Simultaneous detection of various cancer cell types is another useful application of aptamer biosensors. This was achieved previously through optical means in vitro, by labeling the different 6-Fluoroquinaldine cancer cells with distinct aptamer-conjugated fluorescent NPs. Kang et al. conjugated three aptamers: AS1411 (targeting nucleolin), TTA1 (for tenascin-C), and MUC-1 (for mucin) with three QDs of distinct emission (605, 655, and 705 nm) to identify five cancer cell types based on the differential expression of their respective biomarkers [56]. Meanwhile, Chen et al. were able to simultaneously detect Ramos, CEM and Toledo cancer cells from a cell mixture, by applying three FRET NPs modified with distinct aptamer (TD05, Sgc8, and T1, respectively) [57]. As for PET/SPECT monitoring, aptamer conjugation has been used to enable control over the biodistribution of radio-isotope tracers. Previously, aptamers generated against activated neutrophil elastase NX21909 were labeled PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/10714611 with 99mTc, to monitor inflammatory events in a rat [58]. In a similar manner, an aptamer against tenascin-c (TTA1) was labeled with Rhodamine red and 99mTc to track glioblastoma (U251) and breast cancer (MDA-MB-436) cells. Following intravenous injection, the aptamer sensors showed rapid accumulation at tumor site within 10 minutes and diffused throughout 3 hours after. Therapid tumor uptake, in conjunction with rapid renal/ hepatic clearance, resulted in a high tumor to blood signal ratio ( 50 in 3 hours) [59]. Pieve et al. also explored the potential usage of antiMUC1-aptamers as a radiolabelling agent for breast cancer. Selected aptamers which were conjugated with MAG2 ligand and labeled with 99mTc, demonstrated great accumulation at the tumor site of MCF-7 tumor-bearing mice [60]. More recently, conjugation of the A10-3 RNA aptamer with 64Cu through several chelators was shown in vitro not to compromise A10-3 specificity towards PSMA positive tumor, therefore being another promising candidate for aptamer radiolabeling [61]. For cell tracking via X-ray/CT, findings that AuNP has greater X-ray absorption compared to iodine-based contrast agents with less tissue interference and cytotoxic effects have encouraged aptamer-AuNP probe utilization [62,63]. Kim et al. developed a bifunctional aptamer AuNP probe for combined prostate cancer imaging and treatment. 3-Bromo-tetrahydropyran Particularly, the A9 aptamer was extended to allow conjugation of a Dox loaded-21-nt (GCA)7 linker, with thiol modification for subsequent AuNP attachment. The NPs increased CT intensity by 4 folds in PSMA positive LNCaP cells when compared to control PC3 cells, indicating a promising selective CT contrast agent [64]. This report showcases the potential of achieving an integrative aptamer probe to promote drug localization as well. Similarly, magnetic NP-aptamer conjugates are promising candidates in MRI. For example, Ko et al. conjugatedWiraja et al. Molecular and Cellular Therapies 2014, 2:33 http://www.molcelltherapies.com/content/2/Page 5 ofFigure 3 (See legend on next page.)Wiraja et al. Molecular and Cellular Therapies 2014, 2:33 http://www.molcelltherapies.com/content/2/Page 6 of(See figure on previous page.) Figure 3 Activatable aptamer probe (AAP) for in vivo cancer tracking. A) Schematic showing the mechanism of AAP recognition against CCRF-CEM cells. Upo.
Qigong intelligently uses precise hand
postures, smooth movements, and timed
breathing to amplify light/magnetism
that emits from our body.
postures, smooth movements, and timed
breathing to amplify light/magnetism
that emits from our body.