Background Even though dermatologists often perform drug delivery procedures, it is necessary to assess their safety. Objective Quantify the amount of medication delivered using the MMP drug delivery technique and outline other safety parameters. Methods Using a simple and novel technique, we attempted to quantify the amount of medication delivered by weighing human skin samples before and after delivery. Results In drug delivery done on human skin using a liquid with a density of 1,271,460 μg/ml (the values expressed in this manuscript are in µg), a needling density of 570 perforations/cm2, and a needling depth of 300 microns, we estimate that 1,175 μg/cm2 were delivered (standard deviation 601 μg/cm2, standard error 190 μg/cm2). Limitations This result is only applicable to the protocol proposed in this study for the MMP drug delivery technique. Conclusion The MMP drug delivery technique injects small amounts of medication (1,175 μg/cm2) homogeneously into the dermis.

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Thermal aging of hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB/IPDI)-based polyurethane was studied as a function of NCO/OH ratio (1.0 and 0.85). Samples were aged in air ovens at 50, 60, 65, and 70 °C for periods of time from 1 to 34 weeks. Changes in chemical (swelling testing and FT-IR spectroscopy) and mechanical (tension testing and hardness) properties were evaluated throughout the aging assays. Correlation between equilibrium swelling ratio and elastic modulus, coupled with changes in FT-IR spectra, indicated oxidative cross-linking as the dominant mechanism for both molar ratios investigated. However, determination of Arrhenius activation energy resulted in values of (82 ± 10) kJ.mol -1 and (156 ± 30) kJ.mol -1 for 1.0 and 0.85 NCO/OH ratios, respectively, thus revealing faster oxidative degradation kinetics for higher urethane linkage networks.