Héctor Flores

Hemocompatibility assessment of poly(2-dimethylamino ethylmethacrylate) (PDMAEMA)-based polymers

Poly(2-dimethylamino-ethylmethacrylate) (PDMAEMA), a cationic polymer, has been widely reported as a nonviral carrier. Despite the fact that the cytotoxicity of this polymer has been extensively studied, there is a lack of information about its blood compatibility. Hence, this work evaluates the hemocompatibility of free-form PDMAEMA homopolymers differing in molecular weight (Mw) with or without a poly(ethylene glycol) (PEG) sequence in the form of a palm tree-like structure. Poly(ethylenimine) (PEI) was used as a reference in order to compare its hemoreactivity. Hemagglutination, hemolysis, platelet number, blood coagulation, and the complement systems were assessed in normal human whole blood according to the ISO 10993-4. Results showed that Mw, concentration, and incubation time strongly affected the hemocompatibility of the polymers evaluated. Our in vitro observations highlight that PDMAEMA homopolymers interacted strongly with the surface of the red blood cells but not with the inner structure of the membrane, while PEI behaved in the opposite way. No clear correlation has been evidenced between PDMAEMA-induced hemagglutination, PEI-induced hemagglutination, and hemolysis. Interestingly, if these polyelectrolytes strongly affect the platelets and blood coagulation cascades in a dose dependent way, none of them significantly affects the complement system. Our work reveals new knowledge on the toxicology of 2 families of polycations largely explored for gene delivery and on their mechanisms of cellular and humoral interactions.

DPSC colonization of functionalized 3D textiles.

Fiber scaffolds are attractive materials for mimicking, within a 3D in vitro system, any living environment in which animal cells can adhere and proliferate. In three dimensions, cells have the ability to communicate and organize into complex architectures similar to those found in their natural environments. The aim of this study was to evaluate, in terms of cell reactivity, a new in vitro cell model: dental pulp stem cells (DPSCs) in a 3D polymeric textile. Scaffolds were knitted from polyglycolic acid (PGA) or polydioxanone (PDO) fibers differing in surface roughness. To promote cell adhesion, these hydrophobic fabrics were also functionalized with either chitosan or the peptide arginine-glycine-aspartic acid (RGD). Cell behavior was examined 1, 10, and 21 days post-seeding with a LIVE/DEAD® Kit. Confocal laser scanning microscopy (CLSM) highlighted the biocompatibility of these materials (cell survival rate: 94% to 100%). Fiber roughness was found to influence cell adhesion and viability significantly and favorably. A clear benefit of polymeric textile functionalization with chitosan or RGD was demonstrated in terms of cell adhesion and viability.

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity

Objective: This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). Material and Methods: An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). Results and Conclusions: Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system.

Evaluation of the Osteoblast Behavior to PGA Textile Functionalized with RGD as a Scaffold for Bone Regeneration

The new era of biomaterials for repairing bone tissue injury continues to be a challenge in bone tissue engineering. The fiber scaffolds allow for cellular interconnection and a microenvironment close to the bone extracellular matrix. The aim of this study was to evaluate the osteoblast behavior on a 3D textile of PGA (polyglycolic acid) fibers functionalized with the RGD (R: arginine; G: glycine; D: aspartic acid) peptide. The cell morphology, proliferation, and calcium phosphate deposition ability were evaluated on textiles at different time intervals under a confocal laser scanning microscope. The osteoblast viability ranged from 92% to 98%, and cell proliferation was higher in PGA-RGD than control PGA (uncoated). In addition, the osteoblast calcium phosphate deposition was significantly greater on PGA-RGD in osteogenic inductor medium (OIM) in contrast to controls without inducing factors. The PGA-RGD fibers supported proliferation and viability of osteoblast and stimulated bone osteogenesis and mineralization. These results support the adoption of this 3D polymeric textile as a scaffold for bone tissue engineering.

Evaluation of Decellularized Matrix and ß-Tricalcium Phosphate as Biomaterials for Bone Neoformation: In vivo Study

The aim of this study was to evaluate histologically the effect of two biomaterials, a biomaterial derived from porcine Urinary submucosa Bladder Matrix (UBM) and beta-TriCalcium Phosphate ( β-TCP), on bone defects. Twenty male New Zealand rabbits were used; the models were divided in two groups: the UBM group; the β-TCP group, and a Negative Control (NC) group. Fivemm defects were created in the femur of each model and then the different biomaterials were set in place depending on each grou p. At 4 and 8 weeks, the animals in the models were sacrificed and samples of the defect site were collected to perform a Hematoxylin a nd E sin stain (H&E). Histologically, β-TCP group at 4 and 8 weeks presented neoformation of bone-like and cartilage-like tissue, with the presence of inflammatory infiltrate; at 4 and 8 weeks, the UBM group presented neoformation of bone-like and cartilage-like tissue with a low presence of inflammatory infiltrate, and the NC group presented the formation of connective tissue and, in a low proporti n, neof rmation of bone tissue and cartilage. Both biomaterials, UBM and β-TCP, exhibited the capacity to promote bone neoformation; however, the UBM-based biomaterial produced a better-organized tissue with a lower inflammatory response compared with the β-TCP group.