Author Contributions
Conceptualization, T.E. and S.K.; Methodology, S.K. and T.E.; Formal Analysis, T.E.; Investigation, T.E., K.M., E.O., G.S., C.L., M.O. and F.I.; Resources, S.K.; Data Curation, T.E.; Writing-Original Draft Preparation, T.E.; Writing-Review & Editing, S.K. and T.E.; Supervision, S.K. and T.E.; Project Administration, S.K.; Funding Acquisition, S.K.
Figure 1.
Ultrasonic amplitude, ultrasonic duration, molecular size, and molecular charge influence the amount of molecular release from Ca2+ crosslinked hydrogels. (a) FITC-dextran-loaded Ca2+ crosslinked alginate hydrogel fabrication: casting gel on a sigma-coated glass plate (i), cutting into 8-mm-diameter cylindrical gels using a biopsy punch (ii), putting a gel in a scintillation vials with 5 mL DPBS (iii), gels before, during, and after ultrasound stimulation (iv–vi), and 1 mL sample collection for quantifying molecular release (vii). (b–e) FITC-dextran release (b,c) and diethylaminoethyl (DEAE)-FITC-dextran release (d,e) vs. ultrasonic amplitude for gels exposed to 1-min (blue) and 5-min (red) of ultrasonic stimulation. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 1.
Ultrasonic amplitude, ultrasonic duration, molecular size, and molecular charge influence the amount of molecular release from Ca2+ crosslinked hydrogels. (a) FITC-dextran-loaded Ca2+ crosslinked alginate hydrogel fabrication: casting gel on a sigma-coated glass plate (i), cutting into 8-mm-diameter cylindrical gels using a biopsy punch (ii), putting a gel in a scintillation vials with 5 mL DPBS (iii), gels before, during, and after ultrasound stimulation (iv–vi), and 1 mL sample collection for quantifying molecular release (vii). (b–e) FITC-dextran release (b,c) and diethylaminoethyl (DEAE)-FITC-dextran release (d,e) vs. ultrasonic amplitude for gels exposed to 1-min (blue) and 5-min (red) of ultrasonic stimulation. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 2.
The amplitude and duration of ultrasonic stimulation impact the amount of chemotherapeutic released. Release vs. ultrasonic amplitude for mitoxantrone (a), irinotecan (b), and 5-fluorouracil (c). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 2.
The amplitude and duration of ultrasonic stimulation impact the amount of chemotherapeutic released. Release vs. ultrasonic amplitude for mitoxantrone (a), irinotecan (b), and 5-fluorouracil (c). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 3.
The amplitude and duration of ultrasonic stimulation impact the amount of signaling factor released. Release vs. ultrasonic intensity for Vascular Endothelial Growth Factor (VEGF) (a) and Platelet-Derived Growth Factor (PDGF) (b). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 3.
The amplitude and duration of ultrasonic stimulation impact the amount of signaling factor released. Release vs. ultrasonic intensity for Vascular Endothelial Growth Factor (VEGF) (a) and Platelet-Derived Growth Factor (PDGF) (b). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 4.
Ultrasound erodes and heats the gels in manners that are dependent on the intensity and duration of the applied ultrasound. (a) Photographs of mitoxantrone-loaded hydrogels after exposure to the US at the indicated amplitudes and durations. (b) Percent weight loss vs. US intensity for gels stimulated for 1 min (light blue) and 5 min (light purple). (c) Temperature elevation vs. US intensity for gels stimulated for 1 min (yellow) and 5 min (orange). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 4.
Ultrasound erodes and heats the gels in manners that are dependent on the intensity and duration of the applied ultrasound. (a) Photographs of mitoxantrone-loaded hydrogels after exposure to the US at the indicated amplitudes and durations. (b) Percent weight loss vs. US intensity for gels stimulated for 1 min (light blue) and 5 min (light purple). (c) Temperature elevation vs. US intensity for gels stimulated for 1 min (yellow) and 5 min (orange). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared to controls (0% amplitude) unless otherwise specified with lines. N = 4.
Figure 5.
Pulsed ultrasound can enhance drug delivery while helping to control gel erosion and heating. (a) Photos of hydrogels (bottom row) after exposure to the illustrated ultrasonic pulse trains (top row). (b) Percent weight loss of hydrogels vs. pulse number. (c) Temperature rise vs. pulse number. (d) Mitoxantrone release vs. pulse number. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared controls unless otherwise specified with lines. N = 4.
Figure 5.
Pulsed ultrasound can enhance drug delivery while helping to control gel erosion and heating. (a) Photos of hydrogels (bottom row) after exposure to the illustrated ultrasonic pulse trains (top row). (b) Percent weight loss of hydrogels vs. pulse number. (c) Temperature rise vs. pulse number. (d) Mitoxantrone release vs. pulse number. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, compared controls unless otherwise specified with lines. N = 4.
Figure 6.
Ultrasound can be used to generate pulsatile chemotherapeutic delivery profiles over a 3-day period, though gel structure is not maintained, and delivery rates change vs. time. (a) Photos of hydrogels immediately after ultrasonic exposures on the indicated days. (b–d) The rate of mitoxantrone release vs. time when stimulated with pulsed ultrasound for 1 h each day for control and one 1-min pulse (b), two 1-min pulses (c), and three 1-min pulses (d). Plots of release rates vs. time are meant to highlight differences in release rates during periods of ultrasonic stimulation (from 0–1, 24–25, and 48–49 h) vs. periods of no stimulation (from 1–24 and 25–48 h). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, relative to controls. n.s. indicates that no statistical significance was found compared to controls (p > 0.05). N = 4.
Figure 6.
Ultrasound can be used to generate pulsatile chemotherapeutic delivery profiles over a 3-day period, though gel structure is not maintained, and delivery rates change vs. time. (a) Photos of hydrogels immediately after ultrasonic exposures on the indicated days. (b–d) The rate of mitoxantrone release vs. time when stimulated with pulsed ultrasound for 1 h each day for control and one 1-min pulse (b), two 1-min pulses (c), and three 1-min pulses (d). Plots of release rates vs. time are meant to highlight differences in release rates during periods of ultrasonic stimulation (from 0–1, 24–25, and 48–49 h) vs. periods of no stimulation (from 1–24 and 25–48 h). *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, relative to controls. n.s. indicates that no statistical significance was found compared to controls (p > 0.05). N = 4.
Figure 7.
Pulsatile delivery profiles with consistent release rates vs. time can be achieved by altering the US pulse number over time. (a) Photos of hydrogels immediately after ultrasonic exposure on each day for control gels and those exposed to the indicated pulsed US regiment. (b) Release rate vs. time when stimulated with 3, 1-min; 2, 1-min; and 2, 1-min ultrasound pulses on day 1, 2, and 3, respectively. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, relative to controls. N = 4.
Figure 7.
Pulsatile delivery profiles with consistent release rates vs. time can be achieved by altering the US pulse number over time. (a) Photos of hydrogels immediately after ultrasonic exposure on each day for control gels and those exposed to the indicated pulsed US regiment. (b) Release rate vs. time when stimulated with 3, 1-min; 2, 1-min; and 2, 1-min ultrasound pulses on day 1, 2, and 3, respectively. *, **, ***, and **** indicate statistically significant differences with p < 0.05, 0.01, 0.001, and 0.0001, respectively, relative to controls. N = 4.
Figure 8.
Ultrasonically responsive gels can be used to generate a triggered release of irinotecan after an initial burst release of 5-fluorouracil. (a) Cumulative release of 5-fluorouracil (blue) and irinotecan (red) vs time when ultrasonically stimulated for 2-min at 40% US amplitude at 18 h. Control gels (black) were not subjected to ultrasonic stimulation at 18 h. (b) The 18-h average rate of 5-fluorouracil and irinotecan release vs. time for the same conditions presented in part (a). * and ** indicate statistically significant differences with p < 0.05 and 0.01, respectively, relative to controls. N = 4.
Figure 8.
Ultrasonically responsive gels can be used to generate a triggered release of irinotecan after an initial burst release of 5-fluorouracil. (a) Cumulative release of 5-fluorouracil (blue) and irinotecan (red) vs time when ultrasonically stimulated for 2-min at 40% US amplitude at 18 h. Control gels (black) were not subjected to ultrasonic stimulation at 18 h. (b) The 18-h average rate of 5-fluorouracil and irinotecan release vs. time for the same conditions presented in part (a). * and ** indicate statistically significant differences with p < 0.05 and 0.01, respectively, relative to controls. N = 4.