Relevance of rheological properties of sodium alginate in solution to calcium alginate gel properties.

The purpose of this study is to determine whether sodium alginate solutions' rheological parameters are meaningful relative to sodium alginate's use in the formulation of calcium alginate gels. Calcium alginate gels were prepared from six different grades of sodium alginate (FMC Biopolymer), one of which was available in ten batches. Cylindrical gel samples were prepared from each of the gels and subjected to compression to fracture on an Instron Universal Testing Machine, equipped with a 1-kN load cell, at a cross-head speed of 120 mm/min. Among the grades with similar % G, (grades 1, 3, and 4), there is a significant correlation between deformation work (L(E)) and apparent viscosity (η(app)). However, the results for the partial correlation analysis for all six grades of sodium alginate show that L(E) is significantly correlated with % G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium alginate show that η(app) of their solutions did not correlate with L(E) while tan δ was significantly, but minimally, correlated to L(E). These results suggest that other factors--polydispersity and the randomness of guluronic acid sequencing--are likely to influence the mechanical properties of the resultant gels. In summary, the rheological properties of solutions for different grades of sodium alginate are not indicative of the resultant gel properties. Inter-batch differences in the rheological behavior for one specific grade of sodium alginate were insufficient to predict the corresponding calcium alginate gel's mechanical properties.

Prospective randomized controlled study of Hydrofiber dressing containing ionic silver or calcium alginate dressings in non-ischaemic diabetic foot ulcers.

AIMS: Diabetic foot ulcers (DFUs) are at risk of infection and impaired healing, placing patients at risk of lower extremity amputation. DFU care requires debridement and dressings. A prospective, multicentre study compared clinical efficacy and safety of AQUACEL Hydrofiber dressings containing ionic silver (AQAg) with those of Algosteril calcium alginate (CA) dressings in managing out-patients with Type 1 or 2 diabetes mellitus and non-ischaemic Wagner Grade 1 or 2 DFUs. METHODS: Patients stratified by antibiotic use on enrolment were randomly assigned to similar protocols including off-loading, AQAg (n = 67) or CA (n = 67) primary dressings and secondary foam dressings for 8 weeks or until healing. Clinical efficacy measures were healing outcomes and primarily healing speed. Adverse events were recorded. RESULTS: AQAg and CA groups were comparable at baseline. All ulcer healing outcomes improved in both groups. The mean time to healing was 53 days for AQAg ulcers and 58 days for CA ulcers (P = 0.34). AQAg-treated ulcers reduced in depth nearly twice as much as CA-treated ulcers (0.25 cm vs. 0.13 cm; P = 0.04). There was more overall ulcer improvement and less deterioration in AQAg subjects (P = 0.058), particularly in the subset initially using antibiotics (P = 0.02). Safety profiles of both groups were similar. CONCLUSION: When added to standard care with appropriate off-loading, AQAg silver dressings were associated with favourable clinical outcomes compared with CA dressings, specifically in ulcer depth reduction and in infected ulcers requiring antibiotic treatment. This study reports the first significant clinical effects of a primary wound dressing containing silver on DFU healing.