Fig. 4

US stimulus-mediated release of rtPA from rmDPPs. (a) Schematic procedure of rtPA release depending on the acoustic stimulus. (b) Biodegradability assay for quantification of rtPA release due to PLGA hydrolysis (left) and quantification of rtPA leakage due to the +US and +M+US (right), confirming the burst release of rtPA was feasible through the magnetoacoustic approach in the rmDPPs. (c) Schematic mechanism of the measurement of enzymatic activity. (d) Quantification of the enzymatic activity depending on the acoustic stimulus. Plasmin substrates contained the chromophore pNA and released pNA when they reacted with plasmin, demonstrating the enzymatic activity though the colorimetric method was successful. 1 mg of rtPA was presented as the optimal drug loading in the polymeric structure, showing the highest cumulative enzymatic activity among the test groups (all \(n=5\))