Technische Universität Wien

Cell-based therapies for intervertebral disc degeneration (IVDD) treatment face significant challenges, including cell damage from injection-induced shear stress and poor survival in the harsh, nutrient-depleted microenvironment of the intervertebral disc. To overcome these challenges, we developed scaffolded spheroids (S-SPH) by integrating human bone marrow-derived mesenchymal stem cell (hBMSC) spheroids (SPH) into microscaffolds (MS) produced via high-resolution 3D printing, thereby forming injectable tissue-building blocks. We optimized cell seeding density (∼2000 cells/spheroid) and MS fabrication parameters and induced nucleus pulposus (NP)-like differentiation using growth differentiation factor-5 (GDF5) under both normoxic and hypoxic, low-glucose conditions mimicking a healthy in vivo-like environment. S-SPH maintained high cell viability and produced abundant extracellular matrix under both culture conditions. They also upregulated key NP markers, including aggrecan (ACAN), keratin-18 (KRT18), and hypoxia-inducible factor-1α (HIF1α), which indicated successful NP-like differentiation. They also exhibited improved compressive properties approaching those of native human IVD and retained structural integrity and cell viability following injection through a 26G needle. When differentiated into an NP-like phenotype, S-SPH fused and retained a high viability upon injection in vitro. These results demonstrate that S-SPH provide a promising in vitro strategy for NP regeneration, warranting further preclinical evaluation for IVDD therapy.

Single-atom sites (SASs) and their electrocatalysts offer outstanding catalytic activity and metal efficiency. Metal-organic frameworks (MOFs), with their tunable and multifunctional architectures, serve as ideal precursors for SASs, enabling atomic-level dispersion. However, current research often overlooks critical ambiguities in SAS definitions, intrinsic limitations, and characterization reliability. Moreover, prevalent destructive treatments, such as pyrolysis or sulfidation, inevitably compromise framework integrity, raising concerns regarding the trade-off between structural designability and conductivity. Accordingly, this Mini-Review critically revisits MOF-derived SASs by scrutinizing synthesis limitations and emphasizing the quantitative assessment of atomic utilization efficiency. Representative examples of emerging framework-retaining strategies, including ligand and defect engineering, are discussed to illustrate opportunities for preserving MOF advantages. Finally, future directions are proposed, focusing on dynamic structural reconstruction and operando validation to simultaneously enhance activity, stability, and scalability for practical energy conversion applications.

We present a method that combines spin resonance spectroscopy with transmission electron microscopy (TEM), enabling localized in situ detection of microwave (MW)-driven spin transitions in the specimen, utilizing the free-space electron beam of the TEM as a signal receiver. Spin state polarization is achieved via the magnetic field of the TEM's polepiece, while a custom-designed microresonator integrated into a TEM sample holder delivers continuous wave MW excitation at GHz frequencies. At resonance, the MW field drives spin transitions that produce a dynamic, precessional magnetic field around the specimen, inducing a deflection of the free-space electron beam. Phase-locked detection synchronized to the MW driving fields enables the isolation of spin precession contributions to the electron beam deflection. The presented technique offers a pathway for the in situ exploration of spin excitations at the nanoscale.