Subconjunctival nano- and microparticles sustain retinal delivery of budesonide, a corticosteroid capable of inhibiting VEGF expression

Biodegradable microspheres come into sight: A promising biomaterial for delivering drug to the posterior segment of the eyeball

Posterior segment disease acts as a major cause of irreversible visual impairments. Successful treatment of posterior segment disease requires the efficient delivery of therapeutic substances to the targeted lesion. However, the complex ocular architecture makes the bioavailability of topically applied drugs extremely low. Invasive delivery approaches like intravitreal injection may cause adverse complications. To enhance the efficiency, several biomedical engineering systems have been developed to increase the penetration efficiency and improve the bioavailability of drugs at the posterior segments. Advantageously, biodegradable microspheres are found to deliver the therapeutic agents in a controlled fashion. The microspheres prepared from novel biomaterials can realize the prolonged release at the posterior segment with minimum side effects. Moreover, it will be degraded automatically into products that are non-toxic to the human body without the necessity of secondary operation to remove the residual polymer matrix. Additionally, biodegradable microspheres have decent thermoplasticity, adjustable hydrophilicity, controlled crystallinity, and high tensile strength, which make them suitable for intraocular delivery. In this review, we introduce the latest advancements in microsphere production technology and elaborate on the biomaterials that are used to prepare microspheres. We discuss systematically the pharmacological characteristics of biodegradable microspheres and compare their potential advantages and limitations in the treatment of posterior segment diseases. These findings would enrich our knowledge of biodegradable microspheres and cast light into the discovery of effective biomaterials for ocular drug delivery.

Affinity-controlled release of rod-derived cone viability factor enhances cone photoreceptor survival

Retinitis pigmentosa (RP) is a group of genetic diseases that results in rod photoreceptor cell degeneration, which subsequently leads to cone photoreceptor cell death, impaired vision and eventual blindness. Rod-derived cone viability factor (RdCVF) is a protein which has two isoforms: a short form (RdCVF) and a long form (RdCVFL) which act on cone photoreceptors in the retina. RdCVFL protects photoreceptors by reducing hyperoxia in the retina; however, sustained delivery of RdCVFL remains challenging. We developed an affinity-controlled release strategy for RdCVFL. An injectable physical blend of hyaluronan and methylcellulose (HAMC) was covalently modified with a peptide binding partner of the Src homology 3 (SH3) domain. This domain was expressed as a fusion protein with RdCVFL, thereby enabling its controlled release from HAMC-binding peptide. Sustained release of RdCVFL was demonstrated for the first time as RdCVFL-SH3 from HAMC-binding peptide for 7 d in vitro. To assess bioactivity, chick retinal dissociates were harvested and treated with the affinity-released recombinant protein from the HAMC-binding peptide vehicle. After 6 d in culture, cone cell viability was greater when cultured with released RdCVFL-SH3 relative to controls. We utilized computational fluid dynamics to model release of RdCVFL-SH3 from our delivery vehicle in the vitreous of the human eye. We demonstrate that our delivery vehicle can prolong the bioavailability of RdCVFL-SH3 in the retina, potentially enhancing its therapeutic effects. Our affinity-based system constitutes a versatile delivery platform for ultimate intraocular injection in the treatment of retinal degenerative diseases. STATEMENT OF SIGNIFICANCE: Retinitis pigmentosa (RP) is the leading cause of inherited blindness in the world. Rod-derived cone viability factor (RdCVF), a novel protein paracrine factor, is effective in preclinical models of RP. To extend its therapeutic effects, we developed an affinity-controlled release strategy for the long form of RdCVF, RdCVFL. We expressed RdCVFL as a fusion protein with an Src homology 3 domain (SH3). We then utilized a hydrogel composed of hyaluronan and methylcellulose (HAMC) and modified it with SH3 binding peptides to investigate its release in vitro. Furthermore, we designed a mathematical model of the human eye to investigate delivery of the protein from the delivery vehicle. This work paves the way for future investigation of controlled release RdCVF.

In Situ Formation of Injectable Gelatin Methacryloyl (GelMA) Hydrogels for Effective Intraocular Delivery of Triamcinolone Acetonide

A novel drug delivery system designed for intraocular injection, gelatin methacryloyl (GelMA), has attracted much attention due to its sustained-release character and low cytotoxicity. We aimed to explore the sustained drug effect of GelMA hydrogels coupled with triamcinolone acetonide (TA) after injection into the vitreous cavity. The GelMA hydrogel formulations were characterized using scanning electron microscopy, swelling measurements, biodegradation, and release studies. The biological safety effect of GelMA on human retinal pigment epithelial cells and retinal conditions was verified by in vitro and in vivo experiments. The hydrogel exhibited a low swelling ratio, resistance to enzymatic degradation, and excellent biocompatibility. The swelling properties and in vitro biodegradation characteristics were related to the gel concentration. Rapid gel formation was observed after injection, and the in vitro release study confirmed that TA-hydrogels have slower and more prolonged release kinetics than TA suspensions. In vivo fundus imaging, optical coherence tomography measurements of retinal and choroid thickness, and immunohistochemistry did not reveal any apparent abnormalities of retinal or anterior chamber angle, and ERG indicated that the hydrogel had no impact on retinal function. The GelMA hydrogel implantable intraocular device exhibited an extended duration, in situ polymerization, and support cell viability, making it an attractive, safe, and well-controlled platform for treating the posterior segment diseases of the eye.

Fabrication and Characterisation of 3D-Printed Triamcinolone Acetonide-Loaded Polycaprolactone-Based Ocular Implants

Triamcinolone acetonide (TA) is a corticosteroid that has been used to treat posterior segment eye diseases. TA is injected intravitreally in the management of neovascular disorders; however, frequent intravitreal injections result in many potential side effects and poor patient compliance. In this work, a 3D bioprinter was used to prepare polycaprolactone (PCL) implants loaded with TA. Implants were manufactured with different shapes (filament-, rectangular-, and circle-shaped) and drug loadings (5, 10, and 20%). The characterisation results showed that TA was successfully mixed and incorporated within the PCL matrix without using solvents, and drug content reached almost 100% for all formulations. The drug release data demonstrate that the filament-shaped implants (SA/V ratio~7.3) showed the highest cumulative drug release amongst all implant shapes over 180 days, followed by rectangular- (SA/V ratio~3.7) and circle-shaped implants (SA/V ratio~2.80). Most implant drug release data best fit the Korsmeyer−Peppas model, indicating that diffusion was the prominent release mechanism. Additionally, a biocompatibility study was performed; the results showed >90% cell viability, thus proving that the TA-loaded PCL implants were safe for ocular application.

Current Treatments and Innovations in Diabetic Retinopathy and Diabetic Macular Edema

Diabetic retinopathy (DR) is one of the leading causes of blindness worldwide. Multiple treatment options have been used over time to attempt to modify the natural progression of the disease in both proliferative diabetic retinopathy (PDR) and diabetic macular edema (DME). These two retinal complications are the result of microvascular occlusions and vascular hyperpermeability and are considered one of the leading causes of irreversible blindness in patients of working age. It is now well demonstrated that PDR and DME are associated with increased levels of inflammatory and pro-angiogenic factors in the ocular compartment. To date, laser photocoagulation, vascular endothelial growth factor (VEGF) inhibitors, and corticosteroids have demonstrated efficacy in their treatment in large randomized controlled trials and in real-life observational studies. This manuscript aims to provide a comprehensive review of current treatments, including the main drugs used in diabetic pathologic manifestations, as well as new therapeutic alternatives, such as extended-release intraocular devices.

Repurpose but also (nano)-reformulate! The potential role of nanomedicine in the battle against SARS-CoV2

The coronavirus disease-19 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has taken the world by surprise. To date, a worldwide approved treatment remains lacking and hence in the context of rapid viral spread and the growing need for rapid action, drug repurposing has emerged as one of the frontline strategies in the battle against SARS-CoV2. Repurposed drugs currently being evaluated against COVID-19 either tackle the replication and spread of SARS-CoV2 or they aim at controlling hyper-inflammation and the rampaged immune response in severe disease. In both cases, the target for such drugs resides in the lungs, at least during the period where treatment could still provide substantial clinical benefit to the patient. Yet, most of these drugs are administered systemically, questioning the percentage of administered drug that actually reaches the lung and as a consequence, the distribution of the remainder of the dose to off target sites. Inhalation therapy should allow higher concentrations of the drug in the lungs and lower concentrations systemically, hence providing a stronger, more localized action, with reduced adverse effects. Therefore, the nano-reformulation of the repurposed drugs for inhalation is a promising approach for targeted drug delivery to lungs. In this review, we critically analyze, what nanomedicine could and ought to do in the battle against SARS-CoV2. We start by a brief description of SARS-CoV2 structure and pathogenicity and move on to discuss the current limitations of repurposed antiviral and immune-modulating drugs that are being clinically investigated against COVID-19. This account focuses on how nanomedicine could address limitations of current therapeutics, enhancing the efficacy, specificity and safety of such drugs. With the appearance of new variants of SARS-CoV2 and the potential implication on the efficacy of vaccines and diagnostics, the presence of an effective therapeutic solution is inevitable and could be potentially achieved via nano-reformulation. The presence of an inhaled nano-platform capable of delivering antiviral or immunomodulatory drugs should be available as part of the repertoire in the fight against current and future outbreaks.

A non-invasive nanoparticle-based sustained dual-drug delivery system as an eyedrop for endophthalmitis

Endophthalmitis is an infectious disease that affects the entire eye spreading to the internal retinal layers and the vitreous and causes severe sight-threatening conditions. Current treatment strategies rely on intraocular injections of antibiotics that are invasive, may lead to procedural complications and, ultimately, blindness. In this study, we developed a non-invasive strategy as an eyedrop containing nanoparticle-based dual-drug delivery system in which the hydrophobic poly-L-lactide core was loaded with azithromycin or triamcinolone acetonide, and the hydrophilic shell was made of chitosan. The developed nanoparticles were ~200-250 nm in size, spherical in shape, moderately hydrophilic, lysozyme tolerant, cytocompatible, and hemocompatible. Application of these chitosan-coated nanoparticles as eye drops to C57BL/6 mice showed higher bioavailability in choroid and retina when compared to the uncoated nanoparticles. The delivery system showed sustained release of drug for 300 h and exhibited antimicrobial effects against Gram-positive and Gram-negative bacteria and anti-inflammatory effects on activated microglial cells. Interestingly, the combination of the nanoparticles loaded with azithromycin and the nanoparticles loaded with triamcinolone acetonide acted synergistically as compared to either of the nanoparticles/drugs alone. Overall, the developed dual-drug delivery system is non-invasive, has antimicrobial and anti-inflammatory effects, and shows potential as an eye drop formulation against endophthalmitis.

Recent trends in drug-delivery systems for the treatment of diabetic retinopathy and associated fibrosis

Diabetic retinopathy is a frequent microvascular complication of diabetes and a major cause of visual impairment. In advanced stages, the abnormal neovascularization can lead to fibrosis and subsequent tractional retinal detachment and blindness. The low bioavailability of the drugs at the target site imposed by the anatomic and physiologic barriers within the eye, requires long term treatments with frequent injections that often compromise patient's compliance and increase the risk of developing more complications. In recent years, much effort has been put towards the development of new drug delivery platforms aiming to enhance their permeation, to prolong their retention time at the target site and to provide a sustained release with reduced toxicity and improved efficacy. This review provides an overview of the etiology and pathophysiology of diabetic retinopathy and current treatments. It addresses the specific challenges associated to the different ocular delivery routes and provides a critical review of the most recent developments made in the drug delivery field.

Extraocular, periocular, and intraocular routes for sustained drug delivery for glaucoma

Although once daily anti-glaucoma drug therapy is a current clinical reality, most therapies require multiple dosing and there is an unmet need to develop convenient, safe, and effective sustained release drug delivery systems for long-term treatment to improve patient adherence and outcomes. One of the first sustained release drug delivery systems was approved for the reduction of intraocular pressure in glaucoma patients. It is a polymeric reservoir-type insert delivery system, Ocusert™, placed under the eyelid and on the ocular surface for zero-order drug release over one week. The insert, marketed in two strengths, released pilocarpine on the eye surface. While many clinicians appreciated this drug product, it was eventually discontinued. No similar sustained release non-invasive drug delivery system has made it to the market to date for treating glaucoma. Drug delivery systems under development include punctal plugs, ring-type systems, contact lenses, implants, microspheres, nanospheres, gels, and other depot systems placed in the extraocular, periocular, or intraocular regions including intracameral, supraciliary, and intravitreal spaces. This article discusses the advantages and disadvantages of the various routes of administration and delivery systems for sustained glaucoma therapy. It also provides the reader with some examples and discussion of drug delivery systems that could potentially be applied for glaucoma treatment. Interestingly, one intracamerally injected implant, Durysta™, was approved recently for sustained intraocular pressure reduction. However, long-term acceptance of such devices has yet to be established. The ultimate success of the delivery system will depend on efficacy relative to eye drop dosing, safety, reimbursement options, and patient acceptance. Cautious development efforts are warranted considering prior failed approaches for sustained glaucoma drug delivery. Neuroprotective approaches for glaucoma therapy including cell, gene, protein, and drug-combination therapies, mostly administered intravitreally, are also rapidly progressing towards assessment in humans.

Advanced nanodelivery platforms for topical ophthalmic drug delivery

Conventional eye drops have several limitations, including the need for multiple applications per dose, hourly based dosage regiments, and suboptimal ocular bioavailability (<5%). The efficacy of topical ophthalmic medications can be significantly improved by controlling their contact time with the adherent mucin layer and by inducing sustained release properties, thus allowing for a prolonged contact time of the drug with the ocular tissues, which eventually will lead to improved drug bioavailability and a significant decrease in the frequency of eyedrop instillation. In this review, we critically highlight recent and innovative nanodrug delivery platforms, with a primary focus on the integration of nanotechnology, biomaterials, and polymer chemistry to facilitate precise spatial and temporal control over sustained drug release to the cornea.

Novel Needle for Intravitreal Drug Delivery: Comparative Study of Needle Tip Aspirates, Injection Stream and Penetration Forces

Purpose

To study the efficacy of a novel needle for intravitreal injection (IVI) in comparison to the conventional needle under experimental conditions.

Methods

The newly designed 30-gauge (G) needle (NDN) (EP 18158 542.3, patent pending) with occluded outer orifice and a side port for drug delivery was compared to the conventional standard hypodermic 30 G needle for IVI (SHN). An animal study to obtain needle tip aspirates was performed on 10 albino rat eyes. During IVIs, cellular content, which was cut by the needle tip, was aspirated. Cellular material was studied in regard to cell types and their quantity. The injection stream was studied using trypan blue dye in vitro and pig cadaver eyes. The penetration force was tested on polyurethane Testing Foil Strips PU 04 (Melab, Leonberg, Germany) by applying a velocity of 100 mm/min. The results were analyzed using descriptive statistics, correlation matrices and t-test methods with p<0.05 as statistically significant.

Results

Cytological analysis of the needle aspirates showed the presence of cellular content in each case. The amount of conjunctival, ciliary body epithelial cells and granulated basophilic protein sediments (sign of cellular damage) in the case of the NDN tips was significantly lower compared to the SHN. The average penetration force of the NDN was 0.791 N, and in the case of the SHN was 0.566 N. The injection stream study revealed a difference in the initial injection phase between the two needle types, although the diffuse filling of the vitreous area which surrounded the needle tip appeared to be similar.

Discussion

The NDN demonstrated superior performance with regard to a significantly reduced number of cells being captured by the needle tip. Delivery of the injected fluid into the vitreous cavity was comparable. In order to investigate superior properties of the NDN needle design, further studies with improved prototypes would be necessary.

Smart nano-micro platforms for ophthalmological applications: The state-of-the-art and future perspectives

Smart nano-micro platforms have been extensively applied for diverse biomedical applications, mostly focusing on cancer therapy. In comparison with conventional nanotechnology, the smart nano-micro matrix can exhibit specific response to exogenous or endogenous triggers, and thus can achieve multiple functions e.g. site-specific drug delivery, bio-imaging and detection of bio-molecules. These intriguing techniques have expanded into ophthalmology in recent years, yet few works have been summarized in this field. In this work, we provide the state-of-the-art of diverse nano-micro platforms based on both the conventional materials (e.g. natural or synthetic polymers, lipid nanomaterials, metal and metal oxide nanoparticles) and emerging nanomaterials (e.g. up-conversion nanoparticles, quantum dots and carbon materials) in ophthalmology, with some smart nano/micro platformers highlighted. The common ocular diseases studied in the field of nano-micro systems are firstly introduced, and their therapeutic method and the related drawback in clinic treatment are presented. The recent progress of different materials for diverse ocular applications is then demonstrated, with the representative nano- and micro-systems highlighted in detail. At last, an in-depth discussion on the clinical translation challenges faced in this field and the future direction are provided. This review would allow the researchers to design more smart nanomedicines in a more rational manner for specific ophthalmology applications.

Ocular Drug Delivery to the Retina: Current Innovations and Future Perspectives

Treatment options for retinal diseases, such as neovascular age-related macular degeneration, diabetic retinopathy, and retinal vascular disorders, have markedly expanded following the development of anti-vascular endothelial growth factor intravitreal injection methods. However, because intravitreal treatment requires monthly or bimonthly repeat injections to achieve optimal efficacy, recent investigations have focused on extended drug delivery systems to lengthen the treatment intervals in the long term. Dose escalation and increasing molecular weight of drugs, intravitreal implants and nanoparticles, hydrogels, combined systems, and port delivery systems are presently under preclinical and clinical investigations. In addition, less invasive techniques rather than intravitreal administration routes, such as topical, subconjunctival, suprachoroidal, subretinal, and trans-scleral, have been evaluated to reduce the treatment burden. Despite the latest advancements in the field of ophthalmic pharmacology, enhancing drug efficacy with high ocular bioavailability while avoiding systemic and local adverse effects is quite challenging. Consequently, despite the performance of numerous in vitro studies, only a few techniques have translated to clinical trials. This review discusses the recent developments in ocular drug delivery to the retina, the pharmacokinetics of intravitreal drugs, efforts to extend drug efficacy in the intraocular space, minimally invasive techniques for drug delivery to the retina, and future perspectives in this field.

Interphotoreceptor Retinoid-Binding Protein (IRBP) in Retinal Health and Disease

Interphotoreceptor retinoid-binding protein (IRBP), also known as retinol binding protein 3 (RBP3), is a lipophilic glycoprotein specifically secreted by photoreceptors. Enriched in the interphotoreceptor matrix (IPM) and recycled by the retinal pigment epithelium (RPE), IRBP is essential for the vision of all vertebrates as it facilitates the transfer of retinoids in the visual cycle. It also helps to transport lipids between the RPE and photoreceptors. The thiol-dependent antioxidant activity of IRBP maintains the delicate redox balance in the normal retina. Thus, its dysfunction is suspected to play a role in many retinal diseases. We have reviewed here the latest research on IRBP in both retinal health and disease, including the function and regulation of IRBP under retinal stress in both animal models and the human retina. We have also explored the therapeutic potential of targeting IRBP in retinal diseases. Although some technical barriers remain, it is possible that manipulating the expression of IRBP in the retina will rescue or prevent photoreceptor degeneration in many retinal diseases.

Shear-Thinning Viscous Materials for Subconjunctival Injection of Microparticles

While drug-loaded microparticles (MPs) can serve as drug reservoirs for sustained drug release and therapeutic effects, needle clogging by MPs poses a challenge for ocular drug delivery via injection. Two polymers commonly used in ophthalmic procedures-hyaluronic acid (HA) and methylcellulose (MC)-have been tested for their applicability for ocular injections. HA and MC were physically blended with sunitinib malate (SUN)-loaded PLGA MPs for subconjunctival (SCT) injection into rat eyes. The HA and MC viscous solutions facilitated injection through fine-gauged needles due to their shear-thinning properties as shown by rheological characterizations. The diffusion barrier presented by HA and MC reduced burst drug release and extended overall release from MPs. The significant level of MP retention in the conjunctiva tissue post-operation confirmed the minimal leakage of MPs following injection. The safety of HA and MC for ocular applications was demonstrated histologically.

Fabrication, Optimization, and In Vitro and In Vivo Characterization of Intra-vitreal Implant of Budesonide Generally Made of PHBV

Drug delivery to vitreous in comparison with drug delivery to the other parts of the eye is complicated and challenging due to the existence of various anatomical and physiological barriers. Developing injectable intra-vitreal implant could be beneficial in this regard. Herein, poly(hydroxybutyrate-co-valerate) (PHBV) implants were fabricated and optimized using response surface method for budesonide (BZ) delivery. The acquired implants were characterized in regard to the stability of the ingredients during fabrication process, drug loading amount, and drug release pattern (in PBS-HA-A and in vitreous medium). According to this research and statistical analysis performed, first HV% (hydroxyvalerate) then molecular weight and ratio of PEG as pore former affect respectively release rate and burst strength of BZ with different coefficients. Drug release profile in rabbit eye correlated well with that of in vitro (R² = 0.9861, p ˂ 0.0001). No significant changes were seen in ERG waves, intraocular pressure, and histological studies during the in vivo part of the project. Using 8% HV, 20% PEG/PHBV, and higher molecular weight PEG (i.e., 6000), the optimum formulation was achieved. Toxicity and biocompatibility of the optimized formulation, which were evaluated in vivo, indicated the suitability of design implant for intra-vitreal BZ delivery. Grapical abstract.

Micro-interaction of mucin tear film interface with particles: The inconsistency of pharmacodynamics and precorneal retention of ion-exchange, functionalized, Mt-embedded nano- and microparticles

Physiological reflexes and anatomical barriers render traditional eye drop delivery inefficient. We previously reported that drug-loaded nanoparticles and microspheres prepared from montmorillonite and Eudragit polymers exhibited good sustained-release and lowered intraocular pressure. Here, we compared the performance of optimized formulations to select the most suitable formulation for glaucoma therapy. We found that the microspheres had much higher encapsulation efficiency and drug loading than nanoparticles. Moreover, cytocompatibility experiments demonstrated that nanoparticles showed more severe cytotoxicity than microspheres, probably due to their smaller particles, enhanced cell uptake, and intracellular solubility. Interestingly, the pre-corneal retention time of nanoparticles reflected a clear advantage over microspheres, while the duration of the pharmacological effect of nanoparticles was not as good as that of microspheres: compared with the nanoparticle depressurization duration of only 8 h, the microspheres continuously depressurized for 12 h. The slower release of the microspheres and its micro-interaction mechanism with the discontinuous mucin layer of the tear film led to the inconsistency between duration of pharmacodynamics and fluorescence ocular retention time. In summary, the lower cytotoxicity and longer pharmacological effect of microspheres indicate their potential advantages for glaucoma applications.

Nanoformulations for Ocular Delivery of Drugs - A Patent Perspective

Efficient delivery of ocular therapeutics with improved efficacy, enhanced bioavailability, and acceptable patient compliance presents unique challenges. This can be attributed to the presence of protective mechanisms, physicobiological barriers, and structural obstacles in the eye. Nanotherapeutic interventions have been explored extensively over the past few years to overcome these limitations. The present review focusses on the nanoformulations developed for the diagnosis and treatment of various ocular diseases besides providing an in-depth insight into the patents reported for the same.

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.

Modification of Collagen/Gelatin/Hydroxyethyl Cellulose-Based Materials by Addition of Herbal Extract-Loaded Microspheres Made from Gellan Gum and Xanthan Gum

Because consumers are nowadays focused on their health and appearance, natural ingredients and their novel delivery systems are one of the most developing fields of pharmacy, medicine, and cosmetics. The main goal of this study was to design, prepare, and characterize composite materials obtained by incorporation of microspheres into the porous polymer materials consisting of collagen, gelatin, and hydroxyethyl cellulose. Microspheres, based on gellan gum and xanthan gum with encapsulated Calendula officinalis flower extract, were produced by two methods: extrusion and emulsification. The release profile of the extract from both types of microspheres was compared. Then, obtained microparticles were incorporated into polymeric materials with a porous structure. This modification had an influence on porosity, density, swelling properties, mechanical properties, and stability of materials. Besides, in vitro tests were performed using mouse fibroblasts. Cell viability was assessed with the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The obtained materials, especially with microspheres prepared by emulsion method, can be potentially helpful when designing cosmetic forms because they were made from safely for skin ingredients used in this industry and the herbal extract was successfully encapsulated into microparticles.

Effects of shell thickness of hollow poly(lactic acid) nanoparticles on sustained drug delivery for pharmacological treatment of glaucoma

Structural designing of carriers with extended drug release profiles is critically important for achieving long-acting drug delivery systems toward efficient managements of chronic diseases. Here, we present a strategy to exploit the effects of the shell thickness of hollow poly(lactic acid) nanoparticles (HPLA NPs) in sustained glaucoma therapy. Formulations based on pilocarpine-loaded HPLA NPs with tailorable shell thickness ranging from 10 to 100 nm were shown to be highly compatible with human lens epithelial cells in vitro and with rabbit eyes in vivo. Specifically, shell thickness regulated the release of pilocarpine, with thick shells (~70 to 100 nm) providing sustained drug release performance but limited drug-loading efficiency, whereas ultrathin shells (~10 nm) induced the opposite effects. Remarkably, moderately thick shells (~40 nm) showed the most effective release profile of pilocarpine (above the therapeutic levels of ~10 µg/mL for over 56 days). In a rabbit model of glaucoma, single intracameral administration of an HPLA NP-based formulation with shell thickness of ~40 nm sustainably alleviated ocular hypertension for over 56 days, consequently protecting the structural integrity of the corneal endothelium, preserving the electrophysiological functions of the retina, and attenuating retinal and optic nerve degeneration in progressively glaucomatous eyes. The findings therefore implied a promising use of shell thickness effects in the development of long-acting drug delivery systems for pharmacological treatment of chronic ocular diseases. STATEMENT OF SIGNIFICANCE: Owing to their large surface areas and modifiable structures, nanoparticles have been considered as a promising platform for drug delivery; however, achieving drug nanocarrier systems with reduced burst release and sustained therapeutic efficacy remains challenges. This work presents the first report on rational design of hollow poly(lactic acid) nanocarriers for tailoring the structure-property-function relationships toward effective treatment of glaucoma. The shell thickness of the hollow nanocarriers is demonstrated to have influential impacts on pilocarpine encapsulation efficiency and release profile, indicating that the most sustained delivery performance (maintaining the release of pilocarpine above therapeutic level over 56 days) can be obtained for the polymeric nanoparticles with moderate shell thickness of ~40 nm.

Effect of Particle Size and Viscosity of Suspensions on Topical Ocular Bioavailability of Budesonide, a Corticosteroid

Purpose: To determine the effect of particle size and viscosity of suspensions on topical ocular bioavailability of budesonide, a corticosteroid drug. Methods: Budesonide microparticle and nanoparticle (MP and NP) suspensions were prepared with or without homogenization and microfluidization. Using different grades of hydroxyl propyl methyl cellulose, low viscosity NP (NP-LV) and low and high viscosity MP (MP-LV and MP-HV) were prepared. Suspensions were characterized for particle size, viscosity, and osmolality. Budesonide suspensions were administered topically to rabbits and aqueous humor was collected and analyzed for budesonide. Budesonide C_max, t_max, and the area under the concentration time curve (AUC _(0-6h)) values were determined. The geometric mean ratio of AUC and bioequivalence was evaluated using a bootstrap method. Results: The particle sizes for NP and MP were ∼700 and 2,000 nm. The viscosities for low and HV formulations were ∼5 and 50 cP. The geometric mean budesonide C_max values for the suspensions NP-LV, MP-LV, and MP-HV were 0.22, 0.22, and 0.31 μg/g, t_max values were 0.67, 0.60 and 0.53 h, and AUC_0-6h values were 0.72, 0.53, and 0.95 μg h/g, respectively. Bootstrap analysis indicated that the 90% confidence intervals of the geometric mean ratio of AUC_0-6h values were 1.00-1.74 (MP-HV vs. NP-LV), 0.57-0.96 (MP-LV vs. NP-LV), and 0.45-0.70 (MP-LV vs. MP-HV). Conclusions: The 3 budesonide suspensions assessed in this study were not bioequivalent. Results suggested that an increase in viscosity improves the bioavailability of budesonide from the microsuspension formulation.

Drug Delivery to the Posterior Segment of the Eye: Biopharmaceutic and Pharmacokinetic Considerations

The treatment of the posterior-segment ocular diseases, such as age-related eye diseases (AMD) or diabetic retinopathy (DR), present a challenge for ophthalmologists due to the complex anatomy and physiology of the eye. This specialized organ is composed of various static and dynamic barriers that restrict drug delivery into the target site of action. Despite numerous efforts, effective intraocular drug delivery remains unresolved and, therefore, it is highly desirable to improve the current treatments of diseases affecting the posterior cavity. This review article gives an overview of pharmacokinetic and biopharmaceutics aspects for the most commonly-used ocular administration routes (intravitreal, topical, systemic, and periocular), including information of the absorption, distribution, and elimination, as well as the benefits and limitations of each one. This article also encompasses different conventional and novel drug delivery systems designed and developed to improve drug pharmacokinetics intended for the posterior ocular segment treatment.

The humanin peptide mediates ELP nanoassembly and protects human retinal pigment epithelial cells from oxidative stress

Humanin (HN) is a hydrophobic 24-amino acid peptide derived from mitochondrial DNA that modulates cellular responses to oxidative stress and protects human retinal pigment epithelium (RPE) cells from apoptosis. To solubilize HN, this report describes two genetically-encoded fusions between HN and elastin-like polypeptides (ELP). ELPs provide steric stabilization and/or thermo-responsive phase separation. Fusions were designed to either remain soluble or phase separate at the physiological temperature of the retina. Interestingly, the soluble fusion assembles stable colloids with a hydrodynamic radius of 39.1 nm at 37°C. As intended, the thermo-responsive fusion forms large coacervates (>1,000 nm) at 37°C. Both fusions bind human RPE cells and protect against oxidative stress-induction of apoptosis (TUNEL, caspase-3 activation). Their activity is mediated through STAT3; furthermore, STAT3 inhibition eliminates their protection. These findings suggest that HN polypeptides may facilitate cellular delivery of biodegradable nanoparticles with potential protection against age-related diseases, including macular degeneration.

Polymeric Nanoparticles: A Promising Tool to Enhance the Solubility of Poorly Water Soluble Drug

Objective:

The objective of this study was to entrap water-insoluble drug itraconazole into polymer to form drug entrapped nanoparticles by using simple formulation strategy and characterize them for various in vitro properties.

Method:

Itraconazole (ITZ) encapsulated Eudragit E 100 nanoparticles (IEENs) were formulated by emulsification solvent evaporation technique.

Results:

Developed IEENs were evaluated for entrapment efficiency, particle size, polydispersity index, and drug release profile. It was clear that drug polymer ratio along with homogenization speed are the factors affecting droplet size of an emulsion. Evaluation was done by HPLC at 263nm. DSC, XRD studies were carried out. The in vitro antifungal study of nanoparticles suggested that they are more effective in inhibiting growth of Candida albicans.

Conclusion:

The results from this study suggest the potential use of IEENs to provide a possible way of improving solubility and thus oral absorption of Itraconazole. Thus the study concluded that IEENs have potential to effectively treat the fungal infection.

Micro/Nanoparticle Delivery Systems for Ocular Diseases

Micro- (MPs) and nanoparticles (NPs) have been recently studied for their application in ophthalmic drug delivery. These drug delivery systems are able to circumvent the ocular barriers that currently limit the efficacy of conventional treatments, as well as provide a more sustained release of drug, reducing the frequency of administration and increasing patient compliance. This review summarizes the recent trends in ophthalmic research from conventional treatment to the utilization of MPs and NPs as drug carriers.

Drug-Loaded Biocompatible Nanocarriers Embedded in Poloxamer 407 Hydrogels as Therapeutic Formulations

Hydrogels are three-dimensional networks of hydrophilic polymers able to absorb and retain a considerable amount of water or biological fluid while maintaining their structure. Among these, thermo-sensitive hydrogels, characterized by a temperature-dependent sol–gel transition, have been massively used as drug delivery systems for the controlled release of various bioactives. Poloxamer 407 (P407) is an ABA-type triblock copolymer with a center block of hydrophobic polypropylene oxide (PPO) between two hydrophilic polyethyleneoxide (PEO) lateral chains. Due to its unique thermo-reversible gelation properties, P407 has been widely investigated as a temperature-responsive material. The gelation phenomenon of P407 aqueous solutions is reversible and characterized by a sol–gel transition temperature. The nanoencapsulation of drugs within biocompatible delivery systems dispersed in P407 hydrogels is a strategy used to increase the local residence time of various bioactives at the injection site. In this mini-review, the state of the art of the most important mixed systems made up of colloidal carriers localized within a P407 hydrogel will be provided in order to illustrate the possibility of obtaining a controlled release of the entrapped drugs and an increase in their therapeutic efficacy as a function of the biomaterial used.

Utilization of Apatinib-Loaded Nanoparticles for the Treatment of Ocular Neovascularization

Background:

The current treatment of ocular neovascularization requires frequent intravitreal injections of anti-vascular endothelial growth factor (VEGF) agents that cause severe side effects.

Objective:

The purpose of this study is to prepare and characterize a novel nanoscale delivery system of apatinib for ocular neovascularization. </P><P> Methods: The optimized formulation showed a particle size of 135.04 nm, polydispersity index (PDI) of 0.28 &#177; 0.07, encapsulation efficiency (EE) of 65.92%, zeta potential (ZP) of -23.70 &#177; 8.69 mV, and pH of 6.49 &#177; 0.20. In vitro release was carried out to demonstrate a 3.13-fold increase in the sustainability of apatinib-loaded nanoparticles versus free apatinib solution. </P><P> Result: Cell viability and VEGFA and VEGFR2 expression were analyzed in animal retinal pigment epithelial (ARPE-19) cells.

In situ construction of nanonetworks from transformable nanoparticles for anti-angiogenic therapy

Tumor metastasis as the most common reason of death from cancer has always been a great challenge in both clinical and scientific research, where angiogenesis plays a necessary role. Herein, we report an extracellularly transformable nanomaterial for in situ construction of defensive networks on interaction with vascular endothelial growth factor (VEGF) for anti-angiogenic therapy of tumor. The fibrous networks exhibit transformation-enhanced accumulation and retention (TEAR) effects (over 72 h), and bind and intercept cell-secreted VEGF over particulate and molecular anti-angiogenic agents with high efficiency, leading to anti-angiogenesis. This study demonstrates that angiogenesis is positively related to tumor growth as well as tumor metastasis; the anti-angiogenic therapy inhibits tumor metastasis with an inhibition rate of 65.9%. In addition, this extracellular strategy of transformation may be utilized to bind huge amounts of cell-secreted biomolecules/factors or receptors on cell surfaces and inhibit their functionalities for cancer therapy.

Ocular delivery of proteins and peptides: Challenges and novel formulation approaches

The impact of proteins and peptides on the treatment of various conditions including ocular diseases over the past few decades has been advanced by substantial breakthroughs in structural biochemistry, genetic engineering, formulation and delivery approaches. Formulation and delivery of proteins and peptides, such as monoclonal antibodies, aptamers, recombinant proteins and peptides to ocular tissues poses significant challenges owing to their large size, poor permeation and susceptibility to degradation. A wide range of advanced drug delivery systems including polymeric controlled release systems, cell-based delivery and nanowafers are being exploited to overcome the challenges of frequent administration to ocular tissues. The next generation systems integrated with new delivery technologies are anticipated to generate improved efficacy and safety through the expansion of the therapeutic target space. This review will highlight recent advances in formulation and delivery strategies of protein and peptide based biopharmaceuticals. We will also describe the current state of proteins and peptides based ocular therapy and future therapeutic opportunities.

Microspheres as intraocular therapeutic tools in chronic diseases of the optic nerve and retina

Pathologies affecting the optic nerve and the retina are one of the major causes of blindness. These diseases include age-related macular degeneration (AMD), diabetic retinopathy (DR) and glaucoma, among others. Also, there are genetic disorders that affect the retina causing visual impairment. The prevalence of neurodegenerative diseases of the posterior segment is increased as most of them are related with the elderly. Even with the access to different treatments, there are some challenges in managing patients suffering retinal diseases. One of them is the need for frequent interventions. Also, an unpredictable response to therapy has suggested that different pathways may be playing a role in the development of these diseases. The management of these pathologies requires the development of controlled drug delivery systems able to slow the progression of the disease without the need of frequent invasive interventions, typically related with endophthalmitis, retinal detachment, ocular hypertension, cataract, inflammation, and floaters, among other. Biodegradable microspheres are able to encapsulate low molecular weight substances and large molecules such as biotechnological products. Over the last years, a large variety of active substances has been encapsulated in microspheres with the intention of providing neuroprotection of the optic nerve and the retina. The purpose of the present review is to describe the use of microspheres in chronic neurodegenerative diseases affecting the retina and the optic nerve. The advantage of microencapsulation of low molecular weight drugs as well as therapeutic peptides and proteins to be used as neuroprotective strategy is discussed. Also, a new use of the microspheres in the development of animal models of neurodegeneration of the posterior segment is described.

The Efficacy of Intravitreal Triamcinolone Acetonide on Macular Edema in Branch Retinal Vein Occlusion

PURPOSE

To evaluate the effectiveness of intravitreal triamcinolone acetonide as primary treatment of macular edema in branch retinal vein occlusion.

METHODS

Fifteen eyes of 15 patients with macular edema due to branch retinal vein occlusion (Group 1) who received 8 mg/0.2 ml of intravitreal triamcinolone injection as primary treatment were retrospectively evaluated. The control group (Group 2) consisted of 19 eyes of 19 patients who had received laser treatment for macular edema. The main outcome measures included best-corrected visual acuity, intraocular pressure, and macular edema map values of Heidelberg Retinal Tomograph II.

RESULTS

In Group 1, mean visual acuity improved significantly from a mean logMAR (logarithm of minimal angle of resolution) value of 0.98+/-0.19 at baseline to a maximum of 0.24+/-0.24 during a mean follow-up time of 6.3 months. In the control group, the mean baseline log-MAR visual acuity before laser treatment was 1.02+/-0.22, and it was 0.50+/-0.28 at 6-month examinations. Mean improvement in visual acuity at 1-, 3-, and 6-month examinations was significantly higher in Group 1 when compared with the control group (for each, p<0.001). The mean edema map value of Group 1 significantly decreased by 40% at 6-month examinations when compared with preinjection value (p<0.001). In Group 1, mean increase in intraocular pressure elevation was 19.8% at the 1-month, 26.9% at 3-month, and 5.7% at 6-month visits, but intraocular pressures were under control with topical antiglaucomatous medications.

CONCLUSIONS

Intravitreal triamcinolone acetonide injection may be a new and promising approach as initial therapy for macular edema due to branch retinal vein occlusion.

Improvement in Ocular Bioavailability and Prolonged Delivery of Tobramycin Sulfate Following Topical Ophthalmic Administration of Drug-Loaded Mucoadhesive Microparticles Incorporated in Thermosensitive In Situ Gel

PURPOSE

Conventional topical delivery in hyperacute bacterial conjunctivitis and endophthalmitis is associated with low drug bioavailability due to rapid precorneal clearance. Hence, in the present investigation, an attempt has been made to enhance ocular bioavailability of tobramycin sulfate by formulating drug-loaded microparticles dispersed in thermosensitive in situ gel.

METHODS

Microparticles prepared by emulsion-ionic gelation technique were characterized for drug loading, entrapment efficiency, particle size, surface morphology, and in vitro drug release. Consequently microparticles (F2 prepared with 1.5%w/v chitosan, 0.2%w/v tripolyphosphate, and drug, 30%w/w of polymer) with high drug loading and encapsulation efficiency were dispersed in thermosensitive in situ gel containing poloxamer 407 and varying percentage of chitosan. In situ gel containing drug-loaded microparticles were evaluated for gelation temperature, rheological behavior, mucoadhesive strength, in vitro drug release, in vitro permeation, ocular irritation, and bioavailability in aqueous humor of rabbits.

RESULTS

Formulation containing 17%w/v poloxamer 407 and 0.5%w/v chitosan (P2) gelled at 32°C ± 1.5°C gave pseudoplastic behavior. In vitro permeability of tobramycin from the formulation P2 was found 2-folds greater than eye drops. It also gave significantly higher aqueous humor concentration of tobramycin compared with eye drops with no signs of ocular irritation.

CONCLUSION

Thus, the formulation possesses high potential for treating ocular infections.

Pharmaceutical microscale and nanoscale approaches for efficient treatment of ocular diseases

Efficient treatment of ocular diseases can be achieved thanks to the proper use of ophthalmic formulations based on emerging pharmaceutical approaches. Among them, microtechnology and nanotechnology strategies are of great interest in the development of novel drug delivery systems to be used for ocular therapy. The location of the target site in the eye as well as the ophthalmic disease will determine the route of administration (topical, intraocular, periocular, and suprachoroidal administration) and the most adequate device. In this review, we discuss the use of colloidal pharmaceutical systems (nanoparticles, liposomes, niosomes, dendrimers, and microemulsions), microparticles (microcapsules and microspheres), and hybrid systems (combination of different strategies) in the treatment of ophthalmic diseases. Emphasis has been placed in the therapeutic significance of each drug delivery system for clinical translation.

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.

Combination of nanotechnology with vascular targeting agents for effective cancer therapy

As a young science, nanotechnology promptly integrated into the current oncology practice. Accordingly, various nanostructure particles were developed to reduce drug toxicity and allow the targeted delivery of various diagnostic and therapeutic compounds to the cancer cells. New sophisticated nanosystems constantly emerge to improve the performance of current anticancer modalities. Targeting tumor vasculature is an attractive strategy to fight cancer. Though the idea was swiftly furthered from basic science to the clinic, targeting tumor vasculature had a limited potential in patients, where tumors relapse due to the development of multiple drug resistance and metastasis. The aim of this review is to discuss the advantages of nanosystem incorporation with various vascular targeting agents, including (i) endogen anti-angiogenic agents; (ii) inhibitors of angiogenesis-related growth factors; (iii) inhibitors of tyrosine kinase receptors; (iv) inhibitors of angiogenesis-related signaling pathways; (v) inhibitors of tumor endothelial cell-associated markers; and (vi) tumor vascular disrupting agents. We also review the efficacy of nanostructures as natural vascular targeting agents. The efficacy of each approach in cancer therapy is further discussed.

Posterior drug delivery via periocular route: challenges and opportunities

Drug delivery to the posterior segment via the periocular route is a promising route for delivery of a range of formulations. In this review, we have highlighted the challenges and opportunities of posterior segment drug delivery via the periocular route. Consequently, we have discussed different types of periocular routes, physiological barriers that limit effective drug delivery, practical challenges regarding patient compliance and acceptability and recent advances in developing innovative strategies to enhance periocular drug delivery. We conclude with a perspective on how we envisage the importance of understanding complex barrier functions so as to continue to develop innovative drug-delivery systems.

Interleukin-6 participation in pathology of ocular diseases

Interleukin-6 (IL-6) is a multifunctional cytokine that affects a variety of cells in the body such as osteoclasts, hepatocytes, endothelial cells, epithelial cells, white and red blood cells and etc. Elevated levels of IL-6 have been detected in many ocular diseases. Studies show that IL-6 has a major role in the pathology of glaucoma, CRVO, macular edema, ocular neovascularization, posterior capsule opacity formation, keratitis, dry eye disease, allergic eye disease, ocular autoimmune disease, corneal chemical burn, ocular inflammation and so on. IL-6 does its effects through the classic or trans-signal pathways in cells. Blocking of IL-6 signal pathways via Tocilizumab or other chemicals and therapeutics will help to overcome complications related to ocular diseases.

Facilitation of transscleral drug delivery by drug loaded magnetic polymeric particles

A unique method was used to facilitate ocular drug delivery from periocular route by drug loaded magnetic sensitive particles. Injection of particles in periocular space along the eye axis followed by application of magnetic field in front of the eye would trigger the magnetic polymeric particles to move along the direction of magnetic force and reside against the outer surface of the sclera. This technique prevents removal of drug in the periocular space, observed in conventional transscleral drug delivery systems and hence higher amount of drug can enter the eye in a longer period of time. The experiments were performed by fresh human sclera and an experimental setup. Experimental setup was designed by side by side diffusion cell and hydrodynamic and thermal simulation of the posterior segment of the eye were applied. Magnetic polymeric particles were synthesized by alginate as a model polymer, iron oxide nanoparticles as a magnetic agent and diclofenac sodium as a model drug and characterized by SEM, TEM, DLS and FT-IR techniques. According to the SEM images, the size range of particles is around 60 to 800nm. The results revealed that the cumulative drug transfer from magnetic sensitive particles across the sclera improves by 70% in the presence of magnetic field. The results of this research show promising method of drug delivery to use magnetic properties to facilitate drug delivery to the back of the eye.