Extensive burns and full-thickness skin wounds are difficult to repair. Autologous split-thickness skin graft (ASSG) is still used as the gold standard in the clinic. However, the shortage of donor skin tissues is a serious problem. A potential solution to this problem is to fabricate skin constructs using biomaterial scaffolds with or without cells. Bioprinting is being applied to address the need for skin tissues suitable for transplantation, and can lead to the development of skin equivalents for wound healing therapy. Here, we summarize strategies of bioprinting and review current advances of bioprinting of skin constructs. There will be challenges on the way of 3D bioprinting for skin regeneration, but we still believe bioprinting will be potential skills for wounds healing in the foreseeable future.

Tissue engineered conduits have great promise for bridging peripheral nerve defects by providing physical guiding and biological cues. A flexible method for integrating support cells into a conduit with desired architectures is wanted. Here, a 3D-printing technology is adopted to prepare a bio-conduit with designer structures for peripheral nerve regeneration. This bio-conduit is consisted of a cryopolymerized gelatin methacryloyl (cryoGelMA) gel cellularized with adipose-derived stem cells (ASCs). By modeling using 3D-printed “lock and key” moulds, the cryoGelMA gel is structured into conduits with different geometries, such as the designed multichannel or bifurcating and the personalized structures. The cryoGelMA conduit is degradable and could be completely degraded in 2-4 months in vivo. The cryoGelMA scaffold supports the attachment, proliferation and survival of the seeded ASCs, and up-regulates the expression of their neurotrophic factors mRNA in vitro. After implanted in a rat model, the bio-conduit is capable of supporting the re-innervation across a 10 mm sciatic nerve gap, with results close to that of the autografts in terms of functional and histological assessments. The study describes an indirect 3D-printing technology for fabricating cellularized designer conduits for peripheral nerve regeneration, and could lead to the development of future nerve bio-conduits for clinical use.

End-to-end neurorrhaphy is the most commonly used method for treating peripheral nerve injury. However, only 50% of patients can regain useful function after treating with neurorrhaphy. Here, we constructed a 3D-engineered porous conduit to promote the function recovery of the transected peripheral nerve after neurorrhaphy. The conduit that consisted of a gelatin cryogel was prepared by molding with 3D-printed moulds. Due to its porous structure and excellent mechanical properties, this conduit could be collapsed by the mechanical force and resumed its original shape after absorption of normal saline. This shape-memory property allowed a simply surgery process for installing the conduits. Moreover, the biodegradable conduit could prevent the infiltration of fibroblasts and reduce the risk of scar tissue, which could provide an advantageous environment for nerve regeneration. The efficiency of the conduits in assisting peripheral nerve regeneration after neurorrhaphy was evaluated in a rat sciatic nerve transected model. Results indicated that conduits significantly benefitted the recovery of the transected peripheral nerve after end-to-end neurorrhaphy on the static sciatic index (SSI), electrophysiological results and the re-innervation of the gastrocnemius muscle. This work demonstrates a biodegradable nerve conduit that has potentially clinical application in promoting the neurorrhaphy.

Gene therapy has great promise for glioblastoma treatment; however, it remains a great challenge to efficiently deliver genes to the brain. The incomplete resection of glioblastoma always leads to poor prognosis. Here, a 3D‐engineered conformal implant for eradicating the postsurgery residual glioblastoma is designed. This implant is constructed by 3D‐printing technology to match the tumor cavity and release an oncolytic virus‐inspired DNA nanocomplex to kill glioblastoma cells through apoptosis induction. Meanwhile, a 3D‐engineered subcutaneous glioblastoma xenograft is built to mimic the resection tumor cavity in mice. Insertion of the implant into the glioblastoma resection cavity efficiently delays tumor recurrence and significantly prolongs overall survival. This study provides a proof‐of‐concept of glioblastoma therapy using a conformal implant that releases oncolytic DNA nanocomplexs. This strategy can lead to the development of future precision therapy for eradicating postsurgery residual tumors.

Customized microneedle arrays (CMNAs) hold great promise for precise transdermal delivery in a minimally invasive manner. Currently, the fast customization of microneedle arrays remains a great challenge. Here, we show a static optical projection lithography (SOPL) technology for fast 3D printing CMNAs. In this technology, the digital light is statically projected to induce the spatial polymerization of monomer solutions, and therefore microneedle formation can be precisely controlled by the intensity distribution of the projected light. The obtained CMNAs do not have the stair-like surface and layer-by-layer structure that are associated with the common 3D-printing technologies. This method enables fast fabrication of CMNAs with designed shape, size, and distribution in seconds without mechanical motion system. Upconversion nanoparticles (UCNPs) were delivered into skin by the CMNAs, to form a personalized dot matrix for in vivo information storage. Under the irradiation of near-infrared (NIR) light, the UCNPs in skin displayed a visible dot matrix, presenting information encoded in the structure of CMNAs. This work demonstrates a SOPL technology for rapidly customizing high-quality microneedle arrays and a CMNA-mediated in vivo information storage strategy.