Evaluation of pilocarpine-loaded albumin particles as drug delivery systems for controlled delivery in the eye I. In vitro and in vivo characterisation

Navigating albumin-based nanoparticles through various drug delivery routes

As a natural polymer, albumin is well-received for being nontoxic, nonimmunogenic, biodegradable and biocompatible. Together with its targeting potential on specific cells, albumin-based nanoparticles appear as an effective carrier for various therapeutics. In recent years, there has been an increasing number of studies investigating the use of albumin-based nanoparticles across different administration routes. Although each route and target tissue presents a distinct anatomical and physiological profile that demands specific consideration, pharmaceuticals could still be delivered effectively via albumin-based nanoparticles. Therefore, this review discusses the features that warrant such applications across various delivery routes and explores their possibilities in other administration routes. The challenges associated with its use will also be elaborated to provide a holistic consideration to realise their clinical potentials.

Nanoparticles for drug delivery to the anterior segment of the eye

Commercially available ocular drug delivery systems are effective but less efficacious to manage diseases/disorders of the anterior segment of the eye. Recent advances in nanotechnology and molecular biology offer a great opportunity for efficacious ocular drug delivery for the treatments of anterior segment diseases/disorders. Nanoparticles have been designed for preparing eye drops or injectable solutions to surmount ocular obstacles faced after administration. Better drug pharmacokinetics, pharmacodynamics, non-specific toxicity, immunogenicity, and biorecognition can be achieved to improve drug efficacy when drugs are loaded in the nanoparticles. Despite the fact that a number of review articles have been published at various points in the past regarding nanoparticles for drug delivery, there is not a review yet focusing on the development of nanoparticles for ocular drug delivery to the anterior segment of the eye. This review fills in the gap and summarizes the development of nanoparticles as drug carriers for improving the penetration and bioavailability of drugs to the anterior segment of the eye.

Impact of albumin based approaches in nanomedicine: Imaging, targeting and drug delivery

A major challenge in the field of nanomedicine is to transform laboratory innovations into commercially successful clinical products. In this campaign, a variety of nanoenabled approaches have been designed and investigated for their role in biomedical applications. The advantages associated with the unique structure of albumin imparts it with the ability to interact with variety of molecules, while the functional groups present on their surface provide base for large number of modifications making it as an ideal nanocarrier system. So far, a variety of albumin based nanoenabled approaches have been intensively exploited for effective diagnosis and personalized medicine, among them some have successfully completed their journey from lab bench to marketed products. This review focuses on the recent most promising advancement in the field of albumin based nanoenabled approaches for various biomedical applications and their potential use in cancer diagnosis and therapy.

Mucoadhesive nanoparticles for prolonged ocular delivery of natamycin: In vitro and pharmacokinetics studies

The aim of this study was to prepare natamycin encapsulated lecithin/chitosan mucoadhesive nanoparticles (NPs) for prolonged ocular application. These NPs were characterized by their mean particle size 213nm, encapsulation efficiency 73.57%, with a theoretical drug loading 5.09% and zeta potential +43. In vitro release exhibited a biphasic drug release profile with initial burst followed by a very slow drug release. The MIC(90) and zone of inhibition of NPs showed similar antifungal activity as compared to marketed suspension and free natamycin against Candida albicans and Aspergillus fumigates. The ocular pharmacokinetics of NPs and marketed formulation were evaluated in NZ rabbits. The NPs exhibit significant mucin adhesion. The AUC((0-∞)) was increased up to 1.47 fold and clearance was decreased up to 7.4-fold as compared to marketed suspension. The PK-PD and pharmacokinetic simulation was carried out to estimate optimum dosing regimen for good efficacy. Thus, lecithin/chitosan NPs could be considered useful approach aiming to prolong ocular residence and reduce dosing frequency.

Albumin-based nanoparticles as potential controlled release drug delivery systems

Albumin, a versatile protein carrier for drug delivery, has been shown to be nontoxic, non-immunogenic, biocompatible and biodegradable. Therefore, it is ideal material to fabricate nanoparticles for drug delivery. Albumin nanoparticles have gained considerable attention owing to their high binding capacity of various drugs and being well tolerated without any serious side-effects. The current review embodies an in-depth discussion of albumin nanoparticles with respect to types, formulation aspects, major outcomes of in vitro and in vivo investigations as well as site-specific drug targeting using various ligands modifying the surface of albumin nanoparticles with special insights to the field of oncology. Specialized nanotechnological techniques like desolvation, emulsification, thermal gelation and recently nano-spray drying, nab-technology and self-assembly that have been investigated for fabrication of albumin nanoparticles, are also discussed. Nanocomplexes of albumin with other components in the area of drug delivery are also included in this review.

Comparative study of topical application of timolol and verapamil in patients with glaucoma within 6 months

INTRODUCTION

As glaucoma is one of the most significant causes of blindness, and administration of calcium channel blockers is effective in reducing intraocular pressure (IOP) in rabbits and patients with normotensive glaucoma, we administered topical verapamil 0.25% in the human eye to compare its effect with timolol 0.5% in reducing IOP.

PURPOSE

To compare the effect of timolol 0.5% and topical verapamil 0.25% in patients with open-angle glaucoma.

METHODS

It was a double-blinded study in which 118 eyes (59 individuals) were chosen and divided into 2 groups (30 individuals related to timolol and 29 individuals related to verapamil). Patients who used drugs (systemic or topical) that could alter IOP and those with IOP <22 mmHg were excluded from the study (19 eyes). We chose patients who did not use any drugs 24 h prior to the study. Then applanation tonometry was done exactly before the administration of drugs and 90 min later and the results were compared.

RESULTS

In timolol group, mean intraocular pressure in 52 eyes (27 right eyes and 25 left eyes) decreased from 32.545 to 30.230 and mean pressure in verapamil group decreased from 33.195 to 30.835.

CONCLUSION

It seems that topical verapamil has a similar effect to timolol in patients with open-angle glaucoma, so it can be considered as a lowering intraocular pressure agent in glaucoma patients.

Cyclosporine a-loaded solid lipid nanoparticles: ocular tolerance and in vivo drug release in rabbit eyes

PURPOSE

To determine the in vivo efficacy of cyclosporine A-loaded solid lipid nanoparticles (SLNs) in rabbit eyes.

METHODS

SLNs were prepared and administered to the cul-de-sac of rabbits, and the drug amount in aqueous humor was detected by high performance liquid chromatography (HPLC). The irritation was evaluated by modified Draize testing.

RESULTS

The particle size of SLNs was detected as 225.9 +/- 5.5 nm with a negative surface charge. Aqueous humor drug levels reached 50.53 ng/mL, and there was no serious irritation in rabbit eyes.

CONCLUSIONS

Topical ophthalmic efficacy of cyclosporine A was enhanced via administration of SLNs.

Development of an ex vivo method for evaluation of precorneal residence of topical ophthalmic formulations

This paper describes the development of an ex vivo perfusion method for the evaluation of topical ophthalmic formulations. The perfusion system developed consisted of a perfusion chamber, two precision pumps to control the in/out flow rates to simulate the tear flow rate, and a fluorescence microscope imager. Freshly excised rat cornea was used as a biomembrane. Fluorescein (FITC) was used as a marker. Residence time was determined by measuring fluorescence intensity over time after application of the formulation to the cornea. In addition, viscoelastic properties of the formulations were measured and correlated to the retention times. The perfusion method easily differentiated formulations based on the retention time on the cornea: For example, a 0.3% hydroxypropyl methylcellulose formulation had a short retention time of <10 min. Addition of 0.25% carboxymethylcellulose increased the retention time from less than 10 min to over 16 min, and addition of 0.1% Carbopol further increased retention time to over 40 min. For alginate formulations, the retention time was significantly longer in the presence of 0.06% calcium chloride than that of 0.006% calcium chloride. The longer residence time at a higher Ca++ concentration can be attributed to the greater elastic modulus associated with the gel. Interestingly, however, a hyaluronate formulation displayed a very long retention time but has low viscoelastic moduli. This suggests that the mucoadhesive properties may not always be discernable by the rheological properties. The ex vivo perfusion method may in fact provide more meaningful information with regard to retention times of formulations.

Diclofenac-loaded biopolymeric nanosuspensions for ophthalmic application

Polymeric nanoparticle suspensions (NS) were prepared from poly(lactide-co-glycolide) and poly(lactide-co-glycolide-leucine) {poly[Lac(Glc-Leu)]} biodegradable polymers and loaded with diclofenac sodium (DS), with the aim of improving the ocular availability of the drug. NS were prepared by emulsion and solvent evaporation technique and characterized on the basis of physicochemical properties, stability, and drug release features. The nanoparticle system showed an interesting size distribution suitable for ophthalmic application. Stability tests (as long as 6 months' storage at 5 degrees C or at 25 degrees C/60% relative humidity) or freeze-drying were carried out to optimize a suitable pharmaceutical preparation. In vitro release tests showed a extended-release profile of DS from the nanoparticles. To verify the absence of irritation toward the ocular structures, blank NS were applied to rabbit eye and a modified Draize test performed. Polymer nanoparticles seemed to be devoid of any irritant effect on cornea, iris, and conjunctiva for as long as 24 hours after application, thus apparently a suitable inert carrier for ophthalmic drug delivery.

Chitosan nanoparticles for prolonged delivery of timolol maleate

Timolol maleate-loaded chitosan (CS) nanoparticles were prepared by desolvation method. Experimental variables such as molecular weight of CS and amount of crosslinking agent were varied to study their effect on drug entrapment efficiency, size and release rates of nanoparticles. Chemical stability of timolol maleate (TM) and crosslinking of CS were confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetric studies were performed on drug-loaded nanoparticles to investigate crystalline nature of the drug after entrapment. Results indicated amorphous dispersion of drug in the polymer matrix. Scanning electron microscopy revealed irregularly shaped particles. Mean particle size of nanoparticles ranged between 118 and 203 nm, while zeta potential ranged between +17 and +22 mV. Entrapment efficiency of nanoparticles ranged between 47.6 and 63.0%. In-vitro release studies were performed in phosphate buffer saline of pH 7.4. A slow release of TM up to 24 h was observed. A 3(2) full factorial design was employed and second-order regression models were used to study the response (% drug release at 4 h). Release data as analyzed by an empirical relationship suggested that drug release deviated from the Fickian trend.

Preparation and characterization of eudragit retard nanosuspensions for the ocular delivery of cloricromene

The purpose of this study was to improve the stability of cloricromene (AD6) in ophthalmic formulations and its drug availability at the ocular level. To this end, AD6-loaded polymeric nanoparticle suspensions were made using inert polymer resins (Eudragit RS100 and RL100). We modified the quasi-emulsion solvent diffusion technique by varying some formulation parameters (the drug-to-polymer ratio, the total drug and polymer amount, and the stirring speed). The chemical stability of AD6 in the nanosuspensions was assessed by preparing some formulations using (unbuffered) isotonic saline or a pH 7 phosphate buffer solution as the dispersing medium. The formulations were stored at 4 degrees C, and the rate of degradation of AD6 was followed by high performance liquid chromatography (HPLC). The obtained nanosuspensions showed mean sizes and a positive surface charge (zeta-potential) that make them suitable for an ophthalmic application; these properties were maintained upon storage at 4 degrees C for several months. In vitro dissolution tests confirmed a modified release of the drug from the polymer matrixes. Nanosuspensions prepared with saline solution and no or lower amounts of surfactant (Tween 80) showed an enhanced stability of the ester drug for several months, with respect to an AD6 aqueous solution. Based on the technological results, AD6-loaded Eudragit Retard nanoparticle suspensions appear to offer promise as a means to improving the shelf life and bioavailability of this drug after ophthalmic application.

Ocular tolerability of Eudragit RS100 and RL100 nanosuspensions as carriers for ophthalmic controlled drug delivery

Polymeric nanoparticle suspensions were prepared from inert polymer resins (Eudragit RS100, RS, and RL100, RL). When loaded with drugs, these resins have been recently proposed as delivery systems to prolong the release and improve ocular availability of the drug. To verify the absence of toxicity toward the ocular structures, blank RS and RL nanosuspensions were applied to rabbit eye and a modified Draize test was performed. Polymer nanoparticles appeared to be avoiding of any irritant effect on cornea, iris, and conjunctiva up to 24 h after application, thus appearing to be a suitable inert carrier for ophthalmic drug delivery.

Enhanced ocular anti-inflammatory activity of ibuprofen carried by an Eudragit RS100 nanoparticle suspension

PURPOSE

To investigate the ocular pharmacodynamic profile of a polymer nanoparticle system loaded with sodium ibuprofen (IBU-RS) in comparison to an aqueous solution of ibuprofen lysinate (IBL) in the rabbit eye both being applied topically.

METHODS

Ocular inflammation was elicited by topical application of sodium arachidonate. Inflammation was quantified according to a modified Draize test. The protein level and the number of polymorphonuclear leukocytes in the aqueous humor were assessed after 2 h from arachidonate instillation. The ibuprofen concentration in the aqueous humor was evaluated by HPLC assay. The physico-chemical properties of nanoparticles were also evaluated.

RESULTS

The IBU-RS nanosuspension formulation significantly reduced the primary signs of ocular inflammation as well as significantly reducing the protein level and the number of polymorphonuclear leukocytes in the aqueous humor compared with the IBL formulation. Furthermore, the aqueous humor drug concentration from the group treated with IBU-RS was significantly higher compared to the IBL-treated group. The IBU-RS nanosuspensions showed very interesting size and surface charge values, adequate for ophthalmic administration.

CONCLUSIONS

The pharmacological profile of the topical IBU-RS nanosuspension formulation described in this study indicates that the dispersion of the drug within RS polymer nanoparticles increased its ocular bioavailability and ultimately its pharmacological activity.

Flurbiprofen-loaded acrylate polymer nanosuspensions for ophthalmic application

Polymeric nanoparticle suspensions were prepared from Eudragit RS100R and RL100R polymer resins and loaded with flurbiprofen (FLU), with the aim at improving the availability of the drug at an intra-ocular level for the prevention of the myosis induced during extracapsular cataract surgery. Nanosuspensions were prepared by a quasi-emulsion solvent diffusion technique using different formulation parameters (drug-to-polymer ratio, initial polymer concentration, agitation speed, etc.). The resulting nanoparticles showed mean sizes around 100 nm and a fixed positive charge (zeta-potential around +40/+60 mV). Stability tests after mid-time storage (4 degrees C or room temperature) or freeze-drying were carried out to optimise a possible final pharmaceutical preparation. In vitro, dissolution tests showed a controlled release profile of FLU from the nanoparticles. In vivo anti-inflammatory efficacy was assessed in the rabbit eye after induction of an ocular trauma (paracentesis). FLU-loaded nanosuspensions did not show toxicity on ocular tissues. Moreover, an inhibition of the miotic response to the surgical trauma comparable to a control eye-drop formulation was obtained, even though an actual lower concentration of free drug in the conjunctival sac was achieved from the nanoparticle system. Drug levels in the aqueous humour were also higher after application of the nanosuspensions.

Eudragit RS100 nanosuspensions for the ophthalmic controlled delivery of ibuprofen

Topical application of non-steroidal anti-inflammatory drugs on the eye is a common treatment used to contrast the miosis induced by surgical traumas, such as cataract extraction. With the aim of improving the availability of sodium ibuprofen (IBU) at the intraocular level, IBU-loaded polymeric nanoparticle suspensions were made from inert polymer resins (Eudragit RS100). The nanosuspensions were prepared by a modification of the quasi-emulsion solvent diffusion technique using variable formulation parameters (drug-to-polymer ratio, total drug and polymer amount, stirring speed). Nanosuspensions had mean sizes around 100 nm and a positive charge (zeta-potential of +40/+60 mV), this makes them suitable for ophthalmic applications. Stability tests (up to 24 months storage at 4 degrees C or at room temperature) or freeze-drying were carried out to optimize a suitable pharmaceutical preparation. In vitro dissolution tests indicated a controlled release profile of IBU from nanoparticles. In vivo efficacy was assessed on the rabbit eye after induction of an ocular trauma (paracentesis). An inhibition of the miotic response to the surgical trauma was achieved, comparable to a control aqueous eye-drop formulation, even though a lower concentration of free drug in the conjunctival sac was reached from the nanoparticle system. Drug levels in the aqueous humour were also higher after application of the nanosuspensions; moreover, IBU-loaded nanosuspensions did not show toxicity on ocular tissues.

Penetration enhancers and ocular bioadhesives: two new avenues for ophthalmic drug delivery

This review is focused on the two avenues of development that promise a major impact on future ocular drug therapeutics: bioadhesives, including hydrogels and other agents like carbopols, polyacrylic acids, chitosan, etc., and penetration enhancers, including different surfactants, calcium chelators, etc. The capacity of some polymers to adhere to the mucin coat covering the conjunctiva and the corneal surface of the eye forms the basis for ocular mucoadhesion. These systems markedly prolong the residence time of a drug in the conjunctival sac, since clearence is now controlled by the much slower rate of mucus turnover rather than the tear turnover rate. But improving the corneal drug retention alone is inadequate in bringing about a significant improvement of drug bioavailability. Another approach consists of transiently increasing the pentration characteristics of the cornea with appropriate substances, known as penetration enhancers or absorption promoters. The main aim of this article is to give an insight into the potential application of mucoadhesives and corneal penetration enhancers for the conception of innovative opthalmic delivery appraoches, to decrease the systemic side effects, and create a more focused effect, which may be achieved with lower doses of the drug. Ophthalmic formulations based on these mucoadhesives and penetration enhancers are simple to manufacture and exhibit an excellent tolerance when administered into the cornea. The use of the former considerably prolongs the corneal contact time and the use of the latter increases the rate and amount of drug transport. The various corneal epithelial barriers along with the major routes of transport of drugs are discussed. The article includes a list of the various substances in use or under investigation for the aforementioned properties, along with their mechanisms of action. A fair appraisal of the subject with regard to these two therapeutic approaches and any expected ill effects has been made.

Ophthalmic drug delivery systems--recent advances

Eye-drops are the conventional dosage forms that account for 90% of currently accessible ophthalmic formulations. Despite the excellent acceptance by patients, one of the major problems encountered is rapid precorneal drug loss. To improve ocular drug bioavailability, there is a significant effort directed towards new drug delivery systems for ophthalmic administration. This chapter will focus on three representative areas of ophthalmic drug delivery systems: polymeric gels, colloidal systems, cyclodextrins and collagen shields. Hydrogels generally offer a moderate improvement of ocular drug bioavailability with the disadvantage of blurring of vision. In situ activated gel-forming systems are preferred as they can be delivered in drop form with sustained release properties. Colloidal systems including liposomes and nanoparticles have the convenience of a drop, which is able to maintain drug activity at its site of action and is suitable for poorly water-soluble drugs. Among the new therapeutic approaches in ophthalmology, cyclodextrins represent an alternative approach to increase the solubility of the drug in solution and to increase corneal permeability. Finally, collagen shields have been developed as a new continuous-delivery system for drugs that provide high and sustained levels of drugs to the cornea, despite a problem of tolerance. It seems that new tendency of research in ophthalmic drug delivery systems is directed towards a combination of several drug delivery technologies. There is a tendency to develop systems which not only prolong the contact time of the vehicle at the ocular surface, but which at the same time slow down the elimination of the drug. Combination of drug delivery systems could open a new directive for improving results and the therapeutic response of non-efficacious systems.

Influence of sterilization processes on poly(epsilon-caprolactone) nanospheres

Polymeric vectors and especially poly(epsilon-caprolactone) nanoparticles have already shown promising results in the optimization of the ophthalmic bioavailability of drugs. Any formulation instilled in the eye must be sterile, and preferentially isotonic. Poly(epsilon-caprolactone) nanospheres were thus formulated with Synperonic PE/F68, Synperonic PE/F127, or Cremophor RH40. A tonicity agent, a preservative and, in some cases, a viscosifiant were then added. The pH was finally adjusted to pH 4 or buffered to pH 7. Different sterilization processes were studied to investigate their influence on the physicochemical characteristics of vectors. Autoclaving did not induce any modification on polymer molecular weight or Synperonic nanospheres diameter, but catalysed some reactions with surfactants and tonicity agents. This method could thus be used if the nanosphere excipients are chosen with care. gamma radiation induced preservative degradation and viscosifiant depolymerization. A cross-linking of poly(epsilon-caprolactone) chains was observed, as reflected by a sharp increase of its molecular weight. However, no variation of the mean particle size was detected. Finally, sterile filtration was the only process which ensured the conservation of physicochemical integrity of nanospheres. This process was successfully applied on non-viscosified vectors with a sufficiently small diameter.