Preparation and evaluation of poly(l-histidine) based pH-sensitive micelles for intracellular delivery of doxorubicin against MCF-7/ADR cells

Smart Nanoplatforms Responding to the Tumor Microenvironment for Precise Drug Delivery in Cancer Therapy

The tumor microenvironment (TME) is a complex and dynamic entity, comprising stromal cells, immune cells, blood vessels and extracellular matrix, which is intimately associated with the occurrence and development of cancers, as well as their therapy. Utilizing the shared characteristics of tumors, such as an acidic environment, enzymes and hypoxia, researchers have developed a promising cancer therapy strategy known as responsive release of nano-loaded drugs, specifically targeted at tumor tissues or cells. In this comprehensive review, we provide an in-depth overview of the current fundamentals and state-of-the-art intelligent strategies of TME-responsive nanoplatforms, which include acidic pH, high GSH levels, high-level adenosine triphosphate, overexpressed enzymes, hypoxia and reductive environment. Additionally, we showcase the latest advancements in TME-responsive nanoparticles. In conclusion, we thoroughly examine the immediate challenges and prospects of TME-responsive nanopharmaceuticals, with the expectation that the progress of these targeted nanoformulations will enable the exploitation, overcoming or modulation of the TME, ultimately leading to significantly more effective cancer therapy.

The Self-Assembly Soluplus Nanomicelles of Nobiletin in Aqueous Medium Based on Solid Dispersion and Their Increased Hepatoprotective Effect on APAP-Induced Acute Liver Injury

Purpose

APAP-induced liver injury (AILI) is a common cause of acute liver failure (ALF). Nobiletin (NOB) is a potential hepatoprotective agent for the treatment of APAP-induced liver injury. However, the poor solubility and low bioavailability of NOB hinders its application. In this study, a novel self-assembly nano-drug delivery system of nobiletin (solid dispersion of NOB, termed as NOB/SD) was developed based on solid dispersion technology to improve the bioavailability and hepatoprotective ability of NOB for APAP-induced liver injury therapy.

Methods

The optimized NOB/SD system was constructed using the amphiphilic copolymers of Soluplus and PVP/VA 64 via hot melt extrusion technology (HME). NOB/SD was characterized by solubility, physical interaction, drug release behavior, and stability. The bioavailability and hepatoprotective effects of NOB/SD were evaluated in vitro and in vivo.

Results

NOB/SD maintained NOB in matrix carriers in a stable amorphous state, and self-assembled NOB-loaded nanomicelles in water. Nanostructures based on solid dispersion technology exhibited enhanced solubility, improved release behavior, and promoted cellular uptake and anti-apoptosis in vitro. NOB/SD displayed significantly improved bioavailability in healthy Sprague Dawley (SD) rats in vivo. Furthermore, NOB/SD alleviated the APAP-induced liver injury by improving anti-oxidative stress with reactive oxygen species (ROS) scavenging and nuclear factor erythroid 2-related factor 2 (Nrf2) activation.

Conclusion

These results suggested that NOB/SD could be considered as a promising hepatoprotective nano-drug delivery system for attenuating APAP-induced acute liver injury with superior bioavailability and efficient hepatoprotection, which might provide an effective strategy for APAP-induced acute liver injury prevention and treatment.

Effect of Block Sequence on the Solution Self-Assembly of Symmetric ABCBA Pentablock Polymers in a Selective Solvent

Solution self-assembly of multiblock polymers offers a platform to create complex functional self-assembled nanostructures. However, a complete understanding of the effect of the different single-molecule-level parameters and solution conditions on the self-assembled morphology is still lacking. In this work, we have used dissipative particle dynamics to investigate the solution self-assembly of symmetric ABCBA linear pentablock polymers in a selective solvent and examined the effect of the block sequence, composition, and polymer concentration on the final morphology and polymer conformations. We confirmed that block sequence has an effect on the self-assembled morphologies, and it has a strong influence on polymer conformations that give place to physical gels for the sequence where the solvophilic block is located in the middle of the macromolecule. Our results are summarized in terms of morphology diagrams in the composition-concentration parameter space.

Preparation of a pH-responsive chitosan-montmorillonite-nitrogen-doped carbon quantum dots nanocarrier for attenuating doxorubicin limitations in cancer therapy

Despite its widespread usage as a chemotherapy drug in cancer treatment, doxorubicin (DOX) has limitations such as short in vivo circulation time, low solubility, and poor permeability. In this regard, a pH-responsive chitosan (CS)- montmorillonite (MMT)- nitrogen-doped carbon quantum dots (NCQDs) nanocomposite was first developed, loaded with DOX, and then incorporated into a double emulsion to further develop the sustained release. The incorporated NCQDs into the CS-MMT hydrogel exhibited enhanced loading and entrapment efficiencies. The presence of NCQDs nanoparticles in the CS-MMT hydrogel also resulted in an extended pH-responsive release of DOX over a period of 96 h compared to that of CS-MMT-DOX nanocarriers at pH 5.4. Based on the Korsmeyer-Peppas model, there was a controlled DOX release at pH 5.4, while no diffusion was observed at pH 7.4, indicating fewer side effects. MTT assay showed that the cytotoxicity of DOX-loaded CS-MMT-NCQDs hydrogel nanocomposite was significantly higher than those of free DOX (p < 0.001) and CS-MMT-NCQDs (p < 0.001) on MCF-7 cells. Flow cytometry results demonstrated that a higher apoptosis induction achieved after incorporating NCQDs nanoparticles into CS-MMT-DOX nanocarrier. These findings suggest that the DOX-loaded nanocomposite is a promising candidate for the targeted treatment of cancer cells.

Conformational Transition-Triggered Disassembly of Therapeutic Peptide Nanomedicine for Tumor Therapy

Cationic therapeutic peptides have received widespread attention due to their excellent antibacterial and antitumor properties. However, most of these peptides have undesirable delivery efficiency and high hemolytic toxicity due to the positively charged α-helix structure containing many lysine and arginine, which may restrict its in vivo applications. Herein, a conformationally transformed therapeutic peptide Pep-HCO₃ modified with bicarbonates on guanidine groups is designed. Such a design allows Pep-HCO₃ ((nap-RAGLQFPVGRLLRRLLRRLLR) nHCO₃ ) to self-assemble into nanoparticles (NP-Pep) due to disrupting helix folding and the formation of intermolecular hydrogen bonding between bicarbonates and guanidine groups. When pH is from 7.4 to 6.5 at the tumor sites, guanidine bicarbonate can be hydrolyzed to form CO₂ and guanidine groups, resulting in the disassembling of the NP-Pep into monomers α-Pep with a positively charged α-helix structure. In vivo, NP-Pep not only inhibits the tumor growth of xenografted mice with a twofold enhanced inhibition rate compared with α-Pep treatment group, but also significantly reduces the hemolytic toxicity by responding to the pH of tumor microenvironment. Therefore, the strategy of conformational transition-triggered disassembly of nanoparticles allows efficient delivery of cationic therapeutic peptides and lowering the hemolytic toxicity, which may provide an avenue for developing high-performance cationic peptide in vivo applications.

Tumor-Associated Fibroblast-Targeting Nanoparticles for Enhancing Solid Tumor Therapy: Progress and Challenges

Even though nanoparticle drug delivery systems (nanoDDSs) have improved antitumor efficacy by delivering more drugs to tumor sites compared to free and unencapsulated therapeutics, achieving satisfactory distribution and penetration of nanoDDSs inside solid tumors, especially in stromal fibrous tumors, remains challenging. As one of the most common stromal cells in solid tumors, tumor-associated fibroblasts (TAFs) not only promote tumor growth and metastasis but also reduce the drug delivery efficiency of nanoparticles through the tumor's inherent physical and physiological barriers. Thus, TAFs have been emerging as attractive targets, and TAF-targeting nanotherapeutics have been extensively explored to enhance the tumor delivery efficiency and efficacy of various anticancer agents. The purpose of this Review is to opportunely summarize the underlying mechanisms of TAFs on obstructing nanoparticle-mediated drug delivery into tumors and discuss the current advances of a plethora of nanotherapeutic approaches for effectively targeting TAFs.

Polymeric micelles in cancer therapy: State of the art

In recent years, polymeric micelles have been extensively utilized in pre-clinical studies for delivering poorly soluble chemotherapeutic agents in cancer. Polymeric micelles are formed via self-assembly of amphiphilic polymers in facile manners. The wide availability of hydrophobic and, to some extent, hydrophilic polymeric blocks allow researchers to explore various polymeric combinations for optimum loading, stability, systemic circulation, and delivery to the target cancer tissues. Moreover, polymeric micelles could easily be tailor-made by increasing and decreasing the number of monomers in each polymeric chain. Some of the widely accepted hydrophobic polymers are poly(lactide) (PLA), poly(caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), polyesters, poly(amino acids), lipids. The hydrophilic polymers used to wrap the hydrophobic core are poly(ethylene glycol), poly(oxazolines), chitosan, dextran, and hyaluronic acids. Drugs could be conjugated to polymers at the distal ends to prepare pharmacologically active polymeric systems that impart enhanced solubility and stability of the conjugates and provide an opportunity for combination drug delivery. Their nano-size enables them to accumulate to the tumor microenvironment via the Enhanced Permeability and Retention (EPR) effect. Moreover, the stimuli-sensitive breakdown provides the micelles an effective means to deliver the therapeutic cargo effectively. The tumor micro-environmental stimuli are pH, hypoxia, and upregulated enzymes. Externally applied stimuli to destroy micellar disassembly to release the payload include light, ultrasound, and temperature. This article delineates the current trend in developing polymeric micelles combining various block polymeric scaffolds. The development of stimuli-sensitive micelles to achieve enhanced therapeutic activity are also discussed.

Bioresorbable Polymers: Advanced Materials and 4D Printing for Tissue Engineering

Three-dimensional (3D) printing is a valuable tool in the production of complexes structures with specific shapes for tissue engineering. Differently from native tissues, the printed structures are static and do not transform their shape in response to different environment changes. Stimuli-responsive biocompatible materials have emerged in the biomedical field due to the ability of responding to other stimuli (physical, chemical, and/or biological), resulting in microstructures modifications. Four-dimensional (4D) printing arises as a new technology that implements dynamic improvements in printed structures using smart materials (stimuli-responsive materials) and/or cells. These dynamic scaffolds enable engineered tissues to undergo morphological changes in a pre-planned way. Stimuli-responsive polymeric hydrogels are the most promising material for 4D bio-fabrication because they produce a biocompatible and bioresorbable 3D shape environment similar to the extracellular matrix and allow deposition of cells on the scaffold surface as well as in the inside. Subsequently, this review presents different bioresorbable advanced polymers and discusses its use in 4D printing for tissue engineering applications.

Synthesis and Characterization of the Novel Nε-9-Fluorenylmethoxycarbonyl-l-Lysine N-Carboxy Anhydride. Synthesis of Well-Defined Linear and Branched Polypeptides

The synthesis of well-defined polypeptides exhibiting complex macromolecular architectures requires the use of monomers that can be orthogonally deprotected, containing primary amines that will be used as the initiator for the Ring Opening Polymerization (ROP) of N-carboxy anhydrides. The synthesis and characterization of the novel monomer N^ε-9-Fluorenylmethoxycarbonyl-l-Lysine N-carboxy anhydride (N^ε-Fmoc-l-Lysine NCA), as well as the novel linear Poly(N^ε-Fmoc-l-Lys)_n homopolypeptide and Poly(l-Lysine)₇₈-block-[Poly(l-Lysine)₁₀-graft-Poly(l-Histidine)₁₅] block-graft copolypeptide, are presented. The synthesis of the graft copolypeptide was conducted via ROP of the N^ε-Boc-l-Lysine NCA while using n-hexylamine as the initiator, followed by the polymerization of N^ε-Fmoc-l-Lysine NCA. The last block was selectively deprotected under basic conditions, and the resulting ε-amines were used as the initiating species for the ROP of N^im-Trityl-l-Histidine NCA. Finally, the Boc- and Trt- groups were deprotected by TFA. High Vacuum Techniques were applied to achieve the conditions that are required for the synthesis of well-defined polypeptides. The molecular characterization indicated that the polypeptides exhibited high degree of molecular and compositional homogeneity. Finally, Dynamic Light Scattering, ζ-potential, and Circular Dichroism measurements were used in order to investigate the ability of the polypeptide to self-assemble in different conditions. This monomer opens avenues for the synthesis of polypeptides with complex macromolecular architectures that can define the aggregation behavior, and, therefore, can lead to the synthesis of "smart" stimuli-responsive nanocarriers for controlled drug delivery applications.

Tumor microenvironment responsive drug delivery systems

Conventional tumor-targeted drug delivery systems (DDSs) face challenges, such as unsatisfied systemic circulation, low targeting efficiency, poor tumoral penetration, and uncontrolled drug release. Recently, tumor cellular molecules-triggered DDSs have aroused great interests in addressing such dilemmas. With the introduction of several additional functionalities, the properties of these smart DDSs including size, surface charge and ligand exposure can response to different tumor microenvironments for a more efficient tumor targeting, and eventually achieve desired drug release for an optimized therapeutic efficiency. This review highlights the recent research progresses on smart tumor environment responsive drug delivery systems for targeted drug delivery. Dynamic targeting strategies and functional moieties sensitive to a variety of tumor cellular stimuli, including pH, glutathione, adenosine-triphosphate, reactive oxygen species, enzyme and inflammatory factors are summarized. Special emphasis of this review is placed on their responsive mechanisms, drug loading models, drawbacks and merits. Several typical multi-stimuli responsive DDSs are listed. And the main challenges and potential future development are discussed.

Role of Lipid-Based and Polymer-Based Non-Viral Vectors in Nucleic Acid Delivery for Next-Generation Gene Therapy

The field of gene therapy has experienced an insurgence of attention for its widespread ability to regulate gene expression by targeting genomic DNA, messenger RNA, microRNA, and short-interfering RNA for treating malignant and non-malignant disorders. Numerous nucleic acid analogs have been developed to target coding or non-coding sequences of the human genome for gene regulation. However, broader clinical applications of nucleic acid analogs have been limited due to their poor cell or organ-specific delivery. To resolve these issues, non-viral vectors based on nanoparticles, liposomes, and polyplexes have been developed to date. This review is centered on non-viral vectors mainly comprising of cationic lipids and polymers for nucleic acid-based delivery for numerous gene therapy-based applications.

Redox-responsive biocompatible nanocarriers based on novel heparosan polysaccharides for intracellular anticancer drug delivery

Heparosan is a natural precursor of heparin biosynthesis in mammals. It is stable in blood circulation but can be degraded in lysosomes, showing good biocompatibility and long circulation features. So heparosan can be designed as anticancer drug carriers to increase tumor selectivity and improve the therapeutic effect. A novel redox-sensitive heparosan-cystamine-vitamin E succinate (KSV) micelle system was constructed for intracellular delivery of doxorubicin (DOX). Simultaneously, the redox-insensitive heparosan-adipic acid dihydrazide-vitamin E succinate copolymer (KV) was synthesized as control. DOX-loaded micelles (DOX/KSV) with an average particle size of 90-120 nm had good serum stability and redox-triggered depolymerization. In vitro drug release test showed that DOX/KSV micelles presented obvious redox-triggered release behavior compared with DOX/KV. Cytotoxicity and cell uptake were investigated using MGC80-3 tumor cells and COS7 fibroblast-like cells. The cell survival rate of blank micelles was more than 90%, and the cytotoxicity of DOX/KSV in MGC80-3 cells was higher than in COS7 cells, indicating that the carrier has better biocompatibility and less toxicity side effect. The cytotoxicity of DOX/KSV against MGC80-3 cells was significantly greater than that of free DOX and DOX/KV. Furthermore, compared with DOX/KV in MGC80-3 cells, DOX/KSV micelles uptook more anticancer drugs and then released DOX faster into the cell nucleus. The micelles were endocytosed by multiple pathways, but clathrin-mediated endocytosis was the main pathway. Therefore, heparosan polysaccharide could be a potential option as anticancer carrier for enhancing efficacy and mitigating toxicity.

Biodegradable reduction-responsive polymeric micelles for enhanced delivery of melphalan to retinoblastoma cells

Melphalan (MEL) is an effective chemotherapeutic agent for treatment of retinoblastoma (Rb) which is the most common childhood malignancy. However, the inherent cardiopulmonary toxicity and hazardous integration limit its therapeutic effect on RB. N-Acetylheparosan (AH), a natural heparin-like polysaccharide in mammals with long circulation effect and good biocompatibility, was linked by d-α-tocopherol acid succinate (VES) via and cystamine (CYS) to synthesize reduction-responsive N-acetylheparosan-CYS-Vitamin E succinate (AHV) copolymers. In addition, CYS was replaced by adipic acid dihydrazide (ADH) to obtain a control of non-reduction-responsive polymers N-acetylheparosan-ADH-Vitamin E succinate (ADV). MEL-loaded AHV micelles (MEL/AHV) as well as ADV micelles (MEL/ADV) were prepared with small particle size and high drug loading content. In vitro drug release showed that MEL/AHV micelles presented obvious reduction-triggered release behavior compared with MEL/ADV. In vitro antitumor effects were investigated using WERI-Rb-1 retinoblastoma cells. Cytotoxicity experiments showed that the IC₅₀ of MEL/AHV was significantly lower than that of free MEL and MEL/ADV, suggesting that MEL/AHV enhanced the cytotoxicity against retinoblastoma cells. Furthermore, MEL/AHV micelles were more easily uptaken by multiple pathways compared with MEL/ADV and free MEL. Therefore, MEL/AHV might be a potential delivery system for enhanced delivery of melphalan to Rb cells.

Multi-Modulation of Doxorubicin Resistance in Breast Cancer Cells by Poly(l-histidine)-Based Multifunctional Micelles

Even though the reversal of multi-drug resistance (MDR) by numerous nanoparticles has been extensively studied, limited success has been achieved. To overcome this barrier, we report a rationally-designed pH-sensitive micelle, in which doxorubicin (Dox) and resveratrol (Res) were co-loaded. The micelle was based on methoxy poly (ethylene glycol)-poly(d,l-lactide)-poly(l-histidine) (mPEG-PLA-PHis), which integrated passive targeting, endo-lysosomal escape and pH-responsive payloads release. At a physiological pH of 7.4 (slightly alkali), Dox and Res were incorporated into the micelles core using the thin-film hydration method (pH-endoSM/Dox/Res). After cellular uptake, the micelles exhibited an enhanced dissociation in response to the acidic endosomes, triggering the release of Res and Dox. Furthermore, Res was observed to synergistically improve the cytotoxicity of Dox by down-regulating the P-glycoprotein (P-gp) expression, decreasing the membrane potential of the mitochondrial and ATP level, as well as inducing cell apoptosis mediated by mitochondria. The pH-endoSM/Dox/Res showed a prominent ability to decrease the IC50 of Dox by a factor of 17.38 in cell cytotoxicity against the MCF-7/ADR cell line. In vivo distribution demonstrated the excellent tumor-targeting ability of the pH-endoSM/Dox/Res. All results indicated that pH-endoSM/Dox/Res held great potential for the treatment of Dox-resistance breast cancer cells.

Paclitaxel delivered by CD44 receptor-targeting and endosomal pH sensitive dual functionalized hyaluronic acid micelles for multidrug resistance reversion

The drug efflux mediated by P-glycoprotein (P-gp) transporter is a major factor responsible for multidrug resistance (MDR) of paclitaxel (PTX). The efficient intracellular PTX delivery is a promising strategy for overcoming the MDR of tumor cells. A CD44 receptor targeting and endosome-pH sensitive dual functionalized hyaluronic acid-deoxycholic acid-histidine (HA-DOCA-His) micellar formulation was developed to overcome MDR, and a CD44 receptor targeting hyaluronic acid-deoxycholic acid (HA-DOCA) micelles was used as a comparison. Compared with Taxol solution and HA-DOCA micelles, the cytotoxicity of PTX loaded in HA-DOCA-His micelles against drug-resistant tumor cells was improved significantly and possessed superior MDR-overcoming performance; this phenomenon is due to the increased intracellular PTX delivery by CD44 receptor-mediated endocytosis pathway and endosome-pH sensitivity-mediated PTX triggering release. Upon pharmacokinetic study, PTX/HA-DOCA-His micelles demonstrated longer blood circulation time, larger AUC, decreased V_d and CL than the Taxol solution. More importantly, PTX/HA-DOCA-His micelles were more effective in tumor growth inhibition in MCF-7/Adr tumor-bearing mice compared with PTX/HA-DOCA micelles and Taxol solution. Dual targeting strategy-functionalized HA-DOCA-His micelles demonstrated excellent MDR-reversing ability for therapeutic efficacy and improvement on MDR tumors, thereby providing an effective targeting strategy for PTX delivery of nano-drug delivery system in MDR cancer chemotherapy.

An in vitro assessment of novel chitosan/bimetallic PtAu nanocomposites as delivery vehicles for doxorubicin

AIM

To synthesize and functionalize platinum (core)-gold (shell) bimetallic nanoparticles (PtAuBNps) with chitosan and doxorubicin to display favorable pharmacokinetics, biodegradability, biological activity and safety in vitro.

MATERIALS & METHODS

PtAuBNps and their drug nanocomposites were morphologically and physico-chemically characterized. Binding studies determined the efficiency and stability of the platform. In vitro release kinetics were evaluated under simulated environments, cytotoxicity profiles through MTT and Sulforodhamine B assays and apoptosis induction using the dual EtBr/AO staining.

RESULTS & DISCUSSION

The results obtained indicate that functionalized PtAuBNps displayed favorable physio-chemical attributes, high binding capabilities, pH-triggered drug release through zero-order release kinetics, cell-specific cytotoxicity and good colloidal stability.

CONCLUSION

The positive attributes of this novel delivery system bodes well for future in vivo studies.