توصيفگر ها :
پلي(اِل لاكتيد كو كاپرولاكتون) , محبوس سازي فيزيكي , چاپ سه بعدي , مهندسي بافت , ژلاتين , داربست مهندسي بافت , كوپليمريزاسيون حلقه گشا
چكيده انگليسي :
In contemporary research endeavors dedicated to tissue regeneration, tissue engineering scaffolds have proven their efficacy in addressing and rectifying tissue damage. The structure and mechanical properties of these scaffolds provide a suitable basis for the growth and proliferation of cells. Due to the fact that tissue engineering scaffolds are constructed from biological materials, they possess characteristics such as hydrophilicity, biocompatibility, porous architecture, and desirable mechanical properties. Synthetic polymers such as polycaprolactone and poly(lactic acid) are among the commonly used polymers in the fabrication of tissue engineering scaffolds. Additionally, the coexistence of these two polymers imparts desirable mechanical properties for scaffold construction. However, one of the challenges associated with this category of synthetic polymer materials is their limited hydrophilicity, which is not conducive to suitable cell growth. Therefore, the use of a natural polymer such as gelatin can address this deficiency. In this project, to achieve printability and attain suitable mechanical properties, the synthesis of poly(l-lactide-co-caprolactone) (PLCL) copolymer was undertaken. The ring-opening copolymerization process was carried out at a temperature of 140 °C, utilizing a molar ratio of 50/50 for lactide/caprolactone monomers over a period of 24 h. For characterization purposes, FTIR, HNMR, GPC, DSC, DTG, and TGA tests were employed. The FTIR spectroscopy revealed stretching vibrations of carbonyl (C=O) at 1727 cm⁻¹ (attributed to the poly(lactic acid) section) and 1691 cm⁻¹ (attributed to the polycaprolactone section). Furthermore, the presence of the lactide-caprolactone linkage in the HNMR test was confirmed by peaks at 2.3, 4.05, and 5.34 ppm. Another indication of the correct synthesis process is the change in the glass transition temperature, shifting from 20 ℃ in PCL to 12 ℃ in PLCL. The melting and degradation temperatures measured for PLCL were approximately 58 °C and 352 °C, respectively. The viscoelastic behavior of shear thinning was observed in the rheometry test in PLCL. Moreover, for the design of tissue engineering scaffolds, 3D printing of the desired copolymer was carried out using the Taguchi method. The printing conditions were optimized at a temperature of 130 ℃, pressure of 0.9 bar, and a speed of 70 mm/min. Surface modification was achieved through the physical entrapment of gelatin, where a 50/50 volume ratio of water to acetone was selected, and samples were examined at two-time intervals, 10 and 90 min. In order to characterize the surface modification, FTIR, contact angle, tensile testing, and SEM were employed. Peaks observed at 1646 cm⁻¹ and 1549 cm⁻¹ in the FTIR test in the spectra of PLCL after 10 min and PLCL after 90 min of swelling indicate the functional groups of gelatin. Additionally, the contact angle decreased with increasing swelling time in the gelatin solution, reducing from 95.8⁰ in the pure copolymer to 69.1⁰ after 90 min of swelling in gelatin. The mechanical properties of the gelatin-modified samples showed a significant increase. The tensile strength of pure PLCL samples was 5.03±1.05 MPa, and with surface modification using gelatin for 90 min, it increased to 7±0.86 MPa. The porosity size of PLCL scaffolds was approximately 16.38±5.34 µm. SEM images during the 90 min swelling period revealed a higher level of gelatin penetration on the surface. In conclusion, the cell viability percentage of pure PLCL on days 1, 3, and 5 was 96.88±2.67%, 99.21±15.86%, and 97.10±5.35%, respectively. For PLCL90, the viability was 103.08±1.72%, 111.26±4.65%, and 110.22±7% on the respective days. Furthermore, the cell growth capability in the first and fifth days was demonstrated in both pure and modified samples in SEM images. The cell density in the modified samples was higher than that in the pure samples.
