Characterization of a hyaluronic acid-based hydrogel containing an extracellular oxygen carrier (M101) for periodontitis treatment: An in vitro study.

Periodontitis is an inflammatory disease associated with anaerobic bacteria leading to the destruction of tooth-supporting tissues. Porphyromonas gingivalis is a keystone anaerobic pathogen involved in the development of severe lesions. Periodontal treatment aims to suppress subgingival biofilms and to restore tissue homeostasis. However, hypoxia impairs wound healing and promotes bacterial growth within periodontal pocket. This study aimed to evaluate the potential of local oxygen delivery through the local application of a hydrogel containing Arenicola marina's hemoglobin (M101). To this end, a hydrogel (xanthan (2%), hyaluronic acid (1%)) containing M101 (1-2 g/L) (Xn(2%)-HA(1%)-M101) was prepared and characterized. Rheological tests revealed the occurrence of high deformation without the loss of elastic properties. Dialysis experiment revealed that incorporation of M101 within the gel did not modify its oxygen transportation properties. Samples of release media of the gels (1 g/L (10%) and 2 g/L (10%) M101) decreased significantly the growth of P. gingivalis after 24 h validating its antibacterial effect. Metabolic activity measurement confirmed the cytocompatibility of Xn(2%)-HA(1%)-M101. This study suggests the therapeutic interest of Xn(2%)-HA(1%)-M101 gel to optimize treatment of periodontitis with a non-invasive approach.

Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise.

A novel strictly anaerobic, hyperthermophilic archaeon, designated strain CDGST, was isolated from a deep-sea hydrothermal vent in the Cayman Trough at 4964m water depth. The novel isolate is obligate anaerobe and grows chemoorganoheterotrophically with stimulation of growth by sulphur containing compounds. Its growth is optimal at 75°C, pH 6.0 and under a pressure of 50MPa. It possesses the broadest hydrostatic pressure range for growth that has ever been described for a microorganism. Its genomic DNA G+C content is 51.11mol%. The novel isolate belongs to the genus Thermococcus. Phylogenetic analyses indicated that it is most closely related to Thermococcus barossii DSM17882T based on its 16S rRNA gene sequence, and to 'Thermococcus onnurineus' NA1 based on its whole genome sequence. The average nucleotide identity scores with these strains are 77.66% for T. barossii and 84.84% for 'T. onnurineus', respectively. Based on the draft whole genome sequence and phenotypic characteristics, strain CDGST is suggested to be separated into a novel species within the genus Thermococcus, with proposed name Thermococcus piezophilus (type strain CDGST=ATCC TSD-33T=UBOCC 3296T).