Evaluation of cell adhesion and osteoconductivity in bone substitutes modified by polydopamine.

Bones damaged due to disease or accidents can be repaired in different ways. Tissue engineering has helped with scaffolds made of different biomaterials and various methods. Although all kinds of biomaterials can be useful, sometimes their weakness in cellular activity or osteoconductivity prevents their optimal use in the fabrication of bone scaffolds. To solve this problem, we need additional processes, such as surface modification. One of the common methods is coating with polydopamine. Polydopamine can not only cover the weakness of the scaffolds in terms of cellular properties, but it can also create or increase osteoconductivity properties. Polydopamine creates a hydrophilic layer on the surface of scaffolds due to a large number of functional groups such as amino and hydroxyl groups. This layer allows bone cells to anchor and adheres well to the surfaces. In addition, it creates a biocompatible environment for proliferation and differentiation. Besides, the polydopamine coating makes the surfaces chemically active by catechol and amine group, and as a result of their presence, osteoconductivity increases. In this mini-review, we investigated the characteristics, structure, and properties of polydopamine as a modifier of bone substitutes. Finally, we evaluated the cell adhesion and osteoconductivity of different polydopamine-modified bone scaffolds.

Development and characterization of a DNA aptamer for MLL-AF9 expressing acute myeloid leukemia cells using whole cell-SELEX.

Current classes of cancer therapeutics have negative side effects stemming from off-target cytotoxicity. One way to avoid this would be to use a drug delivery system decorated with targeting moieties, such as an aptamer, if a targeted aptamer is available. In this study, aptamers were selected against acute myeloid leukemia (AML) cells expressing the MLL-AF9 oncogene through systematic evolution of ligands by exponential enrichment (SELEX). Twelve rounds of SELEX, including two counter selections against fibroblast cells, were completed. Aptamer pools were sequenced, and three candidate sequences were identified. These sequences consisted of two 23-base primer regions flanking a 30-base central domain. Binding studies were performed using flow cytometry, and the lead sequence had a binding constant of 37.5 + / - 2.5 nM to AML cells, while displaying no binding to fibroblast or umbilical cord blood cells at 200 nM. A truncation study of the lead sequence was done using nine shortened sequences, and showed the 5' primer was not important for binding. The lead sequence was tested against seven AML patient cultures, and five cultures showed binding at 200 nM. In summary, a DNA aptamer specific to AML cells was developed and characterized for future drug-aptamer conjugates.

Start-up of oxygen-limited autotrophic partial nitrification-anammox process for treatment of nitrite-free wastewater in a single-stage hybrid bioreactor.

This study presents effective ammonium removal from nitrite-free ammonium-rich synthetic wastewater through combined partial nitrification (PN) and anammox processes in a multi-zone hybrid airlift bioreactor (BioCAST). Removal efficiencies of ammonia-nitrogen and total nitrogen up to 85.6% and 81.2%, respectively, were achieved shortly after the start-up of bioreactor treating the nitrite-free ammonium-rich synthetic wastewater with ammonium concentrations of 10-350 mg/L. The hybrid (containing suspended and attached biomass) and multi-zone design of the bioreactor with different dissolved oxygen levels, along with the inoculation with anammox-containing sludge were the main factors in the successful start-up of the bioreactor. Nitrate accumulation problem due to the fast growth of nitrite-oxidizing bacteria in the bioreactor was controlled by two operating strategies including lowering the HRT from 4 days to 2 days and controlling the dissolved oxygen concentration in the aerobic zone of the bioreactor between 0.9 and 1.2 mg/L. Moreover, the 16S rRNA gene analysis confirmed that the partial nitrification of ammonia to nitrite occurred by Nitrosomonas sp. primarily in the suspended biomass in the aerobic zone, while the conversion of nitrite to N2 occurred by Candidatus Brocadia species in the anoxic zone. This study showed the effective removal of ammonium from a nitrite-free wastewater by providing a proper HRT, controlling the DO concentration between 0.9 and 1.2 mg/L in the aerobic zone, and preventing biomass loss using both suspended and attached microbial cultures in different zones of the bioreactor.