Diosmin is a flavonoid with a great variety of biological activities including antioxidant and anti-inflammatory ones. Its cytoprotective effect in retinal pigment epithelium cells under high glucose conditions makes it a potential support in the treatment of diabetic retinopathy. Despite its benefits, poor solubility in water reduces its potential for therapeutic use, making it the biggest biopharmaceutical challenge. The design of diosmin-loaded nanocarriers for topical ophthalmic application represents a novelty that has not been yet explored. For this purpose, the response surface methodology (RSM) was used to optimize nanostructured lipid carriers (NLCs), compatible for ocular administration, to encapsulate diosmin and improve its physicochemical issues. NLCs were prepared by a simple and scalable technique: a melt emulsification method followed by ultrasonication. The experimental design was composed of four independent variables (solid lipid concentration, liquid lipid concentration, surfactant concentration and type of solid lipid). The effect of the factors was assessed on NLC size and PDI (responses) by analysis of variance (ANOVA). The optimized formulation was selected according to the desirability function (0.993). Diosmin at two different concentrations (80 and 160 µM) was encapsulated into NLCs. Drug-loaded nanocarriers (D-NLCs) were subjected to a physicochemical and technological investigation revealing a mean particle size of 83.58 ± 0.77 nm and 82.21 ± 1.12 nm, respectively for the D-NLC formulation prepared with diosmin at the concentration of 80 µM or 160 µM, and a net negative surface charge (−18.5 ± 0.60 and −18.0 ± 1.18, respectively for the two batches). The formulations were analyzed in terms of pH (6.5), viscosity, and adjusted for osmolarity, making them more compatible with the ocular environment. Subsequently, stability studies were carried out to assess D-NLC behavior under different storage conditions up to 60 days, indicating a good stability of NLC samples at room temperature. In-vitro studies on ARPE-19 cells confirmed the cytocompatibility of NLCs with retinal epithelium. The effect of D-NLCs was also evaluated in-vitro on a model of retinal inflammation, demonstrating the cytoprotective effect of D-NLCs at various concentrations. RSM was found to be a reliable model to optimize NLCs for diosmin encapsulation.

Resveratrol (RSV) is well known for its many beneficial activities, but its unfavorable physicochemical properties impair its effectiveness after systemic and topical administration; thus, several strategies have been investigated to improve RSV efficacy. With this aim, in this work, we synthesized a novel RSV triester with trolox, an analogue of vitamin E with strong antioxidant activity. The new RSV derivative (RSVTR) was assayed in vitro to evaluate its antioxidant and anti-glycation activity compared to RSV. RSVTR chemical stability was assessed at pH 2.0, 6.8, and 7.2 and different storage temperatures (5 °C, 22 °C, and 37 °C). An influence of pH stronger than that of temperature on RSVTR half-life values was pointed out, and RSVTR greatest stability was observed at pH 7.2 and 5 °C. RSVTR showed a lower antioxidant ability compared to RSV (determined by the oxygen radical absorbance capacity assay) while its anti-glycation activity (evaluated using the Maillard reaction) was significantly greater than that of RSV. The improved ability to inhibit the glycation process was attributed to a better interaction of RSVTR with albumin owing to its increased topological polar surface area value and H-bond acceptor number compared to RSV. Therefore, RSVTR could be regarded as a promising anti-glycation agent worthy of further investigations.

Our study was aimed to asses the retinal binding of a new synthetic Brilliant Blue G derivative (PBB) ophthalmic formulation to improve vitreoretinal surgery procedure. Protein affinity of the new molecule was evaluated in vitro (cell-free assay) and in silico. Further, an ex vivo model of vitreoretinal surgery was developed by using porcine eyes to assess the pharmacological profile of PBB compared to commercial formulations based on Brilliant Blue G (BBG) and methyl-BBG (Me-BBG). PBB showed a higher affinity for proteins (p<0.05) compared to BBG and Me-BBG. In vitro and in silico studies demonstrated that the high selectivity of PBB could be related to the high lipophilicity and binding to fibronectin, the main component of the retinal internal limiting membrane (ILM). Furthermore, PBB staining capabilities were evaluated in porcine eyes in comparison with BBG and Me-BBG. Forty microliters of each formulation were slowly placed over the retinal surface and removed after 30 seconds. After that ILM peeling was carried out, and the retina collected. BBG, Me-BBG and PBB quantification in ILM and retina tissues was carried out by HPLC analysis. PBB levels in the ILM were significantly (p<0.05) higher compared to BBG and Me-BBG formulations. On the contrary, PBB showed a significant lower (p<0.05) distribution in retina (52 ng/mg tissue) compared to BBG and Me-BBG, in particular PBB levels were significantly (p<0.05) lower. Therefore, the new synthetic Brilliant Blue derivative (PBB) showed a great ILM selectivity in comparison with underneath retinal layers. In conclusion, these findings had high translational impact with a tangible improving of retinal surgery, suggesting a future use during surgical practice.

A highly sensitive and selective method for the determination of valproic acid salts in pharmaceutical tablet formulations by a high performance liquid chromatography method with coulometric electrochemical detection is described. The precolumn derivatizations of valproic acid and the internal standard (n-hexanoic acid) were carried out using 1-(2,5-dihydroxyphenyl)-2-bromoethanone as an electroactive labeling reagent. The resulting electroactive esters were separated by isocratic elution of a 3 μm Adsorbosphere ODS column with methanolacetonitrile-acetate buffer eluent. The compounds were detected by a porous graphite electrode set at an oxidation potential of + 0.45 V. The analytical method developed in this study is suitable for quality control assays of complex pharmaceutical formulations containing valproic acid or its salts.