Quantitative Analysis and Correction of Temperature Effects on Fluorescent Tracer Concentration Measurement

To ensure an accurate evaluation of pesticide spray application efficiency and pesticide mixture uniformity, reliable and accurate measurements of fluorescence concentrations in spray solutions are critical. The objectives of this research were to examine the effects of solution temperature on measured concentrations of fluorescent tracers as the simulated pesticides and to develop models to correct the deviation of measurements caused by temperature variations. Fluorescent tracers (Brilliant Sulfaflavine (BSF), Eosin, Fluorescein sodium salt) were selected for tests with the solution temperatures ranging from 10.0 °C to 45.0 °C. The results showed that the measured concentrations of BSF decreased as the solution temperature increased, and the decrement rate was high at the beginning and then slowed down and tended to become constant. In contrast, the concentrations of Eosin decreased slowly at the beginning and then noticeably increased as temperatures increased. On the other hand, the concentrations of Fluorescein sodium salt had little variations with its solution temperature. To ensure the measurement accuracy, correction models were developed using the response surface methodology to numerically correct the measured concentration errors due to variations with the solution temperature. Corrected concentrations using the models agreed well with the actual concentrations, and the overall relative errors were reduced from 42.36% to 2.91% for BSF, 11.72% to 1.55% for Eosin, and 2.68% to 1.17% for Fluorescein sodium salt. Thus, this approach can be used to improve pesticide sprayer performances by accurately quantifying droplet deposits on target crops and off-target areas.

Delivery of Niacinamide to the Skin Using Microneedle-Like Particles

The stratum corneum is the outermost skin layer that obstructs the delivery of active ingredients found in cosmeceutical products. Chemical peels and microbeads have been used to overcome this layer, but these methods can cause side effects and are not environmentally friendly. While microneedles do not share the dangers mentioned above, they are currently only available as patches, which makes them unsuitable to be used with products that are usually applied onto a large area of the skin surface. Therefore, the aim of this study was to develop microneedle-like particles (MLP) whose needles would disrupt the skin during the rubbing process. A modified approach taken from conventional micromolding techniques was used to make the MLPs. The experimental results show that the fabricated structures had the required mechanical strength. Furthermore, after the application of the MLPs, the permeability of two fluorescent dyes, fluorescein sodium salt and sulforhodamine B increased to 217.6% ± 25.6% and 251.7% ± 12.8% respectively. Additionally, the permeability of a model drug, niacinamide, was shown to have increased to 193.8% ± 29.9%. Cryosectioned porcine slices also confirmed the ability of MLPs to enhance skin permeability by revealing a deeper penetration of the applied fluorescent dye. Altogether, the results demonstrate the potential of MLPs to be used as safe skin permeability enhancers that can be applied all over the skin.