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Among the different techniques to modify materials at the surface level, laser micromachining offers a versatile working route to alter the topography of a target in the micrometric scale. Femtosecond pulsed laser ablation (fs PLA) leads to minimal debris outcomes in comparison to longer pulse technologies, such as pico or nanosecond PLA. The briefness of the interaction conferred by fs PLA avoids heat transfer to the phonon network in the lattice, enabling a highly localised material removal [1]. This heat-hindered workflow is suitable for samples with low melting points such as biopolymers, with a great application in fields such as tissue engineering and personalised medicine [2]. Essentially, an increasing interest is being set to systems where surface modification could lead to novel cell responses in terms of adhesion, proliferation and mechanotransduction [3].
The need of precisely modify the surface of biopolymers lead us to employ fs PLA as an interesting approach avoiding the melting of the sample. This work motivates an exploration of ultrashort-pulse laser-matter interaction in polycaprolactone (PCL) scaffolds with the aim of analysing cell-substrate interactions.
Specifically, 4-layer PCL scaffolds were processed by laser with the STELA femtosecond laser, located at the L2A2 facilities in University of Santiago de Compostela. This laser supplies pulses of 35 fs duration, 1 kHz repetition rate and 1 mJ energy, with a central wavelength of 800 nm and a bandwidth of 80 nm. Microgrooves of two different widths were processed by modifying the power reaching the sample: 30 μm and 10 μm width (powers of 15 and 4.3 mW, respectively). Then, human dermal fibroblasts (HDF) and murine macrophages were seeded on the laser-ablated scaffolds and analysed after a 72-hour culture. It was seen that both cell lines were responsive to these micropatterns, resulting in a strong alignment of their cytoplasm and nucleus in the groove direction (Figure 1), as well as strongly increasing their adhesion compared to the control case.
Next steps are envisioned to relate the alignment of the cells with their mechanotransduction mechanisms (proregenerative macrophage M2 polarisation and HDF activation).
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