Cross-linked gels of chemically activated carboxypolysaccharides and polyalkylene oxides
a technology of chemically activated carboxypolysaccharides and cross-linked gels, which is applied in the direction of genetic material ingredients, organic active ingredients, peptide/protein ingredients, etc., can solve the problems of inability to easily manufacture cps or cmc derivatives that can form covalent, ionic or other bonds, and inability to use derivatized cmc or other cps in polymers useful for drug delivery, hemostasis and/or adh
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example 1
Preparation of CMC Having Primary Amine Groups
[0066] Primary amines can be introduced to the side chains of CMC by covalent modification of the carboxylic acids (carboxylate chains) in the polysaccharide with compounds containing primary amines at either end, such as ethylendianine (EDA), to form amide linkages. To ensure that only one end of the compound coupled to each carboxylate and does not cross-link the macromolecules being modified, the diamine should be used in excess. Amide bond formation may be accomplished by several methods including carbodiimide mediated coupling, active ester intermediates, and the use of carbonylating compounds. In this study, a water soluble carbodiimide, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), was used. A protocol is described in the following paragraph.
Materials:
[0067] CMC (degree of substitution, “DS”, 1.19), 3.0 g in 300 ml MES buffered saline (pH 4.7), EDA, 30.6 g in 45 ml MES; and EDC, 2.92 g in 5 ml MES.
Proce...
example 2
Viscosity of CMC-N and CMC-N / PEO Composites
[0073] Primary amine carried CMC derivatives (CMC-N) prepared from CMCs with various DS (0.8 and 1.2) and molecular weight (700 K and 250 K Dalton) were firstly characterized for viscosity in various formulations: (1) composite gel with PEO (CMC-N / PEO); (2) in the presence (3) in the absence of calcium ion; and (4) as a coacervate with CMC. Experiment was performed at ambient temperature using a Brookfield Digital Viscometer (Model VD-II, Brookfield Engineering Laboratory, Inc.; Stoughton, Mass.) at the shear rate of 05 and spindle #29. The pH of these materials was about 7. Results are shown in Table 2 below.
TABLE 2Viscosity of PEO / CMC CompositesSolutioncomposition (%)CMCCMC-NH2PEOViscosity (cps)1.0000.3 × 1032.0001.1 × 103a)2.0003.4 × 104b)2.0001.6 × 10301.000.3 × 1030a)1.001.2 × 10302.000.7 × 1031.001.00.4 × 10301.01.00.7 × 1030a)1.01.01.7 × 1031.01.00 2.3 × 103*a)1.0a)1.00 0.9 × 106*
Unless indicated, CMC used to prepare CMC-N derivat...
example 3
Tissue Adhesiveness of CMC-N / PEO Composites
[0075] The tissue adhesive property of gels was determined by measuring the force needed to detach the gels from the membrane using a modified Tape Loop Tack Tester (Model LT-100; ChemiInstruments, Fairfield, Ohio) equipped with a digital force meter (Chatillon Model DFM; Greensboro, N. J.). Membranes of porcine intestine were used as the receiver. The membranes were mounted onto each surface of both the test panel and specimen jaw, which was attached to the tension head by means of an yok and a release pin. The gap between the two membranes was adjusted to 2±1 mm by releasing and tightening the release pin. 5.0±0.1 ml of the gel were applied on the membrane bound to the test panel. All measurements were performed on settings as: [0076] Specimen jaw lowering speed: 9 mm / s [0077] Contact time: 3 minutes [0078] Contact area: 5.31 cm2 [0079] Specimen jaw withdrawal rate: 9 mm / s [0080] Withdrawal height: 4.5 cm
[0081] Each experiment was carri...
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