Design, Synthesis, and Acid-Responsive Disassembly of Shell-Sheddable Block Copolymer Labeled with Benzaldehyde Acetal Junction

Smart nanoassemblies degradable through the cleavage of acid-labile linkages have attracted significant attention because of their biological relevance found in tumor tissues. Despite their high potential to achieve controlled/enhanced drug release, a systematic understanding of structural factors that affect their pH sensitivity remains challenging, particulary in the consruction of effective acid-degradable shell-sheddable nanoassemblies. Herein, the authors report the synthesis and acid-responsive degradation through acid-catalyzed hydrolysis of three acetal and ketal diols and identify benzaldehyde acetal (BzAA) exhibiting optimal hydrolysis profiles in targeted pH ranges to be a suitable candidate for junction acid-labile linkage. The authors explore the synthesis and aqueous micellization of well-defined poly(ethylene glycol)-based block copolymer bearing BzAA linkage covalently attached to a polymethacrylate block for the formation of colloidally-stable nanoassemblies with BzAA groups at core/corona interfaces. Promisingly, the investigation on acid-catalyzed hydrolysis and disassembly shows that the formed nanoassemblies meet the criteria for acid-degradable shell-sheddable nanoassemblies: slow degradation at tumoral pH = 6.5 and rapid disassembly at endo/lysosomal pH = 5.0, while colloidal stability at physiological pH = 7.4. This work guides the design principle of acid-degradable shell-sheddable nanoassemblies bearing BzAA at interfaces, thus offering the promise to address the PEG dilemma and improve endocytosis in tumor-targeting drug delivery.

Near-infrared photodynamic and photothermal co-therapy based on organic small molecular dyes

Near-infrared (NIR) organic small molecule dyes (OSMDs) are effective photothermal agents for photothermal therapy (PTT) due to their advantages of low cost and toxicity, good biodegradation, and strong NIR absorption over a wide wavelength range. Nevertheless, OSMDs have limited applicability in PTT due to their low photothermal conversion efficiency and inadequate destruction of tumor regions that are nonirradiated by NIR light. However, they can also act as photosensitizers (PSs) to produce reactive oxygen species (ROS), which can be further eradicated by using ROS-related therapies to address the above limitations of PTT. In this review, the synergistic mechanism, composition, and properties of photodynamic therapy (PDT)-PTT nanoplatforms were comprehensively discussed. In addition, some specific strategies for further improving the combined PTT and PDT based on OSMDs for cancer to completely eradicate cancer cells were outlined. These strategies include performing image-guided co-therapy, enhancing tumor infiltration, increasing H2O2 or O2 in the tumor microenvironment, and loading anticancer drugs onto nanoplatforms to enable combined therapy with phototherapy and chemotherapy. Meanwhile, the intriguing prospects and challenges of this treatment modality were also summarized with a focus on the future trends of its clinical application.

An IL-12-Based Nanocytokine Safely Potentiates Anticancer Immunity through Spatiotemporal Control of Inflammation to Eradicate Advanced Cold Tumors

Treatment of immunologically cold tumors is a major challenge for immune checkpoint inhibitors (ICIs). Interleukin 12 (IL-12) can invigorate ICIs against cold tumors by establishing a robust antitumor immunity. However, its toxicity and systemic induction of counteracting immunosuppressive signals have hindered translation. Here, IL-12 activity is spatiotemporally controlled for safely boosting efficacy without the stimulation of interfering immune responses by generating a nanocytokine that remains inactive at physiological pH, but unleashes its full activity at acidic tumor pH. The IL-12-based nanocytokine (Nano-IL-12) accumulate and release IL-12 in tumor tissues, eliciting localized antitumoral inflammation, while preventing systemic immune response, counteractive immune reactions, and adverse toxicities even after repeated intravenous administration. The Nano-IL-12-mediated spatiotemporal control of inflammation prompt superior anticancer efficacy, and synergize with ICIs to profoundly inflame the tumor microenvironment and completely eradicate ICI-resistant primary and metastatic tumors. The strategy could be a promising approach toward safer and more effective immunotherapies.

Simultaneous Knockdown of Immune Suppressive Markers by Tumor Microenvironment-Responsive Multifaceted Prodrug Nanomedicine

Tumors managing to exempt from immune clearance are attributable to their overexpressed immune suppressive molecules (CD47, PD-L1, etc.). Leadingly, the checkpoint blockade-based chemoimmunotherapy by means of knockdown of these immunosuppressive checkpoints, together with immunogenetic chemotherapeutics, is perceived to be a valid therapeutic strategy for improving anti-tumor outcomes. Herein, chemotherapeutic camptothecin was covalently introduced into an intriguing multifaceted nanomedicine. Note that the elaborated nanomedicine was chemically engineered to enable targeted transportation to the tumors via systemic administration, possessing intelligent responsiveness to sequential extracellular and intracellular microenvironments in the targeted tumors for prompted transcellular endocytosis owing to enzymolysis by the tumor-enriched matrix metalloproteinases and the selective liberation of cytocidal camptothecin in the cell interiors owing to thiolysis by glutathione. In addition, this chemotherapeutic nanomedicine allowed facile encapsulation of the negatively charged RNA interference payloads. Consequently, aiming for treatment of intractable triple-negative breast tumors, we attempted the small interfering RNA (siRNA) payloads aiming for CD47 and PD-L1 into the aforementioned nanomedicine. The subsequent investigations demonstrated drastic knockdown of these vital immune suppressive checkpoints by this siRNA-encapsulating chemotherapeutic nanomedicine, conducing to the reversal of the immune checkpoint suppressive microenvironment of triple-negative 4T1 tumors. Namely, the inhibited proceedings of the innate and adaptive anti-tumor immunities were revived, as supported by observation of the activated infiltration and retention of CD68⁺ macrophages and CD4⁺ and CD8⁺ lymphocytes into the tumors. Eventually, most potent anti-tumor efficacies were accomplished by systemic administration of this chemoimmunotherapeutic nanomedicine, which verified the amplified contribution from anti-tumor immunities by means of knockdown of the immune suppressive molecules to the ultimate anti-tumor efficacies. Note that the upregulation of the immune suppressive molecules was constantly reported in a variety of clinical therapies; hence, our facile chemoimmunotherapeutic platform should be emphasized in clinical translation for seeking improved therapeutic outcomes.

Nanodrug removes physical barrier to promote T-cell infiltration for enhanced cancer immunotherapy

The dense extracellular matrix (ECM) is a key barrier to tumor infiltration of cytotoxic T lymphocytes (CTLs), which greatly compromises T cell-dependent immunotherapy of hepatocellular carcinoma (HCC). Herein, hyaluronidase (HAase), IL-12, and anti-PD-L1 antibody (αPD-L1) were co-delivered using a pH and MMP-2 dual-sensitive polymer/calcium phosphate (CaP) hybrid nanocarrier. The dissolution of CaP triggered by tumor acidity facilitated the release of IL-12 and HAase responsible for ECM digestion, enhancing the tumor infiltration and proliferation of CTLs. Furthermore, the in situ-released αPD-L1 inside tumor, as triggered by an overexpressed MMP-2, prevented the tumor cell from escaping the killing effects of CTLs. Such combination strategy induced a robust antitumor immunity for efficiently suppressing HCC growth in mice. Additionally, tumor acidity-sheddable polyethylene glycol (PEG) coating enhanced the tumor accumulation of nanocarrier and reduced the immune-related adverse events (irAEs) induced by on-target off-tumor αPD-L1. This dual-sensitive nanodrug demonstrates an effective immunotherapy paradigm for other dense ECM-characterized solid tumors.

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.

NIR-triggered ligand-presenting nanocarriers for enhancing synergistic photothermal-chemotherapy

Surface PEGylation of nanomedicine is effective for prolonging blood circulation time and facilitating the EPR effect, whereas the hydrophilic stealth surface inhibits effective cellular uptake and hinders active targeting. To address the dilemma, herein, a NIR light-triggered dePEGylation/ligand-presenting strategy based on thermal decomposition of azo bonds is developed, whereby Dox/Pz-IR nanoparticle is self-assembled from thermo-labile azo molecule-linked long PEG chain polymer (Pz-IR), cRGD-conjugated IR783 with short PEG chains (rP-IR) and doxorubicin. The long PEG chains could mask cRGD peptides in the blood circulation, preventing serum degradation and nonspecific interaction with normal cells. Once exposed to NIR laser, the PEG corona is stripped off owing to the rupture of azo bonds through the photothermal effect of IR783, and the masked cRGD peptides are exposed, which remarkably enhances cellular uptake by tumor cells and improves tumor accumulation. Dox/Pz-IR achieves the optimal synergy of photothermal-chemotherapy at mild temperature through progressive tumor accumulation, precisely regulated photothermal effect and NIR-PTT induced pulsated drug release. The strategy of NIR photo-driven dePEGylation/targeting offers a new approach to overcoming the "PEG dilemma", and provides a noval avenue for programmed tumor-targeted drug delivery.

Dual-Responsive Curcumin-Loaded Nanoparticles for the Treatment of Cisplatin-Induced Acute Kidney Injury

Acute kidney injury (AKI) has been a global public health concern leading to high patient morbidity and mortality in the world. Nanotechnology-mediated antioxidative therapy has facilitated the treatment of AKI. Herein, a hierarchical curcumin-loaded nanodrug delivery system (NPS@Cur) was fabricated for antioxidant therapy to ameliorate AKI. The nanoplatform could respond to subacidic and reactive oxygen species (ROS) microenvironments. The subacidic microenvironment led to a smaller size (from 140.9 to 99.36 nm) and positive charge (from -4.9 to 12.6 mV), contributing to the high accumulation of nanoparticles. An excessive ROS microenvironment led to nanoparticle degradation and drug release. In vitro assays showed that NPS@Cur could scavenge excessive ROS and relieve oxidative stress in H₂O₂-induced HK-2 cells through reduced apoptosis, activated autophagy, and decreased endoplasmic reticulum stress. Results from cisplatin-induced AKI models revealed that NPS@Cur could effectively alleviate mitochondria injury and protect kidneys via antioxidative protection, activated autophagy, decreased endoplasmic reticulum stress, and reduced apoptosis. NPS@Cur showed excellent biocompatibility and low toxicity to primary tissues in mice. These results revealed that NPS@Cur may be a potential therapeutic strategy for efficiently treating cisplatin or other cause-induced AKI.

Inflammation-Regulated Nanodrug Sensitizes Hepatocellular Carcinoma to Checkpoint Blockade Therapy by Reprogramming the Tumor Microenvironment

Immune checkpoint blockade (ICB) utilizing programmed death ligand-1 (PD-L1) antibody is a promising treatment strategy in solid tumors. However, in fact, more than half of hepatocellular carcinoma (HCC) patients are unresponsive to PD-L1-based ICB treatment due to multiple immune evasion mechanisms such as the hyperactivation of inflammation pathway, excessive tumor-associated macrophages (TAMs) infiltration, and insufficient infiltration of T cells. Herein, an inflammation-regulated nanodrug was designed to codeliver NF-κB inhibitor curcumin and PD-L1 antibody to reprogram the tumor microenvironment (TME) and activate antitumor immunity. The nanodrug accumulated in TME by an enhanced permeability and retention effect, where it left antibody to block PD-L1 on the membrane of tumor cells and TAMs due to pH-responsiveness. Simultaneously, a new curcumin-encapsulated nanodrug was generated, which was easily absorbed by either tumor cells or TAMs to inhibit the nuclear factor kappa-B (NF-κB) signal and related immunosuppressive genes. The inflammation-regulated nanodrug possessed good biocompatibility. Simultaneously, it reprogrammed TME effectively and exhibited an effective anticancer effect in immunocompetent mice. Overall, this study provided a potent strategy to improve the efficiency of ICB-based treatment for HCC.

Glucosylated nanoparticles for the oral delivery of antibiotics to the proximal small intestine protect mice from gut dysbiosis

Orally delivered antibiotics can reach the caecum and colon, and induce gut dysbiosis. Here we show that the encapsulation of antibiotics in orally administered positively charged polymeric nanoparticles with a glucosylated surface enhances absorption by the proximal small intestine through specific interactions of glucose and the abundantly expressed sodium-dependent glucose transporter 1. This improves bioavailability of the antibiotics, and limits their exposure to flora in the large intestine and their accumulation in caecal and faecal contents. Compared with the standard administration of the same antibiotics, the oral administration of nanoparticle-encapsulated ampicillin, chloramphenicol or vancomycin in mice with bacterial infections in the lungs effectively eliminated the infections, decreased adverse effects on the intestinal microbiota by protecting the animals from dysbiosis-associated metabolic syndromes and from opportunistic pathogen infections, and reduced the accumulation of known antibiotic-resistance genes in commensal bacteria. Glucosylated nanocarriers may be suitable for the oral delivery of other drugs causing gut dysbiosis.

Tannic acid: a crosslinker leading to versatile functional polymeric networks: a review

With the thriving of mussel-inspired polyphenol chemistry as well as the demand for low-cost analogues to polydopamine in adhesive design, tannic acid has gradually become a research focus because of its wide availability, health benefits and special chemical properties. As a natural building block, tannic acid could be used as a crosslinker either supramolecularly or chemically, ensuring versatile functional polymeric networks for various applications. Up to now, a systematic summary on tannic-acid-based networks has still been waiting for an update and outlook. In this review, the common features of tannic acid are summarized in detail, followed by the introduction of covalent and non-covalent crosslinking methods leading to various tannic-acid-based materials. Moreover, recent progress in the application of tannic acid composites is also summarized, including bone regeneration, skin adhesives, wound dressings, drug loading and photothermal conversion. Above all, we also provide further prospects concerning tannic-acid-crosslinked materials.

Single and Multiple Stimuli-Responsive Polymer Particles for Controlled Drug Delivery

Polymers that can change their properties in response to an external or internal stimulus have become an interesting platform for drug delivery systems. Polymeric nanoparticles can be used to decrease the toxicity of drugs, improve the circulation of hydrophobic drugs, and increase a drug’s efficacy. Furthermore, polymers that are sensitive to specific stimuli can be used to achieve controlled release of drugs into specific areas of the body. This review discusses the different stimuli that can be used for controlled drug delivery based on internal and external stimuli. Internal stimuli have been defined as events that evoke changes in different characteristics, inside the body, such as changes in pH, redox potential, and temperature. External stimuli have been defined as the use of an external source such as light and ultrasound to implement such changes. Special attention has been paid to the particular chemical structures that need to be incorporated into polymers to achieve the desired stimuli response. A current trend in this field is the incorporation of several stimuli in a single polymer to achieve higher specificity. Therefore, to access the most recent advances in stimuli-responsive polymers, the focus of this review is to combine several stimuli. The combination of different stimuli is discussed along with the chemical structures that can produce it.

Biomimetic nanoprobe-augmented triple therapy with photothermal, sonodynamic and checkpoint blockade inhibits tumor growth and metastasis

Background

Comprehensive antitumor therapy through integrated multimodal means has drawn increasing attention owing to its high efficiency and metastasis suppression.

Results

We describe a synergistic triple protocol combining photothermal and sonodynamic therapy (PTT and SDT), together with immune checkpoint blockade for the inhibition of breast cancer growth and metastases in the 4T1 mouse model. PTT and SDT are synergistically augmented by a novel multimodal imaging nanoprobe integrated with cancer cell membrane-biomimetic nanoparticles (CHINPs) loaded with superparamagnetic iron oxide (SPIO) and hematoporphyrin monomethyl ether (HMME). CHINPs exhibit excellent homologous tumor targeting, and are sequentially triggered by ultrasound and near infrared (NIR) light under the guidance of magnetic resonance, photoacoustic and photothermal imaging, leading to complete in situ tumor eradication and systemic anti-tumor immune activation. Further combination of this approach with immune checkpoint blockade therapy is shown to suppress tumor metastasis.

Conclusion

This work provides proof-of-principle for triple therapy using multimodal imaging-guided PTT/SDT based on biomimetic nanoprobes in combination with immunotherapy to eliminate tumors.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01287-y.

Self-targeting of zwitterion-based platforms for nano-antimicrobials and nano-carriers

Self-targeting antimicrobial platforms have yielded new possibilities for the treatment of infectious biofilms. Self-targeting involves stealth transport through the blood circulation towards an infectious biofilm, where the antimicrobial platform penetrates...

Polydopamine-drug conjugate nanocomposites based on ZIF-8 for targeted cancer photothermal-chemotherapy

Stimuli-responsive prodrug-based nanoplatform with synergistic antitumor activity is of central importance to the development of promising nanomedicines for cancer therapy. Here, we describe a polydopamine-drug conjugate nanocomposite (ZP-PDA-DOX) with targeted cancer photothermal-chemotherapy (PTT-CT), which constructed by a gradual copolymerization of dopamine (DA) and pH-sensitive dopamine-derived prodrug (DA-DOX) into the porous channels of zeolite imidazolate frameworks-8 (ZIF-8), followed by PEGylation with amino-terminated folic acid-polyethylene glycol (NH₂ -PEG-FA) to acquire the high biocompatibility, specificity, and excellent tumor-targeting property. The incorporation of polydopamine strengthened the stability and dispersion of ZIF-8, and also conferred photothermal conversion effect. In the tumor acidic microenvironment, the acid-labile hydrazone linker of DA-DOX and ZIF-8 promptly degraded to release activated DOX. Moreover, the generated hyperthermia due to the high photothermal conversion efficiency of PDA component could accelerate drug release, and simultaneously thermally ablate tumor tissue to maximize the DOX-induced CT, which could also assist PTT to eradicate tumor cells. This study provides a promising strategy for targeted cancer PTT-CT with synergistic anti-tumor effect.

Cell membrane camouflaged cerium oxide nanocubes for targeting enhanced tumor-selective therapy

Anticancer therapies with profound efficacy but negligible toxicity are a fundamental pursuit that has been made humanly possible through either targeting or tumor-selective therapeutic (TST) approaches. Herein, we developed a targeting-enhanced tumor-selective cancer therapy aimed at integrating the two approaches by preparing cerium oxide (CeO₂) nanocubes with glucose oxidase (GOx) modified on the cube surface and cancer cell membrane (CCM) camouflaged outside. The immune escape and homotypic binding of camouflaged CCM enable targeted delivery of the resultant CeO₂-GOx@CCM nanoparticles mostly into cancer tissue, while its acidic environment (pH < 6.6) activated a cascade reaction, in which the glucose was first catalyzed by GOx into H₂O₂ and then by CeO₂ into highly cytotoxic ˙OH killing cancer cells. In the case of off-targeting, when very few CeO₂-GOx@CCM nanoparticles were accidentally delivered into normal tissue, its neutral pH environment (pH = 7.4) triggered a protective reaction, in which the H₂O₂ generated was catalyzed by CeO₂ into non-toxic H₂O and O₂. Both in vitro and in vivo results demonstrated that this targeting-enhanced TST achieved the most remarkable antitumor performance with negligible toxic side effects.

Multifunctional Size-Expandable Nanomedicines Enhance Tumor Accumulation and Penetration for Synergistic Chemo-Photothermal Therapy

Size expansion can effectively improve tumor accumulation of nanocarriers where precise control is required. A dual-responsive nanocarrier stimulated by both endogenous pH and exogenous heat stimuli can change its size. Herein, a nanoparticle composed of poly(N,N-diethyl acrylamide) (PDEAA) and poly(2-(diisopropylamino) ethyl methacrylate) (PDPA) is developed. The antitumor drug celastrol (CLT) and the photosensitizer indocyanine green (ICG) are then loaded in it to form CIPP. ICG generates heat under near-infrared (NIR) stimulation to kill tumor cells and enhance CIPP penetration. Meanwhile, CIPP expands in response to hyperthermia and acid tumor microenvironments, preventing itself from returning to the blood flow, thus accumulating in tumor sites. Ultimately, the acidic lysosomal environment in tumor cells disintegrates CIPP to release CLT, directly inducing immunogenic cell death and sensitizing tumor cells for hyperthermia by disrupting the interaction of heat shock protein 90 and P50cdc37. Most of the tumors in B16F10-bearing mice are eradicated after single laser irradiation. The dual-responsive CIPP with multiple functions and simple design displays a synergistic antitumor effect. This study provides a basis for developing size-expandable stimulus-responsive drug delivery systems against tumors.

Liposomes with Water as a pH-Responsive Functionality for Targeting of Acidic Tumor and Infection Sites

A lipid named DCPA was synthesized under microwave-assisted heating. DCPA possesses a pyridine betaine, hydrophilic group that can be complexed with water through hydrogen bonding (DCPA-H2 O). DCPA-H2 O liposomes became protonated relatively fast already at pH<6.8, due to the high HOMO binding energy of DCPA-H2 O. In murine models, DCPA-H2 O liposomes had longer blood circulation times than natural DPPC or cationic DCPM liposomes, while after tail-vein injection DCPA-H2 O liposomes targeted faster to solid tumors and intra-abdominal infectious biofilms. Therapeutic efficacy in a murine, infected wound-healing model of tail-vein injected ciprofloxacin-loaded DCPA-H2 O liposomes exceeded the ones of clinically applied ciprofloxacin as well as of ciprofloxacin-loaded DPPC or DCPM liposomes.

Dynamic precise dual-drug-backboned nano-prodrugs for selective chemotherapy

To achieve an ideal drug delivery platform with precise composition and high tumor selectivity, the PEGylated dual-drug backboned prodrug was synthesized via the copolymerization between diamine monomer of ortho ester and cisplatin- demethylcantharidin conjugate (Pt(IV)-1), and then terminated by mPEG550-active ester. The amphipathic prodrug could self-assemble into nano-prodrugs, which endowed the precise structure and high drug loading. Moreover, the nano-prodrugs exhibited physicochemical stability at physiological pH (7.4) for stable blood circulation, DePEGylation and dynamic size change for selective tumor accumulation and enhanced cellular internalization at tumoral extracellular pH (6.8), and efficient drug release for synergetic apoptosis and cytotoxicity at tumoral intracellular pH (5.0)/glutathione. Thus, the precise dual-drug backboned nano-prodrugs with detachable PEGylation, dynamic size change and efficient drug release could be potentially translated for clinically selective cancer treatment. STATEMENT OF SIGNIFICANCE: Few nanomedicines have been clinically used for cancer treatment and little progress has been made in the last decades due to the unprecise composition and unsatisfactory tumor selectivity. Herein, the PEGylated dual-drug backboned nano-prodrugs were successfully constructed by rational design and endowed the defined structure, precise drug ratio, extraordinary high drug loading and reduction/pH dual sensitivity. The nano-prodrugs further exhibited the stable storage and blood circulation through PEGylation and low critical micelle concentration, enhanced tumor accumulation and cellular uptake via extracellular DePEGylation and dynamic size translation, and synergetic cytotoxicity via intracellular efficient drug release, respectively. This study can open a new avenue for easy industrial manufacture and quality control, and highly selective chemotherapy appealing for clinical translation. .

Imidazole-Mediated Dual Location Disassembly of Acid-Degradable Intracellular Drug Delivery Block Copolymer Nanoassemblies

Acid-degradable (or acid-cleavable) polymeric nanoassemblies have witnessed significant progress in anti-cancer drug delivery. However, conventional nanoassemblies designed with acid-cleavable linkages at a single location have several challenges, such as, sluggish degradation, undesired aggregation of degraded products, and difficulty in controlled and on-demand drug release. Herein, a strategy that enables the synthesis of acid-cleavable nanoassemblies labeled with acetaldehyde acetal groups in both hydrophobic cores and at core/corona interfaces, exhibiting synergistic response to acidic pH at dual locations and thus inducing rapid drug release is reported. The systematic analyses suggest that the acid-catalyzed degradation and disassembly are further enhanced by decreasing copolymer concentration (i.e., increasing proton/acetal mole ratio). Moreover, incorporation of acid-ionizable imidazole pendants in the hydrophobic cores improve the encapsulation of doxorubicin, the anticancer drug, through π-π interactions and enhance the acid-catalyzed hydrolysis of acetal linkages situated in the dual locations. Furthermore, the presence of the imidazole pendants induce the occurrence of core-crosslinking that compensates the kinetics of acetal hydrolysis and drug release. These results, combined with in vitro cell toxicity and cellular uptake, suggest the versatility of the dual location acid-degradation strategy in the design and development of effective intracellular drug delivery nanocarriers.

Improvement of Gold Nanorods in Photothermal Therapy: Recent Progress and Perspective

Cancer is a life-threatening disease, and there is a significant need for novel technologies to treat cancer with an effective outcome and low toxicity. Photothermal therapy (PTT) is a noninvasive therapeutic tool that transports nanomaterials into tumors, absorbing light energy and converting it into heat, thus killing tumor cells. Gold nanorods (GNRs) have attracted widespread attention in recent years due to their unique optical and electronic properties and potential applications in biological imaging, molecular detection, and drug delivery, especially in the PTT of cancer and other diseases. This review summarizes the recent progress in the synthesis methods and surface functionalization of GNRs for PTT. The current major synthetic methods of GNRs and recently improved measures to reduce toxicity, increase yield, and control particle size and shape are first introduced, followed by various surface functionalization approaches to construct a controlled drug release system, increase cell uptake, and improve pharmacokinetics and tumor-targeting effect, thus enhancing the photothermal effect of killing the tumor. Finally, a brief outlook for the future development of GNRs modification and functionalization in PTT is proposed.

Dual-Sensitive PEG-Sheddable Nanodrug Hierarchically Incorporating PD-L1 Antibody and Zinc Phthalocyanine for Improved Immuno-Photodynamic Therapy

Tumor immunotherapy like immune checkpoint blockade (ICB) shows great success nowadays but is severely limited by low response rates and immune-related adverse events (IRAEs). While photodynamic therapy (PDT) could efficiently eradicate tumor cells and further induce immune responses to promote activating of T lymphocytes. Herein a nanodrug hierarchically incorporating photosensitizer and PD-L1 antibody was developed for synergistic tumor immuno-photodynamic therapy. A pH/enzyme dual-sensitive polymeric micelle with sheddable PEG coating was designed for codelivery of PD-L1 antibody and zinc phthalocyanine (ZnPc) in the tumor. The tumor microenvironment featuring low pH and high matrix metallopeptidase 2 (MMP-2) sequentially triggered the shedding of PEG and the release of PD-L1 antibody to exert local ICB in tumor tissue, after which the remaining nanodrug with ZnPc undergoing charge reversal was readily delivered into tumor cells. With light irradiation, the photodynamic therapy effect of sAMPc induced immunogenic cell death of tumor cells and further promoted intratumor recruitment of CD8+ T cells, thus resulting in a synergistic immuno-photodynamic therapy with ICB. Moreover, the PEG-sheddable strategy endowed the nanodrug with stealth properties in blood circulation, making the IRAEs of PD-L1 antibody significantly reduced. This pH/MMP-2 dual-sensitive PEG sheddable nanodrug provids a promising strategy for well-combined ICB therapy and PDT to achieve improved anticancer immuno-photodynamic therapy with reduced adverse effects.

Nanoplatforms for Targeted Stimuli-Responsive Drug Delivery: A Review of Platform Materials and Stimuli-Responsive Release and Targeting Mechanisms

To achieve the promise of stimuli-responsive drug delivery systems for the treatment of cancer, they should (1) avoid premature clearance; (2) accumulate in tumors and undergo endocytosis by cancer cells; and (3) exhibit appropriate stimuli-responsive release of the payload. It is challenging to address all of these requirements simultaneously. However, the numerous proof-of-concept studies addressing one or more of these requirements reported every year have dramatically expanded the toolbox available for the design of drug delivery systems. This review highlights recent advances in the targeting and stimuli-responsiveness of drug delivery systems. It begins with a discussion of nanocarrier types and an overview of the factors influencing nanocarrier biodistribution. On-demand release strategies and their application to each type of nanocarrier are reviewed, including both endogenous and exogenous stimuli. Recent developments in stimuli-responsive targeting strategies are also discussed. The remaining challenges and prospective solutions in the field are discussed throughout the review, which is intended to assist researchers in overcoming interdisciplinary knowledge barriers and increase the speed of development. This review presents a nanocarrier-based drug delivery systems toolbox that enables the application of techniques across platforms and inspires researchers with interdisciplinary information to boost the development of multifunctional therapeutic nanoplatforms for cancer therapy.

Dynamic methotrexate nano-prodrugs with detachable PEGylation for highly selective synergistic chemotherapy

To promote the highly selective synergistic chemotherapy, the pH-ultra-sensitive dynamic methotrexate nano-prodrugs with detachable PEGylation were successfully prepared via facile method, and the synergistic nanodrugs could be further constructed through encapsulating Doxorubicin (DOX) following the self-assembly process. The nano-prodrugs exhibited the low critical micelle concentration (CMC), negative zeta potential and stability for 5 days in PBS and FBS at physiological pH (7.4) for stable blood circulation, DePEGylation and dynamic size change at tumoral extracellular pH (6.8) for improved tumor accumulation and cellular internalization, and efficiently synergistic drug release at tumoral intracellular pH (5.0) for enhanced tumor apoptosis and cytotoxicity. Moreover, in vivo experiment suggested that the synergistic nanodrugs could significantly improve tumor accumulation and restrain tumor growth while decreasing adverse effects. Therefore, the dynamic methotrexate nano-prodrugs with detachable PEGylation are easy to clinically transform for highly selective synergistic chemotherapy.

Nanodrug with dual-sensitivity to tumor microenvironment for immuno-sonodynamic anti-cancer therapy

Although a combination with photodynamic therapy (PDT) is a potential means to improve the immune checkpoint blockade (ICB)-based anticancer immunotherapy, this strategy is subjected to the extremely poor light penetration in melanoma. Herein, we develop a lipid (LP)-based micellar nanocarrier encapsulating sonosensitizer chlorin e6 (Ce6) in the core, conjugating anti-PD-L1 antibody (aPD-L1) to the interlayer through MMP-2-cleavable peptide, and bearing a PEG coating sheddable at low pH value (≈6.5) of tumor microenvironment. The unique nanocarrier design allows a tumor-targeting delivery to activate the anti-tumor immunity and meanwhile to reduce immune-related adverse effects (irAEs). Moreover, a sonodynamic therapy (SDT) is triggerable by using ultrasonic insonation to produce tumor-killing reactive oxygen species (ROS), thereby bypassing the poor light penetration which restricts PDT in melanoma. A combination of SDT with aPD-L1 immunotherapy effectively promotes tumor infiltration and activation of cytotoxic T cells, which resulted in robust anti-cancer immunity and long-term immune memory to effectively suppress melanoma growth and postoperative recurrence. This strategy for tumor-targeting codelivery of immune checkpoint inhibitors and SDT agents could be readily extended to other tumor types for better immunotherapeutic outcome and reduced irAEs.

A Drug-Free Therapeutic System for Cancer Therapy by Diselenide-Based Polymers Themselves

The application of nanotechnology-based drug delivery systems has resulted in great progresses in cancer therapy. However, current systems ultimately depend on the action of the drug itself and almost all nanocarriers only serve as excipients without any therapeutic efficacy. Herein, a drug-free therapeutic system is put forward, in which synthetic polymers themselves naturally exhibit effective anticancer activity without the loading of additional chemotherapy drugs. Aiming at this goal, amphiphilic poly(diselenide-carbonate) copolymers (PSeSeTMC), consisting of monomethyl ether poly(ethylene glycol) and diselenide-based polycarbonates, are designed and synthesized to build spherical nanoparticles, which show effective and broad-spectrum anticancer activities against multiple cancer cell lines and high selectivity toward cancer cells. Moreover, the anticancer activities can be well controlled by tuning the selenium contents in polymers. Mechanistic investigations indicate that PSeSeTMC can selectively induce cancer cells to express excessive reactive oxygen species, thereby leading to significant cellular apoptosis. In vivo antitumor studies further demonstrate high therapeutic efficacy and low side effects on normal tissue. Overall, this work provides a novel approach for cancer therapy by utilizing carriers themselves. Considering the fabrication process is pretty simple, this diselenide-based polymeric system has great potential in clinical translation.

Chemo-physical Strategies to Advance the in Vivo Functionality of Targeted Nanomedicine: The Next Generation

The past few decades have witnessed an evolution of nanomedicine from biologically inert entities to more smart systems, aimed at advancing in vivo functionality. However, we should recognize that most systems still rely on reasonable explanation-including some over-explanation-rather than definitive evidence, which is a watershed radically determining the speed and extent of advancing nanomedicine. Probing nano-bio interactions and desirable functionality at the tissue, cellular, and molecular levels is most frequently overlooked. Progress toward answering these questions will provide instructive insight guiding more effective chemo-physical strategies. Thus, in the next generation, we argue that much effort should be made to provide definitive evidence for proof-of-mechanism, in lieu of creating many new and complicated systems for similar proof-of-concept.

Library of Derivatizable Multiblock Copolymers by Nucleophilic Substitution Polymerization and Targeting Specific Properties

Multiblock copolymers (MBCs) are fascinating in the field of biology-polymer chemistry interfaces. Synthesizing libraries of MBCs with tailor-made functionality is challenging as it involves multiple steps. Herein, a simple synthesis, analogous to polyurethane/Michael addition reactions, has been introduced to obtain a library of derivatizable MBCs. Nucleophilic substitution polymerization (S_NP) of poly(ε-caprolactone) and poly(ethylene glycol) blocks containing activated halide termini by primary mono/di/coamines or clickable amines provides functional MBCs. The structure of amines directs the properties of the MBCs. The self-assembly of small molecular weight primary diamine-based MBCs shows controlled release of hydrophobic model guest molecules and therapeutics. The primary diamine (no dangling chain) helps to form MBC micelles having a relatively tight core with a low diffusion property. Antimicrobial property in the MBCs has been introduced by separating the cationic centers from the lipophilic groups using a coamine as a nucleophilic agent and a small molecular weight dihalide as a chain extender. Clickable MBCs were synthesized by changing the structure of the nucleophile to obtain degradable amphiphilic conetworks and hydrogels. Varieties of macromolecular entities could be obtained by switching the nucleophilic agent and introducing a small molecular weight chain extender. This synthesis approach provides an opportunity to tune the chemical functionality, topological structure, and biological properties of macromolecular entities.

Supramolecular nanomotors with "pH taxis" for active drug delivery in the tumor microenvironment

Self-propelled nanomotors demonstrating autonomous motion in biologically relevant fuel are currently being studied to overcome the use of external physical or chemical stimuli as precise delivery agents. In this context, the tumor microenvironment (TME) with slightly acidic pH is used for developing cargo-releasing artificial systems triggered by such conditions. However, there is still a need for fabrication of smart nanomotors that can sense the acidic pH prevalent in the TME rather than using an external fuel source for selective activation and thereafter migrating towards tumors for active drug delivery. Herein, supramolecular assembly-based nanomotors are fabricated by in-situ grown CaCO3 nanoparticles and studied for their motility behaviour in endogenously generated acidic pH by HeLa cells and further exploited as an active delivery vehicle for DOX molecules to the cells for their anticancer efficacy. The nanomotors are activated in slightly acidic pH showcasing "pH taxis" towards tumor cells without the need for any sophisticated/complicated technologies or an external fuel source for active and targeted delivery of drugs.

Polypeptide Nanoparticles with pH-Sheddable PEGylation for Improved Drug Delivery

The variation of tumor microenvironments provides a tool for the construction of stimulus-responsive nanomedicines to enhance drug delivery efficacy. Herein, the assembly of drug-loaded polypeptide nanoparticles (NPs) with pH-sheddable modification of poly(ethylene glycol) (PEG) is prepared to enhance therapeutic efficiency. Poly(l-lysine) and poly(l-glutamic acid) were self-assembled to fabricate polypeptide NPs by electrostatic interactions, followed by PEGylation based on amidation reaction. The NP sizes can be controlled by tuning the molecular weight or the ratio of polypeptides. The PEG coating is cleavable at the tumor acid microenvironment to reverse the surface charge and reduce the NP size, which effectively enhances cell uptake. In addition, the presence of reducing reagent (e.g., glutathione) in cancer cells induces the drug (i.e., cisplatin) release from the polypeptide NPs and subsequently results in the cell toxicity. This reported method highlights the engineering of transformable polypeptide drug carriers, which provides a promising way for enhanced drug delivery efficacy.

Meticulous Doxorubicin Release from pH-Responsive Nanoparticles Entrapped within an Injectable Thermoresponsive Depot

The dual stimuli-controlled release of doxorubicin from gel-embedded nanoparticles is reported. Non-cytotoxic polymer nanoparticles are formed from poly(ethylene glycol)-b-poly(benzyl glutamate) that, uniquely, contain a central ester link. This connection renders the nanoparticles pH-responsive, enabling extensive doxorubicin release in acidic solutions (pH 6.5), but not in solutions of physiological pH (pH 7.4). Doxorubicin-loaded nanoparticles were found to be stable for at least 31 days and lethal against the three breast cancer cell lines tested. Furthermore, doxorubicin-loaded nanoparticles could be incorporated within a thermoresponsive poly(2-hydroxypropyl methacrylate) gel depot, which forms immediately upon injection of poly(2-hydroxypropyl methacrylate) in dimethyl sulfoxide solution into aqueous solution. The combination of the poly(2-hydroxypropyl methacrylate) gel and poly(ethylene glycol)-b-poly(benzyl glutamate) nanoparticles yields an injectable doxorubicin delivery system that facilities near-complete drug release when maintained at elevated temperatures (37 °C) in acidic solution (pH 6.5). In contrast, negligible payload release occurs when the material is stored at room temperature in non-acidic solution (pH 7.4). The system has great potential as a vehicle for the prolonged, site-specific release of chemotherapeutics.

Self-Adaptive Antibacterial Coating for Universal Polymeric Substrates Based on a Micrometer-Scale Hierarchical Polymer Brush System

Surface-tethered hierarchical polymer brushes find wide applications in the development of antibacterial surfaces due to the well-defined spatial distribution and the separate but complementary properties of different blocks. Existing methods to achieve such polymer brushes mainly focused on inorganic material substrates, precluding their practical applications on common medical devices. In this work, a hierarchical polymer brush system is proposed and facilely constructed on polymeric substrates via light living graft polymerization. The polymer brush system with micrometer-scale thickness exhibits a unique hierarchical architecture consisting of a poly(hydroxyethyl methacrylate) (PHEMA) outer layer and an anionic inner layer loading with cationic antimicrobial peptide (AMP) via electrostatic attraction. The surface of this system inhibits the initial adhesion of bacteria by the PHEMA hydration outer layer under neutral pH conditions; when bacteria adhere and proliferate on this surface, the bacterially induced acidification triggers the cleavage of labile amide bonds within the inner layer to expose the positively charged amines and vigorously release melittin (MLT), allowing the surface to timely kill the adhering bacteria. The hierarchical surface employs multiple antibacterial mechanisms to combat bacterial infection and shows high sensitiveness and responsiveness to pathogens. A new paradigm is supplied by this modular hierarchical polymer brushes system for the progress of intelligent surfaces on universal polymer substrates, showing great potential to a promising strategy for preventing infection related to medical devices.

100th Anniversary of Macromolecular Science Viewpoint: Biological Stimuli-Sensitive Polymer Prodrugs and Nanoparticles for Tumor-Specific Drug Delivery

The development of smart polymer vehicles to carry and release cytotoxic drugs to tumor tissues and cells while reducing the exposure of drugs in the blood and healthy organs is a highly challenging task with continuously growing interest from multiple fields, including polymer science, pharmaceutical science, nanotechnology, and clinical oncology. Inspired by the unique tumor microenvironment, such as mild acidity and overexpressed enzymes, functional polymer prodrugs and nanoparticles with reversible charge, detachable PEG shell, activatable ligand, and switchable size have been designed to enhance tumor deposition, tumor penetration, tumor cell uptake, and tumoral drug release. Utilizing biological signals inside tumor cells, such as acidic endo/lysosomal pH, elevated glutathione levels, and reactive oxygen species, responsive polymer prodrugs and nanoparticles with good extracellular stability but fast intracellular disintegration have been engineered for specific intracellular drug release. These biological stimuli-sensitive polymer prodrugs and nanoparticles have shown superior specificity and therapeutic efficacy to nonsensitive counterparts and, in certain cases, even clinically approved systems in varying tumor models. In this Viewpoint, design strategies and recent advances of biological stimuli-responsive polymer prodrugs and nanoparticles for tumor-specific drug delivery will be highlighted, and their challenges and future perspectives will be discussed.

Self-Assembly Protein Superstructures as a Powerful Chemodynamic Therapy Nanoagent for Glioblastoma Treatment

Glioblastoma (GBM) remains a formidable challenge in oncology. Chemodynamic therapy (CDT) that triggers tumor cell death by reactive oxygen species (ROS) could open up a new door for GBM treatment. Herein, we report a novel CDT nanoagent. Hemoglobin (Hb) and glucose oxidase (GOx) were employed as powerful CDT catalysts. Instead of encapsulating the proteins in drug delivery nanocarriers, we formulate multimeric superstructures as self-delivery entities by crosslinking techniques. Red blood cell (RBC) membranes are camouflaged on the protein superstructures to promote the delivery across blood-brain barrier. The as-prepared RBC@Hb@GOx nanoparticles (NPs) offer superior biocompatibility, simplified structure, and high accumulation at the tumor site. We successfully demonstrated that the NPs could efficiently produce toxic ROS to kill U87MG cancer cells in vitro and inhibit the growth of GBM tumor in vivo, suggesting that the new CDT nanoagent holds great promise for treating GBM.

Tumor microenvironment responsive drug delivery systems

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Co-Delivery of Paclitaxel and Interleukin-12 Regulating Tumor Microenvironment for Cancer Immunochemotherapy

In the treatment of malignant tumors, the combination of chemotherapy that can directly kill tumor cells and immunotherapy that can activate the body's immune system and regulate tumor microenvironments is becoming one of the most promising cancer treatments. However, to co-deliver agents with different physicochemical properties for immunochemotherapy is still facing a challenge. Here, nanoparticles are developed for the co-delivery of the hydrophobic chemotherapeutic drug paclitaxel (PTX) and biomacromolecule interleukin-12 (IL-12) through the acid-sensitive material mPEG-Dlink_m -PDLLA and low-temperature expansion effect of Pluronic F127. The nanoparticles encrich in the tumor site, significantly inhibit the growth and metastasis of breast cancer cells 4T1, and prolong the overall survival of tumor-bearing mice. The underlying immune mechanism is further explored. The combination of PTX and IL-12 activates T lymphocytes and NK cells to release IFN-γ, selectively inhibits regulatory T cells and induces M1-type differentiation of tumor-related macrophages, thereby improving tumor immunosuppressive microenvironments. This study may provide an effective strategy for cancer immunochemotherapy through co-delivery of chemotherapeutic drug and immune cytokine by the facile thermo-sponge nanoparticles.

pH-sensitive small molecule nanodrug self-assembled from amphiphilic vitamin B6-E analogue conjugate for targeted synergistic cancer therapy

To promote the targeted cancer therapy, the pH-sensitive small molecule nanodrug self-assembled from amphiphilic vitamin B6-E analogue conjugate was successfully constructed. Herein, water-soluble vitamin B6 with pKa (5.6) was chemically conjugated to lipid-soluble vitamin E succinate (α-TOS), which showed selective cancer cell killing ability and this amphiphilic small molecule vitamin conjugate could self-assemble to be free nanoparticles (NPs) and doxorubicin-loaded NPs (α-TOS-B6-NPs-DOX). The small molecule nanodrugs could perform the following characteristic: (i) stability in the sodium dodecyl sulfonate (SDS) solution and long-term storage stability in PBS via surface negative charge; (ii) tumor accumulation by enhanced penetration and retention (EPR) effect; (iii) improved cellular internalization by means of vitamin B6 transporting membrane carrier (VTC); and (iv) facilitating endosomal escape and rapid drug release for synergistic toxicity to tumor cells via charge reversal and ester hydrolysis at intracellular pH and/or esterase. Moreover, α-TOS-B6-NPs-DOX exhibited long blood circulation stability and significant tumor accumulation and inhibition with the decreased side effects in vivo. Thus, the pH-sensitive small molecule nanodrug self-assembled from amphiphilic vitamin B6-E analogue conjugate could be the potential drug carriers in targeted synergistic cancer therapy.

Transforming Complexity to Simplicity: Protein-Like Nanotransformer for Improving Tumor Drug Delivery Programmatically

It was difficult for nanodrugs to simultaneously meet the contradictory requirements of prolonged circulation time, augmented cellular uptake, rapid lysosome escape, precise drug release, and tumor penetration in tumor drug delivery. We prepared a nanotransformer (DTIG) through assembling doxorubicin, tannic acid, and indocyanine green to overcome this dilemma. Hydrophilic DTIG showed prolonged blood circulation time. Besides, DTIG could be efficiently internalized by tumor cells through transforming into hydrophobic particles in an acidic tumor microenvironment. Subsequently, oversized hydrophobic particles were further formed in acidic lysosomes to escape from it through rupturing the lysosome. These hydrophobic DTIGs could rapidly revert to a smaller hydrophilic nanoassembly and release the payloads in cytoplasm. Similar to denaturation and renaturation of protein, these high-efficiency instantaneous transformations were activated by proton. Besides, photothermal therapy of DTIG promoted drug penetration efficiency in tumor. This optimized drug delivery process of DTIG finally offered potent antitumor efficacy and an obvious advantage on prognosis.

Development of a multifunctional gold nanoplatform for combined chemo-photothermal therapy against oral cancer

Aim: To design and fabricate a multifunctional drug-delivery nanoplatform for oral cancer therapy. Materials & methods: Polyethylene glycol-stabilized, PDPN antibody (PDPN Ab)- and doxorubicin (DOX)-conjugated gold nanoparticles (AuNPs) were prepared and evaluated for their cytotoxicity and antitumor efficacy in both chemotherapy and photothermal therapy. Results: The obtained (PDPN Ab)-AuNP-DOX system presents low toxicity, a high drug loading capacity and cellular uptake efficiency. Both in vitro and in vivo experiments demonstrate that (PDPN Ab)-AuNP-DOX has enhanced antitumor efficacy. Treatment with (PDPN Ab)-AuNP-DOX combined with laser irradiation exhibits superior antitumor effects. Conclusion: This (PDPN Ab)-AuNP-DOX system may be used as a versatile drug-delivery nanoplatform for targeted and combined chemo-photothermal therapy against oral cancer.

A pH and reduction dual-sensitive polymeric nanomicelle for tumor microenvironment triggered cellular uptake and controlled intracellular drug release

Minimal drug leakage during blood circulation and intracellular drug delivery in tumor sites are of great significance in chemotherapeutics. Herein we propose an interlayer crosslinked polymeric micelle with tumor acidity and reduction dual sensitivity for highly efficient drug delivery to cancer cells. A novel copolymer mPEG-C[double bond, length as m-dash]N-PAsp(MEA)-CA was synthesized and self-assembled into a dual-sensitive interlayer-crosslinked micelle (ICM). The micelle was composed of a tumor acidity sheddable PEG outer layer, a reduction-sensitive disulfide-crosslinked interlayer (PAsp(MEA)) and a hydrophobic core of cholic acid (CA) for doxorubicin (DOX) delivery. The nano-sized ICM was stable and showed little drug leakage in a neutral physiological environment. In tumor microenvironments (TMEs) with mild acidity, the PEG outer layer was readily detached due to the hydrolysis of the Schiff base linker, and the surface of the ICM was switched to positively charged to enhance the cellular uptake. Furthermore, inside tumor cells DOX was rapidly released due to the reduction of disulfide bonds by glutathione (GSH). The DOX-loaded ICM exhibited an effective anticancer effect against C6 glioma and reduced side effects both in vitro and in vivo. The study reveals that this pH and reduction dual-sensitive micelle may have great potential to mediate effective anticancer therapy.

Rod-based urchin-like hollow microspheres of Bi2S3: Facile synthesis, photo-controlled drug release for photoacoustic imaging and chemo-photothermal therapy of tumor ablation

Hollow nanostructures have been evoked considerable attention owing to their intriguing hollow interior for important and potential applications in drug delivery, lithium battery, catalysis and etc. Herein, Bi₂S₃ hollow microspheres with rod-based urchin-like nanostructures (denoted as U-BSHM) were synthesized through a facile and rapid ion exchanging method using a particular hard template. The growth mechanism of the U-BSHM has been investigated and illustrated by the morphological evolution of the different samples at early stages. The obtained U-BSHM exhibited strong and wide UV-vis-NIR absorption ability and outstanding photothermal conversion efficiency. Thus, the U-BSHM can be used as spatio-temporal precisely controlled carrier by loading the mixture of 1-tetradecanol (phase change material, PCM) with melting point around 38 °C and hydrophilic chemotherapeutic doxorubicin hydrochloride (denoted as DOX) into the hollow interior to form (PCM + DOX)@Bi₂S₃ nanocomposites (denoted as PD@BS) for photoacoustic (PA) imaging and chemo-photothermal therapy of the tumors. When exposed to 808 nm near infrared light (NIR) laser irradiation, this nanocomposites could elevate the temperature of the surroundings by absorption and conversion of the NIR photons into heat energy, which inducing the triggered release of DOX from the hollow interior once the temperature reach up to the melting point of PCM. The killing efficiency of the chemo-photothermal therapy was systematically validated both in vitro and in vivo. In the meanwhile, the implanted tumor was completely restrained through PA imaging and combined therapies. Therefore, this kind of urchin-like hollow nanostructures would be used as important candidates for the multimodal bioimaging and therapy of tumors.

Dual pH-sensitive nanodrug blocks PD-1 immune checkpoint and uses T cells to deliver NF-κB inhibitor for antitumor immunotherapy

The response to programmed cell death protein-1 (PD-1)/programmed death ligand-1 (PD-L1) blockade in cancer immunotherapy is limited because of multiple immune evasion mechanisms. Here, a previously unknown strategy is proposed to synergize the nuclear factor κB (NF-κB) inhibition and PD-1 blockade for antitumor immunotherapy. A dual pH-sensitive nanocarrier loading curcumin (CUR) and anti-PD-1 monoclonal antibody (aPD-1) may bind to circulating PD-1⁺ T cells and then follow their infiltration into the tumor. Furthermore, the nanodrug bound to PD-1⁺ T cells may be released in the tumor microenvironment, leaving aPD-1 to block PD-1 on T cells and generating a CUR-encapsulated cationic nanodrug that can be easily taken up by tumor cells/tumor associated macrophages (TAMs). Thus, not only the antitumor T cells mediate efficient CUR delivery to tumor but also the efficient CUR delivery promotes the tumor infiltration of antitumor T cells, thereby resulting in effective activation of antitumor immunity.

Dynamic micelles with detachable PEGylation at tumoral extracellular pH for enhanced chemotherapy

Although surface PEGylation of nanomedicines can decrease serum protein adsorption in vivo, it also blocks uptake by tumor cells. This dilemma could be overcome by employing detachably PEGylated strategy at tumoral extracellular microenvironment to achieve improved cellular uptake while prolonged circulation times. Herein, the amphiphilic graft copolymers with pH-sensitive ortho ester-linked mPEG in side chains and polyurethanes in backbone, can self-assemble into the free and doxorubicin (DOX)-loaded micelles. The pH-sensitive micelles could undergo several characteristics as follows: (i) PEGylated shells for stability in sodium dodecyl sulfonate (SDS) solution; (ii) DePEGylation via degradation of ortho ester linkages at tumoral extracellular pH (6.5) for gradually dynamic size changes and effective release of DOX; and (iii) enhanced cellular uptake and cytotoxicity via positive DOX. Moreover, the dynamic micelles with detachable PEGylation could quickly penetrate the centers of SH-SY5Y multicellular spheroids (MCs) and strongly inhibit tumor growth in vitro and in vivo, and might be considered as promising and effective drug carriers in tumor therapy.

Development and disassembly of single and multiple acid-cleavable block copolymer nanoassemblies for drug delivery

Acid-degradable block copolymer-based nanoassemblies are promising intracellular candidates for tumor-targeting drug delivery as they exhibit the enhanced release of encapsulated drugs through their dissociation.

Dual pH-Responsive Polymer Nanogels with a Core-Shell Structure for Improved Cell Association

We report the fabrication of polymer nanogels with a pH-responsive core and a pH-sheddable shell and investigate the pH-dependent cell association of the pH-responsive polymer nanogels. The pH-responsive core composed of poly(2-diisopropylaminoethyl methacrylate) (PDPA) with a pK_a ≈ 6.2 was synthesized by using polymerization in emulsion droplets. The pH-sheddable poly(ethylene glycol) (PEG) shell was coated on the amine-modified PDPA nanogels by an acid-degradable amide bond. The PEG shell is cleavable in response to the acidic tumor microenvironment, and subsequently, the surface charge of the nanogels can be reversed, which effectively enhances cellular association of these nanogels. The reported pH-responsive polymer nanogels provide a promising way for the better understanding of bio-nano interactions and potentially enrich the application of therapeutic delivery for cancer therapy.