Biotin-decorated anti-cancer nucleotide theranostic conjugate of human serum albumin: Where the seed meets the soil?

Human serum albumin is playing an increasing role as a drug carrier in clinical settings. Biotin molecules are often used as suitable tags in targeted anti-tumor drug delivery systems. We report on the synthesis and properties of a new multimodal theranostic conjugate based on an anti-cancer fluorinated nucleotide conjugated with a biotinylated dual-labeled albumin. Interestingly, in vitro and in vivo study revealed stronger anti-tumor activity of the non-tagged theranostic conjugate than that of the biotin-tagged conjugate, which can be explained by decreased binding of the biotin-tagged conjugate to cellular receptors. Our study sheds light on the importance of site-specific albumin modification for the design of albumin-based drugs with desirable pharmaceutical properties.     

间充质干细胞双标记光学成像的体内试验研究

目的:验证双标记生物发光成像活体观测MSCs在肝癌裸鼠模型向肿瘤病灶的趋化作用的可行性。方法:应用fluorescence(荧光)与bioluminescence(生物发光)两种成像方法,对MSCs进行CM-Di I荧光标记及对人肝癌细胞Hep G2进行Fluc-慢病毒感染并由此建立裸鼠肝癌模型,构建双标记成像系统,应用精诺真小动物光学成像仪在裸鼠肝癌模型中观测间充质干细胞向肿瘤的趋化作用。结果:在鼠尾静脉注射标记MSCs细胞后21天荧光成像可见MSCs主要积聚于肿瘤病灶处及肝脏。生物发光成像后可监测到病灶处由luciferase标记肿瘤细胞(Hep G2)发出荧光;将荧光成像与生物发光成像所得图像经后处理融合后,可见证间充质干细胞像肿瘤病灶定向迁徙的生物过程。经肿瘤病理切片证实间充质干细胞成功迁徙至肿瘤病灶中。结论:应用间充质干细胞双标记光学成像系统实现MSCs在活体内对肿瘤的趋化过程进行观测是可行的。这种成像方法可作为下一步以MSCs为载体的肿瘤基因治疗的有效监测手段。     

Exploring the in situ accessibility of small subunit ribosomal RNA of members of the domains Bacteria and Eukarya to oligonucleotide probes

The principle that the small subunit ribosomal RNA (ssu rRNA) is generally accessible to oligonucleotide probes designed to have high thermodynamic affinity was tested with Stenotrophomonas maltophilia, Rhodobacter sphaeroides, Bacillus subtilis, and Saccharomyces cerevisiae. Fluorescein-labeled probes, designed to have ΔG_overall° = −14 ± 1 and to avoid the potential of nucleobase-specific quenching, were used to target 20 randomly selected sites in each organism. A site was considered accessible if probe brightness was at least 10 times the background signal. With 30-h hybridizations, 71 out of 80 target sites passed the accessibility criterion. Three additional sites were demonstrated to be accessible with either longer hybridizations, which seemed to have a negative effect on some probes, or the addition of formamide to the hybridization buffer. The remaining 6 sites were demonstrated to be accessible by changing the fluorophore to Cy5, slightly modifying probe lengths, using dual-labeled fluorescein probes, or a combination of these approaches. Probe elongations were only needed in 4 probes, indicating a 95% success in correctly predicting ΔG_overall°, the key parameter for the design of high affinity probes. In addition, 94% of the fluorescein labeled probes yielded bright signals, demonstrating that nucleobase-specific quenching of fluorescein is an important factor affecting probe brightness that can be predicted during probe design. Overall, the results support the principle that with a rational design of probes, it is possible to make most target sites in the ssu rRNA accessible.