Syntheses of click PEG-dexamethasone conjugates for the treatment of rheumatoid arthritis

PEGylation Improves the Therapeutic Index of Dexamethasone To Treat Acute Respiratory Distress Syndrome with Obesity Background in Mouse

With increasing prevalence globally, obesity presents unique challenges to the clinical management of other diseases. In the case of acute respiratory distress syndrome (ARDS), glucocorticoid therapy (e.g., dexamethasone (DEX)) represents one of the few pharmacological treatment options, but it comes with severe adverse effects, especially when long-term usage (>1 week) is required. One important reason for the adverse effects of DEX is its nonspecific accumulation in healthy tissues upon systemic administration. Therefore, we hypothesize that refining its pharmacokinetics (PK) and in vivo biodistribution may improve its therapeutic index (higher efficacy, lower toxicity) and thus make it safer for obese populations. To achieve this goal, DEX was conjugated with polyethylene glycol (PEG) with three different molecular weights (Mw, 2K, 5K, and 10K) via a reactive oxygen species (ROS)-cleavable linker. Their anti-inflammatory efficacy and long-term adverse effects were evaluated in a murine obesity-ARDS model. Strikingly, DEX-PEG-2K (conjugates with 2K PEG Mw) provided the optimal therapeutic index compared to free DEX and to the other two conjugates with longer PEGs (Mw of 5K and 10K): While retaining the comparable therapeutic efficacy to DEX, DEX-PEG-2K significantly reduced the accumulation of free DEX in the liver and spleen, which led to a 51% reduction of fatty area in liver and a 32% reduction of blood triglycerides concentration. DEX-induced apoptosis of the thymus was also rescued by DEX-PEG-2K under normal conditions. The PK and biodistribution were also investigated to elicit the underlying mechanism. In summary, we provided here a chemical modification strategy to improve the therapeutic index of dexamethasone and possibly other glucocorticoid drugs for ARDS treatment with an obesity background.

Recent Progress in Microenvironment-Responsive Nanodrug Delivery Systems for the Targeted Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that often causes joint pain, swelling, and functional impairments. Drug therapy is the main strategy used to alleviate the symptoms of RA; however, drug therapy may have several adverse effects, such as nausea, vomiting, abdominal pain, diarrhea, gastric ulcers, intestinal bleeding, hypertension, hyperglycemia, infection, fatigue, and indigestion. Moreover, long-term excessive use of drugs may cause liver and kidney dysfunction, as well as thrombocytopenia. Nanodrug delivery systems (NDDSs) can deliver therapeutics to diseased sites with the controlled release of the payload in an abnormal microenvironment, which helps to reduce the side effects of the therapeutics. Abnormalities in the microenvironment, such as a decreased pH, increased expression of matrix metalloproteinases (MMPs), and increased concentrations of reactive oxygen species (ROS), are associated with the progression of RA but also provide an opportunity to achieve microenvironment-responsive therapeutic release at the RA site. Microenvironment-responsive NDDSs may overcome the abovementioned disadvantages of RA therapy. Herein, we comprehensively review recent progress in the development of microenvironment-responsive NDDSs for RA treatment, including pH-, ROS-, MMP-, and multiresponsive NDDSs. Furthermore, the pathological microenvironment is highlighted in detail.

Acid-sensitive prodrugs; a promising approach for site-specific and targeted drug release

Drugs administered through conventional formulations are devoid of targeting and often spread to various undesired sites, leading to sub-lethal concentrations at the site of action and the emergence of undesired effects. Hence, therapeutic agents should be delivered in a controlled manner at target sites. Currently, stimuli-based drug delivery systems have demonstrated a remarkable potential for the site-specific delivery of therapeutic moieties. pH is one of the widely exploited stimuli for drug delivery as several pathogenic conditions such as tumor cells, infectious and inflammatory sites are characterized by a low pH environment. This review article aims to demonstrate various strategies employed in the design of acid-sensitive prodrugs, providing an overview of commercially available acid-sensitive prodrugs. Furthermore, we have compiled the progress made for the development of new acid-sensitive prodrugs currently undergoing clinical trials. These prodrugs include albumin-binding prodrugs (Aldoxorubicin and DK049), polymeric micelle (NC-6300), polymer conjugates (ProLindac™), and an immunoconjugate (IMMU-110). The article encompasses a broad spectrum of studies focused on the development of acid-sensitive prodrugs for anticancer, antibacterial, and anti-inflammatory agents. Finally, the challenges associated with the acid-sensitive prodrug strategy are discussed, along with future directions.

Glucocorticoids-based prodrug design: Current strategies and research progress

Attributing to their broad pharmacological effects encompassing anti-inflammation, antitoxin, and immunosuppression, glucocorticoids (GCs) are extensively utilized in the clinic for the treatment of diverse diseases such as lupus erythematosus, nephritis, arthritis, ulcerative colitis, asthma, keratitis, macular edema, and leukemia. However, long-term use often causes undesirable side effects, including metabolic disorders-induced Cushing's syndrome (buffalo back, full moon face, hyperglycemia, etc.), osteoporosis, aggravated infection, psychosis, glaucoma, and cataract. These notorious side effects seriously compromise patients' quality of life, especially in patients with chronic diseases. Therefore, glucocorticoid-based advanced drug delivery systems for reducing adverse effects have received extensive attention. Among them, prodrugs have the advantages of low investment, low risk, and high success rate, making them a promising strategy. In this review, we propose the strategies for the design and summarize current research progress of glucocorticoid-based prodrugs in recent decades, including polymer-based prodrugs, dendrimer-based prodrugs, antibody-drug conjugates, peptide-drug conjugates, carbohydrate-based prodrugs, aliphatic acid-based prodrugs and so on. Besides, we also raise issues that need to be focused on during the development of glucocorticoid-based prodrugs. This review is expected to be helpful for the research and development of novel GCs and prodrugs.

Peptide targeting improves the delivery and therapeutic index of glucocorticoids to treat rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by excessive inflammation in the joints. Glucocorticoid drugs are used clinically to manage RA symptoms, while their dosage and duration need to be tightly controlled due to severe adverse effects. Using dexamethasone (DEX) as a model drug, we explored here whether peptide-guided delivery could increase the safety and therapeutic index of glucocorticoids for RA treatment. Using multiple murine RA models such as collagen-induced arthritis (CIA), we found that CRV, a macrophage-targeting peptide, can selectively home to the inflammatory synovium of RA joints upon intravenous injection. The expression of the CRV receptor, retinoid X receptor beta (RXRB), was also elevated in the inflammatory synovium, likely being the basis of CRV targeting. CRV-conjugated DEX increased the accumulation of DEX in the inflamed synovium but not in healthy organs of CIA mice. Therefore, CRV-DEX demonstrated a stronger efficacy to suppress synovial inflammation and alleviate cartilage/bone destruction. Meanwhile, CRV conjugation reduced immune-related adverse effects of DEX even after a long-term use. Last, we found that RXRB expression was significantly elevated in human patient samples, demonstrating the potential of clinical translation. Taken together, we provide a novel, peptide-targeted strategy to improve the therapeutic efficacy and safety of glucocorticoids for RA treatment.

Instructive cartilage regeneration modalities with advanced therapeutic implantations under abnormal conditions

The development of interdisciplinary biomedical engineering brings significant breakthroughs to the field of cartilage regeneration. However, cartilage defects are considerably more complicated in clinical conditions, especially when injuries occur at specific sites (e.g., osteochondral tissue, growth plate, and weight-bearing area) or under inflammatory microenvironments (e.g., osteoarthritis and rheumatoid arthritis). Therapeutic implantations, including advanced scaffolds, developed growth factors, and various cells alone or in combination currently used to treat cartilage lesions, address cartilage regeneration under abnormal conditions. This review summarizes the strategies for cartilage regeneration at particular sites and pathological microenvironment regulation and discusses the challenges and opportunities for clinical transformation.

The mode of dexamethasone decoration influences avidin-nucleic-acid-nano-assembly organ biodistribution and in vivo drug persistence

Avidin-Nucleic-Acid-NanoASsemblies (ANANAS) possess natural tropism for the liver and, when loaded with dexamethasone, reduce clinical progression in an autoimmune hepatitis murine model. Here, we investigated the linker chemistry (hydrazide-hydrazone, Hz-Hz, or carbamate hydrazide-hydrazone, Cb-Hz bond) and length (long, 5 kDa PEG, or short, 5-6 carbons) in biotin-dexamethasone conjugates used for nanoparticle decoration through in vitro and in vivo studies. All four newly synthesized conjugates released the drug at acidic pH only. In vitro, the Hz-Hz and the PEG derivatives were less stable than the Cb-Hz and the short chain ones, respectively. Once injected in healthy mice, dexamethasone location in the PEGylated ANANAS outer layer favors liver penetration and resident macrophages uptake, while drug Hz-Hz, but not Cb-Hz, short spacing prolongs drug availability. In conclusion, the tight modulation of ANANAS decoration can significantly influence the host interaction, paving the way for the development of steroid nanoformulations suitable for different pharmacokinetic profiles.

Synthesis of Photo, Oxidative, and Reductive Triple-Stimuli-Responsive Block Copolymer Micelles as Nanocarriers for Controlled Release

With the rapid development of nanotechnology, stimuli-responsive nanomaterials have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. The environment of the human body is complex and cancer cells proliferate rapidly; the traditional nanocarriers could not release the loaded drugs sufficiently, and the release level of the drug is not sufficient for the requirement of treatment. Herein, a photoresponsive, glutathione, and reactive oxygen species block copolymer mPEG_2k-ONB-SS-PO-mPEG_2k is prepared by Cu(I)-catalyzed azide-alkyne cycloaddition click polymerization. The ο-nitrobenzyl groups, peroxalate ester bonds, disulfide bonds, and triazole units are regularly and repeatedly arranged in hydrophobic blocks. The photo, oxidative, and reductive responsive characteristics of the copolymers in different conditions were investigated by ultraviolet and visible spectrophotometry, dynamic light scattering, and transmission electron microscopy. Nile Red is encapsulated into the core of micelles as a model drug and exhibits the drug release behaviors in various environments. This research provides a way to design potential drug carriers and a promising platform for efficient intracellular drug delivery in cancer therapy.

Pharmacokinetics of Pullulan-Dexamethasone Conjugates in Retinal Drug Delivery

The treatment of retinal diseases by intravitreal injections requires frequent administration unless drug delivery systems with long retention and controlled release are used. In this work, we focused on pullulan (≈67 kDa) conjugates of dexamethasone as therapeutic systems for intravitreal administration. The pullulan-dexamethasone conjugates self-assemble into negatively charged nanoparticles (average size 326 ± 29 nm). Intravitreal injections of pullulan and pullulan-dexamethasone were safe in mouse, rat and rabbit eyes. Fluorescently labeled pullulan particles showed prolonged retention in the vitreous and they were almost completely eliminated via aqueous humor outflow. Pullulan conjugates also distributed to the retina via Müller glial cells when tested in ex vivo retina explants and in vivo. Pharmacokinetic simulations showed that pullulan-dexamethasone conjugates may release free and active dexamethasone in the vitreous humor for over 16 days, even though a large fraction of dexamethasone may be eliminated from the eye as bound pullulan-dexamethasone. We conclude that pullulan based drug conjugates are promising intravitreal drug delivery systems as they may reduce injection frequency and deliver drugs into the retinal cells.

Glutathione Reductase-Sensitive Polymeric Micelles for Controlled Drug Delivery on Arthritic Diseases

Inflammation plays an essential role in arthritis development and progression. Despite the advances in the pharmaceutical field, current treatments still present low efficacy and severe side effects. Considering the high activity of the glutathione reductase (GR) enzyme in inflamed joints, a distinctive drug delivery system sensitive to the GR enzyme was designed for efficient drug delivery on arthritic diseases. A linear amphiphilic polymer composed of methoxypolyethylene glycol amine-glutathione-palmitic acid (mPEG-GSH_n-PA) was synthesized and the intermolecular oxidation of the thiol groups from GSHs retain the drug inside the resulting micelles. Stable polymeric micelles of 100 nm of size presented a loading capacity of dexamethasone (Dex) up to 65%. Although in physiological conditions the Dex release presented slow and sustained kinetics, in the presence of the GR enzyme, there was a burst release (stimuli-responsive properties). Biological assays demonstrated their cytocompatibility in contact with human articular chondrocytes, macrophages, and endothelial cells as well as their hemocompatibility. Importantly, in an in vitro model of inflammation, the polymeric micelles promoted a controlled drug release in the presence of GR, exhibiting a higher efficacy than the free Dex while reducing the negative effects of the drug into normal cells. In conclusion, this formulation is a promising approach to treat arthritic diseases and other inflammatory conditions.

Pullulan Based Bioconjugates for Ocular Dexamethasone Delivery

Posterior segment eye diseases are mostly related to retinal pathologies that require pharmacological treatments by invasive intravitreal injections. Reduction of frequent intravitreal administrations may be accomplished with delivery systems that provide sustained drug release. Pullulan-dexamethasone conjugates were developed to achieve prolonged intravitreal drug release. Accordingly, dexamethasone was conjugated to ~67 kDa pullulan through hydrazone bond, which was previously found to be slowly cleavable in the vitreous. Dynamic light scattering and transmission electron microscopy showed that the pullulan-dexamethasone containing 1:20 drug/glucose unit molar ratio (10% w/w dexamethasone) self-assembled into nanoparticles of 461 ± 30 nm and 402 ± 66 nm, respectively. The particles were fairly stable over 6 weeks in physiological buffer at 4, 25 and 37 °C, while in homogenized vitreous at 37 °C, the colloidal assemblies underwent size increase over time. The drug was released slowly in the vitreous and rapidly at pH 5.0 mimicking lysosomal conditions: 50% of the drug was released in about 2 weeks in the vitreous, and in 2 days at pH 5.0. In vitro studies with retinal pigment epithelial cell line (ARPE-19) showed no toxicity of the conjugates in the cells. Flow cytometry and confocal microscopy showed cellular association of the nanoparticles and intracellular endosomal localization. Overall, pullulan conjugates showed interesting features that may enable their successful use in intravitreal drug delivery.

Inflammation-responsive delivery systems for the treatment of chronic inflammatory diseases

Inflammation is the biological response of immune system to protect living organisms from injurious factors. However, excessive and uncontrolled inflammation is implicated in a variety of devastating chronic diseases including atherosclerosis, inflammatory bowel disease (IBD), and rheumatoid arthritis (RA). Improved understanding of inflammatory response has unveiled a rich assortment of anti-inflammatory therapeutics for the treatment and management of relevant chronic diseases. Notwithstanding these successes, clinical outcomes are variable among patients and serious adverse effects are often observed. Moreover, there exist some limitations for clinical anti-inflammatory therapeutics such as aqueous insolubility, low bioavailability, off-target effects, and poor accessibility to subcellular compartments. To address these challenges, the rational design of inflammation-specific drug delivery systems (DDSs) holds significant promise. Moreover, as compared to normal tissues, inflamed tissue-associated pathological milieu (e.g., oxidative stress, acidic pH, and overexpressed enzymes) provides vital biochemical stimuli for triggered delivery of anti-inflammatory agents in a spatiotemporally controlled manner. In this review, we summarize recent advances in the development of anti-inflammatory DDSs with built-in pathological inflammation-specific responsiveness for the treatment of chronic inflammatory diseases.

Dexamethasone Conjugates: Synthetic Approaches and Medical Prospects

Dexamethasone (DEX) is the most commonly prescribed glucocorticoid (GC) and has a wide spectrum of pharmacological activity. However, steroid drugs like DEX can have severe side effects on non-target organs. One strategy to reduce these side effects is to develop targeted systems with the controlled release by conjugation to polymeric carriers. This review describes the methods available for the synthesis of DEX conjugates (carbodiimide chemistry, solid-phase synthesis, reversible addition fragmentation-chain transfer [RAFT] polymerization, click reactions, and 2-iminothiolane chemistry) and perspectives for their medical application as GC drug or gene delivery systems for anti-tumor therapy. Additionally, the review focuses on the development of DEX conjugates with different physical-chemical properties as successful delivery systems in the target organs such as eye, joint, kidney, and others. Finally, polymer conjugates with improved transfection activity in which DEX is used as a vector for gene delivery in the cell nucleus have been described.

Treatment of Rheumatoid Arthritis by Serum Albumin Nanoparticles Coated with Mannose to Target Neutrophils

Rheumatoid arthritis (RA) is an angiogenic and chronic inflammatory disease. One of the most extensively used first-line drugs against RA is methotrexate (MTX), but it shows poor solubility, short in vivo circulation, and off-target binding, leading to strong toxicity. To overcome these shortcomings, the present study loaded MTX into nanoparticles of human serum albumin modified with mannose (MTX-M-NPs) to target the drug to neutrophils. MTX-M-NPs were prepared, and their uptake by neutrophils was studied using laser confocal microscopy and flow cytometry. A chick chorioallantoic membrane assay was used to assess their ability to inhibit angiogenesis. The pharmacokinetics and tissue distribution of MTX-M-NPs were investigated using fluorescence microscopy and high-performance liquid chromatography. Their pharmacodynamics was evaluated in a rat model with arthritis induced by collagen. Neutrophils took up MTX-M-NPs significantly better than the same nanoparticles (NPs) without mannose. MTX-M-NPs markedly suppressed angiogenesis in chick embryos, and the MTX circulation was significantly longer when it was delivered as MTX-M-NPs than as a free drug. MTX-M-NPs accumulated mainly in arthritic joints. The retention of NPs was promoted by mannose-derived coating in arthritic joints. Serum levels of inflammatory cytokines, joint swelling, and bone erosion were significantly decreased by MTX-M-NPs. In conclusion, these NPs can prolong the in vivo circulation of MTX and target it to the sites of inflammation in RA, reducing drug toxicity. MTX-M-NPs allow the drug to exert its intrinsic anti-inflammatory, antiangiogenic, and analgesic properties, making it a useful drug delivery system in RA.

Polymer nanomedicines

Polymer nanomedicines (macromolecular therapeutics, polymer-drug conjugates, drug-free macromolecular therapeutics) are a group of biologically active compounds that are characterized by their large molecular weight. This review focuses on bioconjugates of water-soluble macromolecules with low molecular weight drugs and selected proteins. After analyzing the design principles, different structures of polymer carriers are discussed followed by the examination of the efficacy of the conjugates in animal models and challenges for their translation into the clinic. Two innovative directions in macromolecular therapeutics that depend on receptor crosslinking are highlighted: a) Combination chemotherapy of backbone degradable polymer-drug conjugates with immune checkpoint blockade by multivalent polymer peptide antagonists; and b) Drug-free macromolecular therapeutics, a new paradigm in drug delivery.

Nanomedicine for the Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that results in severe inflammatory microenvironments in the joint tissues. In clinics, disease-modifying antirheumatic drugs (DMARDs) are generally prescribed to patients with RA, but their long-term use often shows toxicity in some organs such as the gastrointestinal system, skin, and kidneys and immunosuppression-mediated infection. Nanomedicine has emerged as a new therapeutic strategy to efficiently localize the drugs in inflamed joints for the treatment of RA. In this Review, we introduce recent research in the area of nanomedicine for the treatment of RA and discuss how the nanomedicine can be used to deliver therapeutic agents to the inflamed joints and manage the progression of RA, particularly focusing on targeted delivery, controlled drug release, and immune modulation.

Nanomedicines for the delivery of glucocorticoids and nucleic acids as potential alternatives in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects 0.5-1% of the world population. Current treatments include on one hand non-steroidal anti-inflammatory drugs and glucocorticoids (GCs) for treating pain and on the other hand disease-modifying anti-rheumatic drugs such as methotrexate, Janus kinase inhibitors or biologics such as antibodies targeting mainly cytokine expression. More recently, nucleic acids such as siRNA, miRNA, or anti-miRNA have shown strong potentialities for the treatment of RA. This review discusses the way nanomedicines can target GCs and nucleic acids to inflammatory sites, increase drug penetration within inflammatory cells, achieve better subcellular distribution and finally protect drugs against degradation. For GCs such a targeting effect would allow the treatment to be more effective at lower doses and to reduce the administration frequency as well as to induce much fewer side-effects. In the case of nucleic acids, particularly siRNA, knocking down proteins involved in RA, could importantly be facilitated using nanomedicines. Finally, the combination of both siRNA and GCs in the same carrier allowed for the same cell to target both the GCs receptor as well as any other signaling pathway involved in RA. Nanomedicines appear to be very promising for the delivery of conventional and novel drugs in RA therapeutics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Recent Advances in Nanotheranostics for Treat-to-Target of Rheumatoid Arthritis

Early diagnosis, standardized treatment, and regular monitoring are the clinical treatment principle of rheumatoid arthritis (RA). The overarching principles and recommendations of treat-to-target (T2T) in RA advocate remission as the optimum aim, especially for patients with very early disease who are initiating therapy with anti-RA medications. However, traditional anti-RA drugs cannot selectively target the inflammatory areas and may cause serious side effects due to its short biological half-life and poor bioavailability. These limitations have significantly driven the research and application of nanomaterial-based drugs in theranostics of RA. Nanomedicines have appropriate sizes and easily modified surfaces which can enhance their biological compatibility and prolong circulation time of drug-loading systems in vivo. Traditional T2T regimens cannot evaluate the efficacy of drugs in real time, while clinical drug nanosizing can realize the integration of diagnosis and treatment of RA. This review bridges clinically proposed T2T concepts and nanomedicine in an integrated system for RA early-stage diagnosis and treatment. The most advanced progress in various nanodrug delivery systems for theranostics of RA is summarized, establishing a clear path and a new perspective for further optimization of T2T. Finally, the key facing challenges are discussed and prospects are addressed.

Stimuli-responsive Drug Delivery Systems as an Emerging Platform for Treatment of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a systemic autoimmune disease accompanied by chronic inflammation. Due to the long-term infiltration in inflammatory sites, joints get steadily deteriorated, eventually resulting in functional incapacitation and disability. Despite the considerable effect, RA sufferers treated with current drug therapeutic efficacy are exposed to severe side effects. Application of Drug Delivery Systems (DDS) has improved these situations while the problem of limited drug exposure remains untackled. Stimuli-responsive DDS that are responsive to a variety of endogenous and exogenous stimuli, such as pH, redox status, and temperature, have emerged as a promising therapeutic strategy to optimize the drug release. Herein, we discussed the therapeutic regimes and serious side effects of current RA therapy, as well as focused on some of the potential stimuliresponsive DDS utilized in RA therapy. Besides, the prospective room in designing DDS for RA treatment has also been discussed.

Controlling protein interactions in blood for effective liver immunosuppressive therapy by silica nanocapsules

Immunosuppression with glucocorticoids is a common treatment for autoimmune liver diseases and after liver transplant, which is however associated with severe side-effects. Targeted delivery of glucocorticoids to inflammatory cells, e.g. liver macrophages and Kupffer cells, is a promising approach for minimizing side effects. Herein, we prepare core-shell silica nanocapsules (SiO₂ NCs) via a sol-gel process confined in nanodroplets for targeted delivery of dexamethasone (DXM) for liver immunosuppressive therapy. DXM with concentrations up to 100 mg mL^-1 in olive oil are encapsulated while encapsulation efficiency remains over 95% after 15 days. Internalization of NCs by non-parenchymal murine liver cells significantly reduces the release of inflammatory cytokines, indicating an effective suppression of inflammatory response of liver macrophages. Fluorescent and magnetic labeling of the NCs allows for monitoring their intracellular trafficking and biodegradation. Controlled interaction with blood proteins and good colloidal stability in blood plasma are achieved via PEGylation of the NCs. Specific proteins responsible for stealth effect, such as apolipoprotein A-I, apolipoprotein A-IV, and clusterin, are present in large amounts on the PEGylated NCs. In vivo biodistribution investigations prove an efficient accumulation of NCs in the liver, underlining the suitability of the SiO₂ NCs as a dexamethasone carrier for treating inflammatory liver diseases.

Injectable Click-Crosslinked Hyaluronic Acid Depot To Prolong Therapeutic Activity in Articular Joints Affected by Rheumatoid Arthritis

The aim of this study was to design a click-crosslinked hyaluronic acid (HA) (Cx-HA) depot via a click crosslinking reaction between tetrazine-modified HA and trans-cyclooctene-modified HA for direct intra-articular injection into joints affected by rheumatoid arthritis (RA). The Cx-HA depot had significantly more hydrogel-like features and a longer in vivo residence time than the HA depot. Methotrexate (MTX)-loaded Cx-HA (MTX-Cx-HA)-easily prepared as an injectable formulation-quickly formed an MTX-Cx-HA depot that persisted at the injection site for an extended period. In vivo MTX biodistribution in MTX-Cx-HA depots showed that a high concentration of MTX persisted at the intra-articular injection site for an extended period, with little distribution of MTX to normal tissues. In contrast, direct intra-articular injection of MTX alone or MTX-HA resulted in rapid clearance from the injection site. After intra-articular injection of MTX-Cx-HA into rats with RA, we noted the most significant RA reversal, measured by an articular index score, increased cartilage thickness, extensive generation of chondrocytes and glycosaminoglycan deposits, extensive new bone formation in the RA region, and suppression of tumor necrosis factor-α or interleukin-6 expression. Therefore, MTX-Cx-HA injected intra-articularly persists at the joint site in therapeutic MTX concentrations for an extended period, thus increasing the duration of RA treatment, resulting in an improved relief of RA.

Polymer-drug conjugates in inflammation treatment

Inflammation is a vital defense mechanism of living organisms. However, persistent and chronic inflammation may lead to severe pathological processes and evolve into various chronic inflammatory diseases (CID), e.g. rheumatoid arthritis, multiple sclerosis, multiple sclerosis, systemic lupus erythematosus or inflammatory bowel diseases, or certain types of cancer. Their current treatment usually does not lead to complete remission. The application of nanotherapeutics may significantly improve CID treatment, since their accumulation in inflamed tissues has been described and is referred to as extravasation through leaky vasculature and subsequent inflammatory cell-mediated sequestration (ELVIS). Among nanotherapeutics, water-soluble polymer-drug conjugates may be highly advantageous in CID treatment due to the possibility of their passive and active targeting to the inflammation site and controlled release of active agents once there. The polymer-drug conjugate consists of a hydrophilic biocompatible polymer backbone along which the drug molecules are covalently attached via a biodegradable linker that enables controlled drug release. Their active targeting or bio-imaging can be achieved by introducing the cell-specific targeting moiety or imaging agents into the polymer conjugate. Here, we review the relationship between polymer conjugates and inflammation, including the benefits of the application of polymer conjugates in inflammation treatment, the anti-inflammatory activity of polymer drug conjugates and potential polymer-promoted inflammation and immunogenicity.

Targeted delivery of hyaluronic acid-coated solid lipid nanoparticles for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease. Long-term, high-dose glucocorticoid therapy can be used to treat the disease, but the fact that the drug distributes systemically can give rise to severe adverse effects. Here we develop a targeted system for treating RA in which the glucocorticoid prednisolone (PD) is encapsulated within solid lipid nanoparticles (SLNs) coated with hyaluronic acid (HA), giving rise to HA-SLNs/PD. HA binds to hyaluronic receptor CD44, which is over-expressed on the surface of synovial lymphocytes, macrophages and fibroblasts in inflamed joints in RA. As predicted, HA-SLNs/PD particles accumulated in affected joint tissue after intravenous injection into mice with collagen-induced arthritis (CIA), and HA-SLNs/PD persisted longer in circulation and preserved bone and cartilage better than free drug or drug encapsulated in SLNs without HA. HA-SLNs/PD reduced joint swelling, bone erosion and levels of inflammatory cytokines in serum. These results suggest that encapsulating glucocorticoids such as PD in HA-coated SLNs may render them safe and effective for treating inflammatory disorders.

Suppression of human arthritis synovial fibroblasts inflammation using dexamethasone-carbon nanotubes via increasing caveolin-dependent endocytosis and recovering mitochondrial membrane potential

Dexamethasone (DEX), a non-particulate glucocorticoid (GC) to inhibit anti-inflammatory response, has been widely used for the treatment of various diseases such as arthritis, cancer, asthma, chronic obstructive pulmonary disease, cerebral edema, and multiple sclerosis. However, prolonged and/or high-dose GC therapy can cause various serious adverse effects (adrenal insufficiency, hyperglycemia, Cushing’s syndrome, osteoporosis, Charcot arthropathy, etc). In this study, developed DEX-carbon nanotube (CNT) conjugates improved intracellular drug delivery via increased caveolin-dependent endocytosis and ultimately suppressed the expression of major pro-inflammatory cytokines in tumor necrosis factor-α (TNF-α)-stimulated human fibroblast-like synoviocytes (FLS) at low drug concentrations. Specifically, DEX on polyethylene-glycol (PEG)-coated CNTs induced caveolin uptake, recovered mitochondrial disruption, and inhibited reactive oxygen species production by targeting mitochondria that was released from the early endosome in TNF-α-stimulated FLS. The obtained results clearly demonstrated that DEX-PEG-coated CNTs significantly inhibited the inflammation by FLS in rheumatoid arthritis (RA) by achieving greater drug uptake and efficient intracellular drug release from the endosome, thus suggesting a mechanism of effective low-dose GC therapy to treat inflammatory diseases, including RA and osteoarthritis.

Recent advances in nanomedicines for the treatment of rheumatoid arthritis

Schematic illustration of inflammatory microenvironment in inflamed joints and events occurring in rheumatoid arthritis.

An Injectable, Click-Cross-Linked Small Intestinal Submucosa Drug Depot for the Treatment of Rheumatoid Arthritis

Here, a click-cross-linked small intestine submucosa (SIS) drug depot is described for the treatment of rheumatoid arthritis (RA). To the best of the knowledge, there have been no studies related to the intra-articular injection of methotrexate (Met)-loaded click-cross-linkable SIS (Met-loaded Cx-SIS) for RA treatment. As the key objective of this work, injectable formulations of tetrazine-modified SIS (TE-SIS) and transcyclooctene-modified SIS (TC-SIS) are employed as drug depots. Within a few seconds, the simple mixing of equal amounts of TE-SIS and TC-SIS suspensions forms a gelatinous click-cross-linked SIS (Cx-SIS) drug depot in vitro and in vivo. The formed Cx-SIS depot is maintained in the articular joint over an extended period, while SIS alone rapidly disappears. Injectable formulations of Met-loaded Cx-SIS and Met-loaded SIS are prepared and then injected into articular joints to form drug depots. Compared to animals treated with Met-loaded SIS, RA animals treated with Met-loaded Cx-SIS show effective RA repair, as well as extensive regeneration of chondrocytes and glycosaminoglycan deposits. Collectively, these results indicate that the Met-loaded Cx-SIS depot is successfully formed after intra-articular injection of click-cross-linkable SIS, and that this formulation induces long-lasting Met release and allows Met to act effectively in the articular joint, resulting in RA repair.

Albumin-Polymer-Drug Conjugates: Long Circulating, High Payload Drug Delivery Vehicles

Albumin is an exquisite tool of nature used in biomedicine to achieve long blood residence time for drugs, but the payload it can carry is typically limited to one molecule per protein. In contrast, synthetic macromolecular prodrugs contain multiple copies of drugs per polymer chain but offer only a marginal increase in the circulation lifetime of the drugs. We combine the benefits of the two platforms and at the same time overcome their respective limitations. Specifically, we develop the synthesis of albumin-polymer-drug conjugates to obtain long circulating, high payload drug delivery vehicles. In vivo data validate that albumin endows the conjugate with a blood residence time similar to that of the protein and well exceeding that of the polymer. Therapeutic activity of the conjugates is validated using prodrugs of panobinostat, an HIV latency reversal agent, in which case the conjugates matched the drug in terms of efficacy of treatment.

Star-Shaped Amphiphilic Hyperbranched Polyglycerol Conjugated with Dendritic Poly(l-lysine) for the Codelivery of Docetaxel and MMP-9 siRNA in Cancer Therapy

The drug/gene codelivery is a promising strategy for cancer treatment. Herein, to realize the codelivery of docetaxel and MMP-9 siRNA plasmid efficiently into tumor cells, a star-shaped amphiphilic copolymer consisting of hyperbranched polyglycerol derivative (HPG-C18) and dendritic poly(l-lysine) (PLLD) was synthesized by the click reaction between azido-modified HPG-C18 and propargyl focal point PLLD. The obtained HPG-C18-PLLD could form the nanocomplexes with docetaxel and MMP-9, and the complexes showed good gene delivery ability in vitro by inducing an obvious decrease in MMP-9 protein expression in MCF-7 cells. The apoptosis assay showed that the complex could induce a more significant apoptosis to breast cancer cells than that of docetaxel or MMP-9 used alone. In vivo assay indicated that the codelivery strategy displayed a better effect on tumor inhibition. Moreover, HPG-C18-PLLD displayed lower toxicity as well as better blood compatibility compared to polyethylenimine PEI-25k, which may be the result of that HPG-C18-PLLD showed the comparative MMP-9 delivery ability in vivo compared with PEI-25k even if it showed the slight lower transfection efficiency in vitro. Therefore, HPG-C18-PLLD is a safe and effective carrier for the codelivery of drug/gene, which should be encouraged in tumor therapy.

Local and targeted drug delivery for bone regeneration

While experimental bone regeneration approaches commonly employ cells, technological hurdles prevent translation of these therapies. Alternatively, emulating the spatiotemporal cascade of endogenous factors through controlled drug delivery may provide superior bone regenerative approaches. Surgically placed drug depots have clinical indications. Additionally, noninvasive systemic delivery can be used as needed for poorly healing bone injuries. However, a major hurdle for systemic delivery is poor bone biodistribution of drugs. Thus, peptides, aptamers, and phosphate-rich compounds with specificity toward proteins, cells, and molecules within the regenerative bone microenvironment may enable the design of targeted carriers with bone biodistribution greater than that achieved by drug alone. These carriers, combined with osteoregenerative drugs and/or stimuli-sensitive linkers, may enhance bone regeneration while minimizing off-target tissue effects.

Charge based intra-cartilage delivery of single dose dexamethasone using Avidin nano-carriers suppresses cytokine-induced catabolism long term

OBJECTIVE

Avidin exhibits ideal characteristics for targeted intra-cartilage drug delivery: its small size and optimal positive charge enable rapid penetration through full-thickness cartilage and electrostatic binding interactions that give long half-lives in vivo. Here we conjugated Avidin with dexamethasone (DEX) and tested the hypothesis that single-dose Avidin-delivered DEX can ameliorate catabolic effects in cytokine-challenged cartilage relevant to post-traumatic OA.

METHODS

Avidin was covalently conjugated with DEX using fast (ester) and slow, pH-sensitive release (hydrazone) linkers. DEX release kinetics from these conjugates was characterized using (3)H-DEX-Avidin (scintillation counting). Cartilage explants treated with IL-1α were cultured with or without Avidin-DEX conjugates and compared to soluble DEX. Sulfated-glycosaminoglycan (sGAG) loss and biosynthesis rates were measured using DMMB assay and (35)S-incorporation, respectively. Chondrocyte viability was measured using fluorescence staining.

RESULTS

Ester linker released DEX from Avidin significantly faster than hydrazone under physiological buffer conditions. Single dose Avidin-DEX suppressed cytokine-induced sGAG loss over 3-weeks, rescued IL-1α-induced cell death, and restored sGAG synthesis levels without causing cytotoxicity. The two Avidin-DEX conjugates in 1:1 combination (fast:slow) had the most prominent bioactivity compared to single dose soluble-DEX, which had a shorter-lived effect and thus needed continuous replenishment throughout the culture period to ameliorate catabolic effects.

CONCLUSION

Intra-cartilage drug delivery remains inadequate as drugs rapidly clear from the joint, requiring multiple injections or sustained release of high doses in synovial fluid. A single dose of Avidin-conjugated drug enables rapid uptake and sustained delivery inside cartilage at low intratissue doses, and potentially can minimize unwanted drug exposure to other joint tissues.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

A Low Protein Binding Cationic Poly(2-oxazoline) as Non-Viral Vector

Developing safe and efficient non-viral gene delivery systems remains a major challenge. We present a new cationic poly(2-oxazoline) (CPOx) block copolymer for gene therapy that was synthesized by sequential polymerization of non-ionic 2-methyl-2-oxazoline and a new 2-oxazoline monomer, 2-(N-methyl, N-Boc-amino)-methyl-2-oxazoline, followed by deprotection of the pendant secondary amine groups. Upon mixing with plasmid DNA (pDNA), CPOx forms small (diameter ≈80 nm) and narrowly dispersed polyplexes (PDI <0.2), which are stable upon dilution in saline and against thermal challenge. These polyplexes exhibited low plasma protein binding and very low cytotoxicity in vitro compared to the polyplexes of pDNA and poly(ethylene glycol)-b-poly(L-lysine) (PEG-b-PLL). CPOx/pDNA polyplexes at N/P = 5 bound considerably less plasma protein compared to polyplexes of PEG-b-PLL at the same N/P ratio. This is a unique aspect of the developed polyplexes emphasizing their potential for systemic delivery in vivo. The transfection efficiency of the polyplexes in B16 murine melanoma cells was low after 4 h, but increased significantly for 10 h exposure time, indicative of slow internalization of polyplexes. Addition of Pluronic P85 boosted the transfection using CPOx/pDNA polyplexes considerably. The low protein binding of CPOx/pDNA polyplexes is particularly interesting for the future development of targeted gene delivery.

A holistic approach to targeting disease with polymeric nanoparticles

The primary goal of nanomedicine is to improve clinical outcomes. To this end, targeted nanoparticles are engineered to reduce non-productive distribution while improving diagnostic and therapeutic efficacy. Paradoxically, as this field has matured, the notion of targeting has been minimized to the concept of increasing the affinity of a nanoparticle for its target. This Opinion article outlines a holistic view of nanoparticle targeting, in which the route of administration, molecular characteristics and temporal control of the nanoparticles are potential design variables that must be considered simultaneously. This comprehensive vision for nanoparticle targeting will facilitate the integration of nanomedicines into clinical practice.

Novel multi-sensitive pseudo-poly(amino acid) for effective intracellular drug delivery

Schematic illustration of DOX loading, endocytosis and intracellular microenvironment triggered release from PRDSP@DOX NPs.

RGD-peptides modifying dexamethasone: to enhance the anti-inflammatory efficacy and limit the risk of osteoporosis

RGD-peptides modifying dexamethasone can enhance the anti-inflammatory efficacy and limit the risk of osteoporosis.

Carbohydrate PEGylation, an approach to improve pharmacological potency

Conjugation with polyethylene glycol (PEG), known as PEGylation, has been widely used to improve the bioavailability of proteins and low molecular weight drugs. The covalent conjugation of PEG to the carbohydrate moiety of a protein has been mainly used to enhance the pharmacokinetic properties of the attached protein while yielding a more defined product. Thus, glycoPEGylation was successfully applied to the introduction of a PEGylated sialic acid to a preexisting or enzymatically linked glycan in a protein. Carbohydrates are now recognized as playing an important role in host–pathogen interactions in protozoal, bacterial and viral infections and are consequently candidates for chemotherapy. The short in vivo half-life of low molecular weight glycans hampered their use but methods for the covalent attachment of PEG have been less exploited. In this review, information on the preparation and application of PEG-carbohydrates, in particular multiarm PEGylation, is presented.

Polymeric delivery systems for dexamethasone

Glucocorticoids (GCs) are broadly used in the treatment of inflammation and in suppressing hyperactivity of the immune system expressed in allergies, asthma, autoimmune diseases and sepsis. They are pleiotropic in nature, showing a wide range of diverse effects, including those which are harmful for the organism. Dexamethasone (DEX) is one of the most frequently used GCs and is considered as one of the safest. Still serious side-effects have been observed for this drug, mostly due to its hydrophobicity and low bioavailability. The potentially promising polymeric carrier systems to deliver DEX effectively are revised.