Figure 1:

Microparticle preparation and morphological characterization. (A) Schematic representation of the formulation strategy used to synthesize PLGA-based oxygen-releasing microparticles using CaO₂ as an O₂-releasing agent. An acetonitrile phase containing PLGA and CaO₂ was prepared and homogenized. An oil phase was prepared with Span80 as an emulsifier. As the acetonitrile phase diffused into an oil bath, the nonsolvent PLGA/CaO₂ phase was separated to form a droplet. The acetonitrile solvent in the presence of Span80 resulted in the spontaneous formation of continuous polylithic CaO₂ /PLGA microparticles followed by washing and drying. (B) Schematic representation of the oxygen-release mechanism from the fabricated microparticles with different compositions of CaO₂ encapsulated in PLGA coalesced during fabrication to yield a continuous morphology. (C) Zeta potential distribution of CPO microparticles and free CPO were measured. Three different PLGA to CaO₂ ratios were used to prepare the microparticles: 1:10, 1:4, and 1:2. CPO microparticles showed an increase in charge with higher CaO₂ loading (n=3). (D) SEM images of CPO microparticles: (i) PLGA, (ii) CPO1, (iii) CPO2, and (iv) CPO3. Scale bar = 50 μm (upper panel). A cross-sectional view of microparticles obtained from a paraffin block revealed the internal structures of the microparticles. Scale bar = 10 μm (middle and lower panel) for the respective microparticle composition. (E) CPO microparticle size distributions show the average sizes of three different CPO microparticle formulations. (Number of particles, n = 71, 62, 51, and 83 for PLGA, CPO1, CPO2, and CPO3, respectively). One-way ANOVA was used for the significance test (* p < 0.05).