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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.

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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.

This work is to develop a novel dual drug delivery system that can simultaneously load and release 18β‐glycyrrhetinic acid (GA, a hydrophobic drug) and bovine serum albumin (BSA, hydrophilic model drug) in a single formulation. The system consists of poly(D,L‐lactic) (PDLLA) microspheres embedded in calcium alginate hydrogel beads. The GA‐loaded microspheres were first prepared and then dispersed in the aqueous solution of sodium alginate and BSA. The resulting suspension was dropped into aqueous calcium chloride solution to obtain the dual drug delivery system. The morphology of the microspheres and beads, the drug content and loading efficiency, the interaction between GA and PDLLA, and the drug release behaviors were studied. Scanning electron microscope (SEM) revealed that the PDLLA microspheres were homogeneously distributed in the beads. Differential scanning calorimetry (DSC) measurement suggested certain interaction between GA and PDLLA, and the crystal structure of GA was influenced by the polymer. The dual release in vitro showed a rapid BSA release but a sustained GA release in all the systems. Furthermore, the release rate of BSA was accelerated by increasing PDLLA/alginate ratio, while the release rate of GA was decreased, and the release of both hydrophobic and hydrophilic drugs could be adjusted by changing the ratio of PDLLA/alginate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 20122