A Redox-Activatable Fluorescent Sensor for the High-Throughput Quantification of Cytosolic Delivery of Macromolecules

Engineered aptamers for molecular imaging

Molecular imaging, including quantification and molecular interaction studies, plays a crucial role in visualizing and analysing molecular events occurring within cells or organisms, thus facilitating the understanding of biological processes. Moreover, molecular imaging offers promising applications for early disease diagnosis and therapeutic evaluation. Aptamers are oligonucleotides that can recognize targets with a high affinity and specificity by folding themselves into various three-dimensional structures, thus serving as ideal molecular recognition elements in molecular imaging. This review summarizes the commonly employed aptamers in molecular imaging and outlines the prevalent design approaches for their applications. Furthermore, it highlights the successful application of aptamers to a wide range of targets and imaging modalities. Finally, the review concludes with a forward-looking perspective on future advancements in aptamer-based molecular imaging.

Elucidation of Protonation Cooperativity of a STING-Activating Polymer

Stimuli-responsive nanomaterials have the potential to improve the performance and overcome existing barriers of conventional nanotherapeutics. Molecular cooperativity design in stimuli-responsive nanomedicine can amplify physiological signals, enabling a cooperative response for improved diagnostic and therapeutic precision. Previously, this work reported an ultra-pH-sensitive polymer, PEG-b-PC7A, that possesses innate immune activating properties by binding to the stimulator of interferon genes (STING) through polyvalent phase condensation. This interaction enhances STING activation and synergizes with the endogenous STING ligand for robust cancer immunotherapy. Despite its successes in innate immune activation, the fundamental physicochemical and pH-responsive properties of PC7A require further investigation. Here, this study elucidates the protonation cooperativity driven by the phase transition of PC7A copolymer. The highly cooperative system displays an "all-or-nothing" proton distribution between highly charged unimer (all) and neutral micelle (nothing) states without gradually protonated intermediates. The binary protonation behavior is further illustrated in pH-precision-controlled release of a representative anticancer drug, β-lapachone, by PC7A micelles over a noncooperative PE5A polymer. Furthermore, the bimodal distribution of protons is represented by a high Hill coefficient (nH  > 9), featuring strong positive cooperativity. This study highlights the nanoscale pH cooperativity of an immune activating polymer, providing insights into the physicochemical characterization and design parameters for future nanotherapeutics development.

Compartmentalized Nano-MOFs as Co-delivery Systems for Enhanced Antitumor Therapy

Therapeutic bioactive macromolecules hold great promise in cancer therapy, but challenges such as low encapsulation efficiency and susceptibility to inactivation during the targeted co-delivery hinder their widespread applications. Compartmentalized nano-metal-organic frameworks (nMOFs) can easily load macromolecules in the innermost layer, protect them from the outside environment, and selectively release them in the target location after stimulation, showing great potential in the co-delivery of biomacromolecules. Herein, the rationally designed (GOx + CAT)/ZIF-8@BSATPZ/ZIF-8 (named GCZ@BTZ) nMOFs with compartmentalized structures are employed to deliver cascaded enzymes and the chemotherapeutic drug tirapazamine (TPZ)-conjugated bovine serum albumin (BSATPZ). Benefiting from the compartmentalized structure and protective shell, the GCZ@BTZ system is stable during blood circulation and preferentially accumulates in the tumor. Furthermore, in response to the acidic tumor environment, GCZ@BTZ effectively released the loading enzymes and BSATPZ. Along with the tumor starvation caused by depletion of glucose, cascaded reactions could also contribute to the enhancement of tumor hypoxia, which further activated BSATPZ-based chemotherapy. Notably, in the mouse tumor models, GCZ@BTZ treatment significantly inhibits tumor survival and metastasis. Such a compartmentalized nMOF delivery system presents a promising avenue for the efficient delivery of bioactive macromolecules.

Recent Advancements on Self-Immolative System Based on Dynamic Covalent Bonds for Delivering Heterogeneous Payloads

The precisely spatial-temporal delivery of heterogeneous payloads from a single system with the same pulse is in great demand in realizing versatile and synergistic functions. Very few molecular architectures can satisfy the strict requirements of dual-release translated from single triggers, while the self-immolative systems based on dynamic covalent bonds represent the "state-of-art" of ultimate solution strategy. Embedding heterogeneous payloads symmetrically onto the self-immolative backbone with dynamic covalent bonds as the trigger, can respond to the quasi-bio-orthogonal hallmarks which are higher at the disease's microenvironment to simultaneously yield the heterogeneous payloads (drug A/drug B or drug/reporter). In this review, the modular design principles are concentrated to illustrate the rules in tailoring useful structures, then the rational applications are enumerated on the aspects of drug codelivery and visualized drug-delivery. This review, hopefully, can give the general readers a comprehensive understanding of the self-immolative systems based on dynamic covalent bonds for delivering heterogeneous payloads.

Recent advances in the intracellular delivery of macromolecule therapeutics

This review summarizes the uptake pathway of intracellular delivery vehicles for macromolecule therapeutics, and provides in-depth discussions and prospects about intracellular delivery of macromolecule therapeutics.

Protein Binding and Release by Polymeric Cell-Penetrating Peptide Mimics

There is significant potential in exploiting antibody specificity to develop new therapeutic treatments. However, intracellular protein delivery is a paramount challenge because of the difficulty in transporting large, polar molecules across cell membranes. Cell-penetrating peptide mimics (CPPMs) are synthetic polymers that are versatile materials for intracellular delivery of biological molecules, including nucleic acids and proteins, with superior performance compared to their natural counterparts and commercially available peptide-based reagents. Studies have demonstrated that noncovalent complexation with these synthetic carriers is necessary for the delivery of proteins, but the fundamental interactions dominating CPPM-protein complexation are not well understood. Beyond these interactions, the mechanism of release for many noncovalent carriers is not well established. Herein, interactions expected to be critical in CPPM-protein binding and unbinding were explored, including hydrogen bonding, electrostatics, and hydrophobic interactions. Despite the guanidinium-rich functionality of these polymeric carriers, hydrogen bonding was shown not to be a dominant interaction in CPPM-protein binding. Fluorescence quenching assays were used to decouple the effect of electrostatic and hydrophobic interactions between amphiphilic CPPMs and proteins. Furthermore, by conducting competition assays with other proteins, unbinding of protein cargoes from CPPM-protein complexes was demonstrated and provided insight into mechanisms of protein release. This work offers understanding toward the role of carrier and cargo binding and unbinding in intracellular outcomes. In turn, an improved fundamental understanding of noncovalent polymer-protein complexation will enable more effective methods for intracellular protein delivery.

Polyvalent design in the cGAS-STING pathway

Polyvalent interactions mediate the formation of higher-order macromolecular assemblies to improve the sensitivity, specificity, and temporal response of biological signals. In host defense, innate immune pathways recognize danger signals to alert host of insult or foreign invasion, while limiting aberrant activation from auto-immunity and cellular senescence. Of recent attention are the unique higher-order assemblies in the cGAS-STING pathway. Natural stimulation of cGAS enzymes by dsDNA induces phase separation and enzymatic activation for switchlike production of cGAMP. Subsequent binding of cGAMP to STING induces oligomerization of STING molecules, offering a scaffold for kinase assembly and signaling transduction. Additionally, the discovery of PC7A, a synthetic polymer which activates STING through a non-canonical biomolecular condensation, illustrates the engineering design of agonists by polyvalency principles. Herein, we discuss a mechanistic and functional comparison of natural and synthetic agonists to advance our understanding in STING signaling and highlight the principles of polyvalency in innate immune activation. The combination of exogenous cGAMP along with synthetic PC7A stimulation of STING offers a synergistic strategy in spatiotemporal orchestration of the immune milieu for a safe and effective immunotherapy against cancer.

Ultrasound lighting up AIEgens for potential surgical navigation

Multifunctional contrast-enhanced agents suitable for application in surgical navigation by taking advantage of the merits of their diverse imaging modalities at different surgical stages are highly sought-after. Herein, an amphipathic polymer composed of aggregation-induced emission fluorogens (AIEgens) and Gd³⁺ chelates was successfully synthesized and assembled into ultrasound responsive microbubbles (AIE-Gd MBs) to realize potential tri-modal contrast-enhanced ultrasound (US) imaging, magnetic resonance imaging (MRI), and AIEgen-based fluorescence imaging (FI) during the perioperative period. Through ultrasound targeted microbubble destruction (UTMD) and cavitation effect, the as-prepared AIE-Gd MBs went through a MBs-to-nanoparticles (NPs) conversion, which not only resulted in targeted accumulation in tumor tissues but also led to stronger fluorescence being exhibited due to the more aggregated AIE-Gd molecules in the NPs. As a proof-of-concept, our work proposes a strategy of US-lit-up AIEgens in tumors which could offer a simple and powerful tool for surgical navigation in the future.

Harnessing Endogenous Stimuli for Responsive Materials in Theranostics

Materials that respond to endogenous stimuli are being leveraged to enhance spatiotemporal control in a range of biomedical applications from drug delivery to diagnostic tools. The design of materials that undergo morphological or chemical changes in response to specific biological cues or pathologies will be an important area of research for improving efficacies of existing therapies and imaging agents, while also being promising for developing personalized theranostic systems. Internal stimuli-responsive systems can be engineered across length scales from nanometers to macroscopic and can respond to endogenous signals such as enzymes, pH, glucose, ATP, hypoxia, redox signals, and nucleic acids by incorporating synthetic bio-inspired moieties or natural building blocks. This Review will summarize response mechanisms and fabrication strategies used in internal stimuli-responsive materials with a focus on drug delivery and imaging for a broad range of pathologies, including cancer, diabetes, vascular disorders, inflammation, and microbial infections. We will also discuss observed challenges, future research directions, and clinical translation aspects of these responsive materials.

Understanding the Polymer Rearrangement of pH-Responsive Nanoparticles

The use of self-assembled nanoparticles for drug delivery has received significant attention in recent years. However, the dynamic nature of self-assembled polymeric systems means there is a need to develop greater understanding of the inherent stability of these systems. In particular, understanding if these materials remain as discrete nanoparticles, or if there is dynamic exchange of material between particles is critical. Herein, we labelled pH-responsive nanoparticles with fluorescent dyes and then investigated the change in fluorescence when the particles were mixed with unlabelled nanoparticles in order to investigate their potential for polymer rearrangement. Nanoparticles were formed by the nanoprecipitation of pH-responsive poly(ethylene glycol)-block-poly(2-(diethylamino)ethyl methacrylate) (PEG-b-PDEAEMA) as the shell and poly(2-(diethylamino)ethyl methacrylate)-random-poly(2-(diisopropylamino)ethyl methacrylate) (PDEAEMA-r-PDPAEMA) as the core. The core and shell were labelled by incorporating pentafluorophenyl methacrylate (PFPMA) in core or shell respectively and then coupling with either Sulfo-cyanine5 amine or Cyanine3 amine. Exchange of material between nanoparticles was probed by tracking changes in the self-quenching of fluorescently labelled polymers in the core of the nanoparticles. The fluorescence intensity of the labelled nanoparticles was stable when mixed with unlabelled nanoparticles at physiological pH (pH 7.4), suggesting there is limited migration of polymers between particles in this system. This study provides important insights into the use of non-crosslinked nanoparticles under biologically relevant conditions.

Antigen folding improves loading efficiency and antitumor efficacy of PC7A nanoparticle vaccine

Cancer vaccines hold great promise to produce antigen-specific T cell immunity for personalized therapy of cancer. Previously, we reported an ultra-pH-sensitive nanoparticle, PC7A, capable of priming an efficacious immune response without significant systemic toxicity. Despite the early success, the relationship between antigen properties and encapsulation efficiency for downstream immune activation remains poorly understood. In this study, we investigated a small library of melanoma antigens and the effects of several formulation methods on the efficiency of peptide loading inside PC7A nanoparticles. Results show loading efficiency is not highly dependent on the formulation methods, but instead mainly driven by the peptide antigen properties. In particular, we identified a phase transition event, namely the folding of antigenic peptides from random coils to α-helical structure, is important for antigen loading inside PC7A nanoparticles. Mutation of a peptide that abrogates the formation of helical structure resulted in poor loading efficiency. Antitumor efficacy studies in melanoma-bearing mice demonstrate the importance of peptide loading in vaccine-induced antitumor immunity. This study highlights the contribution of phase transition of peptide antigens on vaccine formulation in order to make widespread use of personalized nanoparticle vaccines feasible.

Nano-Immune-Engineering Approaches to Advance Cancer Immunotherapy: Lessons from Ultra-pH-Sensitive Nanoparticles

Immunotherapy has transformed the field of oncology and patient care. By leveraging the immune system of the host, immunostimulatory compounds exert a durable, personalized response against the patient's own tumor. Despite the clinical success, the overall response rate from current therapies (e.g., immune checkpoint inhibitors) remains low (∼20%) because tumors develop multiple resistance pathways at molecular, cellular, and microenvironmental levels. Unlike other oncologic therapies, harnessing antitumor immunity requires precise activation of a complex immunological system with multiple levels of regulation over its function. This requires the ability to exert control over immune cells in both intracellular compartments and various extracellular sites, such as the tumor microenvironment, in a spatiotemporally coordinated fashion.The immune system has evolved to sense and respond to nano- and microparticulates (e.g., viruses, bacteria) as foreign pathogens. Through the versatile control of composition, size, shape, and surface properties of nanoparticles, nano-immune-engineering approaches are uniquely positioned to mount appropriate immune responses against cancer. This Account highlights the development and implementation of ultra-pH-sensitive (UPS) nanoparticles in cancer immunotherapy with an emphasis on nanoscale cooperativity. Nanocooperativity has been manifested in many biological systems and processes (e.g., protein allostery, biomolecular condensation), where the system can acquire emergent properties distinct from the sum of individual parts acting in isolation.Using UPS nanoparticles as an example, we illustrate how all-or-nothing protonation cooperativity during micelle assembly/disassembly can be leveraged to augment the cancer-immunity cycle toward antitumor immunity. The cooperativity behavior enables instant and pH-triggered payload release and dose accumulation in acidic sites (e.g., endocytic organelles of antigen presenting cells, tumor microenvironment), intercepting specific immunological and tumor pathophysiological processes for therapy. These efforts include T cell activation in lymph nodes by coordinating cytosolic delivery of tumor antigens to dendritic cells with simultaneous activation of stimulator of interferon genes (STING), or tumor-targeted delivery of acidotic inhibitors to reprogram the tumor microenvironment and overcome T cell retardation. Each treatment strategy represents a nodal intervention in the cancer-immunity cycle, featuring the versatility of UPS nanoparticles. Overall, this Account aims to highlight nanoimmunology, an emerging cross field that exploits nanotechnology's unique synergy with immunology through nano-immune-engineering, for advancing cancer immunotherapy.

Exploiting nanoscale cooperativity for precision medicine

Precise spatiotemporal control of molecular transport is vital to functional physiological systems. Nature evolved to apply macromolecular cooperativity to achieve precision over systemic delivery of important molecules. In drug delivery, conventional nanocarriers employ inert materials and rely on passive accumulation for tissue targeting and diffusion for drug release. Early clinical studies show these nanodrugs have not delivered the anticipated impact on therapy. Inspired by nature, we propose a design principle that incorporates nanoscale cooperativity and phase transition to sense and amplify physiological signals to improve the therapeutic outcome. Using ultra-pH-sensitive (UPS) nanoparticles as an example, we demonstrate how all-or-nothing protonation cooperativity during micelle assembly/disassembly can be exploited to increase dose accumulation and achieve rapid drug release in acidic microenvironments. In a separate study, we show the effectiveness of a single polymer composition to accomplish cytosolic delivery of tumor antigens with activation of stimulator of interferon genes (STING) in lymph node-resident dendritic cells for cancer immunotherapy. Molecular cooperativity is a hallmark of nanobiology that offers a valuable strategy to functionalize nanomedicine systems to achieve precision medicine.

Disulfide-containing Macromolecules for Therapeutic Delivery

Development of macromolecules provides applicable platforms for the delivery of therapeutics. In this general overview, we focus on the design principles of synthetic polymers, with disulfide bonds located in either the polymer backbone or side chains. We also discuss the role of disulfide bonds, as well as the remaining questions to better understand their applications in therapeutic delivery systems.

Recent Development of pH-Responsive Polymers for Cancer Nanomedicine

Cancer remains a leading cause of death worldwide with more than 10 million new cases every year. Tumor-targeted nanomedicines have shown substantial improvements of the therapeutic index of anticancer agents, addressing the deficiencies of conventional chemotherapy, and have had a tremendous growth over past several decades. Due to the pathophysiological characteristics that almost all tumor tissues have lower pH in comparison to normal healthy tissues, among various tumor-targeted nanomaterials, pH-responsive polymeric materials have been one of the most prevalent approaches for cancer diagnosis and treatment. In this review, we summarized the types of pH-responsive polymers, describing their chemical structures and pH-response mechanisms; we illustrated the structure-property relationships of pH-responsive polymers and introduced the approaches to regulating their pH-responsive behaviors; we also highlighted the most representative applications of pH-responsive polymers in cancer imaging and therapy. This review article aims to provide general guidelines for the rational design of more effective pH-responsive nanomaterials for cancer diagnosis and treatment.

The Endosomal Escape of Nanoparticles: Toward More Efficient Cellular Delivery

Many emerging therapies rely on the delivery of biological cargo into the cytosol. Nanoparticle delivery systems hold great potential to deliver these therapeutics but are hindered by entrapment and subsequent degradation in acidic compartments of the endo/lysosomal pathway. Engineering polymeric delivery systems that are able to escape the endosome has significant potential to address this issue. However, the development of safe and effective delivery systems that can reliably deliver cargo to the cytosol is still a challenge. Greater understanding of the properties that govern endosomal escape and how it can be quantified is important for the development of more efficient nanoparticle delivery systems. This Topical Review highlights the current understanding of the mechanisms by which nanoparticles escape the endosome, and the emerging techniques to improve the quantification of endosomal escape.

A sequence-activated AND logic dual-channel fluorescent probe for tracking programmable drug release

The translation of biomarker sensing into programmable diagnostics or therapeutic applications in vivo is greatly challenging, especially for eliminating the 'false positive' signals from OR logic gates. Herein we present a sense-of-logic dual-channel nanoprobe, operating through a sequence-activated AND logic gate by responding ultra-sensitively to pH changes and being subsequently triggered with biothiol for the controllable release of anti-cancer drugs. Specifically, programmable drug release is conducted in a multistage tumor microenvironment (acidic endocytic organelles followed by abnormal glutathione-overexpressing cell cytosol), which is synchronous with dual-channel near-infrared (NIR) fluorescence output. This approach represents the merging of sensing and release, including logically enabled molecular design, biomarker sensing, and controllable drug release. Impressively, the sequential AND logic feature within an unprecedented framework provides feedback on the diversity and complexity of biological milieu, along with remarkably enhancing the tumor therapeutic efficiency via its precise targeting ability and programmable drug release.

In Vivo and in Situ Activated Aggregation-Induced Emission Probes for Sensitive Tumor Imaging Using Tetraphenylethene-Functionalized Trimethincyanines-Encapsulated Liposomes

The design and exploration of fluorescent probes with high-sensitivity and low-background are essential for noninvasive optical molecular imaging. The in vivo and in situ activated aggregation-induced emission (AIE) probes were found to be ideal for achieving higher signal-to-background ratios for tumor detections. We herein developed novel tetraphenylethene-encapsulated liposomes (TPE-LPs) constructed by loading TPE-trimethincyanine into liposomes for the first time, and the probes were applied to tumor bioimaging in vivo. TPE-functionalized trimethincyanines were synthesized with a new and efficient one-pot reaction. In TPE-LPs, TPE-functionalized bicarboxylic acids benzoindole trimethinecyanine (TPE-BICOOH) fluorophores were found to be well dispersed in lipid bilayers (with non-restricted rotation) during the blood circulation, and then aggregated (with restriction of intramolecular rotation) upon liposome rupture in the tumor tissue, achieving a low-background and high-target signal for tumor imaging. The in situ activated AIE probes not only had great accumulation at the tumor site after intravenous injection in 4T1 tumor-bearing mice but also demonstrated excellent signal-to-background ratios, as well as low cytotoxicity and excellent biocompatibility. The proposed strategy is believed to be a simple and powerful tool for the sensitive detection of tumors.

pH-responsive Drug Delivery Systems

Acidic microenvironments exist in selected organs, tissues, and subcellular compartments, as well as in many dysregulated pathological states. A continuous effort has been made to harness the unique acidic properties of biological tissues for site-specific delivery of drugs. Various pH-responsive drug delivery systems have been designed and developed with improved spatio-temporal control of payload delivery with enhanced efficacy. This chapter will focus on the recent advances in the development of pH-sensitive materials, mechanisms of payload release, and pH-triggered drug targeting in various biomedical applications.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Cooperativity Principles in Self-Assembled Nanomedicine

Nanomedicine is a discipline that applies nanoscience and nanotechnology principles to the prevention, diagnosis, and treatment of human diseases. Self-assembly of molecular components is becoming a common strategy in the design and syntheses of nanomaterials for biomedical applications. In both natural and synthetic self-assembled nanostructures, molecular cooperativity is emerging as an important hallmark. In many cases, interplay of many types of noncovalent interactions leads to dynamic nanosystems with emergent properties where the whole is bigger than the sum of the parts. In this review, we provide a comprehensive analysis of the cooperativity principles in multiple self-assembled nanostructures. We discuss the molecular origin and quantitative modeling of cooperative behaviors. In selected systems, we describe the examples on how to leverage molecular cooperativity to design nanomedicine with improved diagnostic precision and therapeutic efficacy in medicine.

Optical molecular imaging for tumor detection and image-guided surgery

We have witnessed rapid development of fluorescence molecular imaging of solid tumors for cancer diagnosis and image-guided surgery in the past decade. Many biomarkers unique to cancer cells or tumor microenvironment, such as cell surface receptors, hypoxia, secreted proteases and extracellular acidosis have been characterized, and can be used to distinguish cancer from normal tissue. A variety of optical imaging probes have been developed to target these biomarkers to improve tumor contrast over the background tissue. Unlike conventional anatomical and molecular imaging technologies, fluorescent imaging method benefits from its safety, high-spatial resolution and real-time capability, and therefore, has become a highly adoptable imaging method for tumor detection and image-guided surgery in clinics. In this review, we summarize recent progress in 'always-ON' and stimuli-activatable fluorescent imaging probes, and discuss their potentials in tumor detection and image-guided surgery.

Innate Immune Activation by cGMP-AMP Nanoparticles Leads to Potent and Long-Acting Antiretroviral Response against HIV-1

HIV-1 evades immune detection by the cGAS-STING cytosolic DNA-sensing pathway during acute infection. STING is a critical mediator of type I IFN production, and STING agonists such as cGMP-AMP (cGAMP) and other cyclic dinucleotides elicit potent immune and antitumor response. In this article, we show that administration of cGAMP, delivered by an ultra-pH-sensitive nanoparticle (NP; PC7A), in human PBMCs induces potent and long-acting antiretroviral response against several laboratory-adapted and clinical HIV-1 isolates. cGAMP-PC7A NP requires endocytosis for intracellular delivery and immune signaling activation. cGAMP-PC7A NP-induced protection is mediated through type I IFN signaling and requires monocytes in PBMCs. cGAMP-PC7A NPs also inhibit HIV-1 replication in HIV⁺ patient PBMCs after ex vivo reactivation. Because pattern recognition receptor agonists continue to show more clinical benefits than the traditional IFN therapy, our data present important evidence for potentially developing cGAMP or other STING agonists as a new class of immune-stimulating long-acting antiretroviral agents.

A STING-activating nanovaccine for cancer immunotherapy

The generation of tumour-specific T cells is critically important for cancer immunotherapy. A major challenge in achieving a robust T-cell response is the spatiotemporal orchestration of antigen cross-presentation in antigen-presenting cells with innate stimulation. Here, we report a minimalist nanovaccine, comprising a simple physical mixture of an antigen and a synthetic polymeric nanoparticle, PC7A NP, which generates a strong cytotoxic T-cell response with low systemic cytokine expression. Mechanistically, the PC7A NP achieves efficient cytosolic delivery of tumour antigens to antigen-presenting cells in draining lymph nodes, leading to increased surface presentation while simultaneously activating type I interferon-stimulated genes. This effect is dependent on stimulator of interferon genes (STING), but not the Toll-like receptor or the mitochondrial antiviral-signalling protein (MAVS) pathway. The nanovaccine led to potent tumour growth inhibition in melanoma, colon cancer and human papilloma virus-E6/E7 tumour models. The combination of the PC7A nanovaccine and an anti-PD-1 antibody showed great synergy, with 100% survival over 60 days in a TC-1 tumour model. Rechallenging of these tumour-free animals with TC-1 cells led to complete inhibition of tumour growth, suggesting the generation of long-term antitumour memory. The STING-activating nanovaccine offers a simple, safe and robust strategy in boosting anti-tumour immunity for cancer immunotherapy.