Biofabrication of a Functional Tubular Construct from Tissue Spheroids Using Magnetoacoustic Levitational Directed Assembly.

In traditional tissue engineering, synthetic or natural scaffolds are usually used as removable temporal support, which involves some biotechnology limitations. The concept of "scaffield" approach utilizing the physical fields instead of biomaterial scaffold has been proposed recently. In particular, a combination of intense magnetic and acoustic fields can enable rapid levitational bioassembly of complex-shaped 3D tissue constructs from tissue spheroids at low concentration of paramagnetic agent (gadolinium salt) in the medium. In the current study, the tissue spheroids from human bladder smooth muscle cells (myospheres) are used as building blocks for assembling the tubular 3D constructs. Levitational assembly is accomplished at low concentrations of gadolinium salts in the high magnetic field at 9.5 T. The biofabricated smooth muscle constructs demonstrate contraction after the addition of vasoconstrictive agent endothelin-1. Thus, hybrid magnetoacoustic levitational bioassembly is considered as a new technology platform in the emerging field of formative biofabrication. This novel technology of scaffold-free, nozzle-free, and label-free bioassembly opens a unique opportunity for rapid biofabrication of 3D tissue and organ constructs with complex geometry.

Acoustic Nonlinearity as a Mechanism for Liquid Drop Explosions in Drop-chain Fountains Generated by a Focused Ultrasound Beam.

Ultrasonic atomization has been used in air humidifiers and is also involved in therapeutic applications of intense ultrasound such as boiling histotripsy. An as-yet unexplained phenomenon occurs when a focused ultrasound beam in water creates an acoustic fountain in the form of a drop chain, which explodes in less than a millisecond. In the present paper, we seek to develop a nonlinear theory to explain this phenomenon. We hypothesize that standing wave harmonics are generated inside the water drops due to acoustic nonlinearities, which, along with localized heat deposition in the drop center, may generate a superheated vapor bubble that causes the explosion.