Polymeric Prodrug Research Articles

Biomaterials Elicit Pyroptosis Enhancing Cancer Immunotherapy

AbstractCancer immunotherapy has the potential to revolutionize the treatment of malignant tumors, but its effectiveness is limited by the low immune response rate and immune‐related adverse events. Pyroptosis, as an inflammatory programmed cell death type, triggers strong acute inflammatory response and antitumor immunity, converting “cold” tumors to “hot”. Particularly, biomaterials loading pyroptosis inducers targeting the tumor microenvironment to engineer pyroptosis, have achieved great progress in recent years. Herein, the design strategy, mechanism pathway, and role of biomaterials to induce pyroptosis in cancer immunotherapy are comprehensively reviewed. The present review focuses on the application of biomaterials‐induced pyroptosis in cancer immunotherapy, including nanogel, polymer prodrug, nanovesicle, and mesoporous material. Additionally, the synthesis of a series of stimuli‐responsive nanoplatforms, including glutathione‐responsive, pH‐responsive, reactive oxygen species‐responsive, and enzyme‐mimicking catalytic performance, is described. Meanwhile, it augments multiple immune response processes of cell uptake, antigen presentation, T‐cell activation, and expansion. Finally, the perspectives of pyroptosis‐mediated inflammation to break through the tumor vascular basement membrane barrier achieving efficient volcanic penetration of biomaterials are discussed. Artificial intelligence, multi‐omics analysis, and anthropogenic animal models of organoids are presented, aiming to provide guidance and assistance for constructing effective and controllable pyroptosis‐engineered biomaterials and improving tumor immunotherapy.

Acid-degradable magnolol-containing polymeric prodrug micelles for enhanced gastric cancer therapy

Magnolol shows promise as an effective anti-tumor therapeutic agent. Nevertheless, the clinical application of this agent is constrained by its inherent water insolubility and diminished stability. In the present investigation, we have developed a new approach to address these limitations by creating an acid-responsive amphiphilic polymeric prodrug (PMag) that contains acetal bonds and magnolol, and can self-assemble into polymeric micelles (PMag-Ms) in aqueous solutions. We conducted in vitro release studies and observed that the micelles rapidly released magnolol at an acidic pH of 5.0, but only released minimal amounts of magnolol at a neutral pH of 7.4. In vitro investigations performed on gastric cancer cells elucidated that PMag-Ms selectively induced cell apoptosis and G1 phase cell cycle arrest, exhibiting higher efficacy than magnolol alone. Furthermore, in vivo studies confirmed that PMag-Ms exhibited superior inhibition of tumor growth, favorable biocompatibility with organs, increased accumulation in tumor tissues, and enhanced targeting efficiency compared to magnolol. Pharmacokinetic analysis also revealed that PMag-Ms had a longer half-life and extended duration of action in vivo. These results highlight the potential of the synthesized acid-degradable PMag-Ms as a promising therapeutic option for gastric cancer.

Reactive Oxygen Species‐Responsive Polymeric Prodrug Nanoparticles for Selective and Effective Treatment of Inflammatory Diseases (Adv. Healthcare Mater. 29/2023)

Reactive Oxygen Species‐Responsive Polymeric Prodrug Nanoparticles for Selective and Effective Treatment of Inflammatory Diseases (Adv. Healthcare Mater. 29/2023)

Design of carboxymethylcellulose-conjugated polymeric prodrug micelles for enhanced in vivo performance of docetaxel

Docetaxel (DTX) has become one of the most important cytotoxic drugs to treat cancer; nevertheless, its poor hydrophilicity and non-specific distribution of DTX lead to detrimental side effects. In this article, we devised carboxymethylcellulose (CMC)-conjugated polymeric prodrug micelles (mPEG-CMC-DTX PMs) for DTX delivery. The ester-bonded polymeric prodrug, mPEG-CMC-DTX, was synthesized and exhibited the capacity for self-assembling into polymeric micelles. The CMC is profusely substituted and acetylated to promote the coupling rate of DTX. Covalent binding of DTX and CMC through an ester bond can be hydrolyzed to dissociate the bond under the action of esterase in the tumor. The mPEG-CMC-DTX PMs displayed promoted drug loading (>50 %, wt), commendable stability, and sustained release behavior in vitro. The gradual release of the prodrug amplified the selectivity of cytotoxicity between normal cells and tumor cells, mitigating the systemic toxicity of mPEG-CMC-DTX PMs and enabling dose intensification. Notably, mPEG-CMC-DTX PMs demonstrated a superior antitumor efficacy and low systemic toxicity due to the elevated tolerance dosage (even at 40 mg/kg DTX). In summation, mPEG-CMC-DTX PMs harmonized the antitumor efficacy and toxicity of DTX. In essence, innovative perspectives for the rational design of CMC-conjugated polymeric prodrug micelles for the delivery of potently toxic drugs were proffered.

Novel self-degradable prodrug blend thermogel for intratympanic drug delivery to treat inner ear diseases

The use of injectable hydrogel formulations for targeted drug delivery into the inner ear has gained considerable interest. In this study, we introduce a novel self-degradable prodrug blend thermogel system designed to deliver the anti-inflammatory drug, dexamethasone (DEX), in a controlled and safe manner for effective treatment of inner ear diseases. Our approach involves blending a thermogelling polymer, hexanoyl glycol chitosan (HGC), with a polymer prodrug, dexamethasone conjugated glycol chitosan (GC-DEX), to create injectable formulations suitable for intratympanic administration. Through extensive evaluation of the physicochemical and biological properties, we demonstrate that our thermogel formulations exhibit not only excellent thermogelling and injectable characteristics but also controlled release properties, resulting in enhanced drug absorption and prolonged drug concentration in the inner ear. The in vivo T2-weighted MRI Imaging further confirms the long-lasting stability of our thermogel formulations within the tympanic cavity, with a self-degradation period of approximately one month. Notably, guinea pigs treated with the HGC/GC-DEX formulation showed significant hearing recovery merely 7 days after noise exposure, accompanied by a reduction in outer hair cell loss. These promising results indicate the potential of our prodrug blend thermogel as an efficient delivery system for therapeutic agents in the inner ear.

Targeted echogenic and anti-inflammatory polymeric prodrug nanoparticles for the management of renal ischemia/reperfusion injury

Ischemia/reperfusion (IR) injury is an inevitable pathological event occurring when blood is resupplied to the tissues after a period of ischemia. One of major causes of IR injury is the overproduction of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), which mediates the expression of various inflammatory cytokines to exacerbate tissue damages. The overproduced H2O2 could therefore serve as a diagnostic and therapeutic biomarker of IR injury. In this study, poly(boronated methacrylate) (pBMA) nanoparticles were developed as nanotheranostic agents for renal IR injury, which not only generate CO2 bubbles to enhance the ultrasound contrast but also provide potent preventive effects in a H2O2-triggered manner. The surface of pBMA nanoparticles was decorated with taurodeoxycholic acid (TUDCA) that binds P-selectin overexpressed in inflamed tissues. In the mouse model of renal IR injury, TUDCA-coated pBMA (T-pBMA) nanoparticles preferentially accumulated in the injured kidney and markedly enhanced the ultrasound contrast. T-pBMA nanoparticles also effectively prevented renal IR injury by scavenging H2O2 and suppressing the expression of inflammatory cytokines. Treatment progress of IR injury could be also monitored by echogenic T-pBMA nanoparticles. Given their targeting ability, excellent H2O2-responsiveness, anti-inflammatory activity and H2O2-triggered echogenicity, T-pBMA nanoparticles have excellent translational potential for the management of various H2O2-related diseases including IR injury.

Reactive oxygen species-responsive polyprodrug micelles deliver cell cycle regulators for chemosensitization

Combination chemotherapy is a common strategy to enhance treatment efficacy and avoid multidrug resistance (MDR) in clinical practice. However, it is difficult to ensure the co-enrichment and reasonable ratio of synergistic drugs in the lesion site after intravenous administration. Integrating synergistic drugs into a nanocarrier can improve drug stability, targeting, drug loading, and importantly, ensure that synergistic drugs work at one destination. This study uses 10-hydroxycamptothecin (HCPT) to construct a polymeric prodrug micelle, and the demethylcantharidin (DMC) is proportionally encapsulated within the micelle. Triggered by reactive oxygen species (ROS), HCPT and DMC were released simultaneously from the co-delivery platform in tumor cells. DMC promotes abnormal cell division by inhibiting the synthesis of the cell cycle checkpoint kinase Protein phosphatase 2A (PP2A), leading to increased cell vulnerability to DNA damage, disordered replication, and death. The co-delivery platform exhibited satisfactory biosafety and antitumor efficacy in vivo. The proposed co-delivery platform may provide a valuable reference for the translation of clinical combination chemotherapy regimens into nano-drug delivery systems.

The Development of Thermoresponsive Polymeric Simvastatin Prodrug for the Treatment of Experimental Periodontitis in Rats.

Periodontitis (PD) is a severe inflammatory gum pathology that damages the periodontal soft tissue and bone. It is highly prevalent in the US, affecting more than 47% of adults. Besides routine scaling and root planing, there are few effective treatments for PD. Developed as an effective treatment for hyperlipidemia, simvastatin (SIM) is also known for its well-established anti-inflammatory and osteogenic properties, suggesting its potential utility in treating PD. Its clinical translation, however, has been impeded by its poor water-solubility, lack of osteotropicity, and side effects (e.g., hepatoxicity) associated with systemic exposure. To address these challenges, an N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-based thermoresponsive polymeric prodrug of SIM (ProGel-SIM) was developed as a local therapy for PD. Its aqueous solution is free-flowing at 4 °C and transitions into a hydrogel at ∼30 °C, allowing for easy local application and retention. After a thorough characterization of its physicochemical properties, ProGel-SIM was administered weekly into the periodontal pocket of an experimental rat model of PD. At 3 weeks post initiation of the treatment, the animals were euthanized with palate isolated for μ-CT and histological analyses. When compared to dose equivalent simvastatin acid (SMA, active form of SIM) treatment, the rats in the ProGel-SIM treated group showed significantly higher periodontal bone volume (0.34 mm3 vs 0.20 mm3, P = 0.0161) and less neutrophil (PMN) infiltration (P < 0.0001) and IL-1β secretion (P = 0.0036). No measurable side effect was observed. Collectively, these results suggest that ProGel-SIM may be developed as a promising drug candidate for the effective clinical treatment of PD.

A hyaluronic-based prodrug with aggregation-induced emission for drug delivery and cellular imaging

A novel drug molecule (R6) is conjugated to hyaluronic acid (HA) to form a pH-responsive prodrug with aggregation-induced emission (AIE) property. Owing to its amphiphilic nature, the prodrug could self-assemble into nanoparticles (NP) in an aqueous solution. This formulation thereby gave rise to AIE of the R6 moieties which resided in the NP core. The polymer could release the drug at the tumor microenvironment (TME) acidic condition (99% release after 72 h), while remaining stable at the physiological pH. In addition, fluorescence signals by AIE from the NP could be used for cellular imaging. The hyaluronic acid shell can target the overexpressed CD44 receptors in cancer cells, which gives the NP active targeting property. The prodrug showed toxicity against the mouse breast cancer cell line 4T1 while being harmless to the L929 fibroblast cells. Fluorescence microscopy images confirmed the imaging ability of the NP in 4T1 cells. The HA-R6 polymer prodrug promises to be a versatile pH-sensitive drug delivery platform.

Thiol-Responsive Polypeptide Sulfur Dioxide Prodrug Nanoparticles for Effective Tumor Inhibition.

Sulfur dioxide (SO2) based gas therapy has emerged as a novel anticancer therapeutic strategy because of its high therapeutic efficacy and biosafety. To precisely adjust the SO2 content and control gas release, herein, a thiol-responsive polypeptide SO2 prodrug mPEG-block-poly(2-amino-6-(2,4-dinitrophenylsulfonamido)hexanoic acid) (PEG-b-PLys-DNs) was designed and facilely synthesized by polymerization of a novel N-carboxyanhydride SO2-NCA. The anticancer potential of the self-assembled nanoparticles (SO2-NPs) was investigated in detail. First, PEG-b-PLys-DNs were synthesized by ring-opening polymerization of SO2-NCA, which self-assembled into NPs sized 88.4 nm in aqueous. Subsequently, SO2-NPs were endocytosed into 4T1 cells and quickly released SO2 under a high concentration of glutathione in tumor cells. This process depleted cellular glutathione, generated reactive oxygen species, and dramatically increased oxidative stress, which led to cancer cell apoptosis. Finally, the in vivo anticancer efficacy of SO2-NPs was verified in 4T1-tumor-bearing mice. Our results indicated that this novel SO2 polymeric prodrug has great potential in eradicating tumors.

Reactive Oxygen Species-Responsive Polymeric Prodrug Nanoparticles for Selective and Effective Treatment of Inflammatory Diseases.

It is challenging to manage inflammatory diseases using traditional anti-inflammatory drugs due to their limited efficacy and systemic side effects, which are a result of their lack of selectivity, poor stability, and low solubility. Herein, it reports the development of a novel nanoparticle system, called ROS-CA-NPs, which is formed using polymer-cinnamaldehyde (CA) conjugates and is responsive to reactive oxygen species (ROS). ROS-CA-NPs exhibit excellent drug stability, tissue selectivity, and controlled drug release upon oxidative stress activation. Using mouse models of chronic rheumatoid arthritis and acute ulcerative colitis, this study demonstrates that the systemic administration of ROS-CA-NPs results in their accumulation at inflamed lesions and leads to greater therapeutic efficacy compared to traditional drugs. Furthermore, ROS-CA-NPs present excellent biocompatibility. The findings suggest that ROS-CA-NPs have the potential to be developed as safe and effective nanotherapeutic agents for a broad range of inflammatory diseases.

A versatile method to deliver platinum (II) drugs via thiol-ene/yne click reaction of polypeptide

Platinum (II) demonstrates potent anticancer activity, but it is hampered by drawbacks such as poor solubility, facile decomposition, bone marrow suppression, and nephrotoxicity, which severely restrict its clinical use. To overcome these limitations, polymer prodrugs were developed by conjugation of platinum drugs onto polymers. The protective shield provided by polymers enables drugs to evade enzymatic degradation and immune system attacks in the physiological environment, achieving sustained release and long-term efficacy. In this study, we synthesized novel vinyl- or alkynyl-substituted cysteine N-carboxyanhydride (NCA) monomers, followed by the preparation of amphiphilic poly(ethylene glycol)-poly(amino-acid) copolymers through the copolymerization of PEG with the NCAs. Next, 1,2-didentate dicarboxylic groups were introduced into the side chains of the block copolymer by employing the “Thiol-ene” or “Thiol-yne” reactions. These carboxylic acid groups were then chelated with (1R,2R)-1,2-diaminocyclohexane platinum (II)(DACH-Pt) and simultaneously assembled into nanoparticles. The morphology and particle size were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). Remarkably, the chelation of platinum (II) led to a decrease in micellar size. In vitro drug release experiments demonstrated a significantly faster release rate in the intracellular environment (pH 5.0) compared to physiological conditions (pH 7.4). MTT assays confirmed the excellent biocompatibility of the polymer. Moreover, concentration-dependent inhibition of cancer cell growth was observed with poly(amino acid)-platinum (II) chelate micelles. Overall, these findings suggest that self-assembled nanoparticles of poly(amino acid)-platinum (II) chelates hold immense potential for drug delivery applications.

Facile synthesis of GSH-triggered skeleton-cleavable hyperbranched polymer prodrug as unimolecular micelles for tumor-specific camptothecin delivery

Prodrug unimolecular micelles based on dendrimers or hyperbranched polymers have attracted intense interest in tumor chemotherapy. The preparation of the former one is usually cumbersome, while the stable skeleton in the latter one restricts the drug release. Here, GSH-triggered skeleton-cleavable hyperbranched polymer prodrug was designed via a “Bottom-up” construction strategy, by the self-condensing vinyl polymerization (SCVP) of GSH-sensitive prodrug monomer MA-SS-CPT and PEGMA with a GSH-sensitive inimer MA-SS-Br. It could self-assemble into stable unimolecular micelles, possessing GSH-triggered drug release and disintegration of the hyperbranched skeleton. So, they showed an excellent tumor-specific CPT release in the in vitro drug release and consequently tumor-specific cytotoxicity with an enhanced tumor cell growth inhibition than the free CPT.

H2O2-responsive polymer prodrug nanoparticles with glutathione scavenger for enhanced chemo-photodynamic synergistic cancer therapy

The combination of chemotherapy and photodynamic therapy (PDT) based on nanoparticles (NPs) has been extensively developed to improve the therapeutic effect and decrease the systemic toxicity of current treatments. However, overexpressed glutathione (GSH) in tumor cells efficiently scavenges singlet oxygens (1O2) generated from photosensitizers and results in the unsatisfactory efficacy of PDT. To address this obstacle, here we design H2O2-responsive polymer prodrug NPs with GSH-scavenger (Ce6@P(EG-a-CPBE) NPs) for chemo-photodynamic synergistic cancer therapy. They are constructed by the co-self-assembly of photosensitizer chlorin e6 (Ce6) and amphiphilic polymer prodrug P(EG-a-CPBE), which is synthesized from a hydrophilic alternating copolymer P(EG-a-PD) by conjugating hydrophobic anticancer drug chlorambucil (CB) via an H2O2-cleavable linker 4-(hydroxymethyl)phenylboronic acid (PBA). Ce6@P(EG-a-CPBE) NPs can efficiently prevent premature drug leakage in blood circulation because of the high stability of the PBA linker under the physiological environment and facilitate the delivery of Ce6 and CB to the tumor site after intravenous injection. Upon internalization of Ce6@P(EG-a-CPBE) NPs by tumor cells, PBA is cleaved rapidly triggered by endogenous H2O2 to release CB and Ce6. Ce6 can effectively generate abundant 1O2 under 660nm light irradiation to synergistically kill cancer cells with CB. Concurrently, PBA can be transformed into a GSH-scavenger (quinine methide, QM) under intracellular H2O2 and prevent the depletion of 1O2, which induces the cooperatively strong oxidative stress and enhanced cancer cell apoptosis. Collectively, such H2O2-responsive polymer prodrug NPs loaded with photosensitizer provide a feasible approach to enhance chemo-photodynamic synergistic cancer treatment.

Polymeric prodrug by supramolecular polymerization

Cancer has become a major public health problem, and chemotherapy is one of the main methods for treating cancer. However, traditional anticancer drugs have shortcomings such as poor selectivity, short half-life, and large toxic side effects. Recently, polymeric prodrugs with therapeutic moieties covalently bonding to polymers have attracted considerable interests in anticancer field, which can self-assemble into nanodrugs with improved the durability, targeting and bioavailability comparing to traditional anticancer drugs. Nevertheless, the chemical composition of polymeric prodrugs is complex due to the polydispersity of a polymer, which greatly limits their clinical translation. In order to obtain polymeric prodrugs with accurate chemical composition, we designed and synthesized an amphiphilic supramolecular polymeric prodrug based on host-guest interaction, which can self-assemble into nano-sized micelles in aqueous medium for anticancer chemotherapy. The novel supramolecular polymeric prodrug we report in this work can combine the general advantages of polymeric prodrug and small molecular prodrug, which should have a bright future in clinical chemotherapy.

Dextran-doxorubicin prodrug nanoparticles conjugated with CD147 monoclonal antibody for targeted drug delivery in hepatoma therapy

Antibody-drug conjugates (ADCs) are a class of tumor cell-targeting drugs that have developed rapidly in recent years. From the perspective of further improving ADC targeting and developing natural macromolecules as drug carriers, it is still challenging and necessary to try new targeted drug delivery modalities. In this study, we have developed an antibody-modified prodrug nanoparticle based on biomacromolecule dextran (DEX) to delivery antitumour drug doxorubicin (DOX). Firstly, oxidized dextran (ODEX) and DOX were bonded to yield ODEX-DOX via Schiff base reaction, which can self-assemble into nanoparticles (NPs) carrying some aldehyde groups. Subsequently, the amino groups of CD147 monoclonal antibody were bound to the aldehyde groups on the surface of ODEX-DOX NPs, resulting in acid-responsive and antibody-modified CD147-ODEX-DOX NPs with relatively small particle size and high DOX loading. FT-IR, UV-Vis, HPLC, and 1H NMR were used to demonstrate the successful synthesis of polymer prodrug ODEX-DOX NPs and antibody-modified nanomedicine CD147-ODEX-DOX NPs. Dynamic light scattering (DLS) was used to evaluate the stability and the pH responsiveness of ODEX-DOX NPs in different media and tumour microenvironment. The in vitro total release content of DOX reached approximately 70% in PB 5.0 buffer solution after 103 h. Furthermore, the in vivo antitumour efficacy and biodistribution experiments confirmed that CD147-ODEX-DOX NPs could significantly inhibit the growth of HepG2 tumour. All of the results indicate that this acid-sensitive nanomedicine has higher safety and targeting effects. It promises to be an ideal strategy for future targeted drug delivery systems and anticancer therapies.

Cascade-amplified self-immolative polymeric prodrug for cancer therapy by disrupting redox homeostasis.

The amplification of reactive oxygen species (ROS) generation and glutathione (GSH) depletion in cancer cells represents a promising strategy to disrupt redox homeostasis for cancer therapy. Quinone methide and its analogs (QM) have recently been recognized as potential GSH scavengers for anticancer applications; however, an effective QM prodrug is yet to be developed. In this study, we prepare a self-immolative polymeric prodrug (SPP), which could be selectively degraded to generate large quantities of QMs in cancer cells during the spontaneous stepwise head-to-tail degradation of SPP. The amphiphilic SPP is self-assembled into nano-sized micelles, allowing for encapsulating 2-methoxy-β-estradiol (2ME), an anticancer drug that produces a large amount of intracellular ROS. When SPP@2ME, as the cascade-amplified prodrug, is treated on the cancer cells, 2ME is rapidly released at the ROS-rich intracellular environment by degradation of SPP, thus generating more ROS that triggers the degradation of more SPP chains. Such a domino-like cascade-amplified feedback loop significantly amplifies oxidative stress and disrupts the redox homeostasis in cancer cells. This unique strategy provides synergistic anticancer therapeutic efficacy and demonstrates an important perception in innovative and precise nanomedicine.

A Systematic Study of Anti-Osteosarcoma Mechanism of pH-Sensitive Charge-Conversion Cinnamaldehyde Polymeric Prodrug Micelles In Vitro.

Osteosarcoma is an aggressive malignant neoplasm, and it is of great significance to the fabrication and investigation of the anti-tumor mechanism of nanomedicine in the treatment of osteosarcoma. Herein, a cinnamaldehyde polymeric prodrug micelle with pH-sensitive charge-conversion ability (mPEG-b-P(C7-co-CA)) was fabricated, and the anti-osteosarcoma mechanism of mPEG-b-P(C7-co-CA) micelle was investigated. mPEG-b-P(C7-co-CA) micelles were prepared by self-assembly method, and their diameter was 227 nm. mPEG-b-P(C7-co-CA) micelles could regulate the cell cycle and inhibit the proliferation of 143B cells, which was demonstrated by flow cytometry analysis, CCK-8 assay and 5-Ethynyl-2'-deoxyuridine (EdU) staining. The wound-healing assay and transwell assay showed that mPEG-b-P(C7-co-CA) micelles effectively inhibited the migration and invasion of 143B cells. It was proven that mPEG-b-P(C7-co-CA) micelles downregulated the levels of proliferation and apoptosis-related proteins and affected osteosarcoma migration and invasion by inhibiting the epithelial-mesenchymal transition (EMT). In addition, mPEG-b-P(C7-co-CA) micelles can also inhibit the transcriptional activity of the PI3K/Akt signaling pathway. Therefore, these findings provide new evidence for the pharmacological effects of mPEG-b-P(C7-co-CA) micelles.

A ROS-response hyaluronic acid-coated/chitosan polymer prodrug for enhanced tumour targeting efficacy of SN38

Ethyl-10-hydroxycamptothecin (SN38) is a camptothecin derivative with significant anti-tumour therapeutic potential, while the clinical application of SN38 was limited by its poor water solubility and low stability. Herein, a core-shell polymer prodrug hyaluronic acid @chitosan-S-SN38 (HA@CS-S-SN38) was designed by CS-S-SN38 as the core and the HA as the shell, which aims to overcome the limitations of the clinical application of SN38, while realising the high tumour targeting of polymer prodrug and the controllable release of drug in tumour cells. HA@CS-S-SN38 showed the high responsiveness of the tumour microenvironment and the safe stability of blood circulation. Furthermore, HA@CS-S-SN38 exhibited the begin uptake efficiency and favourable apoptosis in the 4T1 cells. More importantly, compared with irinotecan hydrochloride trihydrate (CPT-11), HA@CS-S-SN38 significantly improved the conversion efficiency of the prodrug to SN38, and showed excellent tumour targeting and retention in vivo by combining passive and active targeting strategies. In tumour-bearing mice treatment, HA@CS-S-SN38 showed the perfect anti-tumour effect and therapeutic safety. These results indicated that the polymer prodrug designed by ROS-response/HA-modification strategy is a safe and efficient drug delivery system, which provides a new idea for clinical utilisation of SN38 and warrants further evaluation.

PH-sensitive charge-conversion cinnamaldehyde polymeric prodrug micelles for effective targeted chemotherapy of osteosarcoma in vitro.

Introduction: Chemotherapy is a common strategy for the treatment of osteosarcoma. However, its therapeutic efficacy is not ideal due to the low targeting, lowbioavailability, and high toxicity of chemotherapy drugs. Nanoparticles can improve the residence time of drugs at tumor sites through targeted delivery. This new technology can reduce the risk to patients and improve survival rates. To achieve this goal, we developed a pHsensitive charge-conversion polymeric micelle [mPEG-b-P(C7-co-CA) micelles] for osteosarcoma-targeted delivery of cinnamaldehyde (CA). Methods: First, an amphiphilic cinnamaldehyde polymeric prodrug [mPEG-b-P(C7-co-CA)] was synthesized through Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization and post-modification, and self-assembled into mPEG-b-P(C7-co-CA) micelles in an aqueous solution. The physical properties of mPEG-b-P(C7-co-CA) micelles, such as critical micelle concentration (CMC), size, appearance, and Zeta potential were characterized. The CA release curve of mPEG-b-P(C7-co-CA) micelles at pH 7.4, 6.5 and 4.0 was studied by dialysis method, then the targeting ability of mPEG-b-P(C7-co-CA) micelles to osteosarcoma 143B cells in acidic environment (pH 6.5) was explored by cellular uptakeassay. The antitumor effect of mPEG-b-P(C7-co-CA) micelles on 143B cells in vitro was studied by MTT method, and the level of reactive oxygen species (ROS) in 143B cells after mPEG-b-P(C7-co-CA) micelles treatment was detected. Finally, the effects of mPEG-b-P(C7-co-CA) micelles on the apoptosis of 143B cells were detected by flow cytometry and TUNEL assay. Results: An amphiphilic cinnamaldehyde polymeric prodrug [mPEG-b-P(C7-co-CA)] was successfully synthesized and self-assembled into spheric micelles with a diameter of 227 nm. The CMC value of mPEG-b-P(C7-co-CA) micelles was 25.2 mg/L, and it showed a pH dependent release behavior of CA. mPEG-b-P(C7-co-CA) micelles can achieve chargeconversion from a neutral to a positive charge with decreasing pHs. This charge-conversion property allows mPEG-b-P(C7-co-CA) micelles to achieve 143B cell targeting at pH 6.5. In addition, mPEG-b-P(C7-co-CA) micelles present high antitumor efficacy and intracellular ROS generation at pH 6.5 which can induce 143B cell apoptosis. Discussion: mPEG-b-P(C7-co-CA) micelles can achieve osteosarcoma targeting effectively and enhance the anti-osteosarcoma effect of cinnamaldehyde in vitro. This research provides a promising drug delivery system for clinical application and tumor treatment.