Making cellular probes more effective

Scientists at Indian Institute of Science, Bengaluru have found a way to enhance uptake of fluorescent probes into cells. They have found that by replacing hydrogen atoms at crucial places of napthalimide with iodine or bromide atoms makes it easier to break into cells. Napthalimide molecule shines under ultraviolet light by itself or when combined with any other molecule and hence is used as the fluorescent probe.

Fluorescent probes are used to detect molecules, monitor cellular activity and deliver drugs inside cells. Fluorescent probes based on naphthalimide are especially popular as they can easily be made in large quantities and their fluorescence can be tweaked by changing their constituent atoms. Besides they are not harmful like radioactive ones. However, they are usually absorbed by cells only in small quantities, which hampers their effectiveness.

Further investigation revealed that the two iodine atoms formed strong bonds with a transporter protein called MCT8 which then ferried the molecule into the cells. MCT8 is known to transport hormones such as thyroxine, into the cells. For example, thyroxine (T4), the hormone secreted by the thyroid gland, needs to be transported from the blood to inside the cell where it gets converted to T3, its functional form. That adding iodine increases cellular uptake suggests that biological compounds containing iodine probably use a similar transporter protein and mechanism to enter into cells.

Researchers led by Prof GovindaswamyMugeshfound that simply replacing two hydrogen atoms with iodine in their structure dramatically increased the amount of entering into mammalian cells. Almost 98% of all probes can enter the cell if iodine or bromine atoms are tagged to it.

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