Clinical evaluation of photochromic nanoparticle tattoo ink: safety, tolerability, and performance of rewritable intradermal implants
摘要
‘Smart tattoos’ based on stimulus-responsive nanoparticles have emerged as a promising platform for intradermal biosensing and dynamic optical interfaces, yet translation to safe and sustained use in human skin remains largely untested. We report a pilot clinical evaluation of Magic Ink, a rewritable photochromic tattoo ink comprising nano-engineered pigments that switch reversibly between nearly colorless and magenta states under visible and ultraviolet light, enabling permanent intradermal tattoos to be visually erased and restored on demand. Preclinical studies established third-party-verified sterility and non-cytotoxicity, confirmed nanoparticle size/morphology and shear-thinning rheological behavior suitable for intradermal delivery, and demonstrated robust photochromic performance with rapid switching kinetics and high fatigue resistance. In a paired, within-subject study, 11 participants received matched Magic Ink and commercial ‘Standard Ink’ control tattoos. Healing outcomes were assessed by clinical inspection (days 7 & 21), participant surveys through day 21, and longitudinal photographic documentation over five months. No adverse events were observed (0/11 per group). Dermatologist assessments and participant-reported symptoms of pain, redness, and itch did not differ significantly between Magic Ink and Standard Ink tattoos. Magic Ink tattoos remained nearly imperceptible in the deactivated state yet became readily visible upon UV activation after at least one year in vivo, demonstrating durable retention of photoswitchable function in human skin. These results indicate that photo-rewritable tattoo nanomaterials can function as tolerable intradermal implants over the timescales examined, and support their further evaluation for dynamic or ‘disappearing’ tattoos in medical (e.g., radiotherapy treatment localization and biopsy site marking in dermatology), cosmetic and paramedical (e.g., permanent makeup and micropigmentation), and body art applications.
Graphical abstract