Mucoadhesive nano-sized supramolecular assemblies for improved pre-corneal drug residence time

Polymers and their engineered analogues for ocular drug delivery: Enhancing therapeutic precision

Ocular drug delivery is constrained by anatomical and physiological barriers, necessitating innovative solutions for effective therapy. Natural polymers like hyaluronic acid, chitosan, and gelatin, alongside synthetic counterparts such as PLGA and PEG, have gained prominence for their biocompatibility and controlled release profiles. Recent strides in polymer conjugation strategies have enabled targeted delivery through ligand integration, facilitating tissue specificity and cellular uptake. This versatility accommodates combined drug delivery, addressing diverse anterior (e.g., glaucoma, dry eye) and posterior segment (e.g., macular degeneration, diabetic retinopathy) afflictions. The review encompasses an in-depth exploration of each natural and synthetic polymer, detailing their individual advantages and disadvantages for ocular drug delivery. By transcending ocular barriers and refining therapeutic precision, these innovations promise to reshape the management of anterior and posterior segment eye diseases.

Topical Application of Linezolid-Loaded Chitosan Nanoparticles for the Treatment of Eye Infections

Linezolid (LZ) loaded chitosan-nanoparticles (CSNPs) was developed by the ionic-gelation method using Tripolyphosphate-sodium as a crosslinker for topical application for the treatment of bacterial eye infections. Particles were characterized by Zeta-Sizer (Malvern Nano-series). TEM was used for structural morphology. Encapsulation and drug loading were estimated by measuring the unencapsulated drug. In-vitro drug release in STF (pH 7) was performed through a dialysis membrane. Storage stability of LZ-CSNPs was checked at 25 °C and 40 °C for six months. The antimicrobial potency of NPs was evaluated on different Gram-positive strains. Ocular irritation and pharmacokinetic studies were completed in rabbits. Ex-vivo transcorneal permeation of the drug was determined through the rabbit cornea. Ionic interaction among the oppositely charged functional groups of CS and TPP generated the CSNPs. The weight ratio at 3:1, wt/wt (CS/TPP) with 21.7 mg of LZ produced optimal NPs (213.7 nm with 0.387 of PDI and +23.1 mV of ZP) with 71% and 11.2% encapsulation and drug loading, respectively. Around 76.7% of LZ was released from LZ-AqS within 1 h, while 79.8% of LZ was released from CSNPs at 12 h and 90% at 24 h. The sustained drug release property of CSNPS was evaluated by applying kinetic models. The linearity in the release profile suggested that the release of LZ from CSNPs followed the Higuchi-Matrix model. LZ-CSNPs have shown 1.4 to 1.6-times improved antibacterial activity against the used bacterial strains. The LZ-CSNPs were "minimally-irritating" to rabbit eyes and exhibited 4.4-times increased transcorneal permeation of LZ than from LZ-AqS. Around 3-, 1.2- and 3.1-times improved T_max, C_max, and AUC_{0-24 h}, respectively were found for LZ-CSNPs during the ocular pharmacokinetic study. AqS has shown 3.1-times faster clearance of LZ. Conclusively, LZ-CSNPs could offer a better alternative for the prolonged delivery of LZ for the treatment of bacterial infections in the eyes.

Bergamot Essential Oil: A Method for Introducing It in Solid Dosage Forms

Bergamot essential oil (BEO) possess antimicrobial, antiproliferative, anti-inflammatory, analgesic, neuroprotective, and cardiovascular effects. However, it is rich in volatile compounds, e.g., limonene, that are susceptible to conversion and degradation reactions. The aim of this communication was to prepare a conjugate based on a quaternary ammonium chitosan derivative (QA-Ch) and methyl-βCD (MCD), coded as BEO/QA-Ch-MCD, to encapsulate BEO in order to stabilize its volatile compounds, eliminate its unpleasant taste, and convert the oil in a solid dosage form. The obtained conjugate, BEO/QA-Ch-MCD, was highly soluble and had a percentage of extract association efficiency (AE %), in terms of polyphenols and limonene contents, of 22.0 ± 0.9 and 21.9 ± 1.2, respectively. Moreover, stability studies under UV stress in simulated gastric fluid showed that BEO/QA-Ch-MCD was more able to protect polyphenols and limonene from degradation compared to free BEO or BEO complexed with MCD (BEO/MCD). The complexation and subsequent lyophilization allowed the transformation of a liquid into a solid dosage form capable of eliminating the unpleasant taste of the orally administered oil and rendering the solid suitable to produce powders, granules, tablets, etc. These solid oral dosage forms, as they come into contact with physiological fluids, could generate nanosized agglomerates able to increase the stability of their active contents and, consequently, their bioavailability.

Sertaconazole-Nitrate-Loaded Leciplex for Treating Keratomycosis: Optimization Using D-Optimal Design and In Vitro, Ex Vivo, and In Vivo Studies

This study aims to develop efficient topical therapy for keratomycosis using sertaconazolenitrate (STZN)-loaded leciplex (LP). The D-optimal design was used to optimize STZN-loaded LP by utilizing soy phosphatidylcholine (SPC) molar ratio (X₁), cationic surfactant molar ratio (X₂), and cationic surfactant type (X₃) as the independent variables, whereas their impact was studied for entrapment efficiency percent (EE; Y₁), particle size (PS; Y₂), polydispersity index (PDI; Y₃), zeta potential (ZP; Y₄), and permeability coefficient (Kp; Y₅). The optimized formula was evaluated regarding morphology, ex vivo permeation, mucoadhesion, stability, and in vivo studies. The optimized formula was spherical and showed EE of 84.87 ± 1.71%, PS of 39.70 ± 1.35 nm, PDI of 0.242 ± 0.006, ZP of +54.60 ± 0.24 mV, and Kp of 0.0577 ± 0.0001 cm/h. The ex vivo permeation study revealed that the optimized formula enhanced the Kp and corneal deposition by 2.78 and 12.49 folds, respectively, compared to the aqueous drug dispersion. Furthermore, the optimized formula was stable and revealed promising mucoadhesion properties. Finally, the in vivo studies showed that the optimized formula was superior to the drug dispersion in treating rats with induced keratomycosis. These results confirmed the capabilities of LP as a promising nanocarrier for treating ocular diseases topically.

Untangling Mucosal Drug Delivery: Engineering, Designing, and Testing Nanoparticles to Overcome the Mucus Barrier

Mucus is a complex viscoelastic gel and acts as a barrier covering much of the soft tissue in the human body. High vascularization and accessibility have motivated drug delivery to various mucosal surfaces; however, these benefits are hindered by the mucus layer. To overcome the mucus barrier, many nanomedicines have been developed, with the goal of improving the efficacy and bioavailability of drug payloads. Two major nanoparticle-based strategies have emerged to facilitate mucosal drug delivery, namely, mucoadhesion and mucopenetration. Generally, mucoadhesive nanoparticles promote interactions with mucus for immobilization and sustained drug release, whereas mucopenetrating nanoparticles diffuse through the mucus and enhance drug uptake. The choice of strategy depends on many factors pertaining to the structural and compositional characteristics of the target mucus and mucosa. While there have been promising results in preclinical studies, mucus-nanoparticle interactions remain poorly understood, thus limiting effective clinical translation. This article reviews nanomedicines designed with mucoadhesive or mucopenetrating properties for mucosal delivery, explores the influence of site-dependent physiological variation among mucosal surfaces on efficacy, transport, and bioavailability, and discusses the techniques and models used to investigate mucus-nanoparticle interactions. The effects of non-homeostatic perturbations on protein corona formation, mucus composition, and nanoparticle performance are discussed in the context of mucosal delivery. The complexity of the mucosal barrier necessitates consideration of the interplay between nanoparticle design, tissue-specific differences in mucus structure and composition, and homeostatic or disease-related changes to the mucus barrier to develop effective nanomedicines for mucosal delivery.

Development and Evaluation of Chitosan Nanoparticles for Ocular Delivery of Tedizolid Phosphate

This study investigates the development of topically applied non-invasive chitosan-nanoparticles (CSNPs) for ocular delivery of tedizolid phosphate (TZP) for the treatment of MRSA-related ocular and orbital infections. An ionic-gelation method was used to prepare TZP-encapsulated CSNPs using tripolyphosphate-sodium (TPP) as cross-linker. Particle characterization was performed by the DLS technique (Zeta-Sizer), structural morphology was observed by SEM. The drug encapsulation and loading were determined by the indirect method. In-vitro release was conducted through dialysis bags in simulated tear fluid (pH 7) with 0.25% Tween-80. Physicochemical characterizations were performed for ocular suitability of CSNPS. An antimicrobial assay was conducted on different strains of Gram-positive bacteria. Eye-irritation from CSNPs was checked in rabbits. Transcorneal flux and apparent permeability of TZP from CSNPs was estimated through excised rabbit cornea. Ionic interaction between the anionic and cationic functional groups of TPP and CS, respectively, resulted in the formation of CSNPs at varying weight ratios of CS/TPP with magnetic stirring (700 rpm) for 4 h. The CS/TPP weight ratio of 3.11:1 with 10 mg of TZP resulted in optimal-sized CSNPs (129.13 nm) with high encapsulation (82%) and better drug loading (7%). Release profiles indicated 82% of the drug was released from the TZP aqueous suspension (TZP-AqS) within 1 h, while it took 12 h from F2 to release 78% of the drug. Sustained release of TZP from F2 was confirmed by applying different release kinetics models. Linearity in the profile (suggested by Higuchi’s model) indicated the sustained release property CSNPs. F2 has shown significantly increased (p < 0.05) antibacterial activity against some Gram-positive strains including one MRSA strain (SA-6538). F2 exhibited a 2.4-fold increased transcorneal flux and apparent permeation of TZP as compared to TZP-AqS, indicating the better corneal retention. No sign or symptoms of discomfort in the rabbits’ eyes were noted during the irritation test with F2 and blank CSNPs, indicating the non-irritant property of the TZP-CSNPs. Thus, the TZP-loaded CSNPs have strong potential for topical use in the treatment of ocular MRSA infections and related inflammatory conditions.

Enhanced topical corticosteroids delivery to the eye: A trade-off in strategy choice

Topical corticosteroids are the primary treatment of ocular inflammation caused by surgery, injury, or other conditions. Drug pre-corneal residence time, drug water solubility, and drug corneal permeability coefficient are the major factors that determine the ocular drug bioavailability after topical administration. Although growing research successfully enhanced local delivery of corticosteroids utilizing various strategies, rational and dynamic approaches to strategy selection are still lacking. Within this review, an overview of the various strategies as well as their performance in retention, solubility, and permeability coefficient of corticosteroids are provided. On this basis, the tradeoff of strategy selection is discussed, which may shed light on the rational choice and application of ophthalmic delivery enhancement strategies.

Colloidal nanosystems with mucoadhesive properties designed for ocular topical delivery

Over the last years, the scientific interest about topical ocular delivery targeting the posterior segment of the eye has been increasing. This is probably due to the fact that this is a non-invasive administration route, well tolerated by patients and with fewer local and systemic side effects. However, it is a challenging task due to the external ocular barriers, tear film clearance, blood flow in the conjunctiva and choriocapillaris and due to the blood-retinal barriers, amongst other features. An enhanced intraocular bioavailability of drugs can be achieved by either improving corneal permeability or by improving precorneal retention time. Regarding this last option, increasing residence time in the precorneal area can be achieved using mucoadhesive polymers such as xyloglucan, poly(acrylate), hyaluronic acid, chitosan, and carbomers. On the other hand, colloidal particles can interact with the ocular mucosa and enhance corneal and conjunctival permeability. These nanosystems are able to deliver a wide range of drugs, including macromolecules, providing stability and improving ocular bioavailability. New pharmaceutical approaches based on nanotechnology associated to bioadhesive compounds have emerged as strategies for a more efficient treatment of ocular diseases. Bearing this in mind, this review provides an overview of the current mucoadhesive colloidal nanosystems developed for ocular topical administration, focusing on their advantages and limitations.

Challenges and strategies for the delivery of biologics to the cornea

Biologics, like peptides, proteins and nucleic acids, have proven to be promising drugs for the treatment of numerous diseases. However, besides the off label use of the monoclonal antibody bevacizumab for the treatment of corneal neovascularization, to date no other biologics for corneal diseases have reached the market. Indeed, delivering biologics in the eye remains a challenge, especially at the level of the cornea. While it appears to be a rather accessible tissue for the administration of drugs, the cornea in fact presents several anatomical barriers to delivery. In addition, also intracellular delivery barriers need to be overcome to achieve a promising therapeutic outcome with biologics. This review outlines efforts that have been reported to successfully deliver biologics into the cornea. Biochemical and physical methods for achieving delivery of biologics in the cornea are discussed, with a critical view on their efficacy in overcoming corneal barriers.

Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases the lowest bioavailability. Indeed, when a topical formulation reaches the precorneal area, i.e., the drug absorption and/or action site, it is rapidly eliminated due to eye protection mechanisms such as blinking, basal and reflex tearing, and naso-lacrimal draining. To avoid this and to reduce the frequency of dosing, various strategies have been developed to prolong drug residence time after topical administration. These strategies include the use of viscosity increasing and mucoadhesive excipients as well as combinations thereof. From the drug delivery system point of view, liquid and semisolid formulations are preferred over solid formulations such as ocular inserts and contact lenses. Furthermore, liquid and semisolid formulations can contain nano- and microcarrier systems that contribute to a prolonged residence time. Within this review an overview about the different types of excipients and formulations as well as their performance in valid animal models and clinical trials is provided.

Optimization to development of chitosan decorated polycaprolactone nanoparticles for improved ocular delivery of dorzolamide: In vitro, ex vivo and toxicity assessments

The present research work was designed to develop dorzolamide-loaded chitosan-coated polycaprolactone nanoparticles (DRZ-CS-PCL-NPs) for improved ocular delivery. The nanoparticles were prepared by single-step emulsification technique and optimized using the three-factor three-level Box-Behnken design. The optimized DRZ-CS-PCL-NPs prepared with the composition of polycaprolactone (60 mg), chitosan (0.6%) and polyvinyl alcohol (1.5%). The particle size, polydispersity index, zeta potential and encapsulation efficiency of optimized DRZ-CS-PCL-NPs were found to be 192.38 ± 6.42 nm, 0.18 ± 0.04, +5.21 ± 1.24 mV, and 72.48 ± 5.62%, respectively. The dependent and independent response variables showed excellent correlation and signifying the rationality of the optimized DRZ-CS-PCL-NPs. The DRZ release from CS-PCL-NPs showed biphasic behaviour with initial burst release for 2 h after that sustained-release up to 12 h of study. The corneal flux experiment showed many fold enhancement in permeation across goat cornea. DRZ-CS-PCL-NPs exhibited 3.7 fold higher mucoadhesive strength compared to the control. Furthermore, the histopathological assessment and HET-CAM study revealed that the DRZ-CS-PCL-NPs were non-irritant and safe for ocular administration. Therefore, from the present study, it can be concluded that the optimized DRZ-CS-PCL-NPs are safe and have the potential for successful ocular delivery and improved therapeutic efficacy.

Quaternary Ammonium Chitosans: The Importance of the Positive Fixed Charge of the Drug Delivery Systems

As a natural polysaccharide, chitosan has good biocompatibility, biodegradability and biosecurity. The hydroxyl and amino groups present in its structure make it an extremely versatile and chemically modifiable material. In recent years, various synthetic strategies have been used to modify chitosan, mainly to solve the problem of its insolubility in neutral physiological fluids. Thus, derivatives with negative or positive fixed charge were synthesized and used to prepare innovative drug delivery systems. Positively charged conjugates showed improved properties compared to unmodified chitosan. In this review the main quaternary ammonium derivatives of chitosan will be considered, their preparation and their applications will be described to evaluate the impact of the positive fixed charge on the improvement of the properties of the drug delivery systems based on these polymers. Furthermore, the performances of the proposed systems resulting from in vitro and ex vivo experiments will be taken into consideration, with particular attention to cytotoxicity of systems, and their ability to promote drug absorption.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

Therapeutic Nanoparticles and Their Targeted Delivery Applications

Nanotechnology offers many advantages in various fields of science. In this regard, nanoparticles are the essential building blocks of nanotechnology. Recent advances in nanotechnology have proven that nanoparticles acquire a great potential in medical applications. Formation of stable interactions with ligands, variability in size and shape, high carrier capacity, and convenience of binding of both hydrophilic and hydrophobic substances make nanoparticles favorable platforms for the target-specific and controlled delivery of micro- and macromolecules in disease therapy. Nanoparticles combined with the therapeutic agents overcome problems associated with conventional therapy; however, some issues like side effects and toxicity are still debated and should be well concerned before their utilization in biological systems. It is therefore important to understand the specific properties of therapeutic nanoparticles and their delivery strategies. Here, we provide an overview on the unique features of nanoparticles in the biological systems. We emphasize on the type of clinically used nanoparticles and their specificity for therapeutic applications, as well as on their current delivery strategies for specific diseases such as cancer, infectious, autoimmune, cardiovascular, neurodegenerative, ocular, and pulmonary diseases. Understanding of the characteristics of nanoparticles and their interactions with the biological environment will enable us to establish novel strategies for the treatment, prevention, and diagnosis in many diseases, particularly untreatable ones.

Impact of Different Mucoadhesive Polymeric Nanoparticles Loaded in Thermosensitive Hydrogels on Transcorneal Administration of 5-Fluorouracil

In a previous paper a thermosensitive hydrogel formulation based on chitosan or its derivatives (TSOH), containing medicated chitosan nanoparticles (Ch NP) for transcorneal administration of 5-fluorouracil (5-FU) was described. The Ch NP-containing TSOH allowed a time-constant 5-FU concentration in the aqueous for 7 h from instillation. The aim of the present work was to study the impact of the surface characteristics of new NP contained in TSOH on ocular 5-FU bioavailability. The Ch derivatives used to prepare NP were quaternary ammonium-Ch conjugate (QA-Ch), S-protected derivative thereof (QA-Ch-S-pro), and a sulphobutyl chitosan derivative (SB-Ch). All NP types had 300–400 nm size, 16–18% encapsulation efficiency, and retained the entrapped drug for at least 15 h. Drug release from TSOH containing NP based on QA-Ch or QA-Ch-S-pro was virtually equal, whereas with TSOH containing NP based on SB-Ch was significantly slower. Instillation, in rabbit eyes, of NP-containing TSOH based on QA-Ch or SB-Ch led to a plateau in the aqueous concentration vs. time plot in the 1–10 h range with significantly enhanced area under curve (AUC). Negative charges on the NP surface slowed down 5-FU release from TSOH while positive charges increased NP contact with the negatively charged ocular surface. Either results in enhanced ocular bioavailability.

Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature

Thiolated polymers designated "thiomers" are obtained by covalent attachment of thiol functionalities on the polymeric backbone of polymers. In 1998 these polymers were first described as mucoadhesive and in situ gelling compounds forming disulfide bonds with cysteine-rich substructures of mucus glycoproteins and crosslinking through inter- and intrachain disulfide bond formation. In the following, it was shown that thiomers are able to form disulfides with keratins and membrane-associated proteins exhibiting also cysteine-rich substructures. Furthermore, permeation enhancing, enzyme inhibiting and efflux pump inhibiting properties were demonstrated. Because of these capabilities thiomers are promising tools for drug delivery guaranteeing a strongly prolonged residence time as well as sustained release on mucosal membranes. Apart from that, thiomers are used as drugs per se. In particular, for treatment of dry eye syndrome various thiolated polymers are in development and a first product has already reached the market. Within this review an overview about the thiomer-technology and its potential for different applications is provided discussing especially the outcome of studies in non-rodent animal models and that of numerous clinical trials. Moreover, an overview on product developments is given.

Employing a PLGA-TPGS based nanoparticle to improve the ocular delivery of Acyclovir

Delivering drugs via the ocular route has always been a challenge for poorly soluble drugs. The various anatomical and physiological barriers in the eye cavity hinder the residence of drugs within the corneal and precorneal regions. In this study, the nanosystem that could sufficiently deliver the poorly soluble Acyclovir topically via ocular route. Our nanosystem is composed of the biocompatible PLGA polymer stabilized with TPGS which possess a high emulsifying capacity and is also known as P-gp inhibitor. The optimized nanoparticles were prepared with 0.3% TPGS and had particle-size of 262.3 nm, zeta-potential of +15.14 mV. The physicochemical-characterization, ex vivo transcorneal permeation, ocular-irritation and Acyclovir ocular-availability, following topical ocular application of PLGA-NPs in rabbit eyes, were performed. The tested parameters and irritation by Draize's test suggested the suitability and safety of PLGA-NPs for ocular use. An ultrahigh performance liquid chromatographic method was developed, validated, and applied to quantify Acyclovir in aqueous humor which was shown to be significantly higher (p < 0.05) using the developed nanoparticles as compared to Acyclovir-aqueous suspension following their single topical ocular administration. Noticeable 2.78-, 1.71- and 2.2-times increased values of AUC_0-24h, t_1/2 (h) and MRT_0-24h were found, respectively, with the PLGA-TPGS-NPs as compared to ACY-AqS. These results demonstrate the superiority of delivering Acyclovir using a nanosystem compared to conventional methods.

Impact of mucoadhesive polymeric nanoparticulate systems on oral bioavailability of a macromolecular model drug

Nanoparticles (NP) only different in mucoadhesivity are compared for impact on drug oral bioavailability. Two polymeric NP types based on quaternary ammonium-chitosan (NP QA-Ch) and S-protected thiolated derivative thereof (NP QA-Ch-S-pro), respectively, containing the macromolecular drug model, FD4, were prepared by crosslinking each polymer with reduced MW hyaluronic acid. The structure of basic polymers was determined by H¹NMR analysis. NP were similar in size (371 ± 38 vs. 376 ± 82 nm); polydispersity index (0.39 ± 0.08 vs. 0.41 ± 0.10); zeta potential (13.4 ± 0.9 vs. 11.9 ± 1.2 mV); reversible interactions with drug (bound drug, 67 vs. 66%); encapsulation efficiency (23 ± 5 vs. 23 ± 8%); release properties (15% released in 15 h in both cases); and apparent permeation across excised rat intestine (P_app, 8.8 ± 0.8 vs. 10 ± 1 cm/s). Then the differences in NP transport ratio through mucus (TR, 0.75 vs. 0.37) and adhesion to excised rat intestinal mucosa (adsorbed fraction, 23 ± 3 vs. 45 ± 2%) were ascribed to higher mucoadhesivity of NP QA-Ch-S-pro compared to NP QA-Ch. This directly influenced drug oral bioavailability in rats (T_max, 1 vs. 2 h; AUC, 1.7 ± 0.3 vs. 2.9 ± 0.4 μg/mL min, for NP QA-Ch and NP QA-Ch-S-pro, respectively). Mucoadhesivity increases drug bioavailability by retaining NP at its absorption site and opposing its transit down the GI tract. Data on drug accumulation in rat liver allows the assertion that NP is absorbed by transcytosis across intestinal epithelium and transported from blood into liver by Kuppfer cells.

A water-soluble, mucoadhesive quaternary ammonium chitosan-methyl-β-cyclodextrin conjugate forming inclusion complexes with dexamethasone

The ocular bioavailability of lipophilic drugs, such as dexamethasone, depends on both drug water solubility and mucoadhesion/permeation. Cyclodextrins and chitosan are frequently employed to either improve drug solubility or prolong drug contact onto mucosae, respectively. Although the covalent conjugation of cyclodextrin and chitosan brings to mucoadhesive drug complexes, their water solubility is restricted to acidic pHs. This paper describes a straightforward grafting of methyl-β-cyclodextrin (MCD) on quaternary ammonium chitosan (QA-Ch60), mediated by hexamethylene diisocyanate. The resulting product is a water-soluble chitosan derivative, having a 10-atom long spacer between the quaternized chitosan and the cyclodextrin. The derivative is capable of complexing the model drug dexamethasone and stable complexes were also observed for the lyophilized products. Furthermore, the conjugate preserves the mucoadhesive properties typical of quaternized chitosan and its safety as solubilizing excipient for ophthalmic applications was preliminary assessed by in vitro cytotoxicity evaluations. Taken as a whole, the observed features appear promising for future processing of the developed product into 3D solid forms, such as controlled drug delivery systems, films or drug eluting medical devices.

Nanotechnology: from In Vivo Imaging System to Controlled Drug Delivery

Science and technology have always been the vitals of human's struggle, utilized exclusively for the development of novel tools and products, ranging from micro- to nanosize. Nanotechnology has gained significant attention due to its extensive applications in biomedicine, particularly related to bio imaging and drug delivery. Various nanodevices and nanomaterials have been developed for the diagnosis and treatment of different diseases. Herein, we have described two primary aspects of the nanomedicine, i.e., in vivo imaging and drug delivery, highlighting the recent advancements and future explorations. Tremendous advancements in the nanotechnology tools for the imaging, particularly of the cancer cells, have recently been observed. Nanoparticles offer a suitable medium to carryout molecular level modifications including the site-specific imaging and targeting. Invention of radionuclides, quantum dots, magnetic nanoparticles, and carbon nanotubes and use of gold nanoparticles in biosensors have revolutionized the field of imaging, resulting in easy understanding of the pathophysiology of disease, improved ability to diagnose and enhanced therapeutic delivery. This high specificity and selectivity of the nanomedicine is important, and thus, the recent advancements in this field need to be understood for a better today and a more prosperous future.

Thermosensitive hydrogel based on chitosan and its derivatives containing medicated nanoparticles for transcorneal administration of 5-fluorouracil

A thermosensitive ophthalmic hydrogel (TSOH) – fluid at 4°C (instillation temperature), semisolid at 35°C (eye temperature), which coupled the dosing accuracy and administration ease of eyedrops with the increased ocular bioavailability of a hydrogel – was prepared by gelling a chitosan hydrochloride (ChHCl) solution (27.8 mg/mL) medicated with 1.25 mg/mL 5-fluorouracil (5-FU) with β-glycerophosphate 0.8 mg/mL. Polymer mixtures, where Ch was partially (10%, 15%, or 20%) replaced by quaternary ammonium–chitosan conjugates (QA-Ch) or thiolated derivatives thereof, were also used to modulate 5-FU-release properties of TSOH. Also, Ch-based nanoparticles (NPs; size after lyophilization and redispersion 341.5±15.2 nm, polydispersity 0.315±0.45, ζ-potential 10.21 mV) medicated with 1.25 mg/mL 5-FU prepared by ionotropic cross-linking of Ch with hyaluronan were introduced into TSOH. The 5-FU binding by TSOH polymers in the sol state was maximum with plain Ch (31.4%) and tended to decrease with increasing QA presence in polymer mixture. 5-FU release from TSOH with or without NPs was diffusion-controlled and linear in √t. The different TSOH polymers were compared on a diffusivity basis by comparing the slopes of √t plots. These showed a general decrease with NP-containing TSOH, which was the most marked with the TSOH, where Ch was 20% replaced by the derivative QA-Ch50. This formulation and that not containing NP were instilled in rabbits and the 5-FU transcorneal penetration was measured by analyzing the aqueous humor. Both TSOH solutions increased the area under the curve (0–8 hours) 3.5 times compared with the plain eyedrops, but maximum concentration for the NP-free TSOH was about 0.65 µg/mL, followed by a slow decline, while the NP-containing one showed a plateau (0.25–0.3 µg/mL) in a time interval of 0.5–7 hours. This is ascribed to the ability of this TSOH to control drug release to a zero order and that of NPs to be internalized by corneal cells.

Improving the topical ocular pharmacokinetics of an immunosuppressant agent with mucoadhesive nanoemulsions: Formulation development, in-vitro and in-vivo studies

Topical ocular conditions such as cornea transplant rejection and keratoconjunctivitis sicca (so called dry eye disease) require therapeutic concentration of immunosuppressant onto the ocular surface for prolonged period. Based on this rational, we optimized cyclosporine A (Cy-A) loaded polymeric mucoadhesive nanoemulsion (Cy-A-mN) with higher Cy-A payload, improved ocular retention, corneal and conjunctival bioavailability. The concentrations of oil, surfactant and co-surfactant needed for the stable nanoemulsion were screened followed by phase behavior study of the formulations components by the construction of pseudo-ternary phase diagrams. The concentration of chitosan was optimized according to the blinking force of eyelids. The size distribution, surface charge, mucoadhesiveness and Cy-A release were studied for Cy-A-mN along with other formulations. The corneal retention of Cy-A-mN was evaluated by gamma scintigraphy, revealing that the clearance was slowest in the case of Cy-A-mN. Biodistribution performed in rabbits showed that Cy-A-mN was able to maintain the therapeutic concentrations (≥50-300ng/g) of Cy-A in the cornea and conjunctiva over the period of 24h. The safety of formulation was confirmed by Draize's test and by measuring the ocular surface temperature.