A time to heal: microRNA and circadian dynamics in cutaneous wound repair.

Many biological systems have evolved circadian rhythms based on the daily cycles of daylight and darkness on Earth. Such rhythms are synchronised or entrained to 24-h cycles, predominantly by light, and disruption of the normal circadian rhythms has been linked to elevation of multiple health risks. The skin serves as a protective barrier to prevent microbial infection and maintain homoeostasis of the underlying tissue and the whole organism. However, in chronic non-healing wounds such as diabetic foot ulcers (DFUs), pressure sores, venous and arterial ulcers, a variety of factors conspire to prevent wound repair. On the other hand, keloids and hypertrophic scars arise from overactive repair mechanisms that fail to cease in a timely fashion, leading to excessive production of extracellular matrix (ECM) components such as such as collagen. Recent years have seen huge increases in our understanding of the functions of microRNAs (miRNAs) in wound repair. Concomitantly, there has been growing recognition of miRNA roles in circadian processes, either as regulators or targets of clock activity or direct responders to external circadian stimuli. In addition, miRNAs are now known to function as intercellular signalling mediators through extracellular vesicles (EVs). In this review, we explore the intersection of mechanisms by which circadian and miRNA responses interact with each other in relation to wound repair in the skin, using keratinocytes, macrophages and fibroblasts as exemplars. We highlight areas for further investigation to support the development of translational insights to support circadian medicine in the context of these cells.

Implantable drug delivery systems for the treatment of osteomyelitis.

Osteomyelitis is an infection of the bone tissue and bone marrow which is becoming increasingly difficult to treat due to the infection causing pathogens associated. Staphylococcus aureus is one of the main bacteria that causes this infection, which has a broad spectrum of antibiotic resistance making it extremely difficult to treat. Conventional metal implants used in orthopedic applications often have the drawback of implant induced osteomyelitis as well as the requirement of a second surgery to remove the implant once it is no longer required. Recently, attention has been focused on the design and fabrication of biodegradable implants for the treatment of bone infection. The main benefit of biodegradable implants over polymethylmethacrylate (PMMA) based non-degradable systems is that they do not require a second surgery for removal and so making degradable implants safer and easier to use. The main purpose of a biodegradable implant is to provide the necessary support and conductivity to allow the bone to regenerate whilst themselves degrading at a rate that is compatible with the rate of formation of new bone. They must be highly biocompatible to ensure there is no inflammation or irritation within the surrounding tissue. During this review, the latest research into antibiotic loaded biodegradable implants will be explored. Their benefits and drawbacks will be compared with those non-degradable PMMA beads, which is the stable material used within antibiotic loaded implants. Biodegradable implants most frequently used are based on biodegradable natural and synthetic polymers. Implants can take the form of many different structures; the most commonly fabricated structure is a scaffold. Other structures that will be explored within this review are hydrogels, nanoparticles and surface coatings, all with their own benefits/drawbacks.

Development of a stability-indicating UPLC method for determination of isotretinoin in bulk drug.

A highly sensitive and rapid stability indicating ultra-performance liquid chromatographic (UPLC) method was developed for the quantification and identification of isotretinoin in bulk. Chromatographic separation was developed using a gradient elution in a reversed-phase system at flow rate of 0.5 ml/min with 12 min run time. The mobile phase was a gradient mixture of mobile phase A (contained a 30:70:0.5 mixture solution of methanol/purified water/glacial acetic acid) and mobile phase B (contained a 70:25:4.5:0.5 mixture solution of methanol/acetonitrile/purified water/glacial acetic acid). Eluents were monitored at 355 nm. The analytical method was validated for accuracy, precision, robustness, linearity, and forced degradation in accordance with the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) topic Q2 (R1) 'Validation of Analytical Procedures: Text and Methodology'. The method was linear over a concentration range of (1-7 µg/ml) with correlation coefficient of (r2 > 0.9999). The accuracy was confirmed by calculating the % recovery which was found to be 100.0-101.6%. The RSD values obtained for repeatability and intermediate precision experiments were less than 2%. The limit of detection (LOD) was 0.12 µg/ml, while the limit of quantification (LOQ) was 0.38 µg/ml. The drug samples were exposed to different stressed conditions and the results showed that all degradation products were satisfactorily separated from each other and from the peak of the drug using the developed method. The proposed method can be used for the quantitative determination of isotretinoin with confidence.

Ocular delivery systems for topical application of anti-infective agents.

For the treatment of anterior eye segment infections using anti-infective agents, topical ocular application is the most convenient route of administration. However, topical delivery of anti-infective agents is associated with a number of problems and challenges owing to the unique structure of the eye and the physicochemical properties of these compounds. Topical ocular drug delivery systems can be classified into two forms: conventional and non-conventional. The efficacy of conventional ocular formulations is limited by poor corneal retention and permeation resulting in low ocular bioavailability. Recently, attention has been focused on improving topical ocular delivery of anti-infective agents using advanced drug delivery systems. This review will focus on the challenges of efficient topical ocular delivery of anti-infective agents and will discuss the various types of delivery systems used to improve the treatment anterior segment infections.

Development of gatifloxacin-loaded cationic polymeric nanoparticles for ocular drug delivery.

The present investigation aimed at improving the ocular bioavailability of gatifloxacin by prolonging its residence time in the eye and reducing problems associated with the drug re-crystallization after application through incorporation into cationic polymeric nanoparticles. Gatifloxacin-loaded nanoparticles were prepared via the nanoprecipitation and double emulsion techniques. A 50:50 Eudragit® RL and RS mixture was used as cationic polymer with other formulation parameters varied. Prepared nanoparticles were evaluated for size, zeta potential, and drug loading. An optimized formulation was selected and further characterized for in vitro drug release, cytotoxicity, and antimicrobial activity. The double emulsion method produced larger nanoparticles than the nanoprecipitation method (410 nm and 68 nm, respectively). Surfactant choice also affected particle size and zeta potential with Tween 80 producing smaller-sized particles with higher zeta potential than PVA. However, the zeta potential was positive at all experimental conditions investigated. The optimal formulation produced by double emulsion technique and has achieved 46% drug loading. This formulation had optimal physicochemical properties with acceptable cytotoxicity results, and very prolonged release rate. The particles antimicrobial activities of the selected formulation have been tested against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus and showed prolonged antimicrobial effect for gatifloxacin.

Liposomal drug delivery: a versatile platform for challenging clinical applications.

Liposomes are lipid based vesicular systems that offer novel platform for versatile drug delivery to target cell. Liposomes were first reported by Bangham and his co-workers in 1964 (1). Since then, liposomes have undergone extensive research with the prime aim to optimize encapsulation, stability, circulation time and target specific drug delivery. Manipulation of a liposome's lipid bilayer and surface decoration with selective ligands has transformed conventional liposomes into adaptable and multifunctional liposomes. Development of liposomes with target specificity provide the prospect of safe and effective therapy for challenging clinical applications. Bioresponsive liposomes offer the opportunity to release payload in response to tissue specific microenvironment. Incorporation of novel natural and synthetic materials has extended their application from stable formulations to controlled release targeted drug delivery systems. Integration and optimization of multiple features into one system revolutionized research in the field of cancer, gene therapy, immunotherapy and infectious diseases. After 50 years since the first publication, this review is aimed to highlight next generation of liposomes, their preparation methods and progress in clinical applications.

Development of mucoadhesive floating hollow beads of acyclovir with gastroretentive properties.

This study aimed at improving the oral bioavailability of acyclovir (ACV) through incorporating it into gastroretentive dosage form based on floating hollow chitosan beads. Hollow chitosan beads were prepared using a solvent free, ionotropic gelation method. The effect of formulation parameters, including chitosan molecular weight and drug concentration, on bead characteristics was studied. The drug containing formulations had yields >70.5 ± 0.31%. The entrapment efficiencies for the medium molecular weight chitosan formulations (56.29 ± 0.94%-62.75 ± 0.86%) was greater than the high molecular weight chitosan formulation (29.21 ± 0.89%). The density of all formulations was below that of gastric fluid, the greatest density observed was 0.60 ± 0.01 g cm(-3). Unsurprisingly, the formulations were immediate bouyant to different degrees in both pH 1.2 and pH 6.8 media. In addition, the chitosan beads were all seen to swell in pH 1.2 media and demonstrated mucoadhesive properties. A sustained release profile was observed from the chitosan beads, the developed formulations released drug at slower rates than a marketed ACV oral tablet. The developed system has the dual advantages of being gastroretentive, to increase oral bioavailability and releasing drug in a controlled manner, to reduce the required frequency of administration thereby promoting patient adherence.

Development of solid lipid nanoparticles and nanostructured lipid carriers for improving ocular delivery of acyclovir.

The objective of the present investigation was to improve the ocular bioavailability of acyclovir by incorporating it into solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). This required optimization of the process parameters, such as type of lipid, drug to lipid ratios, type and concentration of surfactants, and type and amount of liquid lipids used in the formulations. SLNs and NLCs were prepared by the modified hot oil in water microemuslion method. The prepared nanoparticles were evaluated for their particle size, zeta potential, entrapment efficiency, solid state characteristics, surface morphology, in vitro drug release, and permeation through excised cornea. The prepared nanoparticles were spherical and within the size range suitable for ocular drug delivery (400-777.56 nm). Incorporation of liquid oil in the structure of SLNs resulted in the formation of NLCs with high entrapment efficiency (25-91.64%) compared to SLNs (11.14%). The drug release from SLNs and NLCs was rather a surface-based phenomenon. In comparison to free drug solution, NLCs were capable of having faster permeation through the excised cornea indicating their potential enhanced corneal penetration properties. However, SLNs have reduced the permeation rate significantly. The results of the study suggest that SLNs can be successfully converted to physically superior NLCs, which have the potential to be developed further as ocular drug delivery systems for ACV.

Determination of pKa and forced degradation of the indoloquinoline antimalarial compound cryptolepine hydrochloride.

The study was aimed at determining the acid dissociation constant of cryptolepine hydrochloride and its degradation under stressed conditions. The pKa was determined using buffers in the pH range 10.4-11.6 by spectrophotometry at controlled measurement temperature (20 ± 0.5°C). The stability of the compound was investigated under various stressed conditions including neutral, acid, alkaline, light, dry heat and oxidation at different temperatures. Degradation products were analysed by HPLC. The calculated pKa values (uncorrected and corrected for ionic strength) were 11.09 ± 0.03 and 10.99 ± 0.05, respectively. A graphical approach yielded an uncorrected pKa value of 11.07. Degradation of the compound in water, 0.1 M HCl, 0.1 M NaOH and 3% hydrogen peroxide followed a first order reaction. With proper temperature control and maintenance of uniform ionic strength, a reproducible pKa of cryptolepine is obtainable by spectrophotometry. The compound was found to be highly susceptible to oxidation and relatively stable in neutral and acidic conditions but less so in a basic medium. There were no significant changes in concentration of samples exposed to light and dry heat at 60°C over the study period.

Ultrasound-Mediated Ocular Drug Delivery: From Physics and Instrumentation to Future Directions.

Drug delivery to the anterior and posterior segments of the eye is impeded by anatomical and physiological barriers. Increasingly, the bioeffects produced by ultrasound are being proven effective for mitigating the impact of these barriers on ocular drug delivery, though there does not appear to be a consensus on the most appropriate system configuration and operating parameters for this application. In this review, the fundamental aspects of ultrasound physics most pertinent to drug delivery are presented; the primary phenomena responsible for increased drug delivery efficacy under ultrasound sonication are discussed; an overview of common ocular drug administration routes and the associated ocular barriers is also given before reviewing the current state of the art of ultrasound-mediated ocular drug delivery and its potential future directions.

Isolation and characterization of degradation products of moxidectin using LC, LTQ FT-MS, H/D exchange and NMR.

This study aimed to evaluate the degradation profile and pathways, and identify unknown impurities of moxidectin under stress conditions. During the experiments, moxidectin samples were stressed using acid, alkali, heat and oxidation, and chromatographic profiles were compared with known impurities given in European Pharmacopeia (EP) monograph. Moxidectin has shown good stability under heat, while reaction with alkali produced 2-epi and ∆2,3 isomers (impurities D and E in EP) by characteristic reactions of the oxahydrindene (hexahydrobenzofuran) portion of the macrocyclic lactone. Two new, previously unreported, unknown degradation products, i.e. impurity 1 and impurity 2, detected after acid hydrolysis of moxidectin (impurity 2 was also observed to a lesser extent after oxidation), were isolated from sample matrices and identified using liquid chromatography, NMR, high-resolution FT-ICR MS, and hydrogen/deuterium exchange studies. FTMS analysis showed accurate mass of molecular ion peaks for moxidectin at m/z 640.38412, impurity 1 at m/z 656.37952 and impurity 2 at m/z 611.35684, giving rise to daughter ions traceable up to the seventh levels of MS(n) experiments and supporting the proposed structures. Both unknown impurities along with moxidectin were fully characterized by (1)H, (13)C, 1D HMBC and 2D (NOESY, COSY and HSQC) NMR experiments. The interpretation of experimental data positively identified impurity 1 as 3,4-epoxy-moxidectin and impurity 2 as 23-keto-nemadectin. The identification of new impurities and correlation of their chromatographic profiles with the EP method is very useful to establish the stability profile of moxidectin and its preparations, as well as add value to the forthcoming moxidectin finished product European Pharmacopeia monographs.

An overview on chemical derivatization and stability aspects of selected avermectin derivatives.

Naturally occurring avermectins (AVMs) and its derivatives are potent endectocide compounds, well-known for their novel mode of action against a broad range of nematode and anthropod animal parasites. In this review, chemical and pharmaceutical aspects of AVM derivatives are described including stability, synthetic and purification processes, impurities and degradation pathways, and subsequent suggestions are made to improve the chemical stability. It has been found out that unique structure of AVM molecules and presence of labile groups facilitated the derivatization of AVM into various compounds showing strong anthelmintic activity. However, the same unique structure is also responsible for labile nature related to sensitive stability profile of molecules. AVMs are found to be unstable in acidic and alkaline conditions. In addition, these compounds are sensitive to strong light, and subsequently presence of photo-isomer in animals treated topically with AVM product is well known. The pharmacoepial recommendations for addition of antioxidant into drug substance, as well as its products, arises from the fact that AVM are very sensitive to oxidation. Formations of solvates, salts, epoxides, reduction of double bonds and developing liquid formulation around pH 6.2, were some chemical approaches used to retard the degradation in AVM. This coherent review will contribute towards the better understanding of the correlation of chemical processes, stability profile and biological activity; therefore, it will help to design the shelf-life stable formulations containing AVMs.

Design and in vitro haemolytic evaluation of cryptolepine hydrochloride-loaded gelatine nanoparticles as a novel approach for the treatment of malaria.

Cryptolepine hydrochloride-loaded gelatine nanoparticles were developed and characterised as a means of exploring formulation techniques to improve the pharmaceutic profile of the compound. Cryptolepine hydrochloride-loaded gelatine-type (A) nanoparticles were developed base on the double desolvation approach. After optimisation of formulation parameters including temperature, stirring rate, incubation time polymer and cross-linker (glutaraldehyde) concentrations, the rest of the study was conducted at two different formulation pH values (2.5 and 11.0) and by two different approaches to drug loading. Three cryoprotectants--sucrose, glucose and mannitol--were investigated for possible use for the preparation of freeze-dried samples. Nanoparticles with desired size mostly less than 350 nm and zeta potential above ±20 were obtained when formulation pH was between 2.5 and 5 and above 9. Entrapment efficiency was higher at pH 11.0 than pH 2.5 and for products formulated when drug was loaded during the second desolvation stage compared to when drug was loaded onto pre-formed nanoparticles. Further investigation of pH effect showed a new isoelectric point of 6.23-6.27 at which the zeta potential of nanoparticles was zero. Sucrose and glucose were effective in low concentrations as cryoprotectants. The best formulation produced an EC(50) value of 227.4 µM as a haemolytic agent compared to 51.61 µM by the free compound which is an indication of reduction in haemolytic side effect. There was sustained released of the compound from all formulation types over a period of 192 h. Stability data indicated that the nanosuspension and freeze-dried samples were stable at 4 and 25°C, respectively, over a 52-week period, but the former was less stable at room temperature. In conclusion, cryptolepine hydrochloride-loaded gelatine nanoparticles exhibited reduced haemolytic effect compared to the pure compound and can be developed further for parenteral delivery.

Chitosan nanoparticles for enhancing drugs and cosmetic components penetration through the skin.

Chitosan nanoparticles (CT NPs) have attractive biomedical applications due to their unique properties. This present research aimed at development of chitosan nanoparticles to be used as skin delivery systems for cosmetic components and drugs and to track their penetration behaviour through pig skin. CT NPs were prepared by ionic gelation technique using sodium tripolyphosphate (TPP) and Acacia as crosslinkers. The particle sizes of NPs appeared to be dependent on the molecular weight of chitosan and concentration of both chitosan and crosslinkers. CT NPs were positively charged as demonstrated by their Zeta potential values. The formation of the nanoparticles was confirmed by FTIR and DSC. Both SEM and TEM micrographs showed that both CT-Acacia and CT:TPP NPs were smooth, spherical in shape and are distributed uniformly with a size range of 200nm to 300 nm. The CT:TPP NPs retained an average of 98% of the added water over a 48-hour period. CT-Acacia NPs showed high moisture absorption but lower moisture retention capacity, which indicates their competency to entrap polar actives in cosmetics and release the encapsulated actives in low polarity skin conditions. The cytotoxicity studies using MTT assay showed that CT NPs made using TPP or Acacia crosslinkers were similarly non-toxic to the human dermal fibroblast cells. Cellular uptake study of NPs observed using live-cell imaging microscopy, proving the great cellular internalisation of CT:TPP NPs and CT-Acacia NPs. Confocal laser scanning microscopy revealed that CT NPs of particle size 530nm containing fluorescein sodium salt as a marker were able to penetrate through the pig skin and gather in the dermis layer. These results show that CT NPs have the ability to deliver the actives and cosmetic components through the skin and to be used as cosmetics and dermal drug delivery system.

Controlling of systemic absorption of gliclazide through incorporation into alginate beads.

This work investigates preparation of biodegradable beads with alginate polymer by ionotropic gelation method to take the advantages of the swelling and mucoadhesive properties of alginate beads for improving the oral delivery of the antidiabetic agent gliclazide. It demonstrates that the ionic gelation of alginate molecules offers a flexible and easily controllable process for manipulating the characteristics of the beads which are important in controlling the release rate and consequently the absorption of gliclazide from the gastrointestinal tract. Variations in polymer concentration, stirring speed, internal phase volume and the type of surfactant in the external phase were examined systemically for their effects on the particle size, incorporation efficiency and flow properties of the beads. The swelling behavior was strongly dependent on the polymer concentration in the formulations and the pH of the medium. The in vitro release experiments revealed that the swelling is the main parameter controlling the release rate of gliclazide from the beads. In vivo studies on diabetic rabbits showed that the hypoglycemic effect induced by the gliclazide loaded alginate beads was significantly greater and more prolonged than that induced by the marketed conventional gliclazide tablet (Gliclazide). The results clearly demonstrated the ability of the system to maintain tight blood glucose level and improved the patient compliance by enhancing, controlling and prolonging the systemic absorption of gliclazide.

Nanosizing techniques for improving bioavailability of drugs.

The poor solubility of significant number of Active Pharmaceutical Ingredients (APIs) has become a major challenge in the drug development process. Drugs with poor solubility are difficult to formulate by conventional methods and often show poor bioavailability. In the last decade, attention has been focused on developing nanocrystals for poorly water soluble drugs using nanosizing techniques. Nanosizing is a pharmaceutical process that changes the size of a drug to the sub-micron range in an attempt to increase its surface area and consequently its dissolution rate and bioavailability. The effectiveness of nanocrystal drugs is evidenced by the fact that six FDA approved nanocrystal drugs are already on the market. The bioavailabilities of these preparations have been significantly improved compared to their conventional dosage forms. There are two main approaches for preparation of drug nanocrystals; these are the top-down and bottom-up techniques. Top-down techniques have been successfully used in both lab scale and commercial scale manufacture. Bottom-up approaches have not yet been used at a commercial level, however, these techniques have been found to produce narrow sized distribution nanocrystals using simple methods. Bottom-up techniques have been also used in combination with top-down processes to produce drug nanoparticles. The main aim of this review article is to discuss the various methods for nanosizing drugs to improve their bioavailabilities.

Development of biodegradable PLGA nanoparticles surface engineered with hyaluronic acid for targeted delivery of paclitaxel to triple negative breast cancer cells.

This study aimed at development of poly (lactic-co-glycolic acid) (PLGA) nanoparticles embedded with paclitaxel and coated with hyaluronic acid (HA-PTX-PLGA) to actively target the drug to a triple negative breast cancer cells. Nanoparticles were successfully fabricated using a modified oil-in-water emulsion method. The effect of various formulations parameters on the physicochemical properties of the nanoparticles was investigated. SEM imaging confirmed the spherical shape and nano-scale size of the nanoparticles. A sustained drug release profile was obtained and enhanced PTX cytotoxicity was observed when MDA-MB-231 cells were incubated with the HA-PTX-PLGA formulation compared to cells incubated with the non-HA coated nanoparticles. Moreover, HA-PLGA nanoparticles exhibited improved cellular uptake, based on a possible receptor mediated endocytosis due to interaction of HA with CD44 receptors when compared to non-coated PLGA nanoparticles. The non-haemolytic potential of the nanoparticles indicated the suitability of the developed formulation for intravenous administration.

Gastroretentive Formulations for Improving Oral Bioavailability of Drugs-Focus on Microspheres and their Production.

Oral administration is the most commonly used drug delivery route for the majority of conditions. Given its advantages over other routes, such as convenience and cost, its use is increasing every year despite the major advances in drug delivery. Nevertheless, oral formulations are limited and challenged by physicochemical barriers and highly variable residence times. Gastric retention is a strategy that can overcome the highly variable gastric residence time by designing formulations that remain in the stomach longer than would otherwise be expected. This is especially beneficial for drugs that have an absorption window in the stomach and proximal intestine. Various techniques are discussed and include gasgenerating tablets, floating microspheres, hydrodynamically balanced systems, bioadhesive particles, rafts and modified shape systems. Microspheres having the advantages of being multi-unit are further discussed with regard to their production methods and characterisation. Further, a summary of microsphere studies is presented that looks at methods used and key results.

Transdermal delivery of propranolol hydrochloride through chitosan nanoparticles dispersed in mucoadhesive gel.

This study aimed at improving the systemic bioavailability of propranolol-HCl by the design of transdermal drug delivery system based on chitosan nanoparticles dispersed into gels. Chitosan nanoparticles were prepared by ionic gelation technique using tripolyphosphate (TPP) as a cross-linking agent. Characterization of the nanoparticles was focused on particle size, zeta potential, surface texture and morphology, and drug encapsulation efficiency. The prepared freeze dried chitosan nanoparticles were dispersed into gels made of poloxamer and carbopol and the rheological behaviour and the adhesiveness of the gels were investigated. The results showed that smallest propranolol loaded chitosan nanoparticles were achieved with 0.2% chitosan and 0.05% TPP. Nanoparticles were stable in suspension with a zeta potential (ZP) above ±30mV to prevent aggregation of the colloid. Zeta potential was found to increase with increasing chitosan concentration due to its cationic nature. At least 70% of entrapment efficiency and drug loading were achieved for all prepared nanoparticles. When chitosan nanoparticles dispersed into gel consisting of poloxamer and carbopol, the resultant formulation exhibited thixotropic behaviour with a prolonged drug release properties as shown by the permeation studies through pig ear skin. Our study demonstrated that the designed nanoparticles-gel transdermal delivery system has a potential to improve the systemic bioavailability and the therapeutic efficacy of propranolol-HCl.

Ex vivo and In vivo Evaluation of Chitosan Coated Nanostructured Lipid Carriers for Ocular Delivery of Acyclovir.

BACKGROUND: Herpes keratitis is the most common infectious cause of blindness in the developed world. It may be treated by acyclovir (ACV), however this antiviral drug is poorly soluble with low ocular bioavailability requiring high and frequent dosing. Nanostructured lipid carriers (NLCs) were investigated to improve the ocular bioavailability of ACV by enhancing corneal penetration as well as prolonging the exposure of infected cells to the antiviral agent. METHODS: Cell uptake studies, ex vivo tolerance and cell uptake efficacy as well as in vivo corneal permeation of the developed lipid based formulations were investigated. NLCs were fabricated by the hot microemulsion technique and coated with 0.5% w/v chitosan. NLCs were capable of increasing the cell uptake of encapsulated fluorescein and ACV as examined by fluorescence microscopy and high performance liquid chromatography (HPLC) respectively. RESULTS: When entrapped in NLCs, the antiviral efficacy of ACV was increased by 3.5 fold after 24 hrs of exposure. The in vivo corneal permeation of the formulation was studied on Albino rabbits with NLCs capable of increasing the corneal bioavailability by 4.5 fold when compared to a commercially available ACV ophthalmic ointment. CONCLUSION: NLCs enhanced the ocular bioavailability and antiviral properties of ACV through cell internalisation, sustained release, and increased corneal permeation.