[MR imaging of polyethylenimine-superparamagnetic iron oxide nanoparticle labeled bone marrow mesenchymal stem cells in vitro].

OBJECTIVE: To explore the optimal concentration of polyethylenimine-superparamagnetic iron oxide (PEI2k-SPIO) particles for labeling bone marrow mesenchymal stem cells (BMSCs) in vitro, then to demonstrate the imaging characteristics of the cells by 7.0-T MR scanner. The lowest cell quantity and the optimal cell quantity detected on MR was observed. METHODS: Cells at 2nd passage were inoculated into the 6-hole plate with cover glass. The different concentrations of PEI2k-SPIO (5 microg/mL, 7 microg/mL, 10 microg/mL, 15 microg/mL, 20 microg/mL) were added into different holes, respectively. After labeled with different concentrations of PEI2k-SPIO, the Prussian blue stain was used for determining the labeling efficiency. MTT growth curves were used to identify the activity of BMSCs and to determine the optimal threshold of SPIO nanocomposite particles labeled the stem cells at different PEI2k-SPIO concentrations (7, 10, 15, 20 microg Fe/mL medium). To definite the lowest cells quantity and the optimal observable cells quantity on MR imaging, 1 x 10(6), 1 x 10(5), 1 x 10(4) and 1 x 10(3) cells labeled with optimal threshold of PEI2k-SPIO and 1 x 10(6) cells unlabeled suspended in 0.2 mL agarose (10 g/L), respectively undergone MR scan. RESULTS: MTT growth curves showed the optimal threshold of PEI2k-SPIO labeled BMSCs was 7 microg/mL, which indicates has no adverse effects on the growth of stem cells. At the opimal concentration (7 microg Fe/mL), the lowest observable cell quantity of PEI2k-SPIO-labeled cells for MRI was 1 x 10(4), and the optimal observable cell quantity was 1 x 10(6). CONCLUSION: At the opimal concentration, adverse effect to stem cell activities had not be detected when were labeled with PEI2k-SPIO and the clearly image of MRI of labeled BMSCs could be obtained.

A self-healing PVDF-ZnO/MXene membrane with universal fouling resistance for real seawater desalination.

Seawater desalination is regarded as a possible way to overcome current shortages of fresh water, and membrane-based air humidification-dehumidification desalination (MHDD) represents a promising technique owing to its high-quality freshwater and cost-effectiveness; however, its development is restricted by membrane fouling. While a superhydrophobic membrane provides resistance to hydrophilic fouling, it remains susceptible to hydrophobic fouling. Here, a polyvinylidene fluoride-ZnO/MXene (PVDF-ZM) membrane, with a reversible conversion between superhydrophobicity and hydrophilicity was fabricated to achieve universal fouling resistance. It earned a competitive permeate flux (3.93 kg·m-2·h-1) and an excellent salt rejection (>99.5%). The membrane exhibited a strong anti-hydrophilic fouling ability, benefiting from its superhydrophobicity and rough surface. The adsorbed hydrophobic contaminants could desorb from the membrane surface under UV irradiation when transforming the surface wettability into hydrophilicity, exhibiting an anti-hydrophobic fouling ability. Subsequently, the membrane surface returned to the hydrophobic state under dark conditions. The membrane recovered 90% of the original permeation flux, while maintaining a salt rejection of >99.5%, thus realizing membrane self-healing. The PVDF-ZM membrane holds promise for sustainable desalination applications.