Transistor-like Ultra-pH-Sensitive Polymeric Nanoparticles

Ultra-pH-sensitive nanoplatform for precise tumor therapy

The emergence of precision cancer treatment has triggered a paradigm shift in the field of oncology, facilitating the implementation of more effective and personalized therapeutic approaches that enhance patient outcomes. The pH of the tumor microenvironment (TME) plays a pivotal role in both the initiation and progression of cancer, thus emerging as a promising focal point for precision cancer treatment. By specifically targeting the acidic conditions inherent to the tumor microenvironment, innovative therapeutic interventions have been proposed, exhibiting significant potential in augmenting treatment efficacy and ameliorating patient prognosis. The concept of ultra-pH-sensitive (UPS) nanoplatform was proposed several years ago, demonstrating exceptional pH sensitivity and an adjustable pH transition point. Subsequently, diverse UPS nanoplatforms have been actively explored for biomedical applications, enabling the loading of fluorophores, therapeutic drugs, and photosensitizers. This review aims to elucidate the design strategy and response mechanism of the UPS nanoplatform, with a specific emphasis on its applications in surgical therapy, immunotherapy, drug delivery, photodynamic therapy, and photothermal therapy. The potential and challenges of translating in the clinic on UPS nanoplatforms are finally explored. Thanks to its responsive and easily modifiable nature, the integration of multiple functional units within a UPS nanoplatform holds great promise for future advancements in tumor precision theranositcs.

Elucidation of Spatial Cooperativity in Chemo-Immunotherapy by a Sequential Dual-pH-Responsive Drug Delivery System

Combining immune checkpoint blockade with chemotherapy through nanotechnology is promising in terms of safety and efficacy. However, the distinct subcellular distribution of each ingredient's action site makes it challenging to acquire an optimal synergism. Herein, a dual-pH responsive hybrid polymeric micelle system, HNP(αPDL16.9, Dox5.3), is constructed as a proof-of-concept for the spatial cooperativity in chemo-immunotherapy. HNP retains the inherent pH-transition of each polymer, with stepwise disassembly under discrete pH thresholds. Within weakly acidic extracellular tumor environment, αPDL1 is first released to block the checkpoint on cell membranes. The remaining intact Doxorubicin-loaded micelle NP(Dox)5.3 displays significant tropism toward tumor cells and releases Dox upon lysosomal pH for efficient tumor immunogenic cell death without immune toxicity. This sequential-released pattern boosts DC activation and primes CD8+ T cells, leading to enhanced therapeutic performance than single agent or an inverse-ordered combination in multiple murine tumor models. Using HNP, the indispensable role of conventional type 1 DC (cDC1) is identified in chemo-immunotherapy. A co-signature of cDC1 and CD8 correlates with cancer patient survival after neoadjuvant Pembrolizumab plus chemotherapy in clinic. This study highlights spatial cooperativity of chemo- and immuno-agents in immunoregulation and provides insights into the rational design of drug combination for future nanotherapeutics development.

Severely polarized extracellular acidity around tumour cells

Extracellular pH impacts many molecular, cellular and physiological processes, and hence is tightly regulated. Yet, in tumours, dysregulated cancer cell metabolism and poor vascular perfusion cause the tumour microenvironment to become acidic. Here by leveraging fluorescent pH nanoprobes with a transistor-like activation profile at a pH of 5.3, we show that, in cancer cells, hydronium ions are excreted into a small extracellular region. Such severely polarized acidity (pH <5.3) is primarily caused by the directional co-export of protons and lactate, as we show for a diverse panel of cancer cell types via the genetic knockout or inhibition of monocarboxylate transporters, and also via nanoprobe activation in multiple tumour models in mice. We also observed that such spot acidification in ex vivo stained snap-frozen human squamous cell carcinoma tissue correlated with the expression of monocarboxylate transporters and with the exclusion of cytotoxic T cells. Severely spatially polarized tumour acidity could be leveraged for cancer diagnosis and therapy.

Application and progress of nanozymes in antitumor therapy

Tumors remain one of the major threats to public health and there is an urgent need to design new pharmaceutical agents for their diagnosis and treatment. In recent years, due to the rapid development of nanotechnology, biotechnology, catalytic science, and theoretical computing, subtlety has gradually made great progress in research related to tumor diagnosis and treatment. Compared to conventional drugs, enzymes can improve drug distribution and enhance drug enrichment at the tumor site, thereby reducing drug side effects and enhancing drug efficacy. Nanozymes can also be used as tumor tracking imaging agents to reshape the tumor microenvironment, providing a versatile platform for the diagnosis and treatment of malignancies. In this paper, we review the current status of research on enzymes in oncology and analyze novel oncology therapeutic approaches and related mechanisms. To date, a large number of nanomaterials, such as noble metal nanomaterials, nonmetallic nanomaterials, and carbon-based nanomaterials, have been shown to be able to function like natural enzymes, particularly with significant advantages in tumor therapy. In light of this, the authors in this review have systematically summarized and evaluated the construction, enzymatic activity, and their characteristics of nanozymes with respect to current modalities of tumor treatment. In addition, the application and research progress of different types of nicknames and their features in recent years are summarized in detail. We conclude with a summary and outlook on the study of nanozymes in tumor diagnosis and treatment. It is hoped that this review will inspire researchers in the fields of nanotechnology, chemistry, biology, materials science and theoretical computing, and contribute to the development of nano-enzymology.

pH-Responsive Protein Conformation Transistor

Analogous to electronic transistors, transistor-like responsive materials undergo sharp structural transitions in response to a very narrow range of microenvironment signals. This kind of material is typically limited to synthetic polymer-derived nanoscale assembly or disassembly and has profound implications for modern high-tech applications. Herein, we evolve this system from synthetic polymers to biopolymers and extend the corresponding assembly scale from the nanoscale to meso/macro-scale. We develop unique protein nanocrystals with core-shell structures through a two-step nucleation process. The protein nanocrystals exhibit exceptional transistor-like pH-responsive mesoscale assembly through the formation of inter-particle β-sheet linkers. This allows ultrasensitive cross-linking behavior, such as self-coacervation at a water/water interface, ultrafast gelation in seconds, and ultrasensitive swelling for detection of basic vapors at extremely low concentrations. This breakthrough has great promise for broader applications such as drug encapsulation and delivery, biosensing, cytomimetic materials, and microfluidic chemistry.

Structural Determinants of Stimuli-Responsiveness in Amphiphilic Macromolecular Nano-assemblies

Stimuli-responsive nano-assemblies from amphiphilic macromolecules could undergo controlled structural transformations and generate diverse macroscopic phenomenon under stimuli. Due to the controllable responsiveness, they have been applied for broad material and biomedical applications, such as biologics delivery, sensing, imaging, and catalysis. Understanding the mechanisms of the assembly-disassembly processes and structural determinants behind the responsive properties is fundamentally important for designing the next generation of nano-assemblies with programmable responsiveness. In this review, we focus on structural determinants of assemblies from amphiphilic macromolecules and their macromolecular level alterations under stimuli, such as the disruption of hydrophilic-lipophilic balance (HLB), depolymerization, decrosslinking, and changes of molecular packing in assemblies, which eventually lead to a series of macroscopic phenomenon for practical purposes. Applications of stimuli-responsive nano-assemblies in delivery, sensing and imaging were also summarized based on their structural features. We expect this review could provide readers an overview of the structural considerations in the design and applications of nanoassemblies and incentivize more explorations in stimuli-responsive soft matters.

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.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.

Advances in nanomaterials for the diagnosis and treatment of head and neck cancers: A review

Nanomaterials (NMs) have increasingly been used for the diagnosis and treatment of head and neck cancers (HNCs) over the past decade. HNCs can easily infiltrate surrounding tissues and form distant metastases, meaning that most patients with HNC are diagnosed at an advanced stage and often have a poor prognosis. Since NMs can be used to deliver various agents, including imaging agents, drugs, genes, vaccines, radiosensitisers, and photosensitisers, they play a crucial role in the development of novel technologies for the diagnosis and treatment of HNCs. Indeed, NMs have been reported to enhance delivery efficiency and improve the prognosis of patients with HNC by allowing targeted delivery, controlled release, responses to stimuli, and the delivery of multiple agents. In this review, we consider recent advances in NMs that could be used to improve the diagnosis, treatment, and prognosis of patients with HNC and the potential for future research.

Activatable fluorescent probes for real-time imaging-guided tumor therapy

Surgery and drug therapy are the two principal options for cancer treatment. However, their clinical benefits are hindered by the difficulty of accurate location of the tumors and timely monitoring of the treatment efficacy of drugs, respectively. Rapid development of imaging techniques provides promising tools to address these challenges. Compared with conventional imaging techniques such as magnetic resonance imaging and computed tomography etc., fluorescence imaging exhibits high spatial resolution, real-time imaging capability, and relatively low costs devices. The advancements in fluorescent probes further accelerate the implementation of fluorescence imaging in tumor diagnosis and treatment monitoring. In particular, the emergence of site-specifically activatable fluorescent probes fits the demands of tumor delineation and real-time feedback of the treatment efficacy. A variety of small molecule probes or nanoparticle-based probes have been developed and explored for the above-mentioned applications. This review will discuss recent advances in fluorescent probes with a special focus on activatable nanoprobes and highlight the potential implementation of activatable nanoprobes in fluorescence imaging-guided surgery as well as imaging-guided drug therapy.

Encapsulation of Platinum Prodrugs into PC7A Polymeric Nanoparticles Combined with Immune Checkpoint Inhibitors for Therapeutically Enhanced Multimodal Chemotherapy and Immunotherapy by Activation of the STING Pathway

Tumor immunotherapy has emerged as one of the most promising therapeutic methods to treat cancer. Despite its clinical application, the immunosuppressive tumor microenvironment compromises the therapeutic efficiency of this technique. To overcome this limitation, many research efforts have been devoted to the development of agents that reprogram the immunosuppressive tumor microenvironment through novel mechanisms. Over the last decade, compounds that intervene through the immunogenic stimulator of interferon genes (STING) pathway have emerged with potential for clinical development. Herein, the encapsulation of chemotherapeutic platinum complexes with a polymer with a cyclic seven-membered ring (PC7A)-based polymer into pH-responsive nanoparticles for multimodal therapeutically enhanced chemotherapy and immunotherapy is presented. This study represents the first nanomaterial with a dual activation mechanism of the STING pathway through DNA fragmentation as well as PC7A binding. The combination of these nanoparticles with immune checkpoint inhibitors demonstrates to nearly fully eradicate a colorectal tumor inside the mouse model by chemotherapy and immunotherapy using the STING pathway.

pH-triggered cancer-targeting polymers: From extracellular accumulation to intracellular release

Stimuli-responsive polymers are promising to achieve targeted delivery, improved stability during circulation, and controlled release of therapeutic and diagnostic agents. Among them, pH-responsive polymeric nanocarriers have attracted significant attention as pH varies in different body fluids (e.g., stomach, intestine, and colon) and intracellular organelles (e.g., endosome, lysosome, and mitochondria) to maintain homeostasis, while distinctive pH changes are also found in certain pathological states. For example, the extracellular environment of the tumor is acidic, which can be employed to drive selective delivery. During the internalization process, since most nanocarriers enter cells upon endocytosis where a drop of pH from 6.5 to 5.0 can occur from endosome to lysosome, pH-sensitive groups have been developed for enhanced cargo release. In this review, both non-covalent and covalent interactions responsive to pH changes are introduced, with a focus on the structure-property relationship and their applications in cancer targeting and endosomal escape.

All-Aqueous, Surfactant-Free, and pH-Driven Nanoformulation Methods of Dual-Responsive Polymer Nanoparticles and their Potential use as Nanocarriers of pH-Sensitive Drugs

All-aqueous, surfactant-free, and pH-driven nanoformulation methods to generate pH- and temperature-responsive polymer nanoparticles (NPs) are described. Copolymers comprising a poly(methyl methacrylate) (PMMA) backbone with a few units of 2-(dimethylamino)ethyl methacrylate (DMAEMA) are solubilized in acidic buffer (pH 2.0) to produce pH-sensitive NPs. Copolymers of different molar mass (2.3-11.5 kg mol^-1 ) and DMAEMA composition (7.3-14.2 mol%) are evaluated using a "conventional" pH-driven nanoformulation method (i.e., adding an aqueous polymer solution (acidic buffer) into an aqueous non-solvent (basic buffer)) and a robotized method for pH adjustment of polymer dispersions. Dynamic light scattering, zeta-potential (ζ), and sedimentation-diffusion analyses suggest the formation of dual-responsive NPs of tunable size (from 20 to 110 nm) being stable for at least 28 days in the pH and temperature intervals from 2.0 to 6.0 and 25 to 50 °C, respectively. Ultraviolet-visible spectroscopic experiments show that these NPs can act as nanocarriers for the pH-sensitive dipyridamole drug, expanding its bioavailability and potential controlled release as a function of pH and temperature. These approaches offer alternative strategies to prepare stimuli-responsive NPs, avoiding the use of harmful solvents and complex purification steps, and improving the availability of biocompatible polymer nanoformulations for specific controlled release of pH-sensitive cargos.

Tumor targetable and pH-sensitive polymer nanoparticles for simultaneously improve the Type 2 Diabetes Mellitus and malignant breast cancer

In the recent study, we have developed novel tumor targetable and pH-sensitive PLGA nanoparticles co-loaded with camptothecin (CPT) and metformin (Metf) to simultaneously improve the Type 2 Diabetes Mellitus (T2DM) and malignant breast cancer. To improve the drug loading efficiency, the hydrophobic CPT was conjugated with PLGA polymer by the pH-sensitive hydrazone bonds (hyd). Then, the Metf was physically loaded into the hydrophobicity inner core of CPT-conjugated PLGA nanocomplex to form the dual drugs-loaded nanoparticles (NP/CPT-Metf). Furthermore, on the surface of NP/CPT-Metf was modified with tumor-homing CGKRK peptides to obtain the tumor targetable and pH-sensitive polymer nanoparticles (CNP/CPT-Metf). It was demonstrated that the developed CNP/CPT-Metf displayed sufficient sensitivity to the weak acidic tumor microenvironment. Besides, excellent ability of CNP/CPT-Metf to mediate accumulation of drugs in cells and tumor tissues finally in turn resulted in a signal enhanced anti-tumor effect. Furthermore, it was demonstrated as well that CNP/CPT-Metf was able of significantly alleviating the type 2 diabetes mellitus in diabetic mice. In summary, the developed multifunctional polymer nanoparticles might represent a promising strategy for simultaneously improve the T2DM and treat malignant breast cancer.

Modulating Boronic Ester Stability in Block Copolymer Micelles via the Neighbor Effect of Copolymerized Tertiary Amines for Controlled Release of Polyphenolic Drugs

The traceless and pH-sensitive properties of boronic esters are attractive for the synthesis of polymer-drug conjugates, but current platforms suffer from both low stability under physiologically relevant conditions and synthetically demanding optimization to tune drug release profiles. We hypothesized that the high catechol affinity and stability of Wulff-type boronic acids could be mimicked by copolymerization of phenyl boronic acid with a tertiary amine and subsequent micellization. This strategy yielded a versatile platform for the preparation of reversible polymer-drug conjugates, which more than doubled the oxidative stability of encapsulated polyphenolic drug cargo at physiologically relevant pH and enabled simple and incremental tuning of drug release kinetics. Moreover, we validated, with ¹⁹F NMR, that these copolymers exhibit uniquely high catechol affinity that could not be replicated by combinations of similarly functionalized small molecules. Overall, this report demonstrates that copolymerization of boronic acid and tertiary amine monomers is a powerful and modular approach to improving boronic ester chemistry for drug delivery applications.

pH-Responsive, Two-in-One Doxorubicin and Bcl-2 siRNA-Loaded Micelleplexes for Triple-Negative Breast Cancer Therapy

The combination of chemotherapy and gene therapy is a versatile strategy for treating multi-drug-resistant cancer. Accordingly, we developed a pH-responsive triblock copolymeric carrier for delivering chemotherapeutic and genetic drugs simultaneously....

STING and TLR7/8 agonists-based nanovaccines for synergistic antitumor immune activation

Immunostimulatory therapies based on pattern recognition receptors (PRRs) have emerged as an effective approach in the fight against cancer, with the ability to recruit tumor-specific lymphocytes in a low-immunogenicity tumor environment. The agonist cyclic dinucleotides (CDNs) of the stimulator of interferon gene (STING) are a group of very promising anticancer molecules that increase tumor immunogenicity by activating innate immunity. However, the tumor immune efficacy of CDNs is limited by several factors, including relatively narrow cytokine production, inefficient delivery to STING, and rapid clearance. In addition, a single adjuvant molecule is unable to elicit a broad cytokine response and thus cannot further amplify the anticancer effect. To address this problem, two or more agonist molecules are often used together to synergistically enhance immune efficacy. In this work, we found that a combination of the STING agonist CDG^SF and the Toll-like receptor 7/8 (TLR7/8) agonist 522 produced a broader cytokine response. Subsequently, we developed multicomponent nanovaccines (MCNVs) consisting of a PC7A polymer as a nanocarrier encapsulating the antigen OVA and adjuvant molecules. These MCNVs activate bone marrow-derived dendritic cells (BMDCs) to produce multiple proinflammatory factors that promote antigen cross-presentation to stimulate specific antitumor T-cell responses. In in vivo experiments, we observed that MCNVs triggered a strong T-cell response in tumor-infiltrating lymphocytes, resulting in significant tumor regression and, notably, a 100% survival rate in mice through 25 days without other partnering therapies. These data suggest that our nanovaccines have great potential to advance cancer immunotherapy with increased durability and potency.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (synthesis of CDG^SF, 522, PC7A and OVA; preparation of MCNVs; representative gating strategies for flow cytometry) is available in the online version of this article at 10.1007/s12274-022-4282-x.

Programmable DNA Framework Sensors for In Situ Cell-Surface pH Analysis

The availability of strategies for developing sensors with a defined responsiveness as well as the ability to working in a biological environment is critical to the fields of bioanalysis, nanomedicine, and nanorobotics. Herein, we developed programmable pH sensors by employing a tetrahedral DNA framework (TDF) as a robust structural skeleton for the sensors in biological working scenes and DNA i-motif structures as proton-recognition probes. The sensors' response midpoint and dynamic range can be fine-tuned by deliberately altering the i-motif's sequence composition or by combining different sensors, affording pH response windows that are consecutively distributed in the biologically relevant pH range of 5.0-7.5. This controllable tunability was successfully employed for in situ cell-surface pH analysis after anchoring the i-motif-TDF nanosensor on the cell surface via a two-step anchoring strategy, providing a useful platform for the diagnostics of diseases associated with extracellular pH variations.

Development of D-melittin polymeric nanoparticles for anti-cancer treatment

Melittin, the primary peptide component of bee venom, is a potent cytolytic anti-cancer peptide with established anti-tumor activity. However, practical application of melittin in oncology is hampered by its strong, nonspecific hemolytic activity and intrinsic instability. To address these shortcomings, delivery systems are used to overcome the drawbacks of melittin and facilitate its safe delivery. Yet, a recent study revealed that encapsulated melittin remains immunogenic and can act as an adjuvant to elicit a fatal antibody immune response against the delivery carrier. We discovered that substitution of l-amino acids with d-amino acids mitigates this problem: D-melittin nanoformulations induce significantly decreased immune response, resulting in excellent safety without compromising cytolytic potential. We now report the first application of D-melittin and its micellar formulations for cancer treatment. D-melittin was delivered by a pH-sensitive polymer carrier that (i) forms micellar nanoparticles at normal physiological conditions, encapsulating melittin, and (ii) dissociates at endosomal pH, restoring melittin activity. D-melittin micelles (DMM) exhibits significant cytotoxicity and induces hemolysis in a pH-dependent manner. In addition, DMM induce immunogenic cell death, revealing its potential for cancer immunotherapy. Indeed, in vivo studies demonstrated the superior safety profile of DMM over free peptide and improved efficacy at prohibiting tumor growth. Overall, we present the first application of micellar D-melittin for cancer therapy. These findings establish a new strategy for safe, systemic delivery of melittin, unlocking a potential pathway toward clinical translation for cytotoxic peptides as anti-cancer agents. which can revolutionize in vivo delivery of therapeutic peptides and peptide antigens.

A dual-channel Hill-type small-molecule pH probe

By combining a Hill-type pH probe and a pH-insensitive naphthalimide fluorophore, we synthesized a FRET-based ratiometric pH probe (PHHF), exhibiting a reduced pH transition width, representing a unique approach for development of sensitive probes for detection of biorelevant pH changes.

Prolonged activation of innate immune pathways by a polyvalent STING agonist

The stimulator of interferon genes (STING) is an endoplasmic reticulum transmembrane protein that is a target of therapeutics for infectious diseases and cancer. However, early-phase clinical trials of small-molecule STING agonists have shown limited antitumour efficacy and dose-limiting toxicity. Here, we show that a polyvalent STING agonist-a pH-sensitive polymer bearing a seven-membered ring with a tertiary amine (PC7A)-activates innate-immunity pathways through the polymer-induced formation of STING-PC7A condensates. In contrast to the natural STING ligand 2',3'-cyclic-GMP-AMP (cGAMP), PC7A stimulates the prolonged production of pro-inflammatory cytokines by binding to a non-competitive STING surface site that is distinct from the cGAMP binding pocket. PC7A induces antitumour responses that are dependent on STING expression and CD8⁺ T-cell activity, and the combination of PC7A and cGAMP led to synergistic therapeutic outcomes (including the activation of cGAMP-resistant STING variants) in mice bearing subcutaneous tumours and in resected human tumours and lymph nodes. The activation of the STING pathway through polymer-induced STING condensation may offer new therapeutic opportunities.

Dimeric prodrug-based nanomedicines for cancer therapy

With the rapid development of conjugation chemistry and biomedical nanotechnology, prodrug-based nanosystems (PNS) have emerged as promising drug delivery nanoplatforms. Dimeric prodrug, as an emerging branch of prodrug, has been widely investigated by covalently conjugating two same or different drug molecules. In recent years, great progress has been made in dimeric prodrug-based nanosystems (DPNS) for cancer therapy. Many advantages offered by DPNS have significantly facilitated the delivery efficiency of anticancer drugs, such as high drug loading capacity, favorable pharmacokinetics, tumor stimuli-sensitive drug release and facile combination theranostics. Given the rapid developments in this field, we here outline the latest updates of DPNS in cancer treatment, focusing on dimeric prodrug-encapsulated nanosystems, dimeric prodrug-nanoassemblies and tumor stimuli-responsive DPNS. Moreover, the design principle, advantages and challenges of DPNS for clinical cancer therapy are also highlighted.

Renal clearable nanocarriers: Overcoming the physiological barriers for precise drug delivery and clearance

Physiological barriers encountered in the clinical translation of cancer nanomedicines inspire the community to more deeply understand nano-bio interactions in not only tumor microenvironment but also entire body and develop new nanocarriers to tackle these barriers. Renal clearable nanocarriers are one kind of these newly emerged drug delivery systems (DDSs), which enable drugs to rapidly penetrate into the tumor cores with no need of long blood retention and escape macrophage uptake in the meantime they can also enhance body elimination of non-targeted anticancer drugs. As a result, they can improve therapeutic efficacies and reduce side effects of anticancer drugs. Not limited to anticancer drugs, diagnostic agents can also be achieved with these renal clearable DDSs, which might also be applied to improve the precision in the gene editing and immunotherapy in the future.

Reactive oxygen species-activatable camptothecin polyprodrug based dextran enhances chemotherapy efficacy by damaging mitochondria

Low loading capacity, poor accumulation rate and weak permeability at tumor sites have been identified as the critical barriers for anti-cancer nanomedicines (ANMs). We herein reported a reactive oxygen species (ROS)-activatable ANM of dextran-b-P(CPTMA-co-OEGMA) (DCPT). It aimed to meet the above challenges for improving the therapeutic efficiency of chemotherapy. In this system, camptothecin (CPT) was selected as a chemotherapy drug and poly(ethylene glycol)methyl ether methacrylate (OEGMA) played the role of a hydrophilic block to enhance the water solubility of polyprodrug micelles. At high ROS levels in the tumor microenvironment, the micelles could be disassembled, and simultaneously, the anti-cancer drug of CPT would be released from the DCPT micelles. The 4T1-tumor growth would be greatly inhibited by these two DCPT polyprodrugs, with outstanding in vivo biosafety. The results of both in vitro and in vivo studies indicated the superior therapeutic effects of DCPT. The rational design of polyprodrug nanomedicines may serve as a promising strategy for the development of tumor microenvironment-responsive ANMs, thus improving chemotherapy efficacy.

Intratumoral fate of functional nanoparticles in response to microenvironment factor: Implications on cancer diagnosis and therapy

The extraordinary growth and progression of tumor require enormous nutrient and energy. Unregulated behaviors of cancer cell progressing and persistently change of tumor microenvironment (TME) which acts as the soil for cancer growth and metastasis are the ubiquitous features. The tumor microenvironment exhibits some unique features which differ with the normal tissues. While the nanoparticles get through the blood vessel leakage, they encounter immediately and interact directly with these microenvironment factors. These factors may inhibit the diffusion of nanoparticles from penetrating through the tumor, or induce the dissociation of nanoparticles. Different nanoparticles encountered with different intratumoral microenvironment factors end up in different way. Therefore, in this review, we first briefly introduced the formations, distributions, features of some intratumoral microenvironment, and their effects on the tumor progression. They include extracellular matrix (ECM), matrix metalloproteinases (MMPs), acidic/hypoxia environment, redox environment, and tumor associated macrophages (TAMs). We then exemplified how these factors interact with nanoparticles and emphasized the potentials and challenges of nanoparticle-based strategies facing in enhancing intratumoral penetration and tumor microenvironment remodeling. We hope to give a simple understanding of the interaction between these microenvironment factors and the nanoparticles, thus, favors the designing and constructing of more ideal functional nanoparticles.