Additive manufacturing (AM) has become a key fabrication strategy in tissue engineering, enabling the construction of biodegradable scaffolds with complex geometries. Among various AM techniques, photopolymerization-based approaches such as stereolithography (SLA) and digital light processing (DLP) offer significant advantages due to their high spatial resolution and room-temperature processing capabilities [1] Scaffolds fabricated via these techniques not only allow for the in situ incorporation of thermosensitive drugs or cells, but also more accurately replicate the microarchitecture of native tissues, enabling patient-specific customization. However, achieving a balance between mechanical integrity and tissue compliance remains a major challenge. Hydrogel-based systems, while highly biocompatible, often lack the strength necessary to maintain structural stability [[2], [3], [4]] In contrast, synthetic polyesters-based systems such as poly(lactide), [5] and poly(caprolactone) [6,7] exhibit excessive rigidity, resulting in mechanical mismatch with soft tissues and stress concentration at the tissue–material interface. Recent studies have demonstrated the feasibility of DLP printing using PLCL-based resins for tissue engineering, but also revealed key limitations such as high resin viscosity requiring reactive diluents and inadequate elongation at break (<120%) [8,9] Thus, the development of photocurable elastomeric materials that integrate low stiffness, high stretchability, and solvent-free DLP compatibility remains a critical challenge in soft tissue scaffold design.

Thiol–ene click chemistry provides a promising route, offering homogeneous network formation, tunable mechanical properties, rapid and regioselective photopolymerization, and favorable biocompatibility and degradability [6,10,11] Thijssen et al. reported 3D-printable PCL-based networks formed via thiol–ene crosslinking, achieving enhanced elasticity and print fidelity; [6,7] Arreguín-Campos et al. developed PEG-SH hydrogels via thiol–ene photopolymerization for DLP printing; [12] and Fan et al. demonstrated the SLA-based fabrication of PEG-SH scaffolds incorporating decellularized placenta powder, aiming to enhance tissue-specific bioactivity [13] Nevertheless, few of these thiol–ene-based designs have been tailored for soft tissue scaffolds requiring low modulus and high extensibility. Such mechanical limitations are particularly critical in perivascular scaffold applications, where compliance mismatch exacerbates neointimal hyperplasia (NIH), a key driver of vascular access dysfunction [[14], [15], [16], [17]]

Arteriovenous fistula (AVF) [18] and vein bypass grafting [19,20] are widely used surgical procedures for establishing vascular access or restoring blood flow. However, only 50–70% of AVFs remain functional within the first year, [21,22] and up to 40% of vein grafts fail within a few years after surgery [23,24] These failures are closely associated with inflammation, oxidative stress, hypoxia, and disturbed hemodynamics—such as low wall shear stress and flow turbulence at the anastomotic site—all of which contribute to the development of NIH [[25], [26], [27], [28], [29]] Under the stimulation of inflammatory signals and growth factors, vascular smooth muscle cells (VSMCs) undergo phenotypic switching into a dedifferentiated, proliferative state [30,31] These activated cells migrate into the intima and accumulate excessively, leading to neointimal thickening and luminal narrowing, which can ultimately cause graft thrombosis or failure [32,33] The causal relationships between these pathogenic factors and AVF failure have been further validated in both small and large animal models. In rodents, disturbed flow, oxidative stress, and inflammation have been shown to drive endothelial loss and NIH formation [34,35] Complementary findings in large-animal models further demonstrated that modulating perivascular inflammation, endothelial-to-mesenchymal transition (EndMT), and hemodynamic stress can promote favorable vascular remodeling and reduce stenosis [[36], [37], [38]] These findings underscore the urgent need for biomaterial-based interventions that can modulate the local microenvironment and hemodynamics to prevent NIH and improve long-term graft outcomes.

In response to these challenges, perivascular scaffolds have shown promise in improving long-term patency by providing mechanical support and modulating the local microenvironment [[39], [40], [41], [42]] Clinical devices such as VEST [43] have demonstrated that, compared to the no-stent group, perfect patency increased by approximately 33% at 1 year and 29% at 4.5 years. Similarly, VasQ studies showed an 11–26% improvement in patency at 6 months, a reduction in first intervention time from 81 days to 56 days, and a decrease in annual intervention rates from 1.80 to 1.07 [44,45] Despite their clinical success, both devices are composed of non-degradable metallic materials, which raised concerns about long-term biocompatibility, chronic inflammation, and incompatibility with drug delivery strategies. In contrast, biodegradable wraps such as electrospun poly(caprolactone) (PCL) exhibit good biocompatibility, [[46], [47], [48]] but their tubular geometry provides limited radial support at the anastomotic site and their slow degradation may restrict early venous remodeling, a critical phase in AVF maturation [49] Injectable hydrogels offer favorable conformability and drug delivery potential, but lack the mechanical integrity required to maintain scaffold architecture [50,51]. Given the anatomical variability among patients and the complex geometry of AVF sites, customizable scaffolds tailored to individual vascular anatomy are highly desirable. These limitations underscore the need for a biodegradable, mechanically compliant perivascular scaffold that can be precisely customized via 3D printing to conform to patient-specific vascular geometries, while simultaneously supporting localized therapeutic delivery.

In this study, we developed a photopolymerizable biodegradable elastomer by modifying poly(L-lactide-co-ε-caprolactone) (PLCL) with alkene groups, enabling light-induced crosslinking. When combined with tetra-functional thiol pentaerythritol tetra(3-mercaptopropionate) (PETA-4SH), the resulting A-PLCL/4SH resin formed an elastic, degradable network with mechanical properties suitable for soft tissue applications and high-resolution printability via DLP 3D printing. To demonstrate its application, we constructed a dual-layered perivascular scaffold (BioShell), integrating a DLP-printed A-PLCL/4SH outer shell (BioCore) with an injectable SilMA hydrogel inner layer. This bilayer design decoupled mechanical and therapeutic functions, enabled structural support and localized drug delivery. Using an AVF model as a representative case, the BioShell scaffold preserved anastomotic geometry, promoted outward remodeling, and significantly reduced NIH, highlighting its potential for vascular reconstruction and other soft tissue engineering applications.