UV-Vis/FT-NIR in situ monitoring of visible-light induced polymerization of PEGDA hydrogels initiated by eosin/triethanolamine/O2

Visible Light Cross-Linked Methacrylated Silk Fibroin Enables Enhanced Osteogenic Response in Bioprinted Dual-Layer Guided Bone Regeneration Membrane

Precise design and fabrication of photo-cross-linked hydrogels with controlled network architecture and tailored mechanical properties are essential for advancing complex tissue engineering applications. In this study, a visible-light-activated type II photo-cross-linking system was developed using eosin Y/triethanolamine/N-vinylpyrrolidone (VE) to fabricate methacrylated silk fibroin (SFM) hydrogels through oxygen-mediated controlled photolysis. In comparison to conventional UV-initiated lithium phenyl-2,4,6-trimethylbenzoylphosphinate cross-linking, which rapidly yields mechanically stiffer networks with pronounced β-structures, the VE system (0.02 mM eosin Y, 100 mM triethanolamine, and 50 mM N-vinylpyrrolidone) enabled the fabrication of gradually formed compliant homogeneous networks. This tunability allowed using VE cross-linked SFM in light-assisted extrusion bioprinting to fabricate a dual-layer guided bone regeneration membrane incorporating a collagen I-rich ECM layer. Under calcium-supplemented conditions, the dual-layer membrane exhibited robust osteogenic potential, evidenced by significantly elevated ALP activity and distinctive nodular mineralization patterns compared with single-layer controls. Gene expression profiles revealed coordinated regulation of early (RUNX2, COL1A1), mid-to-late (SPP1, SPARC), and late-stage (BGLAP) markers, indicating successful progression through the osteogenic program. The heterogeneous design achieved a desired balance between its barrier function and tissue integration with an interconnected porous architecture that limits soft tissue downgrowth while supporting matrix organization conducive to bone regeneration. These findings establish critical structure-function relationships in photo-cross-linked biomaterials and highlight how mechanistic understanding of cross-linking chemistry can guide the rational design of functional scaffolds for biomedical applications.

Dual Photoredox Catalysis Strategy for Enhanced Photopolymerization-Based Colorimetric Biodetection

Catalytic redox reactions have been employed to enhance colorimetric biodetection signals in point-of-care diagnostic tests, while their time-sensitive visual readouts may increase the risk of false results. To address this issue, we developed a dual photocatalyst signal amplification strategy that can be controlled by a fixed light dose, achieving time-independent colorimetric biodetection in paper-based tests. In this method, target-associated methylene blue (MB⁺) photocatalytically amplifies the concentration of eosin Y by oxidizing deactivated eosin Y (EYH^3-) under red light, followed by photopolymerization with eosin Y autocatalysis under green light to generate visible hydrogels. Using the insights from mechanistic studies on MB⁺-sensitized photo-oxidation of EYH^3-, we improved the photocatalytic efficiency of MB⁺ by suppressing its degradation. Lastly, we characterized 100- to 500-fold enhancement in sensitivity obtained from MB⁺-specific eosin Y amplification, highlighting the advantages of using dual photocatalyst signal amplification.

Effect of TEOA on the Process of Photopolymerization at 532 nm and Properties of Nanogels

Nanogel is an important kind of biomaterials applied for wound dressings, drug delivery, medical diagnostics and biosensors. The properties of nanogels closely depend on the density of the crosslinking network. In this study, the role of triethanolamine (TEOA) in the effect on the crosslinking degree of nanogels based on poly(ethylene glycol) diacrylate (PEGDA) was investigated and illustrated. The effect of TEOA on the process of photopolymerization at 532 nm and properties of the nanogels was systematically investigated by using UV-vis spectroscopy, FT-IR spectroscopy, ¹ H NMR, DLS, SEM, AFM and DSC. In brief, the double bond conversion of photopolymerization and the crosslinking degree of nanogels can be effectively regulated by TEOA.

Cancer theranostic platforms based on injectable polymer hydrogels

Theranostic platforms that combine therapy with diagnosis not only prevent the undesirable biological responses that may occur when these processes are conducted separately, but also allow individualized therapies for patients. Polymer hydrogels have been employed to provide well-controlled drug release and targeted therapy in theranostics, where injectable hydrogels enable non-invasive treatment and monitoring with a single injection, offering greater patient comfort and efficient therapy. Efforts have been focused on applying injectable polymer hydrogels in theranostic research and clinical use. This review highlights recent progress in the design of injectable polymer hydrogels for cancer theranostics, particularly focusing on the elements/components of theranostic hydrogels, and their cross-linking strategies, structures, and performance with regard to drug delivery/tracking. Therapeutic agents and tracking modalities that are essential components of the theranostic platforms are introduced, and the design strategies, properties and applications of the injectable hydrogels developed via two approaches, namely chemical bonds and physical interactions, are described. The theranostic functions of the platforms are highly dependent on the architecture and components employed for the construction of hydrogels. Challenges currently presented by theranostic platforms based on injectable hydrogels are identified, and prospects of acquiring more comfortable and personalized therapies are proposed.

Experimental validation of eosin-mediated photo-redox polymerization mechanism and implications for signal amplification applications

When eosin-mediated, photo-redox polymerization is used to amplify signals in biosensing, oxygen has dual, opposing roles.

Preparation of ultrasmall nanogels by facile emulsion-free photopolymerization at 532 nm

Nanogels have been widely prepared and characterized in recent years due to their unique advantages. Here, an effective, original, and facile method of emulsion-free photopolymerization at 532 nm without surfactant was developed to prepare nanogels based on poly(ethylene glycol) diacrylate (PEGDA). The 532 nm continuous laser with symmetrical energy distribution like a three-dimensional shape of a straw hat was used to control the reaction region. The self-emulsification of PEGDA in water was studied and PEGDA micelles were directly cross-linked by controlling the laser energy. The number of micelles participating in the microreaction region and the double bond crosslinking between micellar aggregates and inside micelles were reasonably regulated. The size of the nanogels could be effectively modulated by controlling reaction parameters including laser power, monomer concentration, initiator concentration, and reaction time. Finally, ultrasmall nanogels with around 30 nm in size were prepared by balancing double bond crosslinking between micellar aggregates and inside micelles.

Spatiotemporally Controlled Photoresponsive Hydrogels: Design and Predictive Modeling from Processing through Application

Photoresponsive hydrogels (PRHs) are soft materials whose mechanical and chemical properties can be tuned spatially and temporally with relative ease. Both photo-crosslinkable and photodegradable hydrogels find utility in a range of biomedical applications that require tissue-like properties or programmable responses. Progress in engineering with PRHs is facilitated by the development of theoretical tools that enable optimization of their photochemistry, polymer matrices, nanofillers, and architecture. This review brings together models and design principles that enable key applications of PRHs in tissue engineering, drug delivery, and soft robotics, and highlights ongoing challenges in both modeling and application.

Radical polymerization reactions for amplified biodetection signals

This review summarizes various radical polymerization chemistries for amplifying biodetection signals and compares them from the practical point of view.

Controlled Electron-Beam Synthesis of Transparent Hydrogels for Drug Delivery Applications

In this study, we highlight hydrogels prepared by electron-beam polymerization. In general, the electron-beam-polymerized hydrogels showed improved mechanical and optical transmittances compared to the conventional UV-cured hydrogels. They were more elastic and had a higher crosslinking density. Additionally, they were transparent over a broader wavelength range. The dependence of the mechanical and optical properties of the hydrogels on the number of single differential and total irradiation doses was analyzed in detail. The hydrogels were prepared for usage as a drug delivery material with methylene blue as a drug model. In the first set of experiments, methylene blue was loaded reversibly after the hydrogel synthesis. Electron-beam-polymerized hydrogels incorporated twice as much methylene blue compared to the UV-polymerized gels. Furthermore, the release of the model drug was found to depend on the crosslinking degree of the hydrogels. In addition, electron-beam polymerization enabled the irreversible binding of the drug molecules if they were mixed with monomers before polymerization.

On the role of N-vinylpyrrolidone in the aqueous radical-initiated copolymerization with PEGDA mediated by eosin Y in the presence of O2

A ground-state complex between eosin and N-vinylpyrrolidone impacts the photo-initiated synthesis of PEG hydrogels.

Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA): New Insights and Opportunities

The polymerization-induced self-assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo-PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo-PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo-PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self-assembly process. The purpose of this mini-review is therefore to examine some of these recent advances that have been made in Photo-PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.

Metal-Free Photoinduced Electron Transfer-Atom Transfer Radical Polymerization Integrated with Bioinspired Polydopamine Chemistry as a Green Strategy for Surface Engineering of Magnetic Nanoparticles

Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with the bioinspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator. Metal-free PET-ATRP technique was then employed for controlled architecture of poly(glycidyl methacrylate) (PGMA) brushes from the core-shell MNPs by using diverse organic dyes as photoredox catalysts. Impacts of light sources (including UV and visible lights), photoredox catalysts, and polymerization time on the composition and morphology of the PGMA brushes were investigated. Moreover, the versatility of the PGMA-functionalized core-shell MNPs was demonstrated by covalent attachment of ethylenediamine (EDA), a model functional molecule, which afforded the MNPs with improved hydrophilicity, dispersibility, and superior binding ability to uranyl ions. The green methodology by integrating metal-free PET-ATRP with facile PDA chemistry would provide better opportunities for surface modification of MNPs and miscellaneous nanomaterials for biomedical and electronic applications.

Quantitatively monitoring polymer chain growth and topology formation based on monodisperse polymers

In this work, a novel technique for monitoring polymer chain growth and topology formation was demonstrated by precision synthesis of monodisperse polymers, which opened a novel avenue for obtaining real-time polymer structure information.

Highly sensitive visual detection of mutant DNA based on polymeric nanoparticles-participating amplification

Taking advantage of the nanoparticles' large surface area and structural repeating characteristics, polymeric nanoparticles-participating polymerization-based amplification system was designed to enhance the sensitivity of detection.