The effect of polyelectrolyte counterion specificity, charge density, and conformation on polyelectrolyte-amphiphile interaction: the carrageenan/furcellaran-amitriptyline system.
The effect of polyelectrolyte cation specificity, charge density, and conformation on the interaction between furcelleran, kappa, iota, and lambda-carrageenan, respectively, and amitriptyline, an amphiphilic cationic drug molecule, was studied by means of a dialysis equilibrium technique. The carrageenans used in this study-furcelleran, kappa, iota, and lambda-carrageenan-had a charge density corresponding to 0.69, 0.92, 1.53, and 2.07 sulfate groups per disaccharide. In general, the binding isotherms followed the order Li(+) < Na(+) < N(CH3)(4)(+) < K(+) < or = Cs(+) approximately Rb(+), i.e., the binding isotherms were shifted to higher concentrations of free amphiphile according to the sequence indicated. This affinity sequence correlates well with that found for the dextran sulfate-amitriptyline system (A. Hugerth and L.-O. Sundelöf, Langmuir 2000, 16, 313-317). The factor determining the critical aggregation concentration in the presence of Na(+) compared to K(+) was found to be as follows: the flexibility (conformation) in the case of the lower charged carrageenans, i.e., furcelleran and kappa-carrageenan, charge density for iota-carrageenan, and in the lambda-carrageenan case the difference in the ROSO(3)(-)-alkali ion specificity.
Hugerth
A
A
Physical Pharmaceutical Chemistry, Uppsala University, Uppsala Biomedical Center, Box 574, S-751 23 Uppsala, Sweden.
Sundelöf
L O
LO
D000464:Alginates / Q000737:chemistry; D000639:Amitriptyline / Q000737:chemistry; D002236:Carbohydrate Conformation; D002351:Carrageenan / Q000737:chemistry*; D004563:Electrochemistry; D004573:Electrolytes; D009994:Osmolar Concentration; D053149:Plant Gums
D000464:Alginates; D004573:Electrolytes; D053149:Plant Gums; D000639:Amitriptyline; D002351:Carrageenan; C012985:furcellaran