Biological therapy of strontium-substituted bioglass for soft tissue wound-healing: Responses to oxidative stress in ovariectomised rats.

The authors declare that they have no conflicts of interest concerning this article.International audienceNew synthetic biomaterials are constantly being developed for wound repair and regeneration. Bioactive glasses (BG) containing strontium have shown successful applications in tissue engineering account of their biocompatibility and the positive biological effects after implantation. This study aimed to assess whether BG-Sr was accepted by the host tissue and to characterize oxidative stress biomarker and antioxidant enzyme profiles during muscle and skin healing. Wistar rats were divided into five groups (six animals per group): the group (I) was used as negative control (T), after ovariectomy, groups II, III, IV and V were used respectively as positive control (OVX), implanted tissue with BG (OVX-BG), BG-Sr (OVX-BG-Sr) and presented empty defects (OVX-NI). Soft tissues surrounding biomaterials were used to estimate superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and malondialdehyde (MDA) concentration. Our results show that 60 days after operation, treatment of rats with BG-Sr significantly increased MDA concentration and caused an increase of SOD, CAT and GPx activities in both skin and muscular tissues. BG-Sr revealed maturation of myotubes followed a normal appearance of muscle regenerated with high density and mature capillary vessels. High wound recovery with complete re-epithelialization and regeneration of skin was observed. The results demonstrate that the protective action against reactive oxygen species (ROS) was clearly observed in soft tissue surrounding BG-Sr. Moreover, the potential use of BG-Sr rapidly restores the wound skin and muscle structural and functional properties. The BG advantages such as ion release might make BG-Sr an effective biomaterial choice for antioxidative activity

Multiscale Modeling of Complex Dynamic Problems: An Overview and Recent Developments

Multiscale modeling aims to solve problems at the engineering (macro) scale while considering the complexity of the microstructure with minimum cost. Generally, two scales are considered in multiscale modeling: small scale, which is designed to capture the mechanical phenomena at the atomistic, molecular or molecular cluster level, and large scale which is connected to continuous description. For each scale, well-established numerical methods have been developed over the years to handle the relevant phenomena. As a first part of this paper, the most popular numerical methods, used at different scales, as well as the coupling approaches between them are classified, according to their features and applications, so that the place of those used in multiscale modeling can be distinguished. Subsequently, the class of concurrent discrete–continuum coupling approaches, which is well adapted for dynamic studies of complex multiscale problems, is reviewed. Several techniques used in this class are also detailed. Among them, the bridging domain (BD) technique is used to develop a discrete–continuum coupling approach, adapted for dynamic simulations, between the Discrete Element Method and the Constrained Natural Element Method (CNEM). This approach is applied to study the BD coupling parameters in dynamics. Several results giving more light on the setting of these parameters in practice are obtained

Bioactive glasses functionalized with polyphenols: in vitro interactions with healthy and cancerous osteoblast cells

Bioactive glasses are widely studied as biomaterials for bone contact applications. In this research work, the opportunity to modify the surface of a bioactive glass with polyphenols (gallic acid, and natural polyphenols extracted from red grape skin and green tea leaves) has been investigated in order to induce a selective anti-tumor activity in vitro. The presence of surface grafted molecules has been optically proved by fluorescence microscopy exploiting their autofluorescence. Direct and indirect cytotoxicity assays have been performed with human bone osteosarcoma cells (U2OS) and human fetal pre-osteoblasts (hFOB), as well as the quantification of oxygen and nitrogen reactive species (RONS) engendered from cells in response to the materials. Finally, the DNA damage of U2OS cells upon contact with the bioactive glass has been evaluated in order to verify any selective cytotoxic activity of functionalized materials against cancer cells. Results showed a selective cytotoxic activity of functionalized bioactive glasses toward osteosarcoma cells that was particularly evident when cells were cultivated directly onto glasses surface. Moreover, the presence of grafted polyphenols increased the RONS production and induced a permanent DNA damage on the U2SOS cells while they promote a certain anti-inflammatory action toward hFOB. These preliminary results suggest polyphenols grafted bioactive glasses as promising material for bone substitution in cancer treatment