Ionic liquids-based processing of electrically conducting chitin nanocomposite scaffolds for stem cell growth

In the present study, we have successfully combined the biocompatible properties of chitin with the high electrical conductivity of carbon nanotubes (CNTs) by mixing them using an imidazolium-based ionic liquid as a common solvent/dispersion medium. The resulting nanocomposites demonstrated uniform distribution of CNTs, as shown by scanning electron microscopy (SEM) and optical microscopy. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction confirmed the α-crystal structure of chitin in the regenerated chitin nanocomposite scaffolds. Increased CNT concentration in the chitin matrix resulted in higher conductivity of the scaffolds. Human mesenchymal stem cells adhered to, and proliferated on, chitin/CNT nanocomposites with different ratios. Cell growth in the first 3 days was similar on all composites at a range of (0.01 to 0.07) mass fraction of CNT. However, composites at 0.1 mass fraction of CNT showed reduced cell attachment. There was a significant increase in cell proliferation using 0.07 mass fraction CNT composites suggesting a stem cell enhancing function for CNTs at this concentration. In conclusion, ionic liquid allowed the uniform dispersion of CNTs and dissolution of chitin to create a biocompatible, electrically conducting scaffold permissive for mesenchymal stem cell function. This method will enable the fabrication of chitin- based advanced multifunctional biocompatible scaffolds where electrical conduction is critical for tissue function

Histopathological observations of a polylactic acid-based device intended for guided bone/tissue regeneration

Background: Barrier devices have been shown to support alveolar bone and periodontal regeneration, a procedure also known as guided bone/tissue regeneration (GBR/GTR). Popular demand and clinical convenience have raised an interest in bioresorbable barrier devices. Tissue reactions to such bioresorbable devices are, however, generally not well explored. Purpose: The objective of this study was to evaluate short- and long-term tissue reactions following implantation of a bioresorbable polylactic acid (PLA)-based barrier device using a rat model. Materials and Methods: Twenty-one young adult male Sprague-Dawley rats were used. The animals were divided into three groups including 15 animals receiving the PLA device and animals serving as sham surgery (five) or nonoperated (one) controls. Using aseptic techniques, the PLA device was surgically implanted in direct contact with the calvarial bone. Animals receiving the PLA device were sacrificed at 3, 5, 7, and 12 months postsurgery to provide longitudinal histopathological observations of tissue and biomaterials reactions. Control animals were sacrificed at 3 months. Results: Animals were maintained without adverse events. Sham surgery and nonoperated control animals showed no signs of new bone formation or resorption, or signs of inflammatory reactions in adjoining soft tissues. In contrast, extensive amounts of residual biomaterial with evidence of foreign body reactions and bone resorption were observed in animals receiving the PLA device over 12 months. Conclusions: The results suggest that the PLA device may induce bone resorbing foreign body reactions. Importantly, the PLA device does not resorb within a 12-month healing interval. These biomaterials properties may influence new bone formation and maintenance when applying the device for GBR/GTR