In Vitro Evaluation of Rose Bengal Photoactivated by Custom-Built Green Light-Emitting Diode Source for Bacteria and Rapidly Growing Mycobacteria Inhibition.

Purpose: In vitro evaluation of rose bengal (RB) photoactivated by our custom-built green light-emitting diode (LED) source for the growth inhibition of bacterial strains and rapidly growing mycobacterial (RGM) isolates in infectious keratitis. Methods: Six corneal clinical bacteria isolates were included in this study: two Gram-positive bacteria (methicillin-resistant Staphylococcus aureus [MRSA] and Staphylococcus epidermidis), two Gram-negative bacteria (Pseudomonas aeruginosa and Serratia marcescens), and two RGM (Mycobacterium chelonae and Mycobacterium abscessus). Microorganisms were cultured and incubated at specific conditions and prepared in suspensions to adjust their concentration to 104 cells/mL. Different treatments were conducted in triplicates: Group I, no treatment; Group II, treated with 0.1% rose bengal alone (exposed to dark for 30 minutes); Group III, exposed to custom green LED for 30 minutes (12.87 J/cm2); and Group IV, treated with 0.1% rose bengal and exposed to custom green LED for 30 minutes. Agar plates were incubated at specific conditions and photographed after growth for pixel analyses. Results: Complete growth inhibition of all bacteria and RGM was observed in Group IV. MRSA and S. epidermidis in Group II also showed complete growth inhibition. Conclusions: The custom-built green LED presented good activity by photoactivating RB and inhibiting micro-organism growth. For the first time, we demonstrated the expressive growth inhibition effect of RB against S. epidermidis, RGM, and S. marcescens. Clinical treatment with RB may offer an alternate adjunct therapy for corneal surface infections. Translational Relevance: Validating in vitro the custom-built green LED encourages the clinical application for the treatment of infectious keratitis.

Sodium distribution in mixed alkali K-Na metaphosphate glasses.

The local order and distribution of Na in the mixed alkali metaphosphate glasses K(x)Na(1-x)PO(3) were analyzed, with the aim to identify segregation or a random mixture of both cation species. X-Ray photoelectron spectroscopy and several nuclear magnetic resonance (NMR) techniques were applied, including (31)P and (23)Na high-resolution spectroscopy, (23)Na triple quantum-MAS NMR, rotational echo double resonance between (31)P and (23)Na, and (23)Na NMR spin echo decay. The structural picture emerging from these results reveals the similarity in the local Na environments in the glasses but also subtle structural adjustments with increasing degree of K replacement. While both cations are intimately mixed at the atomic scale, the (23)Na spin echo decay data suggest a detectable like-cation preference in the spatial distribution of the ions. These structural properties are consistent with those determined in Li-Rb metaphosphates, indicating that the origin of the mixed alkali effect observed in the conductivity of Na-K metaphosphate glasses may also be explained by structurally blocked ion diffusion.