Preclinical evaluation of antitumor activity of acid-sensitive PEGylated doxorubicin

Guanidine–Curcumin Complex-Loaded Amine-Functionalised Hollow Mesoporous Silica Nanoparticles for Breast Cancer Therapy

The current study focuses on developing a tumour-targeted functionalised nanocarrier that wraps hollow mesoporous silica nanoparticles. The guanidine carbonate and curcumin are immobilised on the surface of 3-aminopropyl-triethoxy silane (APTES)-decorated hollow mesoporous silica nanoparticles (HMSNP), as confirmed through XPS and NMR analysis. XPS analysis demonstrates that the shape of the hysteresis loops is modified and that pore volume and pore diameter are consequently decreased compared to control. Guanidine (85%) and guanidine–curcumin complex (90%) were successfully encapsulated in HMSNAP and showed a 90% effective and sustained release at pH 7.4 for up to 72 h. Acridine orange/ethidium bromide dual staining determined that GuC-HMNSAP induced more late apoptosis and necrosis at 48 and 72 h compared with Gu-HMNSAP-treated cells. Molecular investigation of guanidine-mediated apoptosis was analysed using western blotting. It was found that cleaved caspases, c-PARP, and GSK-3β (Ser9) had increased activity in MCF-7 cells. GuC-HMSNAP increased the activity of phosphorylation of oncogenic proteins such as Akt (Ser473), c-Raf (Ser249), PDK1 (Ser241), PTEN (Ser380), and GSK-3β (Ser9), thus inducing cell death in MCF-7 cells. Altogether, our findings confirm that GuC-HMNSAP induces cell death by precisely associating with tumour-suppressing proteins, which may lead to new therapeutic approaches for breast cancer therapy.

Synthesis and Coordination Properties of a Water-Soluble Material by Cross-Linking Low Molecular Weight Polyethyleneimine with Armed Cyclotriveratrilene

In this study, a full organic and water-soluble material was synthesized by coupling low molecular weight polyethylenimine (PEI-800) with cyclotriveratrilene (CTV). The water-soluble cross-linked polymer contains hydrophobic holes with a high coordination capability towards different organic drug molecules. The coordinating capability towards hydrophilic drugs (doxorubicin, gatifloxacin and sinomenine) and hydrophobic drugs (camptothecin and celastrol) was analyzed in an aqueous medium by using NMR, UV-Vis and emission spectroscopies. The coordination of drug molecules with the armed CTV unit through hydrophobic interactions was observed. In particular, celastrol exhibited more ionic interactions with the PEI moiety of the hosting system. In the case of doxorubicin, the host-guest detachment was induced by the addition of ammonium chloride, suggesting that the intracellular environment can facilitate the release of the drug molecules.

A targeted self-assembling photosensitizer nanofiber constructed by multicomponent coordination

Employing a peptide-based supramolecular photosensitizer nanofiber that combines the flexibility of a self-assembling short peptide and high spatiotemporal precision is a promising approach in photodynamic therapy (PDT). Herein, we developed a versatile multicomponent and multifunctional coordination self-assembling photosensitizer nanofiber based on the combination of a diphenylalanine (FF) short peptide, cell penetrating peptide 44 (CPP44) and 5-(4-aminophenyl)-10,15,20-triphenyl porphine (TPP-NH₂), resulting in CPP44-FF-TPP-NH₂ nanofibers (CFTNFs). Transmission electron microscopy observations showed the filamentous morphology of CFTNFs. Compared with free TPP-NH₂, CFTNFs exhibited a higher cell uptake ability in HepG2 cells and a better tumor targeting ability in in vivo experiments. Furthermore, CFTNFs induced apoptosis and necrosis of more HepG2 cells in vitro and showed higher tumor growth inhibitory activity in vivo. In summary, these results indicated that CFTNFs could lead to greatly enhanced photodynamic treatment efficacy. Moreover, our study provides new opportunities for the development of peptide-based multicomponent coordination self-assembling photosensitizer nanofibers to enhance tumor-specific delivery and the anticancer efficiency.

TMTP1-Modified, Tumor Microenvironment Responsive Nanoparticles Co-Deliver Cisplatin and Paclitaxel Prodrugs for Effective Cervical Cancer Therapy

Background and Purpose

Cisplatin-paclitaxel (TP) combination chemotherapy as the first-line therapy for numerous cancers is hindered by its inadequate accumulation in tumors and severe side effects resulting from non-specific distribution. The aim of this study is to explore whether TMTP1-modified, cisplatin and paclitaxel prodrugs co-loaded nanodrug could improve cervical cancer chemotherapy and relieve its side effects through active and passive tumor targeting accumulation and controlled drug release.

Methods

TDNP, with capacities of active targeting for tumors and controlled drug release, was prepared to co-deliver cisplatin and paclitaxel prodrugs. The characteristics were investigated, including the diameter, surface zeta potential, stability and tumor microenvironment (TME) dependent drug release profiles. Cellular uptake, cytotoxicity, drug accumulation in tumors, antitumor effects and safety analysis were evaluated in vitro and in vivo.

Results

The oxidized cisplatin and the paclitaxel linked to the polymer achieved a high loading effciency of over 80% and TME-dependent sustained drug release. Moreover, TMTP1 modification enhanced cellular uptake of TDNP and further improved the cytotoxicity of TDNP in vitro. In vivo, TDNP showed an extended blood circulation and increased accumulation in SiHa xenograft models with the aid of TMTP1. More importantly, TDNP controlled tumor growth without life-threatening side effects.

Conclusion

Our study provided a novel TP co-delivery platform for targeted chemotherapy of cervical cancer, which was promising to improve the therapeutic effcacy of TP and may also have application in other tumors.

Magnetically Navigated Protein Transduction In Vivo using Iron Oxide-Nanogel Chaperone Hybrid

Systems for "protein transduction," intracellular delivery of functional proteins, are needed to address deliverability challenges of protein therapeutics. However, in vivo protein transduction remains challenging because of instability in serum, extracellular protease digestion and rapid excretion from the bloodstream. Here, a magnetically guided in vivo protein transduction using magnetic nanogel chaperone (MC) composed of iron oxide nanoparticles and a polysaccharide nanogel, a protein carrier inspired by "catch and release" mechanisms of molecular chaperones is demonstrated. The MC system enables efficient delivery of anti-cancer proteins, saporin and RNaseA, into cultured tumor lines and inhibits cell proliferation, mainly via apoptosis. Magnetic in vivo protein transduction via intravenous whole body administration is demonstrated in a fibrosarcoma model. By in vivo optical imaging, MC accumulated in tumor tissues under magnetic field three times more than without irradiation. With subcutaneous injection, saporin is delivered by MC to the cytoplasm in magnetically targeted tissues. In an oral cancer model, MC-delivered magnetically targeted saporin decreased tumor volume without significant body weight changes and no regrowth of tumor at 3 months after complete regression. Protein transduction with MC shows promise for cancer therapeutics and, potentially, for regenerative medicine and other biomedical applications.

Human serum albumin-based doxorubicin prodrug nanoparticles with tumor pH-responsive aggregation-enhanced retention and reduced cardiotoxicity

Doxorubicin (DOX) is a widely-used anticancer drug, but its cardiotoxicity severely hampers its potency in chemotherapy. Herein, human serum albumin (HSA) is engaged as a biocompatible nanocarrier to load a pH-sensitive DOX prodrug, DMDOX, generating HSA-DMDOX nanoparticles via self-assembly driven by hydrophobic interactions. HSA-DMDOX disperses well in a physiological environment (∼40 nm) but aggregates in a tumor acidic microenvironment (pH 6.5, ∼140 nm) owing to the hydrophobicity increase of DMDOX by protonation of carboxylic groups. In vitro anticancer study showed that HSA-DMDOX exhibited enhanced cellular uptake by 4T1 cells and superior cytotoxicity in comparison to HSA-DOX nanoparticles. In vivo study suggested that HSA-DMDOX achieved long blood circulation, aggregation enhanced tumor retention, comparable antitumor efficacy and reduced cardiotoxicity relative to free DOX. Our work presents a facile and effective approach to delivering anthracyclines by HSA-based tumor pH-responsive nanoparticles with aggregation-enhanced tumor retention and reduced toxicity.

Morphologically homogeneous, pH-responsive gold nanoparticles for non-invasive imaging of HeLa cancer

Gold nanoparticles (AuNPs) have been widely used as nanocarriers in drug delivery to improve the efficiency of chemotherapy treatment and enhance early disease detection. The advantages of AuNPs include their excellent biocompatibility, easy modification and functionalization, facile synthesis, low toxicity, and controllable particle size. This study aimed to synthesize a conjugated citraconic anhydride link between morphologically homogeneous AuNPs and doxorubicin (DOX) (DOX-AuNP). The carrier was radiolabeled for tumor diagnosis using positron emission tomography (PET). The systemically designed DOX-AuNP was cleaved at the citraconic anhydride linker site under the mild acidic conditions of a cancer cell, thereby releasing DOX. Subsequently, the AuNPs aggregated via electrostatic attraction. HeLa cancer cells exhibited a high uptake of the radiolabeled DOX-AuNP. Moreover, PET tumor images were obtained using radiolabeled DOX-AuNP in cancer xenograft mouse models. Therefore, DOX-AuNP is expected to provide a valuable insight into the use of radioligands to detect tumors using PET.

Active-targeting and acid-sensitive pluronic prodrug micelles for efficiently overcoming MDR in breast cancer

Multidrug resistance (MDR) seriously hinders therapeutic efficacy in clinical cancer treatment. Herein, we reported new polymeric prodrug micelles with tumor-targeting and acid-sensitivity properties based on two different pluronic copolymers (F127 and P123) for enhancing tumor MDR reversal and chemotherapy efficiency in breast cancer. Hybrid micelles were composed of phenylboric acid (PBA)-modified F127 (active-targeting group) and doxorubicin (DOX)-grafted P123 (prodrug groups), which were named as FBP-CAD. FBP-CAD exhibited good stability in a neutral environment and accelerated drug release under mildly acidic conditions by the cleavage of β-carboxylic amides bonds. In vitro studies demonstrated that FBP-CAD significantly increased cellular uptake and drug concentration in MCF-7/ADR cells through the homing ability of PBA and the anti-MDR effect of P123. In vivo testing further indicated that hybrid micelles facilitated drug accumulation at tumor sites as well as reduced side effects to normal organs. The synergistic effect of active-targeting and MDR-reversal leads to the highest tumor growth inhibition (TGI 78.2%). Thus, these multifunctional micelles provide a feasible approach in nanomedicine for resistant-cancer treatment.

Smart Nanocarriers for Targeted Cancer Therapy

Cancer is considered one of the most threatening diseases worldwide. Although many therapeutic approaches have been developed and optimized for ameliorating patient's conditions and life expectancy, however, it frequently remains an incurable pathology. Notably, conventional treatments may reveal inefficient in the presence of metastasis development, multidrug resistance and inability to achieve targeted drug delivery. In the last decades, nanomedicine has gained a prominent role, due to many properties ascribable to nanomaterials. It is worth mentioning their small size, their ability to be loaded with small drugs and bioactive molecules and the possibility to be functionalized for tumor targeting. Natural vehicles have been exploited, such as exosomes, and designed, such as liposomes. Biomimetic nanomaterials have been engineered, by modification with biological membrane coating. Several nanoparticles have already entered clinical trials and some liposomal formulations have been approved for therapeutic applications. In this review, natural and synthetic nanocarriers functionalized for actively targeting cancer cells will be described, focusing on their advantages with respect to conventional treatments. Recent innovations related to biomimetic nanoparticles camouflaged with membranes isolated from different types of cells will be reported, together with their promising applications. Finally, a short overview on the latest advances in carrier-free nanomaterials will be provided.

Synergistic Cancer Photochemotherapy via Layered Double Hydroxide-Based Trimodal Nanomedicine at Very Low Therapeutic Doses

The success of cancer therapy is always accompanied by severe side effects due to the high amount of toxic antitumor drugs that off-target normal organs/tissues. Herein, we report the development of a trifunctional layered double hydroxide (LDH) nanosystem for combined photochemotherapy of skin cancer at very low therapeutic doses. This nanosystem (ICG/Cu-LDH@BSA-DOX) is composed of acid-responsive bovine serum albumin-doxorubicin prodrug (BSA-DOX) and indocyanine green (ICG)-intercalated Cu-doped LDH nanoparticle. ICG/Cu-LDH@BSA-DOX is able to release DOX in an acid-triggered manner, efficiently and simultaneously generates heating and reactive oxygen species (ROS) upon 808 nm laser irradiation, and synergistically induces apoptosis of skin cancer cells. In vivo therapeutic evaluations demonstrate that ICG/Cu-LDH@BSA-DOX nearly eradicated the tumor tissues upon one-course treatment using very low doses of therapeutic agents (0.175 mg/kg DOX, 0.5 mg/kg Cu, and 0.25 mg/kg ICG) upon very mild 808 nm laser irradiation (0.3 W/cm² for 2 min). This work thus provides a novel strategy to design anticancer nanomedicine for efficient combination cancer treatment with minimal side effects in clinical applications.

Advances of smart nano-drug delivery systems in osteosarcoma treatment

Nanotechnology has recently become popular due to its potential for biomedical applications, especially for cancer treatment. Nanotechnology, featuring responsiveness to stimuli and stable drug release, has been widely used for the delivery of chemotherapeutic drugs, which are commonly used in the treatment of osteosarcoma. Smart stimuli-responsive nanotechnology is expected to improve the treatment of osteosarcoma. Herein, we focus on the latest research on nanomaterials in treating osteosarcoma that respond to internal and external stimuli. We also discuss nanocarriers with targeting ligands and the use of smart nanotechnology to partially reverse the multidrug resistance of osteosarcoma.

Advances and perspectives in carrier-free nanodrugs for cancer chemo-monotherapy and combination therapy

Nanocarrier-based drug delivery systems hold impressive promise for biomedical application because of their excellent water dispersibility, prolonged blood circulation time, increased drug accumulation in tumors, and potential in combination therapeutics. However, most nanocarriers suffer from low drug-loading efficiency, poor therapeutic effectiveness, potential systematic toxicity, and unstable metabolism. As an alternative, carrier-free nanodrugs, completely formulated with one or more drugs, have attracted increasing attention in cancer therapy due to their advantage of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug-loading. In recent years, carrier-free nanodrugs have contributed to progress in a variety of therapeutic modalities. In this review, different common strategies for carrier-free nanodrugs preparation are first summarized, mainly including nanoprecipitation, template-assisted nanoprecipitation, thin-film hydration, spray-drying technique, supercritical fluid (SCF) technique, and wet media milling. Then we describe the recently reported carrier-free nanodrugs for cancer chemo-monotherapy or combination therapy. The advantages of anti-cancer drugs combined with other chemotherapeutic, photosensitizers, photothermal, immunotherapeutic or gene drugs have been demonstrated. Finally, a future perspective is introduced to highlight the existing challenges and possible solutions toward clinical application of currently developed carrier-free nanodrugs, which may be instructive to the design of effective carrier-free regimens in the future.

Functionalization of Polyethyleneimine with Hollow Cyclotriveratrylene and Its Subsequent Supramolecular Interaction with Doxorubicin

In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host-guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform.

pH-Responsive Fluorescence Enhanced Nanogel for Targeted Delivery of AUR and CDDP Against Breast Cancer

Introduction

Auraptene (AUR), a natural bioactive prenyloxy coumarin, is a highly pleiotropic molecule that can bind to the MT1 receptor and can effectively reduce the proliferation and migration of breast cancer cells. Cisplatin (CDDP), as the first synthetic platinum-based anticancer drug, is widely used in the clinic due to its definite mechanism and therapeutic effect on diverse tumors. However, both of AUR and CDDP exhibit some disadvantages when used alone, including poor solubility, low bioavailability, lack of selectivity and systemic toxicity when they are used singly.

Methods

Therefore, the biodegradable materials hyaluronic acid (HA) and β-cyclodextrin derivative (mono-(6-amino-mono-6-deoxy)-β-CD, CD) were employed as carriers to load AUR and CDDP to form nanogel (^CDDPHA-CD@AUR) capable of dual-targeted delivery and synergistic therapy for breast cancer and cell imaging.

Results

With the help of the CDDP-crosslinked CD-loaded structure, the newly synthesized nanogel exhibited excellent physiological stability and fluorescence effects. The release of AUR and CDDP was affected by the pH value, which was beneficial to the selective release in the tumor microenvironment. Cell experiments in vitro demonstrated that the nanogel could be selectively internalized by MCF-7 cells and exhibited low cytotoxicity to HK-2 cells. Antitumor experiments in vivo showed that the nanogel have better antitumor effects and lower systemic toxicity.

Conclusion

Based on these, the nanogel loaded with AUR and CDDP have the potential for targeted delivery against breast cancer.

Remote loading paclitaxel-doxorubicin prodrug into liposomes for cancer combination therapy

The combination of paclitaxel (PTX) and doxorubicin (DOX) has been widely used in the clinic. However, it remains unsatisfied due to the generation of severe toxicity. Previously, we have successfully synthesized a prodrug PTX-S-DOX (PSD). The prodrug displayed comparable in vitro cytotoxicity compared with the mixture of free PTX and DOX. Thus, we speculated that it could be promising to improve the anti-cancer effect and reduce adverse effects by improving the pharmacokinetics behavior of PSD and enhancing tumor accumulation. Due to the fact that copper ions (Cu²⁺) could coordinate with the anthracene nucleus of DOX, we speculate that the prodrug PSD could be actively loaded into liposomes by Cu²⁺ gradient. Hence, we designed a remote loading liposomal formulation of PSD (PSD LPs) for combination chemotherapy. The prepared PSD LPs displayed extended blood circulation, improved tumor accumulation, and more significant anti-tumor efficacy compared with PSD NPs. Furthermore, PSD LPs exhibited reduced cardiotoxicity and kidney damage compared with the physical mixture of Taxol and Doxil, indicating better safety. Therefore, this novel nano-platform provides a strategy to deliver doxorubicin with other poorly soluble antineoplastic drugs for combination therapy with high efficacy and low toxicity.

TME-Responsive Polyprodrug Micelles for Multistage Delivery of Doxorubicin with Improved Cancer Therapeutic Efficacy in Rodents

It is of great significance to develop multifunctional biomaterials to effectively deliver anticancer drug to tumor cells for cancer therapy. Here, inspired by the specific tumor microenvironment (TME) cues, a unique multistage pH/redox-responsive polyprodrug composed of amphiphilic pH-sensitive diblock copolymer poly(ethylene glycol) methyl ether-b-poly(β-amino esters) conjugated with doxorubicin (DOX) via redox-sensitive disulfide bonds (mPEG-b-PAE-ss-DOX) is designed and developed. This polyprodrug can self-assemble into micelles (DOX-ss@PMs) at low concentration with high serum stability, indicating that DOX-ss@PMs have prolonged circulation time. The dual pH/redox-responsiveness of the multistage platform is thoroughly evaluated. In vitro results demonstrate that DOX-ss@PMs can highly accumulate at tumor site, followed by responding to the acidity for disassembly and effectively penetrating into the tumor cells. DOX is released from the platform due to the cleavage of disulfide bonds induced by high glutathione (GSH) concentration, thereby inducing the apoptosis of tumor cells. In vivo studies further reveal that multistage DOX-ss@PMs can more efficiently inhibit the growth of tumors and improve the survival of tumor-bearing mice in comparison to the free drug and control. These results imply that multistage delivery system might be a potential and effective strategy for drug delivery and DOX-ss@PMs could be a promising nanomedicine for cancer chemotherapy.

Acid-labile anhydride-linked doxorubicin-doxorubicin dimer nanoparticles as drug self-delivery system with minimized premature drug leakage and enhanced anti-tumor efficacy

Acid-labile anhydride-linked doxorubicin-doxorubicin dimers (D-DOX) were designed as doxorubicin-doxorubicin conjugate-based drug self-delivery systems (DSDSs) with high drug content for tumor intracellular pH-triggered release, by conjugating doxorubicin (DOX) with various anhydrides, such as maleic anhydride (MAH), succinic anhydride (suc), and 2,3-dimethylmaleic anhydride (DMMAH). With the similar diameter of about 200 nm, the D-DOXMAH showed better pH-triggered DOX release and was thus selected for the further investigation. The D-DOX-5 nanoparticles with desirable average hydrodynamic diameter (Dh) of 162 nm and high drug content of 51.20% were obtained via self-assembly by a facile dialysis technique, with the PEGylated dimer (D-DOXMAH-S-PEG) as surfactant. The cumulative DOX release from the proposed D-DOX nanoparticles reached 40.6% within 36 h in the simulated tumor intracellular acidic micro-environment, while the premature drug leakage was only 4.5% in the simulated normal physiological medium. The MTT results indicated the proposed DSDS possessed an enhanced anti-tumor efficacy for the HepG2 cancer cell than the free DOX.

Bacterial Template Synthesis of Multifunctional Nanospindles for Glutathione Detection and Enhanced Cancer-Specific Chemo-Chemodynamic Therapy

Biological synthetic methods of nanoparticles have shown great advantages, such as environmental friendliness, low cost, mild reaction conditions, and enhanced biocompatibility and stability of products. Bacteria, as one of the most important living organisms, have been utilized as bioreducing nanofactories to biosynthesize many metal nanoparticles or compounds. Here, inspired by the disinfection process of KMnO₄, we for the first time introduce bacteria as both the template and the reducing agent to construct a novel tumor microenvironment-responsive MnO_x-based nanoplatform for biomedical applications in various aspects. It is found that the bacterium/MnO_x-based nanospindles (EM NSs) can efficiently encapsulate the chemotherapeutic agent doxorubicin (DOX), leading to the fluorescence quenching of the drug. The as-formed DOX-loaded EM NSs (EMD NSs) are proven to be decomposed by glutathione (GSH) and can simultaneously release DOX and Mn²⁺ ions. The former can be utilized for sensitive fluorescence-based GSH sensing with a limit of detection as low as 0.28 μM and selective cancer therapy, while the latter plays important roles in GSH-activated magnetic resonance imaging and chemodynamic therapy. We also demonstrate that these nanospindles can generate oxygen in the presence of endogenous hydrogen peroxide to inhibit P-glycoprotein expression under hypoxia and can achieve excellent tumor eradication and tumor metastasis inhibition performance. Taken together, this work designs a multifunctional bacterially synthesized nanomissile for imaging-guided tumor-specific chemo-chemodynamic combination therapy and will have implications for the design of microorganism-derived smart nanomedicines.

Novel pH-triggered biocompatible polymeric micelles based on heparin-α-tocopherol conjugate for intracellular delivery of docetaxel in breast cancer

In this study, pH-triggered polymeric micelle comprising α-tocopherol (TOC) and heparin (HEP) was developed and loaded with docetaxel (DTX). The amphiphilic copolymer was synthesized by grafting TOC onto HEP backbone by a pH-cleavable bond. DTX-loaded micelles were characterized in terms of critical micelle concentration (CMC), particle size, zeta potential, entrapment efficiency (EE), pH-responsive behavior, and drug release. In vitro cytotoxicity of the micelles against breast cancer cells was investigated by MTT assay. The cellular uptake of coumarin-loaded micelles was also evaluated. Furthermore, the pharmacokinetics of DTX-loaded micelles was evaluated and compared with that of Taxotere^®.HEP-CA-TOC copolymers showed low CMC values and high EE. At pH 7.4, the micelles remained stable in size and shape, whereas considerable changes in particle size and morphology were observed at pH 5.5. DTX-loaded micelles showed pH-dependent drug release profiles. Coumarin-loaded micelles showed higher cellular uptake than free coumarin. Therefore, the DTX-loaded micelles showed more toxicity against breast cancer cells than free DTX. A significant increase in T_1/2 β, AUC_0-∞ and MRT was observed in DTX-loaded micelle treated group as compared to the group treated with Taxotere^®.The results suggest that the pH-sensitive HEP-modified micelles could be promising for enhanced intracellular drug delivery of DTX for cancer treatment.

Synergistic Effect of Retinoic Acid Polymeric Micelles and Prodrug for the Pharmacodynamic Evaluation of Tumor Suppression

All-trans retinoic acid (ATRA) is an effective agent that induces differentiation, inhibits cell proliferation, and acts as an anticancer agent. ATRA was successfully conjugated with Pluronic F127 via esterification to enhance its anticancer effects. Pluronic-ATRA showed high cytotoxicity and inhibitory concentrations (IC₅₀) 50% lower than those of ATRA in various breast cancer cell lines (4T1:31.16–8.57 μg/mL; EMT6: 50.48–7.08 μg/mL; MDA-MB-231:37.58–8.99 μg/mL; BT474:25.27–9.09 μg/mL). In combination with chemotherapy, Pluronic-ATRA synergistically enhanced the cytotoxic effects of cisplatin (CDDP). Pluronic-ATRA combined with CDDP effectively suppressed breast tumor growth in vivo. The results of this study demonstrate the potential of Pluronic-ATRA as an anticancer agent that can be used in combination therapy against solid tumors.

Nanoplatform Constructed from a β-Glucan and Polydeoxyadenylic Acid for Cancer Chemotherapy and Imaging

A nanoplatform carrying doxorubicin (Dox) for cancer therapy and a dye for imaging was developed based on a natural triple helix β-glucan (t-LNT) and polydeoxyadenylic acid (poly(dA)). The t-LNT-Dox conjugates were prepared through Schiff-base reaction between the aldehyde group in the oxidized t-LNT and the amino group of Dox, the single chains (s-LNT-Dox) of which interacted with the poly(dA)-dye to form a composite s-LNT-Dox/poly(dA)-dye through hydrogen bonding between s-LNT and poly(dA). t-LNT-Dox was confirmed to acid-responsively release Dox in vitro, showing enhanced cytotoxicity against HeLa cancer cells with time. It was confirmed that Dox and the dye could be simultaneously delivered into HeLa cells or the tumors with a prolonged duration time. Furthermore, LNT-Dox conjugates effectively inhibited tumor growth and decreased adverse effects of the free Dox in vivo. Hence, this work develops a new strategy to fabricate the nanoplatform for therapy and imaging using a natural polysaccharide.

Preparation and evaluation of highly biocompatible nanogels with pH-sensitive charge-convertible capability based on doxorubicin prodrug

In this paper, to achieve the targeted ability of anti-tumor drug doxorubicin (DOX), enhance the treatment effect and reduce the side effect, a novel pH-sensitive and charge-convertible prodrug nanogel was prepared. Firstly, cis-aconitic anhydride-doxorubicin prodrug (CAD) and Pluronic F127-chitosan-CAD (F127-CS-CAD) conjugates were synthesized. Then the DOX loaded polyion complex micelles (F127-CS-CAD/CAD) were prepared by self-assembling, thus CAD was incorporated into micelles via electrostatic interactions between electronegative CAD and positively charged F127-CS-CAD and hydrophobic interactions. Finally a pH-responsive charge-convertible copolymer, folic acid modified gelatin (Gel-FA) was shielded on the surface of micelles and the Gel-FA/F127-CS-CAD/CAD nanogel was formed, the charge-convertible capability was evaluated through changes of the morphology and Zeta potential under different pH value environment by transmission electron microscopy (TEM) and Zeta potential analyzer. And in vitro pH-dependent and two-phase drug release from nanogel was also evaluated. In vitro anti-tumor activity of Gel-FA/F127-CS-CAD/CAD nanogel was performed on HeLa cells and HepG2 cells to prove the strong cell toxicity of nanogels. Finally, the in vivo safety experiments showed that the nanogel achieved the reducing the toxic side effects of DOX significantly.

Multifunctional Cargo-Free Nanomedicine for Cancer Therapy

Nanocarriers encapsulating multiple chemotherapeutics are a promising strategy to achieve combinational chemotherapy for cancer therapy; however, they generally use exotic new carriers without therapeutic effect, which usually suffer from carrier-related toxicity issues, as well as having to pass extensive clinical trials to be drug excipients before any clinical applications. Cargo-free nanomedicines, which are fabricated by drugs themselves without new excipients and possess nanoscale characteristics to realize favorable pharmacokinetics and intracellular delivery, have been rapidly developed and drawn much attention to cancer treatment. Herein, we discuss recent advances of cargo-free nanomedicines for cancer treatment. After a brief introduction to the major types of carrier-free nanomedicine, some representative applications of these cargo-free nanomedicines are discussed, including combination therapy, immunotherapy, as well as self-monitoring of drug release. More importantly, this review draws a brief conclusion and discusses the future challenges of cargo-free nanomedicines from our perspective.

Tumor microenvironment-labile polymer-doxorubicin conjugate thermogel combined with docetaxel for in situ synergistic chemotherapy of hepatoma

Topical chemotherapy with complementary drugs is one of the most promising strategies to achieve an effective antitumor activity. Herein, a synergistic strategy for hepatoma therapy by the combination of tumor microenvironment-sensitive polymer-doxorubicin (DOX) conjugate thermogel, containing a DNA intercalator DOX, and docetaxel (DTX), a microtubule-interfering agent, was proposed. First, cis-aconitic anhydride-functionalized DOX (CAD) and succinic anhydride-modified DOX (SAD) were conjugated onto the terminal hydroxyl groups of poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA-PEG-PLGA), yielding the acid-sensitive CAD-PLGA-PEG-PLGA-CAD and the insensitive SAD-PLGA-PEG-PLGA-SAD conjugates, respectively. The prodrug aqueous solution exhibited a thermoreversible sol-gel transition between room and physiological temperature. Meantime, appropriate mechanical property, biodegradability, as well as a sustained release profile were revealed in such prodrug thermogels. More importantly, the addition of DTX to the DOX-conjugated thermogels (i.e., Gel-CAD and Gel-SAD) was verified with enhanced curative effect against tumor, where the antitumor efficacy of Gel-CAD+DTX was obviously higher than the other groups. A reliable security in vivo was also showed in the Gel-CAD+DTX group. Taken together, such combination of tumor microenvironment-labile prodrug thermogel and a complementary drug exhibited fascinating prospect for local synergistic antineoplastic therapy.

STATEMENT OF SIGNIFICANCE

Multidrug chemotherapy with synergistic effect has been proposed recently for hepatoma treatment in the clinic. However, the quick release, fast elimination, and unselectivity of multidrugs in vivo always limit their further application. To solve this problem, a synergistic combination of tumor microenvironment-sensitive polymeric doxorubicin (DOX) prodrug thermogel for DNA intercalation and a microtubule-interfering agent docetaxel (DTX) is developed in the present study for the local chemotherapy of hepatoma. Interestingly, a pH-triggered sustained release behavior, an enhanced antitumor efficacy, and a favorable security in vivo are observed in the combined dual-drug delivery platform. Therefore, effectively combining tumor microenvironment-labile polymeric prodrug thermogel with a complementary drug provides an advanced system and a promising prospect for local synergistic hepatoma chemotherapy.

Unified D-α-Tocopherol 5-Fu/SAHA bioconjugates self-assemble as complex nanodrug for optimized combination therapy

Aim: To optimize the synergistic efficacy of combination therapy with controlled molar ratio, complex small molecule-based nanodrug (Co-SMND) of 5-fluorouracil (5-Fu)/vorinostat (SAHA) was developed. Materials & methods: Co-SMND with various ratios of 5-Fu-D-α-tocopherol (VE)/SAHA-VE were prepared and characterized including co-assembly mechanism, hydrolytic stability, cytotoxicity, synergistic effect and apoptosis inducing ability. The antitumor activity, systematic toxicity and biodistribution of optimized Co-SMND were evaluated in CT-26 bearing BALB/c mouse. Results: Maximal synergistic effect of Co-SMND could be obtained via simply adjusting the feeding molar ratio. The optimized Co-SMND showed superior in vivo antitumor efficacy, upregulated security and selective intratumoral accumulation. Conclusion: Such Co-SMND is of great significance for future clinical translation, and would be an efficient platform for combination chemotherapy.

Self-Stabilized Hyaluronate Nanogel for Intracellular Codelivery of Doxorubicin and Cisplatin to Osteosarcoma

Osteosarcoma is one of the most serious bone malignancies with rapid speed of deterioration and low survival rate in children and teenagers. Chemotherapy is an important treatment for osteosarcoma, while the conventional small-molecule therapeutics exhibit low efficacies and severe side effects in the clinic. Drug-delivery platforms based on nanotechnology, particularly for self-stabilized delivery platforms with prolonged blood circulation, enhanced intratumoral accumulation, improved antitumor efficacy, and diminished side effects, may break the deadlock on osteosarcoma chemotherapy. Here, a cisplatin (CDDP)-crosslinked hyaluronic acid (HA) nanogel (CDDPHANG) is prepared for effective delivery of doxorubicin (DOX) to treat osteosarcoma. Importantly, both DOX and CDDP have led clinically used antitumor drugs, and CDDP acts as a crosslinker and ancillary anticarcinogen to prevent the premature release of DOX and to achieve synergistic therapeutic performance. Because of the enhanced stability of the nanogel, this CDDP-crosslinked DOX-loaded nanomedicine (CDDPHANG/DOX) exhibits an obviously prolonged circulation time compared to free drugs. Moreover, after valid tumor accumulation, DOX and CDDP are synergistically delivered into the tumor cells and synchronously released into the intracellular acidic environment. Based on the synergistic apoptosis-inducing effects of DOX and CDDP, CDDPHANG/DOX reveals an evidently enhanced antitumor efficacy compared to free drugs and their combination, indicating its great prospects for the chemotherapy of osteosarcoma.

One-Step Synthesis of Targeted Acid-Labile Polysaccharide Prodrug for Efficiently Intracellular Drug Delivery

The therapeutic potential of the active targeting and acid-sensitive polysaccharide prodrug was investigated. The active targeting of polysaccharide prodrug was based on the specific interaction between cyclo(Arg-Gly-Asp-d-Phe-Lys) peptide (c(RGDfK)) and its receptor α_vβ₃ integrin overexpressed on the membrane of tumor cells. The cRGD-modified doxorubicin-conjugated hydroxyethyl starch (HES=DOX/cRGD) was synthesized via a one-step Schiff base reaction between oxidized HES, and DOX and c(RGDfK) that achieved an acid-accelerated drug release profile. The targeted polysaccharide prodrug self-assembled into micelle in aqueous environment with a moderate hydrodynamic diameter of 77.1 nm. All data in vitro indicated enhanced cell uptake and elevated cytotoxicity of HES=DOX/cRGD toward human malignant melanoma A375 cells compared with HES=DOX and DOX. Moreover, the smart prodrug also exhibited upregulated accumulation in the tumor, improved antitumor efficacy, and reduced systemic cytotoxicity in vivo. The cRGD-decorated acid-sensitive polysaccharide prodrug was advantageous in both antitumor efficacy and systemic security, showing great prospect in clinical application.

Self-assembled nanomaterials for synergistic antitumour therapy

Recent progress on self-assembled nanodrugs for anticancer treatment was discussed.

One-pot synthesis of glutathione-responsive amphiphilic drug self-delivery micelles of doxorubicin–disulfide–methoxy polyethylene glycol for tumor therapy

We present a novel glutathione-responsive amphiphilic drug self-delivery (DSD) micelle with one-pot synthesis to synergistically address the problems of controlled drug release, degradability, drug tracing and in vivo accumulated toxicity.

Spatiotemporal Control of Doxorubicin Delivery from "Stealth-Like" Prodrug Micelles

In the treatment of cancer, targeting of anticancer drugs to the tumor microenvironment is highly desirable. Not only does this imply accurate tumor targeting but also minimal drug release en route to the tumor and maximal drug release once there. Here we describe high-loading, "stealth-like" doxorubicin micelles as a pro-drug delivery system, which upon light activation, leads to burst-like doxorbicin release. Through this approach, we show precise spatiotemporal control of doxorubicin delivery to cells in vitro.

Enhancing Doxorubicin Delivery toward Tumor by Hydroxyethyl Starch-g-Polylactide Partner Nanocarriers

Doxorubicin (DOX), a kind of wide-spectrum chemotherapeutic drug, can cause severe side effects in clinical use. To enhance its antitumor efficacy while reducing the side effects, two kinds of nanoparticles with desirable compositions and properties were assembled using optimally synthesized hydroxyethyl starch-grafted-polylactide (HES-g-PLA) copolymers and utilized as partner nanocarriers. The large empty HES-g-PLA nanoparticles (mean size, ca. 700 nm), at an optimized dose of 400 mg/kg, were used to block up the reticuloendothelial system in tumor-bearing mice 1.5 h in advance, and the small DOX-loaded HES-g-PLA nanoparticles (mean size, ca. 130 nm) were subsequently applied to the mice. When these partner nanocarriers were administered in this sequential mode, the released DOX had a significantly prolonged plasma half-life time and much slower clearance rate as well as a largely enhanced intratumoral accumulation as compared to free DOX. In vivo antitumor studies demonstrated that the DOX-loaded HES-g-PLA nanoparticles working together with their partner exhibited remarkably enhanced antitumor efficacy in comparison to free DOX. In addition, these HES-g-PLA partner nanocarriers showed negligible damage to the normal organs of the treated mice. Considering safe and efficient antitumor performance of DOX-loaded HES-g-PLA nanoparticles, the newly developed partner nanocarriers in combination with their administration mode have promising potential in clinical cancer chemotherapy.