering unique properties suitable for various applications. This review delves into the intersection of hydrogels and 3D printing, exploring current research, technological advancements, and future directions. It starts with an overview of hydrogel basics, including composition and properties, and details various hydrogel materials used in 3D printing. The review explores diverse 3D printing methods for hydrogels, discussing their advantages and limitations. It emphasizes the integration of 3D-printed hydrogels in biomedical engineering, showcasing its role in tissue engineering, regenerative medicine, and drug delivery. Beyond healthcare, it also examines their applications in the food, cosmetics, and electronics industries. Challenges like resolution limitations and scalability are addressed. The review predicts future trends in material development, printing techniques, and novel applications.