Effects of the gene carrier polyethyleneimines on structure and function of blood components.

As a synthetic polycation, polyethylenimine (PEI) is currently one of the most effective non-viral gene carriers. For in vivo applications, PEI will enter systemic circulation and interact with various blood components and then affect their individual bio-functions. Up to now, overall and systematic investigation on the interaction of PEI with multiple blood components at cellular, membrane, and molecular levels is lacking, even though it is critically important for the in vivo safety of PEI. To learn a structure-activity relationship, we investigated the effects of PEI with different molecular weight (MW) and shape (branched or linear) on key blood components and function, specifically, on RBC aggregation and morphological change, platelet activation, conformation change of albumin (as a representative of plasma proteins), and blood coagulation process. Additionally, more proteins from plasma were screened and identified to have associations with PEI by a proteomic analysis. It was found that, the PEIs have severe impact on RBC membrane structure, albumin conformation, and blood coagulation process, but do not significantly activate platelets at low concentrations. Furthermore, 41 plasma proteins were identified to have some interaction with PEI. This indicates that, besides albumin, PEI does interact with a variety of blood plasma proteins, and could have unexplored effects on their structures and bio-functions. The results provide good insight into the molecular design and blood safety of PEI and other polycations for in vivo applications.

The effect of the gene carrier material polyethyleneimine on the structure and function of human red blood cells in vitro.

Human red blood cells (RBCs) have high abundance in blood tissue, usually 40-50% v/v. For the in vivo administered biomedical materials in contact with blood tissue, the RBCs are the major (in most cases, undesired) targets encountered. The interaction of the biomaterials with the RBCs will unavoidably occur, affecting the structure and function of the RBCs and then the whole organism. For the clinical applications of biomaterials, this effect should be clearly elucidated since it may cause acute or chronic harm to the organism. Moreover, the RBC-based experimental results could be extended to other tissue cells to a great extent. In this study, the effect of the branched polyethyleneimines (BPEIs) as a gene carrier on the structure and function of human RBCs was studied by using different molecular weights of the BPEIs. Specifically, the RBC aggregation and lysis induced by the BPEIs were first studied; then, the structural and conformational change of hemoglobin in the presence of the BPEIs was examined by using UV-vis, fluorescence, and circular dichroism spectroscopy. Furthermore, the oxygen-carrying function of the RBCs in the presence of the BPEIs was evaluated by measuring the 2,3-diphosphoglycerate (2,3-DPG) level and oxygen-dissociation curves. The results showed that the BPEIs with certain molecular weights at certain concentrations could cause RBC aggregation and lysis, alter the structure and conformation of hemoglobin, and impair the oxygen-delivery function of the RBCs. These data provide valuable information for the molecular design and clinical applications of the BPEIs and other biomedical materials.

Effect of chitosan and carboxymethyl chitosan on fibrinogen structure and blood coagulation.

Chitosan has numerous biomedical applications such as tissue engineering scaffolds, drug/gene delivery systems, hemostasis materials, antibacterial materials, wound dressing, etc. In any case, chitosan administered in vivo would positively or passively contact or enter blood tissue. In this situation, the interaction of chitosan with blood components is critical to determine the efficacy and safety of the polymer. In this study, the effect of chitosan with different molecular weight and its derivative carboxymethyl chitosan (CMC) on the structure and function of clotting-related proteins was studied. Specifically, the structural and conformational change of fibrinogen, an important clotting protein, was studied by using UV, fluorescence, and circular dichroism spectroscopy, respectively. Further, the impact of chitosan and CMC on the clotting function was evaluated with activated partial thromboplastin time (APTT), prothrombin time (PT), fibrinogen time (FT), and thromboelastography (TEG) assays. These results showed that, chitosan and fibrinogen can form complex mainly by electrostatic attraction. As a result, the structure and conformation of fibrinogen are altered by chitosan and CMC. Additionally, the presence of chitosan and CMC has little impact on the values of APTT, PT and FT, but causes significant abnormality in the clotting process by changing TEG parameters. These results provide important insight into the molecular basis for the biological response to chitosan and other biopolymers.

Preparation and characterization of PEM-coated alginate microgels for controlled release of protein.

In this study, calcium-alginate microgels coated with a polyelectrolyte multilayer (PEM) were fabricated as a controlled-release system. This system was constructed via an electrostatic droplet generation technique followed by a layer-by-layer (LbL) self-assembly technique. The electrostatic droplet generation technique was reported as an easy method of preparing microgels, due to their mild preparation conditions and ability to preserve the biological activity of the encapsulated drugs. With the LbL self-assembly technique, the PEM could be fabricated on the microgels attributed to the electrostatic attraction between positive-charged chitosan (Chi) and negative-charged dextran sulfate (Dex). The properties of the prepared microgels were investigated using dynamic laser scattering (DLS), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectrum and zeta potential analyzer. In vitro release study indicated that the initial burst release of the bovine serum albumin (BSA) from PEM-coated microgels was less compared to the uncoated microgels (19% versus 31% in 24 h). In addition, the sustained release of BSA from the PEM-coated microgels was recorded up to 1 month without any damage to BSA integrity. Thus, our results demonstrated that the PEM-coated microgels not only prolonged the release time, but also relieved the initial burst problem to some degree and preserved the biological activity of the encapsulated drugs. Moreover, the release rate of BSA could be regulated by controlling the number of deposited layers. In conclusion, this study presented an easy yet effective method for the controlled, sustained release of biological macromolecules.