Chemical and physical parameters of tears relevant for the design of ocular drug delivery formulations

Nanocarriers for the Delivery of Quercetin to Inhibit the UV-Induced Aggregation of γD-Crystallin

Due to gradual environmental changes like ozone layer depletion and global warming, human eyes are exposed to UV light. Exposure to UV light can be a cause of cataracts, one of the ocular diseases that may cause vision impairment. To date, lens replacement has been the only treatment available for cataracts. In our present study, we carried out an extensive examination of polyphenols as inhibitors for UV-induced aggregation of γD-crystallin. On exposure to UV-C light, γD-crystallin forms fibrils instead of amorphous aggregates. Various polyphenols were tested as inhibitors; out of them, quercetin, baicalein, and caffeic acid were found to be effective. As polyphenols are insoluble in water, nanoencapsulation was used to enhance their bioavailability. CS-TPP and CS-PLGA encapsulating systems were considered, as they form biodegradable nanocapsules. Out of three polyphenols (quercetin, baicalein, and caffeic acid), quercetin forms nanocarriers of smaller sizes, a must for crossing the retinal barrier. Quercetin nanocarriers were considered an effective system that could be used for therapeutic applications. For these nanocarriers, encapsulation efficiency and polyphenol release kinetics were studied. CS-PLGA NPs were found to have a better loading efficiency for quercetin than CS-TPP NPs.

Preparation of zinc oxide nanoparticles using laser-ablation technique: Retinal epithelial cell (ARPE-19) biocompatibility and antimicrobial activity when activated with femtosecond laser

The unusual physical, chemical, and biological features of nanoparticles have sparked considerable attention in the ophthalmological applications. This study reports the synthesis and characterization of zinc oxide nanoparticles (ZnONPs) using laser-ablation at 100 mJ with different ablation times. The synthesized ZnONPs were spherical with an average size of 10.2 nm or 9.8 nm for laser ablation times of 20 and 30 min, respectively. The ZnONPs were screened for their antimicrobial activity against ophthalmological bacteria, methicillin-resistant S. aureus (MRSA) and Pseudomonas aeruginosa. The significant decrease in bacterial growth was observed after treatment with ZnONPs in combination with 400 nm femtosecond laser irradiation. ZnONPs were investigated for their antioxidant activity and biocompatibility towards retinal epithelial cells (ARPE-19). ZnONPs showed moderate antioxidant and free radical scavenging activity. ZnONPs prepared with an ablation time of 20 min were safer and more biocompatible than those prepared with an ablation time of 30 min, which were toxic to ARPE-19 cells with LC₅₀ (11.3 μg/mL) and LC₉₀ (18.3 μg/mL). In this study, laser ablation technique was used to create ZnONPs, and it was proposed that ZnONPs could have laser-activated antimicrobial activity for ophthalmological applications.

An approach to revolutionize cataract treatment by enhancing drug probing through intraocular cell line

The purpose of this study is to prepare and characterize solid lipid nanoparticles (SLN) of N-Acetyl Carnosine (NAC) to treat cataract since surgery necessitates equipments and professional help. Cataract is believed to be formed by the biochemical approach where the crystalline eye proteins lose solubility and forms high molecular weight masses. Added advantages of SLN of NAC (henceforth referred as SLN-NAC) in the study are reduced size, sustained release and better corneal penetration of drug. The method of preparation of SLN-NAC by Mill’s method is unique in itself.

The size of the SLN-NAC was 75 ± 10 nm in the range of ideal for penetration. The in-vitro release study and the SLN-NAC formulations prepared with Mill’s method demonstrated sustained release up to 24 h following an initial burst after 1 h. The zeta potential of the prepared formulation was −22.1 ± 1 mV. Corneal permeation studies using goat corneas indicate that SLN-NAC penetration rate was higher than those from NAC eye drops. Corneal hydration studies indicated that the formulation caused no harm to the corneal cells.

Therefore it may be concluded that SLN-NAC may revolutionize cataract treatment and reversal by improving drug permeation, reducing toxicity and no damage to corneal tissue.

Nanocrystal for ocular drug delivery: hope or hype

The complexity of the structure and nature of the eye emanates a challenge for drug delivery to formulation scientists. Lower bioavailability concern of conventional ocular formulation provokes the interest of researchers in the development of novel drug delivery system. Nanotechnology-based formulations have been extensively investigated and found propitious in improving bioavailability of drugs by overcoming ocular barriers prevailing in the eye. The advent of nanocrystals helped in combating the problem of poorly soluble drugs specifically for oral and parenteral drug delivery and led to development of various marketed products. Nanocrystal-based formulations explored for ocular drug delivery have been found successful in achieving increase in retention time, bioavailability, and permeability of drugs across the corneal and conjunctival epithelium. In this review, we have highlighted the ocular physiology and barriers in drug delivery. A comparative analysis of various nanotechnology-based ocular formulations is done with their pros and cons. Consideration is also given to various methods of preparation of nanocrystals with their patented technology. This article highlights the success achieved in conquering various challenges of ocular delivery by the use of nanocrystals while emphasizing on its advantages and application for ocular formulation. The perspectives of nanocrystals as an emerging flipside to explore the frontiers of ocular drug delivery are discussed.

RES-loaded pegylated CS NPs: for efficient ocular delivery

The objective of this study is to develop resveratrol (RES) loaded polyethylene glycols (PEGs) modified chitosan (CS) nanoparticles (NPs) by ionic gelation method for the treatment of glaucoma. While increasing the concentration of PEG, the particle size and polydispersity index of the formulations increased. Entrapment efficiency and RES loading (RL) of NPs decreased while increasing PEG concentration. The in vitro release of NPs showed an initial burst release of RES (45%) followed by controlled release. Osmolality of formulations revealed that the prepared NPs were iso-osmolar with the tear. Ocular tolerance of the NPs was evaluated using hen's egg test on the chorioallantoic membrane and it showed that the NPs were non-irritant. RES-loaded PEG-modified CS NPs shows an improved corneal permeation compared with RES dispersion. Fluorescein isothiocyanate loaded CS NPs accumulated on the surface of the cornea but the PEG-modified CS NPs crossed the cornea and reached retinal choroid. RES-loaded PEG-modified CS NPs reduced the intra-ocular pressure (IOP) by 4.3 ± 0.5 mmHg up to 8 h in normotensive rabbits. These results indicate that the developed NPs have efficient delivery of RES to the ocular tissues and reduce the IOP for the treatment of glaucoma.

Tear fluid-eye drops compatibility assessment using surface tension

OBJECTIVE

To evaluate the compatibility of commercially available eye drop surface tension with the tear film physiological range and to characterize commonly used ophthalmic excipients in terms of their surface activity under eye-biorelevant conditions.

SIGNIFICANCE

There are a number of quality requirements for the eye drops (e.g. tonicity, pH, viscosity, refractive index) that needs to comply with the physiological parameters of the eye surface. However, the adjustment of surface tension properties of the eye drops to the normal range of surface tension at the air/tear fluid interface (40-46 mN/m) has received rather less attention thus far. Yet, the surface tension at the air/tear fluid interface is of vital importance for the normal function of the eye surface.

METHODS

The surface tension compatibility of the isotonic aqueous solutions of commonly used ophthalmic excipients as well as 18 approved eye drops with the tear fluid have been evaluated using surface tension method.

RESULTS

Each ophthalmic ingredient including the preservatives, solubilizing agents and thickening agents can influence the surface tension of the final formulation. In case of complex ophthalmic formulations one should also consider the possible interactions among excipients and consequent impact on overall surface activity. Out of 18 evaluated eye drops, three samples were within, 12 samples were below and three samples were above the physiological range of the tear fluid surface tension.

CONCLUSIONS

Our results provide a rationale for clinical studies aiming to assess the correlation between the eye drops surface tension and the tear film (in)stability.

Live attenuated and inactivated viral vaccine formulation and nasal delivery: potential and challenges

Vaccines are cost-effective for the prevention of infectious diseases and have significantly reduced mortality and morbidity. Novel approaches are needed to develop safe and effective vaccines against disease. Major challenges in vaccine development include stability in a suitable dosage form and effective modes of delivery. Many live attenuated vaccines are capable of eliciting both humoral and cell mediated immune responses if physicochemically stable in an appropriate delivery vehicle. Knowing primary stresses that impart instability provides a general rationale for formulation development and mode of delivery. Since most pathogens enter the body through the mucosal route, live-attenuated vaccines have the advantage of mimicking natural immunization via non-invasive delivery. This presentation will examine aspects of formulation design, types of robust dosage forms to consider, effective routes of delivery (invasive and noninvasive), and distinctions between live attenuated or inactivated vaccines.

Penetration of silicate nanoparticles into the corneal stroma and intraocular fluids

PURPOSE

The aim of this study was to investigate transmission of topical silicate nanoparticles (SiNPs) through the corneal stroma, anterior chamber, and vitreous fluids by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively.

METHODS

SiNPs with a mean diameter of 40.6 ± 5.6 nm determined by dynamic light scattering were used in this study. The permeability of SiNPs was examined across isolated corneal buttons over a 30-minute period. To visualize the transport and diffusion of nanoparticles through the corneal tissue, SiNPs were applied over the corneal surface and evaluated at 5 and 30 minutes after SiNPs loading for SEM and 15 minutes for TEM. Sections of 10-μm thickness were cut and visualized using SEM. TEM study was performed on 70- to 90-nm-thick sections. ICP-AES was used to determine the concentration of SiNPs.

RESULTS

The determined range of synthesized SiNPs by dynamic light scattering was 40 nm (41.9 ± 5.6 nm). Transmission of SiNPs through the corneal stroma was shown successfully with electron microscopic (SEM and TEM) images. The ICP-AES results revealed SiNPs in the anterior chamber and vitreous fluid.

CONCLUSIONS

Topical administration of SiNPs, as a noninvasive, and available modality with acceptable penetration through the corneal stroma and deep into the intraocular fluids including the anterior chamber and vitreous cavity, may be considered as a suitable alternative to invasive intravitreal injection of other expensive antineovascularization agents.

Nanoparticle-based topical ophthalmic formulation for sustained release of stereoisomeric dipeptide prodrugs of ganciclovir

Poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles (NP) of Val-Val dipeptide monoester prodrugs of ganciclovir (GCV) including L-Val-L-Val-GCV (LLGCV), L-Val-D-Val-GCV (LDGCV) and D-Val-L-Val-GCV (DLGCV) were formulated and dispersed in thermosensitive PLGA-PEG-PLGA polymer gel for the treatment of herpes simplex virus type 1 (HSV-1)-induced viral corneal keratitis. Nanoparticles containing prodrugs of GCV were prepared by a double-emulsion solvent evaporation technique using various PLGA polymers with different drug/polymer ratios. Nanoparticles were characterized with respect to particle size, entrapment efficiency, polydispersity, drug loading, surface morphology, zeta potential and crystallinity. Prodrugs-loaded NP were incorporated into in situ gelling system. These formulations were examined for in vitro release and cytotoxicity. The results of optimized entrapment efficiencies of LLGCV-, LDGCV- and DLGCV-loaded NP are of 38.7 ± 2.0%, 41.8 ± 1.9%, and 45.3 ± 2.2%; drug loadings 3.87 ± 0.20%, 2.79 ± 0.13% and 3.02 ± 0.15%; yield 85.2 ± 3.0%, 86.9 ± 4.6% and 76.9 ± 2.1%; particle sizes 116.6 ± 4.5, 143.0 ± 3.8 and 134.1 ± 5.2 nm; and zeta potential -15.0 ± 4.96, -13.8 ± 5.26 and -13.9 ± 5.14 mV, respectively. Cytotoxicity studies suggested that all the formulations are non-toxic. In vitro release of prodrugs from NP showed a biphasic release pattern with an initial burst phase followed by a sustained phase. Such burst effect was completely eliminated when NP were suspended in thermosensitive gels with near zero-order release kinetics. Prodrugs-loaded PLGA NP dispersed in thermosensitive gels can thus serve as a promising drug delivery system for the treatment of anterior eye diseases.

Contact lens biofuel cell tested in a synthetic tear solution

A contact lens biofuel cell was fabricated using buckypaper electrodes cured on a silicone elastomer soft contact lens. The buckypaper anode consisted of poly(methylene green) and a hydrogel matrix containing lactate dehydrogenase and nicotinamide adenine dinucleotide hydrate (NAD(+)). The buckypaper cathode was modified with 1-pyrenemethyl anthracene-2-carboxylate, and then bilirubin oxidase was immobilized within a polymer. Contact lens biofuel cell testing was performed in a synthetic tear solution at 35°C. The open circuit voltage was 0.413±0.06 V and the maximum current and power density were 61.3±2.9 µA cm(-2) and 8.01±1.4 µWc m(-2), respectively. Continuous operation for 17h revealed anode instability as output current rapidly decreased in the first 4h and then stabilized for the next 13 h. The contact lens biofuel cell presented here is a step toward achieving self-powered electronic contact lenses and ocular devices with an integrated power source.

Dye-attached magnetic poly(hydroxyethyl methacrylate) nanospheres for albumin depletion from human plasma

The selective binding of albumin on dye-affinity nanospheres was combined with magnetic properties as an alternative approach for albumin depletion from human plasma. Magnetic poly(hydroxyethyl methacrylate) (mPHEMA) nanospheres were synthesized using mini-emulsion polymerization method in the presence of magnetite powder. The specific surface area of the mPHEMA nanospheres was found to be 1302 m(2)/g. Subsequent to Cibacron Blue F3GA (CB) immobilization onto mPHEMA nanospheres, a serial characterization processing was implemented. The quantity of immobilized CB was calculated as 800 μmol/g. Ultimately, albumin adsorption performance of the CB-attached mPHEMA nanospheres from both aqueous dissolving medium and human plasma were explored.

Chlamydia trachomatis recombinant MOMP encapsulated in PLGA nanoparticles triggers primarily T helper 1 cellular and antibody immune responses in mice: a desirable candidate nanovaccine

We recently demonstrated by in vitro experiments that PLGA (poly D, L-lactide-co-glycolide) potentiates T helper 1 (Th1) immune responses induced by a peptide derived from the recombinant major outer membrane protein (rMOMP) of Chlamydia trachomatis, and may be a promising vaccine delivery system. Herein we evaluated the immune-potentiating potential of PLGA by encapsulating the full-length rMOMP (PLGA-rMOMP), characterizing it in vitro, and investigating its immunogenicity in vivo. Our hypothesis was that PLGA-rMOMP triggers Th1 immune responses in mice, which are desirable prerequisites for a C. trachomatis candidate nanovaccine. Physical-structural characterizations of PLGA-rMOMP revealed its size (approximately 272 nm), zeta potential (−14.30 mV), apparent spherical smooth morphology, and continuous slow release pattern. PLGA potentiated the ability of encapsulated rMOMP to trigger production of cytokines and chemokines by mouse J774 macrophages. Flow cytometric analyses revealed that spleen cells from BALB/c mice immunized with PLGA-rMOMP had elevated numbers of CD4+ and CD8+ T cell subsets, and secreted more rMOMP-specific interferon-gamma (Th1) and interleukin (IL)-12p40 (Th1/Th17) than IL-4 and IL-10 (Th2) cytokines. PLGA-rMOMP-immunized mice produced higher serum immunoglobulin (Ig)G and IgG2a (Th1) than IgG1 (Th2) rMOMP-specific antibodies. Notably, sera from PLGA-rMOMP-immunized mice had a 64-fold higher Th1 than Th2 antibody titer, whereas mice immunized with rMOMP in Freund’s adjuvant had only a four-fold higher Th1 than Th2 antibody titer, suggesting primarily induction of a Th1 antibody response in PLGA-rMOMP-immunized mice. Our data underscore PLGA as an effective delivery system for a C. trachomatis vaccine. The capacity of PLGA-rMOMP to trigger primarily Th1 immune responses in mice promotes it as a highly desirable candidate nanovaccine against C. trachomatis.

Eudragit-based nanosuspension of poorly water-soluble drug: formulation and in vitro-in vivo evaluation

The present study was performed to investigate potential of Eudragit RLPO-based nanosuspension of glimepiride (Biopharmaceutical Classification System class II drug), for the improvement of its solubility and overall therapeutic efficacy, suitable for peroral administration. Nanoprecipitation method being simple and less sophisticated was optimized for the preparation of nanosuspension. Physicochemical characteristics of nanosuspension in terms of size, zeta potential, polydispersity index, entrapment efficiency (% EE) and in vitro drug release were found within their acceptable ranges. The size of the nanoparticles was most strongly affected by agitation time while % EE was more influenced by the drug/polymer ratio. Differential scanning calorimetry and X-ray diffraction studies provided evidence that enhancement in solubility of drug resulted due to change in crystallinity of drug within the formulation. Stability study revealed that nanosuspension was more stable at refrigerated condition with no significant changes in particle size distribution, % EE, and release characteristics for 3 months. In vivo studies were performed on nicotinamide-streptozotocin-induced diabetic rat models for pharmacokinetic and antihyperglycaemic activity. Nanosuspension increased maximum plasma concentration, area under the curve, and mean residence time values significantly as compared to aqueous suspension. Oral glucose tolerance test and antihyperglycaemic studies demonstrated plasma glucose levels were efficiently controlled in case of nanosuspension than glimepiride suspension. Briefly, sustained and prolonged activity of nanosuspensions could reduce dose frequency, decrease drug side effects, and improve patient compliance. Therefore, glimepiride nanosuspensions can be expected to gain considerable attention in the treatment of type 2 diabetes mellitus due to its improved therapeutic activity.

HP55-coated capsule containing PLGA/RS nanoparticles for oral delivery of insulin

In this work, we designed and developed a two-stage delivery system composed of enteric capsule and cationic nanoparticles for oral delivery of insulin. The enteric capsule was coated with pH-sensitive hydroxypropyl methylcellulose phthalate (HP55), which could selectively release insulin from nanoparticles in the intestinal tract, instead of stomach. The biodegradable poly(lactic-co-glycolic acid) (PLGA) was selected as the matrix for loading insulin. Eurdragit(®) RS (RS) was also introduced to the nanoparticles for enhancing the penetration of insulin across the mucosal surface in the intestine. The nanoparticles were prepared with the multiple emulsions solvent evaporation method via ultrasonic emulsification. The optimized nanoparticles have a mean size of 285nm, a positive zeta potential of 42mV. The encapsulation efficiency was up to 73.9%. In vitro results revealed that the initial burst release of insulin from nanoparticles was markedly reduced at pH 1.2, which mimics the stomach environment. In vivo effects of the capsule containing insulin PLGA/RS nanoparticles were also investigated in diabetic rat models. The oral delivered capsules induced a prolonged reduction in blood glucose levels. The pharmacological availability was found to be approximately 9.2%. All the results indicated that the integration of HP55-coated capsule with cationic nanoparticles may be a promising platform for oral delivery of insulin with high bioavailability.

Chitosan nanoparticles for drug delivery to the eye

The purpose of this review is to provide the reader with an overview of the advances made in ocular delivery of bioactive molecules by means of chitosan-based nanosystems, and their potential relevance in clinical use. The studies described clearly emphasise that chitosan-based nanostructures are versatile systems that can be tailor-made according to required compositions, surface characteristics and particle size. Such parameters, which are known to influence their in vivo performance, can be modulated by adjusting the formulation conditions of the nanotechnologies responsible for their formation, by incorporating additional materials in the preparation steps, and/or by using synthetically modified chitosan. Moreover, this review illustrates how the advances achieved in the understanding of the interaction of nanosystems with the ocular structures should result in the coming years, logically, into challenging innovations in ocular nanomedicines with significant impact on clinical practice.

Cationic polybutyl cyanoacrylate nanoparticles for DNA delivery

To enhance the intracellular delivery potential of plasmid DNA using nonviral vectors, we used polybutyl cyanoacrylate (PBCA) and chitosan to prepare PBCA nanoparticles (NPs) by emulsion polymerization and prepared NP/DNA complexes through the complex coacervation of nanoparticles with the DNA. The object of our work is to evaluate the characterization and transfection efficiency of PBCA-NPs. The NPs have a zeta potential of 25.53 mV at pH 7.4 and size about 200 nm. Electrophoretic analysis suggested that the NPs with positive charges could protect the DNA from nuclease degradation and cell viability assay showed that the NPs exhibit a low cytotoxicity to human hepatocellular carcinoma (HepG2) cells. Qualitative and quantitative analysis of transfection in HepG2 cells by the nanoparticles carrying plasmid DNA encoding for enhanced green fluorescent protein (EGFP-N1) was done by digital fluorescence imaging microscopy system and fluorescence-activated cell sorting (FACS). Qualitative results showed highly efficient expression of GFP that remained stable for up to 96 hours. Quantitative results from FACS showed that PBCA-NPs were significantly more effective in transfecting HepG2 cells after 72 hours postincubation. The results of this study suggested that PBCA-NPs have favorable properties for nonviral delivery.

Topical ocular drug delivery to inner ear disease and sinusitis

Oral steroids are the main therapy for sensorineural deafness. We present the rare case of a patient whose hearing loss associated with inflammation of the inner ear and chronic sinusitis were improved with topical steroid therapy. A 68-year-old male presented with scleritis in the left eye, inflammation of the inner ear and chronic sinusitis. He received oral prednisolone 10 mg/d. However, the oral prednisolone was discontinued due to severe side effects. Topical administration of 0.1% betamethasone sodium phosphate improved the scleritis and incidentally also relieved his symptoms of recurrent otitis and sinusitis after several days. Audiometry revealed recovered acoustic sensation in the right ear, from 50 dB to 20 dB, and in the left ear from 70 to 35 dB with 1,000 Hz. Topical ocular drug delivery of steroids may be effective for inner ear disease and sinusitis in patients with systemic side effects to oral steroids.

Pharmacokinetics of Theophylline in Guinea Pig Tears

It is well recognized that the theophylline (TP) concentration in human tears correlates well with the free TP concentration in human plasma. However this correlation was found only in a very narrow range of concentrations of TP, and pharmacokinetic analysis of TP in tears has not been carried out for a wide range of concentrations of TP. The aims of this investigation were to develop a simple kinetic model for TP in guinea pig plasma (total [Cf+b] and free [Cf]), cerebrospinal fluid (CSF) [C](CSF) and tears [C](T), and to examine whether [Cf], [Cf+b] and [C](CSF) can be predicted from [C](T) using the resulting kinetic parameters. [Cf+b], [Cf], [C](CSF) and [C](T) were determined by GC/EI-SIM following bolus i.v. injection of TP in doses of 10, 50 and 100 mg/kg into guinea pigs. The wide range of concentrations of [Cf+b] could be quantitatively described by a two-compartment model with non-linear elimination kinetics and individual volume distribution of TP at each dose. [C](T) and [C](CSF) were analyzed using passive diffusion models with and without the pH-partition theory, respectively. The value of [Cf] could be predicted from the value of [C](T). Thus, the measurement of [C](T) which can be collected non-invasively would be a useful method for the therapeutic drug monitoring of TP.

Constant rate infusion for topical ocular delivery in horses: a pilot study

OBJECTIVE

To assess the efficacy and kinetics of a continuous infusion modality for topical ophthalmic drug delivery via subpalpebral lavage in horses.

ANIMALS STUDIED

Five ophthalmically normal horses

PROCEDURES

A constant-rate continuous delivery pump was used to apply 0.01% fluorescein solution to the eyes of five ophthalmically normal horses via subpalpebral lavage. Fluorescein was applied at a rate of 0.14 mL/h for 72 h. Tear samples were collected from the ventral conjunctival fornix at regular intervals via capillary tube and tear fluorescein concentrations were determined via spectral assay. Laboratory studies to evaluate the procedures used in the study also were performed.

RESULTS

Overall mean tear film fluorescein concentration was approximately 20% of the applied concentration of fluorescein. However, tear film fluorescein concentrations varied considerably between horses and over time. Dilution varied from 0.62% to 60% of the applied concentration. Air pockets sporadically appeared in subpalpebral lavage tubing lines, resulting in discontinuous topical application of fluorescein.

CONCLUSIONS

Constant-rate delivery of ophthalmic medications using a continuous infusion pump may provide a valuable method of topical drug delivery if tear film dilution of drugs is taken into account.

Characterization of the novel ophthalmic drug carrier Sophisen in two of its derivatives: 3A Ofteno and Modusik-A Ofteno

Sophisen, a new ophthalmic drug carrier, was characterized using physicochemical and morphological criteria. Diclofenac belongs to a nonsteroidal anti-inflammatory molecule group and its ophthalmic use avoids side effects produced by steroid drugs. Cyclosporine-A is a cyclic peptide used as an immunosuppressive when administrated systemically. Its application in ophthalmology has been reported, but it is a very poor soluble drug. Diclofenac sodium and Cyclosporine-A were mixed with Sophisen to render two new ophthalmic solutions that were named 3A Ofteno and Modusik-A Ofteno, respectively. Based on transmission electron microscopy and dynamic light scattering studies, we concluded that Sophisen is a polydisperse solution with a molecular weight of 413 +/-122 kDa, whereas 3A Ofteno and Modusik-A Ofteno are monodisperse solutions with molecular weights of 169 +/- 44 and 153 +/- 10, respectively. Sophisen was shown to be a good carrier for diclofenac sodium as evaluated by passive diffusion through the cornea. A comparative study suggests that diclofenac applied as eye drops was better tolerated when associated with Sophisen. In addition, Modusik-A Ofteno, a new aqueous solution of Cyclosporine-A, improved tear production in patients with moderate or severe dry eye condition.

Cationic vectors in ocular drug delivery

Despite extensive research in the field, the major problem in the ocular drug delivery domain still is rapid precorneal drug loss and poor corneal permeability. One of the approaches recently developed is the drug incorporation into cationic submicronic vectors which exploit the negative charges present at the corneal surface for increased residence time and penetration. This review will focus on the formulation of three main representative cationic colloids developed for ophthalmic delivery: liposomes, emulsions and nanoparticles (NP). Parameters such as choice of the vector type and size, nature of the cationic molecule, pH and ionic strength of the external phase and characteristics of the encapsulated drug will be discussed with accent on the relevance of the positive charge.

Eye irritation of low-irritant cosmetic formulations: correlation of in vitro results with clinical data and product composition

Alternative methods to the Draize eye irritation test, such as the hen's egg test-chorioallantoic membrane (HET-CAM) or the bovine corneal opacity and permeability (BCOP) tests, are currently used to evaluate the irritant potential of cosmetic or consumer products. Although, for strong irritants, the results of these tests correlate well with those of the Draize test, they appear to be less suited to identify mild irritants. In order to improve the sensitivity of alternative eye irritation tests, we developed a novel method that uses a human corneal epithelial cell line (CEPI), and the endpoints of cytotoxicity and IL-8 release. Twelve make-up removers were assessed by the HET-CAM, BCOP and CEPI tests, as well as in a clinical in-use test under ophthalmological control after their application to the external eye lid. In addition, we investigated the impact of osmolality and raw material composition on in vitro and clinical results and compared the in vitro results with those of clinical studies. Overall, although HET-CAM results were unrelated to eye discomfort and adverse clinical signs, they correlated mainly with the presence and concentration of surfactants in the test articles. BCOP scores were unrelated to clinical signs, but related mainly to glycol and sodium lactate content and concentration in the test articles. Cytotoxicity in CEPI mainly correlated with presence and concentrations of surfactants, and IL-8 release to clinical signs and/or glycol and sodium lactate concentrations. Overall, IL-8 release appeared to be the most sensitive and reliable endpoint to predict human eye tolerance to mildly irritant products. Although our results suggest that the IL-8 assay appears to be a promising screen for borderline-irritant formulations, further experiments are required to confirm and validate these preliminary results.

Lachrymal Determinations: Methods and Updates on Biopharmaceutical and Clinical Applications

This article displays different procedures used to collect lachrymal fluid and describes some of its applications. Sampling tears represents the main difficulty to produce precise and reproducible results. The direct sampling procedure consists in collecting tears with capillary tubes and has the drawback of demanding previous stimulation that induces major dilution. The indirect method does not require preliminary stimulation but has been held responsible for altering epithelium and promoting leakage from plasma. Schirmer strips and sponges are classically required. Applications are numerous in biopharmaceutical and clinical fields. The determination of endogenous components has great potentiality as a diagnostic tool, but the use of tear as a substitute of plasma does not present clinical relevance. Levels of drugs like immunosuppressive or antibiotic agents are determined in tears to verify that pharmacological concentrations are reached and frequency of administration is deduced from kinetic fitting.

Preparation and characterization of cationic PLGA nanospheres as DNA carriers

Nanoparticles formulated from biodegradable polymers such as poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) are being extensively investigated as non-viral gene delivery systems due to their controlled release characteristics and biocompatibility. PLGA nanoparticles for DNA delivery are mainly formulated by an emulsion-solvent evaporation technique using PVA as a stabilizer generating negatively charged particles and heterogeneous size distribution. The objective of the present study was to formulate cationically modified PLGA nanoparticles with defined size and shape that can efficiently bind DNA. An Emulsion-diffusion-evaporation technique to make cationic nanospheres composed of biodegradable and biocompatible co-polyester PLGA has been developed. PVA-chitosan blend was used to stabilize the PLGA nanospheres. The nanospheres were characterized by atomic force microscopy (AFM), photon-correlation spectroscopy (PCS), and Fourier transform infrared spectroscopy (FTIR). Zeta potential and gel electrophoresis studies were also performed to understand the surface properties of nanospheres and their ability to condense negatively charged DNA. The designed nanospheres have a zeta potential of 10mV at pH 7.4 and size under 200nm. From the gel electrophoresis studies we found that the charge on the nanospheres is sufficient to efficiently bind the negatively charged DNA electrostatically. These cationic PLGA nanospheres could serve as potential alternatives of the existing negatively charged nanoparticles.

Mucoadhesive ocular insert based on thiolated poly(acrylic acid): development and in vivo evaluation in humans

The aim of the study was to develop a mucoadhesive ocular insert for the controlled delivery of ophthalmic drugs and to evaluate its efficacy in vivo. The inserts tested were based either on unmodified or thiolated poly(acrylic acid). Water uptake and swelling behavior of the inserts as well as the drug release rates of the model drugs fluorescein and two diclofenac salts with different solubility properties were evaluated in vitro. Fluorescein was used as fluorescent tracer to study the drug release from the insert in humans. The mean fluorescein concentration in the cornea/tearfilm compartment as a function of time was determined after application of aqueous eye drops and inserts composed of unmodified and of thiolated poly(acrylic acid). The acceptability of the inserts by the volunteers was also evaluated. Inserts based on thiolated poly(acrylic acid) were not soluble and had good cohesive properties. A controlled release was achieved for the incorporated model drugs. The in vivo study showed that inserts based on thiolated poly(acrylic acid) provide a fluorescein concentration on the eye surface for more than 8 h, whereas the fluorescein concentration rapidly decreased after application of aqueous eye drops or inserts based on unmodified poly(acrylic acid). Moreover, these inserts were well accepted by the volunteers. The present study indicates that ocular inserts based on thiolated poly(acrylic acid) are promising new solid devices for ocular drug delivery.

A collaborative evaluation of the cytotoxicity of two surfactants by using the human corneal epithelial cell line and the WST-1 test

This study was undertaken to investigate the use of the in vitro test WST-1, an assay of cell proliferation and viability, for a preliminary safety evaluation of topical ophthalmic preparations. The cytotoxicity of two surfactants, benzalkonium chloride (BAC) and polyoxyethylene-20-stearyl ether (Brij78, PSE) was independently investigated in four laboratories in the EU by using an immortalized human corneal epithelial (HCE) cell line. The HCE cells were exposed to BAC and PSE for 5 min, 15 min, and 1 hour, and the results of the HCE-WST-1 tests were collected and compared. After one-hour exposure, the EC(50) values in BAC-treated cells in the presence of serum ranged between 0.0650 +/- 0.0284 (mean +/- SD) mM, and those in the absence of serum 0.0296 +/- 0.0081 mM. The corresponding values for PSE were 0.0581 +/-.0300 mM and 0.0228 +/-.0063 mM. There were variations in the results between different laboratories, with coefficients of variation ranging from 31 to 121%, mean 58%. The use of one-hour exposure time is to be preferred, and the elimination of serum in the culture medium is recommended to avoid both underestimation of toxic effects and variability of the test results.

Biocompatible stabilizers in the preparation of PLGA nanoparticles: a factorial design study

Poly(lactic-co-glycolic-acid) nanoparticles are often produced using the w/o/w emulsification solvent evaporation method. In most cases poly(vinyl alcohol) (PVA) is used as stabilizer of the emulsion. The goal of this study was to compare a series of polymers to PVA in a 2(2) full factorial design study. The influence of the concentration of PVA and the polymers tested on particle size and zeta potential value was evaluated before and after freeze-drying of the prepared particles. Nanoparticles were obtained with most polymers when they were used in combination with PVA. Leaving PVA out of the formulation, however, increased the size of the particles over 1 microm. Two exceptions are poloxamer and carbopol, which can be considered as valuable alternatives to PVA. Zeta potential values were usually slightly negative, the most extreme zeta potential values were measured when poloxamer and carbopol were employed. The use of gelatin type A made it possible to achieve positive values. The original 2(2) full factorial design study was further expanded to a central composite design for poloxamer and carbopol, in order to fit the measured data to a quadratic model and to calculate response surfaces.

Review on the systemic delivery of insulin via the ocular route

Systemic drug absorption from the ocular route is well known. Although there is some absorption from the conjunctival sac, the nasal meatus is the site where the majority of systemic absorption of instilled drug takes place. This article reviews the principles of systemic absorption of insulin applied topically to the eye. The physiological and pharmaceutical considerations for formulation development and the strategy of improving the systemic absorption and bioavailability of insulin are also discussed.

Cyclodextrins in topical drug formulations: theory and practice

Cyclodextrins are cyclic oligosaccharides with a hydrophilic outer surface and a somewhat lipophilic central cavity. Cyclodextrins are able to form water-soluble inclusion complexes with many lipophilic water-insoluble drugs. In aqueous solutions drug molecules located in the central cavity are in a dynamic equilibrium with free drug molecules. Furthermore, lipophilic molecules in the aqueous complexation media will compete with each other for a space in the cavity. Due to their size and hydrophilicity only insignificant amounts of cyclodextrins and drug/cyclodextrin complexes are able to penetrate into lipophilic biological barriers, such as intact skin. In general, cyclodextrins enhance topical drug delivery by increasing the drug availability at the barrier surface. At the surface the drug molecules partition from the cyclodextrin cavity into the lipophilic barrier. Thus, drug delivery from aqueous cyclodextrin solutions is both diffusion controlled and membrane controlled. It appears that cyclodextrins can only enhance topical drug delivery in the presence of water.

Assessment of tear concentrations on therapeutic drug monitoring. II. Pharmacokinetic analysis of valproic acid in guinea pig serum, cerebrospinal fluid, and tears

PURPOSE

To quantitatively describe the pharmacokinetics of valproic acid (VPA) in guinea pig serum (total [Cf+b] and free [Cf]), cerebrospinal fluid (CSF) [C]CSF and tears [C]T using a simple kinetic model, and to examine whether [Cf] and [C]CSF can be predicted by [C]T using the resulting pharmacokinetic parameters.

METHODS

[Cf+b], [Cf], [C]CSF and [C]T were determined after bolus i.v. injection of 10 or 20 mg/kg VPA using GC/ECNCI/MS.

RESULTS

[Cf+b] could be quantitatively described by a two compartment model with linear elimination kinetics. [Cf] was separately analyzed using multi-exponential equations. [C]CSF was analyzed using a simple kinetic model in which the CSF compartment is independently connected with the serum compartment by the apparent diffusion constants (KINCSF and KOUTCSF). [C]T was analyzed using the same simple kinetic model used for [C]CSF. The values of [C]CSF and [Cf] in the steady state can be represented by the following equations; [C]CSF = KINCSF/KOUTCSF x [Cf], [Cf] = KOUT/KINT x [C]T, and indicating that [Cf] and [C]CSF can be predicted by [C]T using the resulting pharmacokinetic parameters.

CONCLUSIONS

The measurement of [C]T which can be collected non-invasively and estimated the pharmacokinetic parameters for [Cf], [C]CSF, and [C]T might be a very useful method for TDM of VPA.