Topical application of beads made from poly(methacrylic acid-co-methyl methacrylate) (45 mol % methacrylic acid, MAA) increased the number of blood vessels and improved 1.5 x 1.5 cm full thickness wound closure in a diabetic mouse (db/db) model. Three groups were compared: MAA beads, control poly(methyl methacrylate) beads (PMMA), and no bead blanks. MAA bead treatment significantly increased percent wound closure at all timepoints (7, 14, and 21 days) with MAA bead-treated wounds almost closed at day 21 (91 +/- 5.4% MAA vs. 79 +/- 3.2% PMMA or 76 +/- 4.8% no beads; p < 0.05). This was consistent with the expected significant increase in vascularity in the MAA group at days 7 and 14. For example at day 14, MAA bead-treated wounds had a vascular density of 22.7 +/- 2.6 vessels/hpf compared with 17.0 +/- 2.0 vessels/hpf in the PMMA bead group (p < 0.05). Epithelial gap and migration measurements suggested that the increased vascularity leads to enhanced epithelial cell migration as a principal means of wound closure. Although studies are underway to elucidate the mechanism of this angiogenic response, the results presented here support the notion that such materials, perhaps in other forms, may be useful in wound care or in other situations where vascularity is to be enhanced without the use of exogenous growth factors.

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Plasma electrolysis, where a solid electrode in an electrolytic cell is replaced by a plasma (or gas discharge), differs from conventional electrolysis by not being dictated by the surface characteristics of an electrode, but by the chemical species injected into the solution from the plasma. Reduction in a plasma cathode configuration occurs mostly by plasma-injected solvated electrons (e − aq ), which may engage in side reactions, such as the second order recombination of e − aq , that ultimately reduce the faradaic efficiency for the production of a desired product. In this work, we show that the depletion of reactants at the plasma-liquid interface due to insufficient transport can reduce the predicted faradaic efficiency for a plasma cathode at low concentrations. Measurements of the faradaic efficiency using the dissociative electron attachment to chloroacetate and the ferri/ferrocyanide redox couple confirm this behavior. The effect of other mechanisms on the faradaic efficiency, such as competing oxidation reactions with the hydroxyl radical, are also evaluated and found to be far less significant. Unlike conventional electrolysis, stirring the solution does not increase the faradaic efficiency, but increasing the species concentration does.

In this work, the transport of the plasma injected solvated electron is experimentally studied using total internal reflection absorption spectroscopy (TIRAS). A recently derived a theoretical model predicts power-law scalings between the interfacial concentration n 0 and penetration depth l with plasma current density j, namely n 0 ∝ j e ( 2 3 ) and l ∝ j e ( − 1 3 ) . Here, we extend this model to show that the optical absorption intensity should follow a 1 3 power law behavior with current density, and we perform TIRAS measurements to confirm this behavior. By altering the ionic strength (salt concentration) of our electrolyte solution to control the current density, we find that at higher concentrations a scaling of approximately 1 3 power is observed. However, the scaling is linear at lower concentrations, which we show is due to the transient response of the TIRAS experiment operating in a modulated mode. Ultimately, the experimentally-confirmed scaling law predicts approximate upper limits of penetration depth and interfacial concentration for solvated electrons, findings essential for tailoring plasma-liquid systems for specific applications.

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