# Y-shaped trivalent aptamer for targeted visualization and tracking of reprogrammed astrocytes

## TL;DR

A new DNA-based tool was developed to specifically identify and track astrocytes, offering a faster and more accurate imaging method.

## Contribution

A novel trivalent DNA aptamer was engineered for specific and rapid astrocyte visualization and tracking.

## Key findings

- The trivalent aptamer Tri-ΔAst17-30 enables rapid and specific endocytosis in astrocytes.
- The aptamer shows strong binding to astrocytic glioblastoma cells but minimal binding to glial glioblastoma cells.
- It allows longitudinal monitoring of astrocyte conversion into induced neural precursor cells.

## Abstract

Despite extensive research into the diverse transformations and functions of astrocytes, conventional fluorescence immunohistochemistry for their distinct identification remains challenging and time-consuming, primarily due to the lack of cell surface binders specific to these glial cells. To address this limitation, we developed a specific and straightforward imaging strategy for primary astrocytes using cell surface-targeting aptamers. We identified a novel anti-astrocyte DNA aptamer (designated Ast17-30) through a 17-round cell-SELEX process incorporating magnetic-activated cell sorting, designed to bypass the technical hurdles of SELEX when applied to short-lived cells. To enhance binding affinity, we further engineered this aptamer into a Y-shaped trimer (Tri-ΔAst17-30), enabling clear discrimination between astrocytes and neurons. Consequently, the engineered trivalent aptamer facilitated rapid astrocyte-specific endocytosis within minutes due to its increased binding avidity. This capability enabled longitudinal monitoring of astrocyte conversion into induced neural precursor cells, observing moderate pro-inflammatory gene expression in their transcriptomic profiles. Furthermore, Tri-ΔAst17-30 bound strongly to astrocytic glioblastoma cells (U87MG), with minimal binding to glial glioblastoma cells (C6), confirming specificity for astrocytic tumor cells. Given the current absence of reliable live-astrocyte-specific imaging techniques, we propose that this trivalent anti-astrocyte DNA aptamer has potential for investigating developmental pathways and targeted therapy of these crucial glial cells.

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