Subconjunctival injectable dendrimer-dexamethasone gel for the treatment of corneal inflammation

Thiol-Ene Click-Inspired Late-Stage Modification of Long-Chain Polyurethane Dendrimers

The construction of well-defined polyurethane dendrimers is challenging due to the high reactivity of externally added or in situ formed isocyanates leading to the formation of side products. With a primary focus of dendrimer research being the interaction of the periphery and the core, we report the synthesis of a common polyurethane dendron, which allows for the late-stage variation of both the periphery and the core. The periphery can be varied simply by installing a clickable unit in the dendron and then attaching to the core and vice-versa. Thus, a common dendron allows for varying periphery and core in the final two steps. To accomplish this, a protecting group-free, one-pot multicomponent Curtius reaction was utilized to afford a robust and versatile AB2 type polyurethane dendron employing commercially available simple molecules: 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol. Subsequent late-stage modifications of either dendrons or dendrimers via a thiol-ene click reaction gave surface-functionalized alternating aromatic-aliphatic polyurethane homodendrimers to generation-three (G3). The dendrons and the dendrimers were characterized by NMR, mass spectrometry, and FT-IR analysis. A bifunctional AB2 type dendritic monomer demonstrated this approach’s versatility that can either undergo a thiol-ene click or attachment to the core. This approach enables the incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth for the synthesis of polyurethane dendrimers and other dendritic macromolecules.

Topical Ketotifen Fumarate Inhibits Choroidal Mast Cell Degranulation and Loss of Retinal Pigment Epithelial Cells in Rat Model for Geographic Atrophy

Purpose

This study evaluates whether topical ketotifen fumarate (KTF) can prevent geographic atrophy (GA)-like phenotypes in a rat model.

Methods

Pharmacokinetics (PKs) of KTF after topical administration twice daily for 5 days was analyzed in rat retina, retinal pigment epithelium (RPE)/choroid/sclera, and in plasma by an liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Rats were then given hydrogel implants +/- 48/80 in the superior subconjunctival space and topically treated with 1% and 0.25% of KTF or phosphate buffer saline (PBS) twice daily. Rats were euthanized at 1, 2, 4, and 8 weeks postinjection. Choroidal mast cells (MCs) were stained with nonspecific esterase and the RPE monolayer was labeled with RPE65 and ZO-1 in whole mount choroids. Retinal and choroidal areas were determined in cryosections stained with picrosirius red. Dark-adapted electroretinogram (ERG) was also performed to evaluate retinal function.

Results

PK results showed the highest level of KTF (average 5.6 nM/mg) in the RPE/choroid/sclera in rats given topical 1% KTF. Topical 1% KTF significantly reduced choroidal MC degranulation at 1 week and 2 weeks (both P < 0.001) and RPE loss at 4 weeks (P < 0.001) as well as retinal and choroidal thinning (both P < 0.001) and reduction in ERG amplitude at 8 weeks (P < 0.05) compared to PBS. Similar results were obtained with 0.25% KTF.

Conclusions

Both 1% and 0.25% KTF eye drops effectively reduced MC degranulation, RPE loss, and retinal and choroidal thinning while preventing the decline of ERG amplitude in a GA-like rat model. These data suggest that topical KTF might be a new therapeutic drug for treating GA.

Translational Relevance

The results of this study demonstrate that topical KTF successfully reduced GA-like phenotypes in a rat model and may provide a novel therapy for GA.

Encapsulation of polyprodrugs enables an efficient and controlled release of dexamethasone

Water-soluble low molecular weight drugs, such as the synthetic glucocorticoid dexamethasone (DXM), can easily leak out of nanocarriers after encapsulation due to their hydrophilic nature and small size. This can lead to a reduced therapeutic efficacy and therefore to unwanted adverse effects on healthy tissue. Targeting DXM to inflammatory cells of the liver like Kupffer cells or macrophages is a promising approach to minimize typical side effects. Therefore, a controlled transport to the cells of interest and selective on-site release is crucial. Aim of this study was the development of a DXM-phosphate-based polyprodrug and the encapsulation in silica nanocontainers (SiO₂ NCs) for the reduction of inflammatory responses in liver cells. DXM was copolymerized with a linker molecule introducing pH-cleavable hydrazone bonds in the backbone and obtaining polyprodrugs (PDXM). Encapsulation of PDXMs into SiO₂ NCs provided a stable confinement avoiding uncontrolled leakage. PDXMs were degraded under acidic conditions and subsequently released out of SiO₂ NCs. Biological studies showed significantly enhanced anti-inflammatory capacity of the polyprodrug nanoformulations over non-encapsulated DXM or soluble polyprodrugs. These results demonstrate the advantage of combining the polyprodrug strategy with nanocarrier-mediated delivery for enhanced control of the delivery of water-soluble low molecular weight drugs.

Injectable oligomer-cross-linked gelatine hydrogels via anhydride-amine-conjugation

Injectable gelatine-based hydrogels are valuable tools for drug and cell delivery due to their extracellular matrix-like properties that can be adjusted by the degree of cross-linking. We have established anhydride-containing oligomers for the cross-linking of gelatine via anhydride-amine-conjugation. So far, this conversion required conditions not compatible with cell encapsulation or in vivo injection. In order to overcome this limitation, we developed an array of quarter-oligomers varying in comonomer composition and contents of reactive anhydride units reactive towards amine groups under physiological conditions. The oligomers were of low molecular weight (Mn < 5 kDa) with a high degree of chemically intact anhydrides. Chemical comonomer composition was determined by 1H-NMR. Dissolutions experiments confirmed improved hydrophilicity of the synthesized oligomers over our established compositions. Injectable formulations are described utilizing cytocompatible concentrations of constituent materials and proton-scavenging base. Degree of cross-linking and stiffness of injectable hydrogels were controlled by composition. The gels hold promise as injectable drug or cell carrier and as bioink.

The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye

The prevalence of chronic fundus diseases is increasing with the aging of the general population. The treatment of these intraocular diseases relies on invasive drug delivery because of the globular structure and multiple barriers of the eye. Frequent intraocular injections bring heavy burdens to the medical care system and patients. The use of topical drugs to treat retinal diseases has always been an attractive solution. The fast development of new materials and technologies brings the possibility to develop innovative topical formulations. This article reviews anatomical and physiological barriers of the eye which affect the bioavailability of topical drugs. In addition, we summarize innovative topical formulations which enhance the permeability of drugs through the ocular surface and/or extend the drug retention time in the eye. This article also reviews the differences of eyes between different laboratory animals to address the translational challenges of preclinical models. The fast development of in vitro eye models may provide more tools to increase the clinical translationality of topical formulations for intraocular diseases. Clinical successes of topical formulations rely on continuous and collaborative efforts between different disciplines.

Hydrogels as Emerging Materials for Cornea Wound Healing

Hydrogel biomaterials have many favorable characteristics including tuneable mechanical behavior, cytocompatibility, optical properties suitable for regeneration and restoration of the damaged cornea tissue. The cornea is a tissue susceptible to various injuries and traumas with a complicated healing cascade, in which conserving its transparency and integrity is critical. Accordingly, the hydrogels' known properties along with the stimulation of nerve and cell regeneration make them ideal scaffold for corneal tissue engineering. Hydrogels have been used extensively in clinical applications for the repair and replacement of diseased organs. The development and optimizing of novel hydrogels to repair/replace corneal injuries have been the main focus of researches within the last decade. This research aims to critically review in vitro, preclinical, as well as clinical trial studies related to corneal wound healing using hydrogels in the past 10 years, as this is considered as an emerging technology for corneal treatment. Several unique modifications of hydrogels with smart behaviors have undergone early phase clinical trials and showed promising outcomes. Financially, this considers a multibillion dollars industry and with huge interest from medical devices as well as pharmaceutical industries with several products may emerge within the next five years.

Epigenetic Landscape Analysis of the Long Non-Coding RNA and Messenger RNA in a Mouse Model of Corneal Alkali Burns

Purpose

Corneal alkali burns (CABs) are a common clinical ocular disease, presenting a poor prognosis. Although some long noncoding RNAs (lncRNAs) reportedly play a key role in epigenetic regulation associated with CABs, studies regarding the lncRNA signature in CABs remain rare and elusive.

Methods

A CAB model was established in C57BL/6J mice and profiling of lncRNA expressions was performed by RNA-Seq. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to predicate the related pathological pathways and candidate genes. RT-qPCR was used to verify the expression pattern of lncRNAs and related mRNAs, both in vitro and in vivo. Data were statistically analyzed by GraphPad Prism version 6.0.

Results

In all, 4436 aberrantly expressed lncRNAs were identified in CAB mice when compared with control mice. In the top 13 aberrantly expressed lncRNAs, Bc037156 and 4930511E03Rik were confirmed as the most significantly altered lncRNAs. Pathway analysis revealed that mitogen-activated protein kinase (MAPK) signaling pathway was most enriched. Following 4930511E03Rik siRNA treated, Srgn, IL-1β and Cxcr2 were significant upregulated in corneal epithelial cells, corneal keratocytes, and bone marrow dendritic cells, with NaOH treatment. Moreover, after Bc037156 siRNA treated, expression levels of IL-1β and Srgn were significantly downregulated in the three cell lines.

Conclusions

Our study suggests that Bc037156 and 4930511E03Rik may be involved in inflammation, immune response, and neovascularization by regulating Srgn, IL-1β, and Cxcr2 expression after CAB. These candidate lncRNAs and mRNAs may be the potential targets for the treatment strategy of the alkali injured cornea.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Epithelium-Penetrable Nanoplatform with Enhanced Antibiotic Internalization for Management of Bacterial Keratitis

A standardized regimen for addressing the adverse effects of bacterial keratitis on vision remains an intractable challenge due to poor epithelial penetration and a short corneal retention time. In this study, a new strategy is proposed to implement the direct transport of antibiotics to bacteria-infected corneas via topical administration of an epithelium-penetrable biodriven nanoplatform, thereby enabling the efficacious treatment of bacterial keratitis. The nanoplatforms were composed of amphiphilic glycopolymers containing boron dipyrromethene and boronic acid moieties with stable fluorescence characteristics and the ability to potentiate epithelial penetration deep into the cornea. The boronic acid-derived nanoplatforms enabled efficient cellular internalization through the high affinity of boric acid groups for the diol-containing bacterial cell wall, resulting in enhanced drug penetration and retention inside the pathogenic bacteria. The bacterial cells formed agglomerations after incorporating the nanoplatforms along with a special mechanism to release the encapsulated cargo in response to in situ bacteria. Compared with the drug alone, this smart system achieved enhanced bacterial mortality and attenuated inflammation associated with Staphylococcus aureus-induced keratitis in rats, demonstrating a paradigm for targeted ocular drug delivery and an alternative strategy for managing bacterial keratitis or other bacterial infections by heightening corneal permeability and transcorneal bioavailability.

Fabrication and Characterisation of a Photo-Responsive, Injectable Nanosystem for Sustained Delivery of Macromolecules

The demand for biodegradable sustained release carriers with minimally invasive and less frequent administration properties for therapeutic proteins and peptides has increased over the years. The purpose of achieving sustained minimally invasive and site-specific delivery of macromolecules led to the investigation of a photo-responsive delivery system. This research explored a biodegradable prolamin, zein, modified with an azo dye (DHAB) to synthesize photo-responsive azoprolamin (AZP) nanospheres loaded with Immunoglobulin G (IgG). AZP nanospheres were incorporated in a hyaluronic acid (HA) hydrogel to develop a novel injectable photo-responsive nanosystem (HA-NSP) as a potential approach for the treatment of chorio-retinal diseases such as age-related macular degeneration (AMD) and diabetic retinopathy. AZP nanospheres were prepared via coacervation technique, dispersed in HA hydrogel and characterised via infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Size and morphology were studied via scanning electron microscopy (SEM) and dynamic light scattering (DLS), UV spectroscopy for photo-responsiveness. Rheological properties and injectability were investigated, as well as cytotoxicity effect on HRPE cell lines. Particle size obtained was <200 nm and photo-responsiveness to UV = 365 nm by decreasing particle diameter to 94 nm was confirmed by DLS. Encapsulation efficiency of the optimised nanospheres was 85% and IgG was released over 32 days up to 60%. Injectability of HA-NSP was confirmed with maximum force 10 N required and shear-thinning behaviour observed in rheology studies. In vitro cell cytotoxicity effect of both NSPs and HA-NSP showed non-cytotoxicity with relative cell viability of ≥80%. A biocompatible, biodegradable injectable photo-responsive nanosystem for sustained release of macromolecular IgG was successfully developed.

Effect of mesenchymal stromal cells encapsulated within polyethylene glycol-collagen hydrogels formed in situ on alkali-burned corneas in an ex vivo organ culture model

BACKGROUND AIMS

Corneal inflammation after alkali burns often results in vision loss due to corneal opacification and neovascularization. Mesenchymal stem cells (MSCs) and their secreted factors (secretome) have been studied for their anti-inflammatory and anti-angiogenic properties with encouraging results. However, topical instillation of MSCs or their secretome is often accompanied by issues related to delivery or rapid washout. Polyethylene glycol (PEG) and collagen are well-known biomaterials used extensively in scaffolds for tissue engineering. To effectively suppress alkaline burn-induced corneal injury, the authors proposed encapsulating MSCs within collagen gels cross-linked with multi-functional PEG-succinimidyl esters as a means to deliver the secretome of immobilized MSCs.

METHODS

Human MSCs were added to a neutralized collagen solution and mixed with a solution of four-arm PEG-N-hydroxysuccinimide. An ex vivo organ culture was conducted using rabbit corneas injured by alkali burn. MSCs were encapsulated within PEG-collagen hydrogels and injected onto the wounded cornea immediately following alkali burn and washing. Photographs of the ocular surface were taken over a period of 7 days after the alkali burn and processed for immunohistochemical evaluation. Samples were split into three groups: injury without treatment, MSCs alone, and MSCs encapsulated within PEG-collagen hydrogels.

RESULTS

All corneas in ex vivo organ culture lost their transparency immediately after alkali burn, and only the groups treated with MSCs and MSCs encapsulated within PEG-collagen hydrogels recovered some transparency after 7 days. Immunohistochemical analysis revealed increased expression of vimentin in the anterior corneal stroma of the group without treatment indicative of fibrotic healing, whereas less stromal vimentin was detected in the group containing MSCs encapsulated within the PEG-collagen hydrogels.

CONCLUSIONS

PEG-collagen hydrogels enable the encapsulation of viable MSCs capable of releasing secreted factors onto the ocular surface. Encapsulating MSCs within PEG-collagen hydrogels may be a promising method for delivering their therapeutic benefits in cases of ocular inflammatory diseases, such as alkali burn injuries.

Injectable bio-responsive hydrogel for therapy of inflammation related eyelid diseases

Eyelid plays a vital role in protecting the eye from injury or infection. Inflammation related eyelid diseases, such as blepharitis, are the most common ocular disorders that affect human's vision and quality of life. Due to the physiological barriers and anatomical structures of the eye, the bioavailability of topical administrated therapeutics is typically less than 5%. Herein, we developed a bio-responsive hydrogel drug delivery system using a generally recognized as safe compound, triglycerol monostearate (TG-18), for in-situ eyelid injection with sustained therapeutics release. In vitro, drug release and disassembly time of Rosiglitazone loaded hydrogel (Rosi-hydrogel) were estimated in the presence or absence of MMP-9, respectively. Moreover, the disassembly of TG-18 hydrogel was evaluated with 9-month-old and 12-month-old mice in vivo. Owing to the bio-responsive nature of Rosi-hydrogel, the on-demand Rosiglitazone release is achieved in response to local enzymes. These findings are proved by further evaluation in the age-related meibomian gland dysfunction mice model, and the bio-responsive hydrogel is used as an in-situ injection to treat eyelid diseases. Taken together, the in-situ eyelid injection with sustained drug release opens a window for the therapy of inflammation related eyelid diseases.

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This study is the first application of injectable bio-responsive hydrogel for therapy of inflammation related eyelid diseases.

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The enzyme response characteristic is extremely suitable for enhancing drug bioavailability in ocular drug delivery.

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In-situ release of rosiglitazone can effectively treat age-related meibomian gland dysfunction in the mice model.

Nicotinamide Mononucleotide Alleviates Hyperosmolarity-Induced IL-17a Secretion and Macrophage Activation in Corneal Epithelial Cells/Macrophage Co-Culture System

Background

Hyperosmosis stress (HS) was a key pathological factor in the development of dry eye disease (DED). Nicotinamide mononucleotide (NMN) demonstrated protective effects in the corneal damage, however, its role in the HS-induced DED remained unclear.

Methods

A NaCl based HS in-vitro model (500 mOsm) was generated and used in a co-culture system including corneal epithelial cells (CEC) and macrophage cell line RAW264.7. The effect of NMN on NAD+ metabolism and the expression of HS biomarker, tonicity-responsive element binding protein (TonEBP), was studied in the CEC. The cellular activity, including cell viability, apoptosis status and lactate dehydrogenase (LDH) release through trypan blue staining, flow cytometry and LDH assay, respectively. The mitochondrial membrane potential (MMP) assay would be conducted using the JC1 kit. The expression of IL-17a were detected using RT-PCR, ELISA and Western blot. After co-culture with the CEC in different group for 24 h, the phagocytosis ability and macrophage polarization were assessed in RAW264.7 cells co-cultured with CEC with or without HS or NMN treatment. Besides, the involvement of Notch pathway in the RAW264.7 would be analyzed. The potential involvement of Sirtuin 1 (SIRT1) and IL-17a in the crosstalk between CEC and macrophage was studied with SIRT1 inhibitor EX 527 and anti-IL-17a monoclonal antibody, respectively.

Results

NMN treatment increased NAD+ concentration and thus improved cell viability, reduced apoptotic rate and decreased the LDH release in HS-treated CEC. Besides, NMN alleviated HS-induced MMP, intracellular ROS and LDH release. Besides, it was confirmed NMN improve SIRT1 function and decreased the HS related IL-17a expression in CEC and then alleviated macrophage phagocytosis ability and M1 polarization based on a CEC-macrophage co-culture system. Moreover, NMN treatment of CEC in the CEC could moderate the subsequent macrophage activation through Notch pathway. SIRT1 activation and IL-17a inhibition was regarded as key progress in the function of NMN based on the application of EX 527 and anti-IL-17a antibody in the CEC-macrophage co-culture system.

Conclusion

The findings demonstrated that NMN could alleviated HS-induced DED status through regulating the CEC/macrophage interaction. Our data pointed to the role of SIRT1, IL-17a and Notch pathway in the function of NMN and then provided updated knowledge of potential NMN application in the management of DED.

Nanotechnology-based drug delivery systems in orthopedics

In recent years, nanotechnology has led to significant scientific and technological advances in diverse fields, specifically within the field of medicine. Owing to the revolutionary implications in drug delivery, nanotechnology-based drug delivery systems have gained an increasing research interest in the current medical field. A variety of nanomaterials with unique physical, chemical and biological properties have been engineered to develop new drug delivery systems for the local, sustained and targeted delivery of drugs with improved therapeutic efficiency and less or no toxicity, representing a very promising approach for the effective management of diseases. The utility of nanotechnology, particularly in the field of orthopedics, is a topic of extensive research. Nanotechnology has a great potential to revolutionize treatment, diagnostics, and research in the field of orthopedics. Nanophase drug delivery has shown great promise in their ability to deliver drugs at nanoscale for a variety of orthopedic applications. In this review, we discuss recent advances in the field of nanostructured drug delivery systems for orthopedic applications.

Zoudani E, Daliri R, Aghamirsalim M, Raahemifar K. Biodegradable Nanoparticle for Cornea Drug Delivery: Focus Review

During recent decades, researchers all around the world have focused on the characteristic pros and cons of the different drug delivery systems for cornea tissue change for sense organs. The delivery of various drugs for cornea tissue is one of the most attractive and challenging activities for researchers in biomaterials, pharmacology, and ophthalmology. This method is so important for cornea wound healing because of the controllable release rate and enhancement in drug bioavailability. It should be noted that the delivery of various kinds of drugs into the different parts of the eye, especially the cornea, is so difficult because of the unique anatomy and various barriers in the eye. Nanoparticles are investigated to improve drug delivery systems for corneal disease. Biodegradable nanocarriers for repeated corneal drug delivery is one of the most attractive and challenging methods for corneal drug delivery because they have shown acceptable ability for this purpose. On the other hand, by using these kinds of nanoparticles, a drug could reside in various part of the cornea for longer. In this review, we summarized all approaches for corneal drug delivery with emphasis on the biodegradable nanoparticles, such as liposomes, dendrimers, polymeric nanoparticles, niosomes, microemulsions, nanosuspensions, and hydrogels. Moreover, we discuss the anatomy of the cornea at first and gene therapy at the end.

Pranoprofen Nanoparticles With Poly(L-Lactide)-b-Poly(Ethylene Glycol)-b-Poly(L-Lactide) as the Matrix Toward Improving Ocular Anti-inflammation

Nanotechnology using biodegradable polymer carriers with good biocompatibility and bioabsorbability has been studied and applied extensively in drug delivery systems and biomedical engineering. In this work, the triblocked oligomer poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLEL) with the molecular weight of 2.08 KDa was first synthesized. Its chemistry was characterized by hydrogen nuclear magnetic resonance (1H-NMR) spectrum and Fourier transform infrared (FTIR) spectroscopy. Subsequently, the nanoparticles (NPs) of PLEL and pranoprofen (PF)-loaded PLEL were prepared with the average particle size of (151.7 ± 5.87) nm using the method of emulsion solvent evaporation. The formula and drug releasing profile were characterized by a transmission electron microscope (TEM), dynamic light scattering (DLS), and ultraviolet spectrophotometer (US). In vitro cytotoxicity assays and in vivo ophthalmic tests were performed to measure the safety and efficacy of the formulations. The results showed that PF NPs relieved the cytotoxicity of pure PF and eliminated ophthalmic irritation. The drug encapsulated in the nanoparticles displayed long-lasting release and good anti-inflammation efficiency in animal eyes. Therefore, we concluded that the present formula (PF NPs) could provide sustained drug release with good treatment effect on eye inflammation, and is promising for its use in ophthalmology in the future.

Are Poly(amidoamine) Dendrimers Safe for Ocular Applications? Toxicological Evaluation in Ocular Cells and Tissues

Purpose: The human eye is a sophisticated and sensitive sensory organ. Because of the existence of the blood-ocular barrier and corneal-scleral barrier, safe and efficient ocular drug delivery system is highly desired; yet, it remains an unsolved issue. Due to the unique structure and drug loading property, Poly(amidoamine) (PAMAM) has received much attention in the ocular drug delivery investigation. Herein, we evaluated the ocular cytotoxicity and biosafety of PAMAM dendrimers. Methods: The ocular cytotoxicity and biosafety of PAMAM dendrimers were evaluated by conducting in vitro and in vivo experiments on ocular systems. The in vitro effect of PAMAM dendrimer of different generations (G4.0, G5.0, and G6.0) and concentrations on ocular cell metabolism, apoptosis, and oxidative damage were quantitatively assessed. In vivo biosafety of PAMAM dendrimers were further investigated on intraocular tissue by ocular irritation and intravitreal injection approaches. Results: It is found that that the cytotoxicity of PAMAM was time and generation dependent. PAMAM at a concentration below 50 μg/mL had minimal impact on the ocular tissue, whereas it caused apparent damage when above 50 μg/mL in the investigated situation. Further, our in vivo results showed that higher concentration of dendrimer (100 μg/mL) was associated with functional impairment demonstrated via optical coherence tomography and electroretinogram, although macroscopic structural changes were absent in fundus and histopathological studies. Overall, a higher concentration of PAMAM, such as above 50 μg/mL, may cause ocular functional damage. Conclusion: The PAMAM at the concentrations lower than 50 μg/mL showed good biocompatibility and biosafety in human ocular cells and tissues.

Dendrimers as Modulators of Brain Cells

Nanostructured hyperbranched macromolecules have been extensively studied at the chemical, physical and morphological levels. The cellular structural and functional complexity of neural cells and their cross-talk have made it rather difficult to evaluate dendrimer effects in a mixed population of glial cells and neurons. Thus, we are at a relatively early stage of bench-to-bedside translation, and this is due mainly to the lack of data valuable for clinical investigations. It is only recently that techniques have become available that allow for analyses of biological processes inside the living cells, at the nanoscale, in real time. This review summarizes the essential properties of neural cells and dendrimers, and provides a cross-section of biological, pre-clinical and early clinical studies, where dendrimers were used as nanocarriers. It also highlights some examples of biological studies employing dendritic polyglycerol sulfates and their effects on glia and neurons. It is the aim of this review to encourage young scientists to advance mechanistic and technological approaches in dendrimer research so that these extremely versatile and attractive nanostructures gain even greater recognition in translational medicine.

Corticosteroids in ophthalmology: drug delivery innovations, pharmacology, clinical applications, and future perspectives

Corticosteroids remain the mainstay of the treatment for various ocular conditions affecting the ocular surface, anterior and posterior segments of the eye due to their anti-inflammatory, anti-oedematous, and anti-neovascularization properties. Prednisolone, prednisolone acetate, dexamethasone, triamcinolone acetonide, fluocinolone acetonide, and loteprednol etabonate are amongst the most widely used ophthalmic corticosteroids. Corticosteroids differ in their activity and potency in the eye due to their inherent pharmacological and pharmaceutical differences. Different routes and regimens are available for ocular administration of corticosteroids. Conventional topical application to the eye is the route of choice when targeting diseases affecting the ocular surface and anterior segment, while periocular, intravitreal, and suprachoroidal injections can be potentially effective for posterior segment diseases. Corticosteroid-induced intraocular pressure elevation and cataract formation remain the most significant local risks following topical as well as systemic corticosteroid administration. Invasive drug administration via intracameral, subconjunctival, and intravitreal injection can enhance ocular bioavailability and minimize dose and dosing frequency of administration, yet may exacerbate ocular side effects of corticosteroids. This review provides a critical appraisal of the ophthalmic uses of corticosteroid, routes of administration, drug delivery fundamentals and novel ocular implantable steroid delivery systems, factors influencing side effects, and future perspectives for ocular corticosteroid therapy.

Advanced nanomedicines for the treatment of inflammatory diseases

Inflammation, a common feature of many diseases, is an essential immune response that enables survival and maintains tissue homeostasis. However, in some conditions, the inflammatory process becomes detrimental, contributing to the pathogenesis of a disease. Targeting inflammation by using nanomedicines (i.e. nanoparticles loaded with a therapeutic active principle), either through the recognition of molecules overexpressed onto the surface of activated macrophages or endothelial cells, or through enhanced vasculature permeability, or even through biomimicry, offers a promising solution for the treatment of inflammatory diseases. After providing a brief insight on the pathophysiology of inflammation and current therapeutic strategies, the review will discuss, at a pre-clinical stage, the main innovative nanomedicine approaches that have been proposed in the past five years for the resolution of inflammatory disorders, finally focusing on those currently in clinical trials.

The Role of Nano-ophthalmology in Treating Dry Eye Disease

Dry eye disease (DED) is a common multifactorial disease linked to the tears/ocular surface leading to eye discomfort, ocular surface damage, and visual disturbance. Antiinflammatory agents (steroids and cyclosporine A), hormonal therapy, antibiotics, nerve growth factors, essential fatty acids are used as treatment options of DED. Current therapies attempt to reduce the ocular discomfort by producing lubrication and stimulating gland/nerve(s) associated with tear production, without providing a permanent cure for dry eye. Nanocarrier systems show a great promise to revolutionize drug delivery in DED, offering many advantages such as site specific and sustained delivery of therapeutic agents. This review presents an overview, pathophysiology, prevalence and etiology of DED, with an emphasis on preclinical and clinical studies involving the use of nanocarrier systems in treating DED. Lay Summary: Dry eye disease (DED) is a multifactorial disease associated with tear deficiency or excessive tear evaporation. There are several review articles that summarize DED, disease symptoms, causes and treatment approaches. Nanocarrier systems show a great promise to revolutionize drug delivery in DED, offering many advantages such as site specific and sustained delivery of therapeutic agents. Very few review articles summarize the findings on the use of nanotherapeutics in DED. In this review, we have exclusively discussed the preclinical and clinical studies of nanotherapeutics in DED therapy. This information will be attractive to both academic and pharmaceutical industry researchers working in DED therapeutics.

A role for mast cells in geographic atrophy

Mast cells (MCs) are the initial responders of innate immunity and their degranulation contribute to various etiologies. While the abundance of MCs in the choroid implies their fundamental importance in the eye, little is known about the significance of MCs and their degranulation in choroid. The cause of geographic atrophy (GA), a progressive dry form of age-related macular degeneration is elusive and there is currently no therapy for this blinding disorder. Here we demonstrate in both human GA and a rat model for GA, that MC degranulation and MC-derived tryptase are central to disease progression. Retinal pigment epithelium degeneration followed by retinal and choroidal thinning, characteristic phenotypes of GA, were driven by continuous choroidal MC stimulation and activation in a slow release fashion in the rat. Genetic manipulation of MCs, pharmacological intervention targeting MC degranulation with ketotifen fumarate or inhibition of MC-derived tryptase with APC 366 prevented all of GA-like phenotypes following MC degranulation in the rat model. Our results demonstrate the fundamental role of choroidal MC involvement in GA disease etiology, and will provide new opportunities for understanding GA pathology and identifying novel therapies targeting MCs.

Suppression of pathological ocular neovascularization by a small molecule, SU1498

Selective inhibition of vascular endothelial growth factor receptor (VEGFR), particularly VEGFR-2, is an efficient method for the treatment of ocular neovascularization. SU1498 is a specific inhibitor of VEGFR-2. In this study, we investigated the role of SU1498 in ocular neovascularization. Administration of SU1498 did not show any cytotoxicity and tissue toxicity at the tested concentrations. Administration of SU1498 reduced the size and thickness of choroidal neovascularization and decreased the mean length and mean number of corneal neovascular vessels induced by alkali burn. Pretreatment of SU1498 significantly reduced the proliferation, migration, and tube formation ability of HUVECs. SU1498 played the anti-angiogenic role through the regulation of p38-MAPK signaling. Taken together, inhibition of VEGFR-2 by SU1498 provides a novel therapeutic approach for ocular neovascularization.

Progress in Research on the Role of FGF in the Formation and Treatment of Corneal Neovascularization

Corneal neovascularization (CNV) is a sight-threatening disease usually associated with inflammatory, infectious, degenerative, and traumatic disorders of the ocular surface. Fibroblast growth factor (FGF) family members play an important role in angiogenesis to induce corneal neovascularization, which significantly affects the differentiation, proliferation, metastasis, and chemotaxis of vascular endothelial cells. Both acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) demonstrate positive staining in capillaries and induce corneal stromal cells. The anabolism of endothelial cells is induced by bFGF in corneal neovascularization. FGFs exert their effects via specific binding to cell surface-expressed specific receptors. We believe that both anti-FGF antibodies and anti-FGF receptor antibodies represent new directions for the treatment of CNV. Similar to anti-vascular endothelial growth factor antibodies, subconjunctival injection and eye drops can be considered effective forms of drug delivery.

Nanocarriers for ocular drug delivery: current status and translational opportunity

Ocular diseases have a significant effect on vision and quality of life. Drug delivery to ocular tissues is a challenge to formulation scientists. The major barriers to delivering drugs to the anterior and posterior segments include physiological barriers (nasolacrimal drainage, blinking), anatomical barriers (static and dynamic), efflux pumps and metabolic barriers. The static barriers comprise the different layers of the cornea, sclera, and blood–aqueous barriers whereas dynamic barriers involve conjunctival blood flow, lymphatic clearance and tear drainage. The tight junctions of the blood–retinal barrier (BRB) restrict systemically administered drugs from entering the retina. Nanocarriers have been found to be effective at overcoming the issues associated with conventional ophthalmic dosage forms. Various nanocarriers, including nanodispersion systems, nanomicelles, lipidic nanocarriers, polymeric nanoparticles, liposomes, niosomes, and dendrimers, have been investigated for improved permeation and effective targeted drug delivery to various ophthalmic sites. In this review, various nanomedicines and their application for ophthalmic delivery of therapeutics are discussed. Additionally, scale-up and clinical status are also addressed to understand the current scenario for ophthalmic drug delivery.

Ocular diseases have a significant effect on vision and quality of life.

Fabrication of injectable hydrogels via bio-orthogonal chemistry for tissue engineering

Injectable hydrogels via bio-orthogonal chemistry.

Synergistic effect of halofuginone and dexamethasone on LPS‑induced acute lung injury in type II alveolar epithelial cells and a rat model

Acute lung injury (ALI) is characterized by neutrophilic infiltration, uncontrolled oxidative stress and inflammatory processes. Despite various therapeutic regimes having been performed, there remains no effective pharmacotherapy available to treat ALI. Halofuginone (HF), a ketone isolated from Dichroa febrifuga, exhibits significant anti‑inflammatory and antifibrotic effects. Dexamethasone (DEX), a synthetic glucocorticoid, has been routinely used as an adjuvant therapy in treating inflammatory diseases, including ALI. The present study aimed to investigate the effects of the combination of HF and DEX in the treatment of ALI. The present results suggested that the simultaneous administration of HF and DEX markedly decreased the level of pro‑inflammatory cytokines and increased the level of anti‑inflammatory cytokines, as assessed by western blot analysis. In addition, HF and DEX effectively decreased nuclear factor‑κB activity via suppressing the phosphorylation of P65 in lipopolysaccharide (LPS)‑induced human pulmonary alveolar epithelial cells (HPAEpiC) and lung tissues extracted from ALI rats, as determined by immunofluorescence. Furthermore, in vivo experiments demonstrated that the combination of HF and DEX in LPS‑induced ALI rats defended against lung fibrosis, perivascular inflammation, congestion and edema of pulmonary alveoli, as assessed by histopathological analysis, TUNEL staining and immunohistochemistry assay. Taken together, the present study indicated the synergistic effect of HF and DEX on LPS‑induced ALI in HPAEpiC cells and a rat model. These results offer a novel therapeutic approach for the treatment of ALI.

A Multi-Functional Silicon Nanoparticle Designed for Enhanced Osteoblast Calcification and Related Combination Therapy

Implant materials applied in bone defect commonly focus on the inducement of bone regeneration and neglect to cure complications including bacterial infection and inflammation, which may result in delayed unions or even amputation. In this study, a microporous silica nanoparticle-poly(N-isopropylacrylamide-b-(2-(dimethylamino)ethyl methacrylate) is synthesized for loading DXMS and the ECM-derived peptide (Sequence: Succinic acid-GTPGPQGIAGQRGVV) in order to enhance the osteoblast calcification and relieve related symptoms. Positively charged PDMA blocks endow the nanoparticle with the antimicrobial property. Moreover, the combination of DXMS makes it have the ability of anti-inflammation and promoting calcification formation. Furthermore, incorporation of the peptide leads to a significant improvement of mineralization and alkaline phosphatase expression in the preosteoblast. After intramuscular implantation in mice for four weeks, the results indicate the composite nanoparticle can promote ectopic bone formation. These combined properties make the composite silicon nanoparticle a promising osteogenic drug appropriate for further study in bone repair and related combination therapy.

Leveraging the interplay of nanotechnology and neuroscience: Designing new avenues for treating central nervous system disorders

Nanotechnology has the potential to open many novel diagnostic and treatment avenues for disorders of the central nervous system (CNS). In this review, we discuss recent developments in the applications of nanotechnology in CNS therapies, diagnosis and biology. Novel approaches for the diagnosis and treatment of neuroinflammation, brain dysfunction, psychiatric conditions, brain cancer, and nerve injury provide insights into the potential of nanomedicine. We also highlight nanotechnology-enabled neuroscience techniques such as electrophysiology and intracellular sampling to improve our understanding of the brain and its components. With nanotechnology integrally involved in the advancement of basic neuroscience and the development of novel treatments, combined diagnostic and therapeutic applications have begun to emerge. Nanotheranostics for the brain, able to achieve single-cell resolution, will hasten the rate in which we can diagnose, monitor, and treat diseases. Taken together, the recent advances highlighted in this review demonstrate the prospect for significant improvements to clinical diagnosis and treatment of a vast array of neurological diseases. However, it is apparent that a strong dialogue between the nanoscience and neuroscience communities will be critical for the development of successful nanotherapeutics that move to the clinic, benefit patients, and address unmet needs in CNS disorders.

Let's get small (and smaller): Combining zebrafish and nanomedicine to advance neuroregenerative therapeutics

Several key attributes of zebrafish make them an ideal model system for the discovery and development of regeneration promoting therapeutics; most notably their robust capacity for self-repair which extends to the central nervous system. Further, by enabling large-scale drug discovery directly in living vertebrate disease models, zebrafish circumvent critical bottlenecks which have driven drug development costs up. This review summarizes currently available zebrafish phenotypic screening platforms, HTS-ready neurodegenerative disease modeling strategies, zebrafish small molecule screens which have succeeded in identifying regeneration promoting compounds and explores how intravital imaging in zebrafish can facilitate comprehensive analysis of nanocarrier biodistribution and pharmacokinetics. Finally, we discuss the benefits and challenges attending the combination of zebrafish and nanoparticle-based drug optimization, highlighting inspiring proof-of-concept studies and looking toward implementation across the drug development community.

Therapeutic implications of nanomedicine for ocular drug delivery

Delivering therapeutics to the eye is challenging on multiple levels: rapid clearance of eyedrops from the ocular surface requires frequent instillation, which is difficult for patients; transport of drugs across the blood-retinal barrier when drugs are administered systemically, and the cornea when drugs are administered topically, is difficult to achieve; limited drug penetration to the back of the eye owing to the cornea, conjunctiva, sclera and vitreous barriers. Nanomedicine offers many advantages over conventional ophthalmic medications for effective ocular drug delivery because nanomedicine can increase the therapeutic index by overcoming ocular barriers, improving drug-release profiles and reducing potential drug toxicity. In this review, we highlight the therapeutic implications of nanomedicine for ocular drug delivery.

Corneal Wound Healing Effects of Mesenchymal Stem Cell Secretome Delivered Within a Viscoelastic Gel Carrier

Severe corneal injuries often result in permanent vision loss and remain a clinical challenge. Human bone marrow-derived mesenchymal stem cells (MSCs) and their secreted factors (secretome) have been studied for their antiscarring, anti-inflammatory, and antiangiogeneic properties. We aimed to deliver lyophilized MSC secretome (MSC-S) within a viscoelastic gel composed of hyaluronic acid (HA) and chondroitin sulfate (CS) as a way to enhance corneal re-epithelialization and reduce complications after mechanical and chemical injuries of the cornea. We hypothesized that delivering MSC-S within HA/CS would have improved wound healing effects compared the with either MSC-S or HA/CS alone. The results showed that a once-daily application of MSC-S in HA/CS enhances epithelial cell proliferation and wound healing after injury to the cornea. It also reduced scar formation, neovascularization, and hemorrhage after alkaline corneal burns. We found that combining MSC-S and HA/CS increased the expression of CD44 receptors colocalized with HA, suggesting that the observed therapeutic effects between the MSC-S and HA/CS are in part mediated by CD44 receptor upregulation and activation by HA. The results from this study demonstrate a reproducible and efficient approach for delivering the MSC-S to the ocular surface for treatment of severe corneal injuries. Stem Cells Translational Medicine 2019;8:478-489.

New Advances in General Biomedical Applications of PAMAM Dendrimers

Dendrimers are nanoscopic compounds, which are monodispersed, and they are generally considered as homogeneous. PAMAM (polyamidoamine) was introduced in 1985, by Donald A. Tomalia, as a new class of polymers, named 'starburst polymers'. This important contribution of Professor Tomalia opened a new research field involving nanotechnological approaches. From then on, many groups have been using PAMAM for diverse applications in many areas, including biomedical applications. The possibility of either linking drugs and bioactive compounds, or entrapping them into the dendrimer frame can improve many relevant biological properties, such as bioavailability, solubility, and selectivity. Directing groups to reach selective delivery in a specific organ is one of the advanced applications of PAMAM. In this review, structural and safety aspects of PAMAM and its derivatives are discussed, and some relevant applications are briefly presented. Emphasis has been given to gene delivery and targeting drugs, as advanced delivery systems using PAMAM and an incentive for its use on neglected diseases are briefly mentioned.

Therapeutic Effects of Topical 8-Oxo-2'-deoxyguanosine on Ethanol-Induced Ocular Chemical Injury Models

PURPOSE

To evaluate the therapeutic effects of topical 8-oxo-2'-deoxyguanosine (8-oxo-dG) on experimental ocular chemical injury models.

METHODS

We created ocular chemical injury models with 8-week-old BALB/c mice (n = 70) by applying 100% ethanol; the mice were then treated with 8-oxo-dG eye drops 10 and 5 mg/mL and phosphate-buffered saline (PBS) twice daily. After 7 days, clinical findings such as corneal integrity, clarity, and neovascularization were assessed. Histology, immunohistochemistry findings, and inflammatory cytokine levels using real-time polymerase chain reactions in the corneas of the mice were also analyzed.

RESULTS

Topical application of 8-oxo-dG eye drops resulted in a significant improvement of epithelial defects and clarity, dose dependently (each P < 0.001). Inflammatory cell infiltration and corneal stromal edema were also decreased in the 8-oxo-dG-treated mice compared with PBS-treated controls, based on hematoxylin and eosin staining. The expressions of F4/80 and neutrophil elastase-positive inflammatory cells and IL-1 and TNF-α cytokine levels were significantly reduced in the 8-oxo-dG group compared with the PBS group (each P < 0.01).

CONCLUSIONS

Topical 8-oxo-dG application showed an excellent therapeutic effect in ocular chemical injury models by suppressing inflammation.

Subconjunctival dendrimer-drug therapy for the treatment of dry eye in a rabbit model of induced autoimmune dacryoadenitis

PURPOSE

To investigate the efficacy of a single subconjunctival injection of dendrimer-dexamethasone conjugate in a rabbit model of induced autoimmune dacryoadenitis (AID).

METHODS

Dendrimer biodistribution after subconjunctival injection in AID animals was evaluated using Cy5-labelled dendrimer (D-Cy5) and confocal microscopy. Diseased animals were treated with free dexamethasone (Free-Dex), dendrimer-dexamethasone (D-Dex), or saline via a single subconjunctival injection. The efficacy was evaluated using various clinical evaluations, such as Schirmer's test, tear breakup time (TBUT), and fluorescein and rose Bengal staining. Histopathology was evaluated by H&E staining and immunostaining. Levels of inflammatory cytokines and aquaporin proteins in the LGs were determined by real-time PCR.

RESULTS

Subconjunctivally administered dendrimers selectively localized in the inflamed LGs, and were taken up by the infiltrating cells. At two weeks post single dose-treatment, the D-Dex group showed improved clinical evaluations. No significant changes were observed in other groups. H&E staining demonstrated less inflammatory cell infiltration and fewer atrophic acini in D-Dex group, compared to those treated with saline or Free-Dex. Immunohistochemistry demonstrated that the intensity of CD-18 (+) and RTLA (+) was weaker in LGs in the D-Dex group than in other treatment groups. Pro-inflammatory gene expression levels of MMP9, IL6, IL8, and TNFα were significantly decreased in the D-Dex group compared to the Free-Dex and saline group.

CONCLUSIONS

The dendrimer exhibits pathology-dependent biodistribution in the inflamed LGs. Subconjunctivally administered D-Dex suppressed LG inflammation, leading to partial recovery of LG function with clinical improvement in induced AID. Sjögren's patients may benefit from this targeted nanomedicine approach.

Preferential and Increased Uptake of Hydroxyl-Terminated PAMAM Dendrimers by Activated Microglia in Rabbit Brain Mixed Glial Culture

Polyamidoamine (PAMAM) dendrimers are multifunctional nanoparticles with tunable physicochemical features, making them promising candidates for targeted drug delivery in the central nervous system (CNS). Systemically administered dendrimers have been shown to localize in activated glial cells, which mediate neuroinflammation in the CNS. These dendrimers delivered drugs specifically to activated microglia, producing significant neurological improvements in multiple brain injury models, including in a neonatal rabbit model of cerebral palsy. To gain further insight into the mechanism of dendrimer cell uptake, we utilized an in vitro model of primary glial cells isolated from newborn rabbits to assess the differences in hydroxyl-terminated generation 4 PAMAM dendrimer (D4-OH) uptake by activated and non-activated glial cells. We used fluorescently-labelled D4-OH (D-Cy5) as a tool for investigating the mechanism of dendrimer uptake. D4-OH PAMAM dendrimer uptake was determined by fluorescence quantification using confocal microscopy and flow cytometry. Our results indicate that although microglial cells in the mixed cell population demonstrate early uptake of dendrimers in this in vitro system, activated microglia take up more dendrimer compared to resting microglia. Astrocytes showed delayed and limited uptake. We also illustrated the differences in mechanism of uptake between resting and activated microglia using different pathway inhibitors. Both resting and activated microglia primarily employed endocytotic pathways, which are enhanced in activated microglial cells. Additionally, we demonstrated that hydroxyl terminated dendrimers are taken up by primary microglia using other mechanisms including pinocytosis, caveolae, and aquaporin channels for dendrimer uptake.

A Ultrasensitive Near-Infrared Fluorescent Probe Reveals Pyroglutamate Aminopeptidase 1 Can Be a New Inflammatory Cytokine

Previous study showed that pyroglutamate aminopeptidase 1 (PGP-1) has a relationship with the immune response in cells. However, whether PGP-1 is involved in inflammatory response in vivo and can serve as a new inflammatory cytokine are still unclear. To address these issues, a new near-infrared fluorescent probe, which exhibits high selectivity and super sensitivity, is developed. With this probe, the up-regulation of PGP-1 (evidenced by western blot) in BALB/c mice legs and livers under the stimulation of two main immunopotentiators is revealed for the first time. The occurrence of inflammatory process (including tissue necrosis) in mice is determined by up-regulation of tumor necrosis factor-α and hematoxylin-eosin staining. Interestingly, it is revealed for the first time that knocking down PGP-1 leads to the weakness of inflammatory process in RAW264.7 cells. These new findings suggest that PGP-1 is indeed involved in inflammatory response in vivo and can be a new inflammatory cytokine.

Dendrimer-mediated delivery of N-acetyl cysteine to microglia in a mouse model of Rett syndrome

Background

Rett syndrome (RTT) is a pervasive developmental disorder that is progressive and has no effective cure. Immune dysregulation, oxidative stress, and excess glutamate in the brain mediated by glial dysfunction have been implicated in the pathogenesis and worsening of symptoms of RTT. In this study, we investigated a new nanotherapeutic approach to target glia for attenuation of brain inflammation/injury both in vitro and in vivo using a Mecp2-null mouse model of Rett syndrome.

Methods

To determine whether inflammation and immune dysregulation were potential targets for dendrimer-based therapeutics in RTT, we assessed the immune response of primary glial cells from Mecp2-null and wild-type (WT) mice to LPS. Using dendrimers that intrinsically target activated microglia and astrocytes, we studied N-acetyl cysteine (NAC) and dendrimer-conjugated N-acetyl cysteine (D-NAC) effects on inflammatory cytokines by PCR and multiplex assay in WT vs Mecp2-null glia. Since the cysteine-glutamate antiporter (Xc⁻) is upregulated in Mecp2-null glia when compared to WT, the role of Xc⁻ in the uptake of NAC and l-cysteine into the cell was compared to that of D-NAC using BV2 cells in vitro. We then assessed the ability of D-NAC given systemically twice weekly to Mecp2-null mice to improve behavioral phenotype and lifespan.

Results

We demonstrated that the mixed glia derived from Mecp2-null mice have an exaggerated inflammatory and oxidative stress response to LPS stimulation when compared to WT glia. Expression of Xc⁻ was significantly upregulated in the Mecp2-null glia when compared to WT and was further increased in the presence of LPS stimulation. Unlike NAC, D-NAC bypasses the Xc⁻ for cell uptake, increasing intracellular GSH levels while preventing extracellular glutamate release and excitotoxicity. Systemically administered dendrimers were localized in microglia in Mecp2-null mice, but not in age-matched WT littermates. Treatment with D-NAC significantly improved behavioral outcomes in Mecp2-null mice, but not survival.

Conclusions

These results suggest that delivery of drugs using dendrimer nanodevices offers a potential strategy for targeting glia and modulating oxidative stress and immune responses in RTT.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1004-5) contains supplementary material, which is available to authorized users.

Effects of major parameters of nanoparticles on their physical and chemical properties and recent application of nanodrug delivery system in targeted chemotherapy

Chemotherapy is still one of the main cancer therapy treatments, but the curative effect of chemotherapy is relatively low, as such the development of a new cancer treatment is highly desirable. The gradual maturation of nanotechnology provides an innovative perspective not only for cancer therapy but also for many other applications. There are a diverse variety of nanoparticles available, and choosing the appropriate carriers according to the demand is the key issue. The performance of nanoparticles is affected by many parameters, mainly size, shape, surface charge, and toxicity. Using nanoparticles as the carriers to realize passive targeting and active targeting can improve the efficacy of chemotherapy drugs significantly, reduce the mortality rate of cancer patients, and improve the quality of life of patients. In recent years, there has been extensive research on nanocarriers. In this review, the effects of several major parameters of nanoparticles on their physical and chemical properties are reviewed, and then the recent progress in the application of several commonly used nanoparticles is presented.

Dendrimers for Ocular Drug Delivery

Existing methods of administering ocular drugs are limited in either their safety or efficiency. Nanomedicine therapies have the potential to address this deficiency by creating vehicles that can control drug biodistribution. Dendrimers are synthetic polymeric nanoparticles with a unique highly organized branching structure. In recent years, promising results using dendrimer vehicles to deliver ocular drugs through different routes of administration have been reported. In this review, we briefly summarize these results with emphasis on the dendrimer modifications used to target different ocular structures.