Biodegradable PLGA-Based Drug Delivery Systems for Modulating Ocular Surface Disease under Experimental Murine Dry Eye

OBJECTIVE

Continuous drug delivery to the ocular surface remains difficult due to the rapid tear clearance of topically applied agents. The purpose of this study was to evaluate biodegradable and biocompatible drug delivery systems on the ocular surface using poly-lactic-co-glycolic acid (PLGA) based polymers.

METHODS

Fluorescein-labeled albumin and doxycycline were individually encapsulated into a PLGA-based matrix using a water-oil-water double emulsion method. The drug elution rates for various microspheres were evaluated spectrofluorometrically. Particle size was measured using image analysis software. Subconjunctival injections of PLGA microspheres were used to evaluate safety and inflammatory response to the polymer in the murine model. Efficacy of the drug delivery system was evaluated by a single subconjunctival injection of PLGA-doxycycline (a broad metalloproteinase inhibitor) prior to induction of desiccating stress (DS) model in C57BL/6 mice for 5 days.

RESULTS

PLGA-based microspheres successfully elute encapsulated drugs of interest continuously over controlled periods of time. Mean PLGA-based microparticle diameter was 4.6 μm±1.54 μm. Drug elution rates and delivery times were easily modifiable by altering polymers and synthesis parameters. In vitro studies demonstrate successful continuous elution of encapsulated drugs for at least 2 weeks. In vivo testing of PLGA-doxycycline was efficacious in preventing DS-induced corneal barrier disruption with desiccating stress, similarly to topically applied doxycycline.

CONCLUSIONS

PLGA-based drug delivery systems are safe and non-inflammatory. They can be successfully used to treat ocular surface and corneal diseases by continuously delivering biopharmaceuticals of interest.

A Case of Atrophoderma of Pasini and Pierini Associated with Borrelia burgdorferi Infection Successfully Treated with Oral Doxycycline

Atrophoderma of Pasini and Pierini is a form of dermal atrophy that manifests as either single or multiple, sharply demarcated, hyperpigmented, non-indurated patches. These patches are marked by a slight depression of the skin, with an abrupt edge (i.e., the "cliff-drop" borders), usually located on the backs of adolescents or young adults. The pathophysiology of the disease is unknown, but some authors have suggested a role of Borrelia burgdorferi infection. A 35-year-old woman visited our department because of asymptomatic, hypopigmented, depressed patches on her chest and back lasting for three months. Laboratory evaluations were normal, except for positive serum antibodies to Borrelia burgdorferi. Histologic examination revealed a significantly decreased thickness of the dermis. The patient underwent treatment with oral doxycycline 200 mg/day for six weeks, after which the depth of depression was improved. Herein, we report a case of atrophoderma of Pasini and Pierini, associated with Borrelia burgdorferi infection, successfully treated with oral doxycycline.

Doxycycline blocks gastric ulcer by regulating matrix metalloproteinase-2 activity and oxidative stress

AIM: To examine the effect of doxycycline on the activity of matrix metalloproteinases (MMPs) and oxidative stress in gastric tissues of rats following gastric injury.

METHODS: Gastric ulcers were generated in rats by administration of 70% ethanol, and activity of doxycycline was tested by administration 30 min prior to ethanol. Similarly, the effect of doxycycline was tested in an indomethacin-induced gastric ulcer model. The activities and expression of MMPs were examined by zymography and Western blot analysis.

RESULTS: Gastric injury in rats as judged by elevated ulcer indices following exposure to ulcerogen, either indomethacin or ethanol, was reversed significantly by doxycycline. Indomethacin-induced ulcerated gastric tissues exhibited about 12-fold higher proMMP-9 activity and about 5-fold higher proMMP-3 activity as compared to control tissues. Similarly, ethanol induced about 22-fold and about 6-fold higher proMMP-9 and proMMP-3 activities, respectively, in rat gastric tissues. Both proMMP-9 and MMP-3 activities were markedly decreased by doxycycline in ulcerogen treated rat gastric tissues. In contrast, the reduced MMP-2 activity in ulcerated tissues was increased by doxycycline during ulcer prevention. On the other hand, doxycycline inhibited significantly proMMP-9, -2 and -3 activities in vitro. In addition, doxycycline reduced oxidative load in gastric tissues and scavenged H₂O₂in vitro. Our results suggest a novel regulatory role of doxycycline on MMP-2 activity in addition to inhibitory action on MMP-9 and MMP-3 during prevention of gastric ulcers.

CONCLUSION: This is the first demonstration of dual action of doxycycline, that is, regulation of MMP activity and reduction of oxidative stress in arresting gastric injury.

Spontaneous corneal perforation in ocular rosacea

Rosacea is a dermatologic condition that affects the midfacial region. Ocular rosacea is most frequently diagnosed when cutaneous signs and symptoms are also present. Ocular manifestations are essentially confined to the eyelids and ocular surface. Ocular involvement ranges from minor irritation, dryness, and blurry vision to potentially severe ocular surface disruption including corneal ulcers, vascularization and rarely perforation. We present a 49-year-old Saudi Arabian female with the diagnosis of rosacea who presented with a peripheral corneal performation. The perforation was successfully managed by surgical repair, oral doxycycline and topical steroid. The final best corrected visual acuity was 20/30 after treatment. Early referral to an ophthalmologist and careful long-term follow-up are recommended.

River blindness: an old disease on the brink of elimination and control

For decades, onchocerciasis (or river blindness) was one of the most common infectious causes of blindness in the world. Primarily an infection of Africa, with limited distribution in the new world, disease due to the nematode Onchocerca volvulus is rapidly diminishing as a result of large public health campaigns targeting at risk populations in Africa and the Americas. Existing and newly-developed treatment strategies offer the chance to eliminate onchocercal ocular morbidity in some parts of the world. This article reviews these treatment strategies, current clinical and epidemiologic aspects of onchocerciasis, and the next steps toward elimination.

The effect of locally delivered doxycycline as an adjunctive therapy to scaling and root planing in smokers

BACKGROUND

Locally delivered doxycycline is found to be effective in managing periodontitis as an adjunct to scaling and root planing.

AIM

To evaluate the effect of locally delivered doxycycline (10%) with scaling and root planing in the periodontal treatment of smokers and to compare it with scaling and root planing alone.

METHODS

Twelve smokers with chronic periodontitis and a pocket depth (⩾5 mm) on posterior teeth that bleed on probing were selected. Patients were randomly assigned to scaling and root planing (SRP) or scaling and root planing followed by local application of doxycycline (SRP-D). Plaque, bleeding on probing, gingival recession, clinical attachment level (CAL), and probing depth (PD) were recorded at the baseline, 6 and 12 weeks.

RESULTS

Both groups showed a significant reduction in Plaque, Bleeding on Probing and pocket depth at 6th and 12th week from the baseline. A statistically significant gain of attachment was observed in both groups after treatment. Even though the doxycycline group showed slightly higher attachment gain it was not statistically significant compared to the control group.

CONCLUSION

The observations of the study reveal that the additional benefit of topical application of doxycycline as an adjunct to scaling and root planing in smokers is not convincing. However, further clinical studies may be necessary to substantiate the present observations.

Evaluation of the Doxycycline Release from AH26 Sealer-Doxycycline Combination: An ex vivo Study

INTRODUCTION

The purpose of this ex vivo study was to determine the releasing characteristics and doxycycline dentinal diffusion of AH26 sealer-doxycycline combination from apical 3mm of tooth root and apical foramen.

MATERIALS AND METHODS

One-hundred and two recently extracted single-rooted human teeth were decoronated and prepared with #3 and #4 Gates-Glidden drills and rotary Mtwo files. Smear layer was removed; all surfaces except for apical 3mm of each root were sealed with two coats of nail polish. To quantify the release and diffusion of the doxycycline at different time intervals (30 min, 48 and 72 h) after root canal obturation, the samples were randomly divided into three groups (n=30; 0.5 h, 48 h, 72 h). To evaluate the release of doxycycline from AH26 sealer-doxycycline combination at six concentrations of antibiotic including 0.5%, 1%, 2%, 5%, 10% and 20%; each experimental group was divided into six equal subgroups (n=5). Root canals were filled with gutta-percha and AH26-doxycycline combinations and then were placed in vials containing 1.25mL of phosphate buffer saline solution (PBS). After 30 min, 48 and 72 h, the amount of doxycycline released from specimens into PBS were determined by measuring the absorbance values using UV spectrophotometry at λ(max)=350 nm. Data were analyzed using two-way ANOVA.

RESULTS

The findings of this study revealed that AH26 sealer-doxycycline combination released variable measures of antibiotic at each time interval and in the various concentrations. At 30 min, no statistically significant differences were obtained between the results of subgroups, but at 48 and 72 h these differences were significant (P<0.001). The results also showed that differences between 0.5 h, 48 h and 72 h were significant within subgroups (P<0.01).

CONCLUSION

Under the conditions of this ex vivo study, doxycycline can be released from AH26 sealer-antibiotic combination through 3mm of apical root and apical foramen at 30 min, 48 and 72 h after mixing the sealer with doxycycline at concentrations of 0.5% up to 20%.

Transcatheter arterial embolization with doxycycline and lipiodol down-regulates VEGF and MMP-2 expression in implanted hepatic VX2 tumors in rabbits

AIM: To investigate the effect of transcatheter arterial embolization with doxycycline and lipiodol on tumor growth and the expression of vascular endothelial growth factor (VEGF) and matrix metalloproteinases-2 (MMP-2) in hepatic tumors.

METHODS: VX2 carcinoma was implanted in the left lobe of the liver of rabbits. Two weeks later, 32 tumor-bearing rabbits were randomly and equally divided into four groups: normal saline group, lipiodol group, adriamycin plus lipiodol group, and doxycycline plus lipiodol group. Tumor size was measured by CT to calculate tumor growth rate. Tumor necrosis rate was assessed pathologically. The expression levels of VEGF and MMP-2 in tumors were examined by immunohistochemistry. The staining intensity of VEGF and MMP-2 was evaluated with a computer-assisted image analyzer.

RESULTS: One week after treatment, the growth of tumors was significantly suppressed in the lipiodol group, adriamycin plus lipiodol group, and doxycycline plus lipiodol group compared with the normal saline group (136.4% ± 42.8%, 125.8% ± 30.8%, 116.7% ± 25.2% vs 325.3% ± 75.0%, all P < 0.05). Tumor necrosis rate was significantly higher in the doxycycline plus lipiodol group than in the lipiodol group and adriamycin plus lipiodol group (84.5% ± 5.2% vs 67.3% ± 8.5%, 71.4% ± 7.6%, both P < 0.05). The expression of VEGF was significantly up-regulated in the lipiodol group and adriamycin plus lipiodol group compared with the normal saline group (0.164 ± 0.021, 0.162 ± 0.021 vs 0.141 ± 0.018, both P < 0.05). MMP-2 was slightly up-regulated in the lipiodol group and adriamycin plus lipiodol group compared with the normal saline group (both P > 0.05). The expression levels of VEGF and MMP-2 were significantly lower in the doxycycline plus lipiodol group than in the normal saline group (0.121 ± 0.019 vs 0.141 ± 0.018; 0.135 ± 0.027 vs 0.158 ± 0.016, both P < 0.05). There is a positive correlation between the expression of MMP-2 and VEGF.

CONCLUSION: Trancatheter arterial embolization with doxycycline and lipiodol can suppress tumor growth, increase tumor necrosis, and decrease VEGF and MMP-2 expression in implanted hepatic VX2 tumors in rabbits.

Comparison of AH26 Physicochemical Properties with Two AH26/Antibiotic Combinations

INTRODUCTION

The purpose of this study was to compare the setting time and post-setting solubility, flow, film thickness and dimensional changes of AH26 root canal sealer with AH26-Antibiotic combination.

MATERIALS AND METHODS

This study was performed according to British standard BS 6876 (2001) which tests the physicochemical properties of endodontic sealers. Three samples of each of tested materials including AH26 alone, AH26/amoxicillin and AH26/doxycycline were used to test each of the properties. They were prepared according to ISO protocols.

RESULTS

The setting time of studied materials was 46 hours for AH26, 29 hours for AH26/amoxicillin, 49 hours for AH26/doxycycline. Flow test results were as follows, for AH 26, 15.6 mm; AH26/amoxicillin, 14.9 mm; AH26/doxycycline, 14.2 mm. Film thickness was 0.024 mm in AH26, 0.0283 mm in AH26/amoxicillin, 0.0276 mm AH26/doxycycline. The solubility of AH26 was 0.0076%, AH26/amoxicillin, 0.0113%, and for AH26/doxycycline, 0.013 %. Dimensional changes following setting was 0.07 mm, 2.6 mm, and 1.1 mm for AH 26, AH26/amoxicillin, and AH26/doxycycline, respectively.

CONCLUSION

The physico-mechanical properties of AH26 antibiotic combinations were superior compared with AH26, with the exception of flow. Also, AH26/amoxicillin had a lower setting time than AH26. However, all values were within an acceptable range which conformed to ISO.

In vitro scanning electron microscopic study on the effect of doxycycline and vancomycin on enterococcal induced biofilm

INTRODUCTION

Enterococcus (E) faecalis bacteria adhere to dentine of teeth root canals to form the biofilm. E. faecalis has been shown to be resistant to antibiotics. This in vitro study aimed to investigate the efficacy of vancomycin and doxycycline in inhibiting E. faecalis biofilm formation.

MATERIALS AND METHODS

A total of 60 extracted human teeth were incubated with E. faecalis (ATCC 35550 strain) for 45 days to allow biofilm formation. The teeth were equally divided into six groups (n=10): 1) positive control, 2) negative control, 3) doxycycline alone 4) doxycycline with filing, 5) vancomycin alone, 6) vancomycin with filing. The relevant canals were irrigated with 4µg/mL of either vancomycin or doxycycline antibiotic. Teeth were processed for scanning electron microscopy (SEM). Areas of biofilm remaining in the canals after antibiotic treatment were measured with Scion image analysis software using the SEM images.

RESULTS

Vancomycin is more effective in reducing the overall biofilm area compared with doxycycline; moreover filing after antibiotic administration increased this effect.

CONCLUSION

We can conclude that vancomycin had greater efficacy than doxycycline for inhibiting and reducing E. faecalis biofilms growth in root canals. However, it failed to completely eliminate biofilm formation.

In-vitro red blood cell partitioning of doxycycline

OBJECTIVE

In-vitro red blood cell (RBC) partitioning of doxycycline was studied to determine whether doxycycline penetrates RBC and its concentration was assayed keeping in view its high lipophilicity.

MATERIALS AND METHODS

Standardization of doxycycline was performed in whole blood and plasma of cattle by microbiological assay using Bacillus subtillis ATCC 6633 as indicator organizm. Actual concentration of the drug was obtained by comparing zone inhibition with standard graph and the extent of partitioning was mathematically calculated.

RESULTS

The R(2) value of standard graph for doxycycline was 0.9934 and 0.9727 for plasma and whole blood, respectively. Overall, RBC partitioning of doxycycline was found to be 18.40 +/- 1.70%.

CONCLUSIONS

Overall RBC partitioning of doxycycline indicated low penetration into RBC. Plasma is the fluid suggested for pharmacokinetic evaluation of doxycycline.

Developing tTA transgenic rats for inducible and reversible gene expression

To develop transgenic lines for conditional expression of desired genes in rats, we generated several lines of the transgenic rats carrying the tetracycline-controlled transactivator (tTA) gene. Using a vigorous, ubiquitous promoter to drive the tTA transgene, we obtained widespread expression of tTA in various tissues. Expression of tTA was sufficient to strongly activate its reporter gene, but was below the toxicity threshold. We examined the dynamics of Doxycycline (Dox)-regulated gene expression in transgenic rats. In the two transmittable lines, tTA-mediated activation of the reporter gene was fully subject to regulation by Dox. Dox dose-dependently suppressed tTA-activated gene expression. The washout time for the effects of Dox was dose-dependent. We tested a complex regime of Dox administration to determine the optimal effectiveness and washout duration. Dox was administered at a high dose (500 μg/ml in drinking water) for two days to reach the effective concentration, and then was given at a low dose (20 μg/ml) to maintain effectiveness. This regimen of Dox administration can achieve a quick switch between ON and OFF statuses of tTA-activated gene expression. In addition, administration of Dox to pregnant rats fully suppressed postnatal tTA-activated gene expression in their offspring. Sufficient levels of Dox are present in mother's milk to produce maximal efficacy in nursing neonates. Administration of Dox to pregnant or nursing rats can provide a continual suppression of tTA-dependent gene expression during embryonic and postnatal development. The tTA transgenic rat allows for inducible and reversible gene expression in the rat; this important tool will be valuable in the development of genetic rat models of human diseases.

Antimicrobial Effects of AH26 Sealer/Antibiotic Combinations Against Enterococcus Faecalis

INTRODUCTION

The purpose of this in vitro study was to evaluate the antimicrobial effects of two antibiotics added to AH26 sealer against Enterococcus faecalis (EF).

MATERIALS AND METHODS

The antimicrobial effects of two antibiotic (amoxicillin and doxycycline) that were added separately to AH26 sealer was evaluated by using the agar diffusion test and in vitro human root inoculation method. The freshly mixed sealers were placed in prepared wells inside agar plates inoculated with EF, and were incubated at 37(°)C. The zones of inhibition were measured at 24, 48, 72 hours and 7 days. Root specimens were prepared and obturated with lateral condensation technique. Samples were collected from infected root canals after 2 and 7 days of incubation and the number of colony-forming units (CFU) was determined. The data were analyzed using one-way and two-way ANOVA.

RESULTS

The findings of this study revealed that sealer-antibiotic combination containing amoxicillin and doxycycline had a significant difference in the mean zones of inhibition when compared to AH26 sealer alone in all of the time periods (P<0.05). The minimum effective concentration against EF was one percent of sealer powder weight for both of amoxicillin and doxycyline. The mean log10 CFU in AH26-doxycyline combination group was significantly lower than other groups at 48 h incubation period (P<0.05). AH26-doxycycline combination group and AH26-Amoxicillin combination group killed bacteria (mean CFU=0) in the dentinal tubules at 7 days incubation period.

CONCLUSION

In vitro root fillings carried out with gutta-percha and AH26-antibiotic combination were effective in killing EF in dentinal tubules.

Third-line rescue therapy for Helicobacter pylori infection

H pylori gastric infection is one of the most prevalent infectious diseases worldwide. The discovery that most upper gastrointestinal diseases are related to H pylori infection and therefore can be treated with antibiotics is an important medical advance. Currently, a first-line triple therapy based on proton pump inhibitor (PPI) or ranitidine bismuth citrate (RBC) plus two antibiotics (clarithromycin and amo-xicillin or nitroimidazole) is recommended by all consensus conferences and guidelines. Even with the correct use of this drug combination, infection can not be eradicated in up to 23% of patients. Therefore, several second line therapies have been recommended. A 7 d quadruple therapy based on PPI, bismuth, tetracycline and metronidazole is the more frequently accepted. However, with second-line therapy, bacterial eradication may fail in up to 40% of cases. When H pylori eradication is strictly indicated the choice of further treatment is controversial. Currently, a standard third-line therapy is lacking and various protocols have been proposed. Even after two consecutive failures, the most recent literature data have demonstrated that H pylori eradication can be achieved in almost all patients, even when antibiotic susceptibility is not tested. Different possibilities of empirical treatment exist and the available third-line strategies are herein reviewed.

Etiological role of brucellosis in autoimmune hepatitis

To show that brucellosis may trigger autoimmune hepatitis (AIH), in addition to nonspecific liver involvement and toxic hepatitis, due to a class effect of tetracycline family used for treatment. We present a female patient admitted to our hospital due to partially improved fatigue and elevated liver enzymes following doxycycline and streptomycin usage for brucellosis. Brucellosis is endemic in our country, Turkey. It may involve any organ in the body. Liver is frequently involved. Doxycycline used for treatment occasionally may lead to hepatotoxicity. AIH is a necroinflammatory disease of the liver. Certain drugs (e.g., minocycline), toxins, and viruses (hepatitis B, hepatitis C, EBV, etc.) can trigger AIH. Only one case of AIH probably caused by doxycycline and brucellosis was reported. We discuss the relationship between brucellosis, AIH, and hepatotoxicity of doxycycline. Brucellosis may trigger AIH.