G-quadruplex-modulated nanoplatform triggers a Ca²⁺ storm via the mitochondria-associated endoplasmic reticulum membrane for anti-melanoma multimodal therapy.

Abstract

Endoplasmic reticulum (ER)-mitochondria interplay shapes tumor fate, with Ca²⁺ homeostasis serving as a critical node linking these organelles. Here, we engineered a TTO photosensitizer (PS) that recognizes G-quadruplex (G4) in mitochondria through conformationally restricted π-π interactions, thereby potentiating photodynamic therapy (PDT)-mediated interference with Ca²⁺ homeostasis. Hemin was electrostatically co-assembled with TTO and hyaluronic acid-polyethyleneimine (HA-PEI) copolymer to generate lethal hydroxyl radicals (·OH) that magnify PDT-induced oxidative damage, while the HA-PEI component enables tumor-specific delivery. With this synergy, TTO-Hemin@HA-PEI (TH@HP) propagates PDT influence to provoke ER stress and dysregulate the inositol 1,4,5-trisphosphate receptor (IP₃R)-glucose regulator protein 75 (GRP75)-voltage-dependent anion channel 1 (VDAC1)-mitochondrial calcium uniporter (MCU) Ca²⁺-transfer axis at the mitochondria-associated ER membrane (MAM), leading to MAM remodeling. This self-amplifying pathological loop is characterized by persistent ER Ca²⁺ leakage to mitochondria and cytoplasm via MAM, which impairs adenosine triphosphate (ATP) synthesis, disables energy-dependent Ca²⁺ feedback regulation, and ignites a systemic Ca²⁺ storm, thereby activating markers of immunogenic cell death (ICD) and converting mitochondrial damage into pro-immunogenic signals that drive melanoma immune infiltration. Collectively, this effort reveals a feed-forward mechanism between mitochondrial impairment and ER-driven ICD, offering a compelling paradigm for mitochondria-targeted multimodal therapies. STATEMENT OF SIGNIFICANCE: In this contribution, a multimodal anti-melanoma nanoplatform was engineered to follow the causal chain: G-quadruplex (G4) coupling and biocatalytic reactions-photodynamic therapy (PDT) amplification-Ca²⁺ storm-immune response activation. It has verified that existing mitochondrial-targeted immunogenic cell death (ICD) involves a mechanism where single organelle stimulus while multiple organelles execute responses. Furthermore, a functional association exists between mitochondrial damage and endoplasmic reticulum-driven ICD through mitochondria-associated endoplasmic reticulum membrane (MAM). Simultaneously, this research furnishes comprehensive theoretical and experimental evidence for PDT amplification mechanism following G4 interaction. It is the first time in our known research that rationale and advantages of G4 targeting in PDT applications have been proposed, and we believe it will carry substantial reference for subsequent studies.