Figure 5 | Microsystems & Nanoengineering

Figure 5

From: Low-cost and cleanroom-free fabrication of microneedles

Figure 5

Polymer casting and microneedle fabrication method and needle characterization. (a) Initially the surface of the PDMS mold in oxygen plasma treated; (b) the mold is submerged in petri dish with the polyvinyl alcohol (PVA) solution containing phenol red dye (as a drug model); (c) air bubbles were removed and the solution was condensed by placing the dish in vacuum condition inside desiccator for 7 days; (d) the mold was placed on hot plate to dehydrate and dry the patch; (e) the microneedle patch was pilled off the mold after complete drying; (f) the fabricated PVA microneedle patch, the red color is due to phenol red; (g) scanning electron microscopic (SEM) images of the PVA needle before drug release, showing smooth dense surface with not observable porosity; (h) PVA microneedle patch, after drug release (incubation in phosphate-buffered saline (PBS) at 37 °C for 24 h), the red dye is almost gone but the needles almost preserve their shape; (i) SEM images of needle after release (dried); shape and surface of the needles did not significantly change, confirming that the drug release mostly happens due to diffusion and not degradation; (j) FTIR results for non-crosslinked and crosslinked PVA (PVA microneedle patch); (k) swelling ratio of the PVA needles; (l) degradation of the PVA needle in PBS (less than 8% after 48 h) (m) showing the in vitro skin and release model; (n) release of the drug into the hydrogel after 5 min; (o) release of the drug after 5 h and (p) cumulative release model over time.

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