A new class of pluripotent stem cell cytotoxic small molecules

10.1371/journal.pone.0085039PLoS ONE93-POLN

In vitro and in vivo evaluation of graphene/titanium dioxide composites for synthetic Keratoprosthesis skirts

The design of an artificial cornea skirt requires consideration of its mechanical strength, corrosion resistance as well as biocompatibility in the ocular environment. Herein we report the first study on graphene/titania (TiO2) ceramics for this application. We used graphene oxide (GO, 100–400 nm) and large crystal graphene oxide (LCGO, 20–40 μm) as graphene precursors, and the composites were prepared by an advanced sintering technique, spark plasma sintering. Their mechanical properties were investigated, and corrosion resistance was studied in artificial tear fluid through anodic polarization and long-term incubation. In vitro safety and biocompatibility was assessed using primary human corneal stromal fibroblast culture, and the implantation of fabricated TiO2/GO or TiO2/LCGO composite on rabbit cornea model was performed and in vivo stability and corneal tissue responses were evaluated. Our results showed that that TiO2/LCGO mixed at 1% wt/wt was a preferable graphene precursor which resulted in mechanically stronger and chemically stable compound when compared to other mixture percentages and TiO2/GO(1%). Furthermore, we demonstrated that graphene/TiO2 hybrid possessed outstanding biocompatibility with corneal stromal fibroblasts and induced stronger tissue adherence when transplanted into rabbit stroma. This suggested that graphene/TiO2 hybrid could be a highly promising candidate material to use in keratoprosthesis skirt, a major component of artificial keratoprosthesis for the treatment of end-stage corneal blindness worldwide.​Master of Science (Biomedical Engineering

Prophylactic Vancomycin Drops Reduce the Severity of Early Bacterial Keratitis in Keratoprosthesis

Artificial cornea transplantation, keratoprosthesis, improves vision for patients at high risk of failure with human cadaveric cornea. However, post-operative infection can cause visual loss and implant extrusion in 3.2–17% of eyes. Long-term vancomycin drops are recommended following keratoprosthesis to prevent bacterial keratitis. Evidence, though, in support of this practice is poor. We investigated whether prophylactic vancomycin drops prevented bacterial keratitis in an animal keratoprosthesis model. inoculation into the cornea at 7–12 days post-implantation and were sacrificed at predetermined time-points. Prophylactic and non-prophylactic groups were compared with slit-lamp photography (SLP), anterior segment optical coherence tomography (AS-OCT), and histology, immunohistochemistry and bacterial quantification of excised corneas. Corneal vancomycin pharmacokinetics were studied in 8 additional rabbits. only after 16 days of vancomycin drops. Two of 3 rabbits still developed infection despite bacterial inoculation after 16 days of prophylactic drops. keratitis. Patients should continue to be counselled regarding the risk of infection following keratoprosthesis

Prophylactic Vancomycin Drops Reduce the Severity of Early Bacterial Keratitis in Keratoprosthesis

Background: Artificial cornea transplantation, keratoprosthesis, improves vision for patients at high risk of failure with human cadaveric cornea. However, post-operative infection can cause visual loss and implant extrusion in 3.2–17% of eyes. Long-term vancomycin drops are recommended following keratoprosthesis to prevent bacterial keratitis. Evidence, though, in support of this practice is poor. We investigated whether prophylactic vancomycin drops prevented bacterial keratitis in an animal keratoprosthesis model. Methodology: Twenty-three rabbits were assigned either to a prophylactic group (n = 13) that received vancomycin 1.4% drops 5 times/day from keratoprosthesis implantation to sacrifice, or a non-prophylactic group (n = 10) that received no drops. All rabbits had Staphylococcus aureus inoculation into the cornea at 7–12 days post-implantation and were sacrificed at predetermined time-points. Prophylactic and non-prophylactic groups were compared with slit-lamp photography (SLP), anterior segment optical coherence tomography (AS-OCT), and histology, immunohistochemistry and bacterial quantification of excised corneas. Corneal vancomycin pharmacokinetics were studied in 8 additional rabbits. Results: On day 1 post-inoculation, the median SLP score and mean±SEM AS-OCT corneal thickness (CT) were greater in the non-prophylactic than the prophylactic group (11 vs. 1, p = 0.049 and 486.9±61.2 vs. 327.4±37.1 μm, p = 0.029 respectively). On days 2 and 4, SLP scores and CT were not significantly different. Immunohistochemistry showed a greater CD11b+ve/non-CD11b+ve cell ratio in the non-prophylactic group (1.45 vs. 0.71) on day 2. Bacterial counts were not significantly different between the two groups. Corneal vancomycin concentration (2.835±0.383 μg/ml) exceeded minimum inhibitory concentration (MIC) for Staphylococcus aureus only after 16 days of vancomycin drops. Two of 3 rabbits still developed infection despite bacterial inoculation after 16 days of prophylactic drops. Conclusions: Prophylactic vancomycin drops provided short-term benefit, but did not prevent infection. Achieving MIC in the cornea was not sufficient to prevent Staphylococcus aureus keratitis. Patients should continue to be counselled regarding the risk of infection following keratoprosthesis.NRF (Natl Research Foundation, S’pore)Published versio

Histology.

<p>Haematoxylin and eosin stained corneal sections, comparing vancomycin prophylaxis to non-prophylaxis cases. A. Healthy cornea. B (day 2, prophylaxis). A rich infiltration of neutrophils is present throughout the stroma. The epithelial and endothelial surfaces are irregular due to stromal oedema. C (day 2, non-prophylaxis). The stroma appears more oedematous than in image B. A rich neutrophilic infiltration is also present, mostly in the pocket, but the neutrophils appear to be less densely arranged in the stroma than in image B, most likely reflecting the presence of more oedema. D (day 4, prophylaxis). The stroma is more oedematous than in image B and the Descemets membrane is detached, reflecting greater levels of infection. The neutrophilic infiltration is not as dense as in image B, most likely due to more stromal oedema. E (day 4, non-prophylaxis). The stroma appears similarly oedematous to that in image D and slightly richer in neutrophilic infiltration. (Scale bar 100μm)</p

Study design.

<p>The flow chart demonstrates allocation to prophylactic and non-prophylactic groups, follow-up and investigations carried out at each time point. (* MIC: minimum inhibitory concentration, ** SLP: slit-lamp photography, AS-OCT: anterior segment optical coherence tomography)</p

Immunohistochemistry.

<p>Comparison between prophylaxis and non-prophylaxis on day 2 following bacterial inoculation. More CD11b +ve neutrophils (fluorescing green) are present in the non-prophylactic case (A) than the prophylactic case (B). (Scale bar 50μm).</p

Serial slit-lamp photography for clinical grading.

<p>A. A quiet eye with a clear cornea and the titanium keratoprosthesis in-situ before bacterial inoculation. B. On day 1 following inoculation, the conjunctiva is injected and the cornea oedematous with early infiltration. C. On day 2, moderate corneal infiltration has developed. D. On day 4, severe corneal infiltration is present.</p

Slit-lamp photography score comparison between prophylactic and non-prophylactic groups.

<p>Slit-lamp photography score comparison between prophylactic and non-prophylactic groups.</p

Anterior Segment Optical Coherence Tomography.

<p>Corneal thickness between implant and anterior corneal surface was measured at 5 locations before (A) and after (B) bacterial inoculation.</p