Fig. 3.
Label-free skin penetration measurement of topically applied drugs: (a-b) Raman spectra of lidocaine hydrochloride (LID), loxoprofen sodium salt (LOX), and an untreated skin tissue model (STM) measured using (a) spontaneous Raman spectroscopy and (b) PM-SRS. (c-d) PM-SRS skin penetration images captured at 30 min and 240 min after applying (c) 4% LID and (d) 4% LOX solutions. The scale bar is 50 μm.