High-throughput and rapid serology assays to detect the antibody response specific to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) in human blood samples are urgently required to improve our understanding of the effects of COVID-19 across the world. Short-term applications include rapid case identification and contact tracing to limit viral spread, while population screening to determine the extent of viral infection across communities is a longer-term need. Assays developed to address these needs should match the ASSURED criteria. We have identified agglutination tests based on the commonly employed blood typing methods as a viable option. These blood typing tests are employed in hospitals worldwide, are high-throughput, fast (10–30 min), and automated in most cases. Herein, we describe the application of agglutination assays to SARS-CoV-2 serology testing by combining column agglutination testing with peptide–antibody bioconjugates, which facilitate red cell cross-linking only in the presence of plasma containing antibodies against SARS-CoV-2. This simple, rapid, and easily scalable approach has immediate application in SARS-CoV-2 serological testing and is a useful platform for assay development beyond the COVID-19 pandemic.

Paper can be used as an alternative blood grouping diagnostic tool for selected blood group phenotypes.

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The gel test is the most prevalent method for the forward and reverse blood typing tests. It relies on the controlled centrifugation of red blood cells (RBCs) and antibodies through a gel column. This noncontinuous matrix is currently based on microbeads that often lack sensitivity. For the first time, nanocellulose hydrogel is demonstrated as a sustainable and reliable medium for gel-based blood typing diagnostics. Gels with a minimum of 0.3 wt % TEMPO-oxidized cellulose nanofibers (0.92 mmol/g of carboxyl content) separate agglutinated and individual RBCs in the forward test. The addition of glycine is able to balance the osmotic pressure and reduce hemolysis to 5%, while retaining the electrostatic repulsion responsible for the gel network structure and its rheological properties. For the reverse typing, cellulose nanofibers are chemically cross-linked with hexamethylenediamine (HMDA), increasing the gel yield point 8-fold. Sodium chloride is added to achieve the osmolality found in the human plasma and limit cell lysis to 15%, without affecting the gel colloidal stability. Nanocellulose hydrogel constitutes a performant, low cost, and green soft material, providing clear and well-defined results for both blood grouping tests.

This work reports the fabrication of biocompatible and pH‐sensitive hybrid polydopamine/bovine serum albumin/calcium carbonate (PDA/BSA/CaCO3) particles via a rapid precipitation method. These hybrid particles generate hyperechogenic carbon dioxide bubbles upon exposure to low pH environments, making them ideal as a contrast agent and detector for tumor cells. This study also highlights the application of red blood cell membrane (RBC)‐derived membranes as a biomimetic coating for PDA/BSA/CaCO3 hybrid particles in order to modulate protein corona formation, a natural physiological response that alters tailored properties of most nanomaterials that are administered systemically. Results of this work demonstrate that the RBC membrane‐coated hybrid particles are ideal for a wide range of biomedical applications, such as noninvasive multimodal imaging, photothermal and photodynamic therapy, and “personalized” drug delivery systems.