Photocurable monoolein-based injectable system for in situ forming gel applications

Injectable in situ forming gels are promising for biomedical applications requiring minimally invasive delivery and localized structural stability. Lipid-based systems are particularly attractive due to their ability to self-assemble into ordered nanostructures. Here, we report a photocurable monoolein (MO)-poly(ethylene glycol) diacrylate (PEGDA) system that integrates lipid self-assembly with ultraviolet (UV) curing to yield injectable, in situ forming nanostructured gels. Small-angle X-ray scattering (SAXS) analysis revealed that hydration-induced self-assembly of monoolein is preserved within the photocurable matrix, producing lamellar, cubic, and hexagonal phases depending on composition and water content. Liquid-in-liquid 3D printing demonstrated that monoolein precursors spontaneously form nanostructured gels upon injection into a water bath, while subsequent UV curing stabilizes the printed architecture and enables retrieval of complex constructs. Mechanical testing showed that monoolein to PEGDA ratios control compressive moduli, with lower monoolein concentrations producing stiffer gels and higher concentrations yielding more flexible constructs. Rheological characterization showed Newtonian behavior before hydration and shear-thinning behavior of the samples after hydration. Swelling and biodegradation assays confirmed fluid uptake and enzymatic degradation under physiological conditions, indicating potential for controlled disintegration in vivo. Together, these findings establish a versatile injectable monoolein-PEGDA platform that combines lipid nanostructure with photocurable stability, enabling next-generation applications in drug delivery, tissue engineering, and localized therapeutic depots.