Thermodynamic and NMR studies of some copper(II)-diaminomonocarboxylate equilibrium systems in aqueous solution

Facile wound dressing replacement: Carbon dots for dissolving alginate hydrogels via competitive complexation

Dissolvable hydrogels have shown great potentials in removing the exudes and alleviating pain during wound dressing replacement. Herein, a series of carbon dots (CDs) composing high complexation ability with Cu²⁺ were prepared for capturing Cu²⁺ from Cu²⁺-alginate hydrogels. CDs were prepared using biocompatible lysine as the main starting material, while ethylenediamine was chosen as the other starting material for its extremely high complexation ability with Cu²⁺. The complexation ability increased with the increasing amount of ethylenediamine, while the cell viability decreased. When the mass ratio of ethylenediamine to lysine in CDs was above 1/4, six-coordinate copper centers could be formed. CD_1/4 at the concentration of 90 mg/mL could dissolve Cu²⁺-alginate hydrogels within 16 min, which was about twice faster than lysine. In vivo results showed the replaced hydrogels could ameliorate hypoxic conditions, alleviate local inflammatory reactions and promote the healing speed of burn wounds. Thus, the above results suggested the competitive complexation of CDs with Cu²⁺ could effectively dissolve Cu²⁺-alginate hydrogels, which have much potential in realizing facile wound dressing replacement.

The speciation of lysine-complexed copper as a bovine nutritional supplement

Copper deficiencies in ruminants can be corrected by administering either free (inorganic) or complexed (chelated) copper. Chelated forms are thought to be more bioavailable as they are more stable, and may therefore be absorbed intact. Formation constants for the complexes between copper and the different ligands in the digestive tract can be used to predict if the chelate does, in fact, remain intact. Using a gravimetric autotitrator, the various complex formation constants for the copper(II) lysine system were determined at 38 degrees C, the temperature of the rumen environment. Formation constants for copper(II) complexes with the amino acids glycine and histidine were also determined at 25 and 38 degrees C. The formation constants for the copper(II) lysine system were then utilized in computer simulations to determine the fate of the complex prior to arriving at the rumen. The speciation of the copper(II) lysine system was determined in McDougall's solution, a simulated form of bovine saliva. Results suggest that if copper is administered as copper lysine "chelate," this will disintegrate and the copper will be present mainly as carbonate and phosphate complexes.