Photothermal interaction of a 1927 nm Thulium laser with MatriDerm: an in vitro study

Dermal templates support wound healing, yet complex wounds remain challenging. Thermal lasers activate regenerative heat shock pathways through the heat shock response (HSR), but their interaction with dermal substitutes is unclear. MatriDerm^®, a non-cross-linked collagen-elastin substitute used in single-stage reconstruction, may be enhanced by laser applications to improve regenerative outcomes. This study evaluated the interaction between a 1927 nm Thulium laser and MatriDerm^® under different hydration states. MatriDerm^® scaffolds (Thickness 1-3 mm) were tested in dry, water-soaked and blood-soaked conditions (n = 27). Samples received 1927 nm Thulium laser exposure (20 mJ/ pulse, 10 J/cm², 1 mm spot, five pulses/ site). Macroscopic and microscopic effects, peak temperatures, and charring depth were documented. Blood-soaked scaffolds underwent quantitative polymerase chain reaction (PCR), western blot, enzyme-linked immunosorbent assay (ELISA) and Fourier-transform infrared (FTIR) analysis. Laser effects occurred only in blood-soaked MatriDerm^®. Dry and water-soaked scaffolds showed no structural change and minimal temperature rise (28-32 °C). Blood-soaked samples reached 65 ± 5 °C, producing superficial carbonisation (250 ± 50 μm), with preserved deeper matrix. Molecular analysis showed HSP70 upregulation, reduced transforming growth factor β1 signalling, increased collagen I expression, and collagen reorganisation. Effects reflected local thermal confinements within blood-rich microdomains rather than bulk absorption at 1927 nm, whereas water alone dissipated heat too rapidly to sustain a photothermal response. 1927 nm Thulium laser produces a distinct photothermal response in the presence of blood, suggesting an altered local optical-thermal environment. These findings support laser-activated dermal scaffolds and provide a mechanistic basis for future in vivo studies exploring Thulium laser-assisted wound healing.