Parkington, H. C. | Search bioRxiv

bioRxiv2025

Photoinitiator-Free, Visible Light-Crosslinking Hydrogel with Tuneable Properties for 3D Bioprinting

Light-mediated crosslinking of polymers is widely employed in the preparation of hydrogels for biofabrication and tissue engineering, since photo-crosslinking enables the spatiotemporal control over the gelation processes. Nevertheless, a critical bottleneck persists: most photo-crosslinking reactions rely on the use of photo-initiator, and ultraviolet or short-visible-wavelength light activation, which suffers from potential photodamage and poor penetration. Here we present a photoinitiator-free hydrogel system based on gelatin functionalized with acrylamidylpyrene groups (Gel-Pyr) able to undergo crosslinking via visible-light-induced [2+2] cycloaddition. Gel-Pyr solution exhibits rapid gelation kinetics, tuneable mechanical properties, facile temporal control over photocrosslinking, and long-term structural stability (>30 days) in cell culture conditions. Rheological analyses reveal pronounced shear-thinning behaviour at room temperature, enabling extrusion-based 3D bioprinting of multilayered constructs with high structural fidelity. Fine strand resolution (<400 {micro}m) is achieved in bioprinted crosshatch structures, enabling sufficient nutrient diffusion for cell support. Compared with gelatin methacryloyl (GelMA), Gel-Pyr significantly reduces photocrosslinking-induced oxidative stress and apoptosis in encapsulated bone-marrow mesenchymal stem cells (BM-MSCs), supporting >80% viability over 7 days. By eliminating UV exposure and lowering free radical generation, this visible-light-responsive hydrogel platform offers a facile and cytoprotective alternative to other hydrogel systems. Table of ContentA visible light-crosslinkable, initiator-free gelatin-based hydrogel (Gel-Pyr) is developed using acrylamidylpyrene functionalization. This system enables rapid crosslinking under cytocompatible reaction conditions and offers excellent printability, tuneable mechanics, and long-term stability. Gel-Pyr supports high cell viability, reduced oxidative stress and precision bioprinting, positioning it as a promising platform for tissue engineering and in vitro biofabrication. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=178 SRC="FIGDIR/small/691472v3_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1abe2b4org.highwire.dtl.DTLVardef@1b09b5borg.highwire.dtl.DTLVardef@1a786b1org.highwire.dtl.DTLVardef@17c06b5_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Freestanding rGO electrodes with tunable porous structures for improved neural recording

Invasive neural electrodes prepared from materials with miniaturized geometrical size could improve the longevity of implants by reducing the chronic inflammatory response. Graphene-based microfibers with tunable porous structures have a large electrochemical surface area (ESA)/geometrical surface area (GSA) ratio that has been reported to possess low impedance and high charge injection capacity (CIC), yet the control of the porous structure remains to be fully investigated. In this study, we introduce wet-spun graphene-based electrodes with pores tuned by sucrose concentrations in the coagulation bath. The electrochemical properties of thermally reduced rGO were optimized by adjusting the ratio of rGO to sucrose, resulting in significantly lower impedance, higher CIC, and higher charge storage capacity (CSC) than platinum microwires. Tensile and insertion tests confirmed that optimized electrodes had sufficient strength to ensure a 100% insertion success rate with low angle shift, thus allowing precise implantation without the need for additional mechanical enhancement. Acute in-vivo recordings from the auditory cortex found low impedance benefits from the recorded amplitude of spikes, leading to an increase in the signal-to-noise ratio (SNR). Ex-vivo recordings from hippocampal brain slices demonstrate that it is possible to record and/or stimulate with graphene-based electrodes with good fidelity compared with conventional electrodes.

neuroscience↗