Hybrid Chitosan–BSA Bioinks for DLP Biofabrication and DLP-Assisted Molding of 3D Hydrogel Constructs with Embedded Branched Structures

Digital light processing (DLP) bioprinting enables rapid fabrication of high-resolution three-dimensional constructs, but its broader application remains limited by the availability of bioinks that combine structural stability with biological functionality. Here, we present a hybrid chitosan methacrylate–bovine serum albumin methacrylate (ChiMA–BSA-MA) bioink that integrates the structural support of methacrylated chitosan with the biologically favorable properties of methacrylated bovine serum albumin for DLP biofabrication. The hybrid formulations exhibited shear-thinning behavior, rapid photocrosslinking under 405 nm light exposure, and composition-dependent rheological and mechanical properties suitable for vat photopolymerization. Selected formulations enabled fabrication of free-standing constructs exceeding 10 mm in height while maintaining preserved microscale features. Representative complex geometries and embedded branched structures were successfully fabricated using direct DLP printing together with a complementary DLP-assisted molding strategy. Unlike many existing approaches that rely on extrusion-based bioprinting, support-bath printing, sacrificial templates, coaxial nozzles, or other multistep fabrication procedures, the proposed workflow combines direct DLP printing with a simple secondary molding step using a conventional DLP printer. Biological evaluation demonstrated sustained metabolic activity and cell viability over 14 days. Under chondrogenic differentiation conditions, RT-qPCR showed increased expression of SOX9, COL2A1, ACAN, ELN, COL10A1, and MMP13, indicating induction of chondrogenic and hypertrophy-associated marker expression. Overall, the ChiMA–BSA-MA hybrid bioink provides a versatile platform for DLP biofabrication of tissue models with embedded branched structures, expanding the range of photocurable bioinks available for advanced in vitro tissue engineering applications.