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Abstract Bioprinting of cell-laden hydrogels is a rapidly growing field in tissue engineering. The advent of digital light processing (DLP) three-dimensional (3D) bioprinting technique has revolutionized the fabrication of complex 3D structures. By adjusting light exposure, it becomes possible to control the mechanical properties of the structure, a critical factor in modulating cell activities. To better mimic cell densities in real tissues, recent progress has been made in achieving high-cell-density (HCD) printing with high resolution. However, regulating the stiffness in HCD constructs remains challenging. The large volume of cells greatly affects the light-based DLP bioprinting by causing light absorption, reflection, and scattering. Here, we introduce a neural network-based machine learning technique to predict the stiffness of cell-laden hydrogel scaffolds. Using comprehensive mechanical testing data from 3D bioprinted samples, the model was trained to deliver accurate predictions. To address the demand of working with precious and costly cell types, we employed various methods to ensure the generalizability of the model, even with limited datasets. We demonstrated a transfer learning method to achieve good performance for a precious cell type with a reduced amount of data. The chosen method outperformed many other machine learning techniques, offering a reliable and efficient solution for stiffness prediction in cell-laden scaffolds. This breakthrough paves the way for the next generation of precision bioprinting and more customized tissue engineering. 

Abstract Controllable and long‐term release remains a great challenge in current drug delivery systems. Benefiting from their efficient drug loading and painless administration, microneedles (MNs) have emerged as a promising platform for transdermal drug delivery, while they often fail to achieve long‐term tissue adhesion and controllable extended drug release. Here, 3D printing of an innovative MN patch is presented with succulent‐inspired responsive microstructures and light‐controllable long‐term release capability. The MN exhibits a reversible shrink‐swell volume change behavior in response to surrounding humidity, which enables sufficient mechanical strength for skin penetration under the shrinkage conditions and efficient long‐term adhesion when swollen in skin tissues. Moreover, the MN patch introduces a controllable long‐term drug release system, achieved through the integration of thiolated heparin (Hep‐SH) for sustained growth factor release and graphene oxide (GO) nanosheets for controlled drug release via near infrared (NIR) laser irradiation. The MN patches with growth factor loading have good biocompatibility and can promote the proliferation, migration, and proangiogenesis of endothelial cells is further demonstrated. Thus, it is believed that such flexible MN patches can be promising candidates for controllable long‐term transdermal drug delivery as well as other related tissue engineering applications. 

Abstract Wastewater treatment, particularly for persistent organic pollutants (POPs), remains a significant challenge. Although advanced oxidation processes (AOPs) currently used for treating POPs can achieve a decent efficiency, they often involve high costs and necessitate additional post‐treatment processes. Here, a jellyfish‐mimicking, multi‐functional living material encapsulating algae cells are presented, namely Algelly, created using a multi‐material digital‐light processing (DLP) bioprinting technique. The Algelly construct comprises a methacrylated alginate (AlgMA) layer designed to support algae growth, and a poly(N‐isopropylacrylamide) (PNIPAM) layer embedded with magnetic nanoparticles (MNs). The MNs enable the Algelly to respond to near‐infrared (NIR) laser for deformation and magnetic force for steering. It is demonstrated that the DLP bioprinting technique can fabricate the heterogeneous Algelly with high spatial resolution and efficiency, which supports subsequent algae proliferation and effective photosynthesis in the Algelly matrix. Moreover, the NIR‐induced thermo‐responsive deformation and magnetic steering capabilities enhance Algelly's adaptability for recycling and collection. Most importantly, Algelly demonstrates a high efficiency in degrading POPs under white light illumination. Therefore, it is believed that Algelly holds a promising potential for new applications in wastewater treatment, given its efficiency in POP decomposition and flexible location control capabilities.