3D puzzle-inspired construction of large and complex organ structures for tissue engineering.

3D printing as a powerful technology enables the fabrication of organ structures with a programmed geometry, but it is usually difficult to produce large-size tissues due to the limited working space of the 3D printer and the instability of bath or ink materials during long printing sessions. Moreover, most printing only allows preparation with a single ink, while a real organ generally consists of multiple materials. Inspired by the 3D puzzle toy, we developed a "building block-based printing" strategy, through which the preparation of 3D tissues can be realized by assembling 3D-printed "small and simple" bio-blocks into "large and complex" bioproducts. The structures that are difficult to print by conventional 3D printing such as a picture puzzle consisting of different materials and colors, a collagen "soccer" with a hollow yet closed structure, and even a full-size human heart model are successfully prepared. The 3D puzzle-inspired preparation strategy also allows for a reasonable combination of various cells in a specified order, facilitating investigation into the interaction between different kinds of cells. This strategy opens an alternative path for preparing organ structures with multiple materials, large size and complex geometry for tissue engineering applications.

3D Printing of Collagen Scaffold with Enhanced Resolution in a Citrate-Modulated Gellan Gum Microgel Bath.

3D printing in a microgel-based supporting bath enables the construction of complex structures with soft and watery biomaterials but the low print resolution is usually an obstacle to its practical application in tissue engineering. Herein, high-resolution printing of a 3D collagen organ scaffold is realized by using an engineered Gellan gum (GG) microgel bath containing trisodium citrate (TSC). The introduction of TSC into the bath system not only mitigates the aggregation of GG microgels, leading to a more homogeneous bath morphology but also suppresses the diffusion of the collagen ink in the bath due to the dehydration effect of TSC, both of which contribute to the improvement of print resolution. 3D collagen organ structures such as hand, ear, and heart are successfully constructed with high shape fidelity in the developed bath. After printing, the GG and TSC can be easily removed by washing with water, and the obtained collagen product exhibits good cell affinity in a tissue scaffold application. This work offers an easy-to-operate strategy for developing a microgel bath for high-resolution printing of collagen, providing an alternative path to in vitro 3D organ construction.

Resolution of 3D bioprinting inside bulk gel and granular gel baths.

Three-dimensional (3D) bioprinting has rapidly developed in the last decade, playing an increasingly important role in applications including pharmacokinetics research, tissue engineering, and organ regeneration. As a cutting-edge technology in 3D printing, gel bath-supported 3D bioprinting enables the freeform construction of complex structures with soft and water-containing materials, facilitating the in vitro fabrication of live tissue or organ models. To realize in vivo-like organs or tissues in terms of biological functions and complex structures by 3D printing, high resolution and fidelity are prerequisites. Although a wide range of gel matrices have recently been developed as supporting materials, the effect of bath properties and printing parameters on the print resolution is still not clearly understood. This review systematically introduces the decisive factors for resolution in both bulk gel bath systems and granular microgel bath systems, providing guidelines for high-resolution 3D bioprinting based on bath properties and printing parameters.

Superfast flow reactor derived from the used cigarette filter for the degradation of pollutants in water.

Developing high value-added products from the waste materials is highly promising from the perspective of environmental protection and resource recovery. Herein, the used cigarette filter was recycled to prepare the flow reactor via a clean and facile strategy. A continuous-flow reduction method was adopted to produce the gold nanoparticles on deacetylated cigarette filter without any extra chemical modifier, reductant or surfactant. The obtained filter was applied as a continuous-flow reactor and showed a high permeability and ultrafast flow catalytic ability. The permeability coefficient of the reactor was about 1.4 × 10-10 m2. This work provided a clean method to covert the waste cigarette filter to useful flow reactor with the relatively simple steps, and the product had a potential for the fast reduction of 4-nitrophenol and dyes including methyl blue and methylene orange.

Dual roles of cellulose monolith in the continuous-flow generation and support of gold nanoparticles for green catalyst.

Monolithic flow reactors are widely applied in numerous reactions due to its high efficiency and good reusability, but the green and efficient fabrication of monolithic flow catalytic system is still a challenge. Herein, the cellulose monolith prepared using a facile temperature-induced phase separation method was utilized to generate and immobilize the gold nanoparticles by a continuous-flow strategy, in which the cellulose monolith served as both reducing agent and supporting material. This process was conducted at room temperature and avoided the tedious surface modification of cellulose. The obtained cellulose-Au monolith can be directly applied as a green flow reactor in both water and organic solvents, and exhibited superior catalytic efficiency and good stability. This work provides a highly efficient, scalable and sustainable strategy for developing green catalytic system based on environmentally friendly cellulose monolith materials.

Monolithic cellulose supported metal nanoparticles as green flow reactor with high catalytic efficiency.

A highly effective, stable and reusable flow microreactor was developed by utilizing the environmentally sustainable porous monolithic cellulose based on a facile temperature induced phase separation (TIPS) method. The obtained microreator could be applied to efficiently and continuously catalysing the reduction reaction of 4-nitrophenol (an important reaction in water treatment) without any post-treatment or regeneration of catalysts. Moreover, the monolith overcame the brittleness of the crystalline cellulose and showed a good mechanical resilience, suggesting a great potential for the practical application in severe environment. Compared with previous reported Pd supported catalytic systems, this microreactor exhibited extremely high catalytic efficiency (turnover frequency, TOF = 4660 h-1, almost 4 times higher than that of cellulose nanocrystals supported catalyst) and long-term stability. This work provided a new strategy to construct highly effective and reusable metal NPs involved catalytic system by utilizing biodegradable cellulose materials.