Mechanical Aspects of the Hemostatic Characteristics of Chitosan-Based Wound Dressings
2018
Hochschulschrift
Zugriff:
106
Chitosan-based wound dressings are superior to traditional dressings for hemostatsis, and can arrest bleeding with clotting dysfunction. It is generally claimed, but without detailed reasoning, that “the chitosan cross-links red blood cells (RBCs) to form mucoadhesive barrier” to block the bleeding. The first goal of this study is to understand the related mechanism from a mechanical view point. Hemostatsis succeeds using chitosan under clotting dysfunction was supported qualitatively by animal tests, but quantitative measurement was still lacking. The second goal of this study is provide such a quantitative result in an in vitro environment. Static tests were employed mostly for the hemostatic performance tests of various dressings, but it would be more realistic if the test was performed in a flowing environment. A flow-through device (called the CPG device here) was proposed by Jesty et al. (2009) under a constant pressure gradient, and the performance was assessed via measuring the amount of fluid masses through the device. However, a substantial amount of test fluid is required for the testing using the CPG device. The third goal of this study is to propose an alternative device using less test fluid. Three works were accomplished in this study. First, a flow-through device under a constant flow rate (called the CFR device) was proposed and demonstrated successfully for assessing dynamically the hemostatic performance of various wound dressings via comparing the testing using the CPG device. The pressure drops across the dressings are measured for assessing the performance in the CFR device. The CFR device consumes less test fluid, but the CPG device models more realistic the scenario of bleeding. Secondly, detailed experiments were performed using the CFR device with both the human whole blood and washed blood (with clotting factors and platelets removed) as test fluids, and the results agree with each other within experimental errors. Such quantitative findings show definitely that the hemostatic enhancement due to chitosan is independent of classical clotting pathways. Thirdly, the adhesion forces of red blood cells on various yarns were measured using an optical tweezers. The adhesion force is small, around 3.83 pN, such that the direct adhesion cannot be the sole cause for hemostasis. However, it was observed that layer structures of aggregated RBCs were formed next to chitosan objects in both static and flowing environments, but not formed next to other yarns. Such a layer structure is the clue for the initiation of the mucoadhesive barrier, and thus hemostatsis. Through the supporting measurements of zeta potentials of RBCs and pH’s using blood-chitosan mixtures, it is proposed here that the formation of the RBC layer structures next to chitosan objects is due to the reduction of repulsive electric double layer force between RBCs, because of the association of H+ deprotonated from chitosan with COO on RBC membrane, under the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. The results are beneficial for designing effective chitosan-based wound dressings, and also for general biomedical applications.
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Mechanical Aspects of the Hemostatic Characteristics of Chitosan-Based Wound Dressings
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Autor/in / Beteiligte Person: | Chen, Kuan-Yu ; 陳冠宇 |
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Veröffentlichung: | 2018 |
Medientyp: | Hochschulschrift |
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