High Drug Loading Content Research Articles

Peptide-Based Hydrogels and Nanogels for Delivery of Doxorubicin.

IntroductionThe clinical use of the antitumoral drug doxorubicin (Dox) is reduced by its dose-limiting toxicity, related to cardiotoxic side effects and myelosuppression. In order to overcome these drawbacks, here we describe the synthesis, the structural characterization and the in vitro cytotoxicity assays of hydrogels (HGs) and nanogels (NGs) based on short peptide sequences loaded with Dox or with its liposomal formulation, Doxil.MethodsFmoc-FF alone or in combination with (FY)3 or PEG8-(FY)3 peptides, at two different ratios (1/1 and 2/1 v/v), were used for HGs and NGs formulations. HGs were prepared according to the “solvent-switch” method, whereas NGs were obtained through HG submicronition by the top-down methodology in presence of TWEEN®60 and SPAN®60 as stabilizing agents. HGs gelation kinetics were assessed by Circular Dichroism (CD). Stability and size of NGs were studied using Dynamic Light Scattering (DLS) measurements. Cell viability of empty and filled Dox HGs and NGs was evaluated on MDA-MB-231 breast cancer cells. Moreover, cell internalization of the drug was evaluated using immunofluorescence assays.ResultsDox filled hydrogels exhibit a high drug loading content (DLC=0.440), without syneresis after 10 days. Gelation kinetics (20–40 min) and the drug release (16–28%) over time of HGs were found dependent on relative peptide composition. Dox filled NGs exhibit a DLC of 0.137 and a low drug release (20–40%) after 72 h. Empty HGs and NGs show a high cell viability (>95%), whereas Dox loaded ones significantly reduce cell viability after 24 h (49–57%) and 72 h (7–25%) of incubation, respectively. Immunofluorescence assays evidenced a different cell localization for Dox delivered through HGs and NGs with respect to the free drug.DiscussionA modulation of the Dox release can be obtained by changing the ratios of the peptide components. The different cellular localization of the drug loaded into HGs and NGs suggests an alternative internalization mechanism. The high DLC, the low drug release and preliminary in vitro results suggest a potential employment of peptide-based HGs and NGs as drug delivery tools.

Lactobionic acid-modified thymine-chitosan nanoparticles as potential carriers for methotrexate delivery

In order to achieve efficient delivery of methotrexate (MTX), thymine-chitosan nanoparticles (Thy-Cs NPs) were prepared, and further decorated with lactobionic acid (LA) to obtain tumor-targeting nanoparticles (LA-Thy-Cs NPs). These nanoparticles possessed a regular spherical structure with the average size about 190–250 nm and narrow size distribution, which were kinetically stable in the physiological environment. Due to electrostatic interactions and multiple hydrogen-bonding interactions between MTX and carriers, MTX was loaded into Thy-Cs NPs with high drug loading content (~20%). MTX release from Thy-Cs NPs was significantly accelerated in the mildly acidic environment due to the destruction of two types of non-covalent interactions. In vitro cell experiments demonstrated that LA-Thy-Cs NPs could be efficiently internalized into hepatoma carcinoma cells, leading to higher cytotoxicity. Moreover, MTX-loaded LA-Thy-Cs NPs performed an enhanced growth inhibition in three-dimensional multicellular tumor spheroids. Thus, the LA decorated thymine-chitosan nanocarriers can be a promising candidate for efficient delivery of MTX.

An injectable hydrogel using an immunomodulating gelator for amplified tumor immunotherapy by blocking the arginase pathway

Arginase 1 (ARG1) inactivates T cells by degrading L-arginine, severely reducing the immunotherapeutic efficacy. Effectively blocking the ARG1 pathway remains a challenge. L-norvaline is a very cheap and negligible side effects inhibitor of ARG1. However, its blockage efficacy for ARG1 is impeded by its high half-maximal-inhibitory concentration (IC50) requiring high drug loading content of L-norvaline in carriers. Moreover its high water solubility results in bursting and uncontrolled release. Herein we reported an injectable hydrogel strategy via an L-norvaline-based immunomodulating gelator that could effectively block ARG1 pathway. The designed gelator was a diblock copolymer containing L-norvaline-based polypeptide block, which could construct a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The hydrogel not only ensures high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bond cleavage, thereby solving the problems encountered by L-norvaline. The injectable hydrogel in combination with doxorubicin hydrochloride demonstrated a potent immunotherapy for removal of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis by combining the blockage of ARG1 pathway and the immunogenic cell death. Our immunomodulating gelator strategy provides a robust injectable hydrogel platform to efficiently reverse ARG1 immunosuppressive environments for amplified immunotherapy. Statement of SignificanceWe designed an injectable hydrogel via an L-norvaline-based immunomodulating gelator. The designed gelator, a diblock copolymer containing an L-norvaline-based polypeptide block, enabled a thermally responsive injectable hydrogel by its self-gelation in tumor microenvironments. The injectable hydrogel not only guarantees high drug loading of L-norvaline, but also ensures controlled release of L-norvaline through responsive peptide bonds cleavage, thereby solving the problems encountered by L-norvaline. By further introducing doxorubicin hydrochloride in the hydrogel for inducing immunogenic cell death, the hydrogel showed remarkable immunotherapeutic efficacy towards ablation of primary tumors, suppression of abscopal tumors and inhibition of pulmonary metastasis. Our immunomodulating gelator strategy provides a new concept to efficiently reverse Arginase 1 immunosuppressive environments for amplified immunotherapy.

A two-fold interpenetration pillar-layered metal-organic frameworks based on BODIPY for chemo-photodynamic therapy

The combination of chemotherapy and photodynamic therapy has been proved to be a promising therapy for drug-resistant cancers. In this study, we report, for the first time, a novel two-fold interpenetration pillar-layered metal-organic frameworks (MOFs) material, using BODIPY-derivate bipyridine as linker and Photosensitizer (PS), named BBP-MOFs, was successfully synthesized to serve as a drug carrier and Photodynamic agent simultaneously. The BBP-MOFs could generate singlet oxygen (1O2) to perform PDT under 660 nm light irradiation, in the meantime, the anticancer drugs doxorubicin (DOX) could be loaded for chemotherapy. The results showed that BBP-MOFs exhibited a high drug loading content of 49.7% a controlled drug release and ideal biocompatibility. This DOX loaded BBP-MOFs was readily taken up by HeLa cells, and high levels of 1O2 were generated under light irradiation. This work provided strong evidence for BBP-MOFs as a promising new anticancer drug carrier and PDT candidate, the PDT and chemotherapy combined synergistic therapy revealed high therapeutic efficacy for cancer cells.

Tailor-Made Cell-Based Biomimetic Nanoprobes for Fluorescence Imaging Guided Colorectal Cancer Chemo-immunotherapy.

Colorectal cancer has become one of the malignant tumors with a high rate of morbidity and mortality. Therefore, how to effectively treat colorectal cancer is crucial. Although nanodelivery system has been applied to the therapy of colorectal cancer, the majority of existing nanodelivery systems still have drawbacks such as low biocompatibility and poor targeting ability. In this work, tailor-made cell-based biomimetic nanoplatform was prepared to enhance the targeting and therapeutic effect for colorectal cancer chemo-immunotherapy. First, hollow long persistence luminescence nanomaterials were synthesized with superior background-free bioimaging effect and high drug-loading content. After loaded with cisplatin, the nanoplatform was camouflaged with tailor-made erythrocyte and programmed cell death receptor 1 (PD-1) expressed hybrid cell membrane. In vivo animal imaging experiment showed that the nanoplatform camouflaged with hybrid cell membrane not only had excellent immune escapability but also had excellent tumor active targeting ability. In vivo anticancer experiments showed that combined chemotherapy and immunotherapy of the nanoplatform could significantly inhibit tumor growth in tumor-bearing mice. In summary, the tailor-made cell-based membrane camouflage produced excellent immune escapability and cancer active targeting ability, providing a modality for biomimetic nanodelivery systems.

Phenylboronic acid-conjugated chitosan nanoparticles for high loading and efficient delivery of curcumin

In order to achieve high loading and efficient delivery of curcumin, phenylboronic acid-conjugated chitosan nanoparticles were prepared by a simple desolvation method. These nanoparticles exhibited a regular spherical shape with the average size about 200−230 nm and narrow size distribution, which were kinetically stable under physiological condition. Due to boronate ester formation between curcumin and phenylboronic acid groups in the nanoparticles, and the hydrogen bonding interactions between curcumin and nanocarriers, curcumin was successfully loaded into the nanoparticles with high drug loading content. These curcumin-loaded nanoparticles showed pH and reactive oxygen species (ROS)-triggered drug release behavior. In vitro cell experiments revealed that the blank nanoparticles were completely nontoxic to cultured cells, and the curcumin-loaded nanoparticles exhibited efficient antitumor efficiency against cancer cells. Moreover, the drug-loaded nanoparticles performed an enhanced growth inhibition in three-dimensional multicellular tumor spheroids. Thus, these nanocarriers would be a promising candidate for curcumin delivery in tumor treatment.

Facile Preparation of Tilmicosin-Loaded Polymeric Nanoparticle with Controlled Properties and Functions.

As one of the effective broad-spectrum antimicrobial and anti-inflammatory drugs, tilmicosin (TIM) is applied extensively in a wide range of veterinary treatments. However, the low bioavailability typically leads to overuse of TIM in practical applications, which can cause residual accumulation in the environment and contamination of foodstuffs. Here, we report a precipitation method that allows us to prepare TIM-loaded poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) nanoparticles. Specifically, TIM and biocompatible P(MMA-co-MAA) are dissolved in methanol and then water is introduced as an antisolvent, which triggers the co-precipitation and leads to well-controlled nanoparticles. Depending on the drug/polymer mass ratio and the total concentration of drug and polymer, the formed nanoparticles display a tunable radius from 27 to 80 nm with a narrow size distribution, a high drug loading content, and a controlled release of TIM. The encapsulation does not interrupt the antibacterial function of TIM while reducing its cytotoxicity enormously. Moreover, the formed nanoparticles could be dried to powder through freeze-drying, and the redispersion of the particles hardly disturbs the particle size, size distribution, and drug loading content. Our study developed a facile and robust precipitation method for the controlled construction of TIM-loaded polymeric nanoparticles with tunable properties and functions, as well as improved biocompatibility, which shall improve the bioavailability of TIM and enhance the practical applications.

Drug-induced hierarchical self-assembly of poly(amino acid) for efficient intracellular drug delivery

As a potent anticancer drug, gambogic acid (GA) suffers from its poor water solubility and low chemical stability and shows a limited clinical outcome. To address this problem, we report here a simple and effective strategy to immobilize and deliver GA using a reducible diblock poly(amino acid) as a model. The electrostatic interaction between GA and polymer enables a high drug loading content up to 53.6 %. Moreover, the drug complexation induces a micelle-to-vesicle transformation, combined with a conformation transition from random coil to α-helix. The hierarchically assembled drug nanocomplexes can serve as a smart carrier for efficient cell internalization and triggered release of multiple drugs under intracellular acidic and reductive conditions, resulting in a synergistic antitumor efficacy in vitro. This work provides a new insight into the drug-carrier interaction and a facile nanoplatform for drug delivery applications.

Design and fabrication of cell-targeted, dual drug-loaded nanoparticles with pH-controlled drug release and near-infrared light-induced photothermal effects

Multi-functional nanoparticles with targeting and chemo-photothermal features are attractive materials for the development of therapeutics. In this study, thermal- and pH-sensitive nanoparticles loaded with two drugs were fabricated for controlled drug release. For synthesis of nanoparticles, we first prepared a PAMAM dendrimer cluster, which could provide large core space, and then sequentially loaded indocyanine green (ICG, a photothermal agent) and doxorubicin (DOX, a chemotherapeutic agent) premixed with polyacrylic acid (PAA) to the dendrimer cluster through ionic interactions. This self-assembling strategy yielded a high drug-loading content for both DOX (19.1 ± 0.4%) and ICG (54 ± 1%). Subsequently, PEG and Herceptin were covalently attached to nanoparticles to promote their bio-recognition by HER2-overexpressing cancer cells. DOX was released by changing pH from 7.4 to 5; DOX release was markedly enhanced by NIR (808 nm) laser irradiation. Conjugation with Herceptin could enhance specific attachment and accumulation of nanoparticles in tumor cells. Under NIR laser irradiation, ICG served as a remote-controlled trigger to generate considerable heat that caused severe physical damage and extensive cell apoptosis. Furthermore, after NIR laser irradiation, drug delivery and penetration of the nanoparticles into tumor spheroids were enhanced, indicating the potential therapeutic application of the newly developed nanoparticles.

Rational Design of DNA Framework-Based Hybrid Nanomaterials for Anticancer Drug Delivery.

Engineered DNA frameworks have been extensively exploited as affinity scaffolds for drug delivery. However, few studies focus on the rational design to comprehensively improve their stability, internalization kinetics, and drug loading efficiency. Herein, DNA framework-based hybrid nanomaterials are rationally engineered by using a molecular docking tool, where the framework acts as a template to support conjugated polymers. The hybrid materials exhibit high stability in biofluids owning to the multiple interactions between DNA and cationic conjugated polymer. Through molecular docking, it is found that a specific structure of the conjugated polymer at major grooves of DNA gives rise to a unique pocket for small-molecular drug doxorubicin (DOX) yielding lower binding energy than conventional DOX binding sites. This increases the binding affinity of DOX, allowing for high drug loading content and efficiency, and preventing drug leakage under physiological condition. As a proof of concept, the hybrid nanomaterials equipped with aptamer are used to carry DOX and antisense oligonucleotide G3139, which effectively inhibits solid tumor growth and shows negligible side effects on mice. It is anticipated that this approach would find broad applications in hybrid materials design and precise medicine.

Miktoarm Star Polymers: Branched Architectures in Drug Delivery.

Delivering active pharmaceutical agents to disease sites using soft polymeric nanoparticles continues to be a topical area of research. It is becoming increasingly evident that the composition of amphiphilic macromolecules plays a significant role in developing efficient nanoformulations. Branched architectures with asymmetric polymeric arms emanating from a central core junction have provided a pivotal venue to tailor their key parameters. The build-up of miktoarm stars offers vast polymer arm tunability, aiding in the development of macromolecules with adjustable properties, and allows facile inclusion of endogenous stimulus-responsive entities. Miktoarm star-based micelles have been demonstrated to exhibit denser coronae, very low critical micelle concentrations, high drug loading contents, and sustained drug release profiles. With significant advances in chemical methodologies, synthetic articulation of miktoarm polymer architecture, and determination of their structure-property relationships, are now becoming streamlined. This is helping advance their implementation into formulating efficient therapeutic interventions. This review brings into focus the important discoveries in the syntheses of miktoarm stars of varied compositions, their aqueous self-assembly, and contributions their formulations are making in advancing the field of drug delivery.

Gold embedded chitosan nanoparticles with cell membrane mimetic polymer coating for pH-sensitive controlled drug release and cellular fluorescence imaging.

In this work, gold embedded chitosan nanoparticles (Au@CS NPs) were fabricated by a one-pot method. The benzaldehyde-terminated poly[(2-methacryloyloxy) ethyl phosphorylcholine] (PMPC) was applied to modification of the gold doped chitosan nanoparticles. The obtained Au@CS-PMPC NPs had the diameter of 135 nm with a narrow distribution. The size of the Au@CS-PMPC NPs, as well as the size of the embedded gold NPs, might be well-controlled by adjusting the feeding ratio between chitosan and HAuCl4. Furthermore, the Au@CS-PMPC NPs showed increased colloidal stability, high drug loading content, pH-responsive drug release, excellent biocompatibility and bright fluorescence emission. The results demonstrated that Au@CS-PMPC NPs showed a great potential for tumor therapy via the combination advantages of pH-sensitive controlled drug release and cellular fluorescence imaging.

Site-Selective, Multistep Functionalizations of CO2-Based Hyperbranched Poly(alkynoate)s toward Functional Polymetric Materials.

Hyperbranched polymers constructed from CO2 possess unique architectures and properties; however, they are difficult to prepare. In this work, CO2‐based, hyperbranched poly(alkynoate)s (hb‐PAs) with high molecular weights and degrees of branching are facilely prepared under atmospheric pressure in only 3 h. Because hb‐PAs possess two types of ethynyl groups with different reactivities, they can undergo site‐selective, three‐step functionalizations with nearly 100% conversion in each step. Taking advantage of this unique feature, functional hb‐PAs with versatile properties are constructed that could be selectively tailored to contain hydrophilic oligo(ethylene glycol) chains in their branched chains, on their periphery, or both via tandem polymerizations. Hyperbranched polyprodrug amphiphiles with high drug loading content (44.3 wt%) are also generated, along with an artificial light‐harvesting system with high energy transfer efficiency (up to 92%) and white‐light‐emitting polymers. This work not only provides an efficient pathway to convert CO2 into hyperbranched polymers, but also offers an effective platform for site‐selective multistep functionalizations toward functional polymeric materials.

Monodisperse Hollow MnO2 with Biodegradability for Efficient Targeted Drug Delivery.

The development of new nanocarriers with desired degradability and targeted ability is of great significance for efficient drug delivery. In this work, a monodisperse hollow structured MnO2 (H-MnO2) with a mesoporous shell is prepared and functionalized for efficient targeted drug delivery. The highly monodisperse H-MnO2 with a uniform morphology was obtained by in situ growing MnO2 on solid silica nanoparticles and subsequently removing the silica core. Then, the H-MnO2 is successively modified with polyethylene glycol and targeted molecule folate (FA). The resultant H-MnO2-FA shows excellent colloidal stability and high drug-loading content (∼58.2%) of the antitumor drug doxorubicin hydrochloride (DOX). The H-MnO2-FA possesses acid-responsive T1-weighted magnetic resonance imaging ability. The pH-dependent biodegradation behavior of H-MnO2-FA is directly observed in vitro and confirmed by in vivo imaging, which is expected to favor the potential clearance of this hollow structured nanocarrier and eliminate its long-term toxicity. In addition, the DOX-loaded H-MnO2-FA also demonstrates excellent cancer cell-killing effect and tumor inhibition efficacy.

Photosensitive Supramolecular Micelle-Mediated Cellular Uptake of Anticancer Drugs Enhances the Efficiency of Chemotherapy.

The development of stimuli-responsive supramolecular micelles with high drug-loading contents that specifically induce significant levels of apoptosis in cancer cells remains challenging. Herein, we report photosensitive uracil-functionalized supramolecular micelles that spontaneously form via self-assembly in aqueous solution, exhibit sensitive photo-responsive behavior, and effectively encapsulate anticancer drugs at high drug-loading contents. Cellular uptake analysis and double-staining flow cytometric assays confirmed the presence of photo-dimerized uracil groups within the irradiated micelles remarkably enhanced endocytic uptake of the micelles by cancer cells and subsequently led to higher levels of apoptotic cell death, and thus improved the therapeutic effect in vitro. Thus, photo-dimerized uracil-functionalized supramolecular micelles may potentially represent an intelligent nanovehicle to improve the safety, efficacy, and applicability of cancer chemotherapy, and could also enable the development of nucleobase-based supramolecular micelles for multifunctional biomaterials and novel biomedical applications.

Polymersome Formation by Amphiphilic Polyglycerol-b-polydisulfide-b-polyglycerol and Glutathione-Triggered Intracellular Drug Delivery.

This article reports the synthesis, spontaneous self-assembly, highly efficient drug encapsulation, and glutathione (GSH)-triggered intracellular sustained drug delivery of an ABA-type amphiphilic triblock copolymer, namely, polyglycerol-b-poly(disulfide)-b-polyglycerol (PG-b-PDS-b-PG). The bioreducible PDS block with reactive pyridyldisulfide groups present at the chain terminals was attached to thiol-terminated heterotelechelic PG by a thiol-disulfide exchange reaction producing the amphiphilic PG-b-PDS-b-PG. It formed a stable polymersome in aqueous medium with a critical aggregation concentration of 0.02 mg/mL and average hydrodynamic diameter (Dh) of 230 nm and showed highly efficient and stable encapsulation of doxorubicin (Dox) with a remarkably high drug loading efficiency (DLE) and drug loading content (DLC) of 54% and 16%, respectively. Fluorescence spectroscopy studies revealed GSH-triggered drug release and strong dependence of the release kinetics on the GSH concentration due to degradation of the amphiphilic block copolymer and disassembly of the polymersome. MTT assay indicated excellent biocompatibility of the block copolymer as >90% cells (HeLa or MDA-MB-231) were found to be alive after 96 h of incubation with a polymer concentration of up to 1.0 mg/mL, which was further validated by the hemolysis assay. Cytotoxicity assay of the Dox-loaded polymersome exhibited time and dose-dependent sustained killing of HeLa as well as MDA-MB-231 cells wherein after 48 h of incubation >50% cell killing was noticed with a Dox concentration of ∼4.0 and ∼8.7 μg/mL, respectively, while the free Dox showed faster cell killing. Flow cytometry and live cell fluorescence microscopy studies revealed time-dependent cellular uptake of the drug-loaded polymersome followed by diffusion of the drug to the nucleus. Cells with artificially enhanced GSH were killed at a much faster rate indicating that intracellular GSH-triggered disassembly is the key drug release mechanism.

LHRH/TAT dual peptides-conjugated polymeric vesicles for PTT enhanced chemotherapy to overcome hepatocellular carcinoma

Combination therapy such as photothermal therapy (PTT) enhanced chemotherapy is regarded as a promising strategy for cancer treatment. Herein, we developed redox-responsive polymeric vesicles based on the amphiphilic triblock copolymer PCL-ss-PEG-ss-PCL. To avoid the limited therapeutic effect of chemotherapeutic drugs caused by systemic exposures and drug resistance, the redox-sensitive polymeric vesicles were cargoed with two chemotherapeutics: doxorubicin (DOX) and paclitaxel (PTX). Besides, indocyanine green (ICG) was encapsulated, and cell-penetrating peptides and LHRH targeting molecule were modified on the surface of polymeric vesicles. The results indicated that the polymeric vesicles can load different kinds of drugs with high drug loading content, trigger drug release in responsive to the reductive environment, realize high cellular uptake via dual peptides and laser irradiation, and achieve higher cytotoxicity via chemo-photothermal combination therapy. Hence, the redox-responsive LHRH/TAT dual peptides-conjugated PTX/DOX/ICG co-loaded polymeric micelles exhibited great potential in tumor-targeting and chemo-photothermal therapy.

Fabrication of unimolecular micelle-based nanomedicines from hyperbranched polymers containing both terminal and internal reactive groups

Unimolecular micelles are an attractive type of nanocarriers for drug delivery, but developing unimolecular micelle-based nanomedicine with high drug loading capacity and excellent unimolecular stability is challenging. Herein, we report the design and synthesis of hyperbranched polymers containing both terminal and internal reactive groups for fabricating the unimolecular micelle-based nanocarriers with high drug loading ability and superior unimolecular stability using selective modification. Specifically, we synthesized hyperbranched poly(amino ester)s containing terminal acrylate groups and internal R groups (named HBPAE-R) via the Michael addition polymerization of A2 + BʹB2-R monomers, wherein A represents acrylate, and B, Bʹ represents the hydrogen in primary amine and secondary amine group, respectively, whereas R represents hydroxy, alkene or alkyne groups that do not participate in the polymerization process but assist in additional modification. Then, poly(ethylene glycol) (PEG) chains were linked to the surface of HBPAE-OH (representative molecules) with the subsequent conjugation of doxorubicin (DOX, representative drug) to the internal hydroxy groups through an acid-labile hydrazide bond, to afford anti-cancer drug-loaded hyperbranched star copolymers PEG-HBPAE-DOX. The obtained nanomedicines exhibited good unimolecular stability, relatively high drug loading content and a controlled drug release behavior. The in vitro cytotoxicity experiments further demonstrated the anti-tumor efficacy of these unimolecular nanomedicines. Our approach is expected to further boost research on the fabrication of multifunctional unimolecular nanomedicines from hyperbranched polymers containing both terminal and internal reactive groups.

Folate-receptor mediated pH/reduction-responsive biomimetic nanoparticles for dually activated multi-stage anticancer drug delivery

How to overcome the cell membrane barriers and achieve release payloads efficiently in the cytoplasm have been major challenges for anticancer drug delivery and therapeutic effects with nanosystems. In this study, bovine serum albumin (BSA) was modified with folate acid and histamine, which was then used as the nanocarrier for the antitumor agent doxorubicin (DOX). The DOX-loaded nanoparticles (DOX/FBH-NPs) were prepared via a crosslinking method, and the release of DOX from these nanoparticles (NPs) exhibited pH/reduction-responsive behaviors in vitro. These NPs interacted with the folate receptor overexpressed on the cell membrane of 4T1 cells and achieved enhanced endocytosis. Afterwards, these NPs exhibited pH-responsiveness within endo-lysosomes and escaped from endosomes due to the "proton sponge" effect, and then completed release of DOX was triggered by high concentration of glutathione (GSH) in cytoplasm. Thus, DOX/FBH-NPs exhibited excellent cytotoxicity against 4T1 cells in vitro. Benefited from the enhanced permeability and retention (EPR) effect and folate receptor-mediated endocytosis, these NPs gained satisfied tumor-targeting effects in vivo and efficient delivery of DOX to tumor tissues. As a result, these NPs exhibited enhanced antitumor effects and reduced side effects in vivo. In conclusion, these BSA-based NPs modified with both folate acid and histamine showed enhanced tumor-targeting effects in vivo with good biocompatibility and intracellular pH/reduction-responsive behaviors, providing a promising strategy for the efficient delivery of antitumor agents.

Amphiphilic star copolymers-mediated co-delivery of doxorubicin and avasimibe for effective combination chemotherapy

The combination therapy by using two or more chemotherapeutic agents with different action mechanisms has shown to be an attractive strategy for cancer treatment with synergistic therapeutic effects, and also the side effects reduction by one agent replacing part of another one. In this work, an amphiphilic star copolymer with an H40 hyperbranched polyester as the core and poly(e-caprolactone)-poly(2-dimethylaminoethylmethacrylate) copolymer incorporated with the fluorescent DTM groups as the arms were designed to encapsulate the model anti-cancer drug, doxorubicin (DOX), and a novel potential agent, avasimibe (Ava). Those two drugs could inhibit DNA replication and block acyl-CoA cholesterol acyltransferase-1 (ACAT-1) to induce the cell apoptosis, respectively. The model drugs could be easily loaded into the micelles with a high total drug-loading content toward 24.6% by altering the feeding drug ratios. Three molar ratios (DOX:Ava = 3:1, 1:1, and 1:3) of the drug-loaded micelles were prepared and evaluated for in vitro antitumor efficacy. Results showed that the micelles with 1:1 ratio exhibited the best synergistic cytotoxic activity against both K562 and HeLa cells. Furthermore, the dual-drug combination with efficient anticancer performance was also confirmed by live/dead staining, apoptosis, and cell cycle analysis. Moreover, the internalization of these dual-drug-loaded micelles could be monitored by fluorescent DTM groups and DOX. All these results suggested that the addition of Ava could cut down the dose of DOX to reduce its potential side effects and the co-delivery system could be a promising approach for an effective combination chemotherapy.