Microneedles for liquid cargo and nanovehicle delivery. (a–d) Fang-mimicked microneedles for liquid delivery: (a) schematic illustration of venom delivery by rear-fanged snakes; (b) SEM images of trigrooved (i, v), tetragrooved (ii, vi), pentagrooved (iii, vii), and hexagrooved (iv, viii) microneedles; (c) schematic illustration of microneedles bonded to a PDMS chamber; (d) corresponding optical photos. The scale bars are 100 μ
m in (b) and the inset of (d) and 5 mm in (d). Reproduced with permission from Ref. [98
], copyright 2019, American Association for the Advancement of Science. (e) Schematic illustrations of microneedles carrying m-GOx and m-EX4 for blood glucose control. Reproduced with permission from Ref. [105
], copyright 2017, Springer Nature. (f) Schematic illustrations of microneedles carrying Apd1 and 1-MT in HA nanoparticles for tumor immunotherapy. Reproduced with permission from Ref. [118
], copyright 2016, American Chemical Society.