Improving cellular uptake and in vivo tumor suppression efficacy of liposomal oligonucleotides by urea as a chemical penetration enhancer

Cryoprotection in Human Mesenchymal Stromal/Stem Cells: Synergistic Impact of Urea and Glucose

Standard freezing protocols of clinically relevant cell lines commonly employ agents such as fetal bovine serum and dimethyl sulfoxide, which are a potential concern from both a regulatory and a patient safety perspective. The aim of this work was to develop formulations with safe and well tolerated excipients for the (cryo-) preservation of cell therapy products. We evaluated the cryoprotective capabilities of urea and glucose through measurements of cell metabolic activity. Freezing of clinically relevant human mesenchymal stromal/stem cells and human dermal fibroblasts at ≤ - 65°C at equimolar ratios of urea and glucose resulted in comparable viabilities to established dimethyl sulfoxide. Pre-incubation of human mesenchymal stromal/stem cells in trehalose and addition of mannitol and sucrose to the formulation further enhanced cell viability after freeze-thaw stress. Other cell types assessed (A549 and SK-N-AS) could not satisfactorily be preserved with urea and glucose, highlighting the need for tailored formulations to sustain acceptable cryopreservation.

The photodynamic/photothermal synergistic therapeutic effect of BODIPY-I-35 liposomes with urea

Phototherapy is a new treatment means for cancer which can reduce the side effects of traditional cancer treatments to humans. Urea is a naturally occurring metabolite in the human body. Some studies have shown that it can inhibit the proliferation of tumor cells and cause oxidative stress. In order to explore the application of urea in enhancing the phototherapy effect, we synthesized a new structure photosensitizer (BODIPY-I-35) with good phototherapeutic effect and encapsulated it in liposomes. Compared with free BODIPY-I-35, water-soluble nanoliposomes (LipoBOD) produced a huge redshift (> 122 nm) of fluorescence emission in solution. When LipoBOD was irradiated with 808 nm laser (1 W/cm²) for 10 min, the temperature contrast increased by 20 °C, which was 4 times higher than free BODIPY-I-35. Confocal microscopy showed appreciable accumulation of LipoBOD in HeLa cells. In addition, when LipoBOD was incubated with urea in HeLa cells, we found that urea not only obviously enhanced the production of ROS, but also increased the apoptosis of HeLa cells. The synergistic effect of LipoBOD (20 μg/mL, at BODIPY-I-35-eq) with urea (250 mM) showed significantly higher phototoxicity than LipoBOD alone. Low dose can reduce the cell viability to 10%. Therefore, we have obtained an effective method of using urea to enhance the phototherapy effect.