Analysis of immediate stress mechanisms upon injection of polymeric micelles and related colloidal drug carriers: implications on drug targeting

Chitosan-functionalized bioplatforms and hydrogels in breast cancer: immunotherapy, phototherapy and clinical perspectives

Breast cancer is the most common and malignant tumor among women. Chitosan (CS)-based nanoparticles have been introduced into breast cancer therapy as a way to increase the targeted delivery of drugs and genes to the tumor site. CS nanostructures suppress tumorigenesis by enhancing both the targeted delivery of cargo (drug and gene) and its accumulation in tumor cells. The tumor cells internalize CS-based nanoparticles through endocytosis. Moreover, chitosan nanocarriers can also induce phototherapy-mediated tumor ablation. Smart and multifunctional types of CS nanoparticles, including pH-, light- and redox-responsive nanoparticles, can be used to improve the potential for breast cancer removal. In addition, the acceleration of immunotherapy by CS nanoparticles has also been achieved, and there is potential to develop CS-nanoparticle hydrogels that can be used to suppress tumorigenesis.

Luminescence Sensing of Biomacromolecules Heparin and Protamine in 100% Human Serum and Plasma by Supramolecular Polymeric Assemblies

Heparin, an anionic biomacromolecule, is routinely used as an anticoagulant during medical surgery to prevent blood clot formation and in the treatment of several heart, lung, and circulatory disorders having a higher risk of blood clotting. We herein report supramolecular polymeric nanoassemblies of cationic pyrene-tagged bis-imidazolium amphiphiles for heparin detection with high sensitivity and selectivity in aqueous buffer, plasma, and serum media. The nano-assemblies exhibited cyan-green excimeric emission in aqueous media, and their multivalent array of positive surface charges allowed them to form co-assemblies with heparin, resulting in significantly enhanced emission. This provided a convenient method for heparin detection in buffer at nanomolar concentrations, and most notably, a ratiometric fluorescence response was obtained even in highly competitive 100% human serum and 100% human plasma in a clinically relevant concentration range. Moreover, using the heparin-based luminescent co-assemblies, protamine sulfate, a clinically administered antidote to heparin, was also detected in 100% human serum and 100% human plasma at sub-micromolar concentrations.

Norbornene-Substituted Cationic Iridium(III) Complex and Water-Soluble Luminescent Polymers Based on It: Synthesis, Photophysical and Cytotoxic Properties

Abstract

A norbornene-substituted cationic iridium(III) complex containing 1-phenylisoquinoline cyclometalating ligands and an additional phenylimidazophenanthroline ligand was synthesized. On the base of this complex, water-soluble polymers were obtained by ring-opening metathesis polymerization (ROMP). The resulting polymers showed oxygen-dependent phosphorescence in the orange spectral region and high cytotoxicity against HCT116 cancer cells.

Simultaneous Probing of Metabolism and Oxygenation of Tumors In Vivo Using FLIM of NAD(P)H and PLIM of a New Polymeric Ir(III) Oxygen Sensor

Tumor cells are well adapted to grow in conditions of variable oxygen supply and hypoxia by switching between different metabolic pathways. However, the regulatory effect of oxygen on metabolism and its contribution to the metabolic heterogeneity of tumors have not been fully explored. In this study, we develop a methodology for the simultaneous analysis of cellular metabolic status, using the fluorescence lifetime imaging microscopy (FLIM) of metabolic cofactor NAD(P)H, and oxygen level, using the phosphorescence lifetime imaging (PLIM) of a new polymeric Ir(III)-based sensor (PIr3) in tumors in vivo. The sensor, derived from a polynorbornene and cyclometalated iridium(III) complex, exhibits the oxygen-dependent quenching of phosphorescence with a 40% longer lifetime in degassed compared to aerated solutions. In vitro, hypoxia resulted in a correlative increase in PIr3 phosphorescence lifetime and free (glycolytic) NAD(P)H fraction in cells. In vivo, mouse tumors demonstrated a high degree of cellular-level heterogeneity of both metabolic and oxygen states, and a lower dependence of metabolism on oxygen than cells in vitro. The small tumors were hypoxic, while the advanced tumors contained areas of normoxia and hypoxia, which was consistent with the pimonidazole assay and angiographic imaging. Dual FLIM/PLIM metabolic/oxygen imaging will be valuable in preclinical investigations into the effects of hypoxia on metabolic aspects of tumor progression and treatment response.

The in vivo fate of polymeric micelles

This review aims to provide a systemic analysis of the in vivo, as well as subcellular, fate of polymeric micelles (PMs), starting from the entry of PMs into the body. Few PMs are able to cross the biological barriers intact and reach the circulation. In the blood, PMs demonstrate fairly good stability mainly owing to formation of protein corona despite controversial results reported by different groups. Although the exterior hydrophilic shells render PMs "long-circulating", the biodistribution of PMs into the mononuclear phagocyte systems (MPS) is dominant as compared with non-MPS organs and tissues. Evidence emerges to support that the copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) is first broken down into pieces of PEG and PLA and then remnants to be eliminated from the body finally. At the cellular level, PMs tend to be internalized via endocytosis due to their particulate nature and disassembled and degraded within the cell. Recent findings on the effect of particle size, surface characteristics and shape are also reviewed. It is envisaged that unraveling the in vivo and subcellular fate sheds light on the performing mechanisms and gears up the clinical translation of PMs.

Biophysical Characterization of Interactions between Serum Albumin and Block Copolymer Micelles

Block copolymer micelles have demonstrated great promise in the solubilization of hydrophobic drugs, but an understanding of the blood stability of the drug-laden micelles is needed for therapeutic advancement of micelle technologies. Following intravenous administration, mPEG-CL and mPEG-LA micelles have demonstrated quick release of their cargo and disassembly in blood, but the prevailing mechanisms of micelle disruption and key biomacromolecules driving this disruption have yet to be elucidated. Although protein interactions with solid polymeric nanoparticles have been characterized, not much is known regarding protein interactions with dynamic block copolymer micelles. Herein, we characterize the interaction of bovine and human serum albumins (BSA and HSA) with polymeric micelles, mPEG-CL and mPEG-LA, using protein fluorescence, isothermal titration calorimetry (ITC), and circular dichroism (CD) spectroscopy. We find that BSA and HSA have interactions with mPEG-CL, while only HSA is observed to weakly interact with mPEG-LA. Protein fluorescence suggests that binding of HSA to mPEG-CL and mPEG-LA is driven by electrostatic interactions. ITC suggests an interaction between serum albumin and mPEG-CL block copolymers driven by hydrogen bonding and electrostatic interactions in physiological MOPS-buffered saline, while mPEG-LA has no measurable interaction with either of the serum albumins. CD spectroscopy demonstrates that the protein secondary structure is intact in both proteins in the presence of mPEG-CL and mPEG-LA. Overall, BSA is not always predictive of polymeric interactions with HSA. Understanding of interactions between serum proteins and block copolymer micelles and the exact mechanisms of destabilization will direct the rational design of block copolymer systems for improving blood stability.

Targeted antitumor comparison study between dopamine self-polymerization and traditional synthesis for nanoparticle surface modification in drug delivery

To improve the therapeutic efficacy of anticancer agents and extend their application, mussel-inspired chemical modifications have attracted considerable attention. Surface modification based on polydopamine (PDA) has been a facile and versatile method to immobilize biomolecules on substrates for targeted drug delivery. To better analyze pharmaceutical differences between PDA-based surface modification and traditional synthesis methods, we prepared two kinds of folate (FA)-targeted nanoparticles (NPs) loaded with paclitaxel (PTX). The resultant PTX-PDA-FA NPs and PTX-FA NPs represented PDA and synthesis strategies, respectively. PTX-PDA-FA NPs and PTX-FA NPs have been characterized. The particle size of PTX-PDA-FA NPs was smaller than that of PTX-FA NPs. The two kinds of NPs both exhibited long-rod morphology, good colloidal stability and sustained slow drug release. Cytotoxicityin vitrowas evaluated, and antitumor efficacy was investigated against 4T1 tumor-bearing mice. The tumor targeting therapeutic index of PTX-PDA-FA NPs and PTX-FA NPs showed equivalent superior specificity compared to nontargeted groups, which indicated that FA successfully attached to the surface of NPs by the PDA method and that the antitumor effect was equivalent to that of FA-modified NPs prepared by the chemical synthesis method. These results further indicated that PDA, as a simple and effective chemical surface modification platform, could be developed and applied in targeted delivery systems.

Toward understanding polymer micelle stability: Density ultracentrifugation offers insight into polymer micelle stability in human fluids

Micelles, as a class of drug delivery systems, are underrepresented among United States Food and Drug Administration approved drugs. A lack of clinical translation of these systems may be due to, in part, to a lack of understanding of micelle interactions with biologic fluids following injection. Despite the limited clinical translation, micelles remain an active area of research focus and pre-clinical development. The goal of the present study was to examine the stability of amphiphilic block copolymer micelles in biologic fluids to identify the properties and components of biologic fluids that influence micelle stability. Micelle stability, measured via Förster resonance energy transfer-based fluorescent spectrometry, was complemented with density ultracentrifugation to reveal the colocalized, or dissociated, state of the dye cargo after exposure to human biologic fluids. Polymeric micelles composed of poly(ethylene glycol-block-caprolactone) (mPEG-CL) and poly(ethylene glycol-block-lactide) (mPEG-LA) were unstable in fetal bovine serum, human serum and synovial fluid, with varying levels of instability observed in ascites and pleural fluid. All polymeric micelles exhibited stability in cerebrospinal fluid, highlighting the potential for local cerebro-spinal administration of micelles. Interestingly, mPEG2.2k-CL3.1k and mPEG2k-LA2.7k micelles favored dissolution whereas mPEG5.4k-LA28.5k micelles favored stability. Taken together, our data offers both quantitative and qualitative evidence for micelle stability within human biologic fluids and offers evidence of polymer micelle instability in biologic fluids that is not explained by either total protein content or total unsaturated lipid content. The results help to identify potential sites for local delivery where stability is maintained.

Recent Advances in Chitosan-Based Carriers for Gene Delivery

Approximately 4000 diseases are associated with malfunctioning genes in a particular cell type. Gene-based therapy provides a platform to modify the disease-causing genes expression at the cellular level to treat pathological conditions. However, gene delivery is challenging as these therapeutic genes need to overcome several physiological and intracellular barriers in order, to reach the target cells. Over the years, efforts have been dedicated to develop efficient gene delivery vectors to overcome these systemic barriers. Chitosan, a versatile polysaccharide, is an attractive non-viral vector material for gene delivery mainly due to its cationic nature, biodegradability and biocompatibility. The present review discusses the design factors that are critical for efficient gene delivery/transfection and highlights the recent progress of gene therapy using chitosan-based carriers.

Recent Advances in Drug Delivery System for Bioactive Glycosides from Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) has been used in China for thousands of years for the prevention and treatment of various diseases. The materials that exert a therapeutic effect are called the active ingredients. The bioactive glycosides are important active ingredients from TCM that can make significant contributions to treating diseases. Because of the possibilities of various clinical applications, the properties and administration of these bioactive glycosides deserve further investigation. Their promising treatment effects, however, are hindered by their poor solubility, poor stability and rapid elimination. Therefore, it is necessary that we improve the therapeutic efficacy of bioactive glycosides by overcoming these problems. Meanwhile, some practical design strategies and novel drug delivery vehicles based on drug delivery systems provide favorable support in clinical practice for these active ingredients. This review summarizes diverse pharmacological activities of bioactive glycosides and focuses on recent advances in delivery system for these active constitutes; in particular, some glycol glycosides can effectively cure intractable diseases through targeted drug delivery. This review elucidates some design strategies for drug delivery system that are mainly based on two methods (avoiding physical barriers by changing dosage forms and enhancing the ability to bind to receptors or proteins after administration) and indicate the current challenges during the combination of delivery vehicles and these glycosides in hopes of promoting the process of receiving ideal therapeutic efficacy of them in future studies.

Ratiometric delivery of two therapeutic candidates with inherently dissimilar physicochemical property through pH-sensitive core-shell nanoparticles targeting the heterogeneous tumor cells of glioma

Currently, combination drug therapy is one of the most effective approaches to glioma treatment. However, due to the inherent dissimilar pharmacokinetics of individual drugs and blood brain barriers, it was difficult for the concomitant drugs to simultaneously be delivered to glioma in an optimal dose ratio manner. Herein, a cationic micellar core (Cur-M) was first prepared from d-α-tocopherol-grafted-ε-polylysine polymer to encapsulate the hydrophobic curcumin, followed by dopamine-modified-poly-γ-glutamic acid polymer further deposited on its surface as a anion shell through pH-sensitive linkage to encapsulate the hydrophilic doxorubicin (DOX) hydrochloride. By controlling the combinational Cur/DOX molar ratio at 3:1, a pH-sensitive core-shell nanoparticle (PDCP-NP) was constructed to simultaneously target the cancer stem cells (CSCs) and the differentiated tumor cells. PDCP-NP exhibited a dynamic diameter of 160.8 nm and a zeta-potential of -30.5 mV, while its core-shell structure was further confirmed by XPS and TEM. The ratiometric delivery capability of PDCP-NP was confirmed by in vitro and in vivo studies, in comparison with the cocktail Cur/DOX solution. Meanwhile, the percentage of CSCs in tumors was significantly decreased from 4.16% to 0.95% after treatment with PDCP-NP. Overall, PDCP-NP may be a promising carrier for the combination therapy with drug candidates having dissimilar physicochemical properties.

Plasma protein adsorption and biological identity of systemically administered nanoparticles

Although a variety of nanoparticles (NPs) have been used for drug delivery applications, their surfaces are immediately covered by plasma protein corona upon systemic administration. As a result, the adsorbed proteins create a unique biological identity of the NPs that lead to unpredictable performance. The protein corona on NPs could also impede active targeting, induce off-target effects, trigger particle clearance and even provoke toxicity. This article reviews the fundamentals of NP–plasma protein interaction, the consequences of the interactions, and provides insights into the correlations of protein corona with biodistribution and cellular delivery. We hope that this review will trigger additional questions and possible solutions that lead to more favorable developments in NP-based targeted delivery systems.

Pyrene-based heparin sensors in competitive aqueous media – the role of self-assembled multivalency (SAMul)

Simple functionalised pyrene derivatives can achieve ratiometric sensing of heparin with the precise sensing mechanism depending on whether the sensor self-assembles into a multivalent ligand display.

Micellar carriers for the delivery of multiple therapeutic agents

Multi-drug therapy is described as a simultaneous or sequential administration of two or more drugs with similar or different mechanisms of action and is recognized as a more efficient solution to combat successfully, various ailments. Polymeric micelles (PMs) are self-assemblies of block copolymers providing numerous opportunities for drug delivery. To date various micellar formulations were studied for delivery of drugs, nutraceuticals and genes; a few of them are in clinical trials. It was observed that there is an immense need for the development of PMs embedding multiple therapeutic agents to combat various ailments, including cancers, HIV/AIDS, malaria, multiple sclerosis, hypertension, infectious diseases, cardiovascular and metabolic diseases, immune disorders and many psychiatric disorders. Several combinations of drug-drug, drug-nutraceutical, drug-gene and drug-siRNA explored to date are detailed in this review, with a special emphasis on their potential and future perspectives. A summary of various preparation methods, characterization techniques and applications of PMs are also provided. This review presents a holistic approach on multi-drug delivery using micellar carriers and emphasizes on the development of therapeutic hybrids embedding novel combinations for safer and effective therapy.

Micellar structures in nanoparticle-multiblock copolymer complexes

Brownian dynamics simulation is employed to examine the structure changes of complexes composed of a hydrophobic nanoparticle and a multiblock copolymer molecule (MCP). The dependence of the structure transitions on the radius of the nanoparticle, on the interactions between the hydrophobic segments of the MCP, and on the interactions between the hydrophobic segments and hydrophobic nanoparticle is examined. It is shown that the multiblock copolymer adsorbed on a nanoparticle can acquire the structure of a micelle.To better characterize the micelle generated and the structure changes in the nanoparticle-MCP complex, the mass dipole moment of the complex [the distance between the center of mass of MCP and the center of the nanoparticle minus the radius of the nanoparticle (DCC)], the density profiles of MCP segments around its center of mass and around the nanoparticle, the radius of gyration of the MCP, and the thickness of the micelle around the nanoparticle are determined. It was found that, when structural transition of the complex occurs, the above quantities change dramatically. The present simulation may provide new insights regarding the drug-loaded micelle interacting with a virus represented by a nanoparticle.

Peptide-directed self-assembly of functionalized polymeric nanoparticles part I: design and self-assembly of peptide-copolymer conjugates into nanoparticle fibers and 3D scaffolds

A robust self-assembly of nanoparticles into fibers and 3D scaffolds is designed and fabricated by functionalizing a RAFT-polymerized amphiphilic triblock copolymer with designer ionic complementary peptides so that the assembled core-shell polymeric nanoparticles are directed by peptide assembly into continuous "nanoparticle fibers," ultimately leading to 3D fiber scaffolds. The assembled nanostructure is confirmed by FESEM and optical microscopy. The assembly is not hindered when a protein (insulin) is incorporated within the nanoparticles as an active ingredient. MTS cytotoxicity tests on SW-620 cell lines show that the peptides, copolymers, and peptide-copolymer conjugates are biocompatible. The methodology of self-assembled nanoparticle fibers and 3D scaffolds is intended to combine the advantages of a flexible hydrogel scaffold with the versatility of controlled release nanoparticles to offer unprecedented ability to incorporate desired drug(s) within a self-assembled scaffold system with individual control over the release of each drug.

Chitosan nanoparticles for siRNA delivery: optimizing formulation to increase stability and efficiency

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii) stability in biological media including blood. Therefore, the influence of chitosan/tripolyphosphate ratio, chitosan physicochemical properties, PEGylation of chitosan as well as the addition of an endosomal disrupting agent and a negatively charged polymer was assessed. The gene silencing activity and cytotoxicity were evaluated on B16 melanoma cells expressing luciferase. We monitored the integrity and the size behavior of siRNA nanoparticles in human plasma using fluorescence fluctuation spectroscopy and single particle tracking respectively. The presence of PEGylated chitosan and poly(ethylene imine) was essential for high levels of gene silencing in vitro. Chitosan nanoparticles immediately released siRNA in plasma while the inclusion of hyaluronic acid and high amount of poly(ethylene glycol) in the formulation improved the stability of the particles. The developed formulations of PEGylated chitosan-based nanoparticles that achieve high gene silencing in vitro, low cytotoxicity and high stability in plasma could be promising for intravenous delivery of siRNA.

Endolytic, pH-responsive HPMA-b-(L-Glu) copolymers synthesized via sequential aqueous RAFT and ring-opening polymerizations

A facile synthetic pathway for preparing block copolymers with pH-responsive L-glutamic acid segments for membrane disruption is reported. Aqueous reversible addition-fragmentation chain transfer (aRAFT) polymerization was first used to prepare biocompatible, nonimmunogenic poly[N-(2-hydroxypropyl)methacrylamide]. This macro chain transfer agent (CTA) was then converted into a macroinitiator via simultaneous aminolysis and thiol-ene Michael addition using the primary amine substituted N-(3-aminopropyl)methacrylamide. This macroinitiator was subsequently utilized in the ring-opening polymerization of the N-carboxyanhydride monomer of γ-benzyl-L-glutamate. After deprotection, the pH-dependent coil-to-helix transformations of the resulting HPMA-b-(L-Glu) copolymers were monitored via circular dichroism spectroscopy. HPMA segments confer water solubility and biocompatibility while the L-glutamic acid repeats provide reversible coil-to-helix transitions at endosomal pH values (~5-6). The endolytic properties of these novel [HPMA-b-(L-Glu)] copolymers and their potential as modular components in drug carrier constructs was demonstrated utilizing red blood cell hemolysis and fluorescein release from POPC vesicles.

Chitosan-based siRNA delivery systems

Recently, chitosan has attracted significant attention in the formulation of small interfering RNA (siRNA). Because of its cationic nature, chitosan can easily complex siRNA, thus readily forming nanoparticles. Moreover, chitosan is biocompatible and biodegradable, which make it a good candidate for siRNA delivery in vivo. However, chitosan requires further development to achieve high efficiency. This review will describe the major barriers that impair the efficiency of the chitosan-based siRNA delivery systems, including the stability of the delivery system in biological fluids and endosomal escape. Several solutions to counteract these barriers have been developed and will be discussed. The parameters to consider for designing powerful delivery systems will be described, particularly the possibilities for grafting targeting ligands. Finally, optimized systems that allow in vivo therapeutic applications for both local and systemic delivery will be reviewed. This review will present recent improvements in chitosan-based siRNA delivery systems that overcome many of these system's previous pitfalls and pave the way to a new generation of siRNA delivery systems.

Polymeric micelles for multidrug delivery and combination therapy

The use of conventional therapy based on a single therapeutic agent is not optimal to treat human diseases. The concept called "combination therapy", based on simultaneous administration of multiple therapeutics is recognized as a more efficient solution. Interestingly, this concept has been in use since ancient times in traditional herbal remedies with drug combinations, despite mechanisms of these therapeutics not fully comprehended by scientists. This idea has been recently re-enacted in modern scenarios with the introduction of polymeric micelles loaded with several drugs as multidrug nanocarriers. This Concept article presents current research and developments on the application of polymeric micelles for multidrug delivery and combination therapy. The principles of micelle formation, their structure, and the developments and concept of multidrug delivery are introduced, followed by discussion on recent advances of multidrug delivery concepts directed towards targeted drug delivery and cancer, gene, and RNA therapies. The advantages of various polymeric micelles designed for different applications, and new developments combined with diagnostics and imaging are elucidated. A compilation work from our group based on multidrug-loaded micelles as carriers in drug-releasing implants for local delivery systems based on titania nanotubes is summarized. Finally, an overview of recent developments and prospective outlook for future trends in this field is given.

Drug-initiated ring-opening polymerization of O-carboxyanhydrides for the preparation of anticancer drug-poly(O-carboxyanhydride) nanoconjugates

We report a novel synthetic strategy of polymer-drug conjugates for nanoparticulate drug delivery: hydroxyl-containing drug (e.g., camptothecin, paclitaxel, doxorubicin and docetaxel) can initiate controlled polymerization of phenyl O-carboxyanhydride (Phe-OCA) to afford drug-poly(Phe-OCA) conjugated nanoparticles, termed drug-PheLA nanoconjugates (NCs). Our new NCs have well-controlled physicochemical properties, including high drug loading, quantitative drug loading efficiency, controlled particle size with narrow particle size distribution, and sustained drug release profile over days without "burst" release effect as observed in conventional polymer/drug encapsulates. Compared with polylactide NCs, the PheLA NCs have increased noncovalent hydrophobic interchain interactions and thereby result in remarkable stability in human serum with negligible particle aggregation. Such distinctive properties can reduce the premature disassembly of NCs upon dilution in the bloodstream and prolong NCs' in vivo circulation with the enhancement of intratumoral accumulation of NCs, which has a bearing on therapeutic effectiveness.