Measurement of Hansen Solubility Parameters of third-degree burn eschar.

Topical drug therapy is one of the most effective approaches in third-degree burn wound treatments. To optimize and enhance drug permeation through burn eschar, we need to characterize this barrier, most importantly, its affinity to drugs; the subject of this investigation. Hansen Solubility Parameters (HSP), as polarity and affinity scale, were measured here for human third-degree burn eschar through uptake studies using 19 solvents at 25 °C and 32 °C and two hydration levels by gravimetric method combined with thermal analysis and Karl Fischer titration. HSP parameters of dispersion (δ), bipolar (δ), and hydrogen bonding (δ) were calculated by HSPiP software. Results showed δ, δ and δ of 17.0, 12.5, 14.6 and 16.8, 12.4, 14.4 at 25 and 32 °C respectively for normally-hydrated samples. Full hydration increased HSP values to 17.2, 12.9, 15.3 (25 °C) and 17.1, 12.8, 15.1 (32 °C). Good correlations between solvents uptakes and HSP values were observed for all parameters; higher for δ. Increased temperature decreased them with more changes in δ. Relative Energy Differences (RED) were calculated and shown to be a good parameter for predicting drug-eschar affinity. The obtained information is useful for drug selection and carrier design in drug delivery through burn eschar.