Organ-on-a-chip technology has been used in testing small-molecule drugs for screening potential therapeutics and regulatory protocols. The technology is expected to boost the development of novel therapies and accelerate the discovery of drug combinations in the coming years. This has led to the development of multi-organ-on-a-chip (MOC) for recapitulating various organs involved in the drug–body interactions. In this review, we discuss the current MOCs used in screening small-molecule drugs and then focus on the dynamic process of drug absorption, distribution, metabolism, and excretion. We also address appropriate materials used for MOCs at low cost and scale-up capacity suitable for high-performance analysis of drugs and commercial high-throughput screening platforms.

A nanoparticle is commonly referred as a particle with a diameter between one to one hundred nanometers (nm). Nanoparticles are classified into 3 main groups based on their composition which are organic (polymeric nanoparticles, micelles, dendrimers, liposomes), inorganic (metal-based, metal oxide-based, ceramic-based, quantum dots (QDs)), and carbon-based nanoparticles (graphene/graphene oxide (GO), carbon nanofibers (CNFs), carbon nanotubes (CNTs)). There have been numerous studies that used nanoparticles in bioinks to prepare tissues and organs for instance cartilage, bone, osteochondral, vascular, skin, muscle, nerve, liver and tendon. Incorporation of nanoparticles in bioinks possess many advantages such as improving mechanical and rheological properties of bioinks, enhancing biological features of bioinks through functionalization of nanoparticles, using as effective drug delivery agents, monitoring tissue regeneration, and increasing cell attachment and proliferation. Although, many promising results obtained from previous studies, still there are several drawbacks about using nanoparticles in bioinks for example accumulation of non-biodegradable nanoparticles could cause blockage in capillaries and then possibly it could prevent blood flow and eventually could cause cellular death. Another limitation of using some specific nanoparticles (e.g., silver nanoparticles (AgNPs), iron oxide-based nanoparticles, cadmium-based QDs) could be the cytotoxic effects of these nanomaterials or released ions from these nanoparticles on cells. Invention of more biocompatible nanoparticles in the near future could increase the applications of these materials in bioprinting studies. This review provides detailed information and analysis regarding the up-to-date overview on applications of nanoparticles in the structure of bioinks in bioprinting.