Dr. Jun Feng

Blood-contacting medical devices play a crucial role in clinical interventions, but their susceptibility to thrombosis and inflammation poses serious risks to treatment outcomes and patient safety. This study presents a novel coating that combines dendritic polyglycerol amine (dPGA), dendritic polyglycerol aldehyde (dPG-CHO), and linear polyglycerol sulfate (lPGS) using a layer-by-layer self-assembly method (LBL) on a polystyrene surface. The immobilization of dendritic polyglycerol enhances surface coverage, enabling the incorporation of a higher density of heparin-mimicking lPGS, while the covalent bonding ensures the coating's long-term stability. Compared to the pristine substrate, the coating significantly reduced platelet adhesion and activation. Notably, its hemocompatibility effects persist even after 30 days. Furthermore, co-incubation experiments with RAW264.7 macrophages confirmed the anti-inflammatory properties of the polyglycerol-based coating. These results demonstrate that this heparin-mimetic coating effectively improves the hemocompatibility of polystyrene and has the potential to be applied to other blood-contacting materials.

Multimaterial optical fibers provide a versatile platform for integrating diverse functionalities—such as waveguiding, side emission, sensing, and actuation—into a single filament. Although traditional multimaterial fibers have primarily been fabricated from rigid materials such as silica and thermoplastics for optoelectronic applications, recent developments have shifted the focus toward soft systems composed of elastomers, hydrogels, and their composites. Owing to their mechanical compliance and biocompatibility, these soft fibers are particularly well suited for wearable, implantable, and tissue-integrated devices used in diagnostics and phototherapy. This review provides a comprehensive overview of the rapidly developing field of soft multimaterial optical fibers, highlighting key material combinations and fabrication strategies that enable multifunctional performance. Particular emphasis is placed on extrusion-based multimaterial printing—including coaxial and segmented extrusion—which has significantly expanded the architectural and functional design space of soft optical fibers. Remaining challenges, including material compatibility, interfacial and surface quality, and printing resolution, are critically discussed. Finally, the review outlines emerging opportunities for advancing these fabrication approaches toward practical and clinically relevant biomedical applications.

The application of optical technologies in treating pathologies and monitoring disease states requires the development of soft, minimal invasive and implantable devices to deliver light to tissues inside the body. Here, we present soft and degradable optical waveguides from poly(d,l-lactide) and derived copolymers fabricated by extrusion printing in the desired dimensions and shapes. The obtained optical waveguides propagate VIS to NIR light in air and in tissue at penetration depths of tens of centimeters. Besides, the printed waveguides have elastomeric properties at body temperature and show softness and flexibility in the range relevant for implantable devices in soft organs. Printed waveguides were able to guide light across 8 cm tissue and activate photocleavage chemical reactions in a photoresponsive hydrogel (in vitro). The simplicity and flexibility of the fiber processing method and the optical and mechanical performance of the obtained waveguides exemplify how rational study of medically approved biomaterials can lead to useful inks for printing cost-effective and flexible optical components for potential use in medical contexts.

A solid-to-hollow evolution in macroscopic structure is challenging in synthetic materials. Herein we report a fundamentally new strategy for guiding macroscopic, unidirectional shape-evolution of materials without compromising the material’s integrity, based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. We demonstrate this concept by using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling-shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects including spheres, helix tubes, and cubes with different diameters, for different applications.

Abstract Optogenetics and photonic technologies are changing the future of medicine. To implement light-based therapies in the clinic, patient-friendly devices that can deliver light inside the body while offering tunable properties and compatibility with soft tissues are needed. Here extrusion printing of degradable, hydrogel-based optical waveguides with optical losses as low as 0.1 dB cm−1 at visible wavelengths is described. Core-only and core-cladding fibers are printed at room temperature from polyethylene glycol (PEG)-based and PEG/Pluronic precursors, and cured by in situ photopolymerization. The obtained waveguides are flexible, with mechanical properties tunable within a tissue-compatible range. Degradation times are also tunable by adjusting the molar mass of the diacrylate gel precursors, which are synthesized by linking PEG diacrylate (PEGDA) with varying proportions of DL-dithiothreitol (DTT). The printed waveguides are used to activate photochemical and optogenetic processes in close-to-physiological environments. Light-triggered migration of cells in a photoresponsive 3D hydrogel and drug release from an optogenetically-engineered living material by delivering light across >5 cm of muscle tissue are demonstrated. These results quantify the in vitro performance, and reflect the potential of the printed degradable fibers for in vivo and clinical applications.

In this paper we explore the printability of reversible networks formed by catechol functionalized PEG solutions and metal cations (Al3+, Fe3+ or V3+). The printability and shape fidelity were dependent on the ink composition (metal ion type, pH, PEG molecular weight) and printing parameters (extrusion pressure and printing speed). The relaxation time, recovery rate and viscosity of the inks were analyzed in rheology studies and correlated with thermodynamic and ligand exchange kinetic constants of the dynamic bonds and the printing performance (i.e. shape fidelity of the printed structures). The relevance of the relaxation time and ligand exchange kinetics for printability was demonstrated. Cells seeded on the materials crosslinked with Al3+, Fe3+ ions were viable and revealed well-spread morphologies during 7 day culture, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D bioprinting, and enables straightforward adjustment of the printable formulation to meet application-specific needs.

Light-responsive hydrogels are useful platforms to study cellular responses. Current photosensitive motifs need UV light to be activated, which is intrinsically cytotoxic and has a low penetration depth in tissues. Herein we describe a strategy for near-infrared (NIR) controlled activation of cellular processes (3D cell spreading and angiogenesis) by embedding upconverting nanoparticles (UCNPs) in a hydrogel modified with light-activatable cell adhesive motifs. The UCNPs can convert NIR light (974 nm) into local UV emission and activate photochemical reactions on-demand. Such optoregulation is spatially controllable, dose-dependent and can be performed at different timepoints of the cell culture without appreciable photodamage of the cells. HUVEC cells embedded in this hydrogel can form vascular networks at predefined geometries determined by the irradiation pattern. The penetration depth of NIR light enabled activation of the angiogenesis response through skin tissue with a thickness of 2.5 mm. Our strategy opens a new avenue for 4D cell cultures, with the potential to be extended to dynamically manipulate cell–matrix interactions and derived cellular processes in vivo.

Cooperative action of biochemical and biomechanical signals regulates the interactions between cells and the supporting matrix in natural tissues. Herein, we describe a hydrogel for 4D cell culture which allows user-defined stiffening of the cellular environment and presentation of bioadhesive cues in an orthogonal manner using light of different wavelengths. Stiffening of the gel is initiated by VIS light, while activation of the biochemical function is triggered by UV light. We demonstrate the versatility of this system by triggering, directing and/or hindering cell migration from spheroids based on photoactivated stiffening or integrin-binding to the hydrogels. This material allows in situ and independent manipulation of the physicochemical cues in the cellular microenvironment in vitro, and could eventually be extended to in vivo.

In situ forming hydrogels with catechol groups as tissue reactive functionalities are interesting bioinspired materials for tissue adhesion. Poly(ethylene glycol) (PEG)–catechol tissue glues have been intensively investigated for this purpose. Different cross-linking mechanisms (oxidative or metal complexation) and cross-linking conditions (pH, oxidant concentration, etc.) have been studied in order to optimize the curing kinetics and final cross-linking degree of the system. However, reported systems still show limited mechanical stability, as expected from a PEG network, and this fact limits their potential application to load bearing tissues. Here, we describe mechanically reinforced PEG–catechol adhesives showing excellent and tunable cohesive properties and adhesive performance to tissue in the presence of blood. We used collagen/PEG mixtures, eventually filled with hydroxyapatite nanoparticles. The composite hydrogels show far better mechanical performance than the individual components. It is noteworthy that the adhesion strength measured on skin covered with blood was >40 kPa, largely surpassing (>6 fold) the performance of cyanoacrylate, fibrin, and PEG–catechol systems. Moreover, the mechanical and interfacial properties could be easily tuned by slight changes in the composition of the glue to adapt them to the particular properties of the tissue. The reported adhesive compositions can tune and improve cohesive and adhesive properties of PEG–catechol-based tissue glues for load-bearing surgery applications