Figure 1. (A) Images of dry 3D-printed collagen-based scaffolds after in situ reduction of Ag by different UV irradiation intervals. Dimensions of 3D-printed collagen-based scaffolds are 6 mm × 6 mm × 2 mm. (B) Schematic illustration of the mechanism of in situ AgNPs formation by using the UV irradiation method.

Figure 1. (A) Images of dry 3D-printed collagen-based scaffolds after in situ reduction of Ag by different UV irradiation intervals. Dimensions of 3D-printed collagen-based scaffolds are 6 mm × 6 mm × 2 mm. (B) Schematic illustration of the mechanism of in situ AgNPs formation by using the UV irradiation method.

Figure 2. SEM images of (A): Col-Ag0.05-2; (B): Col-Ag0.05-4; (C): Col-Ag0.05-6; (D): Col-Ag0.1-2; (E): Col-Ag0.1-4; (F): Col-Ag0.1-6. (G): Representative EDS analysis of Col-Ag.

Figure 2. SEM images of (A): Col-Ag0.05-2; (B): Col-Ag0.05-4; (C): Col-Ag0.05-6; (D): Col-Ag0.1-2; (E): Col-Ag0.1-4; (F): Col-Ag0.1-6. (G): Representative EDS analysis of Col-Ag.

Figure 3. TEM images of the AgNPs formed inside the 3D-printed collagen-based scaffolds. (A): Col-Ag0.05-2; (B): Col-Ag0.05-4; (C): Col-Ag0.05-6; (D): Col-Ag0.1-2; (E): Col-Ag0.1-4; (F): Col-Ag0.1-6. (G): schematic illustration of the variation of the size of the silver particles according to the place of the material where they are formed.

Figure 3. TEM images of the AgNPs formed inside the 3D-printed collagen-based scaffolds. (A): Col-Ag0.05-2; (B): Col-Ag0.05-4; (C): Col-Ag0.05-6; (D): Col-Ag0.1-2; (E): Col-Ag0.1-4; (F): Col-Ag0.1-6. (G): schematic illustration of the variation of the size of the silver particles according to the place of the material where they are formed.

Figure 4. FTIR spectra of Col, Col-Ag0.05 (A), and Col-Ag0.1 (B) after different time of UV light exposure (0 h, 2 h, 4 h, and 6 h).

Figure 4. FTIR spectra of Col, Col-Ag0.05 (A), and Col-Ag0.1 (B) after different time of UV light exposure (0 h, 2 h, 4 h, and 6 h).

Figure 5. Silver content in 3D-printed Col-Ag0.05 and Col-Ag0.1 scaffolds, after 2 h, 4 h, and 6 h of UV irradiation, measured by Atomic Absorption spectroscopy.

Figure 5. Silver content in 3D-printed Col-Ag0.05 and Col-Ag0.1 scaffolds, after 2 h, 4 h, and 6 h of UV irradiation, measured by Atomic Absorption spectroscopy.

Figure 6. DSC thermal analyses for 3D-printed Col (A), Col-Ag0.05 (B), and Col-Ag0.1 (C) scaffolds after different UV irradiation times.

Figure 6. DSC thermal analyses for 3D-printed Col (A), Col-Ag0.05 (B), and Col-Ag0.1 (C) scaffolds after different UV irradiation times.

Figure 7. Collagenase degradation test of 3D-printed collagen-based scaffolds. Weight percentage is shown as a function of time comparing Col with Col-Ag0.05 (A), and Col with Col-0.1 (B). Col-2(--●--blue), Col-4(--●--green), Col-6 (--●--red), Col-Ag0.05-2 (-■-blue), Col-Ag0.05-4 (-■-green), Col-Ag0.05-6 (-■-red), Col-Ag0.05-2 (-▲-blue), Col-Ag0.05-4 (-▲-green), and Col-Ag0.05-6 (-▲-red). Results are expressed as mean ± SD from triplicate experiments.

Figure 7. Collagenase degradation test of 3D-printed collagen-based scaffolds. Weight percentage is shown as a function of time comparing Col with Col-Ag0.05 (A), and Col with Col-0.1 (B). Col-2(--●--blue), Col-4(--●--green), Col-6 (--●--red), Col-Ag0.05-2 (-■-blue), Col-Ag0.05-4 (-■-green), Col-Ag0.05-6 (-■-red), Col-Ag0.05-2 (-▲-blue), Col-Ag0.05-4 (-▲-green), and Col-Ag0.05-6 (-▲-red). Results are expressed as mean ± SD from triplicate experiments.

Figure 8. Swelling capacity of Col-Ag0.05 (A) and Col-Ag0.1 (B). Col-2(--●--blue), Col-4(--●--green), Col-6 (--●--red), Col-Ag0.05-2 (-■-blue), Col-Ag0.05-4 (-■-green), Col-Ag0.05-6 (-■-red), Col-Ag0.05-2 (-▲-blue), Col-Ag0.05-4 (-▲-green), and Col-Ag0.05-6 (-▲-red). Results are expressed as mean ± SD from triplicate experiments.

Figure 8. Swelling capacity of Col-Ag0.05 (A) and Col-Ag0.1 (B). Col-2(--●--blue), Col-4(--●--green), Col-6 (--●--red), Col-Ag0.05-2 (-■-blue), Col-Ag0.05-4 (-■-green), Col-Ag0.05-6 (-■-red), Col-Ag0.05-2 (-▲-blue), Col-Ag0.05-4 (-▲-green), and Col-Ag0.05-6 (-▲-red). Results are expressed as mean ± SD from triplicate experiments.

Figure 9. Antimicrobial activity of 3D-printed Col and Col-Ag gels against E. coli. (A) Disk diffusion method. (B) Percentage of growth inhibition, evaluated by the dilution method.

Figure 9. Antimicrobial activity of 3D-printed Col and Col-Ag gels against E. coli. (A) Disk diffusion method. (B) Percentage of growth inhibition, evaluated by the dilution method.

Figure 10. Antimicrobial activity of silver in 3D-printed Col and Col-Ag gels against S. aureus. (A) Disk diffusion method. (B) Percentage of growth inhibition, evaluated by the dilution method.

Figure 10. Antimicrobial activity of silver in 3D-printed Col and Col-Ag gels against S. aureus. (A) Disk diffusion method. (B) Percentage of growth inhibition, evaluated by the dilution method.

Table 1. Size of AgNPs formed in situ, inside the 3D-printed collagen-based scaffolds.

Table 1. Size of AgNPs formed in situ, inside the 3D-printed collagen-based scaffolds.

SampleAgNPs Size (nm)Col-Ag0.05-226.17 ± 5.53Col-Ag0.05-427.70 ± 7.45Col-Ag0.05-624.39 ± 7.50Col-Ag0.1-212.02 ± 3.34Col-Ag0.1-49.74 ± 2.23Col-Ag0.1-610.18 ± 2.45