An octopus-shaped nanomachine hijacks tumor ATP leakage to power a self-amplifying cycle of membrane damage, drug delivery, and metabolic collapse in cancer cells.
(Nanowerk Spotlight) Cancer cells fuel their survival through continuous production and controlled release of adenosine triphosphate (ATP), the molecule that powers nearly all energy-dependent processes in living cells. This metabolic hyperactivity sustains rapid proliferation, invasion, immune evasion, and the reshaping of surrounding tissue. Most therapeutic strategies aimed at disrupting cancer’s energy supply have focused on blocking the internal production machinery, targeting glycolysis or mitochondrial oxidative phosphorylation.
Yet cancer cells are metabolically flexible. They reroute energy pathways when one is blocked, restoring ATP levels and rendering the intervention temporary. A critical dimension of tumor bioenergetics has gone largely unexploited: the movement of ATP across the plasma membrane itself.
Tumor cells release ATP into the extracellular space at rates far exceeding those of healthy cells, creating steep concentration gradients between the cell interior and its surroundings. This gradient has been tapped for stimulus-responsive drug delivery, where nanocarriers open and release their payload in ATP-rich environments. But these approaches tend to suffer from rapid local ATP depletion, burst-release kinetics, and compensatory metabolic resistance.
Building on a growing body of work using DNA nanomachines that combine molecular sensing with photodynamic cancer therapy, researchers developed an octopus-shaped biomimetic nanomachine, designated HSA-ABC, that anchors to tumor cell membranes and initiates a feedforward loop of ATP depletion and drug release, driving a tumor-selective bioenergetic crisis.
Schematic illustration of nano-octopus, HSA-(ABC)x, and its responsive mechanism. (A) Assembly of nano-octopus HSA-(ABC)x. The nanostructure is composed of a maleimide-modified HSA serving as the “octopus head” and a thiolated-DNA assembly, ABC “octopus arm” through a thiol-ene reaction. The cholesterol and Ce6 double-modified C strand linked to the arm strand provides the plasma membrane anchoring and photodynamic therapy basis for the nano-octopus. The B strand, an ATP aptamer modified with BHQ2, facilitates DOX loading and acts as a controlled photodynamic switch for nano-octopus via fluorescence resonance energy transfer (FRET) between BHQ2-Ce6. (B) Local schematic illustration of the nano-octopus dynamic response to ATP, as described in the main text: (I) Membrane anchoring and ATP-triggered activation. (II) Photodynamic membrane disruption upon irradiation. (III) Enhanced DOX internalization. (IV) Apoptosis induction and subsequent ATP release. (V) Feedback amplification via released ATP. (Image: Reproduced with permission from Wiley-VCH Verlag) (click on image to enlarge)
The nanomachine has two main components. The “head” is a human serum albumin (HSA) protein core. The “arms” are DNA assemblies carrying three functional elements: cholesterol anchors for membrane insertion, the photosensitizer chlorin e6 (Ce6) for light-activated generation of reactive oxygen species, and an ATP-sensing aptamer that acts as a molecular switch. The anticancer drug doxorubicin (DOX) is loaded into the DNA structure. Each nanomachine carries roughly five arms with approximately 15 cholesterol-based membrane binding sites.
The key design principle is that the aptamer switch keeps Ce6 inactive until ATP is present. In its default state, a quencher molecule suppresses Ce6 through energy transfer. When extracellular ATP binds the aptamer, the quencher is displaced and Ce6 becomes photoactive, ensuring the nanomachine activates selectively in the ATP-rich tumor microenvironment.
The therapeutic cycle then unfolds in coordinated steps. First, the multivalent cholesterol anchors insert into the tumor cell’s plasma membrane, gripping the lipid bilayer much like an octopus’s suckers. The multivalent construct bound MCF-7 breast cancer cells roughly six times more tightly than single-cholesterol controls, with a dissociation constant of 0.36 µM versus 2.32 µM. Co-localization studies confirmed stable membrane association for up to 8 hours, resisting endocytic internalization.
Once anchored and activated by tumor-derived ATP, irradiation at 660 nm drives Ce6 to generate singlet oxygen, which damages the plasma membrane. The resulting pores allow rapid influx of DOX, bypassing slow conventional endocytosis. DOX reached the nucleus within 15 minutes, and experiments with various endocytic inhibitors confirmed that entry occurred through membrane damage rather than through traditional uptake pathways.
Inside the cell, DOX triggers apoptosis, activating cytochrome c release and caspase-3 cleavage, hallmarks of the intrinsic cell death pathway. Crucially, apoptosis stimulates mitochondrial ATP efflux, driving a surge of ATP into the extracellular space. This released ATP activates additional locked Ce6 modules on the cell surface, restarting the cycle. Each round amplifies membrane damage, accelerates drug influx, and deepens ATP depletion.
The system’s tumor selectivity arises from this ATP dependency. Normal cells, with lower extracellular ATP concentrations and less active membrane efflux, fail to trigger the aptamer switch strongly enough to initiate the cascade. When either the photodynamic or chemotherapy component was removed, extracellular ATP levels remained unchanged and tumor cell killing was negligible. With both active, the nanomachine achieved 65% tumor cell lethality within 4 hours.
Beyond cell killing, the combined treatment reshaped the molecular landscape of tumor cells in ways that neither membrane disruption nor apoptosis alone could achieve. Transcriptomic analysis identified 856 differentially expressed genes relative to controls, with pronounced downregulation of genes governing plasma membrane integrity and extracellular matrix organization, alongside upregulation of immune activation and oxidative phosphorylation pathways.
The metabolic profile diverged just as sharply. The combined treatment group produced 1,395 differentially expressed metabolites, with central carbon metabolism in cancer identified as a key disrupted pathway. Elevated lactate dehydrogenase release and increased expression of damage-associated molecular patterns, including HSP70 and HMGB1, pointed to immunogenic cell death triggered by the membrane damage. Single-action groups showed markedly reduced metabolic disruption, confirming that the synergy between both mechanisms drives the bioenergetic collapse.
In MCF-7 tumor-bearing mice, the complete HSA-ABC system combined with laser irradiation markedly suppressed tumor growth. Without DOX, tumors grew nine-fold. Without laser activation, they grew seven-fold, only marginally less than saline-treated controls. The full system showed no significant toxicity to major organs, and hemolysis assays confirmed biocompatibility.
This work reframes transmembrane ATP flux as a therapeutic target rather than a passive byproduct of cellular stress. Where conventional metabolic therapies attempt to shut down internal energy production, an effort readily circumvented by cancer’s metabolic flexibility, this approach turns the tumor’s own ATP efflux against it. The feedforward design ensures that the therapeutic effect intensifies over time rather than diminishing as the drug is consumed.
The strategy could potentially extend to other membrane-disrupting agents such as oncolytic peptides or pore-forming toxins, and the immunogenic cell death signatures suggest possible synergies with checkpoint immunotherapy. By bridging DNA nanotechnology, protein engineering, and cancer metabolism, the nano-octopus opens a route toward therapeutics that exploit, rather than simply inhibit, the metabolic adaptability of malignant cells.
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