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A method is proposed of fabricating tubular constructs from tissue spheroids (conglomerates of cells up to 200 μm in size) in a nutrient fluid using the acoustic radiation force. The source of the acoustic field is a hollow piezoceramic cylinder with a resonant frequency of 800 kHz. Keeping the obtained structure at 37°C for 24 h fuses the spheroids into a solid tubular viable tissue construct.

Reproducible, scalable, and cost effective fabrication and versatile characterization of tissue spheroids (TS) is highly demanded by 3D bioprinting and drug discovery. Consistent geometry, defined mechanical properties, optimal viability, appropriate extracellular matrix/cell organization are required for cell aggregates aimed for application in these fields. A straightforward procedure for fabrication and systematic multiparametric characterization of TS with defined properties and uniform predictable geometry employing non-adhesive technology is suggested. Applying immortalized and primary cells, the reproducibility of spheroid generation, the strong correlation of ultimate spheroid diameter, and growth pattern with cell type and initial seeding concentration are demonstrated. Spheroids viability and mechanical properties are governed by cell derivation. In this study, a new decision procedure to apply for any cell type one starts to work with to prepare and typify TS meeting high quality standards in biofabrication and drug discovery is suggested.

We have developed a method of the terahertz (THz) solid immersion microscopy for the reflection-mode imaging of soft biological tissues. It relies on the use of the solid immersion lens (SIL), which employs the electromagnetic wave focusing into the evanescent-field volume (i.e. at a small distance behind the medium possessing high refractive index) and yields reduction in the dimensions of the THz beam caustic. We have assembled an experimental setup using a backward-wave oscillator, as a source of the continuous-wave THz radiation featuring λ= 500 μm, a Golay cell, as a detector of the THz wave intensity, and a THz SIL comprised of a wide-aperture aspherical singlet, a truncated sphere and a thin scanning windows. The truncated sphere and the scanning window are made of high-resistivity float-zone silicon and form a unitary optical element mounted in front of the object plane for the resolution enhancement. The truncated sphere is rigidly fixed, while the scanning window moves in lateral directions, allowing for handling and visualizing the soft tissues. We have applied the experimental setup for imaging of a razor blade to demonstrate the advanced 0:2λ resolution of the proposed imaging arrangement. Finally, we have performed imaging of sub-wavelength-scale tissue spheroids to highlight potential of the THz solid immersion microscopy in biology and medicine.