Microrobot with Gyroid Surface and Gold Nanostar for High Drug Loading and Near-Infrared-Triggered Chemo-Photothermal Therapy.

The use of untethered microrobots for precise synergistic anticancer drug delivery and controlled release has attracted attention over the past decade. A high surface area of the microrobot is desirable to achieve greater therapeutic effect by increasing the drug load. Therefore, various nano- or microporous microrobot structures have been developed to load more drugs. However, as most porous structures are not interconnected deep inside, the drug-loading efficiency may be reduced. Here, we propose a magnetically guided helical microrobot with a Gyroid surface for high drug-loading efficiency and precise drug delivery. All spaces inside the proposed microrobot are interconnected, thereby enabling drug loading deep inside the structure. Moreover, we introduce gold nanostars on the microrobot structure for near-infrared-induced photothermal therapy and triggering drug release. The results of this study encourage further exploration of a high loading efficiency in cell-based therapeutics, such as stem cells or immune cells, for microrobot-based drug-delivery systems.

Three-dimensional bioprinting of mesenchymal stem cells using an osteoinductive bioink containing alginate and BMP-2-loaded PLGA nanoparticles for bone tissue engineering.

Hydrogels mimicking the physicochemical properties of the native extracellular matrix have attracted great attention as bioinks for three-dimensional (3D) bioprinting in tissue engineering applications. Alginate is a widely used bioink with beneficial properties of fast gelation and biocompatibility; however, bioprinting using alginate-based bioinks has several limitations, such as poor printability, structural instability, and limited biological activities. To address these issues, we formulated various bioinks using bone morphogenetic protein-2 (BMP-2)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles and alginate for mesenchymal stem cell (MSC) printing and induction of osteogenic differentiation. Incorporation of PLGA nanoparticles into alginate could enhance the mechanical properties and printability of the bioink. In particular, Alg/NPN30 (30 mg/mL PLGA nanoparticles and 3% w/v alginate) was most suitable for 3D printing with respect to printability and stability. BMP-2-loaded PLGA nanoparticles (NPBMP-2) displayed sustained in vitro release of BMP-2 for up to two weeks. Further in vitro studies indicated that bioinks composed of alginate and NPBMP-2 significantly induced osteogenesis of the MSCs compared with other controls, evidenced by enhanced calcium deposition, alkaline phosphatase activity, and gene expression of osteogenic markers. Our novel bioink consisting of widely used biocompatible components displays good printability, stability, and osteogenic inductivity, and holds strong potential for cell printing and bone tissue engineering applications.

An osteogenic bioink composed of alginate, cellulose nanofibrils, and polydopamine nanoparticles for 3D bioprinting and bone tissue engineering.

Bioprinting is an emerging technology for manufacturing cell-laden three-dimensional (3D) scaffolds, which are used to fabricate complex 3D constructs and provide specific microenvironments for supporting cell growth and differentiation. The development of bioinks with appropriate printability and specific bioactivities is crucial for bioprinting and tissue engineering applications, including bone tissue regeneration. Therefore, to produce functional bioinks for osteoblast printing and bone tissue formation, we formulated various nanocomposite hydrogel-based bioinks using natural and biocompatible biomaterials (i.e., alginate, tempo-oxidized cellulose nanofibrils (TOCNF), and polydopamine nanoparticles (PDANPs)). Rheological studies and printability tests revealed that bioinks containing 1.5% alginate and 1.5% TOCNF in the presence or absence of PDANP (0.5%) are suitable for 3D printing. Furthermore, in vitro studies of 3D-printed osteoblast-laden scaffolds indicated that the 0.5% PDANP-incorporated bioink induced significant osteogenesis. Overall, the bioink consisting of alginate, TOCNF, and PDANPs exhibited excellent printability and bioactivity (i.e., osteogenesis).