Fig. 2

PFR prolongs the duration of postoperative analgesia. A SEM images of PF and PFR (scale bar represents 2 μm). B Photos of PFR at 4 °C and 37 °C. C Temperature-dependent rheology of PFR aqueous dispersion. D Frequency-dependent rheology of PFR hydrogel at 37 °C. E The shear-thinning behavior of PFR hydrogel indicated by steady-shear rheology. FCumulative release profile of PFR. G Photos of plantar tumor before and after surgery. H Statistical results of the occurrence of convulsions in post operative mice administrated with PFR or free ropivacaine. I Schematic diagram of postoperative pain relief by PFR. PFR slowly releases ropivacaine, which blocks sodium channels and inhibits the conduction of surgery-triggered painful stimuli via afferent nerves. J Schematic diagram of thermal hyperalgesia assessment. The time to withstand thermal stimulation was recorded. K Paw withdrawal latency was measured at 0, 3, 10, 16, and 24 h after tumor resection with indicated analgesia (n = 5). L–M Immunofluorescence staining and statistical results of p-p38 in the spinal dorsal horn at three days after plantar tumor resection (scale bar represents 100 μm, n = 3). Rop ropivacaine, PFR PF hydrogel mixed with ropivacaine