Folate-conjugated amphiphilic block copolymer micelle for targeted and redox-responsive delivery of doxorubicin

Stimuli-Responsive Aliphatic Polycarbonate Nanocarriers for Tumor-Targeted Drug Delivery

Nanoparticles based on amphiphilic copolymers with tunable physicochemical properties can be used to encapsulate delicate pharmaceutics while at the same time improving their solubility, stability, pharmacokinetic properties, reducing immune surveillance, or achieving tumor-targeting ability. Those nanocarriers based on biodegradable aliphatic polycarbonates are a particularly promising platform for drug delivery due to flexibility in the design and synthesis of appropriate monomers and copolymers. Current studies in this field focus on the design and the synthesis of new effective carriers of hydrophobic drugs and their release in a controlled manner by exogenous or endogenous factors in tumor-specific regions. Reactive groups present in aliphatic carbonate copolymers, undergo a reaction under the action of a stimulus: e.g., acidic hydrolysis, oxidation, reduction, etc. leading to changes in the morphology of nanoparticles. This allows the release of the drug in a highly controlled manner and induces a desired therapeutic outcome without damaging healthy tissues. The presented review summarizes the current advances in chemistry and methods for designing stimuli-responsive nanocarriers based on aliphatic polycarbonates for controlled drug delivery.

Nanomedicine-based tumor photothermal therapy synergized immunotherapy

The emerging anti-tumor immunotherapy has made significant progress in clinical application. However, single immunotherapy is not effective for all anti-tumor treatments, owing to the low objective response rate and the risk of immune-related side effects. Meanwhile, photothermal therapy (PTT) has attracted significant attention because of its non-invasiveness, spatiotemporal controllability and small side effects. Combining PTT with immunotherapy overcomes the issue that single photothermal therapy cannot eradicate tumors with metastasis and recurrence. However, it improves the therapeutic effect of immunotherapy, as the photothermal therapy usually promotes release of tumor-related antigens, triggers immune response by the immunogenic cell death (ICD), thereby, endowing unique synergistic mechanisms for cancer therapy. This review summarizes recent research advances in utilizing nanomedicines for PTT in combination with immunotherapy to improve the outcome of cancer treatment. The strategies include immunogenic cell death, immune agonists and cancer vaccines, immune checkpoint blockades and tumor specific monoclonal antibodies, and small-molecule immune inhibitors. The combination of synergized PTT-immunotherapy with other therapeutic strategies is also discussed.

Redox dual-stimuli responsive drug delivery systems for improving tumor-targeting ability and reducing adverse side effects

Cancer is a big challenge that has plagued the human beings for ages and one of the most effective treatments is chemotherapy. However, the low tumor-targeting ability limits the wide clinical application of chemotherapy. The microenvironment plays a critical role in many aspects of tumor genesis. It generates the tumor vasculature and it is highly implicated in the progression to metastasis. To maintain a suitable environment for tumor progression, there are special microenvironment in tumor cell, such as low pH, high level of glutathione (GSH) and reactive oxygen species (ROS), and more special enzymes, which is different to normal cell. Microenvironment-targeted therapy strategy could create new opportunities for therapeutic targeting. Compared to other targeting strategies, microenvironment-targeted therapy strategy will control the drug release into tumor cells more accurately. Redox responsive drug delivery systems (DDSs) are developed based on the high level of GSH in tumor cells. However, there are also GSH in normal cell though its level is lower. In order to control the release of drugs more accurately and reduce side effects, other drug release stimuli have been introduced to redox responsive DDSs. Under the synergistic reaction of two stimuli, redox dual-stimuli responsive DDSs will control the release of drugs more accurately and quickly and even increase the accumulation. This review summarizes strategies of redox dual-stimuli responsive DDSs such as pH, light, enzyme, ROS, and magnetic guide to delivery chemotherapeutic agents more accurately, aiming at providing new ideas for further promoting the drug release, enhancing tumor-targeting and improving anticancer effects. To better illustrate the redox dual-stimuli responsive DDS, preparations of carriers are also briefly described in the review.

Folic acid-modified nonionic surfactant vesicles for gambogenic acid targeting: Preparation, characterization, and in vitro and in vivo evaluation

The aim of present study was to develop folic acid (FA)-modified nonionic surfactant vesicles (NISVs, niosomes) as carrier systems for targeted delivery of gambogenic acid (GNA). The FA-GNA-NISVs exhibited a mean particle size of 180.77 ± 2.41 nm with a narrow poly dispersion index of 0.147 ± 0.08 determined by dynamic light scattering. Transmission electron microscopy also revealed that the FA-GNA-NISVs were spherical with double-layer structure. Entrapment efficiency (EE%) and zeta potential of the optimal FA-GNA-NISVs were 87.84 ± 1.06% and -37.33 ± 0.33 mV, respectively. Differential scanning calorimetry demonstrated that the GNA was in a molecular or amorphous state inside the FA-NISVs in vitro release profiles suggested that FA-GNA-NISVs could release GNA at a sustained manner, and less than 60% of GNA was released from the FA-NISVs within 12 hours of dialysis. in vivo pharmacokinetic results illustrated that FA-GNA-NISVs had considerably higher C_max , area under curve (AUC_0 - t ) and accumulation in lung. The cell proliferation study shown that the FA-GNA-NISVs significantly enhanced the in vitro cytotoxicity against A549 cells. Flow cytometry and fluorescence microscopy further demonstrated that the FA-GNA-NISVs increased apoptosis compared with nonmodified GNA-NISVs and free GNA. Moreover, FA-GNA-NISVs induced A549 cell apoptosis in a dose-dependent manner. In addition, cellular uptake assays showed a higher uptake of FA-GNA-NISVs than GNA-NISVs as well as free GNA. Taken together, it could be concluded that FA-GNA-NISVs were proposed as a novel targeting carriers for efficient delivering of GNA to cancers cells.

Polymeric nanocarriers as stimuli-responsive systems for targeted tumor (cancer) therapy: Recent advances in drug delivery

In the last decade, considerable attention has been devoted to the use of biodegradable polymeric materials as potential drug delivery carriers. However, bioavailability and drug release at the disease site remain uncontrollable even with the use of polymeric nanocarriers. To address this issue, successful methodologies have been developed to synthesize polymeric nanocarriers incorporated with regions exhibiting a response to stimuli such as redox potential, temperature, pH, and light. The resultant stimuli-responsive polymeric nanocarriers have shown tremendous promise in drug delivery applications, owing to their ability to enhance the bioavailability of drugs at the disease site. In such systems, drug release is controlled in response to specific stimuli, either exogenous or endogenous. This review reports recent advances in the design of stimuli-responsive nanocarriers for drug delivery in cancer therapy. In particular, the synthetic methodologies investigated to date to introduce different types of stimuli-responsive elements within the biomaterials are described. The sufficient understanding of these stimuli-responsive nanocarriers will allow the development of a better drug delivery system that will allow us to solve the challenges encountered in targeted cancer therapy.

Folate-Targeted Anticancer Drug Delivery via a Combination Strategy of a Micelle Complex and Reducible Conjugation

Conjugation of various active targeting ligands to the surface of nanocarriers to realize specific recognition by the corresponding receptors localized on the membrane of the cancer cells has provided a powerful means toward enhanced cancer therapy. Folic acid (FA) is one of the most used targeting ligands due to the overexpressed FA receptors in many cancer cell lines. However, conjugation of hydrophobic FA to the surface of nanocarriers usually alters the hydrophilic/hydrophobic balance of the stabilized nanoparticles, leading to their thermodynamic instability and subsequent formation of aggregates, which apparently compromises the in vivo long circulation and minimized side effects of nanocarriers. The currently leading strategy to overcome this issue is to incorporate a protecting hydrophilic stealth that can be deshielded to expose the targeting ligand at the desired tumor site, which generally involves multistep chemical modifications, conjugations, and purifications. To develop a simple alternative toward FA-mediated enhanced anticancer drug delivery, a combination strategy of micelle complex and reducible conjugation was reported in this study. FA was first conjugated to the terminus of the hydrophilic block of a reduction-sensitive miktoarm star-shaped amphiphilic copolymer, PCL₃-SS-POEGMA₁, with the previously optimized star structure by click coupling via a reducible disulfide link. The resulting PCL₃-SS-POEGMA₁-SS-FA was further mixed with the parent PCL₃-SS-POEGMA₁ to afford a micelle complex with both reducibly conjugated and relatively low amount of FA-targeting ligands toward excellent FA-mediated targeted drug delivery without compromised salt stability in vitro and in vivo. Therefore, the combined strategy developed herein provides a simple and powerful means to promote FA-mediated anticancer drug delivery.

Biodegradable Redox-Sensitive Star Polymer Nanomicelles for Enhancing Doxorubicin Delivery

A typical amphiphilic star polymer adamantane-[poly(lactic-co-glycolic acid)-bis(2-carboxyethyl) sulfide-poly(ethylene glycol) monomethyl ether)]₄ with a specific hydrophilic/redox-sensitive/hydrophobic structure was designed and synthesized through ring opening and esterification reactions. The self-assembled nanomicelles were used as doxorubicin (DOX) delivery vehicles with suitable critical micelle concentrations (5.0 mg/L). After the drug being loaded, drug-loaded micelles showed good drug-loading efficiency (10.39%), encapsulation efficiency (58.1%), and drug release (up to 60%) under simulated biological environment conditions. In addition, the backbone structure of the biodegradable polymer was easily hydrolyzed by the action of biological enzymes. As expected, cell-based studies showed that the designed polymer micelles possessed good biocompatibility (a survival rate of 85% for NH-3T3 cells). Moreover, the drug (DOX) still maintained good anti-cancer effects after being loaded, which caused 40% of MCF-7 cells to survive. These redox-sensitive micelles showed anti-tumor therapeutic potential.

Nanocomposites as biomolecules delivery agents in nanomedicine

Nanoparticles (NPs) are atomic clusters of crystalline or amorphous structure that possess unique physical and chemical properties associated with a size range of between 1 and 100 nm. Their nano-sized dimensions, which are in the same range as those of vital biomolecules, such as antibodies, membrane receptors, nucleic acids, and proteins, allow them to interact with different structures within living organisms. Because of these features, numerous nanoparticles are used in medicine as delivery agents for biomolecules. However, off-target drug delivery can cause serious side effects to normal tissues and organs. Considering this issue, it is essential to develop bioengineering strategies to significantly reduce systemic toxicity and improve therapeutic effect. In contrast to passive delivery, nanosystems enable to obtain enhanced therapeutic efficacy, decrease the possibility of drug resistance, and reduce side effects of "conventional" therapy in cancers. The present review provides an overview of the most recent (mostly last 3 years) achievements related to different biomolecules used to enable targeting capabilities of highly diverse nanoparticles. These include monoclonal antibodies, receptor-specific peptides or proteins, deoxyribonucleic acids, ribonucleic acids, [DNA/RNA] aptamers, and small molecules such as folates, and even vitamins or carbohydrates.

Polymeric nanogels as drug delivery systems

The present review focuses on the description of the design, synthesis and physico-chemical and biological evaluation of polymer nanogels. Nanogels are robust swollen cross-linked polymer nanoparticles that can be used as highly efficient and biodegradable carriers for the transport of drugs in controlled drug delivery. In this article, various types of nanogels are described and methods for their preparation discussed. The possibility of using synthesized nanosystems for targeting are reviewed to show the potential of tailored structures to reach either solid tumor tissue or direct tumor cells. Finally, the methods for encapsulation or attachment of biologically active molecules, e.g. drugs, proteins, are described and compared.