3D organoids using stem cells to study development and disease are now widespread. These models are powerful to mimic in vivo situations but are currently associated with high variability and low throughput. For biomedical research, platforms are thus necessary to increase reproducibility and allow high-throughput screens (HTS). Here, we introduce a microwell platform, integrated in standard culture plates, for functional HTS. Using micro-thermoforming, we form round-bottom microwell arrays from optically clear cyclic olefin polymer films, and assemble them with bottom-less 96-well plates. We show that embryonic stem cells aggregate faster and more reproducibly (centricity, circularity) as compared to a state-of-the-art microwell array. We then run a screen of a chemical library to direct differentiation into primitive endoderm (PrE) and, using on-chip high content imaging (HCI), we identify molecules, including regulators of the cAMP pathway, regulating tissue size, morphology and PrE gene activity. We propose that this platform will benefit to the systematic study of organogenesis in vitro.

Pr3+‐doped LuPO4 emits UV radiation between 225 and 280 nm, where DNA shows strong absorption bands. Therefore, a systematic study of the luminescence of Pr3+ doped LuPO4 is performed: Different doping concentrations, particles sizes, and excitation schemes (vacuum UV at 160 nm and X‐rays 50 kV, 2 mA, tungsten target) are compared. The emission spectra in the UV range depends on the excitation energy and the particle size. Microcrystalline particles (6 µm) comprising 1% Pr3+ display the highest emission intensity at 234 nm upon vacuum UV as well as X‐ray excitation. Sub‐microscale particles (20–50 nm) of LuPO4:Pr3+ (1%) show the same UV emission under X‐ray excitation as the larger particles but do not emit under vacuum UV excitation. Colloidal nanoscale particles (5 nm) do not show emission in the UV‐C range. Based on the high‐density and strong X‐ray absorption of LuPO4, the implementation of Pr3+ doped LuPO4 particles of suitable size (20–50 nm) could improve the well‐established radiation therapy. Owing to the strong absorption and low penetration depth of UV‐C radiation in biological tissue, Pr3+‐doped LuPO4 particles located directly in cancerous tumors could allow for additional treatment with cell‐damaging UV‐C radiation.

Radiation therapy is one of the primary therapeutic techniques for treating cancer, administered to nearly two-thirds of all cancer patients. Although largely effective in killing cancer cells, radiation therapy, like other forms of cancer treatment, has difficulty dealing with hypoxic regions within solid tumors. The incomplete killing of cancer cells can lead to recurrence and relapse. The research presented here is investigating the enhancement of the efficacy of radiation therapy by using scintillating nanoparticles that emit UV photons. UV photons, with wavelengths between 230 nm and 280 nm, are able to inactivate cells due to their direct interaction with DNA, causing a variety of forms of damage. UV-emitting nanoparticles will enhance the treatment in two ways: first by generating UV photons in the immediate vicinity of cancer cells, leading to direct and oxygen-independent DNA damage, and second by down-converting the applied higher energy X-rays into softer X-rays and particles that are more efficiently absorbed in the targeted tumor region. The end result will be nanoparticles with a higher efficacy in the treatment of hypoxic cells in the tumor, filling an important, unmet clinical need. Our preliminary experiments show an increase in cell death using scintillating LuPO4:Pr nanoparticles over that achieved by the primary radiation alone. This work describes the fabrication of the nanoparticles, their physical characterization, and the spectroscopic characterization of the UV emission. The work also presents in vitro results that demonstrate an enhanced efficacy of cell killing with x-rays and a low unspecific toxicity of the nanoparticles.

X-ray excitation of LaPO4:Gd3+ nanocrystals results in single-line UV emission capable of activating organic molecules and enabling new biomedical applications.