Recent developments in 3D printing technologies and design have been nothing short of spectacular. Parallel to this, development of bioinks has also emerged as an active research area with almost unlimited possibilities. Many bioinks have been developed for various cells types, but bioinks currently used for 3D printing still have challenges and limitations. Bioink development is significant due to two major objectives. The first objective is to provide growth- and function-supportive bioinks to the cells for their proper organization and eventual function and the second objective is to minimize the effect of printing on cell viability, without compromising the resolution shape and stability of the construct. Here, we will address the current status and challenges of bioinks for 3D printing of tissue constructs for in vitro and in vivo applications.

Microalgae have gained enormous consideration from scientific community worldwide emerging as a viable feedstock for a renewable energy source virtually being carbon neutral, high lipid content, and comparatively more advantageous to other sources of biofuels. Although microalgae are seen as a valuable source in majority part of the world for production of biofuels and bioproducts, still they are unable to accomplish sustainable large-scale algal biofuel production. Wastewater has organic and inorganic supplements required for algal growth. The coupling of microalgae with wastewater is an effective way of waste remediation and a cost-effective microalgal biofuel production. In this review article, we will primarily discuss the possibilities and current scenario regarding coupling of microalgal cultivation with biofuel production emphasizing recent progress in this area.

A controlled “green synthesis” approach to synthesize silver nanoparticles by Allium cepa and Musa acuminata plant extract has been reported. The effect of different process parameters, such as pH, temperature and time, on synthesis of Ag nanoparticles from plant extracts has been highlighted. The work reports an easy approach to control the kinetics of interaction of metal ions with reducing agents, stabilized by ammonia to achieve sub-10 nm particles with narrow size distribution. The nanoparticles have been characterized by UV–Visible spectra and TEM analysis. Excellent antimicrobial activity at extremely low concentration of the nanoparticles was observed against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Fusarium oxysporum which may allow their exploitation as a new generation nanoproduct in biomedical and agricultural applications.

Owing to the success of three-dimensional (3D) printing in biomedical applications, the latest addition to the technology is four-dimensional (4D) printing, which has gained tremendous interest since 2012. 4D printing is being considered as an upgradation and extension of 3D that includes time as a fourth dimension with the utilization of smart biomaterials, and upon the application of any external stimulus, the shape and size of the printed structure change with time. In this review, we highlight the basic techniques involved in 4D printing, the shape memory effect, and various stimuli like light, temperature, pH, etc., that cause the shape change, leading to the transformation of the structures fabricated. 4D printing using smart materials demonstrates shape memory property and their possible applications in the field of biomedicine and regenerative medicine are discussed in detail. The authors have focused on 4D printing of various tissues, with a special highlight on bone and dental tissue. Graphical abstract

Liver-associated diseases and tissue engineering approaches based on in vitro culture of functional Primary human hepatocytes (PHH) had been restricted by the rapid de-differentiation in 2D culture conditions which restricted their usability. It was proven that cells growing in 3D format can better mimic the in vivo microenvironment, and thus help in maintaining metabolic activity, phenotypic properties, and longevity of the in vitro cultures. Again, the culture method and type of cell population are also recognized as important parameters for functional maintenance of primary hepatocytes. Hepatic organoids formed by self-assembly of hepatic cells are microtissues, and were able to show long-term in vitro maintenance of hepato-specific characteristics. Thus, hepatic organoids were recognized as an effective tool for screening potential cures and modeling liver diseases effectively. The current review summarizes the importance of 3D hepatic organoid culture over other conventional 2D and 3D culture models and its applicability in Liver tissue engineering.