Self-assembled micelles of amphiphilic poly(L-phenylalanine)-b-poly(L-serine) polypeptides for tumor-targeted delivery

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Fundamental advances in hydrogels for the development of the next generation of smart delivery systems as biopharmaceuticals

Recent advances in developing and applying therapeutic peptides for anticancer, antimicrobial and immunomodulatory remedies have opened a new era in therapeutics. This development has resulted in the engineering of new biologics as part of a concerted effort by the pharmaceutical industry. Many alternative routes of administration and delivery vehicles, targeting better patient compliance and optimal therapeutic bioavailability, have emerged. However, the design of drug delivery systems to protect a range of unstable macromolecules, including peptides and proteins, from high temperatures, acidic environments, and enzymatic degradation remains a priority. Herein, we give chronological insights in the development of controlled-release drug delivery systems that occurred in the last 70 years or so. Subsequently, we summarise the key physicochemical characteristics of hydrogels contributing to the development of protective delivery systems concerning drug-targeted delivery in the chronospatial domain for biopharmaceuticals. Furthermore, we shed some light on promising hydrogels that can be utilised for systemic bioactive administration.

Combined Shikonin-Loaded MPEG-PCL Micelles Inhibits Effective Transition of Endothelial-to-Mesenchymal Cells

Introduction

Shikonin is well known for its anti-inflammatory activity in cardiovascular diseases. However, the application of shikonin is limited by its low water solubility and poor bioavailability. Methoxy poly (ethylene glycol)-b-poly (ε-caprolactone) (MPEG-PCL) is considered a promising delivery system for hydrophobic drugs. Therefore, in this study, we prepared shikonin-loaded MPEG-PCL micelles and investigated their effect on endothelial-to-mesenchymal transition (EndMT) induced by inflammatory cytokines.

Methods

Shikonin was encapsulated in MPEG-PCL micelles using an anti-solvent method and the physiochemical characteristics of the micelles (particle size, zeta potential, morphology, critical micelle concentration (CMC), drug loading and encapsulation efficiency) were investigated. Cellular uptake of micelles in human umbilical vein endothelial cells (HUVECs) was evaluated using fluorescence microscopy. In vitro EndMT inhibition was explored in HUVECs by quantitative real-time PCR analysis.

Results

The average particle size of shikonin-loaded MPEG-PCL micelles was 54.57±0.13 nm and 60 nm determined by dynamic light scattering and transmission electron microscopy, respectively. The zeta potential was −6.23±0.02 mV. The CMC of the micelles was 6.31×10⁻⁷mol/L. The drug loading and encapsulation efficiency were 0.88±0.08% and 43.08±3.77%, respectively. The MPEG-PCL micelles significantly improved the cellular uptake of cargo with low water solubility. Real-time PCR analysis showed that co-treatment with TNF-α and IL-1β successfully induced EndMT in HUVECs, whereas this process was significantly inhibited by shikonin and shikonin-loaded MPEG-PCL micelles, with greater inhibition mediated by the shikonin-loaded MPEG-PCL micelles.

Conclusion

Shikonin-loaded MPEG-PCL micelles significantly improved the EndMT-inhibiting effect of the free shikonin. MPEG-PCL is suitable for use more generally as a lipophilic drug carrier.

Spanning BODIPY fluorescence with self-assembled micellar clusters

BODIPY dyes possess favorable optical properties for a variety of applications including in vivo and in vitro diagnostics. However, their utilization might be limited by their water insolubility and incompatibility with chemical modifications, resulting in low aggregation stability. Here, we outline the route for addressing this issue. We have demonstrated two approaches, based on dye entrapment in micellar coordination clusters (MCCs); this provides a general solution for water solubility as well as aggregation stability of the seven BODIPY derivatives. These derivatives have various bulky aromatic substituents in the 2,3,5,6- and meso-positions and can rotate relative to a dipyrrin core, which also provides molecular rotor properties. The molecular structural features and the presence of aromatic groups allows BODIPY dyes to be used as "supporting molecules", thus promoting micelle-micelle interaction and micellar network stabilization. In the second approach, self-micellization, following BODIPY use, leads to MCC formation without the use of any mediators, including chelators and/or metal ions. In both approaches, BODIPY exhibits an excellent optical response, at a concentration beyond its solubilization limit in aqueous media and without undesired crystallization. The suggested approaches represent systems used to encapsulate BODIPY in a capsule-based surfactant environment, enabling one to track the aggregation of BODIPY; these approaches represent an alternative system to study and apply BODIPY's molecular rotor properties. The stabilized compounds, i.e., the BODIPY-loaded MCCs, provide a unique feature of permeability to hydrophilic ligand-switching proteins such as BSA; they exhibit a bright "turn-on" fluorescence signal within the clusters via macromolecular complexation, thus expanding the possibilities of water-soluble BODIPY-loaded MCCs utilization for functional indicators.

Micelles as potential drug delivery systems for colorectal cancer treatment

Despite the significant progress in cancer therapy, colorectal cancer (CRC) remains one of the most fatal malignancies worldwide. Chemotherapy is currently the mainstay therapeutic modality adopted for CRC treatment. However, the long-term effectiveness of chemotherapeutic drugs has been hampered by their low bioavailability, non-selective tumor targeting mechanisms, non-specific biodistribution associated with low drug concentrations at the tumor site and undesirable side effects. Over the last decade, there has been increasing interest in using nanotechnology-based drug delivery systems to circumvent these limitations. Various nanoparticles have been developed for delivering chemotherapeutic drugs among which polymeric micelles are attractive candidates. Polymeric micelles are biocompatible nanocarriers that can bypass the biological barriers and preferentially accumulate in tumors via the enhanced permeability and retention effect. They can be easily engineered with stimuli-responsive and tumor targeting moieties to further ensure their selective uptake by cancer cells and controlled drug release at the desirable tumor site. They have been shown to effectively improve the pharmacokinetic properties of chemotherapeutic drugs and enhance their safety profile and anticancer efficacy in different types of cancer. Given that combination therapy is the new strategy implemented in cancer therapy, polymeric micelles are suitable for multidrug delivery and allow drugs to act concurrently at the action site to achieve synergistic therapeutic outcomes. They also allow the delivery of anticancer genetic material along with chemotherapy drugs offering a novel approach for CRC therapy. Here, we highlight the properties of polymeric micelles that make them promising drug delivery systems for CRC treatment. We also review their application in CRC chemotherapy and gene therapy as well as in combination cancer chemotherapy.

Self-Assembling Glycopeptide Conjugate as a Versatile Platform for Mimicking Complex Polysaccharides

Polysaccharides are a class of carbohydrates that play pivotal roles in living systems such as being chemical messengers in many vital biological pathways. However, the complexity and heterogeneity of these natural structures have posed daunting challenges on their production, characterization, evaluation, and applications. While there have been various types of synthetic skeletons that could mimic some biological aspects of polysaccharides, a safer and more easily accessed system is still desired to avoid the unnatural components and difficulties in modifying the structures. In this work, conveniently accessible self-assembling glycopeptide conjugates are developed, where the natural O-glycosidic linkages and phosphoryl modifications assist the self-assembly and concurrently reduce the risk of toxicity. The generated nanoparticles in aqueous solution offer a multivalent display of structurally controllable carbohydrates as mimics of polysaccharides, among which a mannosylated version exhibits immunostimulatory effects in both cellular assays and vaccination of mice. The obtained results demonstrate the potential of this glycopeptide conjugate-derived platform in exploiting the intriguing properties of carbohydrates in a more structurally maneuverable fashion.

Co-disposition of chitosan nanoparticles by multi types of hepatic cells and their subsequent biological elimination: the mechanism and kinetic studies at the cellular and animal levels

Background: The clearance of nanomaterials (NMs) from the liver is essential for clinical safety, and their hepatic clearance is primarily determined by the co-disposition process of various types of hepatic cells. Studies of this process and the subsequent clearance routes are urgently needed for organic NMs, which are used as drug carriers more commonly than the inorganic ones. Materials and methods: In this study, the co-disposition of chitosan-based nanoparticles (CsNps) by macrophages and hepatocytes at both the cellular and animal levels as well as their subsequent biological elimination were investigated. RAW264.7 and Hepa1-6 cells were used as models of Kupffer cells and hepatocytes, respectively. Results: The cellular studies showed that CsNps released from RAW264.7 cells could enter Hepa1-6 cells through both clathrin- and caveolin-mediated endocytosis. The transport from Kupffer cells to hepatocytes was also studied in mice, and it was observed that most CsNps localized to the hepatocytes after intravenous injection. Following the distribution in hepatocytes, the hepatobiliary-fecal excretion route was shown to be the primary elimination route for CsNps, besides the kidney-urinary excretion route. The elimination of CsNps in mice was a lengthy process, with a half time of about 2 months. Conclusion: The demonstration in this study of the transport of CsNps from macrophages to hepatocytes and the subsequent hepatobiliary-fecal excretion provides basic information for the future development and clinical application of NMs.

The effect of PEG functionalization on the in vivo behavior and toxicity of CdTe quantum dots

CdTe quantum dots (QDs) are considered a potential toxic substance because they contain metal ions. However, most toxicology data are derived from in vitro studies or limited in vivo analysis and may not reflect in vivo responses and biodistribution. Proper modification is one of the most widely used routes to reduce the toxicity of QDs. Herein, we demonstrated the role of polyethylene glycol (PEG) in decreasing the toxicity of QDs by studying the animal survival, clinical biochemistry, organ histology, biodistribution and oxidative stress in thioglycolic acid (TGA)- and mercapto-acetohydrazide (TGH)-stabilized CdTe QD (TGA/TGH-CdTe QD)-treated groups. Via the histology, transmission electron microscopy (TEM) and biodistribution results, it was found that the QDs mainly accumulated in the liver and kidney at 7 days post-injection, and obvious tissue damage was also observed in the bare TGA/TGH-CdTe QD group. Based on the evaluation of oxidative stress in the liver and kidney, the indicators exhibited an obvious variation with a high dose of TGA/TGH-CdTe QDs. In contrast, the QD aggregation decreased in the liver and kidney with no clear physiological index variation after PEG functionalization. Thus, PEG plays an important role in decreasing the toxicity of the CdTe QDs, and both the accumulation of cadmium and oxidative stress variation instead of an isolation factor are responsible for the in vivo toxicity of these QDs.

CdTe quantum dots (QDs) are considered a potential toxic substance because they contain metal ions.

Micellar delivery of dasatinib for the inhibition of pathologic cellular processes of the retinal pigment epithelium

The objective of this study was to fabricate dasatinib-loaded nanoparticles and evaluate their efficacy in inhibiting cellular processes of the retinal pigment epithelium (RPE) related to proliferative vitreoretinopathy (PVR), for which there are no approved pharmacological approaches. We successfully encapsulated dasatinib, a poorly soluble multi-targeted tyrosine kinase inhibitor which has great potential for the treatment of PVR, into nanoparticles prepared from micellation of PEG-b-PCL. The size of the nanomicelles was approximately 55nm with a narrow distribution. They increased the solubility of dasatinib by 475× and provided a sustained drug release. ARPE-19, an immortal RPE cell line, was used to assess the in vitro efficacy of micellar dasatinib because the RPE is believed to play a key role in the pathogenesis of PVR. Three cell-based assays, namely, proliferation, adhesion and migration, which represent three important PVR-related cellular changes of the RPE, were conducted and the cytotoxicity of micelles was also evaluated. Both blank and dasatinib-loaded micelles were non-cytotoxic towards ARPE-19 cells. Micellar dasatinib significantly inhibited cell proliferation, adhesion and migration compared to the free drug; this might be attributable to enhanced solubility. PEG-b-PCL micelles were taken up into the ARPE-19 cells by an energy-dependent clatharin and caveolae-mediated endocytosis. Our results indicated that cellular uptake and the anti-proliferation effect of drugloaded micelles were linearly correlated. Drug loading appears to be a critical parameter for cellular uptake which in turn impacts the in vitro bioactivities of polymeric micelles. Our results clearly demonstrated that dasatinib-encapsulated micelles offer considerable promise in the management of PVR.