Diclofenac-loaded biopolymeric nanosuspensions for ophthalmic application

Formulation, development and optimization of raloxifene-loaded chitosan nanoparticles for treatment of osteoporosis

CONTEXT

Osteoporosis (OP) is a disease of skeletal system and is associated with fragility fracture at the hip, spine and wrist. Various drugs have been used to treat OP. One of them is raloxifene hydrochloride (RLX), a second-generation selective estrogen receptor modulator (SERM) approved by the USFDA. RLX possesses only 2% absolute bioavailability (BA) by oral route due to its extensive first-pass metabolism.

OBJECTIVE

The purpose of the current research work was to develop and evaluate RLX-loaded chitosan nanoparticles (CS-NPs) for treatment of OP with enhanced BA.

MATERIALS AND METHODS

The RLX-loaded CS-NPs were prepared by gelation of CS with tripolyphosphate (TPP) by ionic cross-linking. Formulation was optimized and in vitro drug release and in vivo study were performed.

RESULTS AND DISCUSSIONS

CS-NPs were formed by the ionic gelation method. The particle size, entrapment efficiency and loading efficiency varied from 216.65 to 1890 nm, 32.84 to 97.78% and 23.89 to 62.46%, respectively. Release kinetics showed diffusion-controlled and Fickian release pattern. In vivo study indicated higher plasma drug concentration with NPs administered intranasally as compared to drug suspension administered through oral route (p < 0.05). A significantly higher drug concentration in plasma was achieved in 10 min after nasal administration with respect to oral administration.

CONCLUSION

The results suggest that RLX-loaded CS-NPs have better BA and would be a promising approach for intranasal (i.n.) delivery of RLX for the treatment of OP.

Engineering of polymer-surfactant nanoparticles of doxycycline hydrochloride for ocular drug delivery

CONTEXT

Physiologic barriers of the eye, short precorneal drug residence time and poor corneal penetration are the few reasons for reduced ocular bioavailability.

OBJECTIVE

This study was aimed to develop novel polymer-surfactant nanoparticles of hydrophilic drug doxycycline hydrochloride (DXY) to improve precorneal residence time and drug penetration.

MATERIALS AND METHODS

Nanoparticles were formulated using emulsion cross-linking method and the formulation was optimized using factorial design. The prepared formulation was characterized for particle size, ζ potential, encapsulation efficiency, in vitro drug release and ex vivo drug diffusion studies. The antibacterial activity studies were also carried out against Escherichia coli and Staphylococcus aureus using the cup-plate method. In vivo eye irritation study was carried out by a modified Draize test in rabbits.

RESULTS AND DISCUSSION

The particle size was found to be in the range of 331-850 nm. About 45-80% of the drug was found to be encapsulated in the nanoparticles. In vitro release demonstrated sustained release profile. Lower flux values in case of nanoparticles as compared to DXY pure drug solution in ex vivo diffusion studies confirmed the sustained release. The nanoparticles were found to be significantly effective (p < 0.001) than DXY aqueous solution due to sustained release of doxycycline from nanoparticles in both the E. coli and S. aureus strains. The formulation was found to be stable over entire stability period.

CONCLUSION

The developed formulation is safe and suitable for sustained ocular drug delivery.

Design and optimization of PLGA-based diclofenac loaded nanoparticles

Drug based nanoparticle (NP) formulations have gained considerable attention over the past decade for their use in various drug formulations. NPs have been shown to increase bioavailability, decrease side effects of highly toxic drugs, and prolong drug release. Nonsteroidal anti-inflammatory drugs such as diclofenac block cyclooxygenase expression and reduce prostaglandin synthesis, which can lead to several side effects such as gastrointestinal bleeding and renal insufficiency. The aim of this study was to formulate and characterize diclofenac entrapped poly(lactide-co-glycolide) (PLGA) based nanoparticles. Nanoparticles were formulated using an emulsion-diffusion-evaporation technique with varying concentrations of poly vinyl alcohol (PVA) (0.1, 0.25, 0.5, or 1%) or didodecyldimethylammonium bromide (DMAB) (0.1, 0.25, 0.5, 0.75, or 1%) stabilizers centrifuged at 8,800 rpm or 12,000 rpm. The resultant nanoparticles were evaluated based on particle size, zeta potential, and entrapment efficacy. DMAB formulated NPs showed the lowest particle size (108±2.1 nm) and highest zeta potential (−27.71±0.6 mV) at 0.1 and 0.25% respectively, after centrifugation at 12,000 rpm. Results of the PVA based NP formulation showed the smallest particle size (92.4±7.6 nm) and highest zeta potential (−11.14±0.5 mV) at 0.25% and 1% w/v, respectively, after centrifugation at 12,000 rpm. Drug entrapment reached 77.3±3.5% and 80.2±1.2% efficiency with DMAB and PVA formulations, respectively. The results of our study indicate the use of DMAB for increased nanoparticle stability during formulation. Our study supports the effective utilization of PLGA based nanoparticle formulation for diclofenac.

Nanoparticles in the ocular drug delivery

Ocular drug transport barriers pose a challenge for drug delivery comprising the ocular surface epithelium, the tear film and internal barriers of the blood-aqueous and blood-retina barriers. Ocular drug delivery efficiency depends on the barriers and the clearance from the choroidal, conjunctival vessels and lymphatic. Traditional drug administration reduces the clinical efficacy especially for poor water soluble molecules and for the posterior segment of the eye. Nanoparticles (NPs) have been designed to overcome the barriers, increase the drug penetration at the target site and prolong the drug levels by few internals of drug administrations in lower doses without any toxicity compared to the conventional eye drops. With the aid of high specificity and multifunctionality, DNA NPs can be resulted in higher transfection efficiency for gene therapy. NPs could target at cornea, retina and choroid by surficial applications and intravitreal injection. This review is concerned with recent findings and applications of NPs drug delivery systems for the treatment of different eye diseases.

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.

Rivastigmine-loaded L-lactide-depsipeptide polymeric nanoparticles: decisive formulation variable optimization

The main aim of the investigation was to explore a novel L-lactide-depsipeptide copolymer for the development of rivastigmine-loaded polymeric nanoparticles. L-lactide-depsipeptide synthesis was based on the ring opening polymerization reaction of L-lactide with the cyclodepsipeptide, cyclo(Glc-Leu), using tin 2-ethyl hexanoate as an initiator. Rivastigmine-loaded nanoparticles were prepared by the single emulsion-solvent evaporation technique. The influence of various critical formulation variables like sonication time, amount of polymer, amount of drug, stabilizer concentration, drug-to-polymer ratio, and organic-to-aqueous phase ratio on particle size and entrapment efficiency was studied. The optimized formulation having a particle size of 142.2 ± 21.3 nm with an entrapment efficiency of 60.72 ± 3.72% was obtained. Increased rivastigmine entrapment within the polymer matrix was obtained with a relatively low organic-to-aqueous phase ratio and high drug-to-polymer ratio. A decrease in the average size of the nanoparticles was observed with a decrease in the amount of polymer added and an increase in the sonication time. Prolonged sonication time, however, decreased rivastigmine entrapment. From the different lyoprotectant tested, only trehalose was found to prevent nanoparticle aggregation upon application of the freeze-thaw cycle. Drug incorporation into the polymeric matrix was confirmed by the DSC and XRD study. The spherical nature of the nanoparticles was confirmed by the SEM study. The in vitro drug release study showed the sustained release of more than 90% of the drug up to 72 h. Thus, L-lactide-depsipeptide can be used as an efficient carrier for the nanoparticle preparation of rivastigmine.

Nanolipidgel for enhanced skin deposition and improved antifungal activity

The purpose of the research was to prepare and evaluate a topical nanolipidgel (NLH) of terbinafine hydrochloride (TRB), an antimycotic agent, for enhanced skin deposition and improved antifungal activity. Topical solid lipid nanoparticles (SLN) based nanolipidgel was formulated and evaluated. TRB-loaded SLNs were formulated by high-pressure homogenization technique. The stable TRB SLN dispersion was incorporated into a gel using 1% Carbopol 980 NF. Rheological evaluation and texture analysis of the TRB NLH was carried out. Skin permeation, skin deposition, antifungal activity, and occlusivity studies of the nanolipidgel formulation were carried out. The safety of the TRB NLH gel was evaluated using acute skin irritation test on New Zealand White rabbits. The SLN dispersion containing 10% of glyceryl monostearate, 3% of Tween 80, and 1% Plurol Oleique was the most stable. The optimized TRB SLN had a particle size and zeta potential value of 148.6±0.305 nm and -20.4±1.2 mV, respectively. TRB NLH had excellent rheological and texture properties to facilitate its topical application. TRB NLH showed increased skin deposition of the drug over plain (3-fold) and marketed TRB formulation (2-fold). TRB NLH had significantly enhanced antifungal activity against Candida albicans. TRB NLH showed efficient occlusivity and was non-irritant to the rabbit skin with no signs of erythema or edema. Solid lipid nanoparticles-based topical nanolipidgel of terbinafine can be an efficient, industrially scalable, and cost-effective alternative to the existing conventional formulations.

Preparation and In Vitro/Ex Vivo Evaluation of Moxifloxacin-Loaded PLGA Nanosuspensions for Ophthalmic Application

The aim of the present investigation was to prepare a colloidal ophthalmic formulation to improve the residence time of moxifloxacin. Moxifloxacin-loaded poly(dl-lactide-co-glycolide) (PLGA) nanosuspensions were prepared by using the solvent evaporation technique. The nanosuspensions were characterised physically by using different techniques like particle size, zeta potential, FTIR, DSC, and XRD analysis. In vitro and ex vivo studies of nanosuspensions were carried out using a modified USP dissolution apparatus and all-glass Franz diffusion cells, respectively. The antibacterial activities of the nanosuspension and marketed formulations were performed against S. aureus and P. aeroginosa. The moxifloxacin-loaded PLGA nanosuspensions showed uniform particle size, ranging between 164–490 nm with negative zeta potential for all batches. The percentage entrapment efficiency of the drug-loaded nano-suspension was found to be between 84.09 to 92.05%. In vitro drug release studies suggest that all of the formulations showed extended drug release profiles and follow Korsemeyer-Peppas release kinetics. In vitro corneal permeability was found to be comparable with that of the marketed formulation across isolated goat cornea, indicating the suitability of the nanosuspension formulation in the ophthalmic delivery of moxifloxacin. The optimised nano-suspension was found to be more active against S. aureus and P. aeruginosa compared to the marketed eye drops.

Preparation, characterization, in vivo biodistribution and pharmacokinetic studies of donepezil-loaded PLGA nanoparticles for brain targeting

OBJECTIVE

Alzheimer's disease (AD) is a progressive neurodegenerative disorder manifested by cognitive, memory deterioration and variety of neuropsychiatric symptoms. Donepezil is a reversible cholinesterase inhibitor used for the treatment of AD. The purpose of this work is to prepare a nanoparticulate drug delivery system of donepezil using poly(lactic-co-glycolic acid) (PLGA) for sustained release and efficient brain targeting.

MATERIALS AND METHODS

PLGA nanoparticles (NPs) were prepared by the solvent emulsification diffusion-evaporation technique and characterized for particle size, particle-size distribution, zeta potential, entrapment efficiency, drug loading and interaction studies and in vivo studies using gamma scintigraphy techniques.

RESULTS AND DISCUSSION

The size of drug-loaded NPs (drug polymer ratio 1:1) was found to be 89.67 ± 6.43 nm. The TEM and SEM images of the formulation suggested that particle size was within 20-100 nm and spherical in shape, smooth morphology and coating of Tween-80 on the NPs was clearly observed. The release behavior of donepezil exhibited a biphasic pattern characterized by an initial burst release followed by a slower and continuous sustained release. The biodistribution studies of donepezil-loaded PLGA NPs and drug solution via intravenous route revealed higher percentage of radioactivity per gram in the brain for the nanoparticulate formulation as compared with the drug solution (p < 0.05).

CONCLUSION

The high concentrations of donepezil uptake in brain due to coated NPs may help in a significant improvement for treating AD. But further, more extensive clinical studies are needed to check and confirm the efficacy of the prepared drug delivery system.

Retinal drug delivery using eyedrop preparations of poly-L-lysine-modified liposomes

The purpose of this study was to develop surface-modified liposomes that enhance the efficiency of eye drop drug delivery to the retina. Various molecular weights and concentrations of the water-soluble cationic polymer poly-L-lysine (PLL) were used to modify the surface of submicronized (100 nm) liposomes. Physicochemical properties of surface-modified liposomes were determined in vitro, and the efficiency of drug delivery to the retina was investigated in vivo. Using coumarin-6 as a model drug and fluorescent marker, we show that liposome surface modification by PLL dramatically increased delivery to mouse retina segments after eye drop administration. However, when PLL of high molecular weight (>30,000) was used at higher concentrations (>0.05%), aggregation of surface-modified liposomes increased particle size and hampered distribution to inner ocular tissues. As a result, the efficiency of drug delivery of these aggregated surface-modified liposomes was the same as unmodified liposomes. The optimal molecular weight and concentration of PLL in drug-delivering liposomes were 15,000-30,000 and 0.005%, respectively. Under these conditions, PLL-modified liposomes were not cytotoxic in corneal or conjunctival cells. In conclusion, surface-modified liposomes have great potential as effective retinal drug delivery carriers in eye drop formulations.

The characteristics and improved intestinal permeability of vancomycin PLGA-nanoparticles as colloidal drug delivery system

AIM

In the present investigation, vancomycin (VCM) biodegradable nanoparticles were developed for oral administration, with the aim of improving its intestinal permeability.

METHODS

The vancomycin-loaded nanoparticles were prepared using double-emulsion solvent evaporation method. The prepared nanoparticles were characterized for their micromeritic and crystallographic properties, particle size, zeta potential, drug loading and release. Intestinal permeability of VCM nanoparticles was determined in different concentrations using SPIP technique in rats.

RESULTS

Particle sizes were between 450 nm and 466 nm for different compositions of VCM-PLGA nanoparticles. Entrapment efficiency ranged between 38.38% and 78.6% with negative zeta (ζ) potential. The FT-IR, XRPD and DSC results ruled out any chemical interaction between the drug and PLGA. Effective intestinal permeability values of VCM nanoparticles in concentrations of 200, 300 and 400 μg/ml were significantly higher than that of solutions at the same concentrations.

CONCLUSION

Our findings suggest that PLGA nanoparticles could provide a delivery system for VCM, with enhanced intestinal permeability.

Hydroxypropylmethylcellulose films for the ophthalmic delivery of diclofenac sodium

OBJECTIVES

The aim of this study was to prepare diclofenac/hydroxypropylmethylcellulose (HPMC) and diclofenac-loaded nanoparticles/HPMC films as potential systems for ocular delivery.

METHODS

Two different concentration of the polymer were used: 1.5 and 2.0% w/v. Chitosan-hyaluronic acid nanoparticles were prepared by the ionotropic gelation technique. Nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, drug encapsulation efficiency and rheological studies. In-vitro drug studies and corneal penetration release studies were carried out. Drug release mechanism was finally evaluated by fitting the Ritger and Peppas equation to data. In addition corneal hydration level was calculated to determine whether films could damage the corneas.

KEY FINDINGS

Diclofenac HPMC films presented a faster drug release and a higher drug penetration than nanoparticles; on the contrary nanoparticles containing films were able to give a more sustained release of the drug and thus a slower diclofenac permeation through the cornea than HPMC films.

CONCLUSIONS

Nanoparticles loaded with diclofenac sodium in HPMC films may be a valuable alternative for the treatment of ocular inflammatory diseases, since these formulations offer the benefit of sustained releasing directly to the site of action.

Diclofenac/biodegradable polymer micelles for ocular applications

In this paper, methoxypoly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelle formulations as promising nano-carriers for poorly water soluble drugs were investigated for the delivery of diclofenac to the eye. Diclofenac loaded MPEG-PCL micelles were prepared by a simple solvent-diffusion method and characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), differential scanning calorimetery (DSC), etc. With the analysis of XRD and DSC, the diclofenac was present as an amorphous state in the formulation. The in vitro release profile indicated a sustained release manner of diclofenac from the micelles. Meanwhile, in vivo studies on eye irritation were performed with blank MPEG-PCL micelles (200 mg ml(-1)). The results showed that the developed MPEG-PCL micelles were non-irritants to the eyes of rabbits. In vitro penetration studies across the rabbit cornea demonstrated that the micelle formulations exhibited a 17-fold increase in penetration compared with that of diclofenac phosphate buffered saline (PBS) solution. The in vivo pharmacokinetics profile of the micelle parent drug in the aqueous humor of the rabbit was evaluated and the data showed that the diclofenac loaded MPEG-PCL micelles exhibited a 2-fold increase in AUC(0-24 h) than that of the diclofenac PBS solution eye drops. These results suggest a great potential of our micelle formulations as a novel ocular drug delivery system to improve the bioavailability of the drugs.

Design of vancomycin RS-100 nanoparticles in order to increase the intestinal permeability

PURPOSE

The purpose of this work was to preparation of vancomycin (VCM) biodegradable nanoparticles to improve the intestinal permeability, using water-in-oil-in-water (W/O/W) multiple emulsion method.

METHODS

The vancomycin-loaded nanoparticles were created using double-emulsion solvent evaporation method. Using Eudragit RS100 as a coating material. The prepared nanoparticles were identifyed for their micromeritic and crystallographic properties, drug loading, particle size, drug release, Zeta potential, effective permeability (Peff) and oral fractional absorption. Intestinal permeability of VCM nanoparticles was figured out, in different concentrations using SPIP technique in rats.

RESULTS

Particle sizes were between 362 and 499 nm for different compositions of VCM-RS-100 nanoparticles. Entrapment efficiency expansed between 63%-94.76%. The highest entrapment efficiency 94.76% was obtained when the ratio of drug to polymer was 1:3. The in vitro release studies were accomplished in pH 7.4. The results showed that physicochemical properties were impressed by drug to polymer ratio. The FT-IR, XRPD and DSC results ruled out any chemical interaction betweenthe drug and RS-100. Effective intestinal permeability values of VCM nanoparticles in concentrations of 200, 300 and 400 μg/ml were higher than that of solutions at the same concentrations. Oral fractional absorption was achieved between 0.419-0.767.

CONCLUSION

Our findings suggest that RS-100 nanoparticles could provide a delivery system for VCM, with enhanced intestinal permeability.

PLGA-based nanoparticles: an overview of biomedical applications

Poly(lactic-co-glycolic acid) (PLGA) is one of the most successfully developed biodegradable polymers. Among the different polymers developed to formulate polymeric nanoparticles, PLGA has attracted considerable attention due to its attractive properties: (i) biodegradability and biocompatibility, (ii) FDA and European Medicine Agency approval in drug delivery systems for parenteral administration, (iii) well described formulations and methods of production adapted to various types of drugs e.g. hydrophilic or hydrophobic small molecules or macromolecules, (iv) protection of drug from degradation, (v) possibility of sustained release, (vi) possibility to modify surface properties to provide stealthness and/or better interaction with biological materials and (vii) possibility to target nanoparticles to specific organs or cells. This review presents why PLGA has been chosen to design nanoparticles as drug delivery systems in various biomedical applications such as vaccination, cancer, inflammation and other diseases. This review focuses on the understanding of specific characteristics exploited by PLGA-based nanoparticles to target a specific organ or tissue or specific cells.

Theranostic nanoparticles engineered for clinic and pharmaceutics

Nanomedicine is the manipulation of human biological systems at the molecular level using nanoscale or nanostructured materials. Because nanoscale materials interact effectively with biological systems, the use of nanodiagnostics and nanotherapeutics may overcome many intractable health challenges. A variety of nanoparticles have been designed with modifiable functional surfaces and bioactive cores. The engineering of nanoparticles can result in several advantageous therapeutic and diagnostic properties including enhanced permeation and retention in the circulatory system, specific delivery of drugs to target sites, highly-efficient gene transfection, and enhanced medical imaging. These nanoscale materials offer the opportunity to detect chronic diseases early and to monitor the therapeutic effects of nanoformulated drugs used in the clinic. Many of these novel nanoparticles contain both drug(s) and imaging agent(s) within an individual nanoparticle for simultaneous disease diagnosis and therapy. Further integration of therapeutic compounds with diagnostic agents into theranostic nanoparticles would be highly beneficial. However, the unique physiochemical properties that make nanomaterials attractive for therapy and diagnosis may be also associated with potential health hazards. Our research has demonstrated that the biological response to nanomaterials is related to many factors including exposure levels, systemic accumulation and excretion profiles, tissue and organ distribution, and the age of the test subject. Therefore, when engineering new nanomaterials for clinical use, researchers need to consider these factors to minimize toxicity of nanoparticles in these applications. We have fabricated and evaluated nanomaterials such as cationic amphiphilic polymers and metallofullerenes that demonstrate both high efficiency and low toxicity in gene therapy and/or chemotherapy. In this Account, we describe the development of theranostic nanomaterials with low toxicity and illustrate their potential use as novel nanomedicines in translational research.

Stability of polylactic acid particles and release of fluorochromes upon topical application on human skin explants

Particle-based drug delivery systems allow the controlled and targeted release of incorporated active compounds to the skin and are promising tools to improve the efficacy of topical therapies. In this study we investigated the stability and release properties of biodegradable polylactic acid (PLA) particles upon topical application on human skin explants. PLA particles loaded with the hydrophilic fluorochrome 4-Di-2-Asp (DiAsp-PLA) were compared to PLA particles loaded with the lipophilic fluorochrome Bodipy 630/650 (BP-PLA). Changes of the particle morphology after their incubation on skin surface were investigated by means of electron microscopy while fluorescence microscopy and flow cytometry were used to evaluate particle penetration in hair follicles and fluorochrome release. We found that BP-PLA particles released rapidly the loaded fluorochrome and lost the particulate morphology within a few hours after application on skin surface. On the contrary, DiAsp-PLA particles maintained the particulate morphology, accumulated in hair follicles, and allowed a constant release of the incorporated fluorochrome for up to 16 h. These results show that, once applied to skin surface, PLA particles release the incorporated fluorochromes in a time-dependent manner and suggest the perspective to modulate particle stability and release properties by incorporating excipients with different degree of lipophilicity.

Biocompatibility and biodegradation studies of subconjunctival implants in rabbit eyes

Sustained ocular drug delivery is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Biodegradable subconjunctival implants with controlled drug release may circumvent these two problems. In our study, two microfilms (poly [d,l-lactide-co-glycolide] PLGA and poly[d,l-lactide-co-caprolactone] PLC were developed and evaluated for their degradation behavior in vitro and in vivo. We also evaluated the biocompatibility of both microfilms. Eighteen eyes (9 rabbits) were surgically implanted with one type of microfilm in each eye. Serial anterior-segment optical coherence tomography (AS-OCT) scans together with serial slit-lamp microscopy allowed us to measure thickness and cross-sectional area of the microfilms. In vitro studies revealed bulk degradation kinetics for both microfilms, while in vivo studies demonstrated surface erosion kinetics. Serial slit-lamp microscopy revealed no significant inflammation or vascularization in both types of implants (mean increase in vascularity grade PLGA50/50 12±0.5% vs. PLC70/30 15±0.6%; P = 0.91) over a period of 6 months. Histology, immunohistochemistry and immuno-fluorescence also revealed no significant inflammatory reaction from either of the microfilms, which confirmed that both microfilms are biocompatible. The duration of the drug delivery can be tailored by selecting the materials, which have different degradation kinetics, to suit the desired clinical therapeutic application.

Impacts of nanomedicines in ocular pharmacotherapy

INTRODUCTION

The integrity of the cells/tissues in anterior and/or posterior segments of the eye plays a crucial role in biofunctions of the vision. To maintain ocular homeostasis, selective restrictiveness of the ophthalmic membranes and barriers control must act on shuttling of biomolecules. Thus, not all attempts to apply de novo nanotechnology approaches for ocular pharmacotherapy have met with the same successes as those cited here in this review, and sometimes these novel technologies tools provoke a great deal of challenges and hurdles mainly because of functional presence of these barriers.

METHODS

Recent published articles related to applications of ocular nanomedicines were reviewed and highlighted in this review article.

RESULTS

It seems the emergence of nanomedicines have arisen great hopes for ophthalmic pharmacotherapy, in which nanostructured medicines are expected to be able to cross the restrictive barriers of the eye. Although such fast inauguration of ocular nanomedicines will literally convey new challenges in the regulatory and translational processes, it will also grant a prolific platform from which many exciting, and yet unimagined, applications of biomedical nanotechnology will emerge for pharmacotherapy of the eye.

CONCLUSION

This review provides recent advancements on ocular nanomedicines.

Development of an enhanced formulation for delivering sustained release of buprenorphine hydrochloride

To control the minimum effective dose, and reduce the number and quantity of administered potent drugs are unique features of advanced drug delivery in situ forming gel formulation. The efficacy, consistency, and increasing the application of existing injection therapies can be enhanced through optimization of controlled released systems by using FDA approved biodegradable PLGA (poly-d,l-lactide-co-glycolide) polymer. The purpose of this study was to develop different in situ forming implant (ISFI) formulations of buprenorphine hydrochloride for post treatment of drug addicts, acute and chronic pains. The drug releases from different ISFIs membranes with and without Tween 80 were compared over a period of time. Kinetic equation followed the Korsmeyer-Peppas model, as the plots showed high linearity. The influence of this additive on polymer properties was investigated using differential scanning calorimetry (DSC), and the membranes structure was studied by X-ray diffractometry (XRD) and scanning electron microscope (SEM). Data revealed that Tween 80 modified the drug release pattern using diffusion mechanism and decreased the glass transition temperature (T g) significantly. The degree of crystallinity was decreased after phase inversion which helps the dissolution of drug from membrane. The porosity of modified membranes was in accordance with release profiles. These findings suggest four different in situ forming implant formulations which can release various dose of the buprenorphine hydrochloride in a prolonged time. Also this surfactant can be an attractive additive for modifying the release rate of drugs from PLGA-based membrane drug delivery systems.

Diclofenac-loaded Eudragit S100 nanosuspension for ophthalmic delivery

In this study, diclofenac-loaded Eudragit S100-based nanosuspension was prepared by nanoprecipitation method and characterised for particle size, morphology, in vitro release, and for its in vivo ocular anti-inflammatory activity. The diclofenac-loaded Eudragit S100 nanosuspension was found to have a particle size of 172 nm, polydispersibility index of 0.14 and zeta potential of -23.7 +/- 6.07 mV, indicating that the nanosuspension is fairly stable. The nanosuspended particles were found to be spherical in shape. The nanosuspension was found to provide a sustained in vitro release, following the Higuchi square-root release kinetics. The results indicated that the nanosuspension released the drug by combination of dissolution and diffusion. The in vivo evaluation of nanosuspension in PGE(2)-induced ocular inflammation in rabbit model revealed a significantly (p  <  0.05) higher inhibition of PGE(2)-induced polymorphonuclear leukocytes migration and lid-closure scores as compared with the aqueous solution of diclofenac.

Novel mucoadhesive polysaccharide isolated from Bletilla striata improves the intraocular penetration and efficacy of levofloxacin in the topical treatment of experimental bacterial keratitis

OBJECTIVES

The objective of the present study was to evaluate a novel mucoadhesive polymer extracted from Bletilla striata for ocular delivery of 0.5% levofloxacin in rabbits, and to determine its improved efficacy against experimental keratitis.

METHODS

B. striata polysaccharide (BsP) was subjected to cell cytotoxicity and ferning tests. The pharmacokinetics and bioavailability of topically applied 0.5% levofloxacin-BsP eye drops was investigated and compared with 0.5% levofloxacin eye drops (Cravit). Experimental Staphylococcus aureus keratitis was induced and treated with levofloxacin or levofloxacin-BsP eye drops.

KEY FINDINGS

BsP markedly increased the proliferative capacity of a human corneal epithelial [corrected] cell line. The ferning test showed that BsP exhibited optimal performance as a tear fluid. The polysaccharides significantly increased intra-aqueous penetration and corneal accumulation in rabbits. Treatment with levofloxacin-BsP reduced the number of organisms more significantly than eye drops containing levofloxacin alone.

CONCLUSIONS

BsP appears to be a promising candidate as a vehicle for topical ophthalmic drug delivery, especially for antibiotics.

Zn-Al-NO(3)-layered double hydroxides with intercalated diclofenac for ocular delivery

This study was aimed to evaluate the potential use of a drug delivery system, drug-layered double hydroxide (LDH) nanocomposites for ocular delivery. Diclofenac was successfully intercalated into Zn-Al-NO(3)-LDH by coprecipitation method. The nanocomposites were characterized by particle size, elemental chemical analysis, thermogravimetric analysis, etc. A tilt bilayer of diclofenac molecules formed in the interlayer with the gallery height of 1.868 nm. In vivo precorneal retention studies were conducted with diclofenac sodium (DS) saline, diclofenac-LDH nanocomposite dispersion, 2% polyvinylpyrrolidone (PVP) K30-diclofenac-LDH nanohybrid dispersion and 10% PVP K30-diclofenac-LDH nanohybrid dispersion, separately. Compared with DS saline, all the dispersions have extended the detectable time of DS from 3h to 6h; C(max) and AUC(0-t) of diclofenac-LDH nanocomposite dispersion showed 3.1-fold and 4.0-fold increase, respectively; C(max) and AUC(0-t) of 2% PVP K30-LDH nanohybrid dispersion were about 5.3-fold and 6.0-fold enhancement, respectively. Results of the Draize test showed that no eye irritation was demonstrated in rabbits after single and repeated administration. These results suggest that this novel ocular drug delivery system appears to offer promise as a means to improving the bioavailability of drugs after ophthalmic applications.

Biodegradable levofloxacin nanoparticles for sustained ocular drug delivery

Drug delivery to ocular region is a challenging task. Only 1-2% of drug is available in eye for therapeutic action, rest of the drug is drained out through nasolachrymal drainage system and other ocular physiological barriers. To overcome these problems of conventional dosage form, novel drug delivery systems are explored like nanoparticles. In our present work, levofloxacin encapsulated poly(lactic-co-glycolic acid) nanoparticles were developed and evaluated for various parameters like particle size, ζ potential, in vitro drug release and ex vivo transcorneal permeation. Microbiological efficacy was tested against Staphylococcus aureus using cup-plate method. Precorneal residence time was studied on albino rabbits by γ scintigraphy after radiolabeling of levofloxacin by Tc-99m. Ocular tolerance was evaluated using hen's egg chorioallantoic membrane (HET-CAM) test. The developed nanoparticles were of spherical shape with a mean particle size of 190-195 nm with a ζ potential of -25 mV. The drug entrapment efficiency was found to be near 85%. In vitro drug release profile shows initial burst release followed by extended release up to 24 h. Microbiological assay showed equivalent zone of inhibition compared to marketed formulation. γ Scintigraphy images of developed formulation, suggested a good spread and good retention over precorneal area. The nanosuspension thus developed was retained for the longer time and drained out from the eye very slowly compared to marketed formulation as significant radioactivity was recorded in later in kidney and bladder. The developed nanosuspension with a mean score of 0.33 up to 24 h in HET-CAM assay, showed the nonirritant efficacy of developed formulation. The stability studies yielded a degradation constant less then 5 × 10(-4), proving a stable formulation with an arbitrary shelf life of 2 years.

Drug loaded poly[Lac(Glc-Leu)] microparticles: formulation and release characteristics

Valdecoxib has been entrapped in sub-5 microm particles of poly[Lac(Glc-Leu)] copolymer using a oil-in-water (o/w) emulsification-solvent evaporation technique. To achieve monodispersed sized particles, a microfluidizer was used as ultrasonication device. Formulation parameters such as effect of polymer load, ultrasonication time, stabilizer concentration and stirring rate have a profound effect on particle size, and polydispersity. By adjustment of these parameters, microparticles ranging from about 0.8 to more than 4 microm have been prepared.

Sparfloxacin-loaded PLGA nanoparticles for sustained ocular drug delivery

Poor ocular bioavailability of drugs (<1%) from conventional eye drops (ie, solution, suspension, and ointments) is mainly due to the physiologic barriers of the eye. In general, ocular efficacy is closely related to ocular drug bioavailability, which may be enhanced by increasing corneal drug penetration and prolonging precorneal drug residence time. In our current work, we develop and evaluate a new colloidal system, that is, poly(dl-lactide-co-glycolide) (PLGA) nanoparticles for sparfloxacin ophthalmic delivery, to improve precorneal residence time and ocular penetration. Nanoparticles were prepared by nanoprecipitation technique and characterized for various properties such as particle size, zeta potential, in vitro drug release, statistical model fitting, stability, and so forth. Microbiological assay was carried out against Pseudomonas aeruginosa using the cup-plate method. Precorneal residence time was studied in albino rabbits by gamma scintigraphy after radiolabeling of sparfloxacin by Tc-99m. Ocular tolerance of the developed nanosuspension was also studied by the Hen Egg Test-Chorioallantoic Membrane (HET-CAM) method. The developed nanosuspension showed a mean particle size in the range of 180 to 190 nm, suitable for ophthalmic application with zeta potential of -22 mV. In vitro release from the developed nanosuspension showed an extended release profile of sparfloxacin according to the Peppas model. Acquired gamma camera images showed good retention over the entire precorneal area for the developed nanosuspension compared with that of a marketed formulation. The marketed drug formulation cleared very rapidly from the corneal region and reached the systemic circulation through the nasolacrimal drainage system, as significant radioactivity was recorded in kidney and bladder after 6 hours of ocular administration, whereas the developed nanosuspension cleared at a very slow rate (P < .05) and remained at the corneal surface for longer duration, as no radioactivity was observed in the systemic circulation. HET-CAM assay with 0 score in 8 hours indicates the nonirritant property of the developed nanosuspension. The developed lyophilized nanosuspension was found to be stable for a longer duration of time than the conventional marketed formulation with a good shelf life.

FROM THE CLINICAL EDITOR

Poor ocular bioavailability of drugs (<1%) from conventional eye drops is mainly due to the eye physiological barriers. In this study, a new colloidal system, PLGA nanoparticle for sparfloxacin ophthalmic delivery was demonstrated to improve precorneal residence time and ocular penetration. The developed lyophilized nanosuspension was found to be stable for longer duration of time than conventional marketed formulations.

Preparation of hydrocortisone nanosuspension through a bottom-up nanoprecipitation technique using microfluidic reactors

In this work, the possibility of bottom-up creation of a relatively stable aqueous hydrocortisone nanosuspension using microfluidic reactors was examined. The first part of the work involved a study of the parameters of the microfluidic precipitation process that affect the size of generated drug particles. These parameters included flow rates of drug solution and antisolvent, microfluidic channel diameters, microreactors inlet angles and drug concentrations. The experimental results revealed that hydrocortisone nano-sized dispersions in the range of 80-450 nm were obtained and the mean particle size could be changed by modifying the experimental parameters and design of microreactors. The second part of the work studied the possibility of preparing a hydrocortisone nanosuspension using microfluidic reactors. The nano-sized particles generated from a microreactor were rapidly introduced into an aqueous solution of stabilizers stirred at high speed with a propeller mixer. A tangential flow filtration system was then used to concentrate the prepared nanosuspension. The nanosuspension produced was then characterized using photon correlation spectroscopy (PCS), Zeta potential measurement, transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and X-ray analysis. Results showed that a narrow sized nanosuspension composed of amorphous spherical particles with a mean particle size of 500+/-64 nm, a polydispersity index of 0.21+/-0.026 and a zeta potential of -18+/-2.84 mV was obtained. Physical stability studies showed that the hydrocortisone nanosuspension remained homogeneous with slight increase in mean particle size and polydispersity index over a 3-month period.