Enhanced mechanical and photoluminescence effect of poly(l-lactide) reinforced with functionalized multiwalled carbon nanotubes

A computational study of mechanical properties of collagen-based bio-composites

Studying changes in collagen deformation behavior at the nanoscale due to variations in mineralization and hydration is important for characterizing and developing collagen-based bio-composites. Recent studies also find that carbon nanotubes (CNTs) show promise as a reinforcing material for collagenous bio-composites. Currently, the effects of variation in mineral, water, and CNT content on collagen gap and overlap region mechanics during compression is unexplored. We use molecular dynamics simulations to investigate how variations in mineral, water, and CNT contents of collagen bio-composites in compression change their deformation behavior and thermal properties. Results indicate that variations in mineral and water content affect the collagen structure due to expansion or contraction of the gap and overlap regions. The deformation mechanisms of the gap and overlap regions also change. The presence of CNTs in non-mineralized collagen reduces the deformation of the gap region and increases the bio-composite elastic modulus to ranges comparable to mineralized collagen. The collagen/CNT bio-composites are also determined to have a higher specific heat than the studied mineralized collagen bio-composites, making them more likely to be resistant to thermal damage that could occur during implantation or functional use of a collagen collagen/CNT bio-composite biomaterial.

Carbon Nanotubes in Biomedicine

Nowadays, biomaterials have become a crucial element in numerous biomedical, preclinical, and clinical applications. The use of nanoparticles entails a great potential in these fields mainly because of the high ratio of surface atoms that modify the physicochemical properties and increases the chemical reactivity. Among them, carbon nanotubes (CNTs) have emerged as a powerful tool to improve biomedical approaches in the management of numerous diseases. CNTs have an excellent ability to penetrate cell membranes, and the sp² hybridization of all carbons enables their functionalization with almost every biomolecule or compound, allowing them to target cells and deliver drugs under the appropriate environmental stimuli. Besides, in the new promising field of artificial biomaterial generation, nanotubes are studied as the load in nanocomposite materials, improving their mechanical and electrical properties, or even for direct use as scaffolds in body tissue manufacturing. Nevertheless, despite their beneficial contributions, some major concerns need to be solved to boost the clinical development of CNTs, including poor solubility in water, low biodegradability and dispersivity, and toxicity problems associated with CNTs' interaction with biomolecules in tissues and organs, including the possible effects in the proteome and genome. This review performs a wide literature analysis to present the main and latest advances in the optimal design and characterization of carbon nanotubes with biomedical applications, and their capacities in different areas of preclinical research.

The Preparation, Characterization, Mechanical and Antibacterial Properties of GO-ZnO Nanocomposites with a Poly(l-lactide)-Modified Surface

Graphene oxide (GO) was employed for the preparation of GO-zinc oxide (ZnO). The hydroxyl group on the surface was exploited to trigger the l-lactide ring-opening polymerization. A composite material with poly(l-lactide) (PLLA) chains grafted to the GO-ZnO surface, GO-ZnO-PLLA, was prepared. The results demonstrated that the employed method allowed one-step, rapid grafting of PLLA to the GO-ZnO surface. The chemical structure of the GO surface was altered by improved dispersion of GO-ZnO in organic solvents, thus enhancing the GO-ZnO dispersion in the PLLA matrix and the interface bonding with PLLA. Subsequently, composite films, GO-ZnO-PLLA and GO-ZnO-PLLA/PLLA, were prepared. The changes in interface properties and mechanical properties were studied. Furthermore, the antibacterial performance of nano-ZnO was investigated.

Functionalization of Graphene Oxide with Low Molecular Weight Poly (Lactic Acid)

In this paper, the hydroxyl groups on the surface of graphene oxide (GO) were used to initiate the ring-opening polymerization of a lactic acid O-carboxyanhydride. GO grafted with poly (l-lactic acid) molecular chains (GO-g-PLLA) was prepared. Lactic acid O-carboxyanhydride has a higher polymerization activity under mild polymerization conditions. Thus, the functionalization of the polymer chains and obtaining poly (lactic acid) (PLLA) was easily achieved by ring-opening polymerization with 4-dimethylaminopyridine (DMAP) as the catalyst. The results showed that with this method, PLLA can be rapidly grafted to the surface of GO in one step. As a result, the chemical structure of the GO surface was altered, improving its dispersion in organic solvents and in a PLLA matrix, as well as its bonding strength with the PLLA interface. We then prepared GO/PLLA and PLLA/GO-g-PLLA composite materials and investigated the differences in their interfacial properties and mechanical properties. GO-g-PLLA exhibited excellent dispersion in the PLLA matrix and formed excellent interfacial bonds with PLLA through mechanical interlocking, demonstrating a significant enhancement effect compared to PLLA. The water vapor and oxygen permeabilities of the GO-g-PLLA/PLLA composite decreased by 19% and 29%, respectively.

A free radical assisted strategy for preparing functionalized carbon nanotubes as a highly efficient nucleating agent for poly(l-lactide)

Schematic illumination of the fabrication of the CNT-OEG via free radical polymerization.