Abstract
We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue).
Highlights
We anticipated that the number of gold nanorods within our collagen hydrogels are similar to the evaluated concentration of 5.45 e-9 moles nanorods per liter
We did not anticipate any morphology changes to the gold nanorods due to NIR light exposure since our femtosecond laser operates in nJ energy per pulse range – morphology changes often occur at higher energy levels in the μ J or mJ ranges[18]
The described platform allows for the patterning of internal channels in collagen hydrogels in situ, in this case enabling endothelial recruitment, alignment, and tube formation
Summary
Collagen I, High Concentration (8.7 mg/mL) (VWR) was purchased. Gold nanroods were synthesized and using a seed-mediated growth and surface-modification methodology as previously described with some modifications. 7.5 mL 0.1 M of CTAB was mixed with 250 μ L 0.01 M HAuCl4, followed by addition of 600 μ L 0.01 NaBH4. The growth solution was prepared by mixing 40 mL of 0.1 M CTAB, 1.7 mL 0.01 M HAuCl4, 250 μ L of 0.01 AgNO3, and 270 μ L of 0.1 M L-ascorbic acid, followed by 420 μ L of the seed solution. Nanorods were surface modified by first centrifuging twice at 15,000 g, removing the supernatant and resuspending in diH2O, followed by adding mPEG-SH dropwise and allow to gently mix for 2 hours. Final nanorod concentration was determined to be 5.45 e-9 M by absorbance readings at its plasmon resonance (~800 nm)
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