Overcoming the inhibitory effects of urea to improve the kinetics of microbial-induced calcium carbonate precipitation (MICCP) by Lysinibacillus sphaericus strain MB284.

Among different microbial-induced calcium carbonate precipitation (MICCP) mechanisms utilized for biomineralization, ureolysis leads to the greatest yields of calcium carbonate. Unfortunately, it is reported that urea-induced growth inhibition can delay urea hydrolysis but it is not clear how this affects MICCP kinetics. This study investigated the impact of urea addition on the MICCP performance of Lysinibacillus sphaericus MB284 not previously grown on urea (thereafter named bio-agents), compared with those previously cultured in urea-rich media (20 g/L) (hereafter named bio-agents+ or bio-agents-plus). While it was discovered that initial urea concentrations exceeding 3 g/L temporarily hindered cell growth and MICCP reactions for bio-agents, employing bio-agents+ accelerated the initiation of bacterial growth by 33% and led to a 1.46-fold increase in the initial yield of calcium carbonate in media containing 20 g/L of urea. The improved tolerance of bio-agents+ to urea is attributed to the presence of pre-produced endogenous urease, which serves to reduce the initial urea concentration, alleviate growth inhibition, and expedite biomineralization. Notably, elevating the initial concentration of bio-agents+ from OD600 of 0.01 to 1, housing a higher content of endogenous urease, accelerated the initiation of MICCP reactions and boosted the ultimate yield of biomineralization by 2.6 times while the media was supplemented with 20 g/L of urea. These results elucidate the advantages of employing bio-agents+ with higher initial cell concentrations to successfully mitigate the temporary inhibitory effects of urea on biomineralization kinetics, offering a promising strategy for accelerating the production of calcium carbonate for applications like bio self-healing of concrete.

Mimicking the Acute Myeloid Leukemia Niche for Molecular Study and Drug Screening.

Bone marrow niche is a major contributing factor in leukemia development and drug resistance in acute myeloid leukemia (AML) patients. Although mimicking leukemic bone marrow niche relies on two-dimensional (2D) culture conditions, it cannot recapitulate complex bone marrow structure that causes introduction of different three-dimensional (3D) scaffolds. Simultaneously, microfluidic platform by perfusing medium culture mimic interstitial fluid flow, along with 3D scaffold would help for mimicking bone marrow microenvironment. In this study TF-1 cells were cocultured with bone marrow mesenchymal stem cells (BM-MSCs) in 2D and 3D microfluidic devices. Phenotype maintenance during cell culture and proliferation rate was assayed and confirmed by cell cycle analysis. Morphology of cells in 2D and 3D culture conditions was demonstrated by scanning electron microscopy. After these experiments, drug screening was performed by applying azacitidine and cytarabine and cytotoxicity assay and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for B cell lymphoma 2 (BCL2) were done to compare drug resistance in 2D and 3D culture conditions. Our result shows leukemic cells in 3D microfluidic device retaining their phenotype and proliferation rate was significantly higher in 3D culture condition in comparison to 2D culture condition (p < 0.05), which was confirmed by cell cycle analysis. Cytotoxicity assay also illustrated drug resistance in 3D culture condition and qRT-PCR demonstrated higher BCL2 expression in 3D microfluidic device in contrast to 2D microfluidic device (p < 0.05). On balance, mimicking bone marrow niche would help the target therapy and specify the role of niche in development of leukemia in AML patients.