Lipid emulsions as a potential delivery system for ocular use of azithromycin

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

Cyclodextrin Derivative Enhances the Ophthalmic Delivery of Poorly Soluble Azithromycin

Azithromycin (AZM), a macrolide antibiotic used for the treatment of chlamydial conjunctivitis, is less effective for the treatment of this disease due to its poor bioavailability (38%). Various alternatives have been developed for improving the physicochemical properties (i.e., solubility) of the AZM without much success. To overcome the problems associated with AZM, an inclusion complex employing a modified cyclodextrin, i.e., sulfobutylether-β-cyclodextrin (SBE-β-CD), was prepared and characterized by phase solubility studies and PXRD techniques. The results portrayed the formation of an inclusion complex of AZM with SBE-β-CD in 1:2 molar stoichiometric ratios. This inclusion complex was later incorporated into a polymer matrix to prepare an in situ gel. Various combinations of Carbopol 934P and hydroxypropyl methylcellulose (HPMC K4M) polymers were used and evaluated by rheological and in vitro drug release studies. The optimized formulation (F4) containing Carbopol 934P (0.2% w/v) and HPMC K4M (0.2% w/v) was evaluated for clarity, pH, gelling capacity, drug content, rheological properties, in vitro drug release pattern, ocular irritation test, and antimicrobial efficacy. Finally, owing to the improved antimicrobial efficacy and increased residence time, the AZM:SBE-β-CD in situ gel was found to be a promising formulation for the efficient treatment of bacterial ocular disease.

Drug Delivery Challenges and Current Progress in Nanocarrier-Based Ocular Therapeutic System

Drug instillation via a topical route is preferred since it is desirable and convenient due to the noninvasive and easy drug access to different segments of the eye for the treatment of ocular ailments. The low dose, rapid onset of action, low or no toxicity to the local tissues, and constrained systemic outreach are more prevalent in this route. The majority of ophthalmic preparations in the market are available as conventional eye drops, which rendered <5% of a drug instilled in the eye. The poor drug availability in ocular tissue may be attributed to the physiological barriers associated with the cornea, conjunctiva, lachrymal drainage, tear turnover, blood-retinal barrier, enzymatic drug degradation, and reflex action, thus impeding deeper drug penetration in the ocular cavity, including the posterior segment. The static barriers in the eye are composed of the sclera, cornea, retina, and blood-retinal barrier, whereas the dynamic barriers, referred to as the conjunctival and choroidal blood flow, tear dilution, and lymphatic clearance, critically impact the bioavailability of drugs. To circumvent such barriers, the rational design of the ocular therapeutic system indeed required enriching the drug holding time and the deeper permeation of the drug, which overall improve the bioavailability of the drug in the ocular tissue. This review provides a brief insight into the structural components of the eye as well as the therapeutic challenges and current developments in the arena of the ocular therapeutic system, based on novel drug delivery systems such as nanomicelles, nanoparticles (NPs), nanosuspensions, liposomes, in situ gel, dendrimers, contact lenses, implants, and microneedles. These nanotechnology platforms generously evolved to overwhelm the troubles associated with the physiological barriers in the ocular route. The controlled-drug-formulation-based strategic approach has considerable potential to enrich drug concentration in a specific area of the eye.

Nanoemulsion delivery systems for enhanced efficacy of antimicrobials and essential oils

The ever-growing threat of new and existing infectious diseases in combination with antimicrobial resistance requires the need for innovative and effective forms of drug delivery. Optimal drug delivery systems for existing and newly developed antimicrobials can enhance drug bioavailability, enable site-specific drug targeting, and overcome current limitations of drug formulations such as short elimination half-lives, poor drug solubility, and undesirable side effects. Nanoemulsions (NE) consist of nanometer-sized droplets stabilized by emulsifiers and are typically more stable and permeable due to their smaller particle sizes and higher surface area compared to conventional emulsions. NE have been identified as a promising means of antimicrobial delivery due to their intrinsic antimicrobial properties, ability to increase drug solubility, stability, bioavailability, organ and cellular targeting potentials, capability of targeting biofilms, and potential to overcome antimicrobial resistance. Herein, we discuss non-drug loaded essential oil-based NE that can confer antimicrobial actions through predominantly physical or biochemical mechanisms without drug payloads. We also describe drug-loaded NE for enhanced antimicrobial efficacy by augmenting the potency of existing antimicrobials. We highlight the versatility of NE to be administered through multiple different routes (oral, parenteral, dermal, transdermal, pulmonary, nasal, ocular, and rectal). We summarize recent advances in the clinical translation of antimicrobial NE and shed light on future development of effective antimicrobial therapy to combat infectious diseases.

Physiological fluid interfaces: Functional microenvironments, drug delivery targets, and first line of defense

Fluid interfaces, i.e. the boundary layer of two liquids or a liquid and a gas, play a vital role in physiological processes as diverse as visual perception, oral health and taste, lipid metabolism, and pulmonary breathing. These fluid interfaces exhibit a complex composition, structure, and rheology tailored to their individual physiological functions. Advances in interfacial thin film techniques have facilitated the analysis of such complex interfaces under physiologically relevant conditions. This allowed new insights on the origin of their physiological functionality, how deviations may cause disease, and has revealed new therapy strategies. Furthermore, the interactions of physiological fluid interfaces with exogenous substances is crucial for understanding certain disorders and exploiting drug delivery routes to or across fluid interfaces. Here, we provide an overview on fluid interfaces with physiological relevance, namely tear films, interfacial aspects of saliva, lipid droplet digestion and storage in the cell, and the functioning of lung surfactant. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe therapies and drug delivery approaches targeted at fluid interfaces. STATEMENT OF SIGNIFICANCE: Fluid interfaces are inherent to all living organisms and play a vital role in various physiological processes. Examples are the eye tear film, saliva, lipid digestion & storage in cells, and pulmonary breathing. These fluid interfaces exhibit complex interfacial compositions and structures to meet their specific physiological function. We provide an overview on physiological fluid interfaces with a focus on interfacial phenomena. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe novel therapies and drug delivery approaches targeted at fluid interfaces. This sets the scene for ocular, oral, or pulmonary surface engineering and drug delivery approaches.

Lipid-Based Nanocarriers as Topical Drug Delivery Systems for Intraocular Diseases

Effective drug delivery to intraocular tissues remains a great challenge due to complex anatomical and physiological barriers that selectively limit the entry of drugs into the eye. To overcome these challenges, frequent topical application and regular intravitreal injections are currently used to achieve the desired drug concentrations into the eye. However, the repetitive installation or recurrent injections may result in several side effects. Recent advancements in the field of nanoparticle-based drug delivery have demonstrated promising results for topical ophthalmic nanotherapies in the treatment of intraocular diseases. Studies have revealed that nanocarriers enhance the intraocular half-life and bioavailability of several therapies including proteins, peptides and genetic material. Amongst the array of nanoparticles available nowadays, lipid-based nanosystems have shown an increased efficiency and feasibility in topical formulations, making them an important target for constant and thorough research in both preclinical and clinical practice. In this review, we will cover the promising lipid-based nanocarriers used in topical ophthalmic formulations for intraocular drug delivery.

Role of nano-lipid formulation of CARP-1 mimetic, CFM-4.17 to improve systemic exposure and response in osimertinib resistant non-small cell lung cancer

BACKGROUND

EGFR mutated NSCLCs have been shown to employ the use of CARP-1 in overriding the signaling inhibition of tyrosine kinase inhibitors (such as Osimertinib). CFM 4.17 is a CARP-1 inhibitor which has a promising role in overcoming Tyrosine Kinase Inhibitor (TKI) resistance when used as a pre-treatment through promoting apoptosis. Lack of solubility, hydrophobicity leading to poor systemic exposure are the limitations of CFM 4.17. This can be overcome by nano lipid-based formulation (NLPF) of CFM 4.17 which can enhance systemic exposure in preclinical animal models as well as improve therapeutic efficacy in drug-resistant cancer cell lines.

METHODS

Molecular docking simulation studies were performed for CFM 4.17. CFM 4.17-NLPF was formulated by melt dispersion technique and optimized using a Box-Behnken designed surface response methodology approach using Design Expert and MATLAB. In vitro, CFM 4.17 release studies were performed in simulated gastric fluids (SGF-pH-1.2) and simulated intestinal fluids (SIF- pH-6.8). Cell viability assays were performed with HCC827 and H1975 Osimertinib resistant and non-resistant cells in 2D and 3D culture models of Non-small cell lung cancer to determine the effects of CFM 4.17 pre-treatment in Osimertinib response. In vivo pharmacokinetics in rats were performed measuring the effects of NLPF on CFM 4.17 to improve the systemic exposure.

RESULTS

CFM 4.17 was well accommodated in the active pocket of the active site of human EGFR tyrosine kinase. CFM 4.17 NLPF was optimized with robust experimental design with particle size less than 300 nm and % entrapment efficiency of 92.3 ± 1.23. Sustained diffusion-based release of CFM 4.17 was observed from NLPF in SGF and SIFs with Peppas and Higuchi based release kinetics, respectively. CFM 4.17 pretreatment improved response by decreasing IC50 value by 2-fold when compared to single treatment Osimertinib in both 2D monolayer and 3D spheroid assays in HCC827 and H1975 Osimertinib resistant and non-resistant cells of Non-small cell lung cancer. There were no differences between CFM 4.17 NLPF and suspension in 2D monolayer culture pretreatments; however, The 3D culture assays showed that CFM 4.17 NLPF improved combination sensitivity. Pharmacokinetic analysis showed that CFM 4.17 NLPF displayed higher AUCtot (2.9-fold) and Cmax (1.18-fold) as compared to free CFM 4.17. In contrast, the animal groups administered CFM 4.17 NLPF showed a 4.73-fold (in half-life) and a 3.07-fold increase (in MRT) when compared to equivalent dosed suspension.

CONCLUSION

We have successfully formulated CFM 4.17 NLPFs by robust RSM design approach displaying improved response through sensitizing cells to Osimertinib treatment as well as improving the oral bioavailability of CFM 4.17.

Polymeric Inserts Containing Eudragit® L100 Nanoparticle for Improved Ocular Delivery of Azithromycin

Polymeric inserts containing azithromycin-loaded Eudragit® L100 nanoparticles were developed to sustain the drug release and enhance its ocular performance. The solvent diffusion technique was employed to prepare nanoparticles. The developed nanoparticles (NPs) were fully characterized and investigated. The solvent casting method was used to prepare azithromycin ocular inserts (azithromycin, AZM film) by adding hydroxypropyl methylcellulose (HPMC) or hydroxyethyl cellulose (HEC) solutions after the incorporation of AZM-loaded Eudragit® L100 nanoparticles into plasticized PVA (polyvinyl alcohol) solutions. The optimized nanoparticles had a particle size of 78.06 ± 2.3 nm, zeta potential around -2.45 ± 0.69 mV, polydispersity index around 0.179 ± 0.007, and entrapment efficiency 62.167 ± 0.07%. The prepared inserts exhibited an antibacterial effect on Staphylococcus aureus and Escherichia coli cultures. The inserts containing AZM-loaded nanoparticles showed a burst release during the initial hours, followed by a sustained drug release pattern. Higher cumulative corneal permeations from AZM films were observed for the optimized formulation compared to the drug solution in the ex-vivo trans-corneal study. In comparison to the AZM solution, the inserts significantly prolonged the release of AZM in rabbit eyes (121 h). The mucoadhesive inserts containing azithromycin-loaded Eudragit® L100 nanoparticles offer a promising approach for the ocular delivery of azithromycin (antibacterial and anti-inflammatory) to treat ocular infections that require a prolonged drug delivery.

Advanced Formulation Approaches for Ocular Drug Delivery: State-Of-The-Art and Recent Patents

The eye presents extensive perspectives and challenges for drug delivery, mainly because of the extraordinary capacity, intrinsic to this path, for drugs to permeate into the main circulatory system and also for the restrictions of the ocular barriers. Depending on the target segment of the eye, anterior or posterior, the specifications are different. The ocular route experienced in the last decades a lot of progresses related with the development of new drugs, improved formulations, specific-designed delivery and even new routes to administer a drug. Concomitantly, new categories of materials were developed and adapted to encapsulate drugs. With such advances, a multiplicity of parameters became possible to be optimized as the increase in bioavailability and decreased toxic effects of medicines. Also, the formulations were capable to easily adhere to specific tissues, increase the duration of the therapeutic effect and even target the delivery of the treatment. The ascending of new delivery systems for ocular targeting is a current focus, mainly because of the capacity to extend the normal time during which the drug exerts its therapeutic effect and, so, supplying the patients with a product which gives them fewer side effects, fewer number of applications and even more effective outcomes to their pathologies, surpassing the traditionally-used eye drops. Depending on the systems, some are capable of increasing the duration of the drug action as gels, emulsions, prodrugs, liposomes, and ocular inserts with hydrophilic properties, improving the absorption by the cornea. In parallel, other devices use as a strategy the capacity to sustain the release of the carried drugs by means of erodible and non-erodible matrices. This review discusses the different types of advanced formulations used for ocular delivery of therapeutics presenting the most recent patents according to the clinical applications.

Preparation and Evaluation of Topically Applied Azithromycin Based on Sodium Hyaluronate in Treatment of Conjunctivitis

Azithromycin (AZI) eye drops containing sodium hyaluronate (SH) were developed to improve the bioavailability of AZI. Interaction between AZI and SH in the AZI-SH formulation was investigated by differential scanning calorimetry, X-ray diffraction, and ¹H-nuclear magnetic resonance spectroscopy analyses. Moreover, advantages of using SH as an excipient were investigated by comparing physiological properties and pharmacokinetic behaviors of SH-containing AZI eye drops with that of hydroxypropyl methylcellulose (HPMC)-containing formulation. In addition, safety of the developed AZI-SH eye drops was evaluated by in vitro 3-(4,5-dimethyl-2-Thiazyl)-2, 5-diphenyl-2H-tetrazolium bromide assay (MTT assay) and neutral red uptake assay as well as in vivo eye irritation test and acute toxicity test. The results indicated that AZI formed a complex with SH under a slightly acidic condition. The area under the curve (AUC) of AZI in SH-containing formulation was 1.58-fold higher (P < 0.01) than that in HPMC-containing formulation due to the interaction between the amine group of AZI and the carboxyl group of SH, despite of the higher viscosity of HPMC-containing formulation. Safety evaluation showed that AZI-SH eye drops caused no obvious eye irritation and acute toxicity. In conclusion, the developed SH-containing AZI formulation possessing advantages of longer retention time and higher drug availability was a promising drug formulation for topical ocular therapy.

Cationic lipid emulsions as potential bioadhesive carriers for ophthalmic delivery of palmatine

Palmatine (PM) is a potent anti-infective agent used to treat eye diseases. However, PM is less effective for ocular application due to short residence time within the eyes. This study aimed to develop a cationic lipid emulsions (CLEs) for ophthalmic delivery of PM and evaluate its suitability in infection treatment. PM-loaded CLEs (PM-CLEs) were prepared through emulsifying/high-pressure homogenisation and characterised by particle size, ζ potential and morphology. The resulting PM-CLEs possessed a particle size of 192 nm and ζ potential of 45 mV around. In vitro release illustrated that PM was released less from CLEs. Corneal bioadhesion test showed that PM-CLEs exhibited an enhanced ocular residence time. Improved anti-infective activity was achieved in the model of fungus-induced keratitis. Furthermore, PM-CLEs demonstrated predominant cellular uptake and internalisation in the corneal epithelial cells. These results provide proof of concept that CLEs are promising bioadhesive carriers for ophthalmic delivery of PM.

In Vitro Anti-inflammatory and Antimicrobial Activities of Azithromycin After Loaded in Chitosan- and Tween 20-Based Oil-in-Water Macroemulsion for Acne Management

The objectives of the current investigation are (1) to prepare and characterize (particle size, surface charge (potential zeta), surface morphology by transmission electron microscopy, drug content, and drug release) the azithromycin (AZM, 100 mg)-loaded oil-in-water (o/w) macroemulsion, (2) to assess the toxicity of macroemulsion with or without AZM using RBC lysis test in comparison with AZM in phosphate buffer solution of pH 7.4, (3) to compare the in vitro antimicrobial activity (in Escherichia coli using zone inhibition assay) of AZM-loaded macroemulsion with its aqueous solution, and (4) to assess the in vitro anti-inflammatory effect (using egg albumin denaturation bioassay) of the AZM-loaded macroemulsion in comparison with diclofenac sodium in phosphate buffer solution of pH 7.4. The AZM-loaded macroemulsion possessed the dispersed oil droplets with a mean diameter value of 52.40 ± 1.55 μm. A reversal in the zeta potential value from negative (-2.16 ± 0.75 mV) to positive (+6.52 ± 0.96 mV) was noticed when AZM was added into the macroemulsion. At a 1:5 dilution ratio, 2.06 ± 0.03 mg of drug was released from macroemulsion followed by 1.01 ± 0.01 and 0.25 ± 0.08 mg, respectively, for 1:10 and 1:40 dilution ratios. Antimicrobial activity maintenance and significant reduction of RBC lysis property were noticed for AZM after loaded in the macroemulsion. However, an increment in the absorbance values for emulsion-treated samples in comparison to the control samples was noticed in the anti-inflammatory test. This speculates the potential of the AZM-loaded emulsion to manage inflammatory conditions produced at Acne vulgaris.

Parenteral formulation of larotaxel lipid microsphere tackling poor solubility and chemical instability

The purpose of this study was to develop a parenteral larotaxel lipid microsphere (LTX-LM) and evaluate its stability. The preformulation study showed that LTX possessed poor solubility (0.057 μg/mL in aqueous phase) and chemical instability. LM was selected as the drug carrier due to its higher drug-loading capacities, higher physicochemical stability and reduced irritation and toxicity. High speed shear mixing and high-pressure homogenization were employed to prepare the LTX-LM. Particle size distribution (PSD), zeta-potential, drug content and entrapment efficiency (EE) were taken as indexes to optimize formulations. The dissolution studies were performed using a ZRS-8G dissolution apparatus according to the paddle method. Degradation kinetics test, freezing and thawing test and long term stability test were combined to evaluate the physicochemical stability of LTX-LM. From the degradation kinetics results, the shelf lives (T90%) of LTX in LM at 25 and 4°C (165, 555 days) were about 20 times as long as those in aqueous phase (200, 676 h), which were dramatically prolonged. The activation energies in aqueous solution and in LM calculated from the slopes were 41.93 and 42.25 kJ/mol. And its frequency factors (A) were 4.9 × 10(3)/s and 2.3 × 10(2)/s, respectively. Freezing and thawing test showed the PSD of LTX-LM became larger and wider increasing from 166.9 ± 53.2 nm to 257.4 ± 85.5 nm with more freeze-thaw cycles. From the long term stability test results, all the parameters changes were in qualified range.

Ocular drug delivery systems: An overview

The major challenge faced by today’s pharmacologist and formulation scientist is ocular drug delivery. Topical eye drop is the most convenient and patient compliant route of drug administration, especially for the treatment of anterior segment diseases. Delivery of drugs to the targeted ocular tissues is restricted by various precorneal, dynamic and static ocular barriers. Also, therapeutic drug levels are not maintained for longer duration in target tissues. In the past two decades, ocular drug delivery research acceleratedly advanced towards developing a novel, safe and patient compliant formulation and drug delivery devices/techniques, which may surpass these barriers and maintain drug levels in tissues. Anterior segment drug delivery advances are witnessed by modulation of conventional topical solutions with permeation and viscosity enhancers. Also, it includes development of conventional topical formulations such as suspensions, emulsions and ointments. Various nanoformulations have also been introduced for anterior segment ocular drug delivery. On the other hand, for posterior ocular delivery, research has been immensely focused towards development of drug releasing devices and nanoformulations for treating chronic vitreo-retinal diseases. These novel devices and/or formulations may help to surpass ocular barriers and associated side effects with conventional topical drops. Also, these novel devices and/or formulations are easy to formulate, no/negligibly irritating, possess high precorneal residence time, sustain the drug release, and enhance ocular bioavailability of therapeutics. An update of current research advancement in ocular drug delivery necessitates and helps drug delivery scientists to modulate their think process and develop novel and safe drug delivery strategies. Current review intends to summarize the existing conventional formulations for ocular delivery and their advancements followed by current nanotechnology based formulation developments. Also, recent developments with other ocular drug delivery strategies employing in situ gels, implants, contact lens and microneedles have been discussed.

Novel NSAIDs ophthalmic formulation: flurbiprofen axetil emulsion with low irritancy and improved anti-inflammation effect

The aim of this study was to design and formulate a novel low-irritant NSAIDs ophthalmic emulsion of flurbiprofen axetil (FBA), the prodrug of flurbiprofen (FB). FBA ophthalmic emulsion (FBA-EM) was prepared by high-pressure homogenization with caster oil as oil phase and tween 80 as emulsifying agent. Results from the stability evaluation suggested the protect effect of oil droplets on the stability of FBA. Compared with FBA-oil solution, the AUC(0→10h) of FB in aqueous humor administered in FBA-EMs exhibited 6.7-fold (F2), 4.5-fold (F3) and 4.6-fold (F4) increase. With the increment of oil content, the MRT also prolonged, which of FBA-EM F2-F4 were 5.14 ± 2.23, 5.73 ± 3.35 and 8.71 ± 0.94 h, respectively. No significant difference was found between the ocular bioavailability of FBA-EM F2 and 0.03% FB-Na eye drops. Ocular irritation evaluation revealed that FBA-EM F2 had better ocular biocompatibility than 0.03% FB-Na eye drops, even though the FBA concentration was up to 0.1%. Intraocular anti-inflammation effect evaluation showed that FBA-EM F2 had a quite good anti-inflammation effect. In conclusion, FBA-EM F2 with elevated FBA concentration to be 0.1% might represent a promising NSAIDs ophthalmic emulsion with low irritancy and improved anti-inflammation effect.