Polydopamine treatment of chitosan nanofibers for the conception of osteoinductive scaffolds for bone reconstruction.

We report the influence of treatment time of electrospun chitosan nanofibers (CHT NFs) in dopamine hydrochloride bath (2 mg.mL-1 in 10 mM Tris buffer, pH 8.5) on the extent of the polydopamine (pDA) coating on NFs surface. The reaction was characterized by FTIR and SEM analysis and the cytocompatibility of the scaffolds toward MT3C3-E1 cells was assessed. Biomimetic deposition of hydroxyapatite (HA) in 1.5xSBF batch was investigated by SEM-EDS and XRD. Samples treated in dopamine bath during 2 h promoted the structural stability of NFs in PBS, provided optimal cytocompatibility and induced the in vitro biomineralization from 6 days in 1.5xSBF. The XRD and SEM-EDS investigations confirmed formation of spherical-shaped particles composed of apatitic phase. Finally, this study shows that these NFs-pDA scaffolds prepared in the optimal experimental conditions defined here are promising candidates for application as osteoinductive scaffolds for bone regeneration applied to orthopedic and dental applications.

[Dental stem cells: myth or hope in neuroregenerative medicine?] / Cellules souches dentaires : mythe ou espoir en médecine neurorégénératrice ?

The use of dental stem cells has raised many hopes in the development of new treatments for neurodegenerative diseases. According to current statistics, about 1 in 6 people in the world would be affected by a neurological disease. This number continues to increase as the world's population ages, making neurodegenerative diseases probably the one of the major challenges of public health in the 21st century. Neurodegenerative diseases are characterized mainly by a progressive loss of cognitive abilities and patient autonomy related to loss and degeneration of neurons in brain structures. Unfortunately, today, the only treatments available for this type of disease do only relieve the symptoms, they do not treat them, and few clinical trials have been truly convincing to date. Hence, hope lies for these diseases in the development of other therapeutic approaches. As such, dental stem cells could be a promising area of research because of their rapid growth, their great capacity for differentiation into different types of cells (among neuronal ones for some of them) and how easy they can be obtained, without raising ethical issues as for example for embryonic stem cells.

Sulfonated and sulfated chitosan derivatives for biomedical applications: A review.

From 20th century, chitosan, a natural polysaccharide, has received much attention for use in biomedical applications thanks to its remarkable properties, such as biodegradability, biocompatibility, hemostasis and antibacterial activity. Over the last decades, many researchers have attempted to generate new chitosan derivatives-based biomaterials though chemical modifications, especially through sulfonation or sulfation reactions in order to tailor the physicochemical and biochemical properties. Due to the presence of residual amino groups, the generated polyampholytic derivatives are characterized by convenient biological properties, such as antioxidation, antiviral activity, anticoagulation and bone regeneration, expanding their application scope. This paper provides an overview of the strategies used to chemically modify chitosan by introduction of sulfonate groups on chitosan backbone, focusing on various sulfonating or sulfating agents used and substitution regioselectivity, and highlights their applications in biomedical field.

Synthesis and characterization of polyampholytic aryl-sulfonated chitosans and their in vitro anticoagulant activity.

This work firstly aimed to synthesize mono- and di- sulfonic derivatives of chitosan by reductive amination reaction using respectively 2-formyl benzene sulfonic acid and 2,4 formyl benzene sulfonic acid sodium salts. The influence of the reactants molar ratio (R), aryl - substituted amino groups versus chitosan free amino groups, on the degree of substitution (DS) of both sulfonated chitosans was assessed by 1H NMR, elemental analysis, coupled conductometry-potentiometry analysis and UV spectrometry and FTIR. The influence of pH on sulfonated chitosans' properties in solution were investigated by solubility and zeta potential (ZP) studies, size exclusion chromatography equipped with MALLS detection (SEC-MALLS) and Taylor dispersion analysis (TDA). The polyampholytic character of both series was evidenced and strongly modified the solutions properties compared to chitosan. Then, the anticoagulant properties of mono- and di- sulfonic polymers were investigated by the measurement of the activated partial thromboplastin time (aPTT), Prothrombin-time (PT) and anti-(factor Xa).