## 1 Introduction  
Many pathologies affecting retinal tissue lead to irreversible vision impairments due to the loss of photoreceptors. Regenerative medicine represents a viable strategy for treating these conditions by replacing dead photoreceptors with healthy ones. Research advancements in cell therapies have shown promise in restoring retinal cells and retinal function [1]. For instance, the use of induced pluripotent stem cells (iPSCs) to generate a functional retinal pigment epithelium has demonstrated potential in clinical trials [2]. Yet, significant hurdles, including the long-term survival and integration of transplanted cells, remain [3]. Moreover, photoreceptors are difficult to cultivate and maintain in vitro [4]. To tackle these issues, cells can be transplanted using a scaffold, allowing for the delivery of an organized and functional cell layer that integrates better with the host tissue compared with cell injection. Yet, few studies on the fabrication of photoreceptor scaffolds have been reported in the literature. Most of these studies focused on creating scaffolds with an architecture that guides cell differentiation and orientation, which is crucial for fulfilling the light-sensing function [5]. [PERSON] et al. proved that the presence of microtopography positively affected cell attachment and induced the differentiation of retinal progenitor cells [6]. Similarly, [PERSON] et al. showed that a 3D micropatterned scaffold can guide the attachment and the differentiation of pluripotent stem cells into photoreceptors [7]. Besidestopographical cues, scaffold stiffness has also been identified as a key parameter for driving cells to differentiate into photoreceptors and for maintaining lineage specification [8; 9]. Therefore, selecting suitable substrate materials and fabrication techniques is crucial for recapitulating both the architecture and properties of the in vivo photoreceptor environment [8]. Current substrates fail to mimic both the architecture and the stiffness of the native milieu, thus hindering progress in retinal regenerative approaches [7; 10]. Hence, recreating the environment of photoreceptors in vitro still represents an engineering challenge. Recently, 3D bioprinting has been suggested as a promising technique to fabricate scaffolds for photoreceptors, as it allows 3D porous architectures with precise control over pore size, geometry, and cell spatial distribution to be obtained without significantly affecting cell viability [5; 11; 12; 13]. Different bioprinting technologies have been developed and employed according to the application [14]. For instance, [PERSON] et al. demonstrated the feasibility of fabricating a 3D in vitro retina model using an inkjet-based bioprinter [12]. However, with this approach, cells had to be printed in culture medium to avoid clogging issues. So, the native stiffness could not be matched. Among the bioprinting approaches, pneumatic-driven extrusion-based bioprinting is one of the most common due to its versatility in printing a wide range of bioinks and its ease of use [15]. Additionally, it enables the production of clinically relevant constructs, in terms of size, within a reasonable time. Bioinks employed in extrusion bioprinting must display shear-thinning behavior to enable successful extrusion and printing while preserving the structure given by the printing process [16]. [PERSON] et al. used an alginate-pluronic bioink that included a retinoblastoma-derived cell line to replicate the photoreceptor layer in a 3D in vitro model [17]. They evaluated the impact of two different printing patterns on cell morphology; however, the stiffness of the bioink was not investigated. Hence, to date, a bioink capable of meeting the requirements for extrusion-based bioprinting and simultaneously accurately replicating retinal properties has yet to be developed [11; 18].