Translational medicine in the field of ablative fractional laser (AFXL)-assisted drug delivery: A critical review from basics to current clinical status

Fractional laser-assisted topical delivery leads to enhanced, accelerated and deeper cutaneous 5-fluorouracil uptake

BACKGROUND

Topical 5-Fluorouracil (5-FU) exhibits suboptimal efficacy for non-melanoma skin cancer, attributed to insufficient intracutaneous penetration. This study investigates the impact of ablative fractional laser (AFXL) at different laser-channel depths on cutaneous 5-FU pharmacokinetics and biodistribution.

METHODS

In vitro porcine skin underwent AFXL-exposure using a fractional 10,600 nm CO₂-laser, generating microscopic ablation zones (MAZ) reaching the dermoepidermal junction (MAZ-ED), superficial-(MAZ-DS), or mid-dermis(MAZ-DM). 5-FU in AFXL-exposed and control skin was measured in Franz diffusion cells at 4 and 24 hours (n = 55). HPLC quantified 5-FU in full-thickness skin, specific skin depths of 100μm-1500μm, and transcutaneous receiver-compartments. Qualitative matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) visualized 5-FU in selected samples.

RESULTS

Overall, AFXL enhanced and accelerated 5-FU uptake versus unexposed controls, with increased accumulation in deep skin layers (p < 0.01). While total, 24-hour 5-FU uptake in control skin was 0.096 mg/cm³ (0.19% of applied concentration), AFXL delivered up to 4.707 mg/cm³ (MAZ-DM; 9.41% uptake, 49-fold enhancement) (p = 0.002; 24 hours). Indicating accelerated delivery, 5-FU in laser-exposed samples at 4 hours was at least 10-fold that of 24-hour controls (p = 0.002). Deeper laser-channels increased delivery throughout the skin (MAZ-ED vs. MAZ-DM; p<0.01). MALDI-MSI confirmed enhanced, accelerated, deeper and more uniform 5-FU distribution after AFXL versus controls.

CONCLUSIONS

AFXL offers laser-channel depth-dependent, enhanced and accelerated 5-FU uptake, with increased deposition in deep skin layers.

Imaging mass spectrometry for accessing molecular changes during burn wound healing

The spatiotemporal analysis of the proteomic profile during human wound healing is a critical investigative step that can establish the complex interplay of molecular events that comprise the local response to burn injury. Partial-thickness wound samples with adjacent "normal" skin were collected from twenty-one patients with burn wounds and examined across a time spectrum ranging from the acute injury period at 3, 6, 11 days to the later hypertrophic scar period at 7 and 15 months. The techniques used for histology-directed tissue analyses highlighted inflammatory protein markers at the early time points after injury with diminished expression as burn wounds progressed into the proliferative phase. The datasets show the usefulness of MALDI MS and imaging mass spectrometry as discovery approaches to identify and map the cutaneous molecular sequence that is activated in response to the unique systemic inflammatory response following burn trauma. This information has the potential to define the unique factors that predispose human burn victims to disfiguring hypertrophic scar formation.