3D bioprinting technology displays many advantages for tissue engineering applications, but its utilization is limited by veryfew bioinks available for biofabrication. In this study, a novel type of bioink, which includes three methacryloyl modifiedmannans, was introduced to 3D bioprinting for tissue engineering applications. Yeast mannan (YM) was modified by reactingwith methacrylate anhydride (MA) at different concentrations, and three YM derived bioinks were obtained, which weretermed as YM-MA-1, YM-MA-2 and YM-MA-3 and were distinguished with different adjusted methacrylation degrees. TheYM derived bioink displayed an advantage that the mechanical properties of its photo-cured hydrogels can be enhanced withits methacrylation degree. Hence, YM derived bioinks are fitted for the mechanical requirements of most soft tissueengineering, including cartilage tissue engineering. By selecting chondrocytes as the testing cells, well cytocompatibility of YM-MA-1, YM-MA-2 had been confirmed by CCK-8 method. Following photo-crosslinking and implantation into SD rats for 4 weeks, the in vivo biocompatibility of the YM-MA-2 hydrogel is acceptable for tissue engineering applications. Hence, YM-MA-2 was chosen for 3D bioprinting. Our data demonstrated that hydrogel products with designed shape and living chondrocytes have been printed by applying YM-MA-2 as the bioink carrying chondrocytes. After the YM-MA-2 hydrogel with encapsulated chondrocytes was implanted subcutaneously in nude mice for 2 weeks, GAG and COLII secretion was confirmed by histological staining in YM-MA-2-H, indicating that the YM derived bioink can be potentially applied to tissue engineering by employing a 3D printer of stereolithography.
The high cost of biomass harvesting by centrifugation and high safety risks of collected algal biomass by chemical flocculation are serious problems jeopardizing the industrial implementation of microalgae bio-products. Recently, microalgae immobilization is regarded as a promising technology with the potential of lowering biomass production cost and ensuring biomass safety in the industry. Therefore, microalgal biofilms, an effective and affordable way to immobilize algal cells, are emerging into the limelight. This paper summarizes the progress achieved in biofilm system design and biofilm formation mechanisms. Newly designed algal biofilm systems are compared to demonstrate their advantages and weaknesses. Besides, mechanisms associated with the two steps -initial attachment of microalgae and biofilm thickeningof biofilm formation are discussed in this paper. Factors such as substratum material, algal strain and operational parameters, which could impact the formation and operation of algal biofilm, are demonstrated. Efforts devoted to the industrial application of algal biofilm to treat wastewater are discussed. The biotechnology of microalgal biofilm is currently at the critical stage of developing from fundamental research to industrial implementation. Undeniably, there are still many problems that limit the wide use of algal biofilm for biomass production and wastewater treatment. In this paper, we present some potential solutions to current problems and discuss the development trends of algal biofilm in the foreseeable future. It is expected that by addressing current problems microalgal biofilm will be widely used at the industrial scale.
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