Hydrogel-Forming Microneedle Arrays Allow Detection of Drugs and Glucose In Vivo: Potential for Use in Diagnosis and Therapeutic Drug Monitoring - Fig 5

(A) Quantity of caffeine (μg) taken up in vitro by MN arrays 5 and 60 min after insertion into dermatomed excised neonatal porcine skin mounted on modified Franz cells and bathed on the underside by phosphate buffered saline pH 7.4 thermostated to 37°C and containing defined concentrations of caffeine (Means ± SD, n = 6). (B) Comparison of caffeine (μg) detected in plasma versus levels detected from MN arrays inserted in the forearm of human volunteers at defined time points (0–1, 1–2, 2–3 and 0–3 h) following administration of defined caffeine doses (Mean ± SD, n = 9). (C) Exemplar chromatogram showing HPLC detection of caffeine following extraction from MN after insertion in the forearm of a human volunteer for 1 h. Dose administered = 100 mg oral caffeine in the form of two Proplus® tablets. (D) Exemplar chromatogram showing HPLC detection of caffeine from a plasma sample obtained from a human volunteer 1 h after the administration of 100 mg of caffeine. 7-BHT was used as an internal standard.