A comprehensive understanding of the transmembrane transport mechanisms and subcellular localization characteristics of tFNAs enables the rational design of smart drugs with subcellular targeting capabilities. Subcellular-targeted therapy represents a current research focus as it offers superior therapeutic advantages over conventional approaches by precisely directing therapeutic agents to specific organelles (
e.g., mitochondria, nuclei, and lysosomes) [
165,
166]. This approach significantly enhances drug concentration at target sites through ligand-guided accumulation in pathological organelles, enabling direct interventions in core disease mechanisms such as mitochondrial function restoration and gene expression modulation [
167]. The stimuli-responsive design facilitates controlled drug release in response to organelle-specific microenvironmental cues, thereby improving therapeutic specificity while minimizing off-target effects [
168]. Furthermore, subcellular precision delivery reduces systemic toxicity to healthy organelles and allows for real-time treatment monitoring by integrating diagnostic probes [
169]. Such strategies not only expand the therapeutic window but also enable multidimensional interventions for complex diseases, driving a paradigm shift in precision medicine from tissue-level to subcellular-scale applications. tFNAs have been explored as versatile drug carriers at the subcellular level to maximize therapeutic efficacy [
170]. Initial studies have shown that the early and rapid internalization of tFNAs is closely linked to the lysosomal pathway, which offers inherent advantages for passive lysosomal targeting. Inspired by the efficient uptake of tFNAs by macrophages
via the lysosomal pathway, Cai's team developed a dynamic lysosome-activated tFNA-based nanobox to completely encapsulate short interfering RNA (siRNA) [
32]. This nanobox undergoes conformational changes in response to the acidic lysosomal microenvironment, triggering siRNA release. Similarly, Fan's team used tFNAs to encapsulate zinc-responsive fluorophores, which were internalized
via the lysosomal pathway to monitor zinc ion concentrations in living cells (Fig. S9B in Supporting information) [
171]. Chen
et al. modified the four vertices of tFNAs with Pr-Cl, Pr-Ca, Pr-pH, and Cy5, respectively [
172]. Cy5 served as a stable reference signal, allowing for simultaneous
in situ detection of Cl
-, Ca
2+, and pH within lysosomes and facilitating the identification of lysosome subpopulations with distinct characteristics. Mitochondrial targeting using tFNAs functionalized with triphenylphosphine (TPP) has also been extensively studied (Fig. S9C in Supporting information). Chen
et al. utilized TPP-modified tFNAs to deliver a purine/apyrimidinic endonuclease 1 (APE1)-responsive molecular beacon, enabling the monitoring of APE1 levels in tumor cells to assess radiosensitivity [
164]. Yang
et al. employed this approach to dynamically construct G-quadruplexes using intracellular potassium ions, achieving controllable intracellular signal-driven assembly of tFNAs and mitochondrial function intervention [
34]. This created a polyanion barrier outside the mitochondria, blocking inter-organelle communication and limiting energy supply to tumor cells. Tang
et al. modified tFNAs with methyl sulfonamide groups to deliver glucose oxidase specifically to the endoplasmic reticulum, where the glucose consumption triggered the production of reactive oxygen species, inducing endoplasmic reticulum stress and enhancing cancer immunotherapy (Fig. S9D in Supporting information) [
162]. Additionally, Shao's team [
173] applied tFNAs at a more microscopic level. They developed a three-dimensional barcode system based on the tFNAs structure, termed STAMP, to measure the expression and subcellular distribution of various markers, including proteins, RNA, and metabolites. This method can theoretically provide over 10⁹ barcodes, meeting the requirements for high-throughput and high-sensitivity analysis of protein expression and spatial distribution. Collectively, these advances highlight the significant potential of subcellular-targeted tFNA-based therapeutics in enhancing drug efficacy, reducing side effects, and enabling personalized treatment, offering new avenues for research on tFNA applications.