Modulating the Biomechanical Properties of Engineered Connective Tissues by Chitosan-Coated Multiwall Carbon Nanotubes

A Review on Carbon Nanotubes Family of Nanomaterials and Their Health Field

The use of carbon nanotubes (CNTs), which are nanometric materials, in pathogen detection, protection of environments, food safety, and in the diagnosis and treatment of diseases, as efficient drug delivery systems, is relevant for the improvement and advancement of pharmacological profiles of many molecules employed in therapeutics and in tissue bioengineering. It has contributed to the advancement of science due to the development of new tools and devices in the field of medicine. CNTs have versatile mechanical, physical, and chemical properties, in addition to their great potential for association with other materials to contribute to applications in different fields of medicine. As, for example, photothermal therapy, due to the ability to convert infrared light into heat, in tissue engineering, due to the mechanical resistance, flexibility, elasticity, and low density, in addition to many other possible applications, and as biomarkers, where the electronic and optics properties enable the transduction of their signals. This review aims to describe the state of the art and the perspectives and challenges of applying CNTs in the medical field. A systematic search was carried out in the indexes Medline, Lilacs, SciELO, and Web of Science using the descriptors "carbon nanotubes", "tissue regeneration", "electrical interface (biosensors and chemical sensors)", "photosensitizers", "photothermal", "drug delivery", "biocompatibility" and "nanotechnology", and "Prodrug design" and appropriately grouped. The literature reviewed showed great applicability, but more studies are needed regarding the biocompatibility of CNTs. The data obtained point to the need for standardized studies on the applications and interactions of these nanostructures with biological systems.

The Formation of Self-Assembled Nanoparticles Loaded with Doxorubicin and d-Limonene for Cancer Therapy

Self-assembled nanoparticles present unique properties that have potential applications in the development of a successful drug delivery system. Doxorubicin (DOX) is an important anti-neoplastic anthracycline chemotherapeutic drug widely described. However, it suffers from serious dose-dependent cardiotoxicity. d-Limonene is a major constituent of numerous citrus oils that is considered a specific monoterpene against free radicals producing antioxidant activity. Herein, we aimed to design three types of self-assembled nanodelivery systems (nanoemulsion, niosomes, and polylactide nanoparticles) for loading both DOX and d-limonene to enhance the solubilization of d-limonene and provide antioxidant activity with excellent anticancer activity. As confirmed by dynamic light scattering and transmission electron microscopy, the nanoparticles were prepared successfully with diameter sizes of 52, 180, and 257 nm for the DOX-loaded nanoemulsion, niosomes, and polylactide nanoparticles, respectively. The zeta potential values were above -30 mV in all cases, which confirms the formation of stable nanoparticles. The loading efficiency of DOX was the highest in the case of the DOX-loaded nanoemulsion (75.8%), followed by niosomes (62.8%), and the least was in the case of polylactide nanoparticles with a percentage of 50.2%. The in vitro release study of the DOX-loaded nanoparticles showed a sustained release profile of doxorubicin with the highest release in the case of DOX-loaded PDLLA nanoparticles. The kinetic release model for all developed nanoparticles was the Peppas-Sahlin model, demonstrating DOX release through Fickian diffusion phenomena. Moreover, all developed nanoparticles maintain the antioxidant activity of d-limonene. The cytotoxicity study of the DOX-loaded nanoparticles showed concentration-dependent anticancer activity with excellent anticancer activity in the case of the DOX-loaded nanoemulsion and polylactide nanoparticles. These nanoparticles will be further studied in vivo to prove the cardioprotective effect of d-limonene in combination with DOX.

Noncovalent functionalization of carbon nanotubes as a scaffold for tissue engineering

Tissue engineering is one of the hot topics in recent research that needs special requirements. It depends on the development of scaffolds that allow tissue formation with certain characteristics, carbon nanotubes (CNTs)-collagen composite attracted the attention of the researchers with this respect. However, CNTs suffer from low water dispersibility, which hampered their utilization. Therefore, we aim to functionalize CNTs non-covalently with pyrene moiety using an appropriate hydrophilic linker derivatized from polyethylene glycol (PEG) terminated with hydroxyl or carboxyl group to disperse them in water. The functionalization of the CNTs is successfully confirmed by TEM, absorption spectroscopy, TGA, and zeta potential analysis. 3T3 cells-based engineered connective tissues (ECTs) are generated with different concentrations of the functionalized CNTs (f-CNTs). These tissues show a significant enhancement in electrical conductivity at a concentration of 0.025%, however, the cell viability is reduced by about 10 to 20%. All ECTs containing f-CNTs show a significant reduction in tissue fibrosis and matrix porosity relative to the control tissues. Taken together, the developed constructs show great potential for further in vivo studies as engineered tissue.