Solvent-free biodegradable scleral plugs providing sustained release of vancomycin, amikacin, and dexamethasone--an in vivo study

Microneedle-mediated intrascleral delivery of in situ forming thermoresponsive implants for sustained ocular drug delivery

OBJECTIVES

This paper describes use of minimally invasive hollow microneedle (HMN) to deliver in situ forming thermoresponsive poloxamer-based implants into the scleral tissue to provide sustained drug delivery.

METHODS

In situ forming poloxamer formulations were prepared and investigated for their rheological properties. HMN devices 400, 500 and 600 μm in height were fabricated from hypodermic needles (i.e. 27, 29 and 30 G) and tested for depth of penetration into rabbit sclera. Maximum force and work required to expel different volumes of poloxamer formulations was also investigated. Release of fluorescein sodium (FS) from intrasclerally injected implants was also investigated. Optical coherence tomography (OCT) was used to examine implant localisation and scleral pore-closure.

KEY FINDINGS

Poloxamer formulations showed Newtonian behaviour at 20°C and pseudoplastic (shear-thinning) behaviour at 37°C. Maximum force and work required to expel different volumes of poloxamer formulations with different needles ranged from 0.158 to 2.021 N and 0.173 to 6.000 N, respectively. OCT showed intrascleral localisation of implants and scleral pore-closure occurred within 2-3 h. Sustain release of FS was noticed over 24 h and varied with depth of implant delivery.

CONCLUSIONS

This study shows that the minimally invasive HMN device can localise in situ forming implants in the scleral tissue and provide sustained drug delivery.

Bacterial endophthalmitis in the age of outpatient intravitreal therapies and cataract surgeries: host-microbe interactions in intraocular infection

Bacterial endophthalmitis is a sight threatening infection of the interior structures of the eye. Incidence in the US has increased in recent years, which appears to be related to procedures being performed on an aging population. The advent of outpatient intravitreal therapy for management of age-related macular degeneration raises yet additional risks. Compounding the problem is the continuing progression of antibiotic resistance. Visual prognosis for endophthalmitis depends on the virulence of the causative organism, the severity of intraocular inflammation, and the timeliness of effective therapy. We review the current understanding of the pathogenesis of bacterial endophthalmitis, highlighting opportunities for the development of improved therapeutics and preventive strategies.

Antiinflammatory effect of low-level laser therapy on Staphylococcus epidermidis endophthalmitis in rabbits

A rabbit model of endophthalmitis was established to evaluate the antiinflammatory effect of low-level laser therapy (LLLT) as an adjunct to treatment for Staphylococcus epidermidis endophthalmitis. Rabbits were randomly divided into three groups to receive intravitreal injections into their left eye: group A received 0.5 mg vancomycin (100 μl), group B received 0.5 mg vancomycin + 0.2 mg dexamethasone (100 μl), and group C received 0.5 mg vancomycin (100 μl) and continuous wave semiconductor laser irradiation (10 mW, λ = 632 nm) focused on the pupil. Slit lamp examination and B-mode ultrasonography were conducted to evaluate the symptoms of endophthalmitis. Polymorphonuclear cells and tumour necrosis factor alpha (TNF-α) in aqueous fluid were measured at 0 h, and 1, 2, 3, 7 and 15 days. A histology test was conducted at 15 days. B-mode ultrasonography and histology revealed that groups B and C had less inflammation than group A at 15 days. Groups B and C had fewer polymorphonuclear cells and lower levels of TNF-α in aqueous fluid than group A at 2, 3 and 7 days (P < 0.05). There was no significant difference between groups B and C (P > 0.05). There was no significant difference between groups A, B and C at 15 days (P > 0.05). As an adjunct to vancomycin therapy to treat S. epidermidis endophthalmitis, LLLT has an antiinflammatory effect similar to that of dexamethasone.