Ocular Drug Delivery: A Special Focus on the Thermosensitive Approach

Nanosuspensions in ophthalmology: Overcoming challenges and enhancing drug delivery for eye diseases

This review article provides a comprehensive overview of the advancements in using nanosuspensions for controlled drug delivery in ophthalmology. It highlights the significance of ophthalmic drug delivery due to the prevalence of eye diseases and delves into various aspects of this field. The article explores molecular mechanisms, drugs used, and physiological factors affecting drug absorption. It also addresses challenges in treating both anterior and posterior eye segments and investigates the role of mucus in obstructing micro- and nanosuspensions. Nanosuspensions are presented as a promising approach to enhance drug solubility and absorption, covering formulation, stability, properties, and functionalization. The review discusses the pros and cons of using nanosuspensions for ocular drug delivery and covers their structure, preparation, characterization, and applications. Several graphical representations illustrate their role in treating various eye conditions. Specific drug categories like anti-inflammatory drugs, antihistamines, glucocorticoids, and more are discussed in detail, with relevant studies. The article also addresses current challenges and future directions, emphasizing the need for improved nanosuspension stability and exploring potential technologies. Nanosuspensions have shown substantial potential in advancing ophthalmic drug delivery by enhancing solubility and absorption. This article is a valuable resource for researchers, clinicians, and pharmaceutical professionals in this field, offering insights into recent developments, challenges, and future prospects in nanosuspension use for ocular drug delivery.

Genome editing in the treatment of ocular diseases

Genome-editing technologies have ushered in a new era in gene therapy, providing novel therapeutic strategies for a wide range of diseases, including both genetic and nongenetic ocular diseases. These technologies offer new hope for patients suffering from previously untreatable conditions. The unique anatomical and physiological features of the eye, including its immune-privileged status, size, and compartmentalized structure, provide an optimal environment for the application of these cutting-edge technologies. Moreover, the development of various delivery methods has facilitated the efficient and targeted administration of genome engineering tools designed to correct specific ocular tissues. Additionally, advancements in noninvasive ocular imaging techniques and electroretinography have enabled real-time monitoring of therapeutic efficacy and safety. Herein, we discuss the discovery and development of genome-editing technologies, their application to ocular diseases from the anterior segment to the posterior segment, current limitations encountered in translating these technologies into clinical practice, and ongoing research endeavors aimed at overcoming these challenges.

[Latest Findings on Stimuli-Responsive Hydrogel Wound Dressings Applied in Diabetic Chronic Wound Repair]

Diabetic chronic wounds entail enormous psychological and economic burdens on diabetic patients. Traditional types of wound dressings lack diversity in their functions and do not have sufficient adaptability to the wound environment, which makes it difficult to meet the complicated needs arising during the healing process when they are used. Stimuli-responsive hydrogels respond specifically to the special environment of the wound area, for example, temperature, pH, glucose, etc., and achieve on-demand release by loading active substances, which effectively promotes diabetic wound healing. Herein, based on the research progress in stimulus-responsive wound dressings in recent years and the relevant work of our research team, we summarized and discussed hydrogel wound dressings responsive to temperature, pH, glucose, reactive oxygen species, enzymes, and multiple stimuli. Based on the special physiological environment of diabetic wounds, hydrogels with single or multiple stimuli-responsive properties can be designed so that they can release drugs on demand and improve the microenvironment of the wound, thus meeting the specific needs of different stages of wound healing. Although stimuli-responsive hydrogels currently show excellent therapeutic potential, there is still room for further development-cells or cytokines loaded in wound dressings usually act only at specific healing stages and the timing needs to be precisely controlled in order to avoid counterproductive effects on wound healing. In addition, the construction of sensor-therapeutic integrated devices for real-time monitoring of wound biochemical indicators so that drugs are release on demand and with precision to promote wound healing is also one of the topics that deserve more attention from researchers.

Transscleral Delivery of Dexamethasone-Loaded Microparticles Using a Dissolving Microneedle Array

Microneedles (MNs) have attracted considerable interest as a means of ocular drug delivery, a challenging delivery route due to the limitations imposed by the various biological barriers associated with this organ. In this study, a novel ocular drug delivery system was developed by formulating a dissolvable MN array containing dexamethasone-loaded PLGA microparticles for scleral drug deposition. The microparticles serve as a drug reservoir for controlled transscleral delivery. The MNs displayed sufficient mechanical strength to penetrate the porcine sclera. Dexamethasone (Dex) scleral permeation was significantly higher than in topically instilled dosage forms. The MN system was able to distribute the drug through the ocular globe, with 19.2% of the administered Dex detected in the vitreous humour. Additionally, images of the sectioned sclera confirmed the diffusion of fluorescent-labelled microparticles within the scleral matrix. The system therefore represents a potential approach for minimally invasive Dex delivery to the posterior of the eye, which lends itself to self-administration and hence high patient convenience.

Different Applications of Temperature responsive nanogels as a new drug delivery system mini review

Temperature-sensitive drug delivery systems (TSDDS) are one of the systems that have received more attention in medical science these days due to their advantages. As these systems are sensitive to temperature, drug delivery to the target becomes more specific. Temperature-sensitive nanogels have many applications, including microbial infections, cancer therapy, transdermal use and tissue repair. These systems are characterized by minimal toxicity, improved therapeutic efficacy and reduced exposure to normal cells. This mini-review is prepared with different types of temperature-sensitive nanogel formation, release mechanisms, and their different applications. Various systems reported under these categories for targeted and controlled delivery of different classes of drugs, such as anti-cancer and antibiotic drugs with special emphasis on anti-cancer drugs and tissue healing, are discussed in this mini-review.

Pre-clinical safety of topically administered sunitinib-loaded lipid and polymeric nanocarriers targeting corneal neovascularization

Three different types of sunitinib-loaded (SUN-loaded) nanocarriers were compared, aiming at the topical treatment of corneal neovascularization (CNV): polymeric nanospheres (NS), liposomes (LIP), and solid lipid nanoparticles (SLN). Three out of eleven formulations prepared for an optimization study - the best SUN-loaded nanocarrier of each assessed type (NS, LIP, and SLN) - were selected, based on their size, polydispersity index (PdI), drug load (DL), and encapsulation efficiency (EE). These three optimal formulations were further characterized by nanoparticle tracking analysis (NTA), electron paramagnetic resonance (EPR) spectroscopy, and zeta potential. In vitro SUN release profiles were obtained for the optimal formulations, along with ex vivo corneal permeability/retention studies, and ocular tolerance assays, namely: the bovine corneal opacity and permeability (BCOP) assay, the HET-CAM test (hen's egg test - chorioallantoic membrane), and hemolytic potential (HP) assay. None of the optimal formulations exhibited toxicity or potential for ocular irritation. SLN showed higher surface fluidity, drug release more suitable for topical ocular applications, besides greater SUN corneal retention. Our results suggest that SLN are the best CNV-targeting SUN-loaded nanocarriers for clinical translation when compared to their NS and LIP analogues.

Comparison of postcataract surgery anti-inflammatory regimens on the incidence of cystoid macular edema, iritis, pain, and photophobia

PURPOSE

To compare postcataract surgery anti-inflammatory regimens of intracanalicular dexamethasone insert and topical bromfenac on the incidence of cystoid macular edema (CME), iritis, pain, and photophobia.

SETTING

Eyes of York Cataract & Laser Center, York, Pennsylvania.

DESIGN

Retrospective chart review.

METHODS

Case records of 647 consecutive patients (1001 eyes) who underwent cataract surgery and received dexamethasone intracanalicular insert 0.4 mg (Group 1; 482 eyes) or topical nonsteroidal anti-inflammatory drug (NSAID) (bromfenac 0.075% 2 times a day) for 4 weeks postoperatively (Group 2; 519 eyes) were included. Both groups received intracameral moxifloxacin and phenylephrine/ketorolac. Patients with prior CME, vitreomacular traction, combined cataract/glaucoma surgery, and medication protocols different from those examined in this study were excluded.

RESULTS

Compared with the dexamethasone insert group, the topical NSAID group had a significantly lower incidence of CME (0.4% [2/519] vs 3.9% [19/482], P < .001) and photophobia (1.9% [10/519] vs 4.8% [23/482], P = .012). The incidence of breakthrough iritis (3.5% [18/519] vs 5.6% [27/482], P = .104) and pain also trended lower (4.0% [21/519] vs 5.4% [26/482], P = .314) in the topical NSAID group.

CONCLUSIONS

Topical NSAIDs were found to be more effective in controlling CME, pain, iritis, and photophobia after cataract surgery compared with the intracanalicular dexamethasone insert in the presence of intracameral phenylephrine/ketorolac.

Recent advances in responsive hydrogels for diabetic wound healing

Poor wound healing after diabetes mellitus remains a challenging problem, and its pathophysiological mechanisms have not yet been fully elucidated. Persistent bleeding, disturbed regulation of inflammation, blocked cell proliferation, susceptible infection and impaired tissue remodeling are the main features of diabetic wound healing. Conventional wound dressings, including gauze, films and bandages, have a limited function. They generally act as physical barriers and absorbers of exudates, which fail to meet the requirements of the whol diabetic wound healing process. Wounds in diabetic patients typically heal slowly and are susceptible to infection due to hyperglycemia within the wound bed. Once bacterial cells develop into biofilms, diabetic wounds will exhibit robust drug resistance. Recently, the application of stimuli-responsive hydrogels, also known as "smart hydrogels", for diabetic wound healing has attracted particular attention. The basic feature of this system is its capacities to change mechanical properties, swelling ability, hydrophilicity, permeability of biologically active molecules, etc., in response to various stimuli, including temperature, potential of hydrogen (pH), protease and other biological factors. Smart hydrogels can improve therapeutic efficacy and limit total toxicity according to the characteristics of diabetic wounds. In this review, we summarized the mechanism and application of stimuli-responsive hydrogels for diabetic wound healing. It is hoped that this work will provide some inspiration and suggestions for research in this field.

Developments on the Smart Hydrogel-Based Drug Delivery System for Oral Tumor Therapy

At present, an oral tumor is usually treated by surgery combined with preoperative or postoperative radiotherapies and chemotherapies. However, traditional chemotherapies frequently result in substantial toxic side effects, including bone marrow suppression, malfunction of the liver and kidneys, and neurotoxicity. As a new local drug delivery system, the smart drug delivery system based on hydrogel can control drug release in time and space, and effectively alleviate or avoid these problems. Environmentally responsive hydrogels for smart drug delivery could be triggered by temperature, photoelectricity, enzyme, and pH. An overview of the most recent research on smart hydrogels and their controlled-release drug delivery systems for the treatment of oral cancer is given in this review. It is anticipated that the local drug release method and environment-responsive benefits of smart hydrogels will offer a novel technique for the low-toxicity and highly effective treatment of oral malignancy.

An injectable hyperthermic nanofiber mesh with switchable drug release to stimulate chemotherapy potency

We developed a smart nanofiber mesh (SNM) with anticancer abilities as well as injectability and fast recovery from irregular to non-compressible shapes. The mesh can be injected at the tumor site to modulate and control anticancer effects by loading the chemotherapeutic drug, paclitaxel (PTX), as well as magnetic nanoparticles (MNPs). The storage modulus of the mesh decreases when applied with a certain shear strain, and the mesh can pass through a 14-gauge needle. Moreover, the fibrous morphology is maintained even after injection. In heat-generation measurements, the mesh achieved an effective temperature of mild hyperthermia (41-43°C) within 5 min of exposure to alternating magnetic field (AMF) irradiation. An electrospinning method was employed to fabricate the mesh using a copolymer of N-isopropylacrylamide (NIPAAm) and N-hydroxyethyl acrylamide (HMAAm), whose phase transition temperature was adjusted to a mildly hyperthermic temperature range. Pplyvinyl alcohol (PVA) was also incorporated to add shear-thinning property to the interactions between polymer chains derived from hydrogen bonding, The "on-off" switchable release of PTX from the mesh was detected by the drug release test. Approximately 73% of loaded PTX was released from the mesh after eight cycles, whereas only a tiny amount of PTX was released during the cooling phase. Furthermore, hyperthermia combined with chemotherapy after exposure to an AMF showed significantly reduced cancer cell survival compared to the control group. Subsequent investigations have proven that a new injectable local hyperthermia chemotherapy platform could be developed for cancer treatment using this SNM.

Protein and polypeptide mediated delivery to the eye

Hybrid or recombinant protein-polymers, peptide-based biomaterials, and antibody-targeted therapeutics are widely explored for various ocular conditions and vision correction. They have been noted for their potential biocompatibility, potency, adaptability, and opportunities for sustained drug delivery. Unique to peptide and protein therapeutics, their production by cellular translation allows their precise modification through genetic engineering. To a greater extent than drug delivery to other systems, delivery to the eye can benefit from the combination of locally-targeted administration and protein-based specificity. Consequently, a range of delivery platforms and administration methods have been exploited to address the ocular delivery of peptide and protein biomaterials. This review discusses a sample of preclinical and clinical opportunities for peptide-based drug delivery to the eye.

Bioengineered Human Stromal Lenticule for Recombinant Human Nerve Growth Factor Release: A Potential Biocompatible Ocular Drug Delivery System

Small incision lenticule extraction (SMILE), is a surgical procedure for the myopia correction, during which a corneal stromal lenticule is extracted. Given that we have previously demonstrated how this discarded tissue could be repurposed as a bio-scaffold for stromal engineering, this study aimed to explore its use as an ocular drug delivery system of active molecules, using neurotrophic factor Nerve Growth Factor (NGF). We employed human stromal lenticules directly collected from healthy donors undergoing SMILE. Following a sodium dodecylsulfate (SDS) treatment, decellularized lenticules were incubated with a suspension of polylactic-co-glycolic-acid (PLGA) microparticles (MPs) loaded with recombinant human NGF (rhNGF-MPs). Fluorescent MPs (Fluo-MPs) were used as control. Data demonstrated the feasibility to engineer decellularized lenticules with PLGA-MPs which remain incorporated both on the lenticules surface and in its stromal. Following their production, the in vitro release kinetic showed a sustained release for up to 1 month of rhNGF from MPs loaded to the lenticule. Interestingly, rhNGF was rapidly released in the first 24 h, but it was sustained up to the end of the experiment (1 month), with preservation of rhNGF activity (around 80%). Our results indicated that decellularized human stromal lenticules could represent a biocompatible, non-immunogenic natural scaffold potential useful for ocular drug delivery. Therefore, combining the advantages of tissue engineering and pharmaceutical approaches, this in vitro proof-of-concept study suggests the feasibility to use this scaffold to allow target release of rhNGF in vivo or other pharmaceutically active molecules that have potential to treat ocular diseases.

[An injectable hydrogel/staple fiber composite for sustained release of CA4P and doxorubicin for combined chemotherapy of xenografted breast tumor in mice]

OBJECTIVE

To prepare an injectable hydrogel/staple fiber composite loaded with combretastain A-4 disodium phosphate (CA4P) and doxorubicin (DOX) and evaluate its antitumor efficacy via intratumoral injection.

METHODS

DOX-loaded PELA staple fibers (FDOX) were prepared using electro-spinning and cryo-cutting, and the drug distribution on the surface of the fibers was observed using a fluorescence microscope, and the encapsulation efficiency and loading capacity of FDOX were determined with a fluorospectro photometer. The fibers were then dispersed in CA4P-loaded PLGA-PEG-PLGA tri-block polymer solution at room temperature to obtain the hydrogel/staple fiber composite (GCA4P/FDOX). The thermo-sensitivity of this composite was determined by a test tube inverting method. An ultraviolet spectrophotometer and a fluorospectrophotometer were used to detect the release profile of CA4P and DOX, respectively. We observed in vivo gel formation of the composite after subcutaneous injection in mice. The in vitro cytotoxicity of GCA4P/FDOX composite in MCF-7 and 4T1 cells was assessed using cell Counting Kit-8 (CCK-8) reagent. In a mouse model bearing breast tumor 4T1 cell xenograft, we evaluated the antitumor efficacy of the composite by monitoring tumor growth within 30 days after intratumoral injection of the composite. HE staining, immunohistochemistry for Ki67 and immunofluorescence (TUNEL) assay were used for pathological examination of the tumor tissues 21 days after the treatments.

RESULTS

The average length of FDOX was 4.0±1.3 μm, and its drug loading capacity was (2.69±0.35)% with an encapsulation efficiency of (89.70±0.12)%. DOX was well distributed on the surface of the fibers. When the temperature increased to 37 ℃, the composite rapidly solidified to form a gel in vitro. Drug release behavior test showed that CA4P was completely released from the composite in 5 days and 87% of DOX was released in 30 days. After subcutaneous injection, the composite solidified rapidly without degradation at 24 h after injection. After incubation with GCA4P/FDOX for 72 h, only 30.6% of MCF-7 cells and 28.9% of 4T1 cells were viable. In the tumor-bearing mice, the tumor volume was 771.9±76.9 mm3 in GCA4P/FDOX treatment group at 30 days. Pathological examination revealed obvious necrosis of the tumor tissues and tumor cell apoptosis induced by intratumoral injection of G4A4P/FDOX.

CONCLUSION

As an efficient dual drug delivery system, this hydrogel/staple fiber composite provides a new strategy for local combined chemotherapy of solid tumors.

Advances in Injectable In Situ-Forming Hydrogels for Intratumoral Treatment

Chemotherapy has been linked to a variety of severe side effects, and the bioavailability of current chemotherapeutic agents is generally low, which decreases their effectiveness. Therefore, there is an ongoing effort to develop drug delivery systems to increase the bioavailability of these agents and minimize their side effects. Among these, intratumoral injections using in situ-forming hydrogels can improve drugs' bioavailability and minimize drugs' accumulation in non-target organs or tissues. This review describes different types of injectable in situ-forming hydrogels and their intratumoral injection for cancer treatment, after which we discuss the antitumor effects of intratumoral injection of drug-loaded hydrogels. This review concludes with perspectives on the future applicability of, and challenges for, the adoption of this drug delivery technology.

Development and Evaluation of Polyvinylpyrrolidone K90 and Poloxamer 407 Self-Assembled Nanomicelles: Enhanced Topical Ocular Delivery of Artemisinin

Age-related macular degeneration is a multifactorial disease affecting the posterior segment of the eye and is characterized by aberrant nascent blood vessels that leak blood and fluid. It ends with vision loss. In the present study, artemisinin which is poorly water-soluble and has potent anti-angiogenic and anti-inflammatory properties was formulated into nanomicelles and characterized for its ocular application and anti-angiogenic activity using a CAM assay. Artemisinin-loaded nanomicelles were prepared by varying the concentrations of PVP k90 and poloxamer 407 at different ratios and showed spherical shape particles in the size range of 41-51 nm. The transparency and cloud point of the developed artemisinin-loaded nanomicelles was found to be 99-94% and 68-70 °C, respectively. The in vitro release of artemisinin from the nanomicelles was found to be 96.0-99.0% within 8 h. The trans-corneal permeation studies exhibited a 1.717-2.169 µg permeation of the artemisinin from nanomicelles through the excised rabbit eye cornea for 2 h. Drug-free nanomicelles did not exhibit noticeable DNA damage and showed an acceptable level of hemolytic potential. Artemisinin-loaded nanomicelles exhibited remarkable anti-angiogenic activity compared to artemisinin suspension. Hence, the formulated artemisinin-loaded nanomicelles might have the potential for the treatment of AMD.

A New Bevacizumab Carrier for Intravitreal Administration: Focus on Stability

Bevacizumab (BVZ) is a monoclonal antibody that binds to human vascular endothelial growth factor A (VEGF-A) and inhibits the interaction between VEGF-A and VEGF receptors, thus blocking the angiogenesis. Repeated intravitreal injections of BVZ for the treatment of ocular pathologies that present an excessive proliferation results in a low patience compliance. BVZ is specially indicated for the treatment of diabetic and degenerative retinopathy. In the present study, we designed lipid nanoparticles (NPs) as a BVZ sustained drug delivery system for reducing the frequency of administration. We used a simple and highly efficient procedure, “Cold dilution of microemulsions”, to obtain spherical NPs with mean diameters of 280–430 nm, Zeta potentials between −17 and −31 mV, and drug entrapment efficiencies between 50 to 90%. This study focused on the biochemical and biophysical stabilities of BVZ after entrapment in NPs. SDS-PAGE electrophoretic analysis and circular dichroism, dynamic light scattering, and scanning electron microscopy were used to characterize BVZ-loaded NPs. The biocompatibility was assessed by in vitro cell compatibility studies using the ARPE-19 cell line. Thus, in this work, a stable BVZ-loaded system was obtained. In addition, several studies have shown that BVZ is released slowly from the lipid matrix and that this system is biocompatible. The results are promising and the developed NPs could be exploited to create a new, potentially effective and minimally invasive treatment of intraocular diseases.

Cyclosporine Lipid Nanocapsules as Thermoresponsive Gel for Dry Eye Management: Promising Corneal Mucoadhesion, Biodistribution and Preclinical Efficacy in Rabbits

An ophthalmic cyclosporine (CsA) formulation based on Lipid nanocapsules (LNC) was developed for dry eye management, aiming to provide targeting to ocular tissues with long-term drug levels and maximum tolerability. CsA-LNC were of small particle size (41.9 ± 4.0 nm), narrow size distribution (PdI ≤ 0.1), and high entrapment efficiency (above 98%). Chitosan (C) was added to impart positive charge. CsA-LNC were prepared as in-situ gels using poloxamer 407 (P). Ex vivo mucoadhesive strength was evaluated using bovine cornea, while in vivo corneal biodistribution (using fluorescent DiI), efficacy in dry eye using Schirmer tear test (STT), and ocular irritation using Draize test were studied in rabbits compared to marketed ophthalmic CsA nanoemulsion (CsA-NE) and CsA in castor oil. LNC incorporation in in-situ gels resulted in an increase in mucoadhesion, and stronger fluorescence in corneal layers seen by confocal microscopy, compared to the other tested formulations. Rate of recovery (days required to restore corneal baseline hydration level) assessed over 10 days, showed that CsA-LNC formulations produced complete recovery by day 7 comparable to CsA-NE. No Ocular irritation was observed by visual and histopathological examination. Based on data generated, CsA-LNC-CP in-situ gel proved to be a promising effective nonirritant CsA ophthalmic formulation for dry eye management.

Betaxolol-loaded niosomes integrated within pH-sensitive in situ forming gel for management of glaucoma

Blindness and impaired vision are considered as the most troublesome health conditions leading to significant socioeconomic strains. The current study focuses on development of nanoparticulate systems (i.e., niosomes) as drug vehicles to enhance the ocular availability of betaxolol hydrochloride for management of glaucoma. Betaxolol-loaded niosomes were further laden into pH-responsive in situ forming gels to further extend precorneal retention of the drug. The niosomes were evaluated in terms of vesicle size, morphology, size distribution, surface charge and encapsulation efficiency. The optimized niosomes, comprised of Span® 40 and cholesterol at a molar ratio of 4:1, displayed particle size of 332 ± 7 nm, zeta potential of -46 ± 1 mV, and encapsulation efficiency of 69 ± 5%. The optimal nanodispersion was then incorporated into a pH-triggered in situ forming gel comprised of Carbopol® 934P and hydroxyethyl cellulose. The formed gels were translucent, pseudoplastic, mucoadhesive, and displayed a sustained in vitro drug release pattern. Upon instillation of the betaxolol-loaded niosomal gel into rabbits' eyes, a prolonged intraocular pressure reduction and significant enhancement in the relative bioavailability of betaxolol (280 and 254.7%) in normal and glaucomatous rabbits, were attained compared to the marketed eye drops, respectively. Hence, the developed pH-triggered nanoparticulate gelling system might provide a promising carrier for ophthalmic drug delivery and for improved augmentation of glaucoma.

Recent Advances in Injectable Hydrogels for Controlled and Local Drug Delivery

Injectable hydrogels have received considerable interest in the biomedical field due to their potential applications in minimally invasive local drug delivery, more precise implantation, and site-specific drug delivery into poorly reachable tissue sites and into interface tissues, where wound healing takes a long time. Injectable hydrogels, such as in situ forming and/or shear-thinning hydrogels, can be generated using chemically and/or physically crosslinked hydrogels. Yet, for controlled and local drug delivery applications, the ideal injectable hydrogel should be able to provide controlled and sustained release of drug molecules to the target site when needed and should limit nonspecific drug molecule distribution in healthy tissues. Thus, such hydrogels should sense the environmental changes that arise in disease states and be able to release the optimal amount of drug over the necessary time period to the target region. To address this, researchers have designed stimuli-responsive injectable hydrogels. Stimuli-responsive hydrogels change their shape or volume when they sense environmental stimuli, e.g., pH, temperature, light, electrical signals, or enzymatic changes, and deliver an optimal concentration of drugs to the target site without affecting healthy tissues.

Williams G, Brocchini S, Awwad S. Injectables and Depots to Prolong Drug Action of Proteins and Peptides

Proteins and peptides have emerged in recent years to treat a wide range of multifaceted diseases such as cancer, diabetes and inflammation. The emergence of polypeptides has yielded advancements in the fields of biopharmaceutical production and formulation. Polypeptides often display poor pharmacokinetics, limited permeability across biological barriers, suboptimal biodistribution, and some proclivity for immunogenicity. Frequent administration of polypeptides is generally required to maintain adequate therapeutic levels, which can limit efficacy and compliance while increasing adverse reactions. Many strategies to increase the duration of action of therapeutic polypeptides have been described with many clinical products having been developed. This review describes approaches to optimise polypeptide delivery organised by the commonly used routes of administration. Future innovations in formulation may hold the key to the continued successful development of proteins and peptides with optimal clinical properties.

Dendrimer- and polymeric nanoparticle-aptamer bioconjugates as nonviral delivery systems: a new approach in medicine

Aptamers are RNA or DNA oligonucleotides interacting to form unique 3D target conformations with high affinity and specificity, and are emerging as a powerful class of ligands for therapeutic applications. In addition, dendrimers are well-defined nano-sized symmetric polymeric molecules. In this review, we provide an analysis of the use of dendrimers modified with aptamers as nonviral vectors to specifically target tumor cells. Various anticancer agents have been encapsulated with dendrimers complexing with aptamers, including epirubicin, camptothecin, Bcl-xL short hairpin (sh)RNA, and 5-fluorouracil rhodamine-labeled dextran. Other types of polymeric nanoparticle (NP)-aptamer bioconjugates have also been developed and loaded with Pt(IV) derivatives, to target specific tumor cells.

Hydrogel Biomaterials for Application in Ocular Drug Delivery

There are many challenges involved in ocular drug delivery. These are a result of the many tissue barriers and defense mechanisms that are present with the eye; such as the cornea, conjunctiva, the blinking reflex, and nasolacrimal drainage system. This leads to many of the conventional ophthalmic preparations, such as eye drops, having low bioavailability profiles, rapid removal from the administration site, and thus ineffective delivery of drugs. Hydrogels have been investigated as a delivery system which is able to overcome some of these challenges. These have been formulated as standalone systems or with the incorporation of other technologies such as nanoparticles. Hydrogels are able to be formulated in such a way that they are able to change from a liquid to gel as a response to a stimulus; known as "smart" or stimuli-responsive biotechnology platforms. Various different stimuli-responsive hydrogel systems are discussed in this article. Hydrogel drug delivery systems are able to be formulated from both synthetic and natural polymers, known as biopolymers. This review focuses on the formulations which incorporate biopolymers. These polymers have a number of benefits such as the fact that they are biodegradable, biocompatible, and non-cytotoxic. The biocompatibility of the polymers is essential for ocular drug delivery systems because the eye is an extremely sensitive organ which is known as an immune privileged site.

Noble Metals and Soft Bio-Inspired Nanoparticles in Retinal Diseases Treatment: A Perspective

We are witnessing an exponential increase in the use of different nanomaterials in a plethora of biomedical fields. We are all aware of how nanoparticles (NPs) have influenced and revolutionized the way we supply drugs or how to use them as therapeutic agents thanks to their tunable physico-chemical properties. However, there is still a niche of applications where NP have not yet been widely explored. This is the field of ocular delivery and NP-based therapy, which characterizes the topic of the current review. In particular, many efforts are being made to develop nanosystems capable of reaching deeper sections of the eye such as the retina. Particular attention will be given here to noble metal (gold and silver), and to polymeric nanoparticles, systems consisting of lipid bilayers such as liposomes or vesicles based on nonionic surfactant. We will report here the most relevant literature on the use of different types of NPs for an efficient delivery of drugs and bio-macromolecules to the eyes or as active therapeutic tools.

Comparative Assessment of Distribution Characteristics and Ocular Pharmacokinetics of Norvancomycin Between Continuous Topical Ocular Instillation and Hourly Administration of Eye Drop

Background

The aim of this study was to compare the distribution characteristics and ocular pharmacokinetics of norvancomycin (NVCM) in ocular tissues of the anterior segment between continuous topical ocular instillation and hourly administration of eye drop in rabbits.

Methods

Sixty rabbits were randomly divided into two groups: continuous topical ocular instillation drug delivery (CTOIDD) group and eye drop (control) group. In the CTOIDD group, NVCM solution (50 mg/mL) was perfused to the ocular surface using the CTOIDD system at 2 mL/h up to 10 h and the same solution was administered at one drop (50 μL) per hour for 10 h in the control group. Animals (N=6 per time-point per group) were humanely killed at 2, 4, 6, 10, and 24 h to analyze their ocular tissues and plasma. The concentrations of NVCM in the conjunctiva, cornea, aqueous humour, iris, ciliary body and plasma were measured by HPLC with photodiode array detector. The pharmacokinetic parameters were calculated by Kinetica 5.1.

Results

The highest concentrations of NVCM for the CTOIDD group and control group were 2105.45±919.89 μg/g and 97.18±43.14 μg/g in cornea, 3033.92±1061.95 μg/g and 806.99±563.02 μg/g in conjunctiva, 1570.19±402.87 μg/g and 46.93±23.46 μg/g in iris, 181.94±47.11 μg/g and 15.38±4.00 μg/g in ciliary body, 29.78±4.90 μg/mL and 3.20±1.48 μg/mL in aqueous humour, and 26.89±5.57 μg/mL and 1.90±1.87 μg/mL in plasma, respectively. The mean NVCM levels significantly increased at all time-points in cornea, iris, and ciliary body (p<0.05) in the CTOIDD group. The AUC_0–24 values in the CTOIDD group were 27,543.70 μg·h/g in cornea, 32,514.48 μg·h/g in conjunctiva, 8631.05 μg·h/g in iris, 2194.36 μg·h/g in ciliary body and 343.9 μg·h/mL in aqueous humour, which were higher than for the eye drop group in all tissues.

Conclusion

Since continuous instillation of NVCM with CTOIDD could reach significantly higher concentrations and was sustained for a longer period compared with hourly administration of eye drop, CTOIDD administered NVCM could be a possible method to treat bacterial keratitis.

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Injectable Hydrogels for Localized Cancer Therapy

Traditional intravenous chemotherapy is relative to many systemic side effects, including myelosuppression, liver or kidney dysfunction, and neurotoxicity. As an alternative method, the injectable hydrogel can efficiently avoid these problems by releasing drugs topically at the tumor site. With advantages of localized drug toxicity in the tumor site, proper injectable hydrogel as the drug delivery system has become a research hotspot. Based on different types and stages of cancer, a variety of hydrogel drug delivery systems were developed, including thermosensitive, pH-sensitive, photosensitive, and dual-sensitive hydrogel. In this review, the latest developments of these hydrogels and related drug delivery systems were summarized. In summary, our increasing knowledge of injectable hydrogel for localized cancer therapy ensures us that it is a more durable and effective approach than traditional chemotherapy. Smart release system reacting to different stimuli at different time according to the micro-environment changes in the tumor site is a promising tendency for further studies.