In situ editing of tumour cell membranes induces aggregation and capture of PD-L1 membrane proteins for enhanced cancer immunotherapy

Systematic Comparison of Commercial Uranyl-Alternative Stains for Negative- and Positive-Staining Transmission Electron Microscopy of Organic Specimens

Negative- and positive-staining transmission electron microscopy (ns/psTEM) is a cornerstone of research and diagnostics, enabling nanometer-resolution analysis of organic specimens from nanoparticles to cells without requiring costly cryo-equipment. For nearly 70 years, uranyl salts like uranyl acetate (UA) have been the gold-standard ns/psTEM-stains. However, mounting safety concerns due to their high toxicity and radioactivity have led to stricter regulations and expensive licensing requirements. Consequently, there is an urgent global demand for safer, more sustainable stains that deliver uranyl-comparable, high-quality ns/psTEM. Here, the commercially available stain-alternatives UranyLess, UAR, UA-Zero, PTA, STAIN 77, Nano-W, NanoVan, and lead citrate are systematically assessed against UA. The stains are evaluated regarding their contrast, resolution, stain-distribution, and ease-of-use in ns/psTEM across a diverse sample set, including polymethylmethacrylate-nanoplastics, phosphatidylcholine-liposomes, Influenza-A viruses, globular ferritin, fibrillar pyruvate kinase amyloids, and human lung-carcinoma cell-sections. It is shown that for this variety of samples, a ready-to-use uranyl-alternative is commercially available with comparable or even superior ns/psTEM-performance to UA using an efficient staining-protocol. Furthermore, the GUIDE4U tool is developed for the fast identification of the appropriate uranyl-replacements for each sample of interest, saving ns/psTEM-users time and costs while ensuring excellent staining results for ultrastructural analysis, thereby further catalyzing the use of safer stains.

In Situ Self-Assembly of Artificial Topological Nanostructures Enhances In Vivo Efficacy of PCSK9 Inhibitory Peptides

Optimizing the stability and affinity of peptides in vivo is critical for their development as alternatives to approved monoclonal antibodies. In recent years, efforts in academia and industry have focused on modifying Pep2-8, a classical antagonistic peptide targeting proprotein convertase subtilisin/kexin type 9 (PCSK9), to enhance its specificity and affinity. However, developing effective PCSK9 inhibitory peptides remains challenging, especially given the limited examples of their successful in vivo applications. Here, we designed transformable inhibitory peptide (TIP) against PCSK9 based on the modular structure of Pep2-8. Upon encountering PCSK9, TIP undergoes in situ self-assembly at the epidermal growth factor-like domain A (EGF-A) binding domain of PCSK9 to form artificial topological nanostructures (ATNs). The ATNs not only enhance peptide stability and prolong in vivo retention time but also strengthen PCSK9 binding through multivalent synergistic effects. We demonstrate that compared to Pep2-8, TIP forms ATNs which increasing its binding affinity for PCSK9 by approximately 18.7-fold in vitro. In high-fat diet mouse models, TIP significantly increase hepatic LDLR levels (2.0-fold) and reduced LDL-C and TC levels. We envision that the in situ formation of ATNs by peptides enhances in vivo stability and affinity, which offering an approach for development as antibody alternatives in clinical.