Magnetic purification of plasminogen from human plasma by specific lysine affinity

Integrating Metabolic Oligosaccharide Engineering and SPAAC Click Chemistry for Constructing Fibrinolytic Cell Surfaces

To effectively solve the problem of significant loss of transplanted cells caused by thrombosis during cell transplantation, this study simulates the human fibrinolytic system and combines metabolic oligosaccharide engineering with strain-promoted azide-alkyne cycloaddition (SPAAC) click chemistry to construct a cell surface with fibrinolytic activity. First, a copolymer (POL) of oligoethylene glycol methacrylate (OEGMA) and 6-amino-2-(2-methylamido)hexanoic acid (Lys) was synthesized by reversible addition-fragmentation chain transfer (RAFT) copolymerization, and the dibenzocyclooctyne (DBCO) functional group was introduced into the side chain of the copolymer through an active ester reaction, resulting in a functionalized copolymer DBCO-PEG4-POL with ε-lysine ligands. Then, azide functional groups were introduced onto the surface of HeLa model cells through metabolic oligosaccharide engineering, and DBCO-PEG4-POL was further specifically modified onto the surface of HeLa cells via the SPAAC "click" reaction. In vitro investigations revealed that compared with unmodified HeLa cells, modified cells not only resist the adsorption of nonspecific proteins such as fibrinogen and human serum albumin but also selectively bind to plasminogen in plasma while maintaining good cell viability and proliferative activity. More importantly, upon the activation of adsorbed plasminogen into plasmin, the modified cells exhibited remarkable fibrinolytic activity and were capable of promptly dissolving the primary thrombus formed on their surfaces. This research not only provides a novel approach for constructing transplantable cells with fibrinolytic activity but also offers a new perspective for effectively addressing the significant loss of transplanted cells caused by thrombosis.

Nonspecific interaction between plasminogen and modified magnetic iron oxide nanoparticles

The magnetic particles modified with silicon dioxide (SiO₂) and amino groups (-NH₂), as well as the magnetic particles modified with human serum albumin (HSA) were synthesized using the approaches we developed before and characterized by physico-chemical methods in this study. Plasminogen was chosen as a model protein since plasminogen plays a major role in the fibrinolytic system and plasminogen level correlates with different pathologies and conditions. For the first time it has been carried out qualitative and quantitative assessment of plasminogen nonspecific binding (noncovalent adsorption) by the particles in buffer and plasma solutions. The fibrinolytic activity of plasminogen on the surface of the particles has been measured by the aid of commercially available kits and appeared to be 28-30% of its initial value. Plasminogen desorption from the surface of particles was studied in phosphate buffer with NaCl and ε-aminocaproic acid. Despite nonspecific plasminogen binding is an undesirable process, the data obtained is valuable for further modification of particles for high-specific proteins extraction from biological fluids or transport of plasminogen by the particles. The perspectives of particles modified with SiO₂ and -NH₂, and particles modified with HSA for isolation of protein analytes and their quantitative assessment thereafter have been discussed.