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_D), bipolar (δ_P), and hydrogen bonding (δ_H) were calculated by HSPiP software. Results showed δ_D, δ_P, and δ_H 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_P. Increased temperature decreased them with more changes in δ_H. 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.