Polymer Conjugate as the New Promising Drug Delivery System for Combination Therapy against Cancer.

This review highlights the advantages of combination therapy using polymer conjugates as drug delivery systems for cancer treatment. In this review, the specific structures and materials of polymer conjugates, as well as the different types of combination chemotherapy strategies, are discussed. Specific targeting strategies, such as monoclonal antibody therapy and small molecule ligands, are also explored. Additionally, self-assembled polymer micelles and overcoming multidrug resistance are described as potential strategies for combination therapy. The assessment of combinational therapeutic efficacy and the challenges associated with polymer conjugates are also addressed. The future outlook aims to overcome these challenges and improve the effectiveness of drug delivery systems for combination therapy. The conclusion emphasizes the potential of polymer conjugates in combination therapy while acknowledging the need for further research and development in this field.

Mitochondria-Targeting Polyprodrugs to Overcome the Drug Resistance of Cancer Cells by Self-Amplified Oxidation-Triggered Drug Release.

The multi-drug resistance (MDR) of cancers is one of the main barriers for the success of diverse chemotherapeutic methods and is responsible for most cancer deaths. Developing efficient approaches to overcome MDR is still highly desirable for efficient chemotherapy of cancers. The delivery of targeted anticancer drugs that can interact with mitochondrial DNA is recognized as an effective strategy to reverse the MDR of cancers due to the relatively weak DNA-repairing capability in the mitochondria. Herein, we report on a polyprodrug that can sequentially target cancer cells and mitochondria using folic acid (FA) and tetraphenylphosphonium (TPP) targeting moieties, respectively. They were conjugated to the terminal groups of the amphiphilic block copolymer prodrugs composed of poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) and copolymerized monomers containing cinnamaldehyde (CNM) and doxorubicin (DOX). After self-assembly into micelles with the suitable size (∼30 nm), which were termed as TF@CNM + DOX, and upon intravenous administration, the micelles can accumulate in tumor tissues. After FA-mediated endocytosis, the endosomal acidity (∼pH 5) can trigger the release of CNM from TF@CNM + DOX micelles, followed by enhanced accumulation into the mitochondria via the TPP target. This promotes the overproduction of reactive oxygen species (ROS), which can subsequently enhance the intracellular oxidative stress and trigger ROS-responsive release of DOX into the mitochondria. TF@CNM + DOX shows great potential to inhibit the growth of DOX-resistant MCF-7 ADR tumors without observable side effects. Therefore, the tumor and mitochondria dual-targeting polyprodrug design represents an ideal strategy to treat MDR tumors through improvement of the intracellular oxidative level and ROS-responsive drug release.

The effect of spacers in dual drug-polymer conjugates toward combination therapeutic efficacy.

Recently, a great effort has been made to perfect the therapeutic effect of solid tumor, from single-agent therapy to combined therapy and many other polymer-drug conjugations with dual or more anticancer agents due to their promising synergistic effect and higher drug level accumulation towards tumor tissues. Different polymer-drug spacers present diverse therapeutic efficacy, therefore, finding an appropriate spacer is desirable. In this study, dual drugs that are doxorubicin (DOX) and mitomycin C (MMC) were conjugated onto a polymer carrier (xyloglucan) via various peptide or amide bonds, and a series of polymers drug conjugates were synthesized with different spacers and their effect on tumor treatment efficacy was studied both in vitro and in vivo. The result shows that the synergistic effect is better when using different linker to conjugate different drugs rather than using the same spacer to conjugate different drugs on the carrier. Particularly, the finding of this works suggested that, using peptide bond for MMC and amide bond for DOX to conjugate dual drugs onto single XG carrier could improve therapeutic effect and synergy effect. Therefore, in polymer-pharmaceutical formulations, the use of different spacers to optimize the design of existing drugs to enhance therapeutic effects is a promising strategy.

Tumor-dilated polymersome nanofactories for enhanced enzyme prodrug chemo-immunotherapy.

Combination chemo-immunotherapy of cancers has attracted great attention due to its significant synergistic antitumor effect. The response rates and therapeutic efficacy of immunotherapy can be enhanced significantly after proper combination with chemotherapy. However, chemo-immunotherapy is frequently limited by severe immune-related adverse events and systemic side toxicity. In this report, efficient nanofactory-directed enzyme prodrug chemo-immunotherapy is demonstrated based on enzyme-loaded tumor-dilatable polymersomes with optimized membrane cross-linking density. Upon intravenous injection of the nanofactories, they can passively accumulate at the tumor site. The tumor pH-responsive nanofactories can swell from ~100 nm to ~200 nm under the trigger of tumor acidity, leading to prolonged retention of up to one week inside tumor tissues. Simultaneously, the membrane permeability of the nanofactories has improved significantly, which allows hydrophilic small molecules to pass across the membranes while keeping the enzymes in the inner cavities. Subsequently, the non-toxic prodrug mixtures of chemo-immunotherapy are administrated three times within 6 days, which are in situ activated by the nanofactories selectively at tumor sites. Activated chemotherapeutic drugs kill cancer cells and generate tumor-associated antigens to promote the maturation of dendritic cells. Activated indoleamine 2, 3-dioxygenase 1 inhibitors reverse the immunosuppressive tumor microenvironment. Finally, primary tumors can be effectively suppressed while causing minimal systemic toxicity. The distant tumors that are established after treatment can also be inhibited completely via activation of antitumor immunity in mice. Thus, the tumor-dilatable polymersome nanofactories with long-term intratumoral retention offer a promising paradigm for enhanced enzyme prodrug chemo-immunotherapy.

Hypoxia-Responsive Polyprodrug Nanocarriers for Near-Infrared Light-Boosted Photodynamic Chemotherapy.

The hypoxia environment inside tumors is tightly associated with tumor growth, metastasis, and drug resistance. However, the heterogonous distribution of hypoxic areas limits the efficacy of hypoxia-activatable drug delivery systems. Herein, we report the hypoxia-activable block copolymer polyprodrugs, which are composed of poly(ethylene glycol) (PEG) and copolymerized segments of ortho-nitrobenzyl-linked camptothecin (CPT) methacrylate and 2-(piperidin-1-yl)ethyl methacrylate (PEMA) monomers. After self-assembly in aqueous solution, indocyanine green (ICG) photosensitizers were encapsulated to formulate ICG-loaded micellar nanoparticles (ICG@CPTNB) for near-infrared (NIR) light-boosted photodynamic therapy (PDT), tumor hypoxia aggravation, and responsive drug activation. Through intravenous injection and prolonged blood circulation, the nanoparticles can accumulate into tumor efficiently. Tumor acidity-triggered charge transition of PEMA units remarkably promotes cellular internalization of the nanoparticles. Upon exposure to NIR laser irradiation, ICG inside the nanoparticles produced reactive oxygen species (ROS) along with local hypothermia. Simultaneously, the oxygen consumption during ROS production aggravated the intratumoral hypoxia, which amplified hypoxia-responsive self-immolative CPT release from the nanoparticles. The combined photodynamic chemotherapy using hypoxia-responsive polyprodrug nanoparticles, ICG@CPTNB, overcomes the limitations of single therapy of hypoxia-activable prodrugs or PDT, which remarkably improves the efficiency of tumor growth suppression.

Ferrocene-containing polymersome nanoreactors for synergistically amplified tumor-specific chemodynamic therapy.

Chemodynamic therapy (CDT) has been proposed to convert tumoral H2O2 into toxic hydroxyl radicals (OH) via Fenton or Fenton-like reactions for antitumor efficacy, which is frequently limited by low H2O2 concentrations or lack of enough metal ions inside tumor tissues. In this report, we present ferrocene-containing responsive polymersome nanoreactors via loading glucose oxidase (GOD) and hypoxia-activable prodrug tirapazamine (TPZ) in the inner aqueous cavities. After intravenous injection, the polymersome nanoreactors with the optimized nanoparticle size of ~100 nm and poly(ethylene glycol) corona facilitate tumor accumulation. The tumor acidic microenvironment can trigger the permeability of the polymersome membranes to activate the nanoreactors and release the loaded TPZ prodrugs. Tumor oxygen and glucose can enter the polymersome nanoreactors and are transformed into H2O2 under the catalysis of GOD, which are further converted into OH via Fenton reaction under catalysis of ferrocene moieties. The oxygen consumption can aggravate tumor hypoxia to activate hypoxia-responsive TPZ prodrugs which can produce benzotriazinyl (BTZ) radicals and OH. All the produced radicals synergistically kill tumor cells via the amplified CDT and suppress the tumor growth efficiently. Thus, the ferrocene-containing responsive polymersome nanoreactors loading GOD and TPZ represent a potent nanoplatform to exert amplified CDT for improved anticancer efficacy.

Cisplatin resistance reversal in lung cancer by tumor acidity-activable vesicular nanoreactors via tumor oxidative stress amplification.

Drug resistance of cisplatin significantly limits its therapeutic efficacy in clinical applications against different cancers. Herein, we develop a novel strategy to overcome cisplatin drug resistance through sensitizing cisplatin-resistant human lung cancer cells (A549R) under amplified oxidative stress using a vesicular nanoreactor for simultaneous cisplatin delivery and H2O2 generation. We engineer the nanoreactor by the self-assembly of the amphiphilic diblock copolymers to co-deliver glucose oxidase (GOD) and cisplatin (Cis) (Cis/GOD@Bz-V). Cis/GOD@Bz-V was rationally designed to stay impermeable during blood circulation while mild acidity (pH 6.5-6.8) can activate its molecular-weight selective membrane permeability and release cisplatin locally. Diffusion of small molecules such as oxygen and glucose across the membranes can induce the in situ generation of superfluous H2O2 to promote cellular oxidative stress and sensitize A549R cells via activation of pro-apoptotic pathways. Cis/GOD@Bz-V nanoreactors could effectively kill A549R at pH 6.8 in the presence of glucose by the combination of H2O2 generation and cisplatin release. Growth of A549R xenograft tumors can be inhibited efficiently without the obvious toxic side effects via the systemic administration of Cis/GOD@Bz-V. Accordingly, the tumor acidity-activable cisplatin-loaded nanoreactors show great potential to enhance the therapeutic efficacy against cisplatin-resistant cancers.

ROS-Responsive Polymeric Nanocarriers with Photoinduced Exposure of Cell-Penetrating Moieties for Specific Intracellular Drug Delivery.

In situ modulation of the surface properties on the micellar drug delivery nanocarriers offers an efficient method to improve the drug delivery efficiency into cells while maintaining stealth and stability during blood circulation. Light has been demonstrated to be a temporally and spatially controllable tool to improve cellular internalization of nanoparticles. Herein, we develop reactive oxygen species (ROS)-responsive mixed polymeric micelles with photoinduced exposure of cell-penetrating moieties via photodynamic ROS production, which can facilitate cellular internalization of paclitaxel (PTX) and chlorin e6 (Ce6)-coloaded micelles for the synergistic effect of photodynamic and chemotherapy. The thioketal-bond-linked block polymers poly(ε-caprolactone)-TL-poly(N,N-dimethylacrylamide) (PCL-TL-PDMA) with a long PDMA block are used to self-assemble into mixed micelles with PCL-b-poly(2-guanidinoethyl methacrylate) (PCL-PGEMA) consisting of a short PGEMA block, which are further used to coencapsulate PTX and Ce6. After intravenous injection, prolonged blood circulation of the micelles guarantees high tumor accumulation. Upon irradiation by 660 nm light, ROS production of the micelles by Ce6 induces cleavage of PDMA to expose PGEMA shells for significantly improved cellular internalization. The combination of photodynamic therapy and chemotherapy inside the tumor cells achieves improved antitumor efficacy. The design of ROS-responsive mixed polymeric nanocarriers represents a novel and efficient approach to realize both long blood circulation and high-efficiency cellular internalization for combined photodynamic and chemotherapy under light irradiation.

Polymersome nanoreactors with tumor pH-triggered selective membrane permeability for prodrug delivery, activation, and combined oxidation-chemotherapy.

Therapeutic nanoreactors are currently emerging as promising nanoplatforms to in situ transform inert prodrugs into active drugs. Nevertheless, it is still challenging to engineer a nanoreactor with balanced key features of tunable selective membrane permeability and structural stability for prodrug delivery and activation in diseased tissues. Herein, we present a facile strategy to engineer a polymersome nanoreactor with tumor-specific tunable membrane permeability to load both hydrophobic phenylboronic ester-caged anticancer prodrugs (e.g., camptothecin or paclitaxel prodrug) and hydrophilic glucose oxidase (GOD) in the membranes and cavities, respectively. The nanoreactors maintain inactive during blood circulation and in normal tissues. Upon accumulation in tumors, the mild acidic microenvironment triggers selective membrane permeability to allow small molecules (glucose and O2) to diffuse across the membrane and react under the catalysis of GOD. The massively generated H2O2 triggers in situ transformation of innocuous prodrugs into toxic parental drugs through cleavage of the self-immolative degradable caging groups. The developed system showed significantly enhanced antitumor efficacy by H2O2 production and prodrug activation via combined oxidation-chemotherapy. The well-devised polymersome nanoreactors with tumor-pH-tunable membrane permeability to coload H2O2-responsive prodrug and GOD represent a novel strategy to realize prodrug delivery and activation for enhanced therapeutic efficacy with low side toxicity.

Integrated block copolymer prodrug nanoparticles for combination of tumor oxidative stress amplification and ROS-responsive drug release.

In tumor tissues, reactive oxygen species (ROS) level is significantly higher than that in normal tissues, which has been frequently explored as the specific stimulus to trigger drug release. However, the low intrinsic ROS concentration and heterogeneous distribution in tumor tissues hinder the applications as the stimulus for drug delivery. Herein, we developed integrated nanoparticles to remold tumor microenvironment via specific amplification of the tumor oxidative stress and simultaneously realize ROS-responsive drug release. The amphiphilic block copolymer prodrugs composed of poly(ethylene glycol) and polymerized methacrylate monomer containing thioketal-linked camptothecin (CPT) were synthesized and self-assembled to form core-shell micelles for encapsulation of ß-lapachone (Lapa@NPs). After tumor accumulation and internalization into tumor cells post systemic administration of Lapa@NPs, Lapa can selectively induce remarkable ROS level increase via the catalysis of NAD(P)H: quinone oxidoreductase-1 (NQO1) enzyme overexpressed in cancer cells. Subsequently, enhanced ROS concentration would trigger the cleavage of thioketal linkers to release drug. The released CPT together with high ROS level achieved a synergistic therapy to suppress tumor growth. Moreover, Lapa@NPs exhibited superior biosafety due to the tumor-specific activation of the cascade reaction. Accordingly, Lapa@NPs represent a novel polymer prodrug design and drug release strategy via tumor-specific oxidative stress amplification and subsequent ROS-responsive drug release.

Reduction-Responsive Polymer Prodrug Micelles with Enhanced Endosomal Escape Capability for Efficient Intracellular Translocation and Drug Release.

High-efficiency endosomal escape of drug delivery nanocarriers for glutathione-based reduction-responsive drug release in cytoplasm can significantly enhance the therapeutic efficacy of the loaded therapeutic drugs. In this report, we develop the polymer prodrug micelles self-assembled from the amphiphilic block copolymer prodrug, PEG-b-P(CPTM-co-ImOAMA), consisting of poly(ethylene glycol) (PEG) and copolymerized segments of disulfide bond-linked camptothecin methacrylate monomer (CPTM) and 1-(1H-imidazole-4-yl)-2-(octylamino)-2-oxoethyl methacrylate (ImOAMA). After cellular internalization through endocytosis, PEG-b-P(CPTM-co-ImOAMA) micelles are trapped in endosomes inside the tumor cells. The endosomal pH can trigger the protonation of the imidazole moieties of PImOAMA segments, which may facilitate endosome escape through the proton sponge effect and the improved interactions between protonated imidazole groups, hydrophobic octyl moieties, and endosomal membranes. Moreover, the high concentration of glutathione in the cytoplasm of cancer cells can trigger the release of active camptothecin (CPT) through cleavage of the disulfide linkers from PCPTM. The in vitro results showed that PEG-b-P(CPTM-co-ImOAMA) micelles could be effectively internalized into cells followed by endosomal escape, which contributed to the significantly improved cancer cell-killing efficacy. Moreover, in vivo studies confirmed that the PEG-b-P(CPTM-co-ImOAMA) micelles realized efficient tumor growth inhibition without obvious side toxicity. Therefore, the proposed reduction-responsive polymeric prodrug micelles with high endosomal escape capability could provide a brilliant potential in a drug delivery platform to achieve enhanced antitumor efficacy.

Hypoxia-responsive block copolymer radiosensitizers as anticancer drug nanocarriers for enhanced chemoradiotherapy of bulky solid tumors.

Radiosensitizers play an important role in the clinical radiotherapy of hypoxic solid tumors to improve therapeutic efficacy. However, the in vivo performance of clinically used small-molecule radiosensitizers is commonly compromised by low bioavailability in hypoxic tumor regions. Herein, amphiphilic block copolymer radiosensitizers are prepared from clinically approved poly(ethylene glycol)-block-poly(l-glutamic acid) (PEG-b-PLG) and metronidazole (MN) to obtain MN-grafted PEG-b-PLG (PEG-b-P(LG-g-MN)) via condensation reaction, which can self-assemble into core-shell micelles as nanoparticle-formulated radiosensitizers in aqueous solution. The radiosensitizers are demonstrated to possess significantly higher sensitization enhancement ratio (SER) of 2.18 and potent in vivo tumor ablation capability upon exposure to electron beam irradiation compared with clinically used sodium glycididazole (GS) with SER of 1.32. Moreover, after optimizing the ratios of carboxyl and MN groups, PEG-b-P(LG-g-MN) micelles can be used to encapsulate doxorubicin (DOX@HMs) efficiently. Hypoxia-responsive structural transformation of MN into hydrophilic aminoimidazole triggers fast DOX release from DOX@HMs. After intravenous injection of DOX@HMs, potent ablation capability against bulky solid tumors (∼500 mm3) is realized at a low radiation dose (4 Gy) via enhanced chemoradiotherapy. Therefore, the developed novel amphiphilic block copolymer radiosensitizers can be concurrently used as high-efficiency radiosensitizers and hypoxia-responsive DOX nanocarriers for enhanced chemoradiotherapy.

Therapeutic Nanoreactors as In Vivo Nanoplatforms for Cancer Therapy.

Therapeutic nanoreactors have been proposed as nanoplatforms to treat diseases through in situ production of therapeutic agents. When this treatment strategy is applied in cancer therapy, it can efficiently produce highly toxic anticancer drugs in situ from low-toxic prodrugs or some biomolecules in tumor tissues, which can maximize the therapeutic efficacy with a significantly low systemic toxicity. An ideal therapeutic nanoreactor can provide the reaction space, protect the loaded fragile catalysts, target the desired pathological site, and be selectively activated. In this minireview, we highlight the recent advances concerning the applications of therapeutic nanoreactors as in vivo nanoplatforms particularly in cancer therapy. Herein, the therapeutic nanoreactors are discussed on the basis of treatment strategies and various nanoparticles. Specifically, the treatment strategies of nanoreactors including single enzyme, single enzyme with chemodrugs, and multienzymes, as well as varying types of engineered nanoparticle-loaded active catalysts, primarily including liposomes, polymersomes, polymeric micelles, inorganic nanoparticles, and metal-organic framework (MOF) architectures, are documented and briefly discussed. Finally, we elucidate the current challenges to be addressed toward further development and translation into clinical applications of these therapeutic nanoreactors in cancer therapy.

A robust strategy for preparation of sequential stimuli-responsive block copolymer prodrugs via thiolactone chemistry to overcome multiple anticancer drug delivery barriers.

Block copolymer prodrugs (BCPs) have attracted considerable attentions in clinical translation of nanomedicine owing to their self-assembly into well-defined core-shell nanoparticles for improved pharmacokinetics, stability in blood circulation without drug leakage, and optimized biodistribution. However, a cascade of physiological barriers against specific delivery of drugs into tumor cells limit the final therapeutic efficacy. Herein, we report a robust and facile strategy based on thiolactone chemistry to fabricate well-defined BCPs with sequential tumor pH-promoted cellular internalization and intracellular stimuli-responsive drug release. A series of BCPs were prepared through one-pot synthesis from clinically used small molecule anticancer drugs. The ring-opening reaction of drug-conjugated thiolactones releases mercapto groups via aminolysis by N-(3-aminopropyl)-imidazole, which further react with poly(ethylene glycol)-block-poly(pyridyldisulfide ethylmethacrylate) (PEG-PDSEMA) to produce imidazole and disulfide bonds-incorporated BCPs. Taking paclitaxel (PTX) for example, PTX BCPs exhibited high drug-loading content (>50%) and low critical micellization concentration (5 × 10-3 g/L), which can self-assemble into micellar nanoparticles in aqueous solution with a small size (∼40 nm). The nanoparticles showed high tumor accumulation and uniform distribution in hypopermeable tumors via systemic administration. Meanwhile, imidazole moieties endow nanoparticles tumor pH-sensitive charge transition from nearly neutral to positive, which promoted cellular internalization. Disulfide bonds can be cleaved by intracellular glutathione (GSH) of cancer cells, which accelerate the release of active PTX drug inside cells. Finally, highly aggressive murine breast cancer 4T1 tumor and hypopermeable human pancreatic adenocarcinoma BxPC3 tumor were completely ablated after treatment by PTX BCP nanoparticles. Consequently, the robust and facile preparation strategy based on thiolactone chemistry represents an efficient approach to construct multifunctional BCPs for better therapeutic efficacy via addressing multiple physiological barriers.

Thiolactone Chemistry-Based Combinatorial Methodology to Construct Multifunctional Polymers for Efficacious Gene Delivery.

Hydrophobic segments and amino moieties in polymeric nonviral gene vectors play important roles in overcoming a cascade of barriers for efficient gene delivery. However, it remains a great challenge to facilely construct well-defined multifunctional polymers through optimization of the amino and hydrophobic groups. Herein, we choose thiolactone chemistry to perform the ring opening reaction of varying hydrophobic groups-modified thiolactones by various amines to generate mercapto groups for further Michael addition reaction with poly[2-(acryloyloxy)ethyl methacrylate] (PAOEMA). Based on the combinatorial methodology, a series of multifunctional polymers were prepared and screened. The polymer (P3D) from tetraethylenepentamine and heptafluorobutyric acid-functionalized thiolactone is the most efficacious one with significantly higher gene transfection efficiency and lower cytotoxicity compared with polyethylenimine (PEI) (branched average Mw ∼ 25 000 Da) and Lipofectamine 2000. Cellular uptake and intracellular distribution studies indicate that P3D complexes show high-efficiency endocytosis and excellent endosomal escape. Accordingly, thiolactone chemistry-based combinatorial methodology allows for facile integration of multifunctional groups to prepare simultaneous efficacious and low-cytotoxic gene delivery vectors.

Matrix Metalloproteinase-Responsive Multifunctional Peptide-Linked Amphiphilic Block Copolymers for Intelligent Systemic Anticancer Drug Delivery.

The amphiphilic block copolymer anticancer drug nanocarriers clinically used or in the progress of clinical trials frequently suffer from modest final therapeutic efficacy due to a lack of intelligent features. For example, the biodegradable amphiphilic block copolymer, poly(ethylene glycol)-b-poly(d,l-lactide) (PEG-PDLLA) has been approved for clinical applications as a paclitaxel (PTX) nanocarrier (Genexol-PM) due to the optimized pharmacokinetics and biodistribution; however, a lack of intelligent features limits the intracellular delivery in tumor tissue. To endow the mediocre polymer with smart properties via a safe and facile method, we introduced a matrix metalloproteinase (MMP)-responsive peptide GPLGVRGDG into the block copolymer via efficient click chemistry and ring-opening polymerization to prepare PEG-GPLGVRGDG-PDLLA (P1). P1 was further self-assembled into micellar nanoparticles (NPs) to load PTX, which show MMP-2-triggered dePEGylation due to cleavage of the peptide linkage. Moreover, the residual VRGDG sequences are retained on the surface of the NPs after dePEGylation, which can serve as ligands to facilitate the cellular uptake. The cytotoxicity of PTX loaded in P1 NPs against 4T1 cells is significantly enhanced as compared with free PTX or PTX-loaded PEG-GPLGVRG-PDLLA (P2) and PEG-PDLLA (P3) NPs. In vivo studies confirmed that PTX-loaded P1 NPs show prolonged blood circulation, which are similar to P2 and P3 NPs but exhibit more-efficient accumulation in the tumor site. Ultimately, PTX-loaded P1 NPs display statistically significant improvement of antitumor activity against tumor-bearing mice via systemic administration. Therefore, the strategy by facile incorporation of a responsive peptide linkage between PEG and PDLLA is a promising approach to improving the therapeutic efficacy of anticancer-drug-loaded amphiphilic block copolymer micelles.

Intracellular delivery of 10-hydroxycamptothecin with targeted nanostructured lipid carriers against multidrug resistance.

10-Hydroxycamptothecin (HCPT) is a clinical therapy agent against hepatoma. The chemotherapy of HCPT is strongly obstructed by the emergence of multidrug resistance (MDR), serious systemic toxicity, malfunction of rapid phagocytic and renal clearance disorder which are undesirable for its chemotherapy. In this paper, a drug delivery system (DDS) for HCPT has been developed in order to overcome MDR. Nanostructured lipid carriers (NLC) coated with xyloglucan (XG) was prepared by soya oil and XG consisting of side chains with galactose residues, a terminal moiety that can be used to target HCPT to hepatoma. The therapeutic potential of XG-NLC/HCPT was investigated on HepG2/HCPT cells and on human tumor xenograft nude mouse model (implanted with HepG2/HCPT cells). XG-NLC/HCPT not only indicated superior cytotoxicity against the drug resistant HepG2 cells but also in vivo, generated a higher therapeutic effect. Systemic toxicity study demonstrated that the carrier reduced systemic toxicity. XG-NLC/HCPT proved a great potential to serve as DDS to overcome MDR of HepG2/HCPT cells. These results suggested that XG NLC/HCPT represent a promising carrier for drug delivery to the hepatoma and reverse the drug resistant of HepG2 cells and XG could be exploited as a potential targeting device for liver tissue.

Precise Ratiometric Control of Dual Drugs through a Single Macromolecule for Combination Therapy.

A major challenge of combinatorial therapy is the unification of the pharmacokinetics and cellular uptake of various drug molecules with precise control of the dosage thereby maximizing the combined effects. To realize ratiometric delivery and synchronized release of different drugs from a single carrier, a novel approach was designed in this study to load dual drugs onto the macromolecular carrier with different molar ratio by covalently preconjugating dual drugs through peptide linkers to form drug conjugates. In contrast to loading individual types of drugs separately, these drug conjugates enable the loading of dual drugs onto the same carrier in a precisely controllable manner to reverse multidrug resistance (MDR) of human hepatoma (HepG2) cells. As a proof of concept, the synthesis and characterization of xyloglucan-mitomycin C/doxorubicin (XG-MMC/DOX) conjugates were demonstrated. This approach enabled MMC and DOX to be conjugated to the same polymeric carrier with precise control of drug dosage. The cytotoxicity and combinatorial effects were significantly improved compared to the cocktail mixtures of XG-MMC and XG-DOX as well as the individual conjugate of the mixture. Moreover, the results also showed that there was an optimum ratio of dual drugs showing the best cytotoxicity effect and greatest synergy among other tested polymeric conjugate formulations.

In vivo immunological activity of carboxymethylated-sulfated (1→3)-ß-D-glucan from sclerotium of Poria cocos.

ß-Glucans are one of the polysaccharides known as biological response modifiers extracted from the sclerotium of Poria cocos which has been used for several decades as Traditional Chinese Medicine. Due to its ability to activate immune system, it can be applied in chemotherapy after being chemically modified. In this study, sulfated (1→3)-ß-D-glucan (S-P), carboxymethyl (1→3)-ß-D-glucan (CMP), and carboxymethylated-sulfated (1→3)-ß-D-glucan (S-CMP), which are (1→3)-ß-D-glucan derivatives were synthesized. The current study was aimed to investigate in vivo potential immunological activity of S-CMP in mice. In addition, mice were separately treated with S-P, CMP and S-CMP to evaluate the relationship between single and multiple functional groups. Interestingly, S-CMP exhibited the best in vivo immunological activities and the highest inhibition rate against the implanted HepG2 tumor in BALB/c mice, with significant increase in serum hemolysin antibody titer, spleen antibody production as well as delayed type hypersensitivity compared with S-P and CMP. Furthermore, it was assumed that simultaneous introduction of carboxymethyl and sulfate groups also had great potential effect on antioxidant activity, as substantial decrease in malondialdehyde (MDA) content was remarked. Therefore, it may suggest that S-CMP has better immunological and anti-tumor effects on mice in vivo.